Control Research And Implementation Of 10kW Single-phase Photovoltaic Energy Storage Bidirectional Inverter

The single-phase photovoltaic energy storage inverter is composed of energy storage batteries,a MPPT controller,bidirectional DC/DC converter for battery charging and discharging,a grid-side inverter module and other components.The grid side inverter is a key component of the battery energy storage system,used to control the charging and discharging process of the battery,perform AC/DC conversion,and directly supply power to AC loads when off grid.It can be seen that the grid side inverter can operate both on grid and off grid,playing an important role in the energy storage system.However,using traditional control inverters is difficult to meet the requirements of the power grid and load,so currently studying the control strategy of grid side inverters is of practical significance.In this paper,a series of research have been carried out on the bidirectional AC/DC converter,which is a grid side inverter module in a 10kW single-phase photovoltaic energy storage inverter.Aiming at the time delay oscillations generated by the grid side bidirectional inverter module using an independent voltage controller during the switching process of rectification and inverter in grid connection mode,a unified control method for rectification and inverter of the grid side inverter is studied.In this method,the power flow direction on the grid side can be controlled based on the positive and negative polarity of the output signal of the external voltage regulator.In order to achieve AC current zero static error tracking of a given current signal formed by multiplying the output of the bus voltage outer loop regulator and the phase-ocked loop signal,the current inner loop uses Quasi-Proportional Resonance(QPR).In order to design the current inner loop QPR control parameters,the modes of the bidirectional AC/DC converter under rectifier and inverter operation are analyzed and a mathematical model is established,Based on the power balance theory,the open loop transfer function of the rectifier operation mode is derived.On this basis,the control parameters of the voltage outer loop PI controller are designed,which are suitable for the inverter operation mode.Therefore,the unified control of the bidirectional AC/DC converter’s rectification and grid connected inverter is realized.In this paper,when the grid side inverter operates in the off-grid mode,a dual closedloop control strategy combining the voltage outer loop and the current inner loop is adopted.Aiming at the static error phenomenon of traditional voltage outer loop PI controller during off-grid operation,this paper studies the control strategy of using QPR controller for voltage outer loop and PI controller for current inner loop when grid side inverter is off-grid operation,and presents the tuning method of control parameters.In order to improve the dynamic response speed,the first order linear active disturbance rejection control(LADRC)method for the voltage outer loop of the grid side inverter during off grid operation was studied;Aiming at the application of grid side inverters with rectifier loads when operating off the grid,a composite control strategy combining repetitive control(RC)and PI regulator is adopted.Based on this,a composite control strategy combining RC and first order LADRC is proposed.Through simulation and comparison,the output voltage and current waveforms are superior to the composite control combining RC and PI.This paper also studies a single-phase PQ control mode,which does not require the construction of a three-phase system and the addition of a phase locked loop.It studies the control strategy for switching between on and off grid operations,thereby achieving stable control of two operating states.This thesis uses the TMS320F28035 control chip from TI Corporation to build a 10kW single-phase photovoltaic energy storage inverter prototype.The hardware design of the 10kW single-phase photovoltaic energy storage bidirectional inverter,including the control circuit,sampling circuit,and power circuit,is carried out.Aiming at the performance indicators of the grid side inverter prototype,the selection of main components and the design method of inductance and capacitance parameters are given.The unified control method for gridconnected and rectified operation of the grid-side bidirectional inverter module and the smooth switching control experiment for grid-connected and off-grid inverter operation have been implemented,verifying the rationality of the theoretical research and the correctness of the design in this paper.