Coordination Of Controller Parameters Considerating Steady And Dynamic Characteristics Of Power Systems

In the research of economical operation of power system, the goal of minimizing the total cost of the system operation can be always reached by adjusting the related generator output in the system under the condition of meeting the corresponding constraints and the load demands in the power system. In fact, active network loss could reach its minimum in case where control parameters such as generator voltage, on-load transformer tap position and reactive compensation installed capacity are well adjusted as well as where power flow distribution is modified. Operating parameters of the power system vary accordingly in the process of optimizing power flow, while requirements for small signal stability operation may not be satisfied in some optimizing schemes. Currently, a number of power system stabilizers(PSS) have been installed in order to increase system damping and restrain low frequency oscillations, which can improve the small signal stability. It can’t be absolutely assured that such oscillation will not occur when PSS are in place.To gain better stability and dynamic characteristics after optimizing control parameters, Small signal stability is taken into consideration when the system carries on OPF, and the influences of OPF in setting PSS parameters are also taken into consideration.Method of eigenvalue analysis is adopted in getting information of electromechanical oscillation mode and measuring sensibility of relevant operation parameters exerted by minimum damping in order to do research on influence on small signal stability wielded by parameter adjustment was further analyzed when it comes to the reactive power optimization of small signal stability. Small signal stability index is constructed using the minimum damping ratio in electromechanical oscillation mode, where the index is added in reactive power optimization objective function. In this way, optimized results do good to lower active power loss and ensure small signal stability.When doing research on the PSS parameters setting in OPF, a few steps should be followed, first, optimize generator output in several typical operating modes; second, analyze change characteristics of power flow distribution and electromechanical oscillation modes in those modes of operation; third, optimize PSS parameter based on optimized operation mode to make the PSS provide damping as large as possible; forth, check out those PSS parameters using the original operation mode. Analysis of multimachine system examples reveals that optimized PSS parameters display better adaptability.In this thesis, various optimization algorithms are accordingly employed to solve the optimization issues, and appropriate optimization algorithm is chosen based on the characteristics of optimization issues. For example, PSO is used in reactive power optimization where coevolutionary thought is used to deal with the particle swarm, the particle swarm is divided into two parts, exchanging information under evolutionary process to improve algorithm optimization efficiency. In contrast, interior point method is used to adjust generator output, taking advantage of its fast rate of convergence and high precision. Besides, improved evolutionary programming algorithm(IEP) is adopted since PSS optimal parameter consists of gain and lead-lag time constant.