An improved control method for UPS parallel connection average current

Abstract

The invention relates to UPS parallel connection equal current control method, the real power controller and the idle power controller are adopted to control the UPS contravariant reference voltage, inductance current direct component is added into the UPS contravariant reference voltage, inductance current direct component of the other UPS in system can be obtained by CAN bus, after DSP calculation of every UPS, the average value of the parallel connection system inductance current direct component is calculated to as the system direct current component, then the given value of the direct current is compared with the direct current component of the UPS inductance current to obtain the difference of the inductance current, the difference passes PI adjustor to obtain the regulated quantity needed by the contravariant reference voltage, and the regulated quantity is used to control the UPS output voltage. So the effective control of the inductance current direct component can be realized, and the direct loop current of UPSs can be eliminated, the flow equalization property and stability of integral UPS parallel connection system can be improved.

Description

technical field [0001] The invention relates to a current equalization control method for UPSs running in parallel. Background technique [0002] Uninterruptible power supply (UPS) is more and more widely used in the power supply of important loads and power failure protection. With the continuous improvement of users' requirements on power supply reliability and capacity, parallel operation of UPS is a good choice. The parallel UPS system has the advantages of redundancy, scalability, high reliability and easy maintenance. [0003] The key to UPS parallel operation is the distribution of load current. To make the load evenly distributed between each UPS, it is necessary to make the amplitude, phase and frequency of the UPS output voltage equal at any time, otherwise a circulating current will occur. Uneven load current distribution will cause individual UPS overload, and the circulating current will reduce the efficiency and reliability of the entire parallel system. [0...

AI Technical Summary

Problems solved by technology

The droop control method does not require a power control bus or an average current bus. Each UPS adjusts the amplitude and frequency of the output voltage by detecting its own output power. However, for high-power UPSs, current sharing control is very important, but logic switching And fault protection also determines whether the entire system can run stably, which requires a single UPS to know the status of other UPSs in the parallel system, so there must be a signal bus, and drooping method is rarely used for current sharing control in actual products

[0005] Instantaneous average current control can get a good current sharing effect, but because the average current bus is generally an analog signal, it is easily disturbed and affects the reliability of the parallel UPS system, so anti-interference processing must be carried out and the distance between each machine not very far

[0006] Active power and reactive power sharing current control is based on the method of power control, that is, the active power controller and reactive power controller are used to control the UPS inverter reference voltage, as long as the output active power and reactive power of each UPS are kept exactly the same , it can realize the equal sharing control of the load current, but for the DC component of the output circulating current, the active power and reactive power equal sharing control cannot eliminate the direct current component of the circulating current

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