Voltage Source Converter Adaptive Gate Drive
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Solution Overview
Problem
Voltage source converters face challenges in managing turn-on losses in IGBTs, particularly at higher currents, leading to increased costs and reduced lifetime due to thermic cycling, and existing solutions complicate control schemes with additional communication links and sensors.
Innovation Solution
The solution involves measuring the voltage across the rectifying diode before switching to estimate load current, using this measurement to control the turn-on of the semiconductor device, and adapting the turn-on speed based on current levels to maintain desired diode reverse recovery dV/dt, simplifying control and reducing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the IGBT is turned on quickly at higher currents, then switching losses are reduced, but diode reverse recovery dV/dt increases beyond acceptable levels
Solution Approach 1:
The gate drive characteristics are made dynamically adjustable based on operating conditions. The control unit varies the turn-on gate drive strength according to the measured load current, enabling fast turn-on at high currents while providing soft turn-on at low currents where diode reverse recovery is more problematic.
Solution Approach 2:
The invention changes the gate drive parameters (voltage, current, or resistance) as a function of the load current. By measuring the voltage across the rectifying diode to estimate load current, the system adapts the IGBT turn-on characteristics to match the actual operating conditions, optimizing both switching losses and diode reverse recovery behavior.
2Loss of energy
If additional current sensors and communication links are added to control turn-on speed, then switching losses are reduced, but device complexity increases
Solution Approach 1:
The system uses the voltage measurement across the rectifying diode, which is already part of the normal converter operation and control scheme. This existing measurement is repurposed to estimate load current and control the IGBT turn-on characteristics, eliminating the need for separate current sensors and additional communication infrastructure.
Solution Approach 2:
The voltage measurement across the rectifying diode serves multiple functions: it is used for normal converter control and simultaneously provides the load current information needed for adaptive IGBT turn-on control. This multi-functional use of existing measurements simplifies the overall system architecture.
Data Source
Figure 1~2
Figure 3~5
AI summary
A voltage source converter has a half bridge (21) with two current valves (22, 23) connected in series. A gate drive unit (32) has gate drive parts (33, 34) for control of a semiconductor device (26, 27) of the respective current valve. The converter has for each current valve a member (41, 42) measuring the voltage across a rectifying diode (28, 29) of the current valve and sending information about this voltage measured to a control unit (36, 35) of the gate drive part (34, 33) controlling the other valve. These control units are configured to use the voltage measured as a measure of the current on an AC side (30) of the converter and make the control of a gate member (40, 39) of the respective semiconductor device depending upon information about this voltage so as to minimize the total switching losses associated with the turn on of the semiconductor device while still keeping the diode reverse recovery dV/dt of the freewheeling diode of the half bridge below a maximum level allowed.