基于附加电量的直流微电网动态稳定控制策略

直流微电网的低惯性问题以及遭受扰动后分布式电源与负荷短时保持功率恒定引入的负阻尼,均会削弱直流电压的动态稳定性.对此深入探讨了直流微电网的动态稳定机理,从电量的角度赋予系统稳定判据物理意义.首先基于直流微电网的伏安特性,分析系统运行点的移动轨迹与稳定运行约束条件.其次,基于直流微电网的状态方程,推导系统的电量模型,分析各端换流器具备的暂态电量对系统稳定运行的影响机理,并结合稳定运行条件,提出基于附加电量的直流微电网的动态稳定裕度及判据.然后,基于直流微电网的动态稳定裕度,通过改进储能侧换流器的电压下垂控制,提出基于附加电量的直流微电网电压动态稳定控制策略,并分析其对直流电压暂态过程的影响.最后,搭建多端直流微电网仿真系统,验证所提电压动态稳定判据的正确性,以及附加电量对直流微电网动态稳定的支持能力.

Dynamic stability control strategy of DC microgrid based on additional electric quantity

The low inertia of the DC microgrid, as well as the negative damping introduced by short-time constant power of distributed power supply and load after disturbance, will weaken the dynamic stability of DC voltage. Thus the dynamic stability mechanism of DC microgrid is deeply discussed, and the stability criterion of the system is endowed with physical significance from the perspective of electric quantity. Firstly, based on the volt-ampere characteristics of DC microgrid, the movement trajectory and stable operation constraints of the system operating point are analyzed. Secondly, based on the state equation of the DC microgrid, the electric quantity model of the system is derived, and the influence mechanism of the transient electric quantity provided by the converters at each terminal on the stable operation of the system is analyzed. Combined with the stable operation conditions, the dynamic stability margin and criterion of DC microgrid based on additional electric quantity are proposed. Thirdly, based on the dynamic stability margin of DC microgrid, by improving the voltage droop control of the energy storage side converter, a DC microgrid voltage dynamic stability control strategy based on additional electric quantity is proposed, and its influence on DC voltage transient process is analyzed. Finally, a multi-terminal DC microgrid simulation system is built to verify the correctness of the proposed voltage dynamic stability criterion and the supporting ability of additional electric quantity to dynamic stability of DC microgrid.