Resonant Link Inverter Research Articles

Quasi-resonant soft-switching inverter for low and high power factor loads

A novel quasi-resonant three-phase inverter is proposed for 400 or 50 Hz low and high power factor loads. The proposed quasi-resonant DC link consists of a total of four switches, two resonant inductors and a capacitor. Two switches are connected in series with the resonant DC link (RDCL) and the other two are connected across the RDCL. The quasi-resonant link topology is versatile and the operation is such that the DC link voltage is clamped to the source voltage. The soft-switching operation of the quasi-resonant inverter is explained in terms of modes for both positive and negative link current. The quasi-resonant inverter is operated under modified space vector modulation incorporating soft switching. SABER simulation of the resonant link inverter and subsequent experimental verification show good agreement.

Evaluation of actively clamped resonant link inverter for low-output harmonic distortion high-power-density power converters

The suitability of a soft-switched actively clamped resonant DC-link (ACRDCL) inverter for low-output harmonic distortion/high-power-density power conversion is evaluated. Modulation and control techniques for achieving low-output harmonic distortion are described. Performance and power density of the ACRDCL inverter are maximized through the optimal design of the clamp circuit, resonant components, and output filter components. The ACRDCL inverter simulation and design are validated experimentally. For the same output kilovoltamperes, efficiency and harmonic performance as the ACRDCL inverter, hard-switched designs are compared. Methods to increase the power density of the ACRDCL are proposed, including the use of recently developed nonpunchthrough insulated gate bipolar transistors.

A source voltage-clamped resonant link inverter for a PMSM using a predictive current control technique

A simple source voltage-clamped resonant link (SVCRL) inverter is proposed to clamp the DC-link voltage to the input source voltage and reduce the current rating of a resonant inductor. The current control of a permanent magnet synchronous motor (PMSM) employing a predictive current control technique (PCCT) for the SVCRL, inverter is also investigated to overcome the disadvantage of the current-regulated delta modulation (CRDM) control technique. By employing the PCCT based on the discrete model of a PMSM and estimation of back electromotive force (EMF), the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique.

A simple soft-switched PWM inverter using source voltage clamped resonant circuit

A simple resonant link inverter is proposed to achieve pulsewidth modulation operation by using a single set of auxiliary resonant circuits which provides the soft-switching function to all main switches. With the proposed circuit, the clamped output link voltage, soft switching of all switches and reduced current stress on the resonant switch can be obtained.

A detailed study of losses in the reduced voltage resonant link inverter topology

A new reduced voltage resonant link (RVRL) topology was reported earlier. A detailed study of the effect of various parameters such as the characteristic impedance, Q factors, input DC voltage and the resonant frequency on the link losses is presented. The voltage and current stresses on various link components are also given. The losses are determined and then compared with those of the actively clamped resonant DC link. The RVRL topology reduces the link losses by 25% under certain operating conditions. The new topology being truly resonant offers less EMI and requires less number of power devices. It is particularly suitable at high resonant frequencies with ease of control.

Characterization and snubbing of a bidirectional MCT switch in a resonant AC link converter

The MOS-controlled thyristor (MCT) is emerging as a powerful switch that combines the characteristics of existing power devices. This paper presents a study of switching stresses on the MCT under zero voltage resonant switching. Two MCTs and two diodes are connected to form a bidirectional switch which was used in an AC/AC resonant link inverter. Current and voltage spikes are observed and analyzed with variations in the timing of the MCT switching. Different snubber circuit configurations are investigated to minimize the effect of these transients. Some failure modes of the device are also presented. >

Performance analysis of three-phase inverters controlled by synchronous delta-modulation systems

Synchronous delta-modulation systems are used to control resonant voltage link inverters, where switching has to be synchronized with the zero crossings of the link voltage. This paper shows that output current harmonic distortion and average switching frequency of such systems can be calculated analytically in spite of the quasistochastic behavior of the modulators output. Under the assumption of constant link frequency and large ratio of link to output frequency, results are derived for three-phase sigma-delta modulation, space-vector based sigma-delta modulation, and current-regulated delta modulation. The results hold for any shape of the inverter input voltage (including DC). The output current harmonic distortion of resonant link inverters is compared with conventional hard switching PWM inverters.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Spectral characteristics of resonant-link inverters

The limitations on the operating frequency of hard switched and resonant link inverters are studied. The maximum operating frequency of a hard switched inverter is found to be well defined by the allowed power dissipation due to on-state and switching losses. For resonant link inverters the upper limit is not as well defined and depends upon a trade-off between a number of different factors. For a system using high power bipolar transistors, it is seen that a resonant line system may achieve switching frequencies approximately ten times greater than those possible with a comparable hard switched inverter. The frequency spectrum of the resonant line configuration was compared with PWM (pulse width modulation). It was shown that the improvement in harmonic distortion associated with a delta modulated resonant link inverter is not as great as may be expected from the increase in link frequency that may be obtained. This is a result of constraints placed on switching instants and the need to use integral pulse modulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Review of resonant link topologies for inverters

Resonant link inverter configurations have been proposed as a means of obtaining significantly lower switching losses, thereby allowing operating frequencies and switch power ratings to be raised. In the paper, resonant link topologies are analysed by means of time-domain simulation, and the frequency spectrum typical of a resonant link inverter is compared with one typical of a hard-switched inverter. The resonant link system results in an increase in circuit complexity, and the frequency spectrum is limited by the need to employ integral pulse-modulation techniques.

A new resonant link aircraft power generating system

A 400 Hz aircraft power generating system which has been designed to achieve significant improvements in power density and reliability is introduced. Design targets for this exploratory development program include system (generator-plus-converter) power density of 1 kVA/lb and mean-time-between-failure (MTBF) of 500 h. At the heart of the new variable-speed constant-frequency (VSCF) configuration is a high-frequency resonant link inverter designed so that all inverter switching occurs under zero-voltage conditions. Advantages include minimization of switching losses and significant reductions in power device switching stresses and electromagnetic interference (EMI) generation. Inverter losses are further reduced by using MOS-controlled thyristors (MCTs) as the power switches in order to take advantage of their low forward voltage. A 60 kVA breadboard version of the system has been constructed, and test results which confirm its key performance characteristics are presented. >

Novel four quadrant DC-link soft switching inverter generating sinusoidal waveforms

A novel high frequency resonant link inverter using zerovoltage switching (except for one device where zero-current switching is used) operable in four quadrants is proposed. It provides several excellent advantages over the conventional resonant link inverters, such as low VA ratings, low acoustic noise and low harmonic distortion.

An induction motor drive using an improved high frequency resonant DC link invertor

An induction motor drive that uses an improved high-frequency resonant DC link inverter is presented. The resonant circuit was systematically analyzed first to establish the criteria for initial current selection, and a circuit to establish the bidirectional initial current was then proposed. The proposed current initialization scheme solves voltage overshoot and zero crossing failure problems in the ordinary resonant DC link inverters. A three-phase 3 kW insulated-gate-bipolar-transistor (IGBT) based 60 kHz resonant link inverter has been constructed and successfully tested with an induction motor drive. The speed control system is implemented using two microprocessors. Experimental results are presented to show superior operation of the proposed resonant DC link inverter drive.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Delta modulation strategies for resonant link inverters

The suitability of delta modulation strategies for resonant link inverters is explored in detail. The control and spectral characteristics of various delta modulators are examined in an effort to develop a model for the same. The more fundamental question of comparing delta modulation systems with conventional pulse-width-modulated (PWM) systems, given similar devices, is addressed, and it shown that the former provides a viable high-performance alternative. As the resonant DC link topology allows at least an order of magnitude increase in the switching frequency, Sigma Delta M systems using a given family of devices are capable of better spectral response than a conventional PWM inverter. >