Module Development For Load Flow Calculation In Power Grid

Power flow calculation is one of the most extensive, basic and important calculation in power system analysis.The main purpose of power flow calculation is used to select the connection mode, select the wire-section of electrical equipment, as well as in power system operations, used to determine the operating mode, develop maintenance plans and determine the voltage steps in power system planning design, provide information in relay protection, automatic device design and setting calculation. So it is very important to develop the module of power flow solution.The major work of this paper is as follows:This paper describes the three methods of power flow calculation: Gauss-Seidel method, Newton Raphson method, the fast decoupled method. Gauss-Seidel method is an early emergence of a power flow calculation method has a program designed to be simple to understand the characteristics of the trend in the power calculations in the development of the software play a role; Newton Raphson method (NR method) is widely used power flow calculation of power system computer algorithm;1. The mathematical models of transmission lines, transformers, generators and power compensation equipment are studied, based on the actual operation, the entire grid looks as a regional, the buses of system are divided into swing bus, PV bus and PQ bus, there are a swing bus and a number of PV buses, the other are PQ buses, then the node admittance matrix and the basic equations of power flow calculation are listed;2. The algorithms of Gauss - Seidel, Newton Raphson and Fast Decomposition are studied; the Gauss– Seidel algorithm is the direct converging method, the rate of calculation is good for the low buses system, the slowly converging rate and large storage for the large system. In order to improve the converging rate, the Newton Raphson algorithm (NR algorithm) is used to calculate the power flow, contingencies are a major concern in power system operations, the fast decoupled algorithms (PQ algorithm) have been developed to give power-flow solutions, it is derived from simplification of Jacobian matrix of Newton - Raphson algorithm. Further reduction in computer time can be obtained from additional simplification of the Jacobian matrix.3. The design process of three algorithms are given, the calculated software are compiled. There are several parts: module of data import, module of power-flow solution, module of data outport. The data of system should be tidied in branch information (the parameters R, X, B and transformer-unit transformation ratio) and bus information (including generators active and reactive power, load active and reactive power, the bus voltage of the initial value, the reference voltage, PV bus voltage for a given value, then bus reactive power compensation and words), which are exported into Excel table.The input data should be imported into the software, and three solutions are used to calculate the power flow of the system, the results are exported into Excel table. Then use the MATLAB Compiler to compile MATLAB programs into C + + program, the software can be operating outside of MATLAB, the exe executable files can be operated in windows environment.4. Three algorithms are uses to calculate the power flow of IEEE14, IEEE30, IEEE57, IEEE118 networks, according to computing time, the number of iterations, the results, the application conditions are analyzied, then 37 buses and 70 buses real networks are uses to calculate the power flow from three solutions and Power World Simulator simulation software, the results are analyzed and compared to verify the effectiveness of the module.According to analyzed the results of three algorithms, the algorithm should be choosed to get the satisfying result in the actual system.