Design of Self-Tuning PID Power System Stabilizers for Synchronous Generators

A new technique for the excitation control of a synchronous generator is presented in this paper. The proposed technique employs a self-tuning proportional-integral-derivative (PID) power system stabilizer in order to improve the dynamic performance of a synchronous machine under a wide range of operating condition. Digital simulation of a synchronous machine subject to a major disturbance of a three phase fault under different operating conditions is performed to demonstrate the effectiveness of the proposed controller. It is found that the self-tuning PID stabilizer can enhance both the transient stability and the dynamic performance of the synchronous machine.     

Adaptive control of a synchronous machine using the auto-searchingmethod

A novel adaptive control scheme is presented for the design of a power system stabilizer (PSS) and a static VAr (reactive volt-ampere) compensator (SVC). The developed adaptive proportional-integral (PI) controllers, whose gains are adjusted in real time using the online-measured system operating conditions and a look-up table stored in computer memory, can offer better damper effects for generator oscillations over a wide range of operating conditions than conventional PI controllers with fixed gain settings. The effects of the adaptive PSS and the adaptive SVC on generator damping and terminal voltage profile are examined by computer simulation of system dynamic responses to a major disturbance     

Experience with the identification and tuning of excitation systemparameters at the second nuclear power plant of Taiwan powercompany

Experience with the identification and tuning of exciter constants for a generating unit at the second nuclear power plant of the Taiwan Power Company is reported. A field test is first performed on the excitation system with the generator open-circuited. Since the field test results differ from the computer simulation results using manufacturer's constants, the authors first modify the manufacturer's constants based on their previous experience to reach a preliminary set of parameters for the excitation system. Then a hybrid nonlinear simulation-sensitivity matrix method is developed to further refine the excitation system parameters. The exciter constants are tuned in order to give better dynamic response before a power system stabilizer is applied to the generator. Field tests are then performed in order to compare the dynamic response of the generator without and with power system stabilizer     

Low Frequency Oscillations in Longitudinal Power Systems: Experience with Dynamic Stability of Taiwan Power System

Sustained low frequency oscillations have been observed in Taiwan power system which is of longitudinal structure. It is the purpose of this paper to examine the various factors affecting the damping characteristics of these oscillations which caused dynamic instability problem in the operation of Taiwan power system. It is observed that the amount of power flow on the EHV transmission line and the characteristics of load have a significant effect on the damping of the system while the speed-governing system and the gain of automatic voltage regulator have only a minor one. Detailed investigation using both the frequency domain and time domain approaches also reveals that power system stabilizers can be employed as an effective means for improving dynamic stability of Taiwan power system.     

A combined artificial neural network-fuzzy dynamic programmingapproach to reactive power/voltage control in a distribution substation

Reactive power/voltage control in a distribution substation is investigated in this work. The purpose is to determine proper capacitor on/off status and suitable load tap changer (LTC) positions for the 24 hours in the next day. To reach this goal, an artificial neural network (ANN) is designed to reach a preliminary dispatch schedule for the capacitor and LTC. The inputs to the ANN are main transformer real power and reactive power and primary and secondary bus voltages and the outputs are the desired capacitor on/off status and LTC tap positions. The preliminary dispatch schedule is further refined by fuzzy dynamic programming in order to reach the final schedule. To demonstrate the effectiveness of the proposed method, reactive power/voltage control is performed on a distribution substation in Taipei, Taiwan. Results from the example show that a proper dispatch schedule for capacitor and LTC can be reached by the proposed method in a very short period     

Stabilization of power systems using a variable structure stabilizer

A new technique for improving the dynamic stability of power systems is presented. This new technique makes use of the variable structure system theory and employs the generator speed to obtain a stabilizing signal to increase the damping torque of the synchronous machine.Although modern voltage regulator and excitation systems with fast response and high ceiling voltage can improve the transient stability by increasing the synchronizing torque, their effect on the damping torque is rather small. Under certain operating conditions, when the system exhibits negative damping characteristics, the voltage regulator usually aggravates the situation by increasing the negative damping. Hence, instability may result. In order to reduce this undesirable effect, it is useful to introduce supplementary stabilizing signals to increase the damping torque of the synchronous machine.This paper proposes a variable structure stabilizer for generating the required stabilizing signal. Simulation results indicate that the proposed stabilizer yields better system dynamic performance than that obtained by using the conventional and linear optimal stabilizers in that the step responses have less overshoot and a shorter settling time.It is concluded that the new stabilizer can be used as an effective means of increasing the damping torque and hence improving the dynamic stability of the power system.     

Optimal control of electric power generation using varible structure controllers

This paper presents a new approach to the automatic generation control of power systems. It makes use of the theory of variable structured systems to investigated the automatic generation control of a steam electric power plant. Improvements in both the dynamic and static performances can be achieved by means of the sliding mode provided by a variable structure controller. The main feature of the sliding mode is that the system willhave low sensitivity; certain desirable properties can be obtained by minimizing a quadratic performance index specified in the sliding mode. For comparison, results obtained using a convetional controller and a linear optimal controller are also included.     

Application of power system stabilizers and static VAr compensatorson a longitudinal power system

The dynamic stability improvement of a longitudinal power system using a power system stabilizer (PSS) and a static VAr (reactive volt-ampere) compensator (SVC) is reported. An analytical approach is developed for the determination of PSS parameters. The effect of static VAr compensators installed at several different locations along 345 kV trunk lines on system responses is examined. Results from time-domain simulations indicate that the PSS and the SVC are very effective in damping system oscillations     

Effect of a pumped storage plant on the generation reliability of the Taiwan power system

A novel approach to the reliability analysis of a power system with both hydro and pumped storage plants is presented in this paper. The proposed method is based on the concept of peak shaving for the hydro and pumped storage units. Different values of the stored energy of the pumped storage units are employed to demonstrate their effect on the generation reliability of a power system. The proposed scheme has been applied successfully to the reliability analysis of Taiwan power system.