This paper proposed a novel hybrid power converter topology based on cascaded H-bridge (CHB) and matrix converter (MC) in order to improve the performance of the conventional energy management systems in EV/PHEV appli...
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This paper proposed a novel hybrid power converter topology based on cascaded H-bridge (CHB) and matrix converter (MC) in order to improve the performance of the conventional energy management systems in EV/PHEV application. The power demand by the load is supplied by the generator and batteries, which are connected to the primary winding of the medium frequency transformer (MFT) by the matrix converter and the cascaded H-bridge respectively. The power transfer between the sources and load can be controlled and isolated by using the MFT. The cascaded H-bridge, as the energy control unit, can be used to balance the voltage/SOC of battery packages individually, significantly improve the modularity, stability and safety of EV system.
With the continuous growth of the installed capacity of wind power in China, the ability of integrating wind power becomes the bottleneck of its development. The electricity generation is determined by the heat supply...
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This paper focus on the fault characteristic by experimental research. A test rig is built for the direct driving stall fix-pitch horizontal axis wind turbine. 8 signals are collected by the experiment system, includi...
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This paper focus on the fault characteristic by experimental research. A test rig is built for the direct driving stall fix-pitch horizontal axis wind turbine. 8 signals are collected by the experiment system, including wind speed, rotor rotational speed, shaft torque, the output electric power, vertical and horizontal vibration displacement of main shaft, vibration acceleration of the front bearing pedestal and the back bearing pedestal. 11 common wind turbine faults are researched by experiment. These faults are rotor mass imbalance, pneumatic asymmetry, airfoil changed, yaw fault, shaft horizontal misalignment, shaft vertical misalignment, front bearing pedestal looseness, rear bearing pedestal looseness, front bearing outer ring fault, front bearing inner ring fault, and front bearing roller fault. Several signal analysis methods, which are waveform analysis, orbit analysis, amplitude domain analysis, frequency domain analysis and envelope spectrum analysis, are adopted to extract characteristics from vibration signals. The influence on output power and vibration characteristics of these faults is presented by comparing with normal operation. The findings can be used to guide wind turbine fault diagnosis in engineering applications.
Due to the physical limitations of the generator, the vibrations in a shaft bearing may be amplified at a certain operation regimes, the prohibited zones are needed which leads to a disjoint powergeneration instead o...
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Surge Impedance Relay(SIR) is applied to DC system. Characteristics of SIR in DC line are analysed. A DC SIR algorithm implementing wavelet transform applied to HVDC line protection is proposed. The feasibility of DC ...
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ISBN:
(纸本)9781849198349
Surge Impedance Relay(SIR) is applied to DC system. Characteristics of SIR in DC line are analysed. A DC SIR algorithm implementing wavelet transform applied to HVDC line protection is proposed. The feasibility of DC SIR is verified and the performance of DC SIR is simulated and analysed.
The signal of travelling wave has the merit of immunity to system oscillation, transition resistance, CT saturation and the neutral point operation modes;it has been widely applied in field of fault detection and prot...
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ISBN:
(纸本)9781849198349
The signal of travelling wave has the merit of immunity to system oscillation, transition resistance, CT saturation and the neutral point operation modes;it has been widely applied in field of fault detection and protection. Especially in isolated neutral grounded wind farm distribution network, the algorithm using multiple-bay travelling wave's information can exclusively achieve the fast fault feeder selection and tripping. However, travelling wave sampling frequency tends to reach 500 to 1000 times of that in algorithms with power frequency signal. The direct of travelling wave sampling data sharing in process bus would produce the communication block, and weaken the security of whole substation automation. To solve this problem, the performance of communication in process bus is theoretically analyzed and simulated in this paper, the communication requirement of travelling waves is quantified, and then a feasible scheme is proposed with data pre-processing and fault characteristic abstraction moving forward into the merging unit. simulations prove its validity. The work in paper can promote the wide application of travelling waves in substation based on IEC61850.
The distribution network detection devices are generally using two kinds of instrument current transformer (ICT), of which one is used to transform the travelling wave and transient signals, while the other is used to...
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ISBN:
(纸本)9781849198349
The distribution network detection devices are generally using two kinds of instrument current transformer (ICT), of which one is used to transform the travelling wave and transient signals, while the other is used to transform the power frequency signals. Such scheme is neither necessary nor economical. This paper analyses the influences of sampling resistance, stray capacitance and magnetizing inductance on the frequency characteristic of ICT. Considering that fault zero sequence transient current has big transient component and small power frequency component, an ICT with wide band frequency accuracy has been chosen. Practical experiments have been done. The technical parameters given by the instrument factory are only within 20-20kHz. The characteristics in higher frequency are seldom reported due to the lack of test means. The experiments in this paper is based on the transient tester instrument and current amplifiers developed by our laboratory, which can output wide frequency band current within 20Hz-100kHz up to 50A. Experiment shows that, the predicted results were in good agreement with the measured ones.
In deregulated electricity markets, generation companies with the aim of maximum revenue need to provide trading strategies to the electricity trading market, which contributed to a self-scheduling model. When conside...
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Fan mill is an important device in thermal plants, which supply coal power to boiler. Crack failures recently occurred in pulverizing wheels of fan mills in a power plant in China. The cracks happens in quite a few pu...
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Fan mill is an important device in thermal plants, which supply coal power to boiler. Crack failures recently occurred in pulverizing wheels of fan mills in a power plant in China. The cracks happens in quite a few pulverizing wheels and they affect the normal operation. To find out the root cause of the cracks, Finite Element Analysis (FEA) of the pulverizing wheel is carried out in this work. The assembly with real dimensions is modelled to calculate the concentrated stress and strain with centrifugal load, driving load, and operational temperature taken into account. Contact effects are included in the finite element model as well as nonlinear material property. Based on the analysis, the crack causes are determined: (i) the initial stress exceeds the yield limit in normal operational condition, resulting low safety coefficient;(ii) the stress increases significantly in the worn pulverizing wheel, where the risk of failure is greatly increased.
This paper presents a new control strategy for three-level neutral point clamped (NPC) pulse width modulated (PWM) rectifier without power source voltage sensors. The relationship between instantaneous power and volta...
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