Three-phase Pulse Width Modulation Inverter Research Articles

Input ripple analysis of five-phase pulse width modulated inverters

Input ripple analysis of five-phase pulse width modulated (PWM) inverters is presented. The analytical expressions for the rms value of the input current and voltage ripples as a function of the PWM reference signal are derived. Similar to three-phase PWM inverters, the input current ripple does not depend on the employed reference signal, so the ripple cannot be minimised by changing the shape of reference signal. On the other hand, different from three-phase PWM inverters, it is shown that a pure sinusoidal signal is the optimum reference signal that produces a minimum input voltage ripple in five-phase PWM inverters. Input voltage ripples under several modulation techniques are compared. Experimental results are included to verify the proposed analysis method.

Analysis and Reduction of Time Harmonic Rotor Loss in Solid-Rotor Synchronous Reluctance Drive

Synchronous reluctance machines with solid rotor construction have advantages in certain high-speed applications such as flywheel energy storage systems. However, the solid rotor allows the flow of eddy currents, resulting in rotor loss and heat generation. The switching harmonics in the stator voltage supplied by a pulsewidth modulation (PWM) inverter are one of the sources of the rotor loss. This paper performs an analysis for the time harmonic loss in a solid-rotor synchronous reluctance machine, and investigates design and control issues associated with the inclusion of a three-phase LC filter for reduction of the rotor loss in solid rotor. A two-phase dynamic model of the machine which incorporates the LC filter dynamics is presented. This model is used to predict rotor losses due to switching harmonics generated by the three-phase PWM inverter. A model-based current regulator is utilized, which is modified to include the effects of the LC filter. Experimental results validate the proposed approach.

A Three-Phase UPS That Complies With the Standard IEC 62040-3

This paper proposes a down-sampled discrete-time internal-model-based controller in the synchronous reference frame with a reduced number of poles. This controller is suitable for three-phase pulsewidth modulation inverters with output transformer for double-conversion uninterruptible power supply applications. It is demonstrated that the use of a down-sampled rate and fewer poles in the internal model results in a number of benefits, among which are the following: 1) improvement of the transient response; 2) increase of the stability margin of the closed-loop system; 3) a straightforward implementation in fixed-point digital signal processor (DSP) and microcontroller implementation as well as a reduction of the required memory space; and 4) a simple solution for the saturation of the output transformer. As a result, it is possible to obtain output voltages with reduced total harmonic distortion while ensuring good transient performance for both linear and nonlinear loads. To confirm the advantages claimed for the proposed synchronous reference dq frame internal-model-based controller and to demonstrate the steady-state and transient performance under the test conditions of the International electrotechnical commission standard 62040-3, the experimental results from a 10-kVA space-vector-modulated three-phase inverter, which is fully controlled by a DSP TMS320F241, are presented.

PMモータ駆動に適した変形台形波変調信号

In this paper, a new modulating signal for pulse width modulation (PWM) inverter system suitable for Permanent Magnet synchronous motor (PMSM) drive is proposed. The PMSM with the sinusoidal electromotive force (EMF) driven by the non-sinusoidal PWM voltage generates a torque ripple. And, the torque ripple is similarly generated in PMSM with the trapezoidal EMF driven in the sinusoidal PWM voltage. The new PWM strategy makes a great improvement of the characteristics in the three-phase PWM inverter for the PMSM. The proposed PWM strategy can reduce torque ripple more than sinusoidal PWM method. Although the output voltage waveform is a non-sinusoidal waveform, the motor driven by the proposed modulating signal produces approximately constant torque. By using the proposed modulating signal, the amplitude of the fundamental component is increased more than that of a conventional sine wave inverter. The usefulness of the proposal method was confirmed by a theoretical analysis, the simulation by modeling the system, and the experiments.

Wavelet-fuzzy-based algorithm for condition monitoring of voltage source inverter

A real-time condition monitoring algorithm for a three-phase pulse width modulation inverter in a fuzzy controlled induction machine is developed. It is designed to detect and identify the transistor open-circuit fault and intermittent misfiring fault, which commonly occurs in the drive system. The condition monitoring mechanism is based on discrete wavelet transform and fuzzy logic. The developed system has been rigorously assessed theoretically and experimentally, and it has been shown that the system is robust and reliable.

A new modular motor-modular inverter concept for medium-voltage adjustable-speed-drive systems

In this paper, a new modular motor-modular inverter concept for medium-voltage adjustable-speed drive (MV-ASD) systems is introduced. It is shown that standard MV motor winding connections can be reconnected into several three-phase groups, each powered by a separate three-phase pulsewidth modulation inverter, resulting in a high-performance MV-ASD system. The proposed approach is fault tolerant and can continue to operate at reduced power levels, under inverter and/or motor faults. An example 250 hp four-pole 60 Hz 2300 V/4160 V motor winding connection diagram along with the associated inverter configurations is analyzed. Results from analysis are presented on the aspects of faults and motor operation under partial winding excitation. Experimental results on a low-voltage (460 V) 10 hp ASD are demonstrated.

High power factor AC/DC/AC converter with random PWM

A three-phase AC/DC/AC converter is presented with a power factor preregulator to improve the power quality in the input side and a pseudorandom noise generator to reduce the emitted acoustic noise and the mechanical vibration for an induction motor drive. The space vector modulation with hysteresis current control for a voltage source rectifier is adopted to simplify the hardware circuit. A control scheme is presented to drive the supply current following the reference current. The amplitude of reference current for the pulsewidth modulation (PWM) rectifier is derived from the DC bus voltage regulator and the estimated output power. Random switching frequency technique for a three-phase PWM inverter system to reduce the annoying tonal noise and resonant vibration from an induction motor is described. By randomly varying the instantaneous PWM switching frequency from one cycle to the next, the frequency distribution of harmonics is spread in a wide frequency range. The major advantage for using such a strategy is the nonrepetitive output spectral characteristic that results in reduction of torque pulsations in motor drive systems. The nearly unity power factor at the three-phase rectifier and the absence of acoustic noise concentrated at the specific tones which is usually present with conventional sinusoidal modulation are verified by the experimental tests.

How to include the dependency of the R/sub DS(on/) of power MOSFETs on the instantaneous value of the drain current into the calculation of the conduction losses of high-frequency three-phase PWM inverters

In this paper, the conduction losses of power MOSFETs are calculated analytically for application in three-phase voltage DC-link pulsewidth modulation (PWM) power converter systems. Contrary to a conventional calculation, the dependency of the turn-on behavior on the drain current is considered in terms of a quadratic approximation. The derived relationships are represented graphically; they can be included directly into the dimensioning of the power transistors.

Fuzzy-tuning current-vector control of a three-phase PWM inverter for high-performance AC drives

This paper proposes a new discrete fuzzy-tuning current-vector control (FTC) scheme for three-phase pulsewidth modulation (PWM) inverters. The proposed current control scheme can achieve fast transient responses and, at the same time, have very low total harmonic distortion in output current during steady-state operation. The proposed FTC scheme generates quasi-optimum PWM patterns by using a closed-loop control technique with instantaneous current feedback. The proposed FTC scheme has been realized using a single-chip digital signal processor (TMS320C14) from Texas Instruments. Experimental results are given to verify the proposed fuzzy-tuning current control strategy for three-phase PWM inverters.

Low-distortion variable-level PWM technique

A multicarrier disposition pulse width modulation (PWM) technique that results in low harmonic distortion for a three-phase PWM inverter with a 5-level line-to-line output voltage waveform is discussed in the paper. Comparison with the conventional 5-level unipolar PWM technique for three-phase inverters reveals that the proposed strategy results in a high performance converter with minimised filter requirements since the amplitude of all harmonics is reduced. The resulting line-to-line voltage waveform has five levels at high and three levels at low amplitude modulation indexes (variable-level). Harmonic analysis is presented, along with simulated and experimental results to support the theoretical considerations.

FPGA realization of space-vector PWM control IC for three-phase PWM inverters

This paper presents a new circuit realization of the space-vector pulse-width modulation (SVPWM) strategy. An SVPWM control integrated circuit (IC) has been developed using state of-the-art field-programmable gate array (FPGA) technology. The proposed SVPWM control scheme can be realized using only a single FPGA (XC4010) from Xilinx, Inc. The output fundamental frequency can be adjusted from 0.094 to 1500 Hz. The pulse-width modulation (PWM) switching frequency can be set from 381 Hz to 48.84 kHz. The delay time for the PWM gating signals is adjustable. This SVPWM IC can also be included in the digital current control loop for stator current regulation. The designed SVPWM IC can be incorporated with a digital signal processor (DSP) to provide a simple and effective solution for high-performance AC drives. Simulation and experimental results are given to verify the implemented SVPWM control IC.

Discrete-time current control of voltage-fed three-phase PWM inverters

The discrete-time current control of three-phase voltage-fed pulsewidth modulation (PWM) inverters is discussed, with emphasis on important practical aspects. The inverter feeds a balanced three-phase load of R-L impedances in series with back-EMFs. The inverter-load system is modeled by using space vectors. The practical difficulties of the predictive control method are pointed out. In particular, effects of the delayed application of the manipulated voltage caused by controller computing time are investigated. A modified control law that eliminates the undesirable effects of the computing delay is introduced. Also, prediction of current reference is utilized, which would enable operation with any reference function. An estimation and prediction procedure for the back EMF is also introduced. Steady-state errors in the load current due to these predictions are calculated for sinusoidal operation. Simulation results for the predictive control and the modified control laws are presented and discussed.

A simple and accurate method of computing average and RMS currents in a three-phase PWM inverter

The design of three-phase pulse-width-modulated (PWM) inverters requires values for the average and RMS currents in the inverter in order to select the right components. A computer-aided investigation of approximate inverter current waveforms indicates that the average and RMS inverter currents are simple functions of a single factor equal to the product of the power factor and the modulation index. These functions are expressed as per-unit equations that are useful not only for designing new inverters, but also for evaluating existing designs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

PWM technique for power MOSFET inverter

A sinusoidal PWM (pulsewidth-modulated) inverter suitable for use with power MOSFETs is described. The output waveforms in the proposed PWM inverter are investigated both theoretically and experimentally. A modulating signal for the three-phase PWM inverter is obtained by adding the harmonic components of integer multiples of three to the three-phase sine waves. By using the proposed modulating signal, the amplitude of the fundamental component is increased about 15% more than that of a conventional sine-wave inverter and the commutation number of the inverter is decreased to two-thirds of a conventional one. >

Microprocessor Control of DC/AC Static Converters

Microprocessor control of power electronic systems offers the possibility of improvements in reliability, maintenance and servicing, and increased control flexibility. This paper describes several pulsewidth modulation (PWM) waveforms where a predetermined number of unwanted harmonics can be canceled. The advantages and disadvantages of the different methods of delaying the signals in small microprocessor controlled PWM inverter drive systems are considered. Several examples of single-phase and three-phase PWM inverters, with the laws which govern the commutation angles, output waveforms, and their respective frequency spectra are presented.

Modulation of the Chopping Frequency in DC Choppers and PWM Inverters Having Current-Hysteresis Controllers

In a dc chopper converter having its load current regulated by a feedback controller of the fixed hysteresis type, the chopping frequency is shown to depend on the square of the counter EMF of the load. In a pulsewidth modulated (PWM) inverter, the counter EMF is modulated at the output frequency, so the chopping frequency is modulated at twice the output frequency. For a three-phase PWM inverter feeding a three-wire load, the chopping frequency modulation is not smooth. This is explained to be a consequence of the fact that the three phase currents must sum to zero, rendering one of the three current controllers redundant.

Harmonic Analysis of a Synchronized Pulse-Width-Modulated Three-Phase Inverter

In pulsewidth-modulated inverters used for variable-frequency applications, a number of harmonic control policies can be used. Most of these policies are complex to implement by hardware. The most simple and yet effective technique is synchronizing or the synchronized harmonic control policy. This paper uses double Fourier analysis techniques to obtain the output harmonics as a function of pulsewidth, pulsing frequency, and output frequency. The method obtains the harmonics as analytical functions and thus provides the necessary relationships for control studies and system optimization. The more significant theoretical results are provided and theoretical and experimental results obtained from a 25-kW three-phase pulsewidth-modulated inverter, are compared.

Output Voltage in Three-Phase Pulsewidth-Modulated Inverters

A theoretical analysis of pulsewidth control in three-phase pulsewidth-modulated inverters, is presented. Two general classifications of commutation schemes are discussed with respect to controllability of output voltage and commutation requirements. It is shown that for one scheme the output waveform is always defined regardless of load conditions but for the other scheme the output waveform is dependent on the load. A method of analysis is described whereby the output voltage, in the latter case, can be determined for sinusoidal load currents. Another method is then introduced whereby these results can be extended to applications with nonsinusoidal load currents.