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This paper studies the use of static synchronous compensator (STATCOM) for wind farms integration based on DFIG, and proposes a reactive power cooperative control strategy for the wind farm combined with STATCOM. A whole dynamic model for variable-speed constant-frequency wind energy system and the STATCOM are established in the PSCAD/EMTDC environment. On the basis of this model, the reactive power limit of DFIG wind power generation system based on the power relationships of overall system is calculated. Then optimization cooperative control strategy of the DFIG is proposed. Finally, simulation studies are carried out to examine the dynamic performance of the PCC with and without STATCOM. Results show that the wind farm with STATCOM cooperative compensate control strategy optimizes the reactive power and improves the dynamic performance of the wind farm when the system is in fault.

Anti-islanding method with reliable protection and reasonable control run an important role in grid connected PV power generation system. The detection and calculation of real and reactive power are the bases of many inverter resident passive and active islanding detection method (IDM). As well as the detection and calculation of real and reactive power also concern with the inverter control of grid connected PV power generation system. In this paper, considering instantaneous voltage and instantaneous current are periodic function about time, think of it in terms of periodic function space to define the inner product and norm, Hilbert space based power theory is proposed. Real power, reactive power and apparent power in Hilbert space based theory are defined. This proposed Hilbert space based power theory provide a novel view for the protection, islanding detection and control of grid connected PV power generation system.

Passive islanding detection method is an important concern for grid connected photovoltaic (PV) power generation system due to personnel and equipment safety. Over/Under Voltage Protection (OVP/UVP) and Over/Under Frequency Protection (OFP/UFP) are basical inverter resident passive islanding detection method (IDM) for detecting an islanding condition by monitor parameters in point of common coupling (PCC) such as voltage amplitude and frequency and then cause the inverter to shut down when there is sufficient transition from normal specified conditions. The real and reactive power equations and Non-Detection Zone (NDZ) of OVP/UVP and OFP/UFP methods for grid connected PV system are derived and analyzed in this paper. Analyses show that the behavior of the system at the time of disconnection will depend on the imbalance power at the instant before the switch opens to form the island, these results also indicate the NDZ of OVP/UVP and OFP/UFP methods is considerable large and the reaction times for these protective methodologies may be variable or unpredictable.

In this paper, taking the doubly fed induction generator (DFIG) wind turbine as the research object, an electromagnetic transient simulation model is established in PSCAD/EMTDC simulation environment to analyze the active power and reactive power regulation capacity of DFIG wind turbine. Under different wind speed, maximum power point tracing (MPPT) control is implemented to ensure the optimum active power output, meanwhile the reactive power limits are calculated and combined with reactive power requirement of local load or the grid to determine the reactive power output. It can achieve operation optimization by making full use of a DFIG wind turbine capacity of the flexible power regulation.

In this paper, with analyzing the existing questions of conventional nine-area voltage and reactive power integrated control method, a new fuzzy control logic based dynamic reactive power boundary substation voltage and reactive power integrated control method is proposed. The fuzzy logic control strategies of this method can finish the decoupling control of voltage and reactive power in tight coupled zone to improve the control performance, dynamic reactive power boundary related to the system voltage can preferably adapted to the load characteristics. The system structure, fuzzy logic control rules and membership function of the proposed method are introduced. Simulation results and practical operating data have proved that this approach shows better robustness and performance compared with the conventional nine-area control method, it can reduce the adjust times of transformer tap and capacitors effectively and increase the service life of the transformer tap changer and capacitors switch.

In some regional grids in China, wind power penetration will increase rapidly because of the abundant wind resources in those areas and the government policy impetus. As more and more attention is paid to the increase of wind-turbine farms, a number of problems should be investigated in more detail. Among these problems, the voltage stability of wind farms implemented with induction generators becomes necessary, especially when operating into a weak connection. Based on a actual regional power grid in China, this paper presents a detailed simulation analysis of the impact of large scale wind farm on voltage stability (dynamic voltage stability) of power system under a short-circuit fault performed by PSCAD/EMTDC. Factors influencing voltage stability of the local grid interconnected with the wind farm are analyzed, and measures to improve the voltage stability of power grid are proposed.

Flexible AC transmission systems (FACTS) and their controllers are of great interest today. FACTS controllers can offer great opportunities in modern power system, allowing better and safer operation of the grid. Their technical benefits are very well acknowledged, but there are some factors limiting the widespread of this technology: a) lack of a comprehensive consideration of FACTS for multiple operational problems and operational conditions, b) lack of economic assessment of FACTS projects for utilities and transmission entities [1] c) lack of a clear understanding of the options of devices and their configurations [1], and most importantly d) the high degree of uncertainty associated with the transmission system on the time scale that is needed to assess this kind of long-term projects. This paper gives a brief introduction of various FACTS devices and their controllers, main research methods. We mainly provide a survey of FACTS' economic assessment method proposed so far. We conclude that there is a huge literature body of technical benefits associated with FACTS targeting on single operational problems, but limited work on addressing their practical application considerations, and economic evaluation, offering great research opportunities.

The comparison between Hilbert space based power theory and three other power theories including traditional power theory, instantaneous power theory put forward by Akagi and Fryze power theory are analyzed in this paper. The consistency and difference are indicated in several different aspects: physical meaning, mathematical concept and the derivation of expressions. Analyses shows that traditional power theory can be regarded as a special case of Hilbert space based power theory, in other words, Hilbert space based power theory can be regarded as the generalization of traditional power theory. Fryze power theory is in accordance with Hilbert space based power theory in single-phase nonsinusoidal system, instantaneous power theory is in accordance with Hilbert space based power theory in three- phase symmetrical system without zero-sequence component. The definition of active current in Hilbert space based power theory is different from it in instantaneous power theory in three-phase system.

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 control system 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 control system, 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 power system signal, and the algorithm can be realized easily.

This paper presents a new method of modeling and simulation for relay protection by using a DEVS-based toolkit named CD++. With this toolkit, the modeling of relay will be more easy and straightforward. We takes the digital three zones distances protection as the example, studies the approach of ideal protection relay modeling, and also validate the validity and feasibility of the model through analysis.

Along with the enlarging of electric network, the problems which longtime computing and slow rapidity of convergence become serious in the electric network computing. In order to cope with the problems, this article utilize distributed parallel optimization model which based on sub-area division and auxiliary problem principle (APP) to solve multi-region active load in economic dispatch. We regard the virtual generator as verity generator, and deduce its cure of consumption characteristic. Finally, we give a simulation of example, the simulation shows that this method is fast and has a good convergence property.

In this paper, a fuzzy excitation controller based on wide-are measurement system (WAMS) is built, in which the voltage deviation and its rate are introduced as the input of main-controller, while the deviation and corresponding rate of local generator's frequency and center-of-inertia frequency are acted as the input of the second controller to indicate the global information . The multi-machines system model is firstly set up with MATLAB/PST. Then the digital simulation is conducted to compare the influences of PID excitation controller and fuzzy excitation controller based on WAMS on the transient stability. Results show that applying the fuzzy excitation controller proposed in this paper, the ability to endure serious disturbances can be strengthened and transient stability can be improved. (5 pages)

This paper studies the optimal PMU placements based on incomplete observability of power systems, including the optimal placement methods based on unobservability depths and PMU phase installation, which are both realized by the simulated annealing algorithm. And sensitivity is taken into account during the process of seeking the optimal solutions, which can guarantee that the least number of PMUs is used in optimal placements and as more as PMUs are placed on buses with high sensitivity at the same time to collect high-accuracy network dynamic data. (6 pages)

The events in power systems are an important dynamic behavior, and there is no good approach of modeling and analysis at all times due to the complexity of its behaviors. In this paper, a mathematic definition of the event is given after analyzing various power system events, and also gives a model framework of power system events, which is based on formal language theory. The hybrid dynamic behavior between power system discrete control actions and physical system is analyzed by using this framework, and a cascading event sequence occurred in the 8.14 blackout is used as an example to discuss the controllable of events. Then, the synthesis of supervisor of power system discrete events is also discussed.

In this paper, power system fault diagnosis based on Petri nets and coding theory is further studied. Previous research work is briefly reviewed. Characteristics of Petri nets model in power system fault diagnosis and identification are demonstrated in detail, also a fast model revision algorithm of power components is proposed, which makes the scheme more applicable to large-scale power network. The method is tested in the IEEE 118-bus power system and simulation results show that the suggested approach is accurate by using of error correction theory, model revision is easy, fast when power network is expanded or topology is changed, which makes the encoded Petri nets method more applicable in real power system.

In this paper, coding-based methodology for faults monitoring of discrete event systems is applied to large-scale power system. Using Petri nets and coding theory to perform the fault diagnosis is further studied. Previous research work is briefly reviewed, including faults' mapping (hidden failures are considered), application of encoded Petri net to power system FDI (fault diagnosis and identification), construction of generator matrix. FDI in large-scale power networks is demonstrated in detail, especially on fast model revision algorithm of power components and an auxiliary hybrid diagnosis method. A simple scheme then is provided. The method is tested in the IEEE 118-bus power system and simulation results show that the suggested approach is accurate as combined with error correction theory, model revision is easy, fast in the case of power network expansion or topology change, which significantly improves the application potential of encoded Petri nets method in real power system.

In this paper, coding-based methodology for faults monitoring of discrete event systems is applied to electric power system. Using Petri nets and coding theory to perform the fault diagnosis is further studied. One feeder of the substation is modeled by Petri net using real time discrete events, and redundant places are introduced to form structure redundancy and facilitate fault diagnosis. Based on the previous work, the feeder's all possible failures are analyzed and a new method to model these failures is given. Then parity check from coding theory is used to form an encoded Petri net, therefore faults can be detected and identified through error syndrome. Method to construct important matrix, generator matrix, is presented. The simulation is simple, fast and shows very high accuracy, as combining with error correction theory. The result of simulation shows that the scheme has good performance in real-time substation fault diagnosis.