Showing papers by "Hans Ertl published in 2018"

Performance of a Two-Stage Actively Damped LC Filter for GaN/SiC Motor Inverters

Abstract: In this paper, the filter performance of a wide-bandgap (WBG) three phase motor inverter with integrated sinusoidal output voltage LC filter is analyzed. To ensure a well damped system behaviour at low losses, an active damping scheme based on filter capacitor feedback is used. Unfortunately, the nonlinear DC-Bias dependent capacitance of the used ceramic capacitors (X7R is used to minimize filter volume) significantly affects the active damping. A symmetrical filter structure sufficiently reduces the capacitors voltage dependency. However, the paper shows that the symmetrical structure also causes negative effects in respective to the filters noise suppression performance. Modifications in the filter topology are reported and analyzed for reducing the impaired noise suppression. The proposed filter scheme finally results in a well damped system behaviour fulfilling established EMC standards according output noise demonstrated by experimental results of a 2 kW/400 V laboratory prototype.

Impacts of Filter-Nonlinearities and Voltage Limitations on a Wide-Bandgap Inverter with Actively Damped LC-Filter

Abstract: Today, motor inverters in the kW domain typically are implemented using silicon (Si) based insulated gate bipolar transistors (Si-IGBT) operating in pulse width modulation (PWM) mode at switching frequencies up to 20 kHz. During the past few years, however, wide-bandgap switching devices like GaNand SiC-MOSFETs have been significantly improved, especially concerning voltage capability of GaN devices. Due to the low switchingand also low onstate losses of GaN MOSFETs in comparison to Si-IGBTs, motor inverters with rather high switching frequencies but also high efficiency rates can be achieved (Shirabe and Swamy, 2012). However, the occurring high switching speed of the transistors with rise times in the range of 10 ns also create some crucial issues for motor applications caused by high du/dt rates.

Active Hybrid Filter Applied with a Multi-Cell Switch-Mode Power Amplifier

Abstract: This paper discusses an active filtering method applied on a multi-cell switch-mode power amplifier. One main purpose of this system is to build high quality power sources up to the kW-region. The system is formed by a switch-mode and a linear amplifier. The power allocation of the two parts is approximately 10:1 depending on the operation mode of the system. The switch-mode power amplifier is realized by a multicell amplifier with a passive LC-filter, which is actively damped by feeding back the capacitor current. The workload of the linear amplifier is influenced by the factors input frequency and load current which are examined in this paper. The benefit of the presented system is the low rated voltage and current of the linear stage. The performance of the whole system's output voltage is demonstrated by measurements in the time domain and by high resolution spectra.