Inverter Control Adjusting Phase Angle for Even Switch Thermal Loading
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inverter control methods for electrical machines lead to uneven thermal loading of power semiconductor switches, especially at low rotation speeds, resulting in inefficiencies and increased complexity due to the need for switches to handle long switch-on times and high currents.
Innovation Solution
The method involves controlling the inverter to adjust the phase angle of the current space vector relative to the nominal phase angle based on rotation speed, allowing for even loading of switches by relieving overloaded switches and increasing the load on others, thereby optimizing the loading distribution and reducing thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If space vector modulation is used to control the inverter, then the electrical machine can be supplied with polyphase electric current, but individual power semiconductor switches are thermally loaded with high currents and long switch-on times especially at low rotation speeds
Solution Approach 1:
The patent applies dynamics by making the inverter control adaptive to operating conditions. The control device dynamically adjusts switching patterns based on detected rotation speed, applying different switching strategies for low-speed versus high-speed operation. This resolves the contradiction by allowing the system to maintain power output while reducing thermal loading at low speeds through speed-dependent control adjustments.
Solution Approach 2:
The patent changes operational parameters (switching frequency, switch-on time, phase angle) based on rotation speed. At low speeds, the control device modifies these parameters to reduce thermal stress on individual switches, while at high speeds it returns to standard parameters to maintain power output. This parameter adaptation resolves the contradiction between power delivery and thermal management.
2Speed
If power semiconductor switches are configured for very long switch-on times and very large currents to handle low-speed operation, then the inverter can operate at low rotation speeds, but the inverter becomes elaborate in terms of technology
Solution Approach 1:
The control device dynamically adapts switching patterns based on rotation speed detection. At low speeds, it uses extended switch-on times and alternative switching sequences to maintain operation, while at high speeds it uses standard switching. This dynamic adaptation allows the inverter to handle low-speed operation without requiring hardware configured for extreme conditions, thus reducing overall device complexity.
Solution Approach 2:
The patent employs periodic switching sequences that cycle through different switching states. At low speeds, it uses longer periodic cycles with multiple switching states to distribute thermal load, while at high speeds it uses shorter cycles. This periodic variation allows low-speed operation without requiring permanently oversized components, reducing device complexity.
3Loss of energy
If a particular zero vector is used in particular angular regions to reduce switching losses, then switching losses are reduced in certain situations, but the inverter is loaded unevenly in other situations and efficiency is reduced
Solution Approach 1:
The control device dynamically selects switching patterns based on the current operating point (rotation speed and phase angle). It determines whether to use zero vectors or active switching patterns based on real-time conditions, optimizing the balance between switching loss reduction and efficient power delivery. This dynamic selection resolves the contradiction by adapting to different operational contexts.
Solution Approach 2:
The patent changes switching parameters (use of zero vectors, switching frequency, phase angle) based on detected operating conditions. When rotation speed and phase angle indicate favorable conditions, it uses zero vectors to reduce switching losses; otherwise, it uses standard switching patterns to maintain efficiency. This parameter adaptation resolves the contradiction between loss reduction and productivity.
Data Source
AI summary
The invention relates to a method for controlling an inverter (10) using space-vector pulse width modulation, in particular to control an electric machine, the inverter being equipped with a plurality of controllable switches (S) and being designed to provide a polyphase electric current (IU, IV, IV), in particular to supply polyphase electric current (IU, IV, IV) to the electric machine (14). In said method, a desired current space vector (I1*) having a desired phase angle (alpha1) and a desired amplitude (I1) is predefined, and the inverter (10) is controlled in such a way that a plurality of different successive switching states (V1-V7) is established for the switches (S) in order to provide the electric current (IU, IV, IV) in the form of a current space vector (I2*), the inverter (10) being controlled in such a way that the current space vector (I2*) is provided at a phase angle (alpha2) which differs from the desired phase angle (alpha1), the difference (delta_beta) of the phase angle (alpha2) from the desired phase angle (alpha1) being limited according to a rotational speed (f) of the desired current space-vector (I1*).