Vector Pulse Width Modulation Technique Research Articles

An Efficient Multilevel Inverter System for Reducing THD with Space Vector Modulation

paper proposes a generalized space vector pulse width modulation (SVPWM ) technique for hybrid multilevel inverters for minimizing total harmonic distortion (THD). The proposed method easily determines the actual location of the instantaneous reference space vector and the corresponding switching sequence of a multilevel inverter. The proposed algorithm offers a novel method for minimizing the total harmonic distortion (THD) of the output voltage of the inverter and uses simple arithmetic for determining the sector and does not require lookup tables. The proposed method can be extended to any n-level inverter, and a generalized algorithm is also proposed. Finally, the algorithm was implemented on a Digital Signal Processor (DSP) and the scheme is explained for a five level inverter, and experimental r esults are presented for a seven level inverter.

Direct-Matrix-Converter-Based Drive for a Three-Phase Open-End-Winding AC Machine With Advanced Features

This paper describes how matrix converters (MCs), one at each side of a three-phase open-end-winding ac machine, achieve the following features simultaneously: 1) machine phase voltage up to 1.5 times the input phase voltage in the linear modulation mode, therefore extending the rated torque operation region to 150% of the rated speed of the machine; 2) peak voltage stress across the slot insulation which is limited to the peak of input phase voltage, i.e., a factor of at least √3 lower as compared to the conventional back-to-back converter; 3) controllable grid power factor to be leading, lagging, or unity; and 4) elimination of the instantaneous common-mode voltage at the machine terminals, therefore eliminating the bearing current due to switching common-mode voltage and reduction in the conducted electromagnetic interference. To simultaneously achieve the aforementioned capabilities, a space vector pulsewidth modulation technique is described in which the MCs are modulated using only rotating space vectors. A hardware prototype of the drive system is built. Experimental results from this hardware prototype verify the operation and claims of the drive system.

Development, Implementation and Experimentation on a dSPACE DS1104 of a Direct Voltage Control Scheme

This paper proposes and develops a new direct voltage control (DVC) approach. This method is designed to be applied in various applications for AC drives fed with a three-phase voltage source inverter (VSI) working with a constant switching time interval as in the standard direct torque control (DTC) scheme. Based on a very strong min(max) criterion dedicated to selecting the inverter voltage vector, the developed DVC scheme allows the generation of accurate voltage forms of waves. The DVC algorithm is implemented on a dSPACE DS1104 controller board and then compared with the space vector pulse width modulation technique (SVPWM) in an open loop AC drive circuit. To demonstrate the efficiency of the developed algorithm in real time and in closed loop AC drive applications, a scalar control scheme for induction motors is successfully implemented and experimentally studied. Practical results prove the excellent performance of the proposed control approach.

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.

Scalar PWM algorithms for four-switch three-phase inverters

Four-switch three-phase inverters (FSTPIs) have been proposed to be used in low-cost applications because of the reduced number of semiconductor devices, and space vector pulse width modulation (SVPWM) techniques have also been introduced to control FSTPIs. However, high-performance controllers are needed to implement complicated SVPWM algorithms, which limits their low-cost applications. To simplify algorithms and reduce the cost of implementation, an equivalent scalar method for SVPWM of FSTPIs is proposed. SVPWM for FSTPIs is actually a sine PWM by modulating two sine waves of 60° phase difference with a triangle wave, so such a special sine PWM can be used to control FSTPIs. The simulation and experimental results demonstrate the validity of the proposed method.

Rotor Failures Diagnosis of Squirrel Cage Induction Motors with Different Supplying Sources

The growing application and the numerous qualities of induction motors (IM) in industrial processes that require high security and reliability levels has led to the development of multiple methods for early fault detection. However, various faults can occur, such as stator short-circuits and rotor failures. Traditionally the diagnosis machine is done through a sinusoidal power supply, in the present paper we study experimentally the effects of the rotor failures, such as broken rotor bars in function of the ac supplying, the load and show the impact of the converter from diagnosis of the machine. The technique diagnosis used is based on the spectral analysis of stator currents or stator voltages respectively according to the types of induction motor ac supplying. So, four different ac supplying are considered: ? the IM is directly by the balanced three-phase network voltage source, ? the IM is fed by a sinusoidal current source given the controlled by hysteresis, ? the IM is fed (in open loop) by a scalar control imposing through ratio V/f=constant, ? the IM is controlled through a vector control using space vector pulse width modulation (SVPWM) technique inverter with an outer speed loop.

VLSI-cell placement technique for Architecture of Field Programmable Gate Array (FPGA) design

The Field Programmable Gate Array (FPGA) is an on field programmable device which can be designed for different applications. Various types of software are available for its synthesis. The cell placement depends upon the designing and programming languages used for FPGA. In this paper cell placement technique of FPGA architecture is analyzed for the application of Space Vector Pulse Width Modulation (SVPWM) technique used in speed control of an induction motor. The modulation pulses are produced due to the various components activated and their interconnection in Configurable Logic Blocks (CLBs). Few of its components are so analyzed to find out the reason for their desired output response. This survey has also been conducted to find the correlation of LUTs and formulation of output.

Full Utilization of the Inverter in Split-Phase Drives by Means of a Dual Three-Phase Space Vector Classification Algorithm

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> A simple and effective space vector pulsewidth-modulation technique for six-phase voltage-source-inverter-fed split-phase induction motors is presented in this paper. The approach employs dual three-phase space vector modulators equipped with overmodulation schemes that compensate for the voltage gain reduction due to the use of two independently controlled three-phase inverters. It secures full control of the voltage gain up to the maximum achievable gain with negligible low-order harmonics and utilizes a simple classification algorithm for the implementation of the space vector modulation (SVM) in both linear and overmodulation modes. Experimental results are provided to verify the validity of the proposed SVM split-phase approach. </para>

Achieving Maximum Efficiency in Three-Phase Systems With a Shunt Active Power Compensator Based on IEEE Std. 1459

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> IEEE Standard 1459–2000 establishes that in an efficient electrical system, only the fundamental positive-sequence active power must be present. This paper proposes a new set of reference currents based on the IEEE Standard 1459–2000 for the control of a three-branch four-wire shunt active power compensator. Reactive, unbalance, and harmonic distortion phenomena can be cancelled out upstream from the point of connection, achieving maximum efficiency of the three-phase four-wire electrical system. In addition, a new current control and a three-dimensional space vector pulsewidth-modulation technique are proposed to develop a shunt active power compensator. Simulation and experimental results demonstrate that the proposed shunt active power compensator improves the upstream electrical quality of the power network, achieving maximum efficiency according to IEEE Standard 1459–2000 specifications. </para>

Control of a Fuel Cell Based Z-Source Converter

This paper presents system modeling, modified space vector PWM implementation (MSVPWM), and control system design of a Z-source converter. For an electrical analysis of the fuel cell powered systems, the fuel cell system is modeled by an R-C circuit including its voltage-current polarization characteristics. A discrete-time state space equation is given to implement digital control and a space vector pulse-width modulation technique is modified to realize the shoot-through zero vectors that boost the dc-link voltage. Three discrete-time controllers and an asymptotic observer are designed.

DSP based inverter control for alternate energy systems

This paper presents a DSP based algorithm to control inverters used in interfacing alternate energy systems with the electric utility. Since a constant and ripple free dc bus voltage is not ensured at the output of alternate energy sources, the main aim of the proposed algorithm is to make the output of the inverter immune to the fluctuations in the dc input voltage. In this paper a modified space vector pulse width modulation (SVPWM) technique is proposed which will maintain the quality of the ac output of the inverter, regardless of the ripple present at the inverter input. The principle is explained qualitatively and extensive experiments have been carried out to verify and validate the proposed algorithm. A 16-bit fixed-point C2000 family DSP from Texas Instruments was used as the controller to implement the proposed control algorithm.

Reduced Switch Count DC-Link AC–AC Five-Leg Converter

This paper investigates a reduced switch count dc-link ac–ac five-leg converter for three-phase power conversion. The converter provides both an input rectifier and an output inverter by sharing a leg in order to reduce the number of power switches. Scalar and vector pulsewidth modulation techniques are presented and the concepts of local and global apportioning factors are introduced. A control technique that aims at maximizing the utilization of the dc-link voltage is proposed. A hysteresis current controller that allows operating with one leg being shared by the load and grid sides is developed. In addition, several relevant characteristics of the converter are addressed, such as voltage capability, harmonic distortion, shared-leg and capacitor currents, and power rating. The features of such a converter are compared to those of the six-leg and four-leg converters. Selected experimental results are presented.