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This paper presents an intelligent IGBT module for a quasi-resonant converter, widely used topology in induction heating (IH) applications. The proposed module is composed of an IGBT and the integrated gate drive circuit which provides dedicated protective and control functions to IH applications: soft start during load detection, long turn-on prevention, hard turn-on disabling, retention of minimum turn-off duration, and overvoltage protection for the IGBT. Conventional functions of under and over supply voltage protection, over temperature protection, temperature monitoring, and fault indication are implemented as well. Hence, the proposed module enables easy and compact design of the converter improving robustness and reliability. The design consideration and performance of the proposed functions are described in detail. The module is evaluated in the practical IH cooker to show its effectiveness.

This paper presents the effect of dithering on both harmonics and interharmonics in adjustable speed drives (ASDs). Using a voltage source configuration, a six-pulse rectifier and a sinusoidal pulse width modulated (SPWM) inverter are modeled in the PSCAD/EMTDC simulation platform. The pulse width modulated (PWM) signal for the inverter is modified by means of the additive dither noise. The dither randomizes the timing of rising and falling edges of PWM signals, which eventually reduces periodic harmonics of the inverter output voltage. The reduced harmonics also affect the source voltage of the rectifier and ultimately reduce interharmonics. The mitigated harmonics and interharmonics in the ASD are quantified in conventional power spectrum. Furthermore, frequency coupling is also analyzed using cross bicoherence to investigate causes of interharmonics.

In this paper, we utilize joint time-frequency analysis to inspect frequency-varying currents at the grid connection of a variable speed wind turbine system. Through simulation experiments based on a PSCAD dynamic model, frequency-varying characteristics of the currents are investigated and compared with the wind speed. Of particular note is the appearance of nonharmonic frequencies when the wind speed drops below a certain critical value, which is potentially harmful to the grid power quality. A comparison method based on joint time-frequency analysis is also provided to estimate the onset wind speed corresponding to the appearance of the extraneous frequencies.