Inverter Switching Control for Regenerative Overvoltage
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Solution Overview
Problem
Conventional power conversion devices face challenges in reliably inhibiting the rise in temperature of switching elements during regenerative control, particularly when a disconnection occurs between the DC power supply and the smoothing capacitor, leading to potential overvoltage and reduced reliability.
Innovation Solution
A power conversion device with a control circuit that alternates between switching on all upper switching elements and turning off all lower switching elements, and vice versa, every predetermined period, to manage regenerative current flow and temperature distribution across switching elements, thereby preventing overheating and voltage increase in the smoothing capacitor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only lower switching elements are turned on to cause regenerative current to flow back, then an increase in voltage of the smoothing capacitor is inhibited, but the temperature of the lower switching elements rises due to conduction loss
Solution Approach 1:
The control circuit performs periodic switching between two states: (1) turning on lower switching elements to consume regenerative power, and (2) turning on upper switching elements to allow current to flow back to the DC power supply. This periodic alternation prevents continuous conduction loss in a single set of switching elements, thereby controlling temperature rise while maintaining voltage stabilization
2Temperature
If arm switching control is performed to equalize temperatures between upper and lower arms, then temperature distribution is improved, but device complexity increases due to multiple temperature sensors and control logic
Solution Approach 1:
The invention extracts the temperature control function from complex multi-sensor feedback systems and implements it through simple periodic switching control. By alternating which arm consumes power, the system achieves temperature equalization without requiring multiple temperature sensors or complex real-time temperature measurement and adjustment logic
3Reliability
If all lower switching elements are turned on for three-phase short-circuit, then regenerative power is consumed and voltage increase is inhibited, but the lower switching elements experience excessive heat generation
Solution Approach 1:
Instead of continuously turning on all lower switching elements, the control circuit periodically alternates between turning on lower switching elements (to consume regenerative power) and turning on upper switching elements (to allow current flow back). This periodic action distributes heat generation across both upper and lower switching elements over time, preventing excessive temperature rise in any single component while maintaining the voltage stabilization function
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
This solution effectively inhibits the rise in temperature of switching elements, enhances the reliability of both the smoothing capacitor and switching elements, and extends their lifespan by ensuring efficient power consumption and cooling during regenerative control.
Implementation Method 1
the temperature of the lower switching elements rises, due to conduction loss at the time of switching
Data Source
AI summary
During regenerative control of an inverter circuit, when a path between a DC power supply and a smoothing capacitor is in a disconnection state, a control circuit of a power conversion device performs control while switching between first control in which upper switching elements within the inverter circuit are turned on and all lower switching elements are turned off and second control in which the lower switching elements are turned on and all the upper switching elements are turned off, every predetermined switching period.