Phase PWM Research Articles

New three phase VFVA sine wave generator and PWM harmonics analysis

The new three phase VFVA sine wave generator is presented in this paper. A new sampling holding three phase VFVA sine wave generator's pcinciple, circuit and experimentation waveform are introduced. The principle of this sampling holding circuit is simple and the realization of har'dware circuit is easy. Here we describe the three phase reference sine wave which is produced by this generator's circuit and is required by PWM inverter is described in this paper, and also introduced the speed control and harmonic analysis of PWM inverter variable frequency.

Digital Control of Three Phase PWM Inverter for UPS Application based on Disturbance Observer and Deadbeat Control.

A new approach to digital feedback control of PWM inverter is proposed, in which an output DB (dead beat) control is achieved with a disturbance observer. In this scheme, the state observer and disturbance observer are used, and pole placement of these two observers are chosen separately. When these observers employ the same pole placement, the system has tendency to become unstable. By selecting the different pole placement, the disturbance observer only eliminates the disturbance, and state observer only estimates the state variable of the next sampling instant.From the view point of UPS applications, the advantages and disadvantages are discussed through simulations and experiments.

Modelling and analysis of a three phase PWM AC—DC convertor without current sensor

The familiar state space averaging technique for DC–DC converters is extended for modelling a three-phase AC–DC convertor without current sensor. The space vector representation technique is used to simplify greatly the modelling process without sacrificing the accuracy and valid frequency range. Both steady-state and small-signal analyses are made. The results show that for the proposed duty ratio control law the convertor can achieve an ideal property, namely, sinusoidal input current with unity power factor, zero output voltage ripple resulting from line frequency and fixed switching frequency. Moreover, the convertor also possesses the regenerative capability which is useful for many applications. Finally, some experimental results are presented for verification.

Analysis of the voltage harmonics of PWM voltage fed inverters using high switching frequencies and different modulation functions

AbstractThis paper presents different methods to determine the harmonics of pulse width modulated patterns by means of a minimum on mathematical equations. The first solution is based on a FFT algorithm and allows detailed investigations for a low frequency ratio of the PWM. The second solution consists of a single expression by which any harmonic based on a high switching frequency can be determined. It can, however, also be applied at low frequency ratios above z 15 and takes different modulation schemes into account. Starting from the pure sinusoidal PWM a third harmonic can be injected, the space vector modulation can be applied or the flat top modulation can be considered. The third approach calculates the most important harmonics of the PWM by a simple equation which can be solved without numerical help. The results of the paper are suitable for three phase PWM transistor inverters in electrical drives or in line converters.

Pulsewidth Modulation Techniques for Low Cost Voltage Source Inverter Applications

Optimized PWM techniques have been developed and used with good results for voltage source inverters. However, implementation frequently requires complex electronic circuits, usually microprocessor-based, that cannot be justified in low cost applications. The paper examines three phase PWM pattern generators that are simple to implement with low cost circuitry, particularly with analog components. These modulation techniques are based on the model reference adaptive (MRA) technique. They exhibit intrinsic constant Volts/Hertz operation, and do not require frequency synchronization and frequency jumping, making them ideal for low cost inverter driven variable speed ac motor drives. The PWM patterns are generated by forcing the current in the built-in load model to follow a reference, by means of hysteresis control, also known as the delta modulation technique, or error triangulation control. Unlike delta modulation, the latter technique exhibits constant switching frequency and has an output voltage spectrum similar to that of the well-known sine PWM technique. The paper includes the principles of operation, the control circuit structure and implementation and the features of the PWM patterns.

DSP based real time output waveform synthesis for three phase PWM inverter.

A new digital control technique is proposed to synthesize arbitrary three phase PWM inverter output. Sensing two line-to-line voltages, the required pulse patterns for deadbeat response are computed in real time manner, based on the predicted voltage by an observer at 18kHz sampling frequency. When used for the uninterruptible power supply, this closed loop voltage control inherently results in a very low THD and a very quick transient response with the less filter capacity. Also with repetitive compensator, the proposed scheme has advantages in improving the output waveform for non-linear load. This paper describes modeling technique, theoretical analysis, simulations and experimental results.

A Study on Harmonic Elimination Method of PWM Inverter Fed Induction Motor System Using Walsh Series

Microprocessor control of power electronics systems offers the possibility of improvements in variability, maintenance and servicing, and increased control flexibility. This paper describes the new algorithm for elimination of unwanted harmonics and control of the fundamental amplitude in the three phase PWM inverter output waveform. in other words, this paper is presented technique of the particular harmonics eiimination(PHE) by waish series in three phase PWM inverter output waveform. A microprocessor(8086 CPU) - controlled three phase induction motor system realizing this algorithm is presented. It is designed for a three output voltage in the 1~45Hz inverter with the 5th and 7th harmonics eliminated, and with the fundamental wave amplitude proportional to the output frequency. The performance of the proposed method has been greatly improved with respect to an earlier realization proposed by the authors. In the future, the proposed PWM pattern by Walsh series, is effective not only to the induction motor but also to the other electromagnetic machine such as voltage regulator, UPS.

Current control of 3-phase PWM converter with due regard to parameter variation.

Current control of 3-phase PWM converter with due regard to parameter variation.

Finite time settlement control of three phase PWM inverter.

Finite time settlement control of three phase PWM inverter.

Computer-aided design of PWM inverter systems

The increasing availability of digital computers now makes the computer-aided design of powerelectronic systems an attractive and cost-effective development tool. The paper describes the detailed development of an extremely versatile PWM computer modelling package which can be used as a `stand-alone′ package for harmonic analysis, or alternatively as a `building-block′ for developing more complex systems. The capabilities of the package are demonstrated, using a number of examples of single-phase and 3-phase PWM inverters, which serve to highlight a number of important operational characteristics of PWM inverters. The validity and accuracy of the computer simulations are confirmed, using experimental results obtained from a microprocessor-controlled PWM inverter-drive system.

Analysis and Design Procedure for a Three Phase PWM Inverter-Induction Motor Drive

SUMMARY Design procedures for a variable frequency, PWM, inverter-induction motor pump drive that is self-protecting for overload conditions are presented. System design parameters, including component deratings resulting from voltage harmonics and overload protection circuits, are systematically established. A Double Fourier Analysis Technique is used to derive harmonic voltages. It is demonstrated that the control system must limit the rate of voltage reduction for stable current regulation. The inverter features certain unique circuits and thyristor control techniques. A novel commutation circuit design graph that generates design data from parameters such as peak load current, thyristor di/dt rating, etc. is presented. Selected performance characteristics of a 220 V, 60 Hz, 15 hp drive are presented.