Power Converter Start-Up Heating via Controlled Short-Circuit Losses
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Solution Overview
Problem
Power converters experience increased failure rates and electromagnetic disturbances when started at low ambient temperatures due to impaired semiconductor switch performance, requiring special design measures or external heating methods to raise junction temperatures.
Innovation Solution
A method involving controlled short circuit states in the power converter to generate heat through increased conduction and switching losses in semiconductor switches, using modified gate voltages to increase heating without external heating devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external heating devices or special design measures are used to raise junction temperatures, then reliability during start-up improves, but device complexity and cost increase
Solution Approach 1:
The power converter system uses its own internal power losses (conduction losses and switching losses) to generate heat and raise the junction temperature of semiconductor switches during start-up. The control unit enables a short-circuit state that intentionally increases power loss to provide the necessary heating, allowing the system to heat itself without external heating devices or special design measures.
Solution Approach 2:
The invention converts the harmful effect of power losses (which normally represent wasted energy and heat that needs to be dissipated) into a beneficial effect by using these losses to heat the semiconductor switches during start-up. The short-circuit state intentionally increases power loss to raise junction temperature, transforming what is typically a detrimental factor into a useful heating mechanism.
2Productivity
If normal switching operation is started at low temperatures, then productivity is maintained, but failure rate increases due to impaired semiconductor switch performance
Solution Approach 1:
The control unit performs a preliminary heating action by enabling a short-circuit state before normal switching operation begins. This short-circuit state increases power losses to raise the junction temperature of semiconductor switches to an acceptable level, ensuring that when normal operation starts, the components are at the required temperature to avoid increased failure rates.
3Temperature
If gate voltage is reduced to increase conduction losses for heating, then temperature rises to improve reliability, but power loss increases
Solution Approach 1:
The control unit applies modified gate voltages periodically or temporarily during the start-up phase to increase conduction losses and generate heat. The modified gate voltage is applied only during the short-circuit heating state, not during normal operation, allowing the system to benefit from reduced power loss during normal operation while achieving necessary heating during start-up.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively raises semiconductor and component temperatures above a minimum threshold, reducing failure rates and electromagnetic disturbances, enhancing reliability and efficiency during start-up.
Implementation Method 1
enabling a short circuit state of the first converter by controlling semiconductor switches of the first converter to create at least one short circuit path through the first converter that carries the supplied current; wherein at least one of the semiconductor switches in at least one of the short circuit paths is operated with modified on-state conduction in order to increase conduction losses
Implementation Method 2
A method involving controlled short circuit states in the power converter to generate heat through increased conduction and switching losses in semiconductor switches, using modified gate voltages to increase heating without external heating devices
Data Source
AI summary
A power converter system is provided and includes a power converter having a first converter that includes at least a controllable semiconductor switch having a threshold voltage and a gate voltage for normal on-state conduction, DC terminals connected to a DC link, and AC terminals, a controller of the system supplies current to the first converter for short circuiting by controlling the switches to create a short circuit path through the converter that carries the current. At least one switch in a short circuit path is operated with modified on-state conduction to increase conduction losses by applying a modified gate voltage less than the gate voltage for normal on-state conduction, the modified gate voltage equals the threshold voltage plus x volts, where x ranges from 100 mV to 4 V, and when the converter is short-circuited, the DC link voltage is less than that during a normal switching operation.