Pulse multiplication in AC-DC converters for harmonic mitigation in vector-controlled induction motor drives

In this paper, an autotransformer with reduced kilovoltampere rating for 24-pulse ac-dc converter fed vector controlled induction motor drives (VCIMDs) is presented for harmonic current reduction. The 24-pulse operation is achieved using dc ripple reinjection technique in 12-pulse ac-dc converters. The proposed novel harmonic mitigator is found capable of suppressing up to 21st harmonic in the supply current. The procedure for the design of autotransformer for proposed ac-dc converter is presented to show the flexibility in the design for making it a cost-effective replacement suitable for retrofit applications, where presently a 6-pulse diode bridge rectifier is used. The effect of load variation on VCIMD is also studied to demonstrate the effectiveness of the proposed ac-dc converter. A set of power quality indices on input ac mains and on dc bus for a VCIMD fed from other 24-pulse ac-dc converters are also given to compare their performance. The laboratory prototypes of proposed autotransformers based 12-pulse and 24-pulse ac-dc converters are developed and test results are presented to validate the developed design procedure and the simulation models of these ac-dc converters under varying loads.     

A 40-Pulse AC--DC Converter Fed Vector-Controlled Induction Motor Drive

In this paper, a novel autotransformer for a 40-pulse ac-dc converter configuration is designed, modeled, simulated, and implemented to feed vector-controlled induction motor drive (VCIMD). The proposed converter consists of two paralleled ten-pulse ac-dc converters along with pulse doubling circuit at dc bus. Each ten-pulse ac-dc converter involves five-phase diode bridge rectifiers. It improves power quality at ac mains, and it meets IEEE-519 standard requirements at varying loads. A set of power quality indexes on input ac mains and dc bus for a VCIMD fed from 20-pulse and 6-pulse converters is also given to compare their performance. It is observed that input current total harmonic distortion (THD) of much less than 5% is possible with the proposed topology at varying loads.     

Harmonic Mitigation in AC–DC Converters for Vector Controlled Induction Motor Drives

This paper deals with autotransformer-based multipulse ac--dc converters with reduced magnetics feeding vector controlled induction motor drives for improving the power quality at the point of common coupling. The proposed 12-pulse ac--dc converter-based harmonic mitigator consists of an autotransformer alongwith a passive shunt filter tuned for 11th harmonic frequency. This results in the elimination of 5th, 7th, and 11th harmonic currents. Similarly, the proposed 18-pulse ac--dc converter-based harmonic mitigator eliminates the 5th, 7th, 11th, 13th, and 17th harmonic currents, thereby improving the power quality at ac mains. The experimentation is carried out on the developed prototype of autotransformers-based ac--dc converters. Different power quality indexes of the proposed 12-pulse and 18-pulse ac--dc converters are obtained from simulation and verified from experimental results.     

Power Quality Improvement in Conventional Electronic Load Controller for an Isolated Power Generation

This paper deals with the power quality improvement in a conventional electronic load controller (ELC) used for isolated pico-hydropower generation based on an asynchronous generator (AG). The conventional ELC is based on a six-pulse uncontrolled diode bridge rectifier with a chopper and an auxiliary load. It causes harmonic currents injection resulting distortion in the current and terminal voltage of the generator. The proposed ELC employs a 24-pulse rectifier with 14 diodes and a chopper. A polygon wound autotransformer with reduced kilovolts ampere rating for 24-pulse ac–dc converter is designed and developed for harmonic current reduction to meet the power quality requirements as prescribed by IEEE standard-519. The comparative study of two topologies, conventional ELC (six-pulse bridge-rectifier-based ELC) and proposed ELC (24-pulse bridge-rectifier-based ELC) is carried out in MATLAB using SIMULINK and Power System Blockset toolboxes. Experimental validation is carried out for both ELCs for regulating the voltage and frequency of an isolated AG driven by uncontrolled pico-hydroturbine.      

A Hybrid Converter System for High-Performance Large Induction Motor Drives

A hybrid converter system employing a combination of a load-commutated inverter (LCI), a dc–dc buck converter, and a voltage-source inverter (VSI) is proposed for the large induction motor drives. The VSI ensures the safe commutation of the LCI with active commutation angle control over all speed regions. By replacing capacitor banks and a forced dc-commutation circuit, this system can eliminate all drawbacks related to these circuits in the conventional LCI-based induction motor drives. Sinusoidal motor current and voltage waveforms are achieved with the VSI providing the reactive and harmonic power to the motor, resulting in high-performance drives. The buck converter enables both the VSI and the LCI to be fed from the single-diode rectifier. As a result, the dc-link inductor size can be reduced and the LCI is operated without the controlled rectifier. In addition, faster dynamic response can be obtained through the VSI and the buck converter operation. Finally, the buck converter performs the dc-link current control to ensure minimum VSI rating. The feasibility of the proposed hybrid circuit for the high-power drive systems is verified by computer simulation for a 500-hp induction motor. Experimental results are also included for a 1-hp induction motor laboratory setup controlled by the proposed hybrid system.     

Simple Power Control for Sensorless Induction Motor Drives Fed by a Matrix Converter

This paper presents a new and simple method for sensorless control of matrix converter drives using a power flowing to the motor. The proposed control algorithm is based on controlling the instantaneous real and imaginary powers into the induction motor. To improve low-speed sensorless performance, the nonlinearities of a matrix converter drive such as commutation delays, turn-on and turn- off times of switching devices, and on -state switching device voltage drop are modeled using a PQ power transformation and compensated using a reference power control scheme. The proposed sensorless control method is applied for the induction motor drive using a 3 kW matrix converter system. Experimental results are shown to illustrate the feasibility of the proposed strategy.      

Harmonic reduction in adjustable-speed synchronous motors

Adjustable-speed synchronous motors (ASSM) are very popular in high-power high-speed applications. The Chilean mining industry uses them in milling operations in ranges of several thousands hp. Although a high pulse number for the inverter would be beneficial, it never goes beyond 12, due to complicated connections. Thus, a distorted harmonic-rich current feeds the synchronous motor, increasing the inverter commutation angle and causing additional rotor-heating and pulsating electric torque. Harmonic suppression by filters is not viable due to the variable frequency nature of the motor. In this paper, a new design for the inverter, without complicated circuitry, is proposed, so that it works with 36 pulses and then the motor is fed with a highly sinusoidal current. Also, the same technique is applied to the rectifier end, so that an effective harmonic reduction is carried out at both ends of the system, i.e., the motor as well as the AC supply system. A 20 kVA laboratory development drive system has been built and experimental waveforms for the conventional (12-pulse) and proposed (36-pulse) configurations are included     

Tracking control technique for induction motors

A novel application is presented of the tracking control technique to induction motor drive systems. By this technique, the position or the speed of the rotor can follow a preselected track (a time history of rotor position or velocity). An algorithm for the design of the tracking controller is developed. The induction motor model and the controller are modified to allow the inclusion of the nonlinear modes in the system without excessive computations. A simple and realistic criterion for selecting the proper reference tracks during starting, speed control and braking is proposed. The controller developed, is tested on a full-size nonlinear analog simulator. All test results show the effectiveness of the scheme in position-tracking applications such as robotics and manipulators     

In-wheel permanent-magnet brushless DC motor drive for an electricbicycle

This paper presents the design of an axial-field PM brushless DC motor drive for use on an electric bicycle. Details of the motor and the electronic converter are given. Performance analysis using the finite element method is briefly discussed. A prototype motor was constructed for verifying the actual performance. Good correlation between the theoretical and experimental results hs been obtained. Test results confirmed the feasibility of the proposed motor design     

Development of a novel wind turbine simulator for wind energy conversion systems using an inverter-controlled induction motor

A wind turbine simulator for wind energy conversion systems has been developed with a view to design, evaluate, and test of actual wind turbine drive trains including generators, transmissions, power-electronic converters and controllers. The simulator consists of a 10-hp induction motor (IM) which drives a generator and is driven by a 10-kW variable speed drive inverter and real-time control software. In this simulator, a microcontroller, a PC interfaced to LAB Windows I/O board, and an IGBT inverter-controlled induction motor are used instead of a real wind turbine to supply shaft torque. A control program based on C language is developed that obtains wind profiles and, by using turbine characteristics and rotation speed of IM, calculates the theoretical shaft torque of a real wind turbine. Comparing with this torque value, the shaft torque of the IM is regulated accordingly by controlling stator current demand and frequency demand of the inverter. In this way, the inverter driven induction motor acts like a real wind turbine to the energy conversion system. The drive is controlled using the measured shaft torque directly, instead of estimating it as conventional drives do. The experimental results of the proposed simulator show that this scheme is viable and accurate. This paper reports the operating principles, theoretical analyses, and test results of this wind turbine simulator.     

Performance improvement of a slip energy recovery drive system by a voltage-controlled technique

This paper introduces the performance improvement of a slip energy recovery drive system for the speed control of a wound rotor induction motor by a voltage-controlled technique. The slip energy occurred in the rotor circuit is transferred back to ac mains supply through a reactor instead of a step up transformer. The objective of the voltage-controlled technique is to increase power factor of the system and to reduce low order harmonics of the input line current. The drive system is designed and implemented using a voltage source inverter in conjunction with a boost chopper for DC link voltage, instead of a conventional drive using a 6 pulse converter or a Scherbius system. The slip power is recovered by the help of a voltage source inverter (VSI) based on a space vector pulse width modulation (SVPWM) technique. In order to keep the speed of the wound rotor induction motor constant over a certain range of operating conditions, the servo state feedback controller designed by a linear quadratic regulator (LQR) is also introduced in this paper. The overall control system is implemented on DSP, DS1104’TMS320F240 controller board. The performance improvement of the proposed system is tested in comparison with the conventional Scherbius system and the modified conventional Scherbius system by a 12 pulse converter in conjunction with a chopper at steady state and at dynamic conditions. A 220 W wound motor is employed for testing. It is found that the motor speed can be controlled to be constant in the operating range of 450–1200 rpm at no load and full load. It is also found that the efficiency of the proposed system is remarkably increased since the harmonics of the input ac line current is reduced while the ac line input power factor is increased.     

Adaptive fuzzy-neural-network control for induction spindle motor drive

An induction spindle motor drive using synchronous pulse-width modulation (PWM) and dead-time compensatory techniques with an adaptive fuzzy-neural-network controller (AFNNC) is proposed in this study for advanced spindle motor applications. First, the operating principles of a new synchronous PWM technique and the circuit of dead-time compensator are described in detail. Then, since the control characteristics and motor parameters for high-speed-operated induction spindle motor drive are time varying, an AFNNC is proposed to control the rotor speed of the induction spindle motor. In the proposed controller, the induction spindle motor-drive system is identified by a fuzzy-neural-network identifier (FNNI) to provide the sensitivity information of the drive system to an adaptive controller. The backpropagation algorithm is used to train the FNNI online. Moreover, the effectiveness of the proposed induction spindle motor-drive system is demonstrated using some simulated and experimental results.     

Analysis of current source induction motor drive fed fromphotovoltaic energy source

The transient and steady-state analysis of an induction motor fed from a photovoltaic energy source through a current-source inverter is presented. It is shown that the steady-state and dynamic behaviors of the motor differ considerably from the case in which it is fed from a perfect current source. In particular, the steady-state capability of the motor is limited by the chopping ratio of the DC-DC converter and the switching frequency of the current-source inverter. Analysis of the small signal perturbation equations of the system shows that the system is lightly damped for operating voltages of the array that are less than that of the array voltage corresponding to array maximum output power. For some values of array voltage, it has a nonminimum phase characteristic due to the nonlinear relationship between the array voltage and current. This nonminimum phase characteristic adds an inherent difficulty to the design of a robust closed-loop feedback controller for the motor drive system     

Performance analysis of PV pumping systems using switched reluctance motor drives

A PV pumping system using switched reluctance motor (SRM) is thoroughly investigated in this work. This motor is supplied by a d.c. voltage through a simple switching circuit. This drive circuit is much simpler than the normal d.c./a.c. inverter required to supply the induction motor. The efficiency of this motor is considerably higher than that of the equivalent d.c. or induction motors. In addition, because of the simple construction, SRM is cheaper than these conventional drives. Because of the above advantages of the SRM, the proposed system has higher efficiency and lower cost as compared with other systems.A design example is studied in detail to explore the advantages of PV pumping systems based on this new drive. The study of the performance of the proposed system showed that the operating efficiency of the motor is about 85% during most of its working time. The matching efficiency between the PV array and the proposed system approaches 95%. The major part of the losses takes place in the pump and the riser pipes, this loss represents one-third of the total available energy.     

中频隔离型光伏±35kV/500kW直流变流器研究与工程应用

首先提出一种中频隔离型光伏±35 kV/500 kW直流变流器,该直流变流器由三相T型三电平并联中频逆变器模组、中频400 Hz/24脉波移相升压变压器、三相二极管整流桥以及高压滤波电路组成,该变流器具有升压比高、结构简单、成本低的优势;其次,为了实现逆变器并联模组有功、无功功率的实时均分,采用一种瞬时功率均分的功率主从控制方案;接着,提出一种基于中频变压器无功补偿的改进型LCL滤波器参数设计方法以提高变流器的效率。最后,通过Matlab/Simulink仿真以及张北国家大型风电并网系统研发（实验）中心建设的光伏发电中压直流汇集现场示范工程,对所提直流变流器的设计理念和控制方法进行验证,现场并网实测最大效率为96.33%,升压比高达88,输出电压±35 kV,仿真和实验结果证明了所提直流变流器的可行性。     

A fuzzy adapted field-oriented mechanism for induction motor drive

The detuning of an indirect field-oriented induction motor drive due to variation of rotor resistance may lead to low efficiency and poor transient response. To improve this, an induction motor drive with a fuzzy adapted field-oriented mechanism is proposed. During steady state conditions, an adapted slip angular speed signal is synthesized by a fuzzy controller and used to adjust the original estimate of slip angular speed signal such that minimum stator current is obtained. When the transient due to command or load torque change occurs, the fuzzy tuning mechanism is temporarily inhibited and the final value of the adapted signal is held. A discrete two-degree-of-freedom controller (2DOF) is designed to yield good speed command tracking and load regulating responses. The effectiveness of the proposed motor drive is demonstrated experimentally     

Compositive adaptive position control of induction motors based onpassivity theory

A passivity-based composite adaptive position control scheme for an induction motor is proposed in this paper. First, the dynamics of the induction motor are proved to be state strictly passive, and a composite adaptation algorithm is proposed to control the position of the induction motor. Then, the global stability of the induction motor position control system is formally proved by the passivity theory. Experimental results are provided to show that the good position tracking can be obtained without any information of the rotor flux. The proposed approach is robust to the variations of motor mechanical parameters and external load disturbances     

A new power supply for superconductive magnetic energy storagesystem

A power supply for a superconductive magnetic energy storage system is presented. It permits fast independent regulation of the active and reactive power. The power supply was built with several units connected in parallel. Each unit consists of a 24-pulse bridge converter, thyristor-switched tap-changing transformer, and thyristor-switched capacitor bank. System operation was analyzed by computer simulation, and a feasible system realization is shown. A superconductive magnetic energy storage system with the proposed power supply has the capability of leveling the load variation, damping the low-frequency oscillation, and improving the transient stability in the power system. This power supply can be built with commercially available components using well-proven technologies     

A high-performance induction motor drive with on-line rotortime-constant estimation

A high-performance induction motor (IM) speed drive with online adaptive rotor time-constant estimation and a proposed recursive least square (RLS) estimator is introduced in this paper. The estimation of the rotor time-constant is on the basis of the model reference adaptive system (MRAS) theory; and the rotor inertia constant, the damping constant and the disturbed load torque of the IM are estimated by the proposed RLS estimator, which is composed of an RLS estimator and a torque observer. Moreover, an integral proportional (IP) speed controller is designed online according to the estimated rotor parameters; and the observed disturbance torque is fed forward to increase the robustness of the induction motor speed drive     

A discrete adaptive induction position servo drive

A discrete adaptive induction position servo is designed and implemented. In the proposed servo system, the dynamic model of the indirect field-oriented induction motor is estimated from measurements using the stochastic approach. Based on this model, a PI speed controller and a P position controller are designed using pole-placement and root-locus techniques. In order to reduce the effects of machine and load parameter variations on the performance of the indirect field-oriented induction motor servo drive, an adaptive controller is augmented in which a reduced reference model, which defines the desired following control performance, is chosen and the adaptive control signal is synthesized. The proposed adaptive controller has the advantages of being easy to design and implement. Simulation and experimental results show that good following and regulating control performances are achieved. Moreover, the performances are rather insensitive to parameter variations