光储微电网混合储能系统的控制策略及开关优化

传统光储微电网混合储能系统控制策略将蓄电池视为容量无限大的理想元件，而实际上蓄电池容量有限，当蓄电池剩余电量达到阈值无法正常工作时传统控制策略将不适用。在二阶低通滤波法的基础上提出一种光储微电网混合储能系统的新型控制策略，同时考虑超级电容与蓄电池的剩余电量，根据储能元件的荷电状态调整储能元件输出电流参考值，维持储能元件剩余电量，但在极端天气情况下，仍需与储能元件保护开关相配合。由于采用传统储能元件保护开关的储能系统需独立的充放电电路，存在成本较高、充放电不连续等问题，因此，对储能元件的保护开关进行了改进，利用开关与二极管并联使其具有4种工作状态，在储能元件剩余电量达到阈值时，可自动恢复电量，降低了成本，提高了并网输出电能质量。最后结合新型控制策略与改进的保护开关，提出整体的混合储能系统控制方案，并用 Matlab／Simulink 对其进行仿真验证，结果证明了所提方法的正确性与可行性。

Control strategy and protection switch optimization of hybrid energy storage system for PV-storage microgrid system

In the conventional control strategy of the PV-storage micro-grid hybrid energy storage system (HESS), battery is regarded as an ideal element which has infinite capacity. However, the battery capacity is limited and the conventional control strategy is no longer suitable when the threshold of battery state-of-charge (SOC) is reached and can not work properly. Thus, we proposed a new control strategy for the PV-storage micro-grid HESS based on the second-order low-pass filtering method. This strategy takes the SOC of super-capacitor and battery into account, adjusts the reference value of output current of energy storage element and maintains the SOC of storage element. But in extreme weather conditions, the strategy still needs to cooperate with the protection switch of energy storage element. Furthermore, the HESS using conventional protection switch of energy storage element needs separate charging and discharging circuits, which leads to some problems such as high cost, discontinuous of charge and discharge, etc. So the protection switch of energy storage elements was improved in this paper, which has four working states based on the shunt of switch and diode. The modified protection switch can make SOC back to normal when it reaches threshold, which can reduce cost and improve the quality of grid-connected power output. The overall control scheme of hybrid energy storage system that combines new control strategy with improved protection switch was proposed and simulated in MATLAB Simulink, and the results validate the correctness and the feasibility of the proposed method.