Adaptive Inverter Switching Frequency for Thermal Control
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Solution Overview
Problem
Inverters used in electric drives and vehicles often experience overheating, which can compromise their reliable operation.
Innovation Solution
An inverter with controllable switches and a control device that adjusts the switching frequency based on the temperature of elements within the inverter, with the second switching frequency determined according to the operating point of the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the switching frequency is reduced to control temperature, then the temperature of inverter elements is reduced, but AC current ripple and motor losses increase
Solution Approach 1:
The switching frequency is made dynamic rather than fixed. The control device adjusts the switching frequency based on real-time temperature measurements and motor operating points, allowing the system to optimize between temperature control and performance maintenance across different operating conditions
Solution Approach 2:
The switching frequency parameter is changed adaptively based on temperature and operating point conditions. By modifying this key parameter dynamically, the system resolves the contradiction between maintaining low temperature and avoiding excessive motor losses
2Temperature
If the switching frequency is reduced to control temperature, then the temperature of inverter elements is reduced, but AC current ripple increases
Solution Approach 1:
The switching frequency is dynamically adjusted based on operating conditions. At high motor speeds where AC current ripple is more acceptable, the frequency can be reduced more aggressively for temperature control. At low speeds where ripple is more critical, the frequency is reduced less
Solution Approach 2:
The switching frequency parameter is modified adaptively according to temperature and operating point, allowing the system to balance temperature management against the generation of harmful AC current ripple
3Temperature
If the switching frequency is reduced to control temperature, then the temperature of inverter elements is reduced, but NVH load increases
Solution Approach 1:
The switching frequency is made dynamic to account for NVH considerations at different operating points. The system accepts higher NVH load at high speeds where it is less noticeable, while maintaining lower NVH at low speeds where it is more critical
Solution Approach 2:
The switching frequency parameter is adjusted based on temperature and operating point to balance temperature control against NVH generation, accepting trade-offs that are more acceptable at certain operating conditions
Data Source
AI summary
The inverter comprises input terminals (IT+, IT−), output terminals (OT), controllable switches (Q, Q′) connected to the input terminals (IT+, IT−) and to the output terminals (OT), and a control device (116) configured to control the controllable switches (Q, Q′) such that the controllable switches (Q, Q′) convert a DC voltage (E) at the input terminals (IT+, IT−) into an AC voltage at the output terminals (OT) intended to drive an electric motor (108), the control device (116) being configured to control the controllable switches (Q, O′) according to a first switching frequency and, in response to a temperature (Tj, Tc) of an element (118, Q) of the inverter (110), to a second switching frequency, the control device (116) being configured to determine the second switching frequency according to an operating point of the motor (108).