中文摘要：

为了克服常规主从控制存在的功率主站丢失或达到其功率极限时,多端直流输电系统直流电压不受控以及常规下垂控制存在的正常运行时,各换流站无法精确控制其有功功率的缺陷,提出了一种双限幅功率协调控制器。该双限幅功率协调控制器包括一个上限幅环和一个下限幅环,上限幅环仅在直流电压高于某上限值时起作用并降低换流站整流方向上的有功功率,下限幅环仅在直流电压低于某下限值时起作用并降低换流站逆变方向上的有功功率。正常运行时,换流器直流端电压介于上限幅值和下限幅值之间,双限幅功率协调控制器输出被限幅至零,不起作用。文中进一步设计了连接风电场的VSC换流站功率协调控制。以一个四端口MTDC系统为例,仿真验证了双限幅功率协调控制器在不平衡功率指令、主站退出运行、风电功率波动工况下的有效性。研究结果表明,所提出的双限幅功率协调控制器综合了常规主从控制正常工作时各换流站能精确控制其有功功率以及常规下垂控制在功率失衡或故障工况下能够维持系统稳定性的优点,并克服了两种常规控制的缺陷。

英文摘要：

To overcome the drawback of the conventional master-slave control as shown in DC voltage becoming uncontrollable when the master station gets lost or reaches its power limit and the drawback of conventional droop control shown in the inability of each station to control its active power to its reference value during normal operation,a dual-limiting power balance controller is proposed.The dual-limiting controller is composed of an upper limit loop and a lower limit loop,the former will play apart only when the DC terminal voltage of a converter is higher than a certain upper limit value and reducing the rectified power of a converter.The lower limit loop will play apart only when the DC voltage is lower than the lower limit and reduces the inverted power of a converter.In normal operation,the DC terminal voltage of a converter is somewhere between the upper limit and the lower limit and the dual-limiting controller will not be activated.The power balance controller for voltage source converters interfaced to wind farm is also proposed.Simulations on a 4-terminal multi-terminal direct current（MTDC）system under unbalanced power orders,tripping of the master station and wind power variations have verified the effectiveness of the proposed dual-limiting controller.The dual-limiting controller combines the advantage of master-slave control shown in the active power of each power terminal precisely controlled in normal operation and the advantage of droop control showing the system stability retained in case of unbalanced power orders or fault,the drawbacks of the two conventional controllers overcome.