Intelligent Controller Based STATCOM for Improving Dynamic Stability of a Hybrid Power System

Abstract

Renewable energy sources, which are expected to be a promising alternative energy source, can bring new challenges when connected to the power grid. A large amount of wind turbines are connected to the electrical power system in order to mitigate the negative environmental consequence of conventional electricity generation. While connecting the wind turbine to grid it is important to understand the source of disturbance that affects the power quality. FACTS devices are found to be very effective for stability enhancement followed by a disturbance. Static Synchronous Compensator (STATCOM) which is a shunt device of FACTS family is efficient in regulating voltage either by absorbing or by generating reactive power. STATCOM can provide fast and efficient reactive power support to maintain power system voltage stability. This paper proposes a Hybrid control model for STATCOM that controls the voltage during a disturbance. The proposed controller is implemented to the STATCOM under MATLAB/SIMULINK environment. In the simulation test, the hybrid control shows consistent excellence under a severe disturbance like three phase fault. Keywords: STATCOM, power quality, FACTS, power grid, hybrid controller. I.INTRODUCTION Electric power system is a complex system in its structure and operation is facing many challenges day by day. The major problem in power system is its instability. Power system stability is the capability of the system to maintain an operating equilibrium point after being subjected to a disturbance for given initial operating conditions. Traditionally voltage regulation is performed by the excitation system and thereby help in controlling the system voltage. Suitable devices like Automatic Voltage Regulators (AVR) are used for the regulation of generated voltage. AVR's normally maintain the generator voltage magnitude at a specified level. AVR's are extensively used on the dynamic or steady state stability of the power system as low frequencies oscillations persist for a long period and may affect the capability of power transfer. Electrical power demand is rising at a very higher rate because of rapid industrial development. In order to satisfy the demand, power transmission has to be raised along with the existing facilities. Thus it is essential to concentrate on the power flow control. The power system should be flexible to adapt itself to any momentary changes in system conditions. In an AC power system, there must be a balance between the generated power and variations in load demand while keeping the system frequency and voltage levels as constant. If the generation is not sufficient, the voltage and frequency drop and the load decreases to balance the total generation minus losses in transmission. But there are only a few percent margins for such a self-regulation. Hence the system is collapsed. Generator excitation controller normally improves stability for smaller faults but not suitable for larger faults that occur near to generator terminals. Thus, traditional methods have to be rev...