Vector Control of the Single-Phase Inverter Based on the Extended and Virtual Circuits

A vector control based on the extended equivalent circuit and virtual circuits is proposed for the single-phase inverter.By the extended circuit,the other two phase voltages can be extended by the output voltage of the single-phase inverter so as to construct the voltage vector.The voltage outer-loop is to control the voltage vector in dq coordinate system,and the output voltage can track the target value without deviation in steady state.By designing the virtual circuit,the voltage inner-loop can achieve approximate decoupling and improve the dynamic response under the changeable load.Compared with the traditional dual closed-loop control,the proposed dual closed-loop control scheme only needs to detect and control the voltage without the current.It not only can achieve good control effect,but also reduce the complexity of the hardware.Finally,the simulation and experimental results show that the single-phase inverter has good static and dynamic characteristics regardless of stable load or changeable load.

An Insight into the Second-Harmonic Current Reduction Control Strategies in Two-Stage Converters

Due to the components at twice the fundamental frequency of output voltage in the instantaneous output power of a two-stage single-phase inverter(TSI),the second harmonic current(SHC)is generated in the frontend dc-dc converter(FDC).To reduce the SHC,optimizing the control strategy of the FDC is an effective and costless approach.Fromthe view of visual impedance,this paper conducts an intensive study on the SHC reduction strategies.Origin of the SHC is illustrated first.Then,the equivalent circuit models of the FDC under different control strategies are proposed to analyse the SHC propagation characteristic.The derived model can offer a better insight into how the inductor SHC is affected by the control parameters.According to the derived models,a synthesis of different control strategies is presented and the relevant parameters are listed for control design to achieve better suppression effect.The benefits and limitations of these control strategies are also discussed.Based on the proposed equivalent circuit models,several optimization methods are proposed to enhance the effect.A 1500 VA TSI prototype is built and simulated on MATLAB/Simulink,verifying the effectiveness of the proposed optimization methods.This paper is aimed to provide a guideline for the control design and control optimization of the TSIs.