基于功角动态补偿的VSG故障穿越方法研究

VSG Fault Crossing Method Based on Dynamic Compensation of Power Angle

虚拟同步发电机(virtual synchronous generator,VSG)在电网受到大干扰时会出现和传统发电机一样的暂态功角失稳的问题,无法抑制短路过电流,威胁VSG的稳定运行。为此,提出一种在故障期间导入功角动态补偿的VSG故障电流控制策略。首先分析了短路故障工况下VSG控制存在的功角增大和过电流的原因,在借鉴传统同步发电机暂态功角曲线判稳的基础上,利用VSG控制结构和参数灵活可变的优势,在有功环中导入功角动态补偿控制,并且整定了自适应的功角控制系数;另外根据功角重新整定故障期间无功环中的电压指令值,解决了传统电压环采用积分控制时的无功功率越限的问题。所提方法不仅可以抑制故障过程中不平衡转矩造成的功角持续增大以及短路过电流,而且改善了VSG的频率输出特性。从而实现VSG在电网短路故障下的安全稳定运行。

When the power grid is greatly disturbed, the virtual synchronous generator will have the problem of transient power angle instability as that of the traditional generator, which cannot suppress the component of short-circuit current, threatening the stable operation of virtual synchronous generator(VSG). For this reason, this paper presents a control strategy of improved active loop that introduces power angle control during the fault. First the reasons of the VSG angle increase under the fault conditions is analyzed. In reference to the traditional synchronous generator transient angle curve for stability, using the VSG control structure and the advantage of the flexible parameters, the additional angle control in the active ring is introduced, and the adaptive synchronization angle control coefficient is set. In addition, according to the voltage instruction value in the reactive power loop when the power angle resets the fault, the problem of reactive power off-limit when the traditional voltage loop controls with robust. The proposed method can suppress the continuous increase of power angle and the unbalanced torque and short-circuit overcurrent during the fault process, improving the frequency output of the VSG. It realizes the stable operation of VSG under short-circuit fault.