This paper proposes a zer o current and zero voltage switching (ZCZVS) PWM Boost full bridge (FB) conve rter. With series inductors, the leading switches can realize zero current swit ching (ZCS) in a wide load ra...This paper proposes a zer o current and zero voltage switching (ZCZVS) PWM Boost full bridge (FB) conve rter. With series inductors, the leading switches can realize zero current swit ching (ZCS) in a wide load range using the energy of the output capacitor. Ma king use of parasitic capacitors of the lagging switches and parallel auxiliary i nductance with the primary winding of the transformer, the lagging switches can realize zero voltage switching (ZVS) under any load. Compared with the ZCS PWM Boost FB converter, the new converter has no current duty cycle loss. Operat ional principle and parameter design are analyzed. Experimental results verify the effectiveness of the proposed converter.展开更多
随着清洁能源规模的不断扩大,可平滑电能输出的混合储能系统(hybrid energy storage system,HESS)逐渐受到广泛关注。双有源桥可实现电气隔离和软开关,常应用于HESS中。为拓宽电压增益范围并降低储能装置侧电流纹波,文中提出一种基于电...随着清洁能源规模的不断扩大,可平滑电能输出的混合储能系统(hybrid energy storage system,HESS)逐渐受到广泛关注。双有源桥可实现电气隔离和软开关,常应用于HESS中。为拓宽电压增益范围并降低储能装置侧电流纹波,文中提出一种基于电流源型双向谐振变换器的HESS拓扑。首先,给出变换器的拓扑及等效电路,分析其开关模态和工作原理,推导出等效电路模型、电压增益表达式及低压侧电流纹波特性。在此基础上,提出一种解耦控制策略,通过调节各储能装置侧全桥的占空比独立控制超级电容和蓄电池的传输功率,并根据功率分配指令动态调整各端口功率占比。仿真结果表明,所提系统能实现各开关管的零电压开通(zero voltage switching,ZVS),在负载切换和功率指令变化时均表现出快速的动态响应和良好的稳定性。展开更多
Single-phase low current grounding faults areoften seen in power distribution system of coal mines.These faults are difficult to reliably identify.We propose a new method of single-phase ground fault protection based ...Single-phase low current grounding faults areoften seen in power distribution system of coal mines.These faults are difficult to reliably identify.We propose a new method of single-phase ground fault protection based upon a discernible matrix of the fractal dimension associated with line currents.The method builds on existing selective protection methods.Faulted feeders are distinguished using differences in the zero-sequence transient current fractal dimension.The current signals were first processed through a fast Fourier transform and then the characteristics of a faulted line were identified using a discernible matrix.The method of calculation is illustrated.The results show that the method involves simple calculations, is easy to do and is highly accurate.It is, therefore, suitable for distribution networks having different neutral grounding modes.展开更多
The way of neutral point to earth via full compensation arc suppression coil can solve the problem of residual current compensation in coal mine power network effectively. Based on the analysis on the grounding curren...The way of neutral point to earth via full compensation arc suppression coil can solve the problem of residual current compensation in coal mine power network effectively. Based on the analysis on the grounding current detection results of Xieqiao coal mine, the conclusion that harmonic component of grounding current is dominated by higher harmonics with complex harmonic sources in coal mine power network system was obtained. The influences of harmonic source type and fault point position on harmonic voltage and harmonic current were analyzed theoretically. The influences of earthed fault feeder detection result and the estimation errors of parameters to earth on residual current compensation were analyzed. A new thought of residual current prediction and the selections of model method and control method were proposed on this basis. The simulation results prove that harmonic amplitudes of zero sequence voltage and zero sequence current are determined by harmonic source type as well as fault point position in coal mine power network, and also prove that zero sequence voltage detection can avoid the unstable problem of coal mine power network system caused by undercompensation of capacitive current. Finally, the experimental device of full compensation arc suppression coil is introduced.展开更多
文摘This paper proposes a zer o current and zero voltage switching (ZCZVS) PWM Boost full bridge (FB) conve rter. With series inductors, the leading switches can realize zero current swit ching (ZCS) in a wide load range using the energy of the output capacitor. Ma king use of parasitic capacitors of the lagging switches and parallel auxiliary i nductance with the primary winding of the transformer, the lagging switches can realize zero voltage switching (ZVS) under any load. Compared with the ZCS PWM Boost FB converter, the new converter has no current duty cycle loss. Operat ional principle and parameter design are analyzed. Experimental results verify the effectiveness of the proposed converter.
文摘随着清洁能源规模的不断扩大,可平滑电能输出的混合储能系统(hybrid energy storage system,HESS)逐渐受到广泛关注。双有源桥可实现电气隔离和软开关,常应用于HESS中。为拓宽电压增益范围并降低储能装置侧电流纹波,文中提出一种基于电流源型双向谐振变换器的HESS拓扑。首先,给出变换器的拓扑及等效电路,分析其开关模态和工作原理,推导出等效电路模型、电压增益表达式及低压侧电流纹波特性。在此基础上,提出一种解耦控制策略,通过调节各储能装置侧全桥的占空比独立控制超级电容和蓄电池的传输功率,并根据功率分配指令动态调整各端口功率占比。仿真结果表明,所提系统能实现各开关管的零电压开通(zero voltage switching,ZVS),在负载切换和功率指令变化时均表现出快速的动态响应和良好的稳定性。
基金Project 50504015 supported by the National Natural Science Foundation of Chinathe Youth Science and Technology Research Program of China University of Mining and Technology (0C060996)
文摘Single-phase low current grounding faults areoften seen in power distribution system of coal mines.These faults are difficult to reliably identify.We propose a new method of single-phase ground fault protection based upon a discernible matrix of the fractal dimension associated with line currents.The method builds on existing selective protection methods.Faulted feeders are distinguished using differences in the zero-sequence transient current fractal dimension.The current signals were first processed through a fast Fourier transform and then the characteristics of a faulted line were identified using a discernible matrix.The method of calculation is illustrated.The results show that the method involves simple calculations, is easy to do and is highly accurate.It is, therefore, suitable for distribution networks having different neutral grounding modes.
基金The financial support from the National Natural Science Foundation of China (No. 51107143)
文摘The way of neutral point to earth via full compensation arc suppression coil can solve the problem of residual current compensation in coal mine power network effectively. Based on the analysis on the grounding current detection results of Xieqiao coal mine, the conclusion that harmonic component of grounding current is dominated by higher harmonics with complex harmonic sources in coal mine power network system was obtained. The influences of harmonic source type and fault point position on harmonic voltage and harmonic current were analyzed theoretically. The influences of earthed fault feeder detection result and the estimation errors of parameters to earth on residual current compensation were analyzed. A new thought of residual current prediction and the selections of model method and control method were proposed on this basis. The simulation results prove that harmonic amplitudes of zero sequence voltage and zero sequence current are determined by harmonic source type as well as fault point position in coal mine power network, and also prove that zero sequence voltage detection can avoid the unstable problem of coal mine power network system caused by undercompensation of capacitive current. Finally, the experimental device of full compensation arc suppression coil is introduced.
