The WARD Static Equivalence Based On Block Matrix Operations Using Matlab And Example Analysis

With the development of power system, we can see that, the power system scale is getting bigger as well. But now, the power system is interconnected, when analyzing the state of the internal system on-line and off-line, the information of the external system does not send to the dispatching center. But the operation of the external system has an important effect on the analysis of the internal system, so it requires external system equivalence.Due to the causes of the complexity and the workload, this paper selects the conventional WARD static equivalence. The equivalence procedure is based on the base power flow; the whole system can be divided into three parts:the inner nodes, the border nodes and the outer nodes. We select the inner nodes according to the geographic position and select the first-class buffer network and the second-class buffer network according to the inner nodes. In the paper, the first-class network is considered to be the boundary nodes and the whole network is partitioned into block matrix.Then, the generating and the load are been transferred to the boundary nodes by the linear matrix operations of block matrix.Furthermore, the off-normal transformer tap ratio and the transmission lines charging capacitor are using different methods when forming the complex admittance matrix. We propose a concept of the transformer unit line group and the disposal ways ahout it. We partition admittance matrix of the whole system as needed. We work out the admittance matrix of the boundary nodes by the matrix operation of block matrix, equivalence power and the equivalence load of the outer net. The resistance of internet branch of boundary nodes can also be calculated by the admittance of the above.The resistance to ground which be mounted on the boundary nodes can be calculated by the admittance of the above and the internet branch which connected to the internal nodes.The purpose is to perfect the equivalent network. We implement the previous matrix operation by the Matlab C++ math library which is integrated within the VC++6.0. Thus, the operation efficiency will achieve to the Matlab-level, the calculation time is reduced greatly and the performance of operation is improved obviously.This article utilizes the method of step by step, taking 5-bus,12-bus and 639-bus of Shandong power system in 2007 as example.The basic principle, basic process, processing method of the core problem and usage of Matlab math library are introduced by these examples. The whole process is implemented by C++ programs.We see that, the scale is reduced largerly after the static equivalence.It can be known easily that, the static equivalence has achieved the result expected by the comparative of the parameters and the convergence of the power flow solutions of this example. The system after equivalence is normal without any distortion occurring and the ward static equivalence has a substantial interest in industrial application.