An advanced permanent magnet motor drive system for battery-poweredelectric vehicles

Availability of high-energy neodymium-iron-boron (Nd-Fe-B) permanent magnet (PM) material has focused attention on the use of the PM synchronous motor (PMSM) drive for electric vehicles (EVs). A new Nd-Fe-B PMSM is proposed for the drive system, which possesses high power density and high efficiency, resulting in greater energy and space savings. The design and optimization of the motor employs finite element analysis and computer graphics. Increasingly, a new PWM inverter algorithm is developed for the drive system, which can handle the nonconstant battery voltage source. An efficiency optimizing control is adopted to further improve the energy utilization of the drive system. Both the control strategy and the PWM generation are implemented in a single-chip microcontroller. As a result, the motor drive achieves high power density, high efficiency, and compactness. A prototype of the 3.2 kW battery-powered drive system has been designed and built for an experimental mini-EV     

A space vector modulated CSI-based AC drive for multimotorapplications

A space vector controlled channel state information (CSI) drive for multimotor applications is investigated. The multimotor operation of the drive is achieved by integrating the proposed active damping control, inverter-side DC link voltage feedforward control and pulse width modulation (PWM) index control into the conventional V/f control. The main function of the active damping control is to suppress possible LC resonances caused by the inverter filter capacitor and motor inductances. This function is essential in achieving stable operation of the drive, especially in the multimotor drive where multiple LC resonant modes exist. An additional advantage provided by the active damping control is that it makes the control system less sensitive to motor parameters. The inverter-side DC link voltage feedforward control and the adjustable PWM modulation index control are developed to improve the dynamic performance of the drive system. In addition, the proposed space vector PWM pattern features a low switching frequency (500 Hz), which makes the proposed drive system suitable for high power applications. The system stability is investigated by means of eigenvalue analysis. The theoretic analysis is verified by experiments on a digital signal processing (DSP) controlled CSI multimotor drive     

A multilevel inverter system for an induction motor with open-end windings

In this paper, a multilevel inverter system for an open-end winding induction motor drive is described. Multilevel inversion is achieved by feeding an open-end winding induction motor with two two-level inverters in cascade (equivalent to a three-level inverter) from one end and a single two-level inverter from the other end of the motor. The combined inverter system with open-end winding induction motor produces voltage space-vector locations identical to a six-level inverter. A total of 512 space-vector combinations are available in the proposed scheme, distributed over 91 space-vector locations. The proposed inverter drive scheme is capable of producing a multilevel pulsewidth-modulation (PWM) waveform for the phase voltage ranging from a two-level waveform to a six-level waveform depending on the modulation range. A space-vector PWM scheme for the proposed drive is implemented using a 1.5-kW induction motor with open-end winding structure.     

An improved inverter output filter configuration reduces common anddifferential modes dv/dt at the motor terminals in PWM drivesystems

In this paper, an improved inverter output filter is proposed for pulsewidth-modulated (PWM) drive systems. The proposed filter is shown to effectively reduce both the differential and common modes dv/dt at the motor terminals, even in the presence of long motor leads. Reducing differential mode dv/dt reduces overvoltages at the motor terminals and lowers the stress on the motor insulation. Lowering common mode dv/dt is shown to significantly reduce high-frequency leakage currents to ground and induced shaft voltage in the motor. An important advantage of the approach is that the filter can be installed within the inverter enclosure to achieve both the differential and common modes dv/dt reductions at the motor terminals. Thus, the use of the filter can contribute to enhanced bearing life and improve reliability of PWM drive systems. Analysis, design equations, and experimental results on a 480-V 20-hp PWM drive system are presented. The filter configuration is an excellent candidate for many new and retrofit PWM 480-V/575-V drive systems     

Comparison of two techniques for closed-loop drive of VR stepmotors without direct rotor position sensing

Closed-loop control of variable-reluctance (VR) step motors without using direct rotor-position sensing is investigated. Two nondirect rotor-position sensing techniques, namely the waveform detection (WD) and the pulse-width-modulation (PWM) techniques, were implemented and applied to a four-phase (15° step-angle) VR step motor. Test results show that a DC shunt motor and a DC series motor type of performance can be achieved from the step motor with PWM drive and WD drive, respectively. The stability problem encountered with the existing PWM controller due to motional EMF effects at higher operating speeds is investigated, and modifications are suggested to include speed as an additional control signal to make the system more stable. With the inclusion of the speed signal, the operating speed of the test motor is from 1000 to 1750 r/min. The performances for the two techniques are compared, and experimental results are presented     

Measurement of conducted electromagnetic emissions in PWM motordrive systems without the need for an LISN

This paper presents a technique for measuring the conducted electromagnetic emissions produced by pulse-width modulated (PWM) inverter induction motor drive systems. The method does not require an artificial line-impedance stabilizing network (LISN) but does, however, allow the emission levels to be calculated as if an LISN were present. Testing can be performed when an LISN is either unavailable, prohibitively expensive, or impractical to include in the supply. This is often the case for large drive systems or for systems already installed in the field. A normal RF voltage probe and a spectrum analyzer are used to measure the spectra of the common-mode and differential-mode excitation sources due to the inverter switching. Line inductors for high-frequency (HF) isolation are required for some of the tests, but the cost and complexity of these compared to an LISN is low. Common-mode and differential-mode Thevenin equivalent circuits are then derived from measured impedances. The emissions for any defined supply impedance (including an LISN) can then be determined. A laboratory test on a 15 kW PWM drive system is carried out to verify the accuracy and effectiveness of the proposed method     

High efficiency, unity power factor VVVF drive system of aninduction motor

A high-efficiency, unity-power-factor VVVF (variable voltage, variable frequency) drive scheme for an induction motor is presented. A unity-power-factor PWM (pulsewidth modulated) converter regulates DC voltage. An inverter circuit with the magnetic flux control PWM method generates VVVF PWM waveforms. The modulation factor of the inverter PWM control with controllable DC link DC voltage is studied. As a result, the distortion factor and the switching frequency are reduced by over-modulation with low DC link voltage. A high-efficiency and unity-power-factor VVVF induction motor drive has been achieved using the control strategy     

Single-chip microcomputer control of the inverter by the magneticflux control PWM method [machine control]

Single-chip microcomputer control of a pulsewidth-modulated (PWM) inverter for motor drive applications is presented. The PWM pattern generation and the system control of the inverter are achieved by software of the 8-bit single-chip microcomputer. The single-chip microcomputer has a low processing speed and small memory capacity, disadvantages that can be overcome by the magnetic flux control PWM method. The PWM pattern is generated every 90 μs. The memory capacity of the PWM look-up table is less than 2 kbytes. Experimental results show that the motor performances are the same as that of the multichip triangular-sinewave PWM inverter     

Studies on the effect of filtering, digitization, and computationalgorithm on the ABC-DQ current transformation in PWM inverter drivesystem

In the automotive industry, PWM inverter controlled drive systems find extensive applications in electric vehicles and other motion control systems. A PWM inverter controlled three-phase brushless synchronous motor drive requires a microprocessor based controller to implement the control algorithms. The practical implementation of the control algorithms sometimes calls for the use of lookup tables involving discretized quantities. All these processes and the devices introduce nonidealities and errors in the drive system. Of particular importance in such a system is the ABC-DQ current transformations when vector control is implemented. In automotive applications, the emphasis is to design and realize accurate motion control systems in the most economic manner possible. Hence the effects of filtering, digitization, quantization, and digital computation algorithms and the accompanying inaccuracies introduced by them during the ABC-DQ current transformation in PWM drive system have to be dealt with in a careful manner for an optimum and economic choice of system design to be possible. Some of these aspects are discussed in this paper. The studies lead to a better understanding of the importance of various parameters of power electronics systems and in turn contribute towards the proper selection of parameters and therefore help the design process     

Control Strategy of PWM Inverter Drive System for Electric Vehicles

This paper presents an advanced ac drive system used in electric vehicles (EV's). The system consists of an induction motor, a PWM transistorized inverter, a variable ratio gear box and a controller. The special features of the drive system are discussed, with emphasis on the control strategy which can optimize the performance of the EV.     

A novel Fourier series time function for modeling and simulation of PWM

In this paper, a novel time function, called a modulated Fourier series (MFS), is presented for accurate modeling and rapid simulation of natural sampled pulsewidth modulated (PWM) systems in power electronic applications. This analytical technique eliminates the necessity for an iterative search, employed in currently available simulation packages, of modulated pulse edge transitions during accurate PWM waveform simulation. PWM simulation results are presented for MFS model validation, which are indistinguishable from those for an analog comparator modulator employing arbitrary nonperiodic signals. Additional simulation traces are presented of the fidelity with which the MFS accurately replicates, with only two carrier harmonics, the effects of PWM inverter switching on motor drive current as high-frequency harmonic ripple when compared with experimental test data. Substantial savings of up to fiftyfold in motor drive simulation time are presented without loss of simulation accuracy.     

Comparative evaluation of three-phase high-power-factor AC-DC converter concepts for application in future More Electric Aircraft

A passive 12-pulse rectifier system, a two-level, and a three-level active three-phase pulsewidth-modulation (PWM) rectifier system are analyzed for supplying the dc-voltage link of a 5-kW variable-speed hydraulic pump drive of an electro-hydrostatic actuator to be employed in future More Electric Aircraft. Weight, volume, and efficiency of the concepts are compared for an input phase voltage range of 98-132 V and an input frequency range of 400-800 Hz. The 12-pulse system shows advantages concerning volume, efficiency, and complexity but is characterized by a high system weight. Accordingly, the three-level PWM rectifier is identified as the most advantageous solution. Finally, a novel extension of the 12-pulse rectifier system by turn-off power semiconductors is proposed which allows a control of the output voltage and, therefore, eliminates the dependency on the mains and load condition which constitutes a main drawback of the passive concept.     

An integrated AC drive system using a controlled-current PWMrectifier/inverter link

Two identical three-phase, bipolar transistor, controlled-current, pulsewidth modulation (PWM) power modulators are integrated so that one functions as a rectifier and the other as an inverter in an AC drive system. The rectifier input currents maintain near-60-Hz sinusoidal waveforms with unity power factor. A leading power factor is also possible. The modulators do not depend on the availability of bidirectional switch elements. Performance as a polyphase induction motor drive under motoring and regenerative braking is reported. The study includes digital simulation of operation as a synchronous motor drive     

High-power CSI-fed induction motor drive with optimal power distribution based control

In this article, a current source inverter (CSI) fed induction motor drive with an optimal power distribution control is proposed for high-power applications. The CSI-fed drive is configured with a six-step CSI along with a pulsewidth modulated voltage source inverter (PWM–VSI) and capacitors. Due to the PWM–VSI and the capacitor, sinusoidal motor currents and voltages with high quality as well as natural commutation of the six-step CSI can be obtained. Since this CSI-fed drive can deliver required output power through both the six-step CSI and PWM–VSI, this article shows that the kVA ratings of both the inverters can be reduced by proper real power distribution. The optimal power distribution under load requirements, based on power flow modelling of the CSI-fed drive, is proposed to not only minimise the PWM–VSI rating but also reduce the six-step CSI rating. The dc-link current control of the six-step CSI is developed to realise the optimal power distribution. Furthermore, a vector controlled drive for high-power induction motors is proposed based on the optimal power distribution. Experimental results verify the high-power CSI-fed drive with the optimal power distribution control.     

Space vector pulse width modulation of three-level inverter extending operation into overmodulation region

Multilevel voltage-fed inverters with space vector pulse width modulation have established their importance in high power high performance industrial drive applications. The paper proposes an overmodulation strategy of space vector PWM of a three-level inverter with linear transfer characteristic that easily extends from the undermodulation strategy previously developed by the authors for neural network implementation. The overmodulation strategy is very complex because of large number of inverter switching states, and hybrid in nature, that incorporates both undermodulation and overmodulation algorithms. The paper describes systematically the algorithm development, system analysis, DSP based implementation, and extensive evaluation study to validate the modulator performance. The modulator takes the command voltage and angle information at the input and generates symmetrical PWM waves for the three phases of an IGBT inverter that operates at 1.0 kHz switching frequency. The switching states are distributed such that the neutral point voltage always remains balanced. An open loop volts/Hz controlled induction motor drive has been evaluated extensively by smoothly varying the voltage and frequency in the whole speed range that covers both undermodulation and overmodulation (nearest to square-wave) regions, and performance was found to be excellent. The PWM algorithm can be easily extended to vector-controlled drive. The algorithm development is again fully compatible for implementation by a neural network.     

Conducted electromagnetic emissions in induction motor drivesystems. I. Time domain analysis and identification of dominant modes

Stray components distributed in a pulsewidth modulation (PWM) drive system form parts of resonant circuits which can be excited to produce radio frequency (RF) noise driven by the pulsed switching action of the power devices. The dynamic response of such circuits is complex. It is essential to identify the dominant oscillation modes in the system so that electromagnetic interference (EMI) reduction techniques can be effectively implemented. This paper (Part I) investigates the mechanisms of conducted EMI emissions associated with a typical PWM inverter induction motor drive system. A numerical model, which includes the high-frequency effects within the machine, is established to evaluate the emissions in the time domain. The dominant high-frequency current paths are identified, and this allows the oscillation frequencies to be predicted from knowledge of the component values. The analysis is confirmed using laboratory measurements. Simplified frequency domain methods for direct calculation of the emission spectra based on the dominant high-frequency current paths are discussed in Part II     

轮式机器人控制系统设计

设计了一套基于直流电机的轮式机器人大功率驱动控制系统。本系统采用双H桥结构驱动两个电机,并以AVR单片机Atmega168为处理器实现电机控制。通过单片机定时器的快速PWM(脉宽调制)模式输出不同占空比的PWM信号,送给H桥,从而控制电机的转速。本系统以DXP2004为平台设计了电路原理图和大功率PCB(印刷电路板),并使用AVR Studio和WinAVR工具配合开发单片机程序,电路实测达到10 A以上驱动电流。     

Software waiting loop length control: Technique for reduction ofradiated EMI from microprocessor-based PWM drive system

A novel technique, referred to as software waiting loop length control (SWLLC), for reducing the radiated EMI from microprocessor-based PWM drive systems is presented. By randomly changing the length of the software waiting loops, the energy concentrated into discrete bands by the action of periodic signals on the external and internal buses of the microprocessor system can be spread across a larger frequency range. Using this technique, significant reduction of radiated interference levels has been observed in a typical PWM drive system     

基于myDAQ的直流电机PWM远程控制系统设计

提出了一种基于myDAQ的PWM远程控制直流电机调速与测量系统。采用LabVIEW开发平台,在上位机用图形化编程语言编制PWM控制信号,并通过myDAQ的模拟输出口将PWM信号送给直流电机驱动控制电路实现电机的调速,同时上位机启动、停止、转向等控制信号也通过myDAQ数字输出口送给驱动电路进而实现电机的起、停、转向控制。电机转速通过编码器测量并送至上位机,在上位机将会实时跟踪与显示电机运行状态以及PWM控制信号波形,利用LabVIEW的WEB发布技术将前面板发布至网络上进而实现运程控制。通过测试及分析,结果显示整个系统运行良好、稳定、实时性强。     

Comparison of voltage and current spectra using optimized forms ofinverter pulsewidth modulation

Modern electrical drive technology tends toward application of alternating current machines (especially induction motors) for variable-speed drives. This in general requires providing of voltages with adjustable frequency and amplitude. This is achieved most advantageously with pulsewidth-modulated (PWM) inverters. After an overview of the basic concepts, the different optimization criteria important for practical applications are discussed. Of special interest are efficiency optimization and torque-ripple optimization. These two optimization criteria are treated in detail. Computer simulations for both cases and experimental results for efficiency optimization are presented and compared. Special attention is given to the various switching laws generating the PWM for the inverters and to the voltage and current spectra associated with them. The differences in drive dynamics optimization are also discussed