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# Load Flow Analysis or Power 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 mathematics model of load flow problem is a nonlinear algebraic equation system without differential equations.

Power system dynamic analysis investigates system stability under some given disturbances. Its mathematics 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. There is 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:
1. The convergence properties
2. The computing efficiency and memory requirements
3. The convenience and flexibility of the implementation

## Voltage Stability for load flow analysis

Voltage stability is capacity of a power system to manage acceptable voltages at all buses in the system under normal conditions and after subjected to Voltage instability results in voltage collapse.

Voltage collapse is the process by which the voltage falls to a low, unacceptable value as a result of an avalanche of events accompanying voltage instability.

Voltage or power failure usually appears in power systems which usually heavy loaded failure and has reactive power shortages. In recent, voltage instability has attracted attention of power system planning and operating engineers as well as researchers. This is due to the frequent voltage collapses occurring in different parts of the world. Therefore Voltage Stability Analysis is important for researchers and power system planners to prevent such incidents from occurring.

## Voltage Stability Analysis

The different methods used are:

• P-V curve method.
• Methods based on peculiarity of power flow Jacobean matrix at the point of voltage collapse.
• Optimization Method
• V-Q curve method and reactive power reserve.
• Continuation power flow method.