| As the most important part of AC power supply, inverter is widely used in industrialareas such as UPS and electric locomotive. With the development of moderncommunications technology and advanced manufacturing technology, the capacity andreliability needs of inverter power supply equipment is increasing. The parallel inverter isan important means to achieve high power and high reliability power supply. In this paper,the transient waveform control technology and operational characteristics of parallelinverter was studied. On this basis, stable operation of two parallel40kVA inverters wasachieved.Firstly, the advantages and disadvantages of various inverter waveform controltechniques and parallel technology were introduced and analyzed. Then the most widelyused PID control tectnology and double-loop control technology were researched. Byusing pole placement method, the parameters of the controller were designed. The analysisof the closed-loop system showed that closed-loop control can improve system dynamicperformance and resist load disturbance.On the basis of getting the parallel system model based on output impedence, thecharacteristic of circulating current and circulating power were analyzed. Then theinfluence of output impedence on output power was studied. On the basis of getting thecirculating current transfer function in s domain of the parallel-inverter system, which usesdouble-loop control technology, the influence of controller parameters and main circuitparameters on the fundmental circulating current and the harmonic circulating currentwere analyzed.Finally, experimental studies were carried out on a three-phase combined inverterparallel system. Experimental results showed that inverters using double-loop control havegood dynamic performance and the ability to inhibit load disturbance. Distributed logiccontrol stratege based on active power error of inverters was applied. The circulatingcurrent of parallel system was inhibited, so parallel system can operate stablely. |
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