Advanced autonomous transformer's tap changer control system for coordinated secondar voltage control in ehv power stems

Abstract

The paper first describes the mechanism of the inadequate motion of a transformer's tap changer. We then outline the original fuzzy expert AVQC automatic Voltage and Reactive control) method in use at Tohoku Electric Power Company. We propose improved fuzzy expert and neural network methods to prevent unnecessary tap changer actions. In order to validate the improved method, simulations of tap changer behavior under various operating conditions were conducted. The results of the simulations and analyses are also presented. In the last section, we briefly recommend prudence in utilizing on-load tap changers under critical operating conditions in terms of transient stability of a power system. Index Term ---Voltage and reactive power control, Power system control, Fuzzy expert, Neural network control and BP algorithm, Power systems analysis I. LNTRODUCTION Voltage and reactive power control facilities, such as static condensers, shunt reactors, and SVR (Static Voltage Regulator) for EHV and UHV power systems, are not only expensive, but also limited in terms of available control capability. The control of voltage and reactive control of EHV and UHV bulk power transmission networks depend on the control capacity of large-scale generator units and on-load tap changers of transformers at EHV or UHV substations. In Tohoku Electric Power Company, all step-up transformers of large generating units at thermal and nuclear power stations have been equipped with on-load tap changers since 1968. The tap changers are locally operated by the conventional AVQC system. T. Minakawa and E. Monma are with the

A local demand forecast by NN method for distributed autonomous voltage and reactive power control system

“…The NN intelligent architecture of acquiring voltage and reactive power characteristics can be designed as shown in Fig. 4 [5,10,11]. Table 1 shows an example of voltage and reactive power characteristics estimated by the developed NN method.…”

“…Local voltage and reactive compensation equipment should be provided with a more advanced intelligent control function based on distributed autonomous control theories. This paper briefly presents the concept of technological innovation for a local demand forecasting method [5,6,10]. Figure 2 shows a comparison of the control block diagrams between conventional and proposed AVQC systems [11].…”

“…There is no practical local demand forecasting method. The voltage characteristics of a power system depend on short circuit capacity, which is affected by total and local demand distributions and the topology of a power system network configuration [5]. As the feasible time of demand forecast of a local area, which was previously developed, was limited to within 0.5 to 5 minutes [2], the present forecast method cannot be applied to a longer time domain of demand forecasting.…”