Zhixin Miao, Alexander Domijan, and Lingling Fan
Inverter, DER, unbalance, negative sequence compensation
The objective of this paper is to present an analysis of negative se- quence compensation-based unbalance control in distributed energy resources (DERs) interfacing inverters for unbalance in distribution systems and microgrids. The purpose of the control scheme is to preserve the important loads from subjecting to unbalanced grid conditions. Appropriate transformer connections can prevent zero sequence currents entering into loads. Hence, negative sequence cur- rents or voltages are the main concern. To achieve the purpose, the interfacing inverters will generate unbalanced three-phase voltages accordingly or provide negative sequence compensation. The major contribution of this paper is two-fold: (i) a quantitative analysis is presented to show the level of the required negative sequence compensation; and (ii) the conflicting nature of keeping a balanced voltage and keeping output power ripple free is presented. Impact of the negative sequence compensation on ripples of the output power is investigated. Time-domain simulation results by Matlab/Simulink are given to verify the analysis results and the effectiveness of the control scheme.
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