Design And Tuning Of TCSC Damping Controller To Enhance Power System Small Signal Stability

Management of power systems is becoming increasingly difficult compared to the past, because modern interconnected power systems are large, complex and operated closer to security limits. Furthermore, due to the deregulation of the electrical market, difficulty in acquiring rights-of-way to build new transmission lines, and steady increase in power demand, maintaining power system stability becomes a difficult and very challenging problem. In large interconnected power systems, power system damping is often reduced, which results in lightly damped electromechanical modes of oscillations. These oscillations may sustain and grow to cause system separation if no adequate damping is available. Thus, improving stability and increasing damping of electromechanical oscillations between interconnected power systems, becomes the most important issue for a secure operation.A traditional solution for solving this problem is use of Power System Stabilizer (PSS). Despite PSS's aid to improve power system stability and damp out all oscillation modes, but due to complexity of present day power systems, the number of modes of oscillation experienced by a particular generator has become large and the frequency of these modes has begun to vary over a wide range. Therefore, the design of an effective PSS has become extremely complex and difficult. Thus, Implementation of new equipment consisting of high power electronics based technologies such as Flexible Alternating Current Transmission Systems (FACTS) and proper controller design become essential for improvement of stability and damping oscillations.In this dissertation TCSC-damping controller is proposed, as a compromise solution over the traditional PSS. In order to damp all oscillation modes, a supplementary feedback signal from a power oscillation damper (POD) is applied to TCSC-controller. A residue based-method is implemented to design and compute the parameters of the controller. Then, the optimal location is selected according to mode controllability index and the input signal of controller according to the mode observability index.The design based on the mentioned approach can provide excellent damping over a certain range around the design point. However, controller parameters may not be optimal for whole set of possible operating conditions and configurations, or in some cases it may interacts with other controller particularly PSS. So the proposed TCSC-damping controller needs to be tuned to coordinate with other machines and devices. Two tuning techniques are represented Genetic algorithm (GA) and Particle Swarm Optimization (PSO). The problem is then formulated as an optimization problem to tune TCSC-damping controller parameters so that damping ratio increased above predetermined value.To validate the performance and robustness of proposed controller, a nonlinear time domain simulation is carried out on a SMIB and a multi-machine system under different disturbances and fault locations. Time domain-based design and eigenvalues analysis results show the effectiveness of the proposed TCSC-damping controller to enhance stability and to damp different oscillation modes.