Inverter Control via Dynamic Switch-On Time for Thermal Balance
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Solution Overview
Problem
Existing inverter control methods using space vector modulation lead to thermal overloading of power semiconductor switches and freewheeling diodes, especially at low rotation speeds, due to uneven thermal loading, which complicates the technology and reduces the service life of the inverter.
Innovation Solution
The method involves varying the switch-on time of switching states based on the nominal thermal loading value, set by temperature measurements of the switches and freewheeling diodes, to achieve even thermal distribution and reduce thermal peak values, thereby simplifying the inverter design and extending its service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If space vector modulation is used to control the inverter, then the inverter can provide polyphase electric current and voltage effectively, but individual power semiconductor switches and freewheeling diodes suffer from uneven thermal loading especially at low rotation speeds
Solution Approach 1:
The patent applies dynamics by making the switch-on time of zero potential switching states variable rather than fixed. The control device dynamically adjusts the switch-on time based on temperature feedback from sensors monitoring the switches and freewheeling diodes. This dynamic adjustment allows the system to adapt to changing thermal conditions, particularly at low rotation speeds where thermal loading is most severe, thereby resolving the contradiction between effective inverter control and uneven thermal loading.
Solution Approach 2:
The patent implements feedback control by using temperature sensors to monitor the thermal state of power semiconductor switches and freewheeling diodes. The measured temperature information is fed back to the control device, which then adjusts the switch-on time of zero potential switching states accordingly. This closed-loop feedback mechanism enables the system to maintain balanced thermal loading across all components while preserving effective inverter control performance.
2Speed
If power semiconductor switches are configured for very long switch-on times and large currents to handle thermal loading, then the inverter can operate at low speeds, but the inverter becomes elaborate in terms of technology
Solution Approach 1:
The patent applies parameter changes by modifying the switch-on time parameter of zero potential switching states based on temperature conditions. Instead of configuring switches for very long switch-on times and large currents to handle thermal loading at low speeds, the system dynamically adjusts the switch-on time parameter to optimize thermal distribution. This parameter adjustment allows the inverter to operate effectively at low speeds without requiring oversized components or complex configurations.
3Loss of energy
If zero vectors are selectively used in particular angular regions to reduce switching losses, then switching losses are reduced, but individual switches and diodes still suffer from heavy thermal loading in certain control situations
Solution Approach 1:
The patent uses feedback control to monitor the thermal state of individual switches and freewheeling diodes and adjusts the switch-on time of zero potential switching states accordingly. This feedback mechanism ensures that while switching losses are reduced through selective use of zero vectors, the thermal loading of individual components is also balanced by dynamically adjusting switch-on times based on real-time temperature measurements.
Solution Approach 2:
The patent applies local quality by making the switch-on time adjustment component-specific rather than uniform across all switches. The control device individually monitors and adjusts the switch-on time for each zero potential switching state based on the thermal condition of the corresponding switch or freewheeling diode. This localized adjustment ensures that each component operates within its optimal thermal range while maintaining overall system efficiency.
Data Source
AI summary
The invention relates to a method (40) for controlling an inverter (10) using space-vector pulse width modulation, in particular to control an electric machine (14), said inverter (10) being equipped with a plurality of controllable switches (S) and a corresponding plurality of freewheeling diodes (D) and being designed to provide a polyphase electric current (IU, IV, IW) and a polyphase voltage in the form of current space vectors (I*, U*), in particular to supply polyphase electric current (IU, IV, IW) to the electric machine (14). In said method, the inverter (10) is controlled to establish a plurality of different successive switching states (V0-V7) for the switches (S), and the inverter (10) is switched to an off-load switching state (V0, V7) by means of two switching states (V0, V7), a switch-on time (t0-t7) of the switching states (V0-V7) being varied according to a desired load value (m) for the switches (S) and/or for the freewheeling diodes (D), the desired load value (m) being set according to a temperature (Ts, TD) of at least one of the switches (S) and/or one of the freewheeling diodes (D).