Research on Novel Parallel Current Sharing Control Technique of the Stand-Alone Photovoltaic Inverter

Stand- alone photovoltaic systems have solved power supply in the many remote areas. Inverter is the key component of photovoltaic system. By paralleling several mid/low-power inverter units to compose a large power supply system, both the capability and the reliability of power supply system can be enhanced. The circumfluence among parallel inverter in PV is the key reason for preventing the parallel operating system from running normally. In order to share the load and restrain circumfluence, it is described that a digital current sharing control technique for inverter parallel operation in detail in this paper. The parallel system structure of the stand-alone photovoltaic inverter on distributed-logical-control is presented. Based on the analysis of circumfluence of paralleled system, characteristic of the power regulation, a novel digital power detection technique is deduced. With measuring and analyzing the instantaneous average current of all inverters and the output current of each inverter, both of the current components are used to control and regulate the amplitude and the phase of the output voltage. In this way, the control of current sharing in the inverter paralleling system is realized. The proposed control technique has been verified the good characteristic of restraining circumfluence by the results of the experiment. The control strategy has advantages of brevity, high practicality.