脉冲负荷对舰船综合电力系统的冲击作用研究

综合电力系统可以为舰载高能功率武器等脉冲功率负荷提供瞬时高能。脉冲负荷具有极高瞬时功率,它的使用必将对系统电能质量带来较大的影响。为此就脉冲负荷对舰船综合电力系统的冲击作用进行了研究,其脉冲功率系统为储能电容充电电路形式。充电电路有2种不同拓扑结构:基于可控整流器和基于不可控整流-直流变换器。结果表明:脉冲负荷采用不可控整流器-直流变换器拓扑形式比采用可控整流器拓扑形式对系统造成的冲击小得多,并且电力推进的协同使用可进一步降低冲击强度。     

Regenerative converter for PWM AC drives

Since the PWM induction motor drive has become the industrial drive of choice, applications involving four-quadrant operation for AC drives have become more common. To satisfy such applications, a regenerative AC/DC converter that is robust is needed to allow bidirectional power flow between the load and power distribution system. A robust technology that is well understood is the 6 SCR converter operating in the inverting mode. However, the typical 6 SCR converter will either limit the maximum DC bus voltage or require a step-up transformer. The proposed regenerative converter allows the SCR power structure to operate as a synchronous line commutator, while a two-transistor series/shunt chopper, with a power resistor, controls the regenerative power flow, and offers an emergency braking capability. In addition, SCR commutation is accomplished by the line voltage and diversion of bus current. Both simulation and experimental results are given     

Electronic Commutator Direct Current (ECDC) machine

Conventional DC motors are highly efficient and their characteristics make them suitable for use.However, their major drawback is that they need a commutator and brushes which are subject to wear and require maintenance. Today new technology is attempting to replace these components and reduce permanently these maintenance costs. When the task of commutator and brushes are replaced by solid-state switches, free maintenance motors are invented and the new motor called brushless DC motors emerged.This paper describes another motor which uses an electronic commutator substituting the mechanical commutator and brushes in the DC machine. This electronic commutator is formed with a series of static converters mounted along a bridge structure connected between the two rings and the windings of the machine. The polarities of the machine are obtained using two brushes in contact with the two rings. The control of the converter transistors is achieved by phototransistors controlled by two light sources replacing the brushes, so the sliding electrical contact between brushes and commutator was removed.     

A Multifunction DC-DC Converter as Versatile Power Conditioner

A multifunction dc-dc converter that can be used as a single power conditioner connecting the source, the storage, and the load in solar or wind energy systems is presented. Operation of the converter in four configurations is analyzed and simulated. Application of the converter is discussed, and experimental results obtained with a prototype circuit are given.     

Impact of Postfault Active Power Recovery of Photovoltaic Power Generation on Transient Stability

Currently, Japanese grid codes require photovoltaic (PV) power generation systems to continue supplying power to the grid as soon as possible even if the systems temporarily stop their operation. Although the fault ride‐through capability was originally proposed for preventing a cascading frequency drop in the power system, the capability has the impact on other instability phenomena such as transient stability. In this study, we focus on the postfault active power recovery of the PV systems. The impact of the recovery speed on the transient stability is investigated under different load conditions, in particular static/dynamic load condition. Numerical examples are carried out for the one‐machine one‐load infinite‐bus system, and the effects of the recovery speed are evaluated by equal area criterion and critical clearing time. As a result, we have found both desirable and undesirable effects on the transient stability depending on the load condition.     

A new parallel ZVS converter with less power switches and low current stress components

A new direct current (DC)/DC converter with parallel circuits is presented for medium voltage and power applications. There are five pulse‐width modulation circuits in the proposed converter to reduce current stress at low voltage side for high output current applications. These five circuits share the same power switches in order to reduce switch counts. To reduce the converter size, conduction loss, and voltage stress of power semiconductors, the series connections of power metal‐oxide‐semiconductor field‐effect transistor (MOSFET) with high switching frequency instead of insulated gate bipolar transistor (IGBT) with low switching frequency are adopted. Thus, the voltage stress of MOSFETs is clamped at half of input voltage. The switched capacitor circuit is adopted to balance input split capacitor voltages. Asymmetric pulse‐width modulation scheme is adopted to generate the necessary switching signals of MOSFETs and regulate output voltage. Based on the resonant behavior at the transition interval of power switches, all MOSFETs are turned on under zero voltage switching from 50% load to 100% load. The circuit configuration, operation principle, converter performance, and design example are discussed in detail. Finally, experimental verifications with a 1.92 kW prototype are provided to verify the performance of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.     

Power system applications for PASC converter systems

This paper shows, using EMTP computer simulations, some preliminary results of applying pulse amplitude synthesis and control (PASC) technology to single-source voltage converter systems. The method can be applied to any single terminal pair source with appropriate modifications in power extraction interface and computer control program to match source and load impedance characteristics. The PASC realization as discussed employs banks of transformers, one bank per phase, in which the primaries are connected in parallel through a switch matrix to the DC source. Two opposite polarity primaries per transformer are pulsed alternatively in time to produce an oscillatory sinusoidal output waveform. PASC conversion system capabilities to produce both leading and lagging power factor power output in single-phase and three-phase Δ or Y configurations are illustrated. EMTP simulations are used to demonstrate the converter capabilities. Also included are discussions regarding harmonics and potential control strategies to adapt the converter to an application or to minimize harmonics     

Residential solar-powered air conditioners

The power demand in Japan increases yearly especially in summer, and peaks in the daytime. The main cause is the drastically increased load of air conditioners used widely in general residences. The load pattern of air conditioners is very similar to the output pattern of a photovoltaic (PV) array. Therefore, Sanyo has been developing two types of residential solar-powered air conditioners. One is a unidirectional system by using a dc/dc converter which controls the voltage of a PV array at its optimal operation point and boosts the voltage up to the dc voltage of an inverter-type air conditioner. The other is a bi-directional system by using a bi-directional current-control converter, which regenerates surplus power into a commercial system from a PV array, and suppresses the input current distortion of an air conditioner. In this paper, the configurations and experimental results are described and discussed.     

Strategies for the Fault-Tolerant Current Control of a Five-Phase Permanent-Magnet Motor

This paper deals with the postfault current control strategies of a five-phase permanent-magnet (PM) motor. The analysis covers both the open circuit of one and two phases and the short circuit at the machine terminal of one phase. The proposed control guarantees safe drive operation after any fault occurrence. For the sake of generality, an analytical model has been used to investigate the properties of each postfault strategy. The results are general, and they apply to PM motor of any power rating. Simulations and experimental results validate the theoretical predictions.     

带恒功率负载的DC/DC变换器起动过程分析

以平均电流控制Buck变换器为研究对象,基于平均大信号模型,借助相平面法,对恒功率负载以及阻性负载的起动过程进行比较,分析了两种情形下的起动过程,揭示了变换器带恒功率负载起动过程存在两种类型:正常起动与限流工作状态,通过提高电流限流点可以确保系统集成后起动性能不受影响.仿真与实验结果验证了理论的正确性.     

变频器在起重机调速控制系统中的设计与应用

对于升降类的恒转矩负载,如起重机、电梯等,这类负载的特点是起动时冲击电流大;下降过程中会有能量回馈,需要一定的制动转矩,因此要求变频器留有一定的余量。通用变频器内部本身提供的制动转矩往往不能满足要求,需要外加制动单元。通过分析桥式起重机拖动负载的特性,选用具有四象限运行特点的矢量变频器进行设计。     

永磁直驱风电系统变流器拓扑分析

永磁直驱风电系统变流器为永磁同步发电机和电网的接口,对其常用的拓扑进行了详细的分析和说明,包括不控整流 逆变器、不控整流 DC/DC变换 逆变器、背靠背双PWM变换器等拓扑,对其工作原理、应用和优缺点进行了介绍和对比,并针对风电机组对大功率变流器的需求,对大功率拓扑结构的特性和应用进行了详细的介绍。不控整流 Boost变换 并网逆变器和背靠背双PWM变换器2种拓扑是目前的优选方案,多电平变换器因其优良的性能将具有良好的发展前景。     

Integration of a bi-directional DC-DC converter model into a real-time system simulation of a shipboard medium voltage DC system

A bi-directional dc/dc converter model is investigated for a notional Medium Voltage DC (MVDC) shipboard power system to improve energy flexibility and deal with peak energy demand in shipboard power system. Surplus energy in the MVDC system during light load condition can be captured by energy storages distributed in local load zones through the bi-directional dc/dc converters and then can be used during heavy load condition or black starting of the MVDC system. In this paper, the derivation process of the small-signal average models of the isolated-type bi-directional dc/dc converter is presented for controller design. This paper also presents the controller optimization process using intelligent optimal searching algorithm, Particle Swarm Optimization, for optimizing dynamic and steady-state control performance of a bi-directional dc/dc converter. The control performance of the proposed controller is evaluated using frequency-domain analysis and time-domain simulation of the large-scale notional MVDC shipboard power system using the Real-Time Digital Simulator.     

基于不对称运行下换相过程的改进换流器动态相量模型

为充分研究大规模交直流混联系统动态特性,建立准确而高效的换流器数学模型是当前的关键问题。文章分析了交流系统在不对称故障情况换流器的换相过程,综合考虑了换相电压的相位偏移引起的换相电压过零点偏移和导通角偏移,以及交流系统的谐波等对换相持续时间的影响,提出了改进的换相角动态相量计算方法,建立了适用于不对称运行条件下的改进换流器动态相量模型,并通过选取主要谐波简化了模型的计算过程。仿真验证了所提出的改进换流器动态相量模型的精度和准确性。     

The structure and operating algorithm of a commutator in the neural network of a self-routing analog-to-digital converter

This paper is dedicated to the structure of a neural network of a self-routing analog-to-digital converter, especially its first hidden level—commutators. The paper also presents two possible structures of a commutator from the point of view of collecting information on the state of a neural network, and their algorithms are described. The structures are compared, and a conclusion is drawn regarding the advantages and disadvantages of their operation.     

中点钳位式三电平STATCOM的动态相量建模与仿真

首先介绍了中点钳位式(NPC)三电平静止同步补偿器(STATCOM)的结构和原理．采用一种改进的空间矢量脉宽调制(SVPWM)控制方法，用以解决换流器直流侧两个电容的电压均衡问题：通过开关函数详细描述了换流桥的离散动态过程，使用动态相量法得到STATCOM的动态模型．并同时给出了电源、负荷和输电线路的动态相量模型：最后使用Simulink／Matlab平台分别实现了含NPC三电平STATCOM测试系统的电磁暂态模型和动态相量模型的建模．仿真结果验证了动态相量模型的精确性和有效性．     

输入串联输出并联变换器的控制器设计及稳定性分析方法

输入串联输出并联(ISOP)变换器具有低电压、电流应力、模块化等优点,在高压至低压的功率变换领域得到广泛的应用。以输入电压平衡作为基本控制思想,结合ISOP变换器的等效双闭环控制框图,提出了相应的控制器设计方法及稳定性分析方法,在简化了控制器设计流程的同时提高了稳定性分析的可靠性。为了验证该方法的有效性,选取了双向高效能软开关DC-DC变换器——全桥LLC谐振变换器作为研究对象,对其小信号控制模型进行了进一步的推导和完善,并结合实例,完成了控制器的设计和稳定性的分析。最后,搭建了基于全桥LLC谐振变换器的2单元ISOP变换器实验平台,从起机过程、负载切换过程和功率平衡效果3个方面对上述结论进行了实验验证。     

Stability Analysis of Cascaded DC–DC Power Electronic System

Stability analysis of the cascaded dc-dc power electronic system is analyzed in this paper. For demonstration boost converter supplying, the hybrid switched capacitor converter considered as an example. The boost converter is acting as the bus converter, 42 V bus, while the switched capacitor converter is serving as the point of load converter. The two converters are provided with voltage-mode and peak current-mode controllers, respectively. Converter state-space, two-port network models are developed and then stability of the cascaded system has been analyzed. Cascaded system interaction effects, (i) source converter power handling capability with switching load and (ii) load converter interfacing capability with bus converter, are analyzed. Simulation and experimental results are provided for verification purpose. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

基于两象限DC/DC变换器的光伏发电系统

传统MPPT电路串联在光伏组件和负载之间.光伏板产生的所有电能都要经过DC/DC变换器进行处理.因此.整个光伏发电系统的效率就要依赖于DC/DC变换器的效率.针对离网型光伏发电系统提出一种两象限DC/DC变换电路,并将最大功率跟踪电路与其并联,主要能完成蓄电池充放电,升降压电路的功能.由于与主电路并联,仅有少部分能量通...     

A learning aid for power electronics with knowledge basedcomponents

In this paper we have presented a self-study expert system based power electronics instruction aid for selection and analysis of suitable power electronic converter configurations. Converter input output specifications, analysis, and converter design methodologies are interactively pursued with extensive graphical aid to guide the user (student, engineers, etc.) in the study process. Furthermore, transient, steady-state, and harmonic analysis are possible with an integrated simulator within the instruction module. A fault diagnosis expert system based module for converter-fed motor-drives, which can be chained with the expert learning aid, has also been developed. This is in the process of development to diagnose faults on all converters available in the package