Research On Current Superposition Type Additional Controller And Its Control Strategy For Photovoltaic Power Generation System

Distributed energy has the characteristics of clean and efficient,flexible installation,and can cooperate with energy storage devices to improve the reliability of power supply of distribution network.However,the access of a large number of distributed energy to distribution network not only changes the topology of distribution network,but also leads to the two-way flow of power.At the same time,it also makes the dynamic characteristics of the distribution network more complex,which brings many challenges to the planning and operation optimization of the distribution network.Among them,the optimization of distribution network dynamic characteristics has become a new research hotspot.Based on the above background,this paper aims to optimize the dynamic characteristics of distributed energy distribution network,focusing on the current superposition type additional controller and its control strategy.The specific contents are as follows:Firstly,the paper takes the photovoltaic power generation system as the research object,introduces the topological structure of the photovoltaic power generation system,the output characteristics of the photovoltaic cell,MPPT technology and the control strategy of the photovoltaic inverter in detail,and establishes the corresponding mathematical model.On this basis,the PSCAD simulation software was used to build a distribution network model including photovoltaic power generation system,and the bad dynamic characteristics of the distribution network under different disturbances were simulated and analyzed,which laid a foundation for the subsequent optimization of the dynamic characteristics of the distribution network.Secondly,an additional control strategy based on current superposition control is proposed to solve the poor dynamic problem of distribution network.The input signal of the control strategy is selected as the active and reactive power of the inverter.Considering that the coupling voltage signal will change the output phase of the phase-locked loop,the output signal of the additional control is designed as the current signal,and the control strategy will not change the internal control structure of the converter control unit,so it is very convenient to apply.In this paper,the components and design parameters of the additional control are introduced in detail,and the simulation comparison of the distribution network system with or without additional control is carried out through a numerical example,and the effectiveness of the proposed additional control method is verified.Finally,according to the proposed additional control strategy,a current superposition additional controller is designed,and the current source output unit of the additional controller is emphatically designed.The unit is synthesized from sine wave,triangle wave generator circuit,comparator,drive circuit,inverter circuit and filter circuit,the main function is to attach additional controller output control signal into current signal,the current signal is coupled to the input current of converter control unit,back to the way to improve the control performance of the control unit.In this paper,the circuit principle and parameter design of each part of the output current source unit are introduced in detail,and the performance of the output current source unit designed in this paper is verified by experiments.