计及VSC和DFIG的电网动态无功优化模型

近年来,一系列特高压直流工程的投运和大型风电场等新能源的并网给特高压近区电网无功控制带来了新的挑战。为解决含柔性直流的交直流混联电网的无功优化控制问题,提出了含电压源换流器(Voltage Source Converter, VSC)并考虑双馈感应风机(Doubly-Fed Induction Generator, DFIG)无功支撑的动态无功优化模型。该模型以交直流电网全天网损最小为目标函数,约束包括交直流系统的潮流约束、直流变量的控制约束、离散控制变量动态调节次数约束及节点电压的安全约束。原模型是一个多时段非线性混合整数规划问题,缺乏快速有效的求解方法,通过线性化技术将原模型转化为能有效求解的二阶锥规划(Second Order Cone Programming, SOCP)问题。以IEEE30节点系统为例,通过仿真计算验证了所建模型和算法的有效性。

A dynamic reactive power optimization model considering reactive power support of DFIG and VSC

At present, along with the wide deployment of UHVDC in the power system and the connections of the high penetration of renewable energies for example large-scale wind farm, great challenges on reactive power optimization of UHVDC neighboring grid have appeared. In order to solve the reactive power optimization control issue for AC/DC hybrid power grid with flexible DC, this paper presents a dynamic reactive power optimization model with voltage source converter and considering reactive power support of the Doubly-Fed Induction Generator (DFIG). The objective function in the presented model is the minimum all-day network loss of the AC-DC grid. And also the model mainly considers four types of the constraints including the AC-DC system power flow constraints, the DC variables controlling constraints, the dynamic adjustment constraints of the discrete control variables, and the safety constraints of the node voltage. However, the model is a multi-period nonlinear mixed integer programming problem, which is tremendously difficult to be solved. As a result, by employing the linearization technology, the original model can be converted in to a second-order cone programming problem which can be efficiently solved. The evaluations have been carried out using the IEEE-30 bus system. The experiment results show the effectiveness of the presented model for dealing with the reactive power optimization task. This work is supported by National Key Research and Development Program of China (No. 2017YFB0903300) and Science and Technology Project of State Grid Corporation of China (No. DZ71-17-023).