Improvement Of Grid-Connected Photovoltaic Simulation Technology Based On PSASP_UPI And Research On Control Strategy Under Unbalanced Power Grid

With the increase grid-connected PV capacity,more electric electronic components are connected to the power grid,which puts forward higher requirements of transient stability simulation of PV grid.On the one hand,it is necessary to consider the complexity power electronic components and control systems.On the other hand,size of the power grid must be considered.To solve the problem that current simulation software can not meet the precision of photovoltaic modeling and the scale of the power grid at the same time,based on PSASP and MATLAB,this paper focuses on the joint simulation method of PSASP_UPI.A lot of simulation analysis is made from the application field of software,data characteristics,and interface technology and so on.In view of the problem that PSASP can not control the UP's step when simulating,a hybrid step simulation method based on improved UP is proposed in this paper.The photovoltaic grid connected model is compiled into C code through Simulink Coder and embedded to UP.The UP is improved in VC to calculate one hundred times step-by-step every time it receiving PSASP's calculations at one time,saving each calculation result and passing the last calculation to the PSASP at the next time.The simulation example of CEPRI 36 nodes grid connected photovoltaic model built in PSASP shows that the improved UP hybrid step simulation method is more accurate and feasible compared with the fixed step size simulation method.In order to solve the problem of PV inverter control under unbalanced power grid that smaller power fluctuations and Less current harmonics can't be meet at the same time,a coordination control strategy of inverter is proposed considering current limit.First,the output characteristics of the inverter under unbalanced power grid are analyzed,and variables affecting the active power output,reactive power output,and current harmonics of the photovoltaic system is weighted into k and ?.Then,k and ? are optimized with the optimization of minimizing active and reactive fluctuations,and the constraints of current harmonic distortion factor and current Limitation.Next,the correctness of the unbalanced fault control strategy is verified MATLAB/Simulink model.Finally,PV model with improved control strategy is incorporated into the CEPRI 36 nodes system based on PSASP_UPI to prove its validity.