A new variable‐speed,constant‐frequency,stand‐alone power generating system

Variable‐speed and constant‐frequency power generating systems using rotor excitation of the wound‐rotor induction machines have been used for such applications as variable‐speed pump generators and flywheel energy storage systems. However, the stand‐alone generating system of this type has only been reported and has not yet been practically used. On the other hand, the stand‐alone generating systems using diesel engines have been widely used for emergency supplies of plants or isolated islands and so on. However, in these cases, synchronous generators are usually used. If the output frequency is to be kept constant, there is the need to control the speed of the engine using a high‐performance governor. Even then, the output frequency changes in the case of a sudden load change. This paper proposes a new stand‐alone power generating system. In this system, the constant‐frequency output voltage can be obtained even though rotor speed changes by several percent. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(2): 75–85, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10191     

A novel slip‐power recovery system using a PWM boost rectifier

A novel compact slip‐power recovery system having sinusoidal rotor currents is proposed. In this system, a PWM boost rectifier is used as a substitute for a diode rectifier and a boost chopper in a conventional compact slip‐power recovery system. The conventional compact system has the disadvantage that it has a rectangular rotor current, and a motor torque with large ripple, because a diode rectifier remains in the system. Also, the rotor current cannot reach the current reference value near the synchronous speed, because the voltage drop caused by the resistance of the semiconductor devices and so on cannot be neglected when the rotor voltage becomes smaller near the synchronous speed. The use of the system proposed in this paper has solved these problems. The effectiveness of the proposed system was verified through computer simulations and experiments. As a result, the proposed system brings the sinusoidal rotor current, the small torque ripple, and wide controllable range near the synchronous speed. © 2002 Scripta Technica, Electr Eng Jpn, 139(2): 52–60, 2002; DOI 10.1002/eej.10012     

不平衡电压下双馈感应发电机转子侧变流器的灵活功率控制

针对不平衡电压下双馈感应发电机(DFIG)转子侧变流器的控制,分析定子瞬时有功和无功功率与三相定子电压、转子电流的关系,通过引入连续调节系数得到转子三相电流指令值的通用计算式。进一步地,求得指令电流调节系数、转子电流峰值及DFIG定子有功和无功波动的表达式,分析DFIG控制特性随调节系数、电压不平衡度的变化规律;分析不平衡电压跌落下DFIG的可控性,给出电压跌落后定子电压的临界值和转子侧变流器可控的判断条件;以功率波动设定值为目标,计及转子电流峰值限制,建立DFIG单位功率因数和无功功率支持2种模式下的灵活功率控制策略,通过仿真验证所提方法的可行性。     

Sensorless vector controlled converter for variable speed wind generation system using an induction generator

This paper proposed two types of speed sensorless converters that can control rotational speed and electric power. One is based on a slip frequency control system. The other is based on a vector control system. The rotational speed of the wind turbine is estimated with the phase voltage and phase current of the induction generator by the adaptive rotor flux observer. The estimated wind turbine rotational speed ω_r^est is used as the feedback of the speed control loop in the converter control system. Also, the estimated rotor flux ?_2d^est is used for the vector control. The simulation results confirm that both of them perform satisfactorily under the speed sensorless operation. The method based on the vector control system generates more electrical energy than does the method based on the slip frequency control system. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 62–75, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20323     

双馈型风电机组网侧换流器无功功率调节控制策略

全面分析了双馈型风电机组网侧换流器在正常工作和故障情况下的无功调节能力,提出了相应的网侧换流器无功控制策略来充分利用其无功调节能力以改善风电场的并网能力.采用DigSILENT/PowerFactory 14.0,搭建详细的双馈型风电机组模型,并接入等效弱电网.仿真结果验证了提出控制策略的有效性:正常工作情况下,网侧换...     

A current‐mode 1kHz/10kHz low‐voltage integrated analogue PLL for lock‐in portable applications

We present a low‐supply voltage (2V) low‐power consumption (500W) analogue phase‐locked loop (PLL), working at two low frequencies (1 and 10kHz), to be used in an integrated lock‐in amplifier. An externally settable control bit allows the switching operation between the two different frequencies. The circuit has been designed in a standard 0.6–m CMOS technology and differs from the standard analogue PLL architectures for the current mode implementation of both the loop filter and of the oscillator. Three different locked waveforms (sinusoidal, triangular, squared) can be obtained at the PLL output. Simulation results, obtained through the use of PSPICE and using accurate transistor models, will be proposed. The pull‐in ranges are about ±250Hz around 1 and ±1.3kHz around 10kHz, with pull‐in times of about 10 and 4ms, respectively. Copyright © 2003 John Wiley & Sons, Ltd.     

A matching transformer‐less inrush current suppressor for transformers using a series‐connected small‐rated voltage‐source PWM converter—consideration of the control gains and required ratings of the PWM converter

This paper proposes a new inrush current suppressor using a series‐connected small‐rated PWM converter for a transformer. The PWM converter is directly connected in series between the source and transformer without a matching transformer. The inrush phenomena of the matching transformer, thus, can be avoided. The control gain and required ratings of the series‐connected small‐rated PWM converter are discussed in detail. The capacity of the DC capacitor of the PWM converter is also discussed considering the active power flows into the PWM converter. The PSCAD/EMTDC is used to verify the validity of the proposed inrush current suppressor. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed suppressor can perfectly overcome the inrush phenomena of transformers. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(3): 45–55, 2007; Published online in Wiley InterScience ( www. interscience.wiley.com ). DOI 10.1002/eej.20374     

Flywheel‐based AC cache power for stand‐alone power systems

Stand‐alone power systems (SPS) are attracting more and more interest with the global move toward distributed generation (DG). Without strong support from the power grid, they suffer from poor load‐following capability at varying loads. A cache power that has fast response and high energy efficiency is demanded. As a solution, this paper provides an AC power technology based on flywheel energy storage. Different from the other DC generation technologies such as electric double layer capacitor (EDLC) or superconducting magnetic energy storage (SMES), the proposed flywheel system generates AC power and therefore can be directly connected to the power line without any power semiconductors. Furthermore, the proposed technology realizes power in/out automatically in response to the frequency/voltage variation of the power line. Therefore, this system has the advantages of robustness, simplicity, and fast response. Besides, by getting rid of power semiconductors, the proposed flywheel system has a good overload capability as high as two to three times. We prove by simulation and experimentation the validity and effectiveness of the proposed technology to provide cache power for stand‐alone power systems. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

一种新颖的用于六相感应电机调速系统的空间矢量PWM方法

基于三相调速系统中传统的空间矢量理论和统一电压调制技术,本文提出了一种新颖的用于六相感应电机调速系统的空间矢量SVPWM方法.该方法有效地抑制了电压源逆变器供电的六相感应电机中定子谐波电流,提高了直流母线电压利用率,且易于实现,执行速度快,极易推广到以三相组为子集的多相感应电机调速系统PWM控制中.本文给出了这种SVPWM方法具体的实现思路,通过数字仿真和实验结果将它与传统的SPWM和SVPWM方法做了深入的分析和比较研究,研究结果验证了该算法的有效性,它具有谐波电流最小和实现简单的突出优点,在多相PWM逆变器控制中有广阔的应用前景.     

基于双馈风电机组的分布式动态无功支撑系统

充分挖掘风电机组的无功电压调节能力对改善电力系统的电压稳定性有重要意义。首先定量分析了实际商用双馈风电机组的无功调节能力及限制因素,指出双馈风电机组具备较强的无功功率输出和吸收能力。继而提出了一种利用双馈风电机组的电力系统分布式动态无功支撑系统的构想及其实现方案。该系统可充分发挥双馈风电机组的动态无功调节能力,有效提高电力系统的动态无功储备,并显著改善双馈风电机组接入电网的电压稳定性。实际浙江电网的仿真结果验证了该技术的可行性和有效性。     

Unbalanced power flow calculation of a power system containing a variable‐speed generator

There are some factors that render a power system network unbalanced: UHV transmission lines in which three‐phase transmission lines are not transposed, an unbalanced transformer, unbalanced load as well as sustained unbalanced faults. On the other hand, the number of variable‐speed generators used in pumping‐up power stations has recently been increasing in Japan. This paper presents a new means of calculating unbalanced power flow of a power system which contains variable‐speed pumping‐up generators. This new technique is based on the phase coordinate method, because a power system which has elements of unsymmetrical impedance can easily be analyzed by using it. In this paper, phase coordinate models of the variable‐speed generator and its secondary exciting circuit, composed of a GTO converter/inverter, are analyzed first. Procedures of power flow calculation of unbalanced power systems follow. © 2000 Scripta Technica, Electr Eng Jpn, 134(3): 34–43, 2001     

DBD型臭氧发生器电源的频率跟踪移相PWM控制技术及其实现

提出一种DBD型臭氧发生器电源频率跟踪移相PWM控制技术的实现方案.利用集成锁相环CD4046在锁定状态时第6,7脚输出的锯齿波与输入方波信号的稳定相位关系,用一给定直流电平与锯齿波作比较产生移相信号,达到频率跟踪移相PWM控制的目的.与其它的频率跟踪移相PWM控制技术实现方案相比较,该方案具有电路简单、实现容易等特点,实验结果证明了该方案的可行性和正确性.     

A waveform generator circuit for extra low‐frequency CMOS micro‐power applications

This paper presents a novel low‐power CMOS extra low‐frequency (ELF) waveform generator based on an operational trans‐conductance amplifier (OTA). The generator has been designed and fabricated using 2.5‐V devices available in 130‐nm IBM CMOS technology with a ±1.2‐V voltage supply. Using the same topology, two sets of device dimensions and circuit components are designed and fabricated for comparing relative performance, silicon area and power dissipation. The first design consumes 691 μW, while the second design consumes 943 μW using the same voltage supply. This low‐power performance enables the circuit to be used in many micro‐power applications. ELF oscillation is achieved for the two designs being around 3.95 Hz and 3.90 Hz, respectively, with negligible waveform distortion. The measured frequencies agree well with the simulation results. The first design is found to provide overall optimal performance compared to the second design at the expense of higher silicon area. Copyright © 2015 John Wiley & Sons, Ltd.     

A novel three‐phase converter using a three‐phase series chopper

This paper proposes a novel three‐phase converter using a three‐phase series chopper. The proposed circuit is composed of three switching devices, three‐phase diode bridge, input reactors, and LC low‐pass filter. In the conventional circuit, which combines three‐phase diode bridge and boost voltage chopper, to obtain sinusoidal input current the output voltage must be two or three times larger than the maximum input line voltage. However, in the proposed circuit, the input current can be controlled to be sinusoidal also when the output voltage is the same as the maximum input line voltage. This can be achieved because in the proposed circuit the discharging current of the reactors does not flow through the voltage source. The control method of the proposed circuit is as simple as that of the conventional circuit since all three switching devices are simultaneously turned on and off. This paper discusses the theoretical analysis and the design of the proposed circuit. In addition, simulation and experimental results are reported. The proposed circuit has obtained a 93% efficiency, and 99.7% at 1.3kW load as the input power factor. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 79–88, 2000     

定子双绕组感应发电系统的滞环电流控制方法

提出了一种基于空间电压矢量的适用于定子双绕组感应发电系统的滞环电流控制新方法.该方法将滞环控制与空间电压矢量PWM控制相结合,根据控制绕组的电流误差矢量与参考空间电压矢量的区域分布,选择最佳的电压矢量运行,使各相电流误差被限定在给定滞环内,准确跟踪各相给定电流,实现静止励磁控制器三相桥臂间的关联控制,消除相间影响.该方法实现简单,即能限制开关频率,又能有效减小电流误差,改善电流跟踪性能.实验结果证明了该方法的正确性和有效性.     

Transient current analysis of induction generators for wind power generating system

In this paper we present a transient current analysis of induction generators used in a wind power system before and after three‐phase fault conditions. First, the basic equations of an induction generator connected to an infinite bus are developed and then transient current analysis formulas are derived for a three‐phase fault before and after fault clearance. We also determine the initial phase angle for the three‐phase fault or the restoration phase angle of the power supply voltages and the time at which the maximum or minimum transient currents flow in the system. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(1): 38–45, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10319     

A novel method of suppressing the inrush current of transformers by using a series‐connected voltage‐source PWM converter

This paper proposes a novel method of suppressing the inrush current of transformers. A small‐rated voltage‐source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter serves as a resistor for the source current, no inrush phenomena occurs. The required rating of the PWM converter, which serves as the damping resistor for the inrush phenomena, is 1/400 that of the main transformers in single‐phase circuits. In three‐phase circuits, it is 1/900. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 56–65, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20174     

A low‐power small‐area 10‐bit analog‐to‐digital converter for neural recording applications

In vivo neural recording systems require low power and small area, which are the most important parameters in such systems. This paper reports a new architecture for reducing the power dissipation and area, in analog‐to‐digital converters (ADCs). A time‐based approach is used for the subtraction and amplification in conjunction with a current‐mode algorithm and cyclical stage, which the conversion reuses a single stage for three times, to perform analog‐to‐digital conversion. Based on introduced structure, a 10‐bit 100‐kSample/s time‐based cyclical ADC has been designed and simulated in a standard 90‐nm Complementary Metal Oxide Semiconductor (CMOS) process. Design of the system‐level architecture and the circuits was driven by stringent power constraints for small implantable devices. Simulation results show that the ADC achieves a peak signal‐to‐noise and distortion ratio (SNDR) of 59.6 dB, an effective number of bits (ENOB) of 9.6, a total harmonic distortion (THD) of ?64dB, and a peak integral nonlinearity (INL) of 0.55, related to the least significant bit (LSB). The ADC active area occupies 280µm × 250µm. The total power dissipation is 5µW per conversion stage and 20µW from an 1.2‐V supply for full‐scale conversion. Copyright © 2010 John Wiley & Sons, Ltd.     

基于矩阵变换器双馈风力发电系统矢量解耦控制

本文结合矩阵变换器、双馈感应电机(DFIG)风力发电系统的优点,导出了双馈电机风力发电系统在同步旋转dq坐标轴下的矢量控制数学模型;针对常规矢量控制中存在电流耦合情况,设计一种新型、简易的电流前馈解耦控制方案.在此基础上,建立基于矩阵变换器交流励磁磁场定向电流解耦矢量控制策略.MATLAB仿真结果表明,当有功、无功功率变化时,电流解耦控制具有良好动态性能.本文设计了11kW风力发电试验装置并进行离、并网实验,当双馈电机处于亚同步、超同步状态时,双馈电机定子电压和频率均能保持稳定,实现变速恒频运行.实验结果表明,基于矩阵变换器交流励磁双馈风力发电系统是可行的,并具有一定的实用价值.