Systems and methods for control of a medium voltage direct current solar plant

A method for controlling a solar power generation system, the solar power generation system including at least one direct current (DC) to DC converter, at least one inverter, and an energy storage system, the at least one DC to DC converter electrically coupled to a medium voltage DC (MVDC) bus, said method comprising:

• converting, by the at least one DC to DC converter, low voltage DC (LVDC) power received from at least one photovoltaic (PV) array to MVDC power;
• determining, by the at least one DC to DC converter, a voltage of the MVDC bus;
• in response to the determined voltage of the MVDC bus exceeding a threshold output voltage, transmitting, by the at least one DC to DC converter, the MVDC power via the MVDC bus at a DC power level less than a rated DC output power level of the at least one DC to DC converter;
• receiving, by the inverter, the MVDC power from the at least one DC to DC converter;
• converting, by the inverter, the MVDC power to medium voltage AC (MVAC) power;
• determining, by the inverter, the voltage of the received MVDC power;
• in response to the determined voltage of the received MVDC power being less than a threshold input voltage, transmitting, by the inverter, the MVAC power at an AC power level less than a rated AC output power level of the inverter;
• operating the energy storage system at a maximum storage setpoint to store MVDC power received from said at least one DC to DC converter when a voltage of the MVDC bus is greater than the threshold output voltage of said at least one DC to DC converter;
• operating the energy storage system at a maximum transmission setpoint to transmit MVDC power to said at least one inverter when the voltage of the MVDC bus is less than the threshold input voltage of said at least one inverter;
• and
• operating the energy storage system at a variable setpoint that varies between the maximum storage setpoint and the maximum transmission setpoint when the voltage of the MVDC bus is between the threshold output voltage of said at least one DC to DC converter and the threshold input voltage of said at least one inverter.

A solar power distribution system comprising:

• at least one direct current (DC) to DC converter electrically coupled to a medium voltage DC (MVDC) bus, said DC to DC converter configured to:
• convert low voltage DC (LVDC) power received from at least one photovoltaic (PV) array to MVDC power;
• determine a voltage of the MVDC bus;
• and
• in response to the determined voltage of the MVDC bus exceeding a threshold output voltage, transmit the MVDC power via the MVDC bus at a DC power level less than a rated DC output power level of said at least one DC to DC converter;
• at least one inverter configured to:
• receive the MVDC power from the at least one DC to DC converter;
• convert the MVDC power to medium voltage AC (MVAC) power;
• determine the voltage of the received MVDC power;
• and
• in response to the determined voltage of the MVDC power being less than a threshold input voltage, transmit the MVAC power at an AC power level less than a rated AC output power level of said at least one inverter;
• and
• an energy storage system configured to:
• operate at a maximum storage setpoint to store MVDC power received from said at least one DC to DC converter when a voltage of the MVDC bus is greater than the threshold output voltage of said at least one DC to DC converter;
• operate at a maximum transmission setpoint to transmit MVDC power to said at least one inverter when the voltage of the MVDC bus is less than the threshold input voltage of said at least one inverter;
• and
• operate at a variable setpoint that varies between the maximum storage setpoint and the maximum transmission setpoint when the voltage of the MVDC bus is between the threshold output voltage of said at least one DC to DC converter and the threshold input voltage of said at least one inverter.