Yalan Wang

An Analysis of High-Power IGBT Switching Under Cascade Active Voltage Control

A new gate-drive solution, cascade active voltage control (Cascade AVC), employs classic feedback-control methods with an inner loop controlling the insulated-gate bipolar-transistor (IGBT) gate voltage and an outer loop controlling the collector voltage, simultaneously. They make the switching performance less dependent on the IGBT itself. Feedback control of IGBTs in the active region does not necessarily slow the switching but introduces stability issues. A detailed stability analysis provides a sensible perspective to judge the system stability and justify the controller design, through considering major operating points and determining corresponding IGBT parameters. Experiments on high-power IGBTs including a 4500-V device show that Cascade AVC offers improved performance and is easier to design than the original AVC.

Numerical Optimization of an Active Voltage Controller for High-Power IGBT Converters

Feedback control of insulated gate bipolar transistors (IGBTs) in the active region can be used to regulate the device switching trajectory. This facilitates series connection of devices without the use of external snubber networks. Control must be achieved across the full active region of the IGBT and must balance a number of conflicting system goals including diode recovery. To date, the choice of control parameters has been a largely empirical process. This paper uses accurate device models and formalized optimization procedures to evaluate IGBT active voltage controllers. A detailed optimization for the control of IGBT turn-on is presented in this paper

Real-time Optimization of IGBT/Diode Cell Switching under Active Voltage Control

A combined digital and analogue approach is introduced to establish a dynamic active voltage controller (AVC) for controlling an insulated gate bipolar transistor (IGBT), suitable for series connection of devices. In the AVC, the reference voltage dictates the switching trajectory of active voltage controlled IGBTs via a feedback loop. By means of employing adaptive and self-timing control methods to adjust the reference voltage profile according to the transient states on the power side, this new controller has achieved real-time optimization of the IGBT switching with lowest possible power losses. In particular, this new AVC has provided an efficient and flexible solution to addressing the diode reverse recovery and the IGBT-diode commutation during IGBT switch-on operation. The commonly seen voltage overshoot and extra power loss associated with diode reverse recovery voltage are greatly reduced in the new AVC. The optimal switching performance in experiments for both a single IGBT and IGBTs connected in series is given in this paper. This is an effective solution to IGBT control without snubber networks and shows the effectiveness of concurrent optimization of devices and circuits

An analysis of high power IGBT switching under cascade active voltage control

A new gate drive solution, cascade active voltage control (cascade AVC), employs classic feedback control methods with an inner loop controlling the IGBT gate voltage and an outer loop controlling the collector voltage simultaneously. They make the switching performance less dependent on the IGBT itself. Feedback control of IGBTs in the active region does not necessarily slow the switching, but introduces stability issues. A detailed stability analysis provides a sensible perspective to judge the system stability and justify the controller design, through considering major operating points and determining corresponding IGBT parameters. Experiments on high power IGBTs including a 4500 V device show that cascade AVC offers improved performance and is easier to design than the original AVC.

Design of the active voltage controller for series IGBTs

This paper presents an investigation into the stability and performance of the active voltage control (AVC) method of gate drive applied to insulated gate bipolar transistors (IGBTs). The analysis is performed using standard control theory methods. Various parameters that affect the stability of the feedback system are investigated using root locus plots. It is shown that the bandwidths of various elements of the controller and the stray inductances in the gate-emitter circuitry are influential. This sets the design guidelines for improving the performance of the gate drives and for designing the compensating controller. Finally, experimental switching results from an IGBT switched with AVC using an optimised controller is given and conclusions drawn.

Controlled switching of high voltage IGBTs in series

This paper is focused on the investigation of performance and improvement of the switching control of high voltage IGBTs especially when connected in series. A variety of seriesing methods are explored and valuated. Due to the dominant advantages the Active Voltage Control (AVC) strategy is characterized, analyzed and optimised in simulation and experiments. A new method Active Voltage/Current Control (AV/CC) is advanced and validated for di/dt control. It is concluded that the AVC, particularly with the di/dt auxiliary loop control, allows the operation of high power IGBTs in series to be closely defined and well controlled.

Numerical Optimization of an Active Voltage Controller for Series IGBTs

Feedback control of IGBTs in the active region can be used to regulate the device switching trajectory. This facilitates series connection of devices without the use of external snubber networks. Control must be achieved across the full active region of the IGBT and must balance a number of conflicting system goals including diode recovery. To date, the choice of control parameters has been a largely empirical process. This paper uses accurate device models and formalised optimization procedures to evaluate IGBT active voltage controllers. A detailed optimization for the control of IGBT turn-on is presented in this paper

Parameters influencing the performance of an IGBT gate drive

This paper presents an improvement of an IGBT gate drive implementing Active Voltage Control (AVC), and investigates the impact of various parameters affecting its performance. The effects of the bandwidths of various elements and the gains of AVC are shown in simulation and experimentally. Also, the paper proposes connecting a small Active Snubber between the IGBT collector and its gate integrated within the AVC. The effect of this snubber on enhancing the stability of the gate drive is demonstrated. It will be shown that using a wide bandwidth operational amplifier and integrating the Active Snubber within the gate drive reduces the minimum gate resistor required to achieve stability of the controller. Consequently, the response time of the IGBT to control signals is significantly reduced, the switching losses then can be minimised and, hence, the performance of gate drive as whole is improved. This reflects positively on turn-off and turn-on transitions achieving voltage sharing between the IGBTs connected in series to construct a higher voltage switch, making series IGBTs a feasible practice.