Based on the synthetic control of microgrid, a flexible power electronics interface is developed in this paper. Considering distributed generation types and storage devices, different control strategies are adopted in...
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Based on the synthetic control of microgrid, a flexible power electronics interface is developed in this paper. Considering distributed generation types and storage devices, different control strategies are adopted in controller design for different distributed generation units. The interface comprises a couple of back-to-back VSC converters, and exports variable active power and reactive power in order to maintain the power balance inside the microgrid. Apparently, the interface separates the microgird from the AC grid, prevent harmonic component transmitting from one side to the other side and control the active power precisely flowing between microgrid and main grid. Besides, it's also in charge of reactive power compensation and keeping the microgrid voltage stable. Simulation results can approve its superiority and validity comparing with direct connection.
The value setting of the traditional distance protection has become very difficult for the distribution system with distributed generators (DGs) owing to the randomness of the DG output power. This paper proposes a ne...
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ISBN:
(纸本)9781424480807
The value setting of the traditional distance protection has become very difficult for the distribution system with distributed generators (DGs) owing to the randomness of the DG output power. This paper proposes a new adaptive distance protection scheme to solve this problem. Firstly, on the basis of the connected point of DGs, the protected feeders are divided into different zones, with adaptive distance protection configured at the upstream side of DG. Then, based on a fault characteristic analysis of the distribution system with DG, the adaptive distance protection scheme for the distribution system with DG is studied to solve this problem. The results show that this scheme can automatically calculate the settings according to the operation mode and the output power of DG with no need for communication. Compared with the traditional adaptive protection scheme, the performance of this method is greatly improved. Simulation results on a 10 kV distribution system have verified the validity of the scheme proposed.
The problem of current waveform distortion because of dead-time inserted in power electronic applications is analyzed and researched in this paper, and the equivalent voltage source model is set up in to analyze the l...
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The problem of current waveform distortion because of dead-time inserted in power electronic applications is analyzed and researched in this paper, and the equivalent voltage source model is set up in to analyze the low frequency harmonic voltage because of dead-time effect. The control strategy of harmonic injection is proposed to compensate the current distortion due to dead-time effect. Firstly, obtains the application output current amplitude and phase of mainly harmonic current by Fourier transform, then calculates the compensation instructive voltage according to the connected inductor and dc voltage. Based on H-bridges cascaded static synchronous compensator (STATCOM), the experiment on a STATCOM based on digital signal processor (DSP) and (Field Programmable Gate Array) FPGA is implemented. The simulation and experimental results show that the proposed method is feasible and efficient to compensate the current distortion.
In this paper, control strategies of VSC-HVDC aiming to improve the ability of fault ride through of the VSC-HVDC system under serious asymmetric fault at the receiving side was studied. On the basis of DQ decoupling ...
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ISBN:
(纸本)9781424480807
In this paper, control strategies of VSC-HVDC aiming to improve the ability of fault ride through of the VSC-HVDC system under serious asymmetric fault at the receiving side was studied. On the basis of DQ decoupling control scheme, two additional fault control modules are proposed based on positive and negative sequence detecting technology. One is based on negative sequence voltage compensation, and the other is based on oscillating active power elimination. Simulations are carried out in PSCAD/EMTDC to verify the validity of the proposed control strategies.
Wavelet energy entropy has a small calculation amount, and it has a unique sensibility to slightly change of the dynamic system parameters. This paper presents a novel transient-based protection for power system EHV t...
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Wavelet energy entropy has a small calculation amount, and it has a unique sensibility to slightly change of the dynamic system parameters. This paper presents a novel transient-based protection for power system EHV transmission line, which employ the value of wavelet energy entropy to reflect the different energy distribution between internal and external fault. The basic principle of the protection is according to the attenuation effect of busbar capacitance and line trap to the high-frequency components. Simulation results show that the proposed protection criterion has high sensitivity and reliability, and capable of providing correct responses under conditions of different fault types, positions, path resistances, and inception angles.
The topology characteristics of the nodal matrix in power system analysis and the adjacent matrix in graph respectively has been proved to be absolutely identical. According to this feature and modification principles...
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The topology characteristics of the nodal matrix in power system analysis and the adjacent matrix in graph respectively has been proved to be absolutely identical. According to this feature and modification principles of the nodal impedance matrix, a new tracking algorithm for the state change of the circuit breaker has been built based on the general multiplication and general addition operations. The new algorithm is able to reduce the computation burden than the traditional way. Finally, the text example has validated the efficiency of the novel tracking algorithm in substation configuration.
In the paper, the principle of speed governor of synchronous machine is discussed firstly. Based on this, mathematical models of the speed governors of BPA and PSS/E are compared to find the corresponding relationship...
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In the paper, the principle of speed governor of synchronous machine is discussed firstly. Based on this, mathematical models of the speed governors of BPA and PSS/E are compared to find the corresponding relationship of the speed governor models between BPA and PSS/E. The corresponding models have been validated by simulation of a single machine infinite bus system and the quantitative analysis of conversion error between models is given. The results indicate that the corresponding speed-governor models of BPA and PSS/E have good consistency, so conversion of corresponding speed-governor models between BPA and PSS/E can be entirely achieved for transient stability analysis.
Microgrid, as a new effective way for large scale new energy and renewable energy power generation systems connected to the grid, injects new vigor into the power system. Focusing on the characteristics of P-f (active...
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Microgrid, as a new effective way for large scale new energy and renewable energy power generation systems connected to the grid, injects new vigor into the power system. Focusing on the characteristics of P-f (active power versus frequency) droop and Q-V (reactive power versus voltage) droop, on the basis of analyzing the variable slope coefficient of droop characteristic, a droop control method of microsources based on divided self-adjusting slope coefficient is proposed in this paper. By calculating the quantity of the load fluctuation, this control method dynamically adjusts the active and reactive power maximums of inverters in the range of the inverter ratings to change the slope coefficients of droop curves. The aim of this method is to decrease the deviation of the frequency and voltage magnitude of the microgrid bus effectively. The simulation result verifies the correctness and feasibility of this control method.
With the deepening reform to power industries, power systems are going to gradually open the demand side and the power consumers have to face the changes of their role in the market, and make a preliminary long-term f...
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With the deepening reform to power industries, power systems are going to gradually open the demand side and the power consumers have to face the changes of their role in the market, and make a preliminary long-term forecasting for the electricity prices. In order to consider the relations between the spot market and the long-term contract market, this paper builds a multi-electricity price grey model to comprehensive forecast the prices of the 2 markets; further researches the structure of the background value, and improves the multi-electricity price grey model; and introduces the residual error, the related grade, the mean variance ratio and the little probability of error as test indexes. The test results show that the multi-electricity price grey forecasting model and its improved model have better accuracy, and the improved model has stronger adaptability and extends the application range.
As an important component of distribution network, micro-grid is the necessarily development trend for future. Micro-grid has greatly improved the random problems of distributed generation (DG). However, DGs, the powe...
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As an important component of distribution network, micro-grid is the necessarily development trend for future. Micro-grid has greatly improved the random problems of distributed generation (DG). However, DGs, the power electronic equipments inevitably bring about power quality problems, especially voltage flicker and harmonics. This paper tries to study the operating regulations of micro-grid in order to find out the generating mechanism and propagation characteristic of power quality problems. Taking the photovoltaic (PV) system for an example, the micro-grid simulation model has been set up. The experiments show that an appropriate control strategy coordinating every part can improve the power quality of micro-grid greatly. This paper finds out the factors affecting power quality and their harm degrees, explaining the reasons of power quality problems. Coordinating every unit, this paper set up an optimal control strategy and proper parameter settings, trying to improve power quality of micro-grid to the largest extent.
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