A new method of damping harmonic resonance at the DC link in a large‐capacity rectifier‐inverter system

This paper proposes a new method of damping harmonic resonance in the DC link of a large‐capacity rectifier‐inverter system, such as in rapid‐transit railways. A voltage‐source PWM converter is connected in series to the DC capacitor of the rectifier through a matching transformer, acting as a damping resistor to the DC capacitor current. No filters are needed to extract harmonic components from the DC capacitor current. This results in a quick response and highly stable damping. The relationship between the control gain of the PWM converter and the required rating is theoretically discussed. We show that the required rating is less than one‐thousandth of that previously proposed. In particular, regenerating the power consumed by the PWM converter is very important because of the large power in practical systems. Normally, an additional PWM inverter is connected to the DC bus of the PWM converter to regenerate the consumed power. The additional inverter regenerates the DC power to the AC source through a transformer. This method, however, makes the damping circuit complex, thus the proposed method for the DC‐link harmonic resonance is less practicable. In this paper, a simple and novel scheme that utilizes the DC‐link voltage of the rectifier as a DC source for the PWM converter is proposed. The excellent practicability of the proposed damping method with the novel regenerating scheme is confirmed using digital computer simulation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(2): 53–62, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10172     

Method for Diffusing Carrier Noise under Zero‐Speed Condition using a Zero‐Sequence Voltage

In this paper, a technique is proposed to reduce the carrier noise of pulse width modulation (PWM) inverters for a permanent magnet motor drive. The carrier noise is generated by the motor and the reactor driven by the inverter and affected by the switching frequency. When a motor rotates and drives a machine, the carrier noise is hidden by the machine noise. However, when the motor speed is approximately zero, the carrier noise becomes dominant and raucous. The typical method to reduce the noise employs a switching frequency higher than the audible frequency of human hearing. However, the increase in switching frequency results in the inverter suffering a higher switching loss and lower efficiency. In particular, when the permanent magnet motor operates at approximately zero‐speed and full‐load, for example, in the hill‐start conditions of electric vehicles and the start and stop conditions of elevators, the current flows in specific power devices and the switching loss further increases. The proposed technique uses a zero‐sequence voltage, which is generated randomly with the M‐sequence signal, and diffuses the frequency components of the ripple contained in the current. The technique is able to reduce the noise without increasing the switching frequency of the inverter when the motor speed is almost zero. Simulation and experimental results show that the proposed technique can diffuse the carrier noise and the cycle of the M‐sequence signal changes the diffusion effect of the carrier noise.     

A sensorless drive system for brushless DC motors using a digital phase‐locked loop

This paper proposes a sensorless drive system for Brushless DC (BLDC) motors using a Digital Phase‐Locked Loop (DPLL). The Back Electromotive Force (BEMF) voltage is measured from the motor winding to determine the permanent magnet rotor position using the DPLL, and Pulse Width Modulation (PWM) limits the motor current to control the speed of BLDC motors. The proposed method can drive BLDC motors using an open‐loop control without stepping out. Also, the proposed method is compared experimentally with a control method that uses Hall sensors. Experimental results for the BLDC motor show the effectiveness of the proposed method. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(1): 57–66, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10074     

A speed control method for a PM motor using a speed observer and a low‐resolution encoder

This paper proposes a new speed control method for a PM motor using a low‐resolution encoder and a speed observer. The servo system should be economical and simple. For this purpose, this paper realizes the high‐performance speed control system using a low‐resolution encoder, whose performance is nearly equal to the performance of speed servo system using a conventional optical encoder. The speed observer uses the information of motor current and motor voltage. The rotor position is calculated by the estimated value of speed observer. This observer has the influence of electrical parameter variation. This paper proposes the correction algorithm of both the voltage error of PWM inverter and the electrical parameter variation. The experimental results and numerical simulation results point out that the proposed speed control system has the desired speed response with respect to parameter variations and load torque perturbation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 66–75, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10121     

Novel current‐source multilevel inverter driven by single gate drive power supply

This paper proposes a novel current‐source multilevel inverter, which is based on a current‐source half‐bridge topology. Multilevel inverters are effective for reducing harmonic distortion in the output voltage and the output current. However, the multilevel inverters require many gate drive power supplies to drive switching devices. The gate drive circuits using a bootstrap circuit and a pulse transformer can reduce the number of the gate drive power supplies, but the pulse width of the output PWM waveform is limited. Furthermore, high‐speed power switching devices are indispensable to create a high‐frequency power converter, but various problems, such as high‐frequency noise, arise due to the high dv/dt rate, especially in high‐side switching devices. The proposed current‐source multilevel inverter is composed of a common emitter topology for all switching devices. Therefore, it is possible to operate it with a single power supply for the gate drive circuit, which allows stabilizing the potential level of all the drive circuits. In this paper, the effectiveness of the proposed circuit is verified through experimental results. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 88–95, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20475     

Characteristics of PM synchronous motor drives with a trapezoidal EMF

A permanent magnet synchronous motor (PMSM) with nonsinusoidal electromotive force (EMF) generates torque ripple even if the sinusoidal PWM inverter drives the PMSM. A new modified trapezoidal modulating signal for PWM inverter suitable for PMSM drive with nonsinusoidal EMF is proposed in this paper. A new modulating signal for the PMSM drive is determined by the condition of reducing torque ripple of the motor with various trapezoidal EMF. When the PWM inverter using modified trapezoidal modulating signal drives the PMSM having a nonsinusoidal EMF, the torque ripple of the motor can be reduced, the DC link voltage utilization is improved, and reduction of switching loss can be obtained. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(1): 62–71, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20441     

Carrier phase error detection method and synchronization control of parallel‐connected PWM inverters without signal line

In recent years, parallel operation of inverters is employed to increase reliability and capacity in an uninterruptible power supply (UPS) system. A phase error in PWM carrier‐signals of each inverter causes high‐frequency loop current between inverters. Therefore, the PWM carrier‐signal of each inverter should be adjusted in phase. This paper proposes a detection method of phase error in PWM carrier‐signal and its application to synchronization control for parallel‐connected inverters. A simple definite‐integral circuit achieves detection of the carrier phase error from high‐frequency loop current using no signal line between inverters. The detected carrier phase error is applied to synchronize the PWM carrier‐signal through a PI compensator, and then the high‐frequency loop current can be suppressed. Several experimental test results show the validity of the proposed detection method and synchronization control. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(1): 63– 71, 2006; Published online in Wiley InterScience ( http://www.interscience.wiley.com ). DOI 10.1002/eej.20143     

Experimental investigation of a speed‐sensor‐less IM drive system under Inverter fault‐tolerant control

This paper proposes an algorithm for fault tolerance of three‐phase, inverter‐fed, speed‐sensor‐less control of a three‐phase induction motor drive system. The fault tolerance of the inverter when one switch is open or one leg of six‐switch inverter is lost is considered. The control of the drive system is based on indirect rotor field‐oriented control theory. Also, the speed estimator is based on model reference adaptive system (using stator current and rotor flux as state variables for estimating the speed). The fault‐tolerant algorithm is able to adaptively change over from a six‐switch inverter to a four‐switch inverter topology when a fault occurs; also, it makes a smooth transition of the motor speed, torque, and current when changing over from a faulty condition to a new healthy status, which is four‐switch three‐phase inverter (FSTPI) topology; thus, the six‐switch three‐phase inverter (SSTPI) topology (pre‐fault status) is almost retained for the medium‐power range of induction motor applications. The proposed algorithm is simulated by using the MATLAB/SIMULINK package. Also, the proposed control system is tested experimentally using a digital signal processor (DSP1104). The obtained results from the simulation model and experimental system demonstrate the performance enhancement and good validity of the fault‐tolerance control for the speed‐sensor‐less induction motor drive system. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A new generalized high‐frequency voltage injection method and mirror‐phase estimation method for sensorless drive of salient‐pole PMSMSs

This paper proposes a new generalized high‐frequency voltage injection method for sensorless drive of salient‐pole permanent‐magnet synchronous motors. The injected high‐frequency voltage has a unique spatially‐rotating elliptical shape, with the amplitudes of both the major and minor axes varying with the motor speed, and can be designed by selecting a design parameter. The high‐frequency current caused by the injected voltage, which has information on the rotor phase to be estimated, is speed‐independent, that is, is not affected by the motor speed at all. Consequently, the rotor phase can be estimated in a wide speed range from zero to the rated speed. By selection of the design parameter, the properties of the high‐frequency current can be adjusted appropriately to the associated motor‐drive system consisting of a motor and an inverter. As a versatile phase estimation method for estimating rotor phase using the high‐frequency current, the “mirror‐phase estimation method” is reconstructed and reproposed. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 67–82, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20803     

Comparisons between a hybrid shunt active filter and a pure shunt active filter

This paper deals with the hybrid shunt active filter for harmonic compensation of a three‐phase diode rectifier in a 480‐V adjustable‐speed motor drive system. The hybrid filter is formed by a three‐phase LC filter tuned around the seventh harmonic frequency and a small‐rated three‐phase voltage‐source PWM inverter. The LC filter and PWM inverter are directly connected in series. As a result, the DC capacitor voltage of the PWM inverter in the hybrid filter is much lower than that of a conventional pure shunt active filter. This results in higher efficiency, less switching ripple, and less EMI emission. Computer simulation is carried out to compare the hybrid filter with the pure filter in terms of circuit configuration and filtering performance. Simulation results indicate that the hybrid filter is superior in effectiveness and viability to the pure filter. In addition, theoretical analysis based on vector loci confirms the validity of the simulation results. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(2): 61–70, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20145     

Harmonic analysis of the output voltage of a third‐harmonic‐injected inverter for LSM drives

The superconducting magnetic leviation railway system (MAGLEV) under development in Japan uses pulse‐width‐modulation (PWM) inverter for driving a linear synchronous motor (LSM). The inverter output voltage contains nonnegligible harmonics which cause harmonic resonances in the LSM system, and therefore harmonics of the output voltage have been analyzed in order to control such harmonic resonances. This paper applies a third‐harmonic injection method to the inverter for the purpose of enhancing the output voltage without changing the circuit configuration. It performs harmonic analysis of the output voltage of the inverter based on the third‐harmonic injection. Validity of the harmonic analysis is verified by computer simulation. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 71–78, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ).     

Effect of Carrier Frequency and Circuit Resistance on Iron Loss of Non‐Oriented Electrical Steel Sheet under Single‐Phase Full‐Bridge PWM Inverter Excitation

Because of the development of power electronics technology, pulse width modulation (PWM) inverters are now being used to drive motors in order to achieve precise and energy‐efficient control. Precise estimation of the increase in iron loss due to the high harmonic components of flux, including the carrier frequency, is important in the design of motors excited by a PWM inverter. We measured the iron losses of non‐oriented electrical steel sheets that were excited using a single‐phase full‐bridge PWM inverter, and examined the influence of the carrier frequency and circuit resistance on the iron loss. We showed that the iron loss increased because of the generation of minor loops when the circuit resistance was high. Therefore, the circuit resistance should be decreased in an actual motor system.     

一种抑制三相两电平逆变器电流纹波的变零矢量分配PWM方法

三相两电平逆变器广泛应用于交流电机驱动、电能变换等领域。由于逆变器的输出电流含有纹波成分,会给系统带来损耗增加、性能下降等问题。在脉冲位置居中对称的前提下推导了电流纹波模型,分析了脉冲宽度调制PWM(pulse width modulation)技术中开关周期、脉冲占空比和脉冲位置对电流纹波的影响,并提出了一种改变脉冲占空比抑制电流纹波的PWM方法,即变零矢量分配脉冲宽度调制VZDPWM(variable zero-vector distribution pulse width modulation)技术。最后,通过仿真和实验验证了VZDPWM抑制电流纹波的有效性。     

High‐efficiency and low‐acoustic‐noise drive system using an open‐winding AC motor and two space vector modulated inverters

The combining of the outputs of two inverters using interphase reactors is a widely used method for supplying large AC drives rated at more than several thousand kilowatts. Certain drawbacks are associated with this method, such as high acoustic noise and high losses due to the interphase reactors. To overcome this problem, in this paper a new low‐acoustic‐noise and high‐efficiency drive system using an open‐winding AC motor and two space vector modulated inverters is proposed. This configuration consists of a three‐level inverter with switching once per cycle and a two‐level inverter of about 1 kHz switching frequency, connected to the opposite terminals of the open‐winding motor. With the proposed configuration, good current waveforms and high efficiency can be obtained. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 144(3): 46–57, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10157     

High‐efficiency,low‐torque ripple control of a permanent magnet synchronous motor based on current tracking vector of electromotive force

Since ordinary magnetic field poles of a PM (permanent magnet) motor generate higher harmonic flux, sinusoidal current will cause torque ripple. This is usually removed by short pitch winding, skew slot method, and so on. These methods have a drawback in terms of lower efficiency. Recently, new current control methods have been proposed to realize zero‐torque ripple and high‐efficiency drive at the same time. However, because the optimized reference current waveform obtained by these methods includes zero phase component, normal three‐phase full bridge inverter and d–q coordinate control method cannot be used. This paper proposes a new current control method that can achieve zero‐torque ripple and maximum efficiency by using a normal three‐phase inverter. The three‐phase optimum current can be derived by satisfying the following conditions: (1) the direction of the current resultant vector always agrees with that of the electromotive force resultant vector, and (2) the scalar product of the two vectors is held constant. By means of modifying the coordinate transformation angle, this method can also make it possible to compensate torque pulsation error with maximum efficiency using general d–q coordinate control method. The proposed method has been verified by experiments. © 2001 Scripta Technica, Electr Eng Jpn, 136(1): 57–64, 2001     

基于Buck变换器的无刷直流电机转矩控制仿真

无刷直流电动机（BLDCM）存在转矩脉动的突出缺点，提出了一种基于直流环节电压控制和模糊PID控制器的新型混合控制策略，以抑制无刷直流电机的转矩脉。电路拓扑包含功率因数校正降压转换器和逆变器。降压转换器通过控制直流电路电压来降低换向转矩脉动，使用模糊PID控制器和脉冲宽度调制（PWM）技术的逆变器在导通区域提供适当的电流。 Buck变换器降低了通过控制直流环节电压换向转矩脉动，逆变器使用模糊PID和PWM技术提供导通区域的电流。该方法能够消除传导区转矩脉动,削弱换相区转矩脉动，仿真结果表明，该策略具有功率因数校正功能，可有效抑制转矩脉动，提升电机运行的鲁棒性。     

基于MRAS和SVPWM永磁同步电动机无位置传感器控制

依据永磁同步电动机的动态耦合关系,提出一种模型参考自适应辨识算法来估算转子的位置。永磁同步电动机无位置传感器的调速系统采用空间矢量脉宽调制策略以减小逆变器输出电压的谐波成分,降低转矩脉动。仿真结果证实了模型参考自适应辨识算法对转子位置跟踪准确,系统具有很强的鲁棒性,是实现永磁同步电动机无位置传感器控制的一种实用方法。     

Improved current source GTO inverter-fed induction motor driveswith PWM-controlled thyristor converter

An improved current-source GTO (gate turn-off) inverter system for driving an induction motor at high frequency was developed. This system is composed of an inverter using GTOs and a PWM (pulsewidth-modulated)-controlled thyristor rectifier. The energy rebound circuit in the inverter is used to turn off the thyristors in the rectifier and to apply PWM control techniques. This circuit plays an important role in the treatment of reactive power in a load. The capacitors connected to the AC input terminal to improve PWM control also function as a filter. Thus, the waveforms of the input voltage and current become almost sinusoidal. Principles and circuit operations of the rectifier section are described in detail. The current-source GTO inverter is used to drive a 5.5 kW induction motor. The experimental waveform and characteristics for the tested motor drives are given. It is shown that the harmonic components of the input voltage and current are eliminated or reduced by using the PWM control technique without spoiling the inherent characteristics of the current-source GTO inverter     

Identification of the parameters of the high‐frequency equivalent circuit of PM synchronous motor based on genetic algorithm

This paper presents an identification technique of parameters of a high‐frequency equivalent circuit of permanent magnet synchronous motors (PMSM) driven by a PWM inverter. The high‐frequency oscillatory currents such as leakage current to the motor frame (common‐mode current) and high‐frequency oscillatory line current (normal‐mode current) are generated by switching instants of inverter transistors. The parameters of the high‐frequency equivalent circuit of PMSM which can simulate the oscillating current are identified by means of genetic algorithm. It is shown that the high‐frequency equivalent circuit with identified parameters can generate the oscillating current by some simulation results. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(4): 57–66, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20717     

Power factor improvement of single‐phase diode rectifier circuit by field‐weakening of inverter‐driven IPM motor

This paper proposes a novel inverter drive system to improve the input power factor of single‐phase diode rectifier. Conventional rectifiers need a high‐frequency switching device and a reactor to improve the input power factor. However, the proposed power converter does not need the switching device, electrolytic capacitor, or reactor. By making many ripples across the DC‐bus voltage, the input power factor can be improved. The proposed system consists of only a single‐phase diode rectifier, small film capacitor, three‐phase inverter, and motor. The proposed system adopts an interior permanent magnet (IPM) synchronous motor. The IPM motor is well known as a high‐efficiency motor and can realize field weakening. The basic ideas of the inverter control method are based on the following operations: the inverter's controlled synchronous with the DC‐bus ripple voltage by field‐weakening method, and direct active power feeding from the source side to the motor without smoothing the DC‐bus voltage. This paper describes that the proposed method can obtain an input power factor of 97.3% by experimental tests, and realizes the goals of small size and long life of the system. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(2): 66–73, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20047