Xian-Yong Xiao

Harmonic Source Location at the Point of Common Coupling Based on the Nonlinearity Index of Load

Harmonic source quantitative location can not simply be achieved by the severity of load harmonic distortion at the point of common coupling (PCC) because the tested harmonic at PCC contains the background harmonic and the harmonic of given customer emission. Harmonics in distribution system are caused mainly by nonlinear loads. In view of this, a harmonic location method based on the nonlinearity index (NLI) of loads is proposed. In this method, the real parameters of loads are calculated by using the time domain model, and the linear parameters of loads are obtained by removing residual error. The nonlinearity index is calculated to evaluate the harmonic emission level. The simulation and the practical engineering results indicate that the proposed method is valid and feasible.

The optimal selection of investment scheme for premium power considering customer perception of utility

High-tech manufacturing customers (HTMCs) are sensitive to the event-based disturbances, such as voltage sags and short-time interruptions, which make them eager to obtain premium power. But the selection of optimal investment scheme is still a difficult problem. Analyzing the HTMCs demands for premium power, the two-sided matching relationship between the HTMCs demands for premium power and the level of premium power brought by investment schemes is studied. Based on the preference ordinal number of HTMC obtained by a simple survey, the preference degree of HTMCs and its quantification method are presented. Consider the disappointment-rejoicing psychology perception of HTMC, the perceived utility (PU, refers to the perceived effectiveness or satisfaction degree) is introduced and the quantification method of PU is also proposed. Then the optimal objective model of investment scheme for premium power is presented and the related algorithms are studied in detail. With the help of a field survey by the authors, five HTMCs located in a High-Tech Park in Western China are evaluated. The results compared with the actual survey have proved the rationality and correctness of the proposed method.

Complex blind source separation based harmonic contribution assessment

Harmonic contribution assessment is the precondition of harmonic responsibility-sharing and mitigating and its difficulty lies in real-time assessment of harmonic impedance. In order to solve this problem, this paper proposed a complex blind source separation (CBSS) based harmonic contribution assessment method. Use linear filter to abstract fast changing components from measuring data at the point of common coupling (PCC) and establish a CBSS based harmonic contribution assessment model; use complex maximization of non-Gaussianity (CMN) to assess demixing matrix, impedance matrix, and harmonic sources and the process of harmonic contribution assessment is studied in detail on this basis. The proposed method is validated by simulation, comparing with current methods, and the results prove that the proposed method can separate harmonic contribution directly with measuring data and it is suitable for resonance and non-resonance cases.

Nonadditive Measure and Assessment Method of the Failure Possibility of Sensitive Equipment Due to Voltage Sags

The choice of measure is the foundation of accurate assessment of sensitive equipment failure possibility due to voltage sag. When the additivity of probability measure is unable to be contented, possibility measure which is possessed of nonadditivity is more suitable for assessment. Hence, a new assessment model of equipment failure degree was constructed. Based on test samples, the PC was evaluated with the proposed model and compared with two traditional methods; the results show that this method is correct.

Impersonal Probability Assessment of Equipment Trip Probability Due to Voltage Sag

The assessment of equipment trip probability due to voltage sag is a complicated matter because of the uncertainties both from voltage sag in power systems and sensitive equipment in customer side. The uncertainties of influencing factors are difficult to determine especially the stochastic distribution of voltage tolerance of equipment. The characteristics of voltage sag are determined by sag severity indices and the probability density function of voltage tolerance of equipment is determined by maximum entropy model. An impersonal assessment method is proposed in this paper. As a case study, PC is simulated and the simulation results are compared with the current methods.

Programming Model and Method for the Customer Friendly Distribution System

In modern grid, the programming model and method of a customer friendly distribution system, a new concept, are proposed in the paper. The influences of construction cost, operating cost and customer losses etc are considered especially the customers potential loss caused by power system disturbances which is evaluated based on the customer satisfaction degree. Maximum entropy and fuzzy based method is used to analyze the compatibility between system disturbance and equipment voltage tolerance. The proposed method has been applied to Garver-6 and the results prove that the planned distribution system is better.

Interval Evaluation of Voltage Sag Magnitude and Frequency in Distribution System

Aiming at the uncertainties of voltage sag evaluation and integrating the interval algorithm to existing stochastic evaluation methods, a interval-based method and approaches for the evaluation of voltage magnitude and sag duration were proposed. In this method, the interval characteristics of reliability parameters of components in distribution system and the variation of customer loading were considered and a interval evaluation method is proposed in order to assess the voltage magnitude and sag frequency in the distribution system based on existing fault location method. For the typical configuration of distribution system, the mathematical model and approaches were researched in detail on the basis of the algorithm of interval power flow. The proposed method was performed on RBTS-2 standard testing distribution system and compared with existing method with certain parameters. It is proved that it needs only one time of interval iteration process. The simulation results indicate that this method is reasonable and effective.

Assessing Method of Voltage Sag Frequency Caused by Transmission Line faults

Fault location on transmission line influences the characteristics of voltage sag at given bus. It is difficult to determine the fault pattern and voltage sag frequency. A new method based on maximum entropy principle was proposed to assess sag frequency synthetically considered different fault types and objective probability distribution of fault location in the power system. The faulty line intervals were derived from analytical approach and sample data moments were used as constraint conditions. The probability value of fault location was determined by maximizing the entropy function. The voltage sag frequency was calculated using the proposed method. Applied in IEEE 30-bus reliability test system, simulation results show that the method is veracious and practical.