含网损模拟的DCOPF对参考节点的依赖性及电力网欠秩问题

Dependence of lossy DCOPF on reference bus and power system rank-short problems

智能电网的发展,使基于DC潮流并模拟网损(简称"有损")的OPF被日益广泛应用。但至今,该OPF所得发电功率的解对参考节点的依赖性仍缺乏深入研究。为此,文中先构建基于DC潮流雅可比逆阵的直接网损模拟公式,再构建基于DC潮流并直接模拟网损的OPF模型,然后通过仿真就这种OPF所得发电功率的解对参考节点的依赖性展开深入分析。结果表明,这种OPF所得发电功率的解对参考节点有依赖性、且该依赖性对线路潮流极限约束很敏感。该依赖性的主要根源是模型中采用了丢参考节点的雅可比矩阵方程,这导致"用参考节点对地短路电网的电气量关系替代原始电网电气量关系"的原理性缺陷。这种OPF运用于电力系统调控时调节次数多、效能低。最后归纳出一类电力网欠秩问题,指出该类问题在已有电力系统理论范畴内尚无方法求解、探讨其解法对提高电力系统运行性能有重要意义。

With the developments of smart grid, the application of DC-power-flow based OPF with grid losses modeling becomes wilder and wilder. However, the dependence of this OPF solution, such as generation MW solution,on reference bus is seldom investigated. For this reason,a formula is built at first to directly model grid losses based on the inverse Jacobian matrix of DC power flow. Then a DC-power-flow based OPF model with losses directly modeled is built. At last the reference bus dependence of this OPF solution is investigated via numerical simulation. It is revealed that the generation MW solution of this OPF always depends upon the change of reference bus, and the extent of dependence is sensitive to line power limits. This dependence stems mainly from the adoption in OPF model of Jacobian matrix equation discarded reference bus,which leads to the principle defect that ＂the V-I relationship of original grid is replaced by that of reference-bus-to-ground short-circuit grid＂. This OPF leads to repeated regulation,low efficiency and economy when used in power system regulation. Consequently, the power grid rank-short problems are summed up. And it is pointed out that the existing power system theory fails to solve these problems,their solution methods are important for improving power system operation performance.