Primary and Secondary Droop Control Method for Islanded Microgrid with Voltage Regulation and Current Sharing

Abstract

This paper presents primary and secondary control of islanded microgrid. In conventional primary droop control, there is a problem of poor voltage regulation of microgrid. The drawback of conventional primary droop control is improved by voltage shifting based primary control. Voltage shifting based primary control is not completely satisfied by the voltage regulation of microgrid. Also, there is current sharing problem in both types of primary control. So, in secondary control, both current sharing and voltage regulation are achieved by slope adjusting and voltage shifting simultaneously. In this secondary control method, average value of current, voltage, and droop resistance of two neighboring converters is calculated then controlled by additional layer of distributed secondary control over both primary controls. By adjusting droop coefficient of different converters making same value of output impedance of converter, current sharing and voltage regulation are achieved. Also, in transient state, current sharing is achieved by using this secondary control technique. The performance of proposed microgrid is verified by MATLAB simulation.