Load Flow Analysis
Load flow analysis is the most important and essential approach to investigating problems in power system operating and planning. Based on a specified generating state and transmission network structure, load flow analysis solves the steady operation state with node voltages and branch power flow in the power system. Load flow analysis can provide a balanced steady operation state of the power system, without considering system transient processes.
Hence, the mathematic model of load flow problem is a nonlinear algebraic equation system without differential equations.
Load flow analysis diagram:
Power system dynamic analysis investigates system stability under some given disturbances. Its mathematic model includes differential equations. It should be pointed out that dynamic analysis is based on load flow analysis and the algorithm of load flow analysis is also the base for dynamic analysis methods. Therefore, familiarity with the theory and algorithms of load flow analysis is essential to understanding the methodology of modern power system analysis. Using digital computers to calculate load flow started from the middle of the 1950s. Since then, a variety of methods has been used in load flow calculation. The development of these methods is mainly led by the basic requirements of load flow calculation, which can be summed up as:
- The convergence properties
- The computing efficiency and memory requirements
- The convenience and flexibility of the implementation
Mathematically, the load flow problem is a problem of solving a system of nonlinear algebraic equations. Its solution usually cannot avoid some iteration process. Thus reliable convergence becomes the prime criterion for a load flow calculation method. With the scale of power system continually expanding, the dimension of load flow equations now becomes very high (several thousands to tens of thousands). For the equations with such high dimensions, we cannot ensure that any mathematical method can converge to a correct solution. This situation requires the researchers and scholars in the power system analysis field to seek more reliable methods.