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This paper presents an improved PWM strategy for three-phase inverters, especially suited for use at low ratios of switching frequency to fundamental output frequency. The method of third-harmonic injection is used to ensure maximum utilisation of the DC bus voltage. Implementation issues for the new modulation strategy are discussed. A comparison with a conventional, regularly sampled PWM is presented,...
This paper reports on inverter nonlinearity effects on sensorless control methods based on high-frequency signal injection (HF-injection). Inverter output voltage distortions and their influence on position detection are described analytically and their compensation is discussed. Furthermore it is pointed out that the effects of inverter nonlinearities on sensorless control depend on whether the rotating...
This paper deals with a method to derive the junction temperature of an IGBT while the device is in operation. In order to achieve this the gate-emitter voltage, the collector current and the collector-emitter voltage are digitized on the driver board. Due to the fact that material parameters vary with temperature, the waveforms of the switching transients vary with temperature, too. Thus, there is...
Synchronous optimal pulse width modulation (SO- PWM) techniques provide an appropriate solution to the increasing demand on very low switching frequencies of power semiconductors, in order to reduce switching losses. The shape of their pulse patterns is offline computed, and the modulation techniques assume a steady state operation of the drive system. Medium voltage drives when applied to the retrofit...
This document describes a new approach to generate binary signals with varying pulse-lengths for the use in power electronics. The novel modulation scheme SB-ZePoC (Zero Position Coding with Separated Baseband) was primarily developed for Class-D audio amplifiers. This modulation scheme has the extraordinary advantage that the signal band is free of harmonic distortion and carrier intermodulation...
Gate units of todaypsilas converters are in most cases voltage sources charging the input capacitance with a fixed gate resistor. Consequently, there is hardly no possibility to adapt quickly the gate unit to different semiconductor devices. During operation, there is no adaption process to adjust the switching transients to their actual optimum. The possibilities to implement new features or to adapt...
This paper reports on a novel modulation strategy for generation of band limited signals with binary switches, which was originally developed for audio power amplifiers, and on applying it to energy conversion. This modulation strategy has the extraordinary advantage that the signal band is free of harmonics or carrier intermodulation products. This so called ldquoZero-Position-Coding with Separated...
In high power medium voltage drives the switching frequency of power semiconductor devices is limited because of high switching losses. These drives often consist of a three-level NPC inverter with an LC output filter to protect the motor from harmonics. Application of the filter creates a resonant circuit that may be excited for instance by switching harmonics or control transients. However, state...
In order to reduce the switching frequencies of power semiconductors, synchronous optimal pulse width modulation provides an appropriate solution. The switching angles result from complex offline calculations, assuming steady-state operation. Medium voltage drives when applied to the retrofit of existing fixed speed induction motors often include an output LC-filter which introduces a resonant circuit...
Gate units of todaypsilas converters are in most cases voltage sources charging the input capacitance with a fixed gate resistor. In some publications, fixed current sources are implemented to support the charging process with a supplementary gate current. These solutions are implemented in an analog way and are designed and respectively optimized for fixed parameters and devices. During operation,...
This paper presents a first order ΣΔ Analog to Digital Converter for current measurement in motor controls. The converter consists of a time continuous differential integrator at the input with external capacitors and a four bit pulsewidth modulator in the feedback branch. Highly symmetrically switching inverters are used to couple the differential feedback signal back to the input of the converter...
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