基于多速率仿真和简化离散牛顿法的电压源型换流器和直流电网机电暂态模型

AN Electromechanical Transient Model of VSC and DC Grid Based on Multi-rate Simulation Method and Simplified Discrete Newton Method

提出一种基于多速率仿真和简化离散牛顿法的,适用于大规模电网稳定分析的电压源型换流器和直流电网机电暂态模型。对电压源型换流器(voltage source converter,VSC)和直流电网采用小于交流电网的仿真步长。在多速率仿真流程中采取抑制输出波动,每次小步长迭代调整dq坐标,管理故障操作的影响等措施考虑VSC的特性。提出一种称为简化离散牛顿法的拟牛顿类非线性方程组迭代解法,以提高大扰动时VSC大功率注入交流网络的迭代收敛性,减小计算用时。给出快慢时步交直流侧仿真流程,构建完整的VSC和直流电网机电暂态模型。通过与PSCAD电磁暂态模型的对比验证所提模型的正确性与效率,用国家电网公司规划数据等算例说明算法的价值,并分析限制该模型精度的因素。

An electromechanical transient model of VSC and DC grid based on multi-rate simulation method and Simplified Discrete Newton Method was put forward, which suits for analyzing stability of bulk power grid. Simulation step ngth of VSC and DC grid is less than it of AC grid. In multi-rate simulation some measures were taken to include the characteristic of VSC, which are restraining output pulsation, updating dq coordinate every small-step iteration, and controlling impact from fault or manipulation. A quasi Newton class method of nonlinear equations iterative solving, named Simplified Discrete Newton Method, is put forward to improve convergence cause by great VSC power pouring to AC grid during huge disturbance, which can decrease computation time. Flow chat of slow and fast rate simulation as well as AC and DC side were given, and whole electromechanical transient model of VSC and DC grid was built. Correctness and efficiency of this model was verified by electromagnetic transient model in PSCAD. Value of this model is embodied through cases of China state grid plan data and others. Moreover, factors restricting simulation accuracy of this model were discussed.