Research Of Control Technology In Single Phase Parallel Inverter With Different Capacityes

With the increasing demand for energy， New energy power system-relatedtechnology has got more and more attention. The distributed power system has becomeone of the key research because of its many desirable features such as expandability,modularity, redundancy, parallel inverters control is the kernel technique of thedistributed power system. According to the advantages and disadvantages of existingparallel control structures, using a distributed parallel structure to increase the capacityand reliability of power supply. In order to improve system’s output power quality, suchas the THD of output voltage, restraining circulating current, distributing the loadcurrent. In this paper, several measures based on main circuit and control system areproposed to improve the output power quality, which are tested and verified in theMATLAB.On the topology selection of the parallel system, In consideration of the harmonicof the inverter output voltage at switching frequency can’t be suppressed by closed-loopcontrol, while it’s only suppressed by the filter of the main circuit. So having thecharacteristics of higher attenuation and higher output impedance, LCL filter isintroduced to as the main circuit filter. Through analyzing the filtering performance andthe filter element parameter characteristics, LCL filter parameter design method isgiven.Contra the problem that traditional inner-loop current regulator tracks powerfrequency instruction with poor accuracy, quasi proportional resonant controller isproposed to improve performance of current regulator. For resonance in the specificfrequency, quasi resonant controller can obtain high gain at power frequency, and trackspower frequency instruction more accurately. In addition, with regard to the differentcapacity power source inverters in parallel, a dual-outer-loop distributed control strategyis proposed. It can achieve the goal that the required modules in parallel system dependon the value of load current and all the parallel modules share load current in proportionto their own capacities，in the same time, restrain circulating current and realize theredundancy in parallel.Contra the problem that load disturbance uncertain, robust control based on μsynthesis used in outer-loop is proposed. robust synthesis problem caused by theinductive or nonlinear load perturbations in parallel system is first transformed into a minimization problem of the structured singular values so that a high-order andcontinuous μ synthesis robust controller can be solved by DK Iterative algorithm afterdetermining the range of load disturbance. In order to make μ synthesis robust controllereasy in implementation of practical engineering, the optimal Hankel-normapproximation are given in the paper which is used to reduce the order of μ synthesisrobust controller, and verify the robustness performance of the low-order controller.Simulation platform consists of three parallel inverter modules is build in theMATLAB/Simulink, to verify the feasibility of proposed control strategy in the paper.