1.Key Laboratory of Measurement and Control of CSE Ministry of Education Southeast University Nanjing 210096 China; 2.Taizhou University Taizhou 225300 China
Abstract：Because the high-frequency switching harmonics of the active power filter (APF) are generally not included in the closed current control loop,they will have the characteristics of voltage source,which may cause the high-frequency harmonic circular currents in the modules of multi-module APF.These harmonic circular currents will increase the power loss and reduce the system stability and control precision.To solve above problems,through building the circular current mathematical model,the formation mechanism of the circular current and its influences are analyzed in detail.Furthermore,the influences of the output filters (OF) on the circular currents are researched.Finally,a coordinated control strategy to suppress the circular currents is introduced.The theoretical analysis and experimental results show that:Firstly,the primary cause of the circular currents is the asynchronization of SPWM carrier waves;Secondly,the circular currents do not flow into the power system;thirdly,the OF can inhibit the non-circular part of the high-frequency harmonic currents,but it is ineffective to the circular part and will undermine the system stability;Finally,the circular currents can be inhibited effectively by the coordinated control method proposed in this paper.
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2016, Vol. 31 
