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RE: [microhydro] Grid-tie inverter microhydro system

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  • Jeff Grebe
    Hi Kevin. The only clue you give to size of the plant is the 10 kW inverter - is the turbine output? The AC-DC-AC conversion process you mention can and is
    Message 1 of 13 , Jun 12, 2013
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      Hi Kevin.   The only clue you give to size of the plant is the 10 kW inverter - is the turbine output?  The AC-DC-AC conversion process you mention can and is being done.  Works very well for variable speed turbines  and what we were using on our hydro kinetic turbines. 
       
      Having said that you almost answered your own question.  What you need is a UL 1741 inverter so that gives you a simple option. First use an AC alternator then a bridge rectifier to produce DC power then a solar  or wind inverter (most grid tie inverters take a range of input voltages not only 48 V so be sure to find one that has the correct input range.  Wind inverters are generally more flexible concerning input power but that depends on the manufacturer
       
      An alternative tact would be to go back to the utility with the  IEEE 1547 Utility Interconnect Standard.  There is no reason that you should have to spend that kind of money to provide the required safeties and protective relays for this size plant- the utility may be willing to work with you if you can show them the proper codes and UL approved equipment.


       
      Jeff  Grebe

       

      To: microhydro@yahoogroups.com
      From: kevindedwards@...
      Date: Wed, 12 Jun 2013 13:44:18 -0400
      Subject: [microhydro] Grid-tie inverter microhydro system



      All,

      I am working to develop a microhydro site that will be grid connected, in the United States.  At first I wanted to use a simple induction motor as generator, but the utility will require an excessive amount of protection equipment for this, costing over $40000.  This is the same equipment they would require for a 2 MW plant!  They were not interested in the utility grade protective relaying I proposed.

      They are also willing to allow a connection if we use a UL-1741 certified inverter, like would be used for grid-tie solar.

      The prime mover is a 24' diameter steel overshot wheel, so there will be gears/belts to increase the speed no matter what generator is chosen.  Normally we work on equipment from a few hundred kilowatts to a few megawatts, so this is outside my experience range.  My question for the group is: what is the best way to make 48VDC from the available shaft power?

      This is the first idea that came to me:
      Waterwheel -> speed increaser -> Brushless AC synchronous generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter

      Better would be a PMDC generator that directly output 48v (or 24v) DC.  Any ideas on sourcing this?

      Thanks!
      Kevin

      ---
      Kevin Edwards
      Mechanical Engineer
      Piedmont Hydro Technologies, LLC
      kevin.edwards@...
      336.589.6138
      www.piedmonthydrotech.com


    • nando37
      They are trying to snow you down . The only thing you need to demonstrate is that if you are using an induction motor as a generator without any capacitors if
      Message 2 of 13 , Jun 12, 2013
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        They are trying to snow you down .

        The only thing you need to demonstrate is that if you are using an induction motor as a generator without any capacitors if the Grid drops the induction generator drops as well because the Grid electrical power is the what makes the induction motor to produce power into the Grid.

        Instead with a Vac Inverter You need to have a high cost inverter with Grid drop protection -- totally unnecessary

        Nando



        On 6/12/2013 12:44, Kevin Edwards wrote:
         

        All,

        I am working to develop a microhydro site that will be grid connected, in the United States.  At first I wanted to use a simple induction motor as generator, but the utility will require an excessive amount of protection equipment for this, costing over $40000.  This is the same equipment they would require for a 2 MW plant!  They were not interested in the utility grade protective relaying I proposed.

        They are also willing to allow a connection if we use a UL-1741 certified inverter, like would be used for grid-tie solar.

        The prime mover is a 24' diameter steel overshot wheel, so there will be gears/belts to increase the speed no matter what generator is chosen.  Normally we work on equipment from a few hundred kilowatts to a few megawatts, so this is outside my experience range.  My question for the group is: what is the best way to make 48VDC from the available shaft power?

        This is the first idea that came to me:
        Waterwheel -> speed increaser -> Brushless AC synchronous generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter

        Better would be a PMDC generator that directly output 48v (or 24v) DC.  Any ideas on sourcing this?

        Thanks!

        Kevin

        ---
        Kevin Edwards
        Mechanical Engineer
        Piedmont Hydro Technologies, LLC
        kevin.edwards@...
        336.589.6138
        www.piedmonthydrotech.com

      • Jeff Grebe
        Nando, not to get into an argument but I disagree with the statement that all you need is an induction motor. This is theoretically true but not in practice.
        Message 3 of 13 , Jun 13, 2013
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          Nando, not to get into an argument but I disagree with the statement that all you need is an induction motor.  This is theoretically true but not in practice.  Every utility that I am aware of and IEEE 1547 have very specific interconnect requirement that require at the minimum protective relays.  Remember your are not just protecting against islanding but also from such things as over/under voltage over/under frequency etc. 
           
          My experience has been that when you get into small systems that a UL listed inverter that has those safeties built in and tested is actually  cheaper than a purchased protective relay package that requires field wiring and testing and greatly simplifies the negotiations with the utility. 


          Jeff  Grebe

           

          To: microhydro@yahoogroups.com
          From: nando37@...
          Date: Wed, 12 Jun 2013 21:56:11 -0500
          Subject: Re: [microhydro] Grid-tie inverter microhydro system



          They are trying to snow you down .

          The only thing you need to demonstrate is that if you are using an induction motor as a generator without any capacitors if the Grid drops the induction generator drops as well because the Grid electrical power is the what makes the induction motor to produce power into the Grid.

          Instead with a Vac Inverter You need to have a high cost inverter with Grid drop protection -- totally unnecessary

          Nando



          On 6/12/2013 12:44, Kevin Edwards wrote:
           
          All,

          I am working to develop a microhydro site that will be grid connected, in the United States.  At first I wanted to use a simple induction motor as generator, but the utility will require an excessive amount of protection equipment for this, costing over $40000.  This is the same equipment they would require for a 2 MW plant!  They were not interested in the utility grade protective relaying I proposed.

          They are also willing to allow a connection if we use a UL-1741 certified inverter, like would be used for grid-tie solar.

          The prime mover is a 24' diameter steel overshot wheel, so there will be gears/belts to increase the speed no matter what generator is chosen.  Normally we work on equipment from a few hundred kilowatts to a few megawatts, so this is outside my experience range.  My question for the group is: what is the best way to make 48VDC from the available shaft power?

          This is the first idea that came to me:
          Waterwheel -> speed increaser -> Brushless AC synchronous generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter

          Better would be a PMDC generator that directly output 48v (or 24v) DC.  Any ideas on sourcing this?

          Thanks!

          Kevin

          ---
          Kevin Edwards
          Mechanical Engineer
          Piedmont Hydro Technologies, LLC
          kevin.edwards@...
          336.589.6138
          www.piedmonthydrotech.com



        • nando37
          JEFF: Not getting into an argument but one needs to know how the induction motor works as a generator. The motor does not produce power UNLESS the GRID applies
          Message 4 of 13 , Jun 13, 2013
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            JEFF:

            Not getting into an argument but one needs to know how the induction motor works as a generator.

            The motor does not produce power UNLESS the GRID applies power to the motor  but the motor to convert into a generator the turbine attached to the motor HAS to make the motor rotate to the motor RPM RATE PLUS the Slip factor of the motor so if the motor is 1800 RPM rated, as a motor the RPM may be 1740 RPM and as a generator the RPM has to be set to 1800 Plus ( 1800 - 1740 ) = 1800 + 60 = 1860 RPM to start producing power into the GRID .

            Now if the GRID for some reason is disconnected the motor automatically stop producing power because it does not have the necessary polarization to produce power..

            Now  things like over /under voltage is defined by the Grid voltage -- also the frequency is totally defined by the GRID so there is not an over / under frequency -- because is defined by the Grid.

            So a simple relay set up to disconnect the motor leads from the GRID lines.  --- I could extend myself but I think that this is enough for the moment !! and the protective relay is really cheaper compared to the inverter and all the paraphernalia needed with the inverter.

            Nando
             

            On 6/13/2013 11:51, Jeff Grebe wrote:
             

            Nando, not to get into an argument but I disagree with the statement that all you need is an induction motor.  This is theoretically true but not in practice.  Every utility that I am aware of and IEEE 1547 have very specific interconnect requirement that require at the minimum protective relays.  Remember your are not just protecting against islanding but also from such things as over/under voltage over/under frequency etc. 
             
            My experience has been that when you get into small systems that a UL listed inverter that has those safeties built in and tested is actually  cheaper than a purchased protective relay package that requires field wiring and testing and greatly simplifies the negotiations with the utility. 


            Jeff  Grebe

             

            To: microhydro@yahoogroups.com
            From: nando37@...
            Date: Wed, 12 Jun 2013 21:56:11 -0500
            Subject: Re: [microhydro] Grid-tie inverter microhydro system



            They are trying to snow you down .

            The only thing you need to demonstrate is that if you are using an induction motor as a generator without any capacitors if the Grid drops the induction generator drops as well because the Grid electrical power is the what makes the induction motor to produce power into the Grid.

            Instead with a Vac Inverter You need to have a high cost inverter with Grid drop protection -- totally unnecessary

            Nando



            On 6/12/2013 12:44, Kevin Edwards wrote:
             
            All,

            I am working to develop a microhydro site that will be grid connected, in the United States.  At first I wanted to use a simple induction motor as generator, but the utility will require an excessive amount of protection equipment for this, costing over $40000.  This is the same equipment they would require for a 2 MW plant!  They were not interested in the utility grade protective relaying I proposed.

            They are also willing to allow a connection if we use a UL-1741 certified inverter, like would be used for grid-tie solar.

            The prime mover is a 24' diameter steel overshot wheel, so there will be gears/belts to increase the speed no matter what generator is chosen.  Normally we work on equipment from a few hundred kilowatts to a few megawatts, so this is outside my experience range.  My question for the group is: what is the best way to make 48VDC from the available shaft power?

            This is the first idea that came to me:
            Waterwheel -> speed increaser -> Brushless AC synchronous generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter

            Better would be a PMDC generator that directly output 48v (or 24v) DC.  Any ideas on sourcing this?

            Thanks!

            Kevin

            ---
            Kevin Edwards
            Mechanical Engineer
            Piedmont Hydro Technologies, LLC
            kevin.edwards@...
            336.589.6138
            www.piedmonthydrotech.com




          • Scott Moore
            I just installed a 3kW hydro grid tied system in the Idaho mountains 7 months ago. The local power utility required me to meet their interconnect standards.
            Message 5 of 13 , Jun 13, 2013
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              I just installed a 3kW hydro grid tied system in the Idaho mountains 7 months ago. The local power utility required me to meet their interconnect standards.

               

              One option was a protective gen-set type controller system such as a Schweitzer SEL700. This approach would have cost about $10K USD and needed to be initially tested and recertified annually by and independent state licensed engineer at my expense.

               

              The other option was to use a 3ph PMA with a rectified output full load voltage above 200VDC which is then feed into a grid-tie inverter. The local power company treated it the same way as a small wind turbine with GTI. With the GTI being UL 1741/IEEE-1547 compliant the power company did a simple disconnect test to verified that it waited at least 5 minutes before reconnecting. The power company has the option to retest every 3 years at their expense.

               

              I used a SMA SB3000 GTI inverter for this system along with a used 5kW 10pole servo motor rated at 95% eff. The GTI was programmed to run in constant voltage mode which effective set the turbine RPM at max power point. One thing you need to watch for is the unloaded turbine voltage not exceed the GTI input max. If that is a issue you can install a voltage shunt regulator that are common in motor braking application.

               

              Protection relay or GTI choice really comes down to a cost of instillation and on going expense like recertification. In my case it was also much faster to get start-up approval since it was just another GTI like many solar systems on net-metering.

               

              Regards,

              Scott

               

               

            • blabs2003
              Jeff, I am interested in using a 48 volt grid tie inverter also, but for a different reason. My water source becomes scarce in the summer, but the sun shines
              Message 6 of 13 , Jun 14, 2013
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                Jeff,
                I am interested in using a 48 volt grid tie inverter also, but for a different reason. My water source becomes scarce in the summer, but the sun shines strongly and solar panels are approaching $1/watt. I want to switch from a 3.5 kw induction motor to a PMDC unit. The largest I have found is in the 1.5 kw range. The 48 volt DC grid tie inverter is available for around $3K. I am in the pricing and design stage now. One problem I have run into is that a solar unit is allowed without huge licensing problems but not a hydro in California. I consider electrons are electrons.

                An approved solar unit that can be fed from a hydro unit in the winter should not meet with objections.

                David Green


                --- In microhydro@yahoogroups.com, Jeff Grebe <jeffgrebe@...> wrote:
                >
                > Nando, not to get into an argument but I disagree with the statement that all you need is an induction motor. This is theoretically true but not in practice. Every utility that I am aware of and IEEE 1547 have very specific interconnect requirement that require at the minimum protective relays. Remember your are not just protecting against islanding but also from such things as over/under voltage over/under frequency etc.
                >
                > My experience has been that when you get into small systems that a UL listed inverter that has those safeties built in and tested is actually cheaper than a purchased protective relay package that requires field wiring and testing and greatly simplifies the negotiations with the utility.
                >
                >
                > Jeff Grebe
                >
                > To: microhydro@yahoogroups.com
                > From: nando37@...
                > Date: Wed, 12 Jun 2013 21:56:11 -0500
                > Subject: Re: [microhydro] Grid-tie inverter microhydro system
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                >
                > They are trying to snow you down .
                >
                >
                >
                > The only thing you need to demonstrate is that if you are using an
                > induction motor as a generator without any capacitors if the Grid
                > drops the induction generator drops as well because the Grid
                > electrical power is the what makes the induction motor to produce
                > power into the Grid.
                >
                >
                >
                > Instead with a Vac Inverter You need to have a high cost inverter
                > with Grid drop protection -- totally unnecessary
                >
                >
                >
                > Nando
                >
                >
                >
                >
                >
                >
                >
                > On 6/12/2013 12:44, Kevin Edwards
                > wrote:
                >
                >
                >
                >
                >
                >
                > All,
                >
                >
                >
                > I am working to develop a microhydro site that will be
                > grid connected, in the United States. At first I wanted
                > to use a simple induction motor as generator, but the
                > utility will require an excessive amount of protection
                > equipment for this, costing over $40000. This is the same
                > equipment they would require for a 2 MW plant! They were
                > not interested in the utility grade protective relaying I
                > proposed.
                >
                >
                >
                > They are also willing to allow a connection if we use a
                > UL-1741 certified inverter, like would be used for
                > grid-tie solar.
                >
                >
                >
                > The prime mover is a 24' diameter steel overshot wheel, so
                > there will be gears/belts to increase the speed no matter
                > what generator is chosen. Normally we work on equipment
                > from a few hundred kilowatts to a few megawatts, so this
                > is outside my experience range. My question for the group
                > is: what is the best way to make 48VDC from the available
                > shaft power?
                >
                >
                >
                > This is the first idea that came to me:
                >
                > Waterwheel -> speed increaser -> Brushless AC
                > synchronous generator -> 48v battery charger ->
                > 48vdc / 10 kW 120VAC inverter
                >
                >
                >
                > Better would be a PMDC generator that directly output 48v
                > (or 24v) DC. Any ideas on sourcing this?
                >
                >
                >
                > Thanks!
                >
                >
                >
                > Kevin
                >
                >
                >
                > ---
                >
                > Kevin Edwards
                >
                > Mechanical Engineer
                >
                > Piedmont Hydro Technologies, LLC
                >
                > kevin.edwards@...
                >
                > 336.589.6138
                >
                > www.piedmonthydrotech.com
                >
              • arrow28r@rocketmail.com
                Hi Nando Is it possible to continue to generate without the grid by using capacitors on the generator terminals? I am thinking about our situation where we
                Message 7 of 13 , Jun 14, 2013
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                  Hi Nando
                  Is it possible to continue to generate without the grid by using capacitors on the generator terminals? I am thinking about our situation where we will be wanting to go grid tied and if the grid drops off, still be able to generate locally using an induction motor. If this is what we want to do, are we better consider a different type of generator or is the induction motor(generator) still OK in this situation?
                  Thanks
                  Peter

                  --- In microhydro@yahoogroups.com, nando37 <nando37@...> wrote:
                  >
                  > JEFF:
                  >
                  > Not getting into an argument but one needs to know how the induction
                  > motor works as a generator.
                  >
                  > The motor does not produce power UNLESS the GRID applies power to the
                  > motor but the motor to convert into a generator the turbine attached to
                  > the motor HAS to make the motor rotate to the motor RPM RATE PLUS the
                  > Slip factor of the motor so if the motor is 1800 RPM rated, as a motor
                  > the RPM may be 1740 RPM and as a generator the RPM has to be set to 1800
                  > Plus ( 1800 - 1740 ) = 1800 + 60 = 1860 RPM to start producing power
                  > into the GRID .
                  >
                  > Now if the GRID for some reason is disconnected the motor automatically
                  > stop producing power because it does not have the necessary polarization
                  > to produce power..
                  >
                  > Now things like over /under voltage is defined by the Grid voltage --
                  > also the frequency is totally defined by the GRID so there is not an
                  > over / under frequency -- because is defined by the Grid.
                  >
                  > So a simple relay set up to disconnect the motor leads from the GRID
                  > lines. --- I could extend myself but I think that this is enough for
                  > the moment !! and the protective relay is really cheaper compared to the
                  > inverter and all the paraphernalia needed with the inverter.
                  >
                  > Nando
                  >
                  >
                  > On 6/13/2013 11:51, Jeff Grebe wrote:
                  > >
                  > > Nando, not to get into an argument but I disagree with the statement
                  > > that all you need is an induction motor. This is theoretically true
                  > > but not in practice. Every utility that I am aware of and IEEE 1547
                  > > have very specific interconnect requirement that require _at the
                  > > minimum _protective relays. Remember your are not just protecting
                  > > against islanding but also from such things as over/under voltage
                  > > over/under frequency etc.
                  > >
                  > > My experience has been that when you get into small systems that a UL
                  > > listed inverter that has those safeties built in and tested is
                  > > actually cheaper than a purchased protective relay package that
                  > > requires field wiring and testing and greatly simplifies the
                  > > negotiations with the utility.
                  > >
                  > >
                  > > Jeff Grebe
                  > >
                  > >
                  > > ------------------------------------------------------------------------
                  > > To: microhydro@yahoogroups.com
                  > > From: nando37@...
                  > > Date: Wed, 12 Jun 2013 21:56:11 -0500
                  > > Subject: Re: [microhydro] Grid-tie inverter microhydro system
                  > >
                  > >
                  > >
                  > > They are trying to snow you down .
                  > >
                  > > The only thing you need to demonstrate is that if you are using an
                  > > induction motor as a generator without any capacitors if the Grid
                  > > drops the induction generator drops as well because the Grid
                  > > electrical power is the what makes the induction motor to produce
                  > > power into the Grid.
                  > >
                  > > Instead with a Vac Inverter You need to have a high cost inverter with
                  > > Grid drop protection -- totally unnecessary
                  > >
                  > > Nando
                  > >
                  > >
                  > >
                  > > On 6/12/2013 12:44, Kevin Edwards wrote:
                  > >
                  > > All,
                  > >
                  > > I am working to develop a microhydro site that will be grid
                  > > connected, in the United States. At first I wanted to use a
                  > > simple induction motor as generator, but the utility will require
                  > > an excessive amount of protection equipment for this, costing over
                  > > $40000. This is the same equipment they would require for a 2 MW
                  > > plant! They were not interested in the utility grade protective
                  > > relaying I proposed.
                  > >
                  > > They are also willing to allow a connection if we use a UL-1741
                  > > certified inverter, like would be used for grid-tie solar.
                  > >
                  > > The prime mover is a 24' diameter steel overshot wheel, so there
                  > > will be gears/belts to increase the speed no matter what generator
                  > > is chosen. Normally we work on equipment from a few hundred
                  > > kilowatts to a few megawatts, so this is outside my experience
                  > > range. My question for the group is: what is the best way to make
                  > > 48VDC from the available shaft power?
                  > >
                  > > This is the first idea that came to me:
                  > > Waterwheel -> speed increaser -> Brushless AC synchronous
                  > > generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter
                  > >
                  > > Better would be a PMDC generator that directly output 48v (or 24v)
                  > > DC. Any ideas on sourcing this?
                  > >
                  > > Thanks!
                  > >
                  > > Kevin
                  > >
                  > > ---
                  > > Kevin Edwards
                  > > Mechanical Engineer
                  > > Piedmont Hydro Technologies, LLC
                  > > kevin.edwards@...
                  > > <mailto:kevin.edwards@...>
                  > > 336.589.6138
                  > > www.piedmonthydrotech.com <http://www.piedmonthydrotech.com>
                  > >
                  > >
                  > >
                  > >
                  > >
                  >
                • Jeff Grebe
                  Nando. I assure you that I understand how an induction alternator works and we agree on the basic concept. I also assure you that you can t hook an induction
                  Message 8 of 13 , Jun 14, 2013
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                    Nando. I assure you that I understand how an induction alternator works and we agree on the basic concept.  I also assure you that you can't hook an induction alternator into the grid  in the US without protective relays.  While the wiring of an induction alternator protects from sending powering into a dead grid (islanding) it does not prevent the over/under voltage impacts, ground faults. harmonics, etc that a powered alternator can have on an active grid.  This is why ALL utility interconnect standards and IEEE dictate a minimum protective relay package.  You should really read IEEE 1547 before you give advice about connecting to the grid in the US.
                    As stated in another post recently, the minimum package of relays for most utilities in the US costs about $10k  This is before wiring, testing and calibration. Some utilities don't recognize risk / impact versus scale and the requirements are even higher.
                     I stand by my contention that for a grid connected small hydro (<10 kW) it is  more cost effective to use an prepackaged, wired tested, UL approved inverter in an AC/DC/AC setup. Utilities are very used to these inverters at this point due to all the solar connections and it is generally a very simply process to get them approved


                    Jeff  Grebe

                     

                    To: microhydro@yahoogroups.com
                    From: nando37@...
                    Date: Fri, 14 Jun 2013 00:04:23 -0500
                    Subject: Re: [microhydro] Grid-tie inverter microhydro system



                    JEFF:

                    Not getting into an argument but one needs to know how the induction motor works as a generator.

                    The motor does not produce power UNLESS the GRID applies power to the motor  but the motor to convert into a generator the turbine attached to the motor HAS to make the motor rotate to the motor RPM RATE PLUS the Slip factor of the motor so if the motor is 1800 RPM rated, as a motor the RPM may be 1740 RPM and as a generator the RPM has to be set to 1800 Plus ( 1800 - 1740 ) = 1800 + 60 = 1860 RPM to start producing power into the GRID .

                    Now if the GRID for some reason is disconnected the motor automatically stop producing power because it does not have the necessary polarization to produce power..

                    Now  things like over /under voltage is defined by the Grid voltage -- also the frequency is totally defined by the GRID so there is not an over / under frequency -- because is defined by the Grid.

                    So a simple relay set up to disconnect the motor leads from the GRID lines.  --- I could extend myself but I think that this is enough for the moment !! and the protective relay is really cheaper compared to the inverter and all the paraphernalia needed with the inverter.

                    Nando
                     

                    On 6/13/2013 11:51, Jeff Grebe wrote:
                     

                    Nando, not to get into an argument but I disagree with the statement that all you need is an induction motor.  This is theoretically true but not in practice.  Every utility that I am aware of and IEEE 1547 have very specific interconnect requirement that require at the minimum protective relays.  Remember your are not just protecting against islanding but also from such things as over/under voltage over/under frequency etc. 
                     
                    My experience has been that when you get into small systems that a UL listed inverter that has those safeties built in and tested is actually  cheaper than a purchased protective relay package that requires field wiring and testing and greatly simplifies the negotiations with the utility. 


                    Jeff  Grebe

                     

                    To: microhydro@yahoogroups.com
                    From: nando37@...
                    Date: Wed, 12 Jun 2013 21:56:11 -0500
                    Subject: Re: [microhydro] Grid-tie inverter microhydro system



                    They are trying to snow you down .

                    The only thing you need to demonstrate is that if you are using an induction motor as a generator without any capacitors if the Grid drops the induction generator drops as well because the Grid electrical power is the what makes the induction motor to produce power into the Grid.

                    Instead with a Vac Inverter You need to have a high cost inverter with Grid drop protection -- totally unnecessary

                    Nando



                    On 6/12/2013 12:44, Kevin Edwards wrote:
                     
                    All,

                    I am working to develop a microhydro site that will be grid connected, in the United States.  At first I wanted to use a simple induction motor as generator, but the utility will require an excessive amount of protection equipment for this, costing over $40000.  This is the same equipment they would require for a 2 MW plant!  They were not interested in the utility grade protective relaying I proposed.

                    They are also willing to allow a connection if we use a UL-1741 certified inverter, like would be used for grid-tie solar.

                    The prime mover is a 24' diameter steel overshot wheel, so there will be gears/belts to increase the speed no matter what generator is chosen.  Normally we work on equipment from a few hundred kilowatts to a few megawatts, so this is outside my experience range.  My question for the group is: what is the best way to make 48VDC from the available shaft power?

                    This is the first idea that came to me:
                    Waterwheel -> speed increaser -> Brushless AC synchronous generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter

                    Better would be a PMDC generator that directly output 48v (or 24v) DC.  Any ideas on sourcing this?

                    Thanks!

                    Kevin

                    ---
                    Kevin Edwards
                    Mechanical Engineer
                    Piedmont Hydro Technologies, LLC
                    kevin.edwards@...
                    336.589.6138
                    www.piedmonthydrotech.com






                  • nando37
                    Induction motors as generators require a simple set up to produce power . For those interested Nigel Smith wrote : Motors as Generators for micro hydro
                    Message 9 of 13 , Jun 15, 2013
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                      Induction motors as generators require a simple set up to produce power .

                      For those interested  Nigel Smith wrote : "Motors as Generators for micro hydro power" , that can be Google to find where there are PDF copies of it in English or even in Spanish as I was told.

                      The pamphlet describe quite well how to convert the induction motor into a generator -- I was aware of how to do the conversion for many decades when I read it , in French, when doing some high school homework and used to produce power.

                      In Grid  connection to dump power into the Grid it is a simple procedure to do since the Grid voltage biases the motor into a generator when the generator is rotated  with its rated RPM plus the % slip for such motor.

                      When the Grid drops the only thing to do is to wait a second then using relays with a small battery to connect the polarizing capacitors with a ballast controller to stabilize the output voltage , in some cases due to the high quality metal of the motor with very low magnetic retention it is necessary to be able to produce the initial kick to make the motor into a generator, one way is to have a 12 volts battery with a small converter to produce, lets say 200 volts DC to charge one of the capacitors , so  when the relay connect the capacitors to the the motor leads the charged capacitor excites the motor into a generator, one needs to be careful because the need to start or to stop the motor without any load -- basic step to insure to have a generator working every time, the same small converter transformer can be used to float charge the 12 volts battery .

                      The drop of the Grid that generates the operation of the isolation relay also connects the small converter to the capacitor to charge during that one second and the relay connecting the capacitors disconnects the converter from the capacitor and then once the ballast starts to control the voltage the converter becomes a battery charger to  keep the battery in float charge conditions for long life ( 13.5 volts ) .

                      Induction motors as generators are being used all over the world because they are cheaper and easier to attain, for single phase , it is best to have a 3 phase motor connected DELTA and using the C & 2C capacitors circuit.

                      If the motor is going to use the 3 phases then use the C & C & C circuit to equate all the phases for better generator operation

                      Using simple controllers and giving the necessary times to do the transitions from one mode to the other a very effective system is developed.

                      I have used induction motors from  200 watt up to about 25 KW in the far past .

                      The Ballast controllers for the small systems I have used an amplifier plus a couple of transistors and one LM555 to trigger a Triac  to load the generator phase angle wise and for the much higher power the  Ballast controller I have used an amplifier and several integrated circuits to control multiple ballast in incrementing/decrementing steps to maintain the stabilized frequency or voltage depending on the type of ballast controller desired.

                      Now - a - days with a microprocessor the ballast controller is much easier to design and build if one knows how to program the smaller available processors.

                      Nando
                      On 6/14/2013 22:20, arrow28r@... wrote:
                       

                      Hi Nando
                      Is it possible to continue to generate without the grid by using capacitors on the generator terminals? I am thinking about our situation where we will be wanting to go grid tied and if the grid drops off, still be able to generate locally using an induction motor. If this is what we want to do, are we better consider a different type of generator or is the induction motor(generator) still OK in this situation?
                      Thanks
                      Peter

                      --- In microhydro@yahoogroups.com, nando37 <nando37@...> wrote:
                      >
                      > JEFF:
                      >
                      > Not getting into an argument but one needs to know how the induction
                      > motor works as a generator.
                      >
                      > The motor does not produce power UNLESS the GRID applies power to the
                      > motor but the motor to convert into a generator the turbine attached to
                      > the motor HAS to make the motor rotate to the motor RPM RATE PLUS the
                      > Slip factor of the motor so if the motor is 1800 RPM rated, as a motor
                      > the RPM may be 1740 RPM and as a generator the RPM has to be set to 1800
                      > Plus ( 1800 - 1740 ) = 1800 + 60 = 1860 RPM to start producing power
                      > into the GRID .
                      >
                      > Now if the GRID for some reason is disconnected the motor automatically
                      > stop producing power because it does not have the necessary polarization
                      > to produce power..
                      >
                      > Now things like over /under voltage is defined by the Grid voltage --
                      > also the frequency is totally defined by the GRID so there is not an
                      > over / under frequency -- because is defined by the Grid.
                      >
                      > So a simple relay set up to disconnect the motor leads from the GRID
                      > lines. --- I could extend myself but I think that this is enough for
                      > the moment !! and the protective relay is really cheaper compared to the
                      > inverter and all the paraphernalia needed with the inverter.
                      >
                      > Nando
                      >
                      >
                      > On 6/13/2013 11:51, Jeff Grebe wrote:
                      > >
                      > > Nando, not to get into an argument but I disagree with the statement
                      > > that all you need is an induction motor. This is theoretically true
                      > > but not in practice. Every utility that I am aware of and IEEE 1547
                      > > have very specific interconnect requirement that require _at the
                      > > minimum _protective relays. Remember your are not just protecting
                      > > against islanding but also from such things as over/under voltage
                      > > over/under frequency etc.
                      > >
                      > > My experience has been that when you get into small systems that a UL
                      > > listed inverter that has those safeties built in and tested is
                      > > actually cheaper than a purchased protective relay package that
                      > > requires field wiring and testing and greatly simplifies the
                      > > negotiations with the utility.
                      > >
                      > >
                      > > Jeff Grebe
                      > >
                      > >
                      > > ----------------------------------------------------------
                      > > To: microhydro@yahoogroups.com
                      > > From: nando37@...
                      > > Date: Wed, 12 Jun 2013 21:56:11 -0500
                      > > Subject: Re: [microhydro] Grid-tie inverter microhydro system
                      > >
                      > >
                      > >
                      > > They are trying to snow you down .
                      > >
                      > > The only thing you need to demonstrate is that if you are using an
                      > > induction motor as a generator without any capacitors if the Grid
                      > > drops the induction generator drops as well because the Grid
                      > > electrical power is the what makes the induction motor to produce
                      > > power into the Grid.
                      > >
                      > > Instead with a Vac Inverter You need to have a high cost inverter with
                      > > Grid drop protection -- totally unnecessary
                      > >
                      > > Nando
                      > >
                      > >
                      > >
                      > > On 6/12/2013 12:44, Kevin Edwards wrote:
                      > >
                      > > All,
                      > >
                      > > I am working to develop a microhydro site that will be grid
                      > > connected, in the United States. At first I wanted to use a
                      > > simple induction motor as generator, but the utility will require
                      > > an excessive amount of protection equipment for this, costing over
                      > > $40000. This is the same equipment they would require for a 2 MW
                      > > plant! They were not interested in the utility grade protective
                      > > relaying I proposed.
                      > >
                      > > They are also willing to allow a connection if we use a UL-1741
                      > > certified inverter, like would be used for grid-tie solar.
                      > >
                      > > The prime mover is a 24' diameter steel overshot wheel, so there
                      > > will be gears/belts to increase the speed no matter what generator
                      > > is chosen. Normally we work on equipment from a few hundred
                      > > kilowatts to a few megawatts, so this is outside my experience
                      > > range. My question for the group is: what is the best way to make
                      > > 48VDC from the available shaft power?
                      > >
                      > > This is the first idea that came to me:
                      > > Waterwheel -> speed increaser -> Brushless AC synchronous
                      > > generator -> 48v battery charger -> 48vdc / 10 kW 120VAC inverter
                      > >
                      > > Better would be a PMDC generator that directly output 48v (or 24v)
                      > > DC. Any ideas on sourcing this?
                      > >
                      > > Thanks!
                      > >
                      > > Kevin
                      > >
                      > > ---
                      > > Kevin Edwards
                      > > Mechanical Engineer
                      > > Piedmont Hydro Technologies, LLC
                      > > kevin.edwards@...
                      > > <mailto:kevin.edwards@...>
                      > > 336.589.6138
                      > > www.piedmonthydrotech.com <http://www.piedmonthydrotech.com>
                      > >
                      > >
                      > >
                      > >
                      > >
                      >


                    • k r
                      David, A lot of our hydro customers in California put in a good size solar system for grid-tie purposes and then sneak the hydro in later. An RE source
                      Message 10 of 13 , Jun 17, 2013
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                        David,
                         
                        A lot of our hydro customers in California put in a good size solar system for grid-tie purposes and then "sneak" the hydro in later.
                        An RE source should be an RE source but.........Most utilities are harder on wind/hydro as they require voltage clamps, redundant diversion loads, etc as they are concerned about overspeed/overvoltage.
                         

                        To: microhydro@yahoogroups.com
                        From: hookjawbrown@...
                        Date: Fri, 14 Jun 2013 13:35:07 +0000
                        Subject: [microhydro] Re: Grid-tie inverter microhydro system

                         
                        Jeff,
                        I am interested in using a 48 volt grid tie inverter also, but for a different reason. My water source becomes scarce in the summer, but the sun shines strongly and solar panels are approaching $1/watt. I want to switch from a 3.5 kw induction motor to a PMDC unit. The largest I have found is in the 1.5 kw range. The 48 volt DC grid tie inverter is available for around $3K. I am in the pricing and design stage now. One problem I have run into is that a solar unit is allowed without huge licensing problems but not a hydro in California. I consider electrons are electrons.

                        An approved solar unit that can be fed from a hydro unit in the winter should not meet with objections.

                        David Green

                        --- In microhydro@yahoogroups.com, Jeff Grebe <jeffgrebe@...> wrote:
                        >
                        > Nando, not to get into an argument but I disagree with the statement that all you need is an induction motor. This is theoretically true but not in practice. Every utility that I am aware of and IEEE 1547 have very specific interconnect requirement that require at the minimum protective relays. Remember your are not just protecting against islanding but also from such things as over/under voltage over/under frequency etc.
                        >
                        > My experience has been that when you get into small systems that a UL listed inverter that has those safeties built in and tested is actually cheaper than a purchased protective relay package that requires field wiring and testing and greatly simplifies the negotiations with the utility.
                        >
                        >
                        > Jeff Grebe
                        >
                        > To: microhydro@yahoogroups.com
                        > From: nando37@...
                        > Date: Wed, 12 Jun 2013 21:56:11 -0500
                        > Subject: Re: [microhydro] Grid-tie inverter microhydro system
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > They are trying to snow you down .
                        >
                        >
                        >
                        > The only thing you need to demonstrate is that if you are using an
                        > induction motor as a generator without any capacitors if the Grid
                        > drops the induction generator drops as well because the Grid
                        > electrical power is the what makes the induction motor to produce
                        > power into the Grid.
                        >
                        >
                        >
                        > Instead with a Vac Inverter You need to have a high cost inverter
                        > with Grid drop protection -- totally unnecessary
                        >
                        >
                        >
                        > Nando
                        >
                        >
                        >
                        >
                        >
                        >
                        >
                        > On 6/12/2013 12:44, Kevin Edwards
                        > wrote:
                        >
                        >
                        >
                        >
                        >
                        >
                        > All,
                        >
                        >
                        >
                        > I am working to develop a microhydro site that will be
                        > grid connected, in the United States. At first I wanted
                        > to use a simple induction motor as generator, but the
                        > utility will require an excessive amount of protection
                        > equipment for this, costing over $40000. This is the same
                        > equipment they would require for a 2 MW plant! They were
                        > not interested in the utility grade protective relaying I
                        > proposed.
                        >
                        >
                        >
                        > They are also willing to allow a connection if we use a
                        > UL-1741 certified inverter, like would be used for
                        > grid-tie solar.
                        >
                        >
                        >
                        > The prime mover is a 24' diameter steel overshot wheel, so
                        > there will be gears/belts to increase the speed no matter
                        > what generator is chosen. Normally we work on equipment
                        > from a few hundred kilowatts to a few megawatts, so this
                        > is outside my experience range. My question for the group
                        > is: what is the best way to make 48VDC from the available
                        > shaft power?
                        >
                        >
                        >
                        > This is the first idea that came to me:
                        >
                        > Waterwheel -> speed increaser -> Brushless AC
                        > synchronous generator -> 48v battery charger ->
                        > 48vdc / 10 kW 120VAC inverter
                        >
                        >
                        >
                        > Better would be a PMDC generator that directly output 48v
                        > (or 24v) DC. Any ideas on sourcing this?
                        >
                        >
                        >
                        > Thanks!
                        >
                        >
                        >
                        > Kevin
                        >
                        >
                        >
                        > ---
                        >
                        > Kevin Edwards
                        >
                        > Mechanical Engineer
                        >
                        > Piedmont Hydro Technologies, LLC
                        >
                        > kevin.edwards@...
                        >
                        > 336.589.6138
                        >
                        > www.piedmonthydrotech.com
                        >


                      • Kevin Edwards
                        Indeed, a grid-tied induction motor as generator would be the best technical solution. I even have Motors as Generators for Micro-Hydropower on my shelf,
                        Message 11 of 13 , Jun 17, 2013
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                          Indeed, a grid-tied induction motor as generator would be the best technical solution.  I even have "Motors as Generators for Micro-Hydropower" on my shelf, and have built several grid-tied plants using motors as generators (up to 75kW).  I proposed this to the utility, along with a Basler 11g relay, all the settings configuration, 1-line diagram, etc.  It met all IEEE 1547 specs. They rejected this proposal, and are completely inflexible.  I have tried similar arguments with this utility before on larger plants, and failed to move them.  I thought that perhaps a 10 kW system would be small enough that they would allow us to provide the protection.  Not every Utility is this way - I have built several systems where the protection was as described above, and other utilities have accepted them.  But it's not going to happen in this case.

                          So, AC-DC-AC it is.  My goal is 8-10 kW electrical output from the inverter.  Will a single-phase brushless AC generator be sufficient, or should I look for a 3 phase one?  My concern is the rectified output of a single phase machine is rather bumpy, whereas 3-phase rectified is rather smooth.  As I haven't used an inverter this way before, I have a concern about whether it will tolerate a rough input DC waveform.  My preference is single phase, unless there will be a problem there.

                          Can any of you provide recommendations about which generator and inverter to choose?  I'm just thinking about manufacturers and suppliers, not the detailed selection.  I am outside my usual experience range, and my usual suppliers don't offer these.

                          Thank you all!
                          Kevin

                        • Jeff Grebe
                          Kevin, wind is not my specialty, having only done a few, but my understanding is that small wind turbines are basically this set up. Namely AC alternators,
                          Message 12 of 13 , Jun 17, 2013
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                            Kevin, wind is not my specialty, having only done a few, but my understanding is that small wind turbines are basically this set up. Namely AC alternators, rectifiers producing DC and inverters back to AC. I like Sunny Boy Inverters (SMA) and I know they make a Windy Boy that might be the ticket. Take a look and their technical staff is very helpful so call and run the questions through them


                            --- In microhydro@yahoogroups.com, Kevin Edwards <kevindedwards@...> wrote:
                            >
                            > Indeed, a grid-tied induction motor as generator would be the best
                            > technical solution. I even have "Motors as Generators for
                            > Micro-Hydropower" on my shelf, and have built several grid-tied plants
                            > using motors as generators (up to 75kW). I proposed this to the utility,
                            > along with a Basler 11g relay, all the settings configuration, 1-line
                            > diagram, etc. It met all IEEE 1547 specs. They rejected this proposal, and
                            > are completely inflexible. I have tried similar arguments with this
                            > utility before on larger plants, and failed to move them. I thought that
                            > perhaps a 10 kW system would be small enough that they would allow us to
                            > provide the protection. Not every Utility is this way - I have built
                            > several systems where the protection was as described above, and other
                            > utilities have accepted them. But it's not going to happen in this case.
                            >
                            > So, AC-DC-AC it is. My goal is 8-10 kW electrical output from the
                            > inverter. Will a single-phase brushless AC generator be sufficient, or
                            > should I look for a 3 phase one? My concern is the rectified output of a
                            > single phase machine is rather bumpy, whereas 3-phase rectified is rather
                            > smooth. As I haven't used an inverter this way before, I have a concern
                            > about whether it will tolerate a rough input DC waveform. My preference is
                            > single phase, unless there will be a problem there.
                            >
                            > Can any of you provide recommendations about which generator and inverter
                            > to choose? I'm just thinking about manufacturers and suppliers, not the
                            > detailed selection. I am outside my usual experience range, and my usual
                            > suppliers don't offer these.
                            >
                            > Thank you all!
                            > Kevin
                            >
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