Resonant DC Link Research Articles

Utilization of the series resonant DC link converter as a conditioning system for SMES

A superconductive magnetic energy storage (SMES) system utilizing a high-frequency series resonant DC link power converter of high efficiency as the conditioning converter is presented. This system generates a high-frequency (20 kHz or more) resonant current in a series link and switching is done at zero-current instants, reducing switching losses to a minimal value. Through the utilization of an adequate control strategy, the input power factor can be fully adjusted during the charging, storing, and discharging modes of the SMES, improving the overall system efficiency. Different semiconductor devices are used as the switching losses are established for each case. Experimental results from a monophase and three-phase system verified the results obtained from digital simulation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Series Resonant DC Link Converter for Induction Motor Drives.

Series Resonant DC Link Converter for Induction Motor Drives.

An Evaluation Method of Power Loss in Resonant DC Link Inverters.

Resonant DC link inverters, which can realize high switching frequency power conversion without switching loss in principle, have been proposed and investigated. In such inverters, power loss is produced in the resonant circuit though power loss in the main circuit is reduced by the amount of the switching loss Therefore, an evaluation method of the total power loss should be established from the view point of efficiency.In this paper, first we summarize the circuit operation and the control method of the resonant DC link inverter. Based on this, the expressions for various power losses produced both in the inverter main circuit and in the resonant circuit are derived. In this derivation, since the turn-on signal for an inverter arm is assumed to be determined only by comparison of the actual output current and its reference, a concept of probability is introduced for the turn-on signal of each inverter arm.As an investigation of the resonant reactor, which affects the total power loss significantly, two types of reactor are constructed and the frequency characteristics of their resistances are clarified experimentally.To confirm the validity of the expressions for losses derived in this paper, a comparison of the calculated and measured total losses is made for an experimental system.

Analysis and improved control method of resonant DC link inverters

High performance power conversion requires high switching frequency power converters. Resonant dc link inverters, which are investigated in this paper, are suitable for this purpose because they cause no switching loss in principle. But in these inverters, loss of the resonant oscillation and occurrence of high peaks in the resonant capacitor voltage are serious problems. In this paper, we investigate a control method for resonant dc link inverters which can overcome these problems. First of all, we summarize the basic control principle of an ideal resonant dc link inverter. Then we present an analyzing method for the practical resonant dc link inverter introducing two equivalent circuits in which the influence of the power losses in the resonant link and in the inverter load is considered. From these equivalent circuits, the problems of existing control methods are clarified. Based on the results of this analysis, we propose an optimum and keep the capacitor voltage at an allowable level. A simple compensation method for the influence of storage time of switching devices, which affects the implementation of the proposed control method, is described. Some experimental results are included to confirm the validity of the analytical results and the effectiveness of the proposed control method.

Parallel resonant DC link circuit-a novel zero switching loss topology with minimum voltage stresses

A parallel-resonant DC link (PRDCL) circuit topology is presented as a way to realizing zero-switching-loss, DC-AC high switching frequency power conversion. The circuit is used as an interface between DC voltage supply and the voltage-source PWM (pulse-width-modulated) inverter. It provides a short zero-voltage period in the DC link of the inverter to allow zero-voltage switching to take place in the PWM inverter. The peak voltage stress on the PWM inverter switches is limited to the DC supply voltage. Another significant advantage of the proposed circuit is that the inverter can be controlled by the conventional PWM strategy. The circuit is systematically analyzed, and its operation principle is explained in detail. Design considerations and formulae are also presented. A complete zero-voltage-switching DC-AC converter system consisting of the proposed circuit and the PWM inverter is simulated on computer. >

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>

Analysis and Improved Control Method of Resonant DC Link Inverters.

High performance power conversion requires high switching frequency power converters. Resonant dc link inverters, which are investigated in this paper, are suitable for this purpose because they cause no switching loss in principle. But in these inverters, loss of the resonant oscillation and occurrence of high peaks in the resonant capacitor voltage are serious problems. In this paper, we investigate a control method for resonant dc link inverters which can overcome these problems. First of all, we summarize the basic control principle of an ideal resonant dc link inverter. Then we present an analyzing method for the practical resonant dc link inverter introducing two equivalent circuits in which the influence of the power losses in the resonant link and in the inverter load is considered. From these equivalent circuits, the problems of existing control methods are clarified. Based on the results of this analysis, we propose an optimum and keep the capacitor voltage at an allowable level. A simple compensation method for the influence of storage time of switching devices, which affects the implementation of the proposed control method, is described. Some experimental results are included to confirm the validity of the analytical results and the effectiveness of the proposed control method.

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. >

Dynamic analysis and experimental evaluation of delta modulators for field-oriented AC machine current regulators

Implementation of field-oriented control requires regulation of the temporal orientation of flux and current vectors in AC machines. The orientation is generally achieved via instantaneous control of stator current relative to either the measured flux or the indirectly estimated flux terms. In either case, the instantaneous control of current is critical. A novel approach for current regulation is presented, based on the use of a nonlinear discrete-time delta modulator which offers the potential for reduced parameter sensitivity and more accurate command tracking than either classical or state-space linear system controllers. A power electronic topology, the resonant DC link is ideally suited to implement this controller. Experimental data on a field-oriented induction machine controller using a resonant DC link inverter topology demonstrate the command tracking performance of this induction-machine current regulator. >

The resonant DC link converter-a new concept in static power conversion

A novel approach to realizing efficient high-performance power converters is presented. The concept of a resonant DC link inverter has been proposed and realized with the addition of only one small inductor and capacitor to a conventional voltage source inverter circuit. The proposed technology is capable of switching almost an order of magnitude faster than state-of-the-art voltage source inverters at significantly improved efficiencies using the same family of devices. The topology is especially suitable for high-power applications using gate turn-off devices. A 4.5 kW inverter has been fabricated and tested extensively in the laboratory, and the superior characteristics of the resonant DC link topology have been verified. >

Zero-switching-loss inverters for high-power applications

The development of zero switching loss inverters has attracted much interest for industrial applications. Two topologies for realizing zero switching losses in high-power converters are proposed. The actively clamped resonant DC link inverter uses the concept of a lossless active clamp to restrict voltage stresses to only 1.3-1.5 supply voltage. For applications demanding substantially better spectral performance, the resonant pole inverter (RPI), also called the quasi-resonant current mode inverter, is proposed as a viable topology. Using only six devices rated at supply voltage, this circuit transfers the resonant components to the AC side of each phase and thus requires additional inductor and capacitor (LC) components. On the other hand, the RPI is capable of true pulsewidth modulation (PWM) operation at high frequency as opposed to discrete pulse modulation operation found in resonant DC link invertors. >

An evaluation of resonant snubbers applied to GTO converters

Aspects of the application of resonant snubber technology to gate-turn-off (GTO) converters are investigated. GTO power switches require snubbing at turn-off when applied in converters. This leads to the extensive use of regenerative snubber circuits in GTO converters due to the difficulties involved in using dissipative snubbers. At present, it is accepted that the repetition switching frequency of GTO pulse-width modulated (PWM) circuits is largely determined by the resettling time of regenerative snubbers. The resonant DC link may be seen as a nondissipative snubber and holds the promise of a faster resettling time. The behavior of GTO devices is investigated under the conditions applied to them by this kind of snubbing and its application in GTO converters. The concept has been demonstrated with 90 A 1200 V GTOs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>