Power conversion system and method
Systems and methods for operating a power conversion system that includes a sole DC/DC converter are described. The systems and methods reduce a total number of DC/DC converters in a power system that includes an electric energy storage device and a photovoltaic array. The system and method provide for transferring electrical charge from the photovoltaic array and the electric energy storage device to an alternating current stationary electrical grid via a DC bus and an inverter.
1. An electric power conversion system, comprising:
a direct current (DC) bus;
a DC power source directly electrically coupled to the DC bus;
an inverter directly coupled to the DC bus and electrically connectable to a stationary alternating current (AC) electric power grid, the inverter adapted to convert DC electric energy on the DC bus to AC electric energy for the stationary AC electric power grid;
an all iron redox flow battery, the all iron redox flow battery having a plating electrolyte and a redox electrolyte, the all iron redox flow battery adapted to permit the plating electrolyte and the redox electrolyte to comprise different molar concentrations of a predetermined salt; and
a sole DC/DC converter electrically coupled to the DC bus and the all iron redox flow battery, wherein a controller senses a voltage output and/or a current output of the DC power source via a DC power source sensor, and wherein the sole DC/DC converter includes transistors configured to switch in response to a signal transmitted by the controller to adjust a direction of current flow and/or adjust an effective impedance of the DC bus.
2. The electric power conversion system of claim 1 , wherein the DC power source is a photovoltaic array, and wherein the DC power source includes one or more blocking diodes adapted to permit electrical current flow from the DC power source to the DC bus and restrict or prevent electrical current flow from the DC bus to the DC power source.
3. The electric power conversion system of claim 2 , further comprising an AC power grid, and wherein the inverter is electrically coupled to the AC power grid.
4. The electric power conversion system of claim 3 , wherein the DC/DC converter is bi-directional.
5. The electric power conversion system of claim 4 , wherein the DC/DC converter includes the controller.
6. The electric power conversion system of claim 5 , further comprising executable instructions stored in non-transitory memory of the controller to operate the DC/DC converter in a buck mode to transfer electric power from the DC bus to the all iron redox flow battery.
7. The electric power conversion system of claim 6 , wherein the DC/DC converter is operated in the buck mode in response to an electrical load the DC bus provides to the DC power source.
8. The electric power conversion system of claim 7 , wherein the electrical load is less than an electrical load that causes the DC power source to operate substantially at a maximum power tracking point.
9. The electric power conversion system of claim 5 , further comprising executable instructions stored in non-transitory memory of the controller to operate the DC/DC converter in a boost mode to transfer electric power from a battery to the DC bus.
10. The electric power conversion system of claim 9 , wherein the DC/DC converter is operated in the boost mode in response to an electrical load the DC bus provides to the DC power source.
11. The electric power conversion system of claim 10 , wherein the electrical load is greater than an electrical load that causes the DC power source to operate substantially at a maximum power tracking point.
12. An electric power conversion system, comprising:
a direct current (DC) bus;
a DC power source directly electrically coupled to the DC bus;
an inverter directly coupled to the DC bus and electrically connectable to a stationary alternating current (AC) electric power grid, the inverter adapted to convert DC electric energy on the DC bus to AC electric energy for the stationary AC electric power grid;
a battery, the battery comprising an all iron redox flow battery having a plating electrolyte and a redox electrolyte, the all iron redox flow battery adapted to permit the plating electrolyte and the redox electrolyte to comprise different molar concentrations of a predetermined salt;
a sole DC/DC converter electrically coupled to the DC bus and the battery and including switchable transistors; and
a controller, the controller electrically coupled to the DC power source and the battery, the controller including executable instructions stored in non-transitory memory to:
switch the transistors to adjust a direction of current flow and/or adjust an effective impedance of the DC bus; and
operate the sole DC/DC converter in a buck mode in response to a first operating condition of the DC power source, and to operate the DC/DC converter in a boost mode in response to a second operating condition of the DC power source.
13. The electric power conversion system of claim 12 , wherein the first condition is an electrical load applied to the DC power source being less than an electrical load that provides a maximum power output for present DC power source operating conditions, and wherein the second condition is an electrical load applied to the DC power source being greater than an electrical load that provides a maximum power output for present DC power source operating conditions.
14. The electric power conversion system of claim 12 , further comprising:
additional instructions to adjust an electrical load provided via the sole DC/DC converter to the DC bus responsive to output voltage and current of the DC power source.
15. The electric power conversion system of claim 12 , further comprising additional instructions to operate the sole DC/DC converter in the boost mode in response to a request to provide electric power to an AC grid.
16. The electric power conversion system of claim 15 , further comprising additional instructions to operate the sole DC/DC converter in the buck mode in response to a state of charge of the battery and output current and voltage of the DC power source.
17. A method of electric power conversion, comprising:
operating a sole direct current (DC)/DC converter of a power distribution system for an all iron redox flow battery in a buck mode in response to operating conditions of a photovoltaic array, operating the sole DC/DC converter of the power distribution system in a boost mode in response to operating conditions of the photovoltaic array, the sole DC/DC converter directly electrically coupled to a DC bus, the photovoltaic array directly coupled to the DC bus, the DC bus directly electrically coupled to an inverter; and
switching transistors of the sole DC/DC converter to adjust an electrical impedance provided by the DC bus to maximize an electrical output of the photovoltaic array;
wherein the all iron redox flow battery includes a plating electrolyte and a redox electrolyte, the all iron redox flow battery adapted to permit the plating electrolyte and the redox electrolyte to comprise different molar concentrations of a predetermined salt.
18. The method of claim 17 , further comprising:
operating the DC/DC converter in the buck mode or the boost mode in further response to output efficiency of the photovoltaic array; and
operating the DC/DC converter in the buck mode or the boost mode in response to an operating state of the all iron redox flow battery.
19. The method of claim 17 , further comprising transferring electrical charge from the photovoltaic array to the all iron redox flow battery via the sole DC/DC converter, the all iron redox flow battery electrically isolated from the photovoltaic array via a transformer that includes a primary coil and a secondary coil.
20. The method of claim 17 , further comprising operating the sole DC/DC converter in the buck mode in response to a state of battery charge.