Research On Control Strategy Of Photovoltaic Grid Connected Inverter With Selective Harmonic Compensation

The grid-connected inverters with the function of active power filter(APF)have been popularized due to their high efficiency and low cost.When the output power of the PV array is small,the residual capacity of the inverter can be used to compensate the harmonics,which makes the system work in the grid and APF state.However,when the load current of the system is large,the command current value of the grid connected photovoltaic system and the APF is more than the current limit value of the power tube,resulting in the system capacity exceeding the limit.Therefore,This paper presents a selective harmonic compensation of photovoltaic(pv)grid inverter control strategy,carry on the theoretical analysis and experimental research.In this paper,the topology and working principle of the clamped three level inverter based on the photovoltaic active power grid and the unified control of APF are analyzed,and the corresponding mathematical model is established.Based on the judgment of the traditional small sector of the SVPWM algorithm,the medium vector is introduced,which reduces the time of small sector judgment and improves the real-time performance of the algorithm.Aiming at the traditional SVPWM control algorithm,the DC neutral point potential migration mechanism is easily analyzed.By introducing time action factor to adjust the action time of positive and negative vectors,the neutral point potential migration is suppressed.Based on the limitations of the specific subharmonic detection algorithm,this paper uses the specific subharmonic detection algorithm.This paper focuses on the APF and PV unified control exist capacity problems,analysis of shortcomings of traditional proportional current limiting mode,this paper put forward a kind of selective harmonic compensation of photovoltaic grid connected inverter control strategy of selective compensation for greater risk on harmonics,rounding of low content and harmonic compensation,and reasonably reduce synthesis of instruction current,the system of limited capacity to obtain the reasonable use.In order to achieve the purpose of unified control of photovoltaic grid connected and APF,the current and voltage double closed loop control strategy is adopted in this paper,and PR controller is adopted to achieve no static error control for fundamental and all harmonics.Finally,the results verify the effectiveness of the strategy.