Uninterruptible power supply with a dual gain voltage regulator controlling an inverter output voltage based on active and reactive components of current
View Patent ↗An uninterruptible power supply (UPS) system has an inverter having an output coupled to a primary side of an output transformer. The UPS system has a controller having a dual gain voltage regulator for controlling the output voltage of the inverter of a UPS system that uses active and reactive current components of a load current flowing out an output of the UPS system.
1. 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 active and reactive components and using them as approximations for I T — active and I T — reactive ;
b. determining with the controller a voltage drop across the output transformer for a steady state mode of the UPS system (V reg2 ) and also for a continuous mode of the UPS system (V reg1 ), wherein V reg1 and V reg2 are determined by
V reg1 =G active *I T — active +G reactive(low) *I T — reactive
V reg2 =G active *I T — active +G reactive(high) *I T — reactive
where V reg1 is the voltage drop across the output transformer for a continuous mode of the UPS system, V reg2 is the voltage drop across the output transformer for a steady state mode of the UPS system, G reactive(low) is a gain less than 300, G reactive(high) is a pain greater than 1,000, I T — active is the active component of the load current, and I T — reactive is the reactive component of the load current, and
c. in each of the two modes, determining with the controller a voltage drop across the output transformer (V TVR ) to use in determining a desired inverter output voltage of the inverter by
V TVR =V reg1 +ΔV T
where V TVR is the voltage drop across the output transformer to use in determining a desired inverter output voltage, ΔV T is zero when the UPS system is not in the steady state mode and ΔV T =V reg2 −V reg1 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 V TVR and controlling an actual inverter output voltage based on the desired inverter output voltage and the monitored primary side voltage.
2. The method of claim 1 , including using a value in the range of 50 to 300 for G reactive(low) and a value in the range of 1,000 to 2,000 for G active in determining V reg1 and using a value in the range of 4,000 to 6,000 for G reactive(high) and a value in the range of 100 to 300 for G active in determining V reg2 .
3. The method of claim 2 including determining V reg1 a plurality of times each line cycle of an AC output voltage of the UPS system and determining V reg2 no more than once per second.
4. The method of claim 3 including determining V reg1 four times each line cycle of the AC output voltage of the UPS system.
5. An uninterruptible power supply (UPS) system, comprising:
a. an inverter having an output coupled to a primary side of an output transformer, the output transformer having a secondary side coupled to an output of the UPS system;
b. a controller configured to monitor a primary side voltage and load current flowing through the output of the UPS system, decompose the load current into an active and reactive components and uses them as approximations for I T — active and I T — reactive ;
c. the controller configured to determine a voltage drop across the output transformer for a steady state mode of the UPS system (V reg2 ) and also for a continuous mode of the UPS system (V reg1 ), wherein V reg1 and V reg2 are determined by
V reg1 =G active *I T — active +G reactive(low) *I T — reactive
V reg2 =G active *I T — active +G reactive(high) *I T — reactive
where V reg1 is the voltage drop across the output transformer for a continuous mode of the UPS system, V reg2 is the voltage drop across the output transformer for a steady state mode of the UPS system, G reactive(low) is a gain less than 300, G reactive(high) is a gain greater than 1,000, I T — active is the active component of the load current, and I T — reactive is the reactive component of the load current; and
d. in each of the two modes, the controller configured to determine a voltage drop across the output transformer (V TVR ) to use in determining a desired inverter output voltage of the inverter by
V TVR =V reg1 +ΔV T
where V TVR is the voltage drop across the output transformer to use in determining a desired inverter output voltage, ΔV T is zero when the UPS system is not in the steady state mode and ΔV T =V reg2 −V reg1 when the UPS system is in the steady state mode; and
e. the controller configured to determine the desired inverter output voltage based on a nominal output voltage of the UPS system and V TVR and controlling the inverter output voltage based on the determined desired inverter output voltage and the monitored primary side voltage.
6. The UPS system of claim 5 wherein G reactive(low) is in the range of 50 to 300 and the value used for G active in determining V reg1 is in the range of 1,000 to 2,000 and G reactive(high) is in the range of 4,000 to 6,000 and a value used for G active in determining V reg2 is in the range of 100 to 300.
7. The UPS system of claim 6 wherein the controller is configured to determine V reg1 a plurality of times each line cycle of an AC output voltage of the UPS system and determines V reg2 no more than once per second.
8. The UPS system of claim 7 wherein the controller is configured to determine V reg1 four times each line cycle of the AC output voltage of the UPS system.