Distributed generation (DG), which is interlinked with distribution system, will inevitably have an impact to system. In the paper, a reliability evaluation method is proposed, which is based on the analysis to the st...
详细信息
Distributed generation (DG), which is interlinked with distribution system, will inevitably have an impact to system. In the paper, a reliability evaluation method is proposed, which is based on the analysis to the structure and power flow of distribution system with distributed generation. First, a new concept, the smallest unit, is put forward for improving the fault traversal networks times. The authors use the depth-first search in data structure to divide distribution system into several the smallest units, and propose the islanding operation mode to increase the reliability of the system. Distribution system will be automatically turned into the islanding operation mode once faults occur. To evaluate quantitatively the reliability of distribution system, Monte Carlo simulation method is used by simulating the running status of distribution system. At last, the calculation results of actual case show that the proposed method is available to evaluate the reliability of distribution system with distributed generation.
The occurrence cause and negative effects of the islanding are presented in the paper, and a new method is presented based on chaos system. This paper applies certain chaos system of its sensitivity to periodical volt...
详细信息
The occurrence cause and negative effects of the islanding are presented in the paper, and a new method is presented based on chaos system. This paper applies certain chaos system of its sensitivity to periodical voltage signal to make its periodical solution yield a dramatic change to detect islanding, existence of the islanding can be identified by discriminating operation status of chaos system. The proposed method is showed to have fast acting and little influence on power quality. The simulations of the proposed method are carried out according to IEEE Std 1547-2003, the simulation results verify its effectiveness.
With the start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate the wheeling charges of large consumers is of vital theoretical and practical significance...
详细信息
With the start of trial operation of direct purchasing electricity for large consumers in China, the method on how to allocate the wheeling charges of large consumers is of vital theoretical and practical significance. An integrated method for allocating the congestion management cost of larger consumers is presented in this paper considering time-of-use (TOU) pricing in congestion period, power supply reliability and the use capacity of the line. Modeling the TOU index, power supply reliability index and use capacity of the line index is proposed. The weights of three indices are determined by interacting between the transmission utility and large consumers based on multilevel models to get comprehensive evaluation indices for all consumers. The integrated indices are used to allocate the cost. Test results show that the method can allocate the congestion cost more reasonably.
The character of the voltage at the end of the opened phase conductor was studied and an improved voltage criterion was proposed to distinguish between transient and permanent faults. The performance of the improved c...
详细信息
The character of the voltage at the end of the opened phase conductor was studied and an improved voltage criterion was proposed to distinguish between transient and permanent faults. The performance of the improved criterion is hardly influenced by the load currents of healthy phases, transmission line length, fault distance and fault earth resistance. For EHV/UHV lines with shunt reactors, the improved method is also effective when a calculated capacitive coupling voltage is employed. Simulation tests show that the conclusions drawn in this paper are correct.
Distributed generation in microgrid is mainly composed of new energy and renewable energy resources. The maximum power point of the PV cell array is various from time to time with the change of circumstance and load. ...
详细信息
Distributed generation in microgrid is mainly composed of new energy and renewable energy resources. The maximum power point of the PV cell array is various from time to time with the change of circumstance and load. The fuzzy control can react to the environment change quickly and keep the photovoltaic system work on its maximum power point all the time. However, the limitation in the fuzzy control itself and the characteristic of self-optimization lead to serious concussion of the system around the maximum power point. Whereas the PID control method is effective in the elimination of concussion and is easy to be realized. To tackle the problem, the fuzzy parameter self-tuning PID control method is adopted in the paper to achieve the MPPT control of PV system. The method can effectively eliminate the concussion around the maximum power point and improve the stability of the whole microgrid; and achieve grid-connected operation with a high power factor in combination with the harmonic elimination PWM control of inverter. Simulation results show that the scheme has merits of simple structure, high power factor and reliable operation, etc. and is worthwhile to be popularized.
powersystem is approaching its limits due to the deregulation of power industry and unavailability of new transmission corridor. However powersystemsecurity assessment is carried out and the operating limits are se...
详细信息
powersystem is approaching its limits due to the deregulation of power industry and unavailability of new transmission corridor. However powersystemsecurity assessment is carried out and the operating limits are set according to the given contingency list which might happen in very rare frequency. In other words, the frequency of fault occurrence and the risk of blackout is varied when the operating condition (load level, status of power equipment, and weather) changes. How can we do the security assessment based on the operating condition to get the best equilibrium between the security and the profit is the focus of this paper. The idea of risk based on-line powersystemsecurity assessment is suggested. A precise calculation method of average failure rates of components is presented. Besides, operating condition based failure rates of components are also analyzed systematically in the paper. The Monte-Carlo simulation demonstrates the viewpoint of the paper.
An improved differential variance bacterial colony chemotaxis (DVBCC) algorithm was presented for the urban power network substation planning. Bacterial colony chemotaxis (BCC) algorithm improves the speed of converge...
详细信息
An improved differential variance bacterial colony chemotaxis (DVBCC) algorithm was presented for the urban power network substation planning. Bacterial colony chemotaxis (BCC) algorithm improves the speed of convergence compared with bacterial chemotaxis (BC) algorithm through the introduction of perception in bacterial colony, and also increases the possibility of a local optimum. DVBCC adopts adaptive control perception scope according to colony' distribution condition, at the same time adds differential variance operator in order to increase the variety of bacterial colony and improves its robust and global optima searching capability. In this paper completed economy of substation optimization planning of 110 kV and 220 kV voltage grade in urban power network was taken as objective function, and factors of geographical effect was considered. The results indicated that DVBCC algorithm outperforms BCC and particle swarm optimization (PSO) algorithms in solving substation planning problem and the proposed model has good economy and practicability.
Frequency spectrum leakage caused by synchronous error in nonsynchronous sampling system reduces the accuracy of frequency spectrum analysis and harmonic measurement. A sampling frequency self-adapting software algori...
详细信息
Frequency spectrum leakage caused by synchronous error in nonsynchronous sampling system reduces the accuracy of frequency spectrum analysis and harmonic measurement. A sampling frequency self-adapting software algorithm in protection relay measure and controlsystem is presented in this paper. The sampling frequency self-adapting software algorithm obtained the actual signal frequency fairly accurately by calculating the sampling data from protection relay measure and controlsystem, and adjusted the sampling time interval according to the frequency which was calculated by the self- adapting software algorithm. The process of the software algorithm design is introduced, simulation and analysis are discussed. The results of simulation and analysis show that this software algorithm can improve the accuracy of frequency spectrum analysis and harmonic measurement for powersystem signal, and the algorithm can be realized easily.
With increasingly proportion of distributed generation (DG) in the powersystem, traditional powersystem planning has new challenges and demands. The necessity for flexible electric system, changing regulatory, energ...
详细信息
With increasingly proportion of distributed generation (DG) in the powersystem, traditional powersystem planning has new challenges and demands. The necessity for flexible electric system, changing regulatory, energy savings and environmental impact are providing impetus to the development of DG. Itpsilas critical that the powersystem impacts be assessed accurately so that DG can be applied in a manner that avoid degradation of power quality, assure reliability and control of the utility system. In recent years, wind energy has become an important part of DG in many countries and its importance is continuing to increase. This paper focuses on the capacity planning of wind power stations, considering technical constrains, like feeder voltage profile, harmonic distortion etc, and establishes a model based on improved genetic algorithm to solve, which produces chaotic initial population to start iteration to raise algorithm for the speed and accuracy. Through simulation and calculation, the two sets of results are compared, and the feasibility of the above model and algorithm is demonstrated.
A nonlinear control strategy based on Lyapunov stability theory is proposed to satisfy stability requirements under the external interference of the uncertainty condition. Due to the nonlinear of the DC voltage differ...
详细信息
A nonlinear control strategy based on Lyapunov stability theory is proposed to satisfy stability requirements under the external interference of the uncertainty condition. Due to the nonlinear of the DC voltage differential equation for VSC-HVDC, the control of DC voltage is transformed to the control of the q-axis component of AC current fundamental component. Suitable Lyapunov functions are adopted according to the difference between reference value and actual value. Two nonlinear control inputs to the converter are obtained based on Lyapunov stability criterion. Due to linear of active power differential equation, active power is controlled based on traditional proportional integral (PI). The simulation results performed on PSCAD/EMTDC verify the feasibility of the control strategies effectively under a short time (0.05s) single phase to ground fault in two terminal AC systems of VSC- HVDC.
暂无评论