Researchoncontrol Strategies Of Distributed Photovoltaic Power Generations With Battery Energy Storage Systems

To solve the problems of energy shortage and environmental pollution, each countries pay more attention to new energy distributed power generation. New energy power generation has become the key point to resolve this contradiction. Adding storage device into DG system can help to improve the efficiency. The system can not only be able to provide uninterrupted power supply for the important loads, but also permeate better into the grid. Reasonable and effective control strategy for DG is the key technology to combine DGs with grid, and it has become a hot research spot in recent years.Firstly, this paper describes the characteristics of photovoltaic power generation systems and battery storage system, introduces the inverter mathematical model, and also designs the parameters. After introducing the control theory of PQ control and droop control, the parameters of the two controllers are designed and their Simulink model are respectively built to validation.Secondly, PV-battery power system is studied.It proposes two control strategies for the bi-directional DC/DC converter. By using the two strategies respectively, under simulated changing light intensity, Simulink results show that using constant DC bus volatage outer loop current inner loop control strategy can guarantee the stability of the inverter output. Based on this, the simulation example of the PV-battery system is completed, it verifies that by battery charging and discharging control, the system can smooth the output fluctuations of the PV cells and ensures DC bus voltage is stabilized in pre-set value.Again, it improves droop control algorithm, by introducting the line voltage drop into drop control, and compares the resule of reactive power allocation before and after correction, the result shows its validity. Meanwhile it also studies voltage-frequency recovery strategy, which can effectively suppress induced voltage and frequency deviation.Finally, with the PV-battery system access into micro-grid, it studies its operational characteristics and control strategies. Aiming at smooth switching method between island and grid-connected modes, it proposes two kinds of control strategies, and the models based on Simulink are respectively given and demonstrated that the two control methods can realize smooth switching between island and grid-connected modes. In order to ensure the quality of the important load power, in island mode,when DGs cannot provide enough power for load and control method cannot ensure a smooth transition, the system needs to cutoff some loads to ensure the stability of system. Based on this,this paper studies control method to cut off secondary loads, two separate removal of loads can effectively reduce the transient oscillations, and ensure switching more smoothly.