Simulation And Research Of The Photovoltaic Supplied Micro-grid Under Partial Shading

With the continuous expansion of the scale of the power grid,the traditional centralized power generation and long distance transmission of power grid construction mode showed more and more limitations.As a supplement to the large power grid,micro grid emerges as the times require.Micro grid can integrate a large number of distributed new energy power generation,help to solve the problems encountered in the large power grid.Solar energy as a new clean energy,PV micro source as an important part of the micro grid has been the rapid development.But with the rapid development of PV power generation and micro grid,the new problems have emerged: one is the MPPT of the PV array under partical shading,and the two is how to ensure the reliable and stable operation of the micro grid.On the above two issues,to take the research methods of this paper,the problem can be solved one by one.The first part is the MPPT problem of the PV array under partical shading.Because under partial shading,the P-U characteristic curve of PV array will be multi peak phenomenon,using the traditional MPPT method will fall into the local maximum power point,and this problem is difficult to solve.Based on the above problems,this paper proposes a MPPT algorithm with photovoltaic prediction: PV prediction+ Actual MPPT.Comparison of three kinds of modeling methods for photovoltaic cells,as the kinematic modeling method can be well to express the characteristics of photovoltaic cells,less computation,error meeting engineering,so the photovoltaic prediction model use the kinematic model,and Using particle swarm optimization algorithm predict the maximum power.The using of PV prediction can probably know the MPP working point of the actual position of the PV array.As the working position of the PV array MPP has been probably known,when the actual MPPT,let the work point begin to work near the predicted value,then the P&O can quickly find out the actual MPP.This would solve the problem of MPPT under partical shading.The second part is how to ensure the reliable and stable operation of the micro grid Due to the adoption of Droop control strategy;it can realize the control of "plug and play" and "equivalence".So Droop control strategy is widely used in micro network control.But due to the traditional Droop control has the shortcomings of droopcoefficient setting small,dynamic response speed slow,and increasing droop coefficient can improve the dynamic response,but frequency and voltage amplitude will greatly deviate from the set value,which cause the system unstable.This paper presents the droop control strategy of piecewise hysteresis,instead of one sag curve with three sag curve,using this method can not only solve the problem of dynamic response but also can increase the power output range and keep the output of the voltage amplitude and frequency not changing too much.Finally,using the above method establish the PV power generation model under partical shading and micro grid model in MATLAB/Simulink,Through the separate operation and the combined operation models,verify the correctness and feasibility of the proposed approach.Through a separate operation and the combined operation of these models,verify the correctness and feasibility of the proposed method.