Yung-Sung Chuang

Design of decentralized output feedback power system stabilizers using hybrid differential evolution

This paper is used to investigate the application of hybrid differential evolution (HDE) method in the design of output feedback power system stabilizers (PSSs) to enhance damping of electromechanical modes. The HDE is useful to get the parameters of PSSs to suppress oscillations of a power system subjected to disturbances. The PSSs have the output feedback configuration, and thus they could be implemented easily. In the design procedure, the objective function is chosen to ensure the real parts of electromechanical modes and/or the damping ratios. The searching for nearly global optimal solutions could be obtained and the computation time is short. The design purposes are to guarantee the damping effects of the entire power system. The effects of system loading are also considered. Nonlinear system time domain simulations are used to demonstrate the design results.

Tuning of Static Excitation Systems to Improve Dynamic Performance for Generators Serving Electric Arc Furnaces Loads

This paper describes the useful experiences about dynamic performance improvement of synchronous generators in the Tong-Shiao Generation Station of the Taiwan Power System. This work includes the dynamic performance test, parameter identification, and parameter retuning of static excitation systems (SESs). Since the hardware circuits of SESs had been modified, it caused the detuning of parameters so that the generators did not have enough ability to sustain large voltage fluctuation disturbances. Those SESs were temporarily retuned according to the results from simple field tests. However, step responses of field tests were different from those of computer simulations. Thus, the least-squared-error algorithm has been employed to estimate the parameters of inner-loop regulators in SESs. Finally, the hybrid differential evolution method was used to get suitable parameter values. The SESs of six gas-turbine generators have been retuned again and these have worked well till now. The experiences and results provide useful references.

Direct Coherency Identification of Synchronous Generators in Taiwan Power System Based on Fuzzy c-Means Clustering

This paper is to investigate the application of fuzzy c-means clustering to the direct identification of coherent synchronous generators in power systems. Because of the conceptual appropriateness and computational simplicity, this approach is essentially a fast and flexible method. At first, the coherency measures are derived from the time-domain responses of generators in order to reveal the relations between any pair of generators. And then they are used as initial element values of the membership matrix in the clustering procedures. An application of the proposed method to the Taiwan power (Taipower) system is demonstrated in an attempt to show the effectiveness of this clustering approach. The effects of short circuit fault locations, operating conditions, data sampling interval, and power system stabilizers are also investigated, as well. The results are compared with those obtained from the similarity relation method. And thus it is found that the presented approach needs less computation time and can directly initialize a clustering process for any number of clusters.

Test results of three excitation systems for generators suffering continuous voltage flicker disturbance

This paper uses field test methods to compare the dynamic stability of three types of excitation systems, static excitation systems, brushless rotating excitation systems, and digital excitation control system, at the Tong-Shiao Generation Station of the Taiwan Power System. Three electric arc furnaces in this area produce continuous disturbance of voltage flicker (voltage fluctuation). The dynamic performances of generators and effects of voltage flicker will be evaluated by a series of field tests and measurements. At first, the field measurement is taken by injecting a small step signal into the reference input of the excitation systems for the generators at no-load. The system responses are examined and compared with the IEEE standard 421.2 recommendation to check the stability conditions. The tests for the generators at on-load are repeated again. Then the outputs of the generators are continuously monitored during the operation of the electric arc furnaces. The dynamic characteristics of the generators with different excitation systems are compared to reveal the effect of voltage flicker.

Frequency domain approach to suppress power oscillations of synchronous generators caused by voltage flicker disturbances

A frequency domain approach is used to tune the static excitation systems (SESs) of combined-cycle synchronous generators in the Tong-Shiao generation station in Taiwan to suppress active and reactive power oscillations caused by voltage flicker disturbances. Two electric arc furnaces are fed from this station. The continuous changing of furnace loading has caused voltage flicker disturbances at generator voltage buses, and then induced oscillations of generator active and reactive powers. It is required that the generators have ability to stand voltage flicker disturbances. The parameters of static excitation systems should be adjusted to enhance the damping of electromechanical modes. The frequency spectrum of field measurement voltage waveforms has revealed the frequency components of flicker disturbances. Then the static excitation systems were tuned so that the closed-loop transfer function has a low gain and a suitable bandwidth in the flicker frequency range. Eigenvalue analysis has also been employed to explore the effect of loop-gains, and the dynamic responses of generators were checked by time domain computer simulations.

OLTC Voltage and Reactive Power Control in Area Transmission System for Improvement Line Loss and Voltage Variation

Coordination on load tap changers (OLTCs) voltage and reactive power compensators in area transmission power system is presented to improve efficiency and voltage variation using a novel optimum procedure technique. The novel optimum technique procedure used hybrid differential evolution (HDE) to coordinate the OLTCs setting and reactive power compensation for reducing line losses and voltage change rate. The objection function is selected total line loss under the limited range of OLTCs setting and reactive power compensation. The proposal design method is used to IEEE-30BUS power system to demonstrate the useful method. The result exhibits to less line losses and a little voltage variation.