Akira Nabae

A New Neutral-Point-Clamped PWM Inverter

A new neutral-point-clamped pulsewidth modulation (PWM) inverter composed of main switching devices which operate as switches for PWM and auxiliary switching devices to clamp the output terminal potential to the neutral point potential has been developed. This inverter output contains less harmonic content as compared with that of a conventional type. Two inverters are compared analytically and experimentally. In addition, a new PWM technique suitable for an ac drive system is applied to this inverter. The neutral-point-clamped PWM inverter adopting the new PWM technique shows an excellent drive system efficiency, including motor efficiency, and is appropriate for a wide-range variable-speed drive system.

Instantaneous Reactive Power Compensators Comprising Switching Devices without Energy Storage Components

The conventional reactive power in single-phase or three- phase circuits has been defined on the basis of the average value concept for sinusoidal voltage and current waveforms in steady states. The instantaneous reactive power in three-phase circuits is defined on the basis of the instantaneous value concept for arbitrary voltage and current waveforms, including transient states. A new instantaneous reactive power compensator comprising switching devices is proposed which requires practically no energy storage components.

Control Strategy of Active Power Filters Using Multiple Voltage-Source PWM Converters

The control strategy of active power filters using switching devices is proposed on the basis of the instantaneous reactive power theory. This aims at excellent compensation characteristics in transient states as well as steady states. The active power filter is developed, of which the power circuit consists of quadruple voltage-source PWM converters. As the result, interesting compensation characteristics were verified experimentally which could not be obtained by the active power filter based on the conventional reactive power theory.

A new approach to harmonic compensation in power systems-a combined system of shunt passive and series active filters

A novel approach to compensate for harmonics in power systems is proposed. The approach differs from conventional passive and active filters in its compensation principle. A practical system configuration to implement the approach is presented. It consists of a small-VA-rating PWM (pulsewidth-modulated) converter and a passive filter. The compensation principle is described, and compensation characteristics are examined theoretically and experimentally. The practicability and validity of the approach are experimentally demonstrated.<<ETX>>

A Novel Control Scheme for Current-Controlled PWM Inverters

A high-performance current-controlled inverter must have a quick current response in transient state and low harmonic current content in steady state. However, in general, these requirements contradict each other. A novel control scheme is proposed which is based on the current deviation vector and satisfies both requirements. Experimental results showed good agreement with the anticipated performance.

Compensation characteristics of the combined system of shunt passive and series active filters

The transient compensation characteristics and stability of a combined system of shunt passive and small rated series active filters are discussed and analyzed theoretically and experimentally. The stable and unstable regions of the combined system and the problems faced when an attempt at improving transient compensation characteristics is made are revealed. A control method that allows the application of the combined system to compensation for cycloconverters is proposed. Some results obtained from the experimental model using the control method are presented to demonstrate its validity.<<ETX>>

A novel control scheme of a parallel current-controlled PWM inverter

A parallel technique for current-controlled pulse-width-modulated (PWM) inverters is described. Two voltage source inverters, the output terminals of which are connected in parallel through current balancers, are used as a main circuit. In this scheme, excellent characteristics both in steady states and in transient states are obtained, keeping the average values of the cross current and zero sequence current at zero level. This current control scheme is applicable to large-capacity GTO inverters because good performance is attained even if the switching frequency is only a few hundred hertz, as is shown in the experimental results. >

A novel PWM scheme of voltage source inverters based on space vector theory

ContentsA novel PWM scheme which can considerably reduce harmonic currents is proposed. It is explained analytically that the harmonic currents depend on the amplitude and phase angle of the reference voltage vector, the inverter output voltage vectors used in a switching period, and the sequence of these output voltage vectors. In the novel PWM scheme, the switching sequence is selected so that the harmonic currents are minimum. An experimental system which generates the PWM patterns by software at real time is constructed. Compared with the conventional sinusoidal PWM scheme, it is confirmed that the current ripple is decreased and the spectrum is shifted and dispersed to a higher frequency region.ÜbersichtEs wird ein neues Modulationskonzept vorgeschlagen, mit dem die Oberschwingungsströme beträchtlich herabgesetzt werden können. Wie analytisch gezeigt wird, hängen diese von Amplitude und Phasenwinkel des Zeigers der Referenzspannung, der Wechselrichter-Ausgangsspannung in einer Schaltperiode und der Abfolge der Zeiger dieser Ausgangsspannung ab. Nach dem neuen Konzept wird die Schaltfolge so gewählt, daß sich ein Minimum der Oberschwingungsströme ergibt. In einer Versuchseinrichtung wird das Pulsmuster durch Software in Echtzeit generiert. Im Vergleich mit der konventionellen Sinusbewertung bestätigt sich eine Verminderung der Welligkeit und eine Verschiebung des Oberschwingungsspektrums in den Bereich höherer Frequenzen.

Analysis and design of an active power filter using quad-series voltage source PWM converters

The modeling, analysis, and design of an active power filter using quad-series voltage-source PWM (pulsewidth-modulated) converters of voltage and current are used for the analysis. The vector differential equation derived makes it easy to achieve the analysis and design of the active power filter. Experimental waveforms obtained from a prototype active power filter having a rating of 7 kVA, along with simulation waveforms, are included to verify the theory.<<ETX>>

A new approach to harmonic compensation in power systems

A novel approach to compensate for harmonics in power systems is proposed. The approach differs from conventional passive and active filters in its compensation principle. A practical system configuration to implement the approach is presented. It consists of a small-VA-rating PWM (pulsewidth-modulated) converter and a passive filter. The compensation principle is described, and compensation characteristics are examined theoretically and experimentally. The practicability and validity of the approach are experimentally demonstrated. >