Research On Grid-connected Control Strategy Of Inverter Under Non-ideal Condition Of Grid Voltage

With the increase of investment in new energy generation in China,there are many phenomena of wind abandoning and light abandoning,and the control strategy of grid-connected inverter,as a hub device connecting power grid and power electronic devices,will directly affect the quality of grid-connected system power generation.Due to the dynamic change of the power grid,the imbalance of power grid voltage,harmonic distortion and other non-ideal conditions will have a negative impact on the output performance of the grid-connected inverter,thus affecting the output current quality of the grid-connected inverter,and thus affecting the stability of the whole grid-connected system.Therefore,it is necessary to study the control strategy of grid-connected inverter under the condition of non-ideal grid voltage.Firstly,established without considering delay and consider delay the LCL filter grid inverter,the mathematical model and the three-phase grid inverter according to the characteristics of digital control,discussed all kinds of digital SPWM modulation method and its digital control and the reason of the digital time delay,and analyses the digital delay link for inverter modeling process,the influence of digital control inverter performance for later analysis and digital delay effect on the performance of the system to provide mathematical basis.Secondly,in view of the grid voltage unbalance and distortion under the condition of grid synchronization information detection,digital sampling,PWM output,such as time delay problem,research a kind of duty ratio and zero pole compensation based on predictive control and the positive and negative sequence component complex filter comprehensive improvement methods,so as to improve the dynamic performance of grid inverter,and USES the proportion of quasi resonant controller in parallel manner to eliminate the grid voltage harmonic distortion caused by the grid current.At the same time,on the basis of the mathematical model of the three-phase grid-connected inverter,the value range of the feedback coefficient of the inner loop capacitance current is deduced to make the system stable,the value range is compared and analyzed,and the influence of different feedback coefficients of the capacitance current on the stability of the system is analyzed by the Byrd diagram.Finally,the three-phase grid-connected inverter system model is simulated,and the output characteristics of the grid-connected inverter under unbalanced and distorted grid voltage conditions are analyzed.The results show that the proposed improved control method is better than traditional control It has higher dynamic characteristics,and the designed capacitor current feedback coefficient value range still has better stability under the condition of non-ideal grid voltage.