R.W. De Doncker

The auxiliary quasi-resonant DC link inverter

A quasi-resonant DC link converter topology is proposed. The basic topology of the auxiliary quasi-resonant DC link (AQRDCL) is derived from the auxiliary resonant commutated pole (ARCP) converter and is closely related to the active clamped resonant DC link (ACRDCL) circuit. The operation and gating control strategy of the AQRDCL converter, which ensures zero voltage switching of all inverter switches and zero current switching of the auxiliary switches, is presented. The proposed circuit utilizes auxiliary switches to trigger the LC resonance of the DC link to create a zero voltage switching opportunity for the inverter switches. The waveform quality and the performance of the AQRDCL inverter, which has PWM capability, is compared with the DPM strategy of the ACRDCL inverter.<<ETX>>

Towards EMI prediction of a PM motor drive for automotive applications

Technology innovations in automobiles increasingly involve high power electric motor drives, leading to an increasing level of electromagnetic interference (EMI) and the requirements to meet electromagnetic compatibility (EMC). A numerical prediction of EMI/EMC has the potential to evaluate EMI performances at the design stage and before prototyping. It can also help reduce the post-prototype EMC cost by minimizing late re-design and modifications of a drive implementation. This paper describes a systematic approach towards early EMI prediction of motor drives. It is able to calculate the conducted EMI through modeling of parasitic coupling and circuit simulation. Methodologies for extracting parasitic parameters of major EMI components of a PM motor drive are developed using FEM analysis, experimental measurement and analytical approximation. Major EMI characteristics of the PM motor drive is then predicted by using a circuit simulator to solve the motor drive circuitry with high frequency parasitic parameters. Simulation results are compared with experimental data and the effectiveness of the EMI simulation approach is demonstrated.

A new hybrid filter to dampen resonances and compensate harmonic currents in industrial power systems with power factor correction equipment

A new hybrid power filter is presented for three phase industrial power systems which include passive power factor correction equipment (PFC). The hybrid filter damps resonances occurring between line impedances and the PFC. In addition, the hybrid filter topology cam be used to compensate harmonic currents. The capacitors of the PFC, which generally cause resonant problems in harmonic distorted networks, can be used for passive filtering by connecting the magnetizing inductance of a transformer in series. The primary side of the transformer is connected to a low VA-rated three-phase inverter which builds the active part of the hybrid topology. Simulation results and experimental results are presented verifying the damping and harmonic compensation performance of the proposed topology.

Single phase unity power factor control for dual active bridge converter

An AC line fed switching power supply with a single power converter stage is described which operates with high input power factor while maintaining good regulation of the desired output DC voltage. The single-power converter is a dual active bridge DC-to-DC power converter (DABC), comprising high-frequency transformer-coupled input and output bridge converters. The DABC receives a rectified AC line voltage via a diode-bridge rectifier connected to a small, high-frequency filter capacitor. The two active bridges, generating edge-resonant square waves at their transformer terminals, appropriately phase-shifted from each other to simultaneously perform the high-efficiency DC output regulation while maintaining unity power factor at the AC input. The soft-switching nature of the converter allows increased performance (in terms of efficiency and stresses) and reduction in size/weight at operating frequencies in the range of 50-250 kHz. Simulations, and experimental results are presented to corroborate the analysis.<<ETX>>

Characteristics of MOS-controlled thyristors under zero voltage soft-switching conditions

MOS-controlled thyristor (MCT) characterizations, as they relate to their dynamic performance during zero voltage switching, are reviewed. A test circuit that enables characterization of the zero voltage turn-on and turn-off losses of the device is described. Behavior models are presented and evaluated to predict the MCT turn-off losses under various soft-switching conditions. These models are shown to be useful for optimizing device performance in high frequency soft-switching converters.<<ETX>>

Control of three phase power supplies for ultra low THD

Current regulators are proposed and investigated for high-power three-phase power supplies with ultra-low total harmonic distortion (THD) (less than 0.5%). Two valid approaches to realize three-phase power supplies can be proposed. In the first approach, current regulated pulse-width-modulated (PWM) inverters along with high bandwidth voltage control loops are proposed. In the second approach, an internal voltage synthesizer under closed loop current control is used. Both approaches have mechanisms to decouple the LC filter interactions and to lower the THD. The tradeoffs of these two basic approaches are investigated. The influence of different current regulators in case of the current-regulated PWM (CRPWM) converter is investigated as well as different approaches to control the voltage synthesizer under current control. The study compares the effectiveness of these current regulator in soft-switching PWM inverters and describes a method to measure accurately ultra-low THDs.<<ETX>>

System design considerations for a high-power aerospace resonant link converter

A novel variable-speed, constant-frequency (VSCF) 400 Hz aircraft generating system has been developed using an actively clamped resonant DC link converter. The design approach used to select the best configuration for the resonant converter power stage is described, including techniques for choosing power component values to meet key governing performance specifications. Interactions between the various converter components are discussed, suggesting approaches for selecting values which must meet multiple and sometimes conflicting system performance criteria. Verification is provided using a combination of simulation results and test data from a 60 kVA laboratory breadboard system.<<ETX>>

Field-oriented controllers with rotor deep bar compensation circuits (induction machines)

A rotor deep bar effect compensation circuit for field-oriented controllers is derived from the transient equations of a double-cage induction machine. Torque and flux are decoupled with respect to the airgap flux. Accurate tuning of the field-oriented controller is possible both for steady-state and high-frequency conditions in the rotor. Consequently, an extended static stability region and improved torque dynamics are obtained with the deep bar effect compensated induction motor drive. >

A new single phase AC to DC zero voltage soft switching converter

A resonant boost rectifier is analyzed. The primary goal of the circuit is to produce single-phase AC line currents with very low harmonic distortion at unity power factor, thereby eliminating or reducing the size of filter components. The single-phase AC-to-DC converter consists of a boost-rectifier line conditioner connected to a resonant DC link bus. This enables zero-voltage soft switching operation of all the power devices, allowing the circuit to operate at high switching frequencies (up to 100 kHz) at high power levels (3 kW and above). The boost switch can be turned on or off at the zero voltage instants of the resonant DC link. As with resonant DC link converters, the amplitude of the AC input line current is modulated by discrete pulse modulation (DPM) of the resonant bus voltage. Furthermore, PWM (pulse width modulation) control at 100 kHz of the AC line currents can be obtained with little penalty on the system efficiency. This resonant boost rectifier is simple and reliable, achieves a high waveform quality, and operates very efficiently.<<ETX>>

Self tuning of induction motor servo drives using the universal field oriented controller

The universal field-oriented (UFO) controller is used to control the induction motor torque and airgap flux independently of each other. In this work, the direct UFO control is realized by sensing the airgap flux using center taps on two machine windings. Moreover, an adaptive control scheme that accomplishes a continuous and automatic tuning of the rotor time constant of the field-oriented controller whenever the drive operates in the direct field orientation mode is proposed. In addition, at low invertor frequencies, the UFO controller switches over to the indirect field orientation mode in which the rotor time constant is frozen to the last tuned value of the previous direct field orientation mode. At steady state and elevated speeds the induction motor servo drive has no detuning errors when operating under direct field orientation, while at low speeds the indirect field orientation mode exhibits minimal errors. The latter expands the use of the high-performance induction motor drive up to standstill. The proposed field-oriented controller can be realized at minimal cost in AC servomotor drives requiring motion control or accurate speed control.<<ETX>>