Power system having AC and DC power sources
View Patent ↗A power system ( 110; 210; 310 ) combines a power source ( 14 ) having a DC output ( 20 A, 20 B) with an AC supply from the AC grid ( 12 ) to provide AC to customer's loads ( 16 ) and DC to various DC auxiliary loads ( 134, 134 A). The DC output of the DC power source ( 14 ) is connected in steady-state to the DC input ( 120 A, 120 B, 60 ) of a converter/bi-directional inverter ( 122; 222 ) for conversion therein to AC for connection ( 124, 124 A, 32 ) to the customer's loads ( 16 ) and ( 124, 124 B) to any AC auxiliary loads ( 134, 234 ). During start-up of the DC power source ( 14 ), an open isolation switch ( 70 ) disconnects that DC power source ( 14 ) from the bi-directional inverter ( 122; 222 ). A start-up power supply ( 50, 60; 250, 60; 90, 180, 60 ) selectively connects ( 56; 94 ) between the AC power grid ( 12 ) and the bi-directional inverter ( 122; 222 ) and/or DC controllers ( 134 A) to provide a supply of rectified DC power at the inverter DC input and to certain DC auxiliary loads ( 134, 234 ). DC power is supplied to the auxiliary loads ( 134; 234 ) from the inverter DC input substantially continuously during start-up and steady state.
1. A power system ( 110 ; 210 ; 310 ) comprising:
a power source ( 14 ) having a DC output ( 20 A, 20 B);
a power converter ( 122 ; 222 ) for converting DC at a DC input/terminal ( 120 A, 120 B) thereof to AC at an AC output/terminal ( 124 ) thereof;
a supply of AC from an AC power source ( 12 );
an electrical connection ( 124 , 124 A, 32 ) between the AC output/terminal of the converter ( 122 ; 222 ) and at least one general load ( 16 ) to supply AC power to those loads;
an AC power source-connect switch ( 30 ) connected ( 124 , 124 A, 28 A, 28 ) between the AC output/terminal ( 124 ) of the converter and the supply of AC from the AC power source configured to selectively connect and disconnect the AC power source ( 12 ) in parallel with the AC output/terminal ( 124 ) of the converter ( 122 ; 222 );
at least one DC auxiliary load ( 134 , 134 A, 134 B; 234 ) to operate the power source ( 14 ) having the DC output;
a start-up power supply ( 50 , 60 ; 250 , 60 ; 90 , 180 , 60 ), connectable ( 28 , 128 , 58 , 30 , 124 A, 124 ; 28 , 128 , 258 , 30 124 A, 124 ; 28 , 228 , 92 , 30 , 124 a , 124 ) between the supply of AC from the AC power source ( 12 ) and at least the converter ( 122 ; 222 ) during at least start-up of the power source ( 14 ) having the DC output, and being responsive to a supply ( 28 , 128 , 228 , 30 , 124 A, 124 ) of AC power ( 12 ) to provide a start-up supply of DC power ( 60 ; 60 , 90 ) at least at the DC input ( 120 A, 120 B) of the converter ( 122 ; 222 );
an isolation switch ( 70 ) operatively connected between the output ( 20 A, 20 B) of the power source ( 14 ) having the DC output and the DC input/terminal ( 120 A, 120 B) of the converter ( 122 ; 222 ) and configured to selectively isolate DC at the DC input of the converter from the DC power source during start-up of the source ( 14 ) having the DC output; and
an electrical connection ( 120 AB) to supply DC power at the DC input/terminal ( 120 A, 120 B, 60 ) of the converter ( 122 , 222 ) to the at least one DC auxiliary load ( 134 , 134 A, 134 B, 234 ) without further conversion.
2. The power system ( 110 ; 210 ; 310 ) of claim 1 wherein the said power source having a DC output comprises at least one fuel cell ( 14 ).
3. The power system ( 110 ; 210 ; 310 ) of claim 1 wherein said power converter ( 122 ; 222 ) comprises a bi-directional inverter ( 122 ; 222 ).
4. The power system ( 110 ; 210 ; 310 ) of claim 1 wherein the at least one DC auxiliary load ( 134 , 134 A, 134 B; 234 ) comprises at least a DC-powered controller ( 134 A) having an Electronic Control System and a Power Control System.
5. The power system ( 110 ; 210 ; 310 ) of claim 1 wherein said start-up power supply ( 50 , 60 ; 250 , 60 ) comprises a precharge circuit ( 50 ; 250 ) having a switch ( 56 ) for selectively connecting and disconnecting said AC supply from the AC power source ( 12 ) through said precharge circuit to said converter ( 122 ; 222 ), whereby the connection from said AC power source to said converter through the precharge circuit may be disconnected after start-up of the power source ( 14 ) having the DC output.
6. The power system ( 110 ) of claim 1 wherein said start-up power supply ( 50 , 60 ) comprises a precharge circuit ( 50 ) having a rectifier ( 52 ) for converting AC to a DC output, and wherein the DC output of said precharge circuit is connected ( 58 ) to a DC link capacitor ( 60 ) across the DC input/terminal ( 120 A, 120 B) of said converter ( 122 ).
7. The power system ( 210 ) of claim 3 wherein said start-up power supply comprises a precharge circuit ( 250 ) having a current-limited, switchable connection ( 254 , 56 ) between the supply of AC from the AC power source ( 12 ) and the AC output/terminal ( 124 ) of the bi-directional inverter ( 222 ), whereby current-limited AC from the AC supply is rectified by the bi-directional inverter ( 222 ) and appears as DC at a DC link capacitor ( 60 ) across the DC input/terminal ( 120 A, 120 B) of the inverter ( 222 ).
8. The power system ( 310 ) of claim 3 wherein the at least one DC auxiliary load ( 134 , 134 A, 134 b ; 234 ) comprises at least a DC-powered controller ( 134 A) having one or both of an Electronic Control System and a Power Control System, and wherein said start-up power supply comprises an AC to DC power supply operatively connectable between the AC power source ( 10 ) and the DC-powered controller ( 134 A) to supply a limited DC voltage thereto, an inductance ( 180 ) connected in series between the AC power source-connect switch ( 30 ) and the AC output/terminal ( 124 ) of the bi-directional inverter ( 222 ), and a DC link capacitor ( 60 ) across the DC input/terminal ( 120 A, 120 B) of said converter ( 122 ), whereby connection ( 92 ) of said limited DC voltage to said DC-powered controller ( 134 A) is operative to close said AC power source-connect switch ( 30 ) and supply current-limited AC power from the AC power source ( 10 ) through the inductance ( 180 ) to the AC output/terminal ( 124 ) of the inverter ( 222 ) for conversion to a DC voltage appearing on the DC link capacitor ( 60 ).
9. The power system ( 110 ; 210 ; 310 ) of claim 1 further including a connection ( 20 AB) between the power source ( 14 ) having the DC output and the at least one DC auxiliary load ( 134 , 134 A; 234 ), and wherein the at least one DC auxiliary load includes a load impedance ( 72 ) for controllably adjusting the voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ) to provide a reference voltage.
10. The power system ( 110 ; 210 ; 310 ) of claim 9 wherein the at least one DC auxiliary load ( 134 , 134 A; 234 ) further includes at least a DC-powered controller ( 134 A), which is operative to adjust the DC voltage across a DC link capacitor at the DC input/terminal ( 120 A, 120 B) of the converter ( 122 ; 222 ) to substantially match said reference voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ), and is also operative to close the isolation switch ( 70 ) to connect the DC output ( 20 A, 20 B) of the DC power source ( 14 ) with the DC input/terminal ( 120 A, 120 B) of the converter ( 122 , 222 ).
11. The power system ( 110 ; 210 ) of claim 4 wherein said power converter ( 122 ; 222 ) comprises a bi-directional inverter ( 122 ; 222 ), said AC power source-connect switch ( 30 ) is normally open, and wherein, following connection ( 120 AB) of DC power to said DC-powered controller ( 134 A), at least one of said Electronic Control System and said Power Control System acting to close the AC power source-connect switch to provide AC power ( 12 , 28 , 124 A, 124 ) to the AC output/terminal ( 124 ) of the bi-directional inverter ( 122 ; 222 ), whereby the AC power from said AC power source ( 12 ) is rectified by the bi-directional inverter and appears as DC voltage across a DC link capacitor ( 60 ) at the DC input/terminal ( 120 A, 120 B) of said inverter.
12. The power system ( 110 ; 210 ; 310 ) of claim 1 wherein the AC power source ( 12 ) comprises the AC electrical grid.
13. The power system ( 110 ) of claim 6 wherein the AC power source ( 12 ) comprises the AC electrical grid; said power source having a DC output comprises at least one fuel cell ( 14 ); said power converter ( 122 ) comprises a bi-directional inverter ( 122 ); said at least one DC auxiliary load ( 134 , 134 A, 134 B) comprises at least a DC-powered controller ( 134 A) having one or both of an Electronic Control System and a Power Control System; said start-up power supply ( 50 , 60 ) comprises a precharge circuit ( 50 ) having a switch ( 56 ) for selectively connecting and disconnecting said AC supply from the AC power source ( 12 ) through said precharge circuit to said converter ( 122 ), whereby the connection from said AC power source to said converter through the precharge circuit may be disconnected after start-up of the power source ( 14 ) having the DC output; a connection ( 20 AB) between the power source ( 14 ) having the DC output and the at least one DC auxiliary load ( 134 , 134 A), and wherein the at least one DC auxiliary load includes a load impedance ( 72 ) for controllably adjusting the voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ) to provide a reference voltage; said DC-powered controller ( 134 A) being operative to adjust the DC voltage across a DC link capacitor ( 60 ) at the DC input/terminal ( 120 A, 120 B) of the converter ( 122 ) to substantially match said reference voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ), and is also operative to close the isolation switch ( 70 ) to connect the DC output ( 20 A, 20 B) of the DC power source ( 14 ) with the DC input/terminal ( 120 A, 120 B) of the converter ( 122 ); said AC power source-connect switch ( 30 ) is normally open, and wherein, following connection ( 120 AB) of DC power to said DC-powered controller ( 134 A), at least one of said Electronic Control System and said Power Control System acts to close the AC power source-connect switch to provide AC power ( 12 , 28 , 124 A, 124 ) to the AC output/terminal ( 124 ) of the bi-directional inverter ( 122 ), whereby the AC power from said AC power source ( 12 ) is rectified by the bi-directional inverter and appears as DC voltage across a DC link capacitor ( 60 ) at the DC input/terminal ( 120 A, 120 B) of said inverter.
14. The power system ( 210 ) of claim 7 wherein the AC power source ( 12 ) comprises the AC electrical grid; said power source having a DC output comprises at least one fuel cell ( 14 ); said at least one DC auxiliary load ( 134 , 134 A, 134 B) comprises at least a DC-powered controller ( 134 A) having one or both of an Electronic Control System and a Power Control System; said start-up power supply ( 250 , 60 ) comprises a precharge circuit ( 250 ) having a switch ( 56 ) for selectively connecting and disconnecting said AC supply from the AC power source ( 12 ) through said precharge circuit to said converter ( 222 ), whereby the connection from said AC power source to said converter through the precharge circuit may be disconnected after start-up of the power source ( 14 ) having the DC output; a connection ( 20 AB) between the power source ( 14 ) having the DC output and the at least one DC auxiliary load ( 134 , 134 A), and wherein the at least one DC auxiliary load includes a load impedance ( 72 ) for controllably adjusting the voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ) to provide a reference voltage; said DC-powered controller ( 134 A) being operative to adjust the DC voltage across a DC link capacitor ( 60 ) at the DC input/terminal ( 120 A, 120 B) of the converter ( 222 ) to substantially match said reference voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ), and is also operative to close the isolation switch ( 70 ) to connect the DC output ( 20 A, 20 B) of the DC power source ( 14 ) with the DC input/terminal ( 120 A, 120 B) of the converter ( 222 ); said AC power source-connect switch ( 30 ) is normally open, and wherein, following connection ( 120 AB) of DC power to said DC-powered controller ( 134 A), at least one of said Electronic Control System and said Power Control System acts to close the AC power source-connect switch to provide AC power ( 12 , 28 , 124 A, 124 ) to the AC output/terminal ( 124 ) of the bi-directional inverter ( 122 ), whereby the AC power from said AC power source ( 12 ) is rectified by the bi-directional inverter and appears as DC voltage across a DC link capacitor ( 60 ) at the DC input/terminal ( 120 A, 120 B) of said inverter.
15. The power system ( 310 ) of claim 8 wherein the AC power source ( 12 ) comprises the AC electrical grid; said power source having a DC output comprises at least one fuel cell ( 14 ); and further including a connection ( 20 AB) between the power source ( 14 ) having the DC output and the at least one DC auxiliary load ( 134 , 134 A; 234 ), and wherein the at least one DC auxiliary load includes a load impedance ( 72 ) for controllably adjusting the voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ) to provide a reference voltage; said DC-powered controller ( 134 A) being operative to adjust the DC voltage across a DC link capacitor ( 60 ) at the DC input/terminal ( 120 A, 120 B) of the converter ( 222 ) to substantially match said reference voltage at the DC output ( 20 A, 20 B) of the DC power source ( 14 ), and being also operative to close the isolation switch ( 70 ) to connect the DC output ( 20 A, 20 B) of the DC power source ( 14 ) with the DC input/terminal ( 120 A, 120 B) of the converter ( 222 ).
16. The power system ( 110 , 210 , 310 ) of claim 3 further including an inductance ( 80 , 180 ) that is connectable in series between the supply of AC from the AC power source ( 12 ) and the AC output/terminal ( 124 ) of the bidirectional inverter.
17. The power system ( 110 , 210 , 310 ) of claim 16 wherein said inductance ( 80 , 180 ) comprises the inductance in an LCL filter ( 80 , 180 ).
18. The power system ( 110 , 210 , 310 ) of claim 1 including a DC link capacitor ( 60 ) operatively connected across the DC input/terminal ( 120 A, 120 B) of the power converter ( 122 , 222 ) and across which is provided the start-up supply of DC power.
19. The power system ( 110 , 210 , 310 ) of claim 18 wherein the voltage of the start-up supply of DC power across the DC link capacitor ( 60 ) is greater than 100 V DC .