Dominic Gerber

Gate Unit With Improved Short-Circuit Detection and Turn-Off Capability for 4.5-kV Press-Pack IGBTs Operated at 4-kA Pulse Current

This paper presents a gate unit with short-circuit protection for a 4.5-kV press-pack insulated gate bipolar transistor (IGBT) designed for pulsed applications and operated at a pulse current of 4 kA and the results of short-circuit tests performed with the mentioned switch and the gate unit. Initially, an overview of the gate unit, the implemented gate boosting as well as the two-stage turn-off and active clamping is given. An over- di/dt as well as an over-current detection using a printed circuit board (PCB) Rogowski coil is used in the gate drive to protect the IGBT during operation. Then, the design of the PCB Rogowski coil is introduced including partial element equivalent circuit simulations to predict the coil parameters. Measurements were made to verify these simulations. Afterward, two types of short-circuit tests were performed. First, the over- di/dt detection was tested by turn-on into a short circuit. The tests show that the over- di/dt detection reacts very fast. The IGBT was always able to turn off the short-circuit current. The maximum short-circuit current was 4.4 kA. Second, tests using an auxiliary switch were made to investigate the short-circuit events during pulse top. The IGBT was able to turn off a maximum short-circuit current of 8.7 kA.

IGBT gate-drive with PCB Rogowski coil for improved short circuit detection and current turn-off capability

In this paper, a gate drive using gate boosting and double-stage turn off including voltage clamping as well as with detection of overcurrent and a too high di/dt during turn on is discussed in detail. Besides the gate drive, also the design of a PCB-Rogowski coil, which is used for measuring currents and for di/dt detection, is explained and different designs are compared. The presented coil has a bandwidth of more than 28MHz and a propagation delay of 11 ns.

Interleaving of a Soft-Switching Boost Converter Operated in Boundary Conduction Mode

This paper presents the interleaved operation of a soft-switching boost converter operated in boundary conduction mode. First, the operating principle of the converter as well as the basic concept of the interleaving is presented. Then, the dynamic behavior is modeled using the z-transform to obtain a converter model that is independent of the switching frequency. With the model, the stability of the closed-loop system with a proportional-integral (PI) controller is analyzed. It is shown that an adaptive PI controller can be easily implemented to achieve a minimal settling time over a wide operating range. Finally, the controller is validated with two converters with a 40-kW nominal output power and an output voltage of 3 kV. The tests at different output voltages under different load conditions show a stable interleaved operation.

Charging Precision Analysis of a 40-kW 3-kV Soft-Switching Boost Converter for Ultraprecise Capacitor Charging

In this paper, the charging precision of a 40-kW 3-kV soft-switching boost converter for capacitor charging is investigated. At the beginning, an overview on the topology and the control of the converter is given. Then, two different feedback controllers are presented and compared analytically to determine their sensitivity on noisy input variables. An algorithm to investigate the charging precision is illustrated. This algorithm considers the signal-to-noise ratio (SNR) of all measured signals, the controller output limitations, quantization related errors, the finite resolution in the digital domain, and the switching signal jitter to calculate the charging precision. All effects mentioned before are analyzed separately. This analysis shows that the output voltage measurement SNR is the key parameter for the charging precision. Then, measurements are performed to verify the model used to calculate the precision. These measurements show that the measured precision is only 6% higher than the precision predicted by the model for the used setup. Finally, the charging precision of the presented converter is analyzed including all considered effects. The repetition accuracy of the converter is determined to be 8.3 ppm at an output voltage of 3 kV, neglecting the load connection and the input voltage variation during one switching cycle.

Bouncer circuit for a 120 MW/370 kV solid state modulator

In this paper, a bouncer circuit for a 120 MW/370 kV modulator is described. The bouncer circuit is a two-winding inductor bouncer which reduces the output voltage droop. The bouncer circuit is described and investigated in detail. Also, the influence of component tolerances is investigated. Finally, the benefit of using a bouncer circuit is shown by presenting the same modulator without and with bouncer circuit. The amount of stored energy was reduced by a factor of 3.3 which reduces the overall system volume significantly.

High-Dynamic and High-Precise Optical Current Measurement System Based on the Faraday Effect

In this paper, a high-dynamic and high-precise optical current measurement system based on the Faraday effect is presented. First, the sensor concept is presented and different sensor constructions are analyzed. Then, a measurement system based on a rare-earth iron garnet film is investigated. The measurement system uses multiple signal processing channels to increase the signal-to-noise ratio. Furthermore, the measurement range exceeds a rotation of 180° and therefore requires a counting mechanism to count the number of rotations. Finally, the precision of the presented system is analyzed. The precision is determined to be 4.9 ppm at a rotation range of 3300°.

Charging precision analysis of a 40 kW, 3 kV soft-switching boost converter for ultra precise capacitor charging

In this paper, the charging precision of a 40 kW, 3 kV soft-switching boost converter for capacitor charging is investigated. At the beginning, an overview on the topology and the control of the converter is given. Then, two different feedback controllers are presented and compared analytically in order to determine their sensitivity on noisy input variables. An algorithm to investigate the charging precision is illustrated. This algorithm considers the signal to noise ratio of all measured signals, the controller output limitations, quantization related errors, the finite resolution in the digital domain and the switching signal jitter in order to calculate the charging precision. All effects mentioned before are analyzed separately. This analysis shows, that the output voltage measurement signal to noise ratio is the key parameter for the charging precision. Finally, the charging precision of the presented converter is analyzed including all considered effects. The repetition accuracy of the converter is determined to be 8.3 ppm at an output voltage of 3 kW, neglecting the load connection and the input voltage variation during one switching cycle.

High precision, low ripple 3kV capacitor charger

In this paper, a high precision, low ripple 3kV capacitor charging system is investigated, which is designed for the Compact Linear Collider (CLIC). The 240 kW charging system consists of six capacitor charging units operated in boundary conduction mode (BCM). In order to obtain a low current ripple, the charging currents of the units are interleaved. Measurements of the interleaved capacitor charging are provided, which show the stable operation of the interleaving controller. To achieve a high pulse to pulse repeatability of the pulse modulator system, a high charging accuracy of the capacitor bank is mandatory. Thus, a precision analysis of the capacitor charging system is also performed in this paper. With this analysis, the standard deviation of the capacitor banks voltage is derived for the entire CLIC load operating range, resulting in σvout <23.2 mV, which is below 10 ppm.

Design of an Ultraprecise 127-MW/3- Solid-State Modulator With Split-Core Transformer

This paper presents the design of an ultraprecise 127-MW/3-μs solid-state modulator with split-core transformer. The modulator consists of a power supply, 12 pulse generator modules with active core reset, and a split-core transformer with six cores. In addition, an LC bouncer could be used to compensate the droop of the pulse. This paper includes the design and analysis of the pulse transformer. A volume minimal transformer is investigated for different load capacitances to investigate the achievable rise time and the parameters which can be used to adjust the damping. In addition, the influence of the pulse transformer on the synchronization of the switches is investigated using an enhanced reluctance model. In addition, an LC bouncer circuit is investigated. A multiobjective optimization is performed which shows the required energy of the bouncer for a certain pulse ripple. The flat-top ripple of the presented modulator can be reduced to 0.2%. Because the bouncer degrades the flat-top stability, the bouncer is not implemented. Measurements of the overall system include short-circuit measurements and flat-top stability measurements. They show that the modulator is shortcircuit capable. Furthermore, the flat-top stability is determined to be less than 10 ppm at an output voltage of 360 kV.

High precision optical current measurement system based on the faraday-effect with a large bandwidth

In this paper, a high dynamic, high precision optical current measurement system based on the Faraday-effect is presented. First, the sensor concept is explained and different sensor constructions are analyzed. Then, an implementation of the concept based on a rare-earth iron garnet film is investigated. This measurement system uses multiple signal processing channels to increase the signal-to-noise ratio. Furthermore, the range of the rotation of the polarization plane exceeds 90 ° and therefore requires a counting mechanism to count the number of rotations. Finally, the precision of the presented system is analyzed. The precision is determined to be 4.9 ppm for a rotation range of 3300°.