Research On The Photovoltaic Grid-connected Power Conditioner System

Photovoltaic power generation technology is an effective way to use solar energy whichis clean energy and higher value. Therefore, researching grid-connected photovoltaic powerconditioning system is crucial. The theoretical basis of PVPC is the unity between gridinverter and active power filter topologies existing on the working principle and controlstrategy. The two functions can be achieved by controlling inverter devices basing on theoriginal function of the grid, it can also achieve reactive power compensation and harmonicsuppression function. Expand research on PVPC, the main contents as follows:Firstly, the core part of achieving reactive power compensation and harmonicsuppression is accurately detecting the load side harmonic and reactive current in real-time,while in the photovoltaic power generation. By analyzing the detection method based onaverage active theory, this detection method requires a low-pass filter to extract the DCcomponent. To solve the delay of this method, an improved method which regards theharmonic and reactive current as the feedback signal is raised. Introduce PID feedback loopregulation to speed up the detection speed. Through simulation analysis, validating theimproved detection methods are more rapid.Secondly, in the analysis of PVPC’s control objectives and strategy, the control systemcomprises two sides: on one hand, the MPPT control of the PV array, climbing method usedhere to ensure maximum active power output of the photovoltaic array; on the other hand,analyzing the dual-loop control strategy of the outer voltage and inner current, the currentinner loop control technology apply quasi-PR to track the command current which includingactive current from regulator’s control and harmonic and reactive current, to suppressharmonic, output and active power, detecting island based on reactive power adjusting.Lastly, by building simulation models in Matlab/Simulink, it can verify the feasibilityof PVPC. The results of simulation show that the MPPT control and the dual-loop controlstrategy are right, the photovoltaic grid power conditioning system can achieve grid andreactive power compensation and harmonic suppression. And adjust the active and reactivepower changes in light intensity and extent of changes in reactive power compensation. At thesame time, by the degree of the control of reactive power compensation, it can detect theislanding rapidly.