The poor voltage stability and weak damping of flexible DC distribution system bring great challenges to its safe and stable operation, and its power imbalance also has a negative impact on AC distribution system. In this paper, a novel dead-zone based PID control strategy and a coordinated hierarchical voltage control (CHVC) paradigm are presented to improve the voltage stability and the damping of flexible DC distribution systems. The dead-zone based PID control is performed by a PID controller with a dead zone. It can not only carry out fast power demand response, but also prolong the service life of the battery. The CHVC strategy coordinates the battery converter control and the interconnected voltage source converter (VSC) droop control. It can not only improve the overall dynamic and steady-state characteristics of the system, but also reduce the influence of the DC system unbalanced power on the AC system. Furthermore, the effects of DC line parameters, the intensity of interconnected AC distribution systems and outer loop control parameters on the stability of the system are also analyzed, which can provide a theoretical basis for the selection of system hardware and control parameters. Numerical examples verify the feasibility and the effectiveness of CHVC.

柔性直流配电系统电压稳定性差、阻尼弱，对其安全稳定运行带来极大挑战，其功率不平衡也对交流配电系统产生负面影响。在本文中，提出了一种新的基于死区的 PID 控制策略和协调分级电压控制 (CHVC) 范式，以提高柔性直流配电系统的电压稳定性和阻尼。基于死区的 PID 控制由具有死区的 PID 控制器执行。它不仅可以进行快速的电力需求响应，还可以延长电池的使用寿命。CHVC 策略协调电池转换器控制和互连电压源转换器 (VSC) 下垂控制。它不仅可以改善系统的整体动态和稳态特性，同时也减少了直流系统不平衡功率对交流系统的影响。此外，还分析了直流线路参数、互联交流配电系统的强度和外环控制参数对系统稳定性的影响，为系统硬件和控制参数的选择提供了理论依据。数值算例验证了CHVC的可行性和有效性。