This paper provides analytical and graphical methods for the study, performance evaluation and design of the modern carrier-based pulse width modulators (PWMs), which are widely employed in PWM voltage-source inverter (VSI) drives. Simple techniques for generating the modulation waves of the high-performance PWM methods are described. The two most important modulator characteristics-the current ripple and the switching losses-are analytically modeled. The graphical illustration of these often complex multivariable functions accelerate the learning process and help one understand the microscopic (per-carrier cycle) and macroscopic (per fundamental cycle) behavior of all the modern PWM methods. The analytical formulae and graphics are valuable educational tools. They also aid the design and implementation of the high-performance PWM methods.

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Simple analytical and graphical methods for carrier-based PWM-VSI drives

In this paper, a generalized discontinuous pulsewidth modulation (GDPWM) method with superior high modulation operating range performance characteristics is developed. An algorithm which employs the conventional space-vector PWM method in the low modulation range, and the GDPWM method in the high modulation range, is established. As a result, the current waveform quality, switching losses, voltage linearity range, and the overmodulation region performance of a PWM voltage-source inverter (PWM-VSI) drive are optimized online, as opposed to conventional modulators with fixed characteristics. Due to its compactness, simplicity and superior performance, the algorithm is suitable for most high-performance PWM-VSI drive applications. This paper provides detailed performance analysis of the method and compares it to the other methods. The experimental results verify the superiority of this algorithm to the conventional PWM methods.

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A high-performance generalized discontinuous PWM algorithm

In this paper, a novel voltage modulation technique named unified PWM (pulse width modulation) for high performance voltage generation in a voltage-fed inverter is described. As increasing the interest in the high quality power conversion is, a simple PWM scheme that has the wide fitness to the general prospect for the loss minimization and the lowest current harmonic with full DC link voltage utilization is required. From the synthesis of the actual inverter action, a simple but useful concept for the 'effective time' is established. And, fully employing this concept, a new voltage modulation technique for various applications is presented with detailed explanation and actual test results. Implementing this facile strategy to actual fields will result in great reduction of calculation efforts and high applicability including the minimization of switching loss and current harmonics.

Unified voltage modulation technique for real time three-phase power conversion

The theory, design, and implementation of a constant-frequency hysteresis current control for grid-connected voltage source inverter (VSI) is presented. The proposed control technique retains the benefit of the hysteresis control having fast dynamic response and tackles the drawback of the standard hysteresis control having variable switching frequency. The concept is based on predicting the current reference, system dynamic behavior, and past time to formulate the switching function for dictating the switching times of the switches in the inverter within a predefined switching period. Of particular importance, no hysteresis bandwidth (a challenge in the practical implementation) is needed in the entire control method. The operating principles of the proposed technique and mathematical derivation of the switching functions will be given. The proposed method is successfully applied to a 300 W, 110 V, 60 Hz grid-connected VSI prototype with the controller implemented by a simple analog circuit. The steady-state and large-signal dynamic response of the VSI are studied. Experimental results show that the inverter can reach the steady state in two switching actions after the inverter is subject to large-signal input and output disturbances.

Constant-Frequency Hysteresis Current Control of Grid-Connected VSI Without Bandwidth Control

This article reviews the nonsinusoidal CPWM and SVPWM techniques and deals with the three possibilities of calculation of pulsewidths after the addition of a zero-sequence signal. A general algorithm is proposed and adapted for dealing with the control of the three-level NPC inverter and also the Z-source converter. Experimental results corroborate the proposed technique.

Pulsewidth Modulation Strategies

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. >

Y. Ogino

Papers

PWM technique for power MOSFET inverter