Power system and method

A power system for supplying AC output power to at least one desired AC load, the system comprising:

• an internal DC bus configured to electric transfer within the system;
• an inverter unit coupled to the internal DC bus, which inverter unit is configured to invert DC power to AC power to supply the AC output power to the inverter connected AC load;
• an energy measurement device coupled to the internal DC bus, wherein the energy measurement device is configured to measure values of electrical currents and/or voltages within the system;
• and
• a controller configured to take measured values from the energy measurement device as an input for determining an AC output power demand of the AC load connected to the inverter unit,
• wherein the controller is further configured to control electric power consumption of the inverter unit based on the AC output power demand,
• wherein the controller is further configured to control the inverter unit to operate at least in a low-level mode and in a high-level mode, and
• wherein the inverter unit comprises a low-level inverter configured to invert the DC power to the AC power in the low-level mode, which low-level mode is configured to be used when the AC output power demand is below threshold value, and the inverter unit further comprises a high-level inverter configured to invert the DC power to the AC power in the high-level mode, which high-level mode is configured to be used when the AC output power demand is above the threshold value, and which low-level and high-level inverter are separate inverters.

A computer program product on a non-transitory media for supplying AC output power to at least one desired AC load, comprising instructions configured to, when executed on at least one processor, cause the at least one processor to perform method steps, the method steps comprising:

• receiving measured values of electrical currents and/or voltages of a power system from an energy measurement device as an input;
• determining an AC output power demand of an AC load connected to an inverter unit;
• controlling an inverter unit in inverting of DC power received via an internal DC bus to AC power to supply the AC output power, the internal DC bus is configured to electric transfer within the system;
• controlling a switching element;
• controlling electric power consumption of the inverter unit based on the AC output power demand;
• and
• selecting of AC output mode of the inverter unit based on the AC output power demand, wherein the selecting of the AC output mode is made between a low-level mode and a high-level mode on the basis of a threshold value, wherein the low-level mode is selected when the AC output power demand is below the threshold value and the high-level mode is selected when the AC output power demand is above the threshold value;
• wherein the switching element accomplishes a step of connecting the low-level inverter on the AC output line and disconnecting the high-level inverter from the AC output line, when selecting the low-level mode, which low-level inverter and high-level inverter are separate inverters, and which switching element accomplishes a step of connecting the high-level inverter on the AC output line and disconnecting the low-level inverter from the AC output line, when selecting the high-level mode.