Uninterruptible power supply with a dual gain voltage regulator controlling an inverter output voltage based on active and reactive components of current

A method of controlling an output voltage of an inverter of an uninterruptible power supply (UPS) system, the UPS system including an output transformer having a primary side coupled to an output of the inverter and a secondary side coupled to an output of the UPS system, a controller that monitors a primary side voltage and load current flowing through the output of the UPS system, the method comprising:

• a. decomposing with the controller the load current into an active and reactive components and using them as approximations for IT—active and IT—reactive;
• b. determining with the controller a voltage drop across the output transformer for a steady state mode of the UPS system (Vreg2) and also for a continuous mode of the UPS system (Vreg1), wherein Vreg1 and Vreg2 are determined by
• Vreg1=Gactive*IT—active+Greactive(low)*IT—reactive
• Vreg2=Gactive*IT—active+Greactive(high)*IT—reactive
• where Greactive(low) is less than 300 and Greactive(high) is greater than 1,000;
• and
• c. in each of the two modes, determining with the controller a voltage drop across the output transformer (VTVR) to use in determining a desired inverter output voltage of the inverter by
• VTVR=Vreg1+ΔVT
• where ΔVT is zero when the UPS system is not in the steady state mode and ΔVT=Vreg2−Vreg1 when the UPS system is in the steady state mode;
• and
• d. determining with the controller a desired inverter output voltage based on a nominal output voltage of the UPS system and VTVR and controlling an actual inverter output voltage based on the desired inverter output voltage and the monitored primary side voltage;