The paper describes the use of multi-terminal HVDC transmission system based on voltage source converter (VSC) (VSC-MTDC) for connecting doubly fed induction generator (DFIG) based wind farms over long distance. The o...
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The paper describes the use of multi-terminal HVDC transmission system based on voltage source converter (VSC) (VSC-MTDC) for connecting doubly fed induction generator (DFIG) based wind farms over long distance. The operation principles between DFIG and VSC-MTDC of the proposed system are described. Stator flux oriented vector control technology is used to execute AC excitation for DFIG rotor, then independent control of active and reactive power is realized and electricity generation by capturing maximal wind energy is also obtained. The control objective of rectifiers is delivering the generated power from the wind farms to the DC network instantaneously and to keep AC voltage at wind farm bus constant. The control objective of inverters is receiving the power from the DC network and to keep DC voltage constant, and the multi VSCs are controlled coordinately, the relevant mathematical model was established. The parameters optimization based on simplex algorithm and objective function are used to get suitable PI control parameters of VSC-MTDC. Interactions between DFIG and VSC-MTDC link are investigated and simulations performed in PSCAD/EMTDC to verify the proposed control strategy.
In this paper, concerning the limitations of this method which can not meet the current needs of the development of large-scale power system, a new electromechanical transient simulation model based on dynamic equival...
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ISBN:
(纸本)9781424480807
In this paper, concerning the limitations of this method which can not meet the current needs of the development of large-scale power system, a new electromechanical transient simulation model based on dynamic equivalent is proposed. It develop a new vision for the electromechanical transient and electromagnetic transient hybrid simulation, which presents the application of dynamic hybrid simulation equivalent in hybrid simulation. Two cases are studied, electromechanical Simulation of IEEE14 nodes system, and hybrid simulation of electromagnetic transient and electromechanical transient on RTDS was developed, in the condition that the electromagnetic transient part is an actual DC system. The simulation results show that dynamic equivalence presented in the paper is valid and effective. On this basis, hybrid simulation based on dynamic equivalence is realized, thereby expanding the simulation size of AC system.
Previous blackouts demonstrate that the safe and stable operation of backbone-grid plays a key role in preventing large-scale blackouts caused by cascading failures. Based on binary particle swarm optimization, a nove...
Previous blackouts demonstrate that the safe and stable operation of backbone-grid plays a key role in preventing large-scale blackouts caused by cascading failures. Based on binary particle swarm optimization, a novel method is proposed to identify the backbone-grid in power grid. First, the concept of the backbone-grid is defined for mathematically describing the critical lines and important topology structure which are crucial for power system to prevent the blackout caused by cascading failures. On this basis, the problem of exploring backbone-grid is further formulated as a mixed integer nonlinear programming problem which is to be solved with binary particle swarm optimization. The problem just needs to be optimized only once. The backbone-grid essential to the safe and stable operation of power grid can be obtained. Simulation on IEEE RTS-79 system verifies that the proposed method can identify backbone-grid with high computational efficiency.
This paper briefly introduces the first project in China using a Static Var Compensator (SVC) to damp Sub-Synchronous Oscillations (SSO) excited by fixed series compensation. Since the SVC function of this project is ...
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This paper briefly introduces the first project in China using a Static Var Compensator (SVC) to damp Sub-Synchronous Oscillations (SSO) excited by fixed series compensation. Since the SVC function of this project is to damp SSO, it is necessary to study its side-effects on the ac system when damping SSO. A real time digital simulator (RTDS) model for this project is developed and a closed-loop test platform is established, which is comprised of an RTDS and a physical SVC controller. Based on the platform, this paper studies the side-effects of the SVC including transformer overload, ac system transient stability and relay malfunction. Simulation and theoretical results show that all these side-effects are acceptable and will not effect the operation of the ac system.
With the expansion of the power systems, DC power transmission has been increasingly applied in interconnection of grids. The determination of Available Transfer Capability (ATC) for the AC/DC transmission systems is ...
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With the expansion of the power systems, DC power transmission has been increasingly applied in interconnection of grids. The determination of Available Transfer Capability (ATC) for the AC/DC transmission systems is significant to the system planning and operation. So far, most studies have been focused on ATC determination for AC transmission systems, few are on the AC/DC system ATC determination. In this paper, the ATC determination model for the AC/DC systems is proposed. Multi-terminal DC (MTDC) system is considered in ATC computation model. Conventionally, the power injection variations are determined by load variations and generation dispatch, both of them are nonlinear. To model these nonlinear variations, an alternate iterative continuation power flow (CPF) method with multiple load variations and generation economic dispatch patterns is presented to solve the proposed model. The MTDC system configurations, the converter control strategies and the transformer's tap adjustment strategies are incorporated to this modified CPF algorithm. The modified IEEE 30-bus test system is used to verify the presented approach.
In order to overcome some disadvantages of the conventional adjacent matrix method, the relationship between the elements of the adjacent matrix and the connected routes among nodes is analyzed as the fundamental intr...
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ISBN:
(纸本)9781424480807
In order to overcome some disadvantages of the conventional adjacent matrix method, the relationship between the elements of the adjacent matrix and the connected routes among nodes is analyzed as the fundamental introduction. Subsequently, the graphic characteristic of the main electrical connection in power plant or substation is extracted as three types: single branch, two branches in-parallel and multi-branches in-parallel, and an unified principle for the formulation of connected routes among arbitrary two nodes in wiring connection is also proposed as the cornerstone for the novel method. Thirdly, a novel method of substation configuration is established based on the set of connected routes among arbitrary two nodes, and by mean of taking the route state as variables, the value of connected routes set is used to directly determine the element in corresponding place of the adjacent matrix. Finally, the example results show that the new method is able to finish the original topology analysis and track the state status of switches more accurately and rapidly.
The issue of power quality in the distribution system is always in sense of the concern. With the high penetration of distributed generation (DG) currently, it tends to be more complicated. This paper presents a new a...
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The faults in electric power system can not be completely avoided. When power system operates from normal state to failure or abnormal operates, its electric quantities may change significantly. Our researches indicat...
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The faults in electric power system can not be completely avoided. When power system operates from normal state to failure or abnormal operates, its electric quantities may change significantly. Our researches indicate that the variable with the biggest coefficient in principal component usually corresponds to the fault. Therefore, utilizing real-time measurements of PMU, basing on principal components analysis technology, we have completed the fault location of electric power system. Of course, because of the complexity of different types of faults in power system, there still exists enormous problems need a close and intensive study.
Distributed generator (DG), with its flexible power generation, environment-friendly advantages has been more widely used in distribution system, which has brought some influence to the traditional distribution networ...
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ISBN:
(纸本)9781424480807
Distributed generator (DG), with its flexible power generation, environment-friendly advantages has been more widely used in distribution system, which has brought some influence to the traditional distribution network reliability evaluation. In this paper, two different models for conventional DG and wind turbine generator (WTG) are established for reliability evaluation, based on different energy sources and operation characteristics. This paper presents a technique to obtain the WTG output using statistical wind speed information, considering to the intermittent characteristics of wind power. On this basis, an improved minimal cut set algorithm is proposed to evaluate the reliability of distribution network with DG. Finally, the simulation of a typical distribution line with DG verifies the validity of this method.
This paper theoretically analyzes the compound control apparatus for current quality compensation which is designed as differentiation cascaded H bridge type with two modules: fundamental-frequency module and high-fre...
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ISBN:
(纸本)9781424480807
This paper theoretically analyzes the compound control apparatus for current quality compensation which is designed as differentiation cascaded H bridge type with two modules: fundamental-frequency module and high-frequency module. The detection algorithm calculates the harmonic current and fundamental-frequency current of the load current which serve as the command current. For the purpose of eliminating the steady periodic error of system and improving the tracking accuracy of the compensation current, PI and repetitive controller in parallel is introduced as a advanced current control method. A detailed analysis and design for the high-frequency module is presented based on frequency characteristic and steady state. A 10kV system simulation model based on PSCAD/EMTDC is built to analyze the control strategy. Finally, the experimental results illustrate that the proposed control strategy is feasible and provide a reference for the 10kV industrial apparatus.
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