An Analytic Hierarchy Process Based Method For Identifying Coherent Generator Groups

With the extensive application and growing influence of power electronic devices in power system, electromagnetic transient simulation is strongly demanded in order to study on it. Due to the limit of simulation algorithm, the scale of simulation system can not be as large as practical power system. Therefore, dynamic equivalent is needed to maintain the dynamic characteristics of the whole system. Coherency-based equivalence method is widely used, whose key content is the identification of coherent generators. As a result, the research on the process of coherency identification is of great significance to dynamic equivalence.To solve the subjective and one-sideness problems in the process of coherency identification, more factors are taken to account to analyze the coherency of generators. Using the experience of analytic hierarchy process for reference, a practical AHP model is set up, which combines key factors such as swing curves, topological structures, parameters of the generators and so on, in order to change the process of coherency identification from single-decision making to multiple attribute decision making. For multi-generator swing curves, using dynamic time warping method combining with Prony signal analysis method, characteristic parameters such as trend, frequency, amplitude and damping, are extracted and taken into similarity analysis in both time and frequency domain. According to the need of AC-DC power system electromagnetic transient simulation and the operation characteristics of regional power grid, parameters and topology of the generators are integrated with swing curves to identifying coherent generator groups. Taking the specificity of500kV main network frame into consideration, based on engineering applications, a set of practical methods is summed up. It is proved by practice that this set of methods can increase the controllability and reduce error in dynamic equivalence process. Simulation results of IEEE39-bus system and North China500kV power grid show that this method is accurate and practical in both identifying coherent generator groups and improving dynamic equivalent results.