Inverter Stop Control for Regenerative DC Link Overvoltage
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Solution Overview
Problem
Inverters using a single capacitor with small capacity face durability issues due to excessive regenerative voltage when the PWM control signal is cut off, as they lack sufficient capacity to accommodate the remaining power.
Innovation Solution
A controller is used to detect a stop signal for the PWM control and reduce the load speed, stopping the driving of the load at a specific phase when the link voltage is minimum, and optionally controlling a PFC circuit to minimize regenerative voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single capacitor with small capacity is used in the DC linker, then the device complexity and component count are reduced, but the reliability deteriorates due to excessive regenerative voltage causing durability issues
Solution Approach 1:
The controller detects the stop signal for PWM control in advance and proactively reduces the load speed before the capacitor experiences excessive regenerative voltage. This preliminary action prevents the harmful voltage buildup from occurring in the first place, thereby protecting the capacitor while maintaining the simple single-capacitor DC linker structure
Solution Approach 2:
The controller continuously monitors the operation state of the inverter and detects the stop signal for PWM control. Based on this feedback information, the controller adjusts the load speed to prevent excessive regenerative voltage from occurring in the capacitor, thereby maintaining capacitor durability without requiring multiple capacitors or a more complex DC linker structure
2Speed
If the PWM control signal is cut off abruptly, then the response time is reduced, but the harmful factors increase due to regenerative voltage exceeding capacitor capacity
Solution Approach 1:
When the controller detects a stop signal for PWM control, it proactively reduces the load speed before the PWM signal is completely cut off. This preliminary action ensures that regenerative voltage does not exceed capacitor capacity, preventing harmful effects while maintaining fast response capability
Solution Approach 2:
The controller applies a counter-action by reducing load speed in advance when PWM stop is detected. This preliminary anti-action counteracts the potential harmful regenerative voltage buildup before it can occur, allowing abrupt PWM termination without causing capacitor damage
Data Source
AI summary
An electronic device comprises: a rectifying unit to rectify an input alternating current voltage; a converter to convert the rectified input alternating-current voltage into a direct-current voltage; an inverter including a plurality of switching elements to convert the direct-current voltage into a three-phase alternating current voltage and outputting the three-phase alternating current voltage to a load; a DC link unit located between the converter and the inverter; and a control unit to control the inverter to convert the direct-current voltage into the three-phase alternating-current voltage according to a pulse width modulation (PWM) control signal. The control unit reduces the speed of a load in response to the detecting of a stop signal with respect to the PWM control signal and controls the load to stop a driving of the load in response to the detecting of a change in the link voltage of the DC link unit.