Current-controlled Inverter Research Articles

Symmetric structure of induction motor systems

In this paper, symmetric structure of induction motor system in stationary αβ0 coordinates is studied by the geometric approach. The results show that the system possesses symmetry (G, ϑ,Φ) and infinitesimal symmetry. Under certain conditions, the system can be transformed into a form possessing state-space symmetry (G, Φ) and infinitesimal state-space symmetry by means of state feedback and input coordinate base transform. The results can be extended to the fifth order induction motor system fed by hysteresis-band current-controlled PWM inverter.

A control method for the active power filter in unsymmetrical voltage systems

In this paper, the authors propose a calculation method for the compensating current reference of the active power filter, where a nonlinear load exists in a three-phase, three-wire unsymmetrical voltage system. This new method has been named the extension pq method. The authors have experimented with the extension pq method and the pq method, using the same current-controlled intelligent power module inverter for both methods. The results of the experiments proved that in the unsymmetrical voltage system the source current was distorted in the case of the pq method, but undistorted in the case of the extension pq method.

Integrating the digital time control algorithm with DC-bus ‘notching’ circuit based soft-switched inverter

A single-phase full-bridge bi-level inverter using a DC-link quasi-resonant circuit (QRC) to introduce a zero-volts interval across the DC bus for soft switching is discussed. It is demonstrated that the digital time control (DTC) algorithm, a method that belongs to the family of zero average current error (ZACE) methods, is a suitable technique to be integrated with a typical QRC DC-link soft-switched inverter. Experimental results taken from a low power single-phase current-controlled inverter prototype are documented. These include quasi-resonant circuit waveforms, inverter waveforms and electromagnetic interference (EMI) spectral characteristics.

Comparison between space vector modulation and subharmonic methods for current harmonics of DSP-based permanent-magnet AC servo motor drive system

The PWM voltage generated by the space vector modulation method is compared with that generated by the subharmonic method for a permanent-magnet AC servo motor driven by a current-controlled PWM inverter. For the space vector modulation method, the on-times of its two zero voltage vectors are equalised. The experimental waveforms of phase currents, which were produced by the subharmonic and space vector modulation methods, are represented. In addition, the calculated waveforms of the phase currents and torque are shown for both methods. FFT results are indicated for the calculated current waveforms, which show that the current harmonies in the space vector modulation method are reduced by 45% around the carrier frequency relative to its value from the subharmonic method. Furthermore, the relation between the on-time ratio of two zero-voltage vectors and total harmonic distortion is investigated for the calculated current waveforms obtained by the space vector modulation method.

Improved and less load dependent three-phase current-controlled inverter with hysteretic current controllers

A concept of the so-called inner feedback in three-phase current-controlled inverters with hysteretic current controllers is introduced. Stability of the inverter at various frequencies under two different applied loads have been studied. An inertial feedback loop is added to each controller. This modification affects operating characteristics of the inverter by enforcing a switching pattern of low dependence on the load, resulting in significantly improved quality of the output current. >

Analysis of Switching and Conduction Losses in Hysteresis Current-Controlled Inverters.

Analysis of Switching and Conduction Losses in Hysteresis Current-Controlled Inverters.

Flux tracking in induction machines by means of volt-ampere quantities

It is demonstrated that an instantaneous quantity related to average reactive power can be defined for machines with three-phase sinusoidally distributed windings. Expressions for the flow of this quantity into the stator of an induction machine are obtained and interpreted in terms of the behavior of flux distributions within the machine. These results are used to devise an algorithm for tracking the rotor flux inside an induction machine without dependence on stator or rotor resistance and without the need for motor modifications. Application of this algorithm to a field-oriented control system utilizing a voltage-source current-controlled inverter is investigated. Computer simulations are presented to support the theoretical results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Operating Limits of Inverter-Driven Permanent Magnet Motor Drives

Recent developments of high-energy permanent magnet (PM) materials such as neodymium-iron-boron have focused attention on the use of PM synchronous motors supplied from inverters for a wide variety of speed control applications. PM motor drives are readily applicable where full torque is required up to full or base speed. They are, however, limited in their ability to operate in the power-limited regime where the available torque is reduced as the speed is increased above its base value. In contrast with the field weakening approach used in dc drives, the magnet is permanent. The torque-speed operating limits of PM motor drives, of conventional design are explored, and then design measures which can substantially extend operation into the power-limited regime are proposed. A trade-off between the low speed-torque limit and the extent of the speed range above base speed is achieved by variations in magnet dimensions and the depth of inset of the magnets in the rotor iron. Experimental results are presented for two motors of different design, each using neodymium magnets and each supplied from a current-controlled inverter with hysteresis control of current waveshape.

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.

高調波抑制と高速電流応答を可能にした電流制御形ＰＷＭインバータ

高調波抑制と高速電流応答を可能にした電流制御形ＰＷＭインバータ

Identification and Compensation of the Rotor Temperature of AC Drives by an Observer

The magnetic flux of induction motors fed by current-source or current-controlled voltage-source inverters is normally controlled indirectly and considerably influenced by rotor temperature. Since the additional installation of temperature sensors does not agree with the intention of a sturdy drive, indirect detection using only easily measurable quantities is desired. On-line observation of the machine by a model implemented in a microcomputer allows closed-loop estimation of the disturbing temperature. Requirements on the accuracy of the model and the measured data are discussed. The feedback from the estimation program to the analog inverter control including experimental results is demonstrated.

Design, analysis and test results for a superconducting linear synchronous motor

A linear synchronous motor has been designed to propel a 480 km/h magnetically levitated passenger vehicle. The paper describes the motor and presents the results of tests which have been performed on essentially full-scale components of the motor using a 7.6 m-diameter test-wheel facility. Controlled starting, acceleration, cruising, deceleration and transient operation have been demonstrated. A 6-component force balance has been used to measure the three forces and three moments acting on a single stationary superconducting magnet due to its interaction with the split 3-phase windings mounted on the rim of the test wheel and energised by a variabl-efrequency current-controlled inverter power supply. Measured forces and terminal characteristics over complete cycles of force angle are in excellent agreement with analysis based on a coupled circuit model of the machine and mutual inductance computations. Moments were measured to be small underall operating conditions. Two modes of control have been demonstrated. The α-scheme, proposed for a full-scale system, maintains the angle between induced voltage and phase current at a value which optimises the motor characteristics, i.e. inverter MVA rating, etc. β-control, which may be required for starting, uses vehicle position detectors to fire the inverter thyristors at appropriate times.