Ying Liming

Power quality disturbances detection and location using mathematical morphology and complex wavelet transformation

Bused on mathematical morphology (MM) and complex wavelet, a novel method on power quality (PQ) disturbance detection and location is presented in this paper. At first, a generalized morphology filter with horizontal linear structure elements is designed to filter impulses and random white noises in PQ disturbance signals. Numerical simulation results show that the characteristics of the original signal can be well retained and the noise interferences are suppressed effectively with the proposed filter method. Then, to the filtered results, the complex wavelet derived by Daubechies real wavelet and its compound information are applied to detect and locate the start and end time that the disturbance occurs. The voltage interruption, voltage sag, voltage swell, high frequency oscillation and harmonic distortion are used to verify the validity of the filter-location approach. Simulation results show the integrated detection approach of morphology-complex wavelet is valid and effective. Besides, it can reduce calculation time and can be implemented easily in the available hardware.

Risk assessment model of relay protection system based on multi-state Bayesian networks

Relay protection is important for power systems stable operation. However, logic state of traditional Bayesian network is simplex. To adapt to the relay protection system operation environment with increasing complexity in current years, a risk assessment model of relay protection system based on multiple-state Bayesian networks is established with dynamic and static indexes. Taking advantages of figurative expression of Bayesian network, the model can express multiple states of system and probability clearly, and also can calculate the risk grade by using qualitative and quantitative analysis of multi-state Bayesian networks.

Performance analysis of self-excited induction generators under unbalanced conditions

The general mathematical model of SEIG under unbalanced conditions was presented in this paper. The model is derived from using symmetrical components theory and the sequence equivalent circuits of the generator. The method avoids lengthy and tedious algebraic derivations. Performance characteristics of a SEIG under unbalanced conditions were analyzed. There is a good agreement between the calculated and experimental measured values.

State comprehensive evaluation of secondary equipment in an intelligent substation based on real-time information

Secondary equipment of real-time information on its status evaluation plays a very important role. And the development of secondary equipment intellectualization and change the way of communication, the equipment real-time state information in an intelligent substation secondary can through the device self-checking information data to realize the online monitoring and network analyzer. Comprehensive evaluation model of secondary equipment health status based on real-time monitoring of environmental information is established. The analytic hierarchy process (AHP) and the subjective and objective combination method of the entropy weight method is used to reduce the weight deviation. Considering the serious information easy to be submerged risks in the process of traditional weighted, a mechanism of that serious information trigger weight fusing and redistribution weight correction is put forward, to ensure the accuracy of the evaluation results. The state evaluation results of fuzzy membership degree is transferred into the evaluation scores and the corresponding state level is determined. The rationality of the comprehensive status evaluation model proposed in the paper is verified by the example analysis.