光储直流微网能量协调控制方法

摘要

The stochastic volatility of distributed power output from DC microgrid not only causes a large range of DC bus voltage fluctuations,but also affects the stable operation of the system. To solve this problem, an energy coordi-nated control method for DC microgrid with photovoltaic(PV)and hybrid energy storage(HES)is proposed in this paper, which achieves the rapid suppression of bus voltage fluctuations caused by the power imbalance between supply and de-mand.This method gives priority to the use of new energy sources for load power supply. By setting the working thresh-olds of grid converter and energy storage module to coordinate and manage the energy flow among modules,the frequent actions of power electronic devices due to the small range of fluctuations of DC bus voltage can be avoided,realizing the optimal use of energy. In the on-grid operation, the DC microgrid exchanges power with the large grid through grid con-verter; in the off-grid operation, the PV module and HES module coordinate to supply power for the local loads. In the second operation, with the consideration of the charging/discharging margins of HES module as well as the characteris-tics of super capacitors(i.e., large power density)and lithium batteries(i.e., large energy density), the HES module ma-kes the super capacitor work first to balance the instantaneous power of the system,which improves the system's dynam-ic response characteristics, reduces the actions of lithium batteries, and extends their service life. After lithium batteries start to work,they can coordinate with super capacitors to adjust the DC bus voltage to prevent the super capacitors from reaching saturation too fast.Simulation results verify the effectiveness of the proposed method.%直流微网中分布式电源出力的随机波动性,不仅会引起直流母线电压大范围波动,还会影响系统的稳定运行.对此,提出了一种光储直流微网能量协调控制方法,实现了因系统功率供需不平衡引起的母线电压波动的快速平抑.该方法优先利用新能源为负荷供电,通过设定并网变换器和储能模块的工作阈值以协调管理各模块间的能量流动,避免直流母线电压小范围波动引起电力电子器件频繁动作,实现能量的最优利用.在并网状态下,直流微网通过并网变换器与大电网进行能量交换;在离网状态下,光伏模块与混合储能模块协调配合给本地负载供电.其中,考虑混合储能模块的充放电裕量,结合超级电容功率密度大和锂电池能量密度高的特点,混合储能模块让超级电容先工作来平衡系统瞬时功率,提高系统的动态响应特性,减少锂电池动作次数,延长使用寿命.锂电池工作后,可以配合超级电容调整直流母线电压,防止超级电容达到饱和的速度过快.仿真验证了所提方法的有效性.