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.
As a clean renewable energy, wind energy draws more and more attention around the world. In case of high wind speed or low speed but substantial installed wind power capacity, wind turbine generators (WTGs) will take ...
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As a clean renewable energy, wind energy draws more and more attention around the world. In case of high wind speed or low speed but substantial installed wind power capacity, wind turbine generators (WTGs) will take the place of traditional power plant partly. Under the circumstance, the transient stability will change. Therefore, in this article, the synthetical dynamic model of WTG is introduced first, and on the basis of it, the article focus on the comparison of transient stability characteristic between wind farm based on double fed induction generator (DFIG) and tradition power plant with the same capacity. Take an actual grid including wind farm as an example. The power factor of the wind farm is 1.00 and keeps constant during steady state. Under this control mode, the reactive power between wind farm and the grid is zero. The study indicates that, in this system, when the scale of wind farm connected is below 12.3%, the transient stability is better than synchronous generator integrated with the identical capacity. And with the increasing capacity of wind farm, the fault critical clearing time (CCT) is shorter, and it lasts longer time during the recovery. When the scale of wind farm exceeds 12.3%, the terminal voltage of point of common coupling (PCC) is below 0.95 p.u. The stability is inferior to the synchronous generator connected. Under the circumstance, the stability will be enhanced through adding the reactive power compensative device.
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.
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.
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.
Wavelet energy entropy has a small calculation amount, and it has a unique sensibility to slightly change of the dynamicsystem parameters. This paper presents a novel transient-based protection for powersystem 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 dynamicsystem parameters. This paper presents a novel transient-based protection for powersystem 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 powersystem 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 powersystem 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 powersystem. 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 powersystem. 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.
Ice accretion on high voltage power lines is a severe problem for power network and it can cause insulator flashover, wire breakage and tower falling down. In the present work, different hydrophobic surfaces were depo...
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Ice accretion on high voltage power lines is a severe problem for power network and it can cause insulator flashover, wire breakage and tower falling down. In the present work, different hydrophobic surfaces were deposited on aluminum conductor and the ice accretion process on these hydrophobic aluminum surfaces were studied in an artificial climatic chamber. The superhydrophobic aluminum surface can largely prevent ice accretion on the surface except a few ice growth at the edge of the aluminum conductor when it was sprayed by supercooled water under low temperature. While the hydrophobic aluminum surface deposited with a coating of RTV did resist ice formation in a short time but was covered by a intact layer of ice after being sprayed for 30 min at the same condition. The common hydrophilic aluminum conductor has been covered by a intact layer of ice in no more than 1 min spraying time. This is resulted from the different hydrophobicity of the aluminum conductor. As the superhydrophobic conductor has an excellent hydrophobicity and water droplet can not adhere on the surface stablely, which result no ice crystal to be formed on the aluminum surface. However the hydrophobic RTV coated aluminum conductor has a water sliding angle larger than 90°, which result the formation of ice layer gradually. The hydrophilic aluminum can be wetted by water droplets easily, which result the layer of ice to be formed quickly when it was sprayed by supercooled water under low temperature.
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