Inverter Control via Phase Angle Deviation for Thermal Load Distribution
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Solution Overview
Problem
Existing inverter control methods using space vector modulation lead to thermal overload of power semiconductor switches, particularly at low rotational speeds, due to uneven loading of switches, making the inverter complex and inefficient.
Innovation Solution
The method adjusts the phase angle of the current space vector based on power dissipation and temperature of switches to distribute the load uniformly, relieving overloaded switches and increasing the lifespan of the inverter by varying the load on switches and phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If space vector modulation is used to control the inverter, then the electric current can be provided in polyphase form, but some power semiconductor switches are thermally overloaded at low rotational speeds
Solution Approach 1:
The patent applies dynamics by making the inverter control adaptive to operating conditions. The control device dynamically adjusts the switching states based on detected temperature or power dissipation of switches, allowing the system to optimize its operation in real-time. This resolves the contradiction by enabling the inverter to maintain control capability while adapting switch loading conditions to prevent thermal overload at different rotational speeds.
Solution Approach 2:
The patent changes the control parameters by deviating the current space vector phase angle from the reference phase angle when thermal overload is detected. This parameter change redistributes the load among switches, preventing any single switch from being permanently thermally overloaded while maintaining the polyphase current output capability.
2Reliability
If power semiconductor switches are designed for very long switch-on times and very large currents, then thermal overload can be prevented, but the inverter becomes technically complex
Solution Approach 1:
Instead of designing switches for worst-case continuous high current operation, the patent changes the operational parameters by dynamically adjusting switching states based on actual thermal conditions. This allows the use of less robust (simpler, cheaper) switches that are sized for normal operating conditions, while the control system prevents thermal overload through adaptive switching, thereby reducing inverter complexity.
Solution Approach 2:
The patent implements feedback control by detecting the temperature or power dissipation of switches and using this information to adjust the switching states. This feedback mechanism allows the system to prevent thermal overload without requiring switches to be oversized for worst-case scenarios, thus reducing device complexity while maintaining reliability.
3Loss of energy
If certain zero vectors are used in certain angle ranges, then switching losses can be reduced, but some switches are permanently thermally loaded and the inverter is loaded non-uniformly
Solution Approach 1:
The patent makes the selection of zero vectors dynamic rather than static. Instead of using certain zero vectors in fixed angle ranges, the control device dynamically selects which zero vectors to apply based on real-time detection of switch temperatures or power dissipation. This dynamic adaptation allows the system to reduce switching losses while simultaneously preventing permanent thermal overload of specific switches, achieving uniform load distribution.
Solution Approach 2:
The patent changes the control strategy by deviating the current space vector phase angle from the reference phase angle when thermal imbalance is detected. This parameter change, combined with selective zero vector application, redistributes the thermal load among switches uniformly while maintaining energy efficiency by reducing switching losses through appropriate zero vector selection.
Data Source
AI summary
The invention relates to a method (60) 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 being designed to provide a polyphase electric current (IU, IV, IW), in particular to supply multiphase electric current to an electric machine (14). In said method, a reference phase angle (alpha_R) is predefined, and the inverter (10) is controlled in such a way that a plurality of different successive switching states (V0-V7) is established for the switches (S) in order to provide the electric current (IU, IV, IW) in the form of a current space vector (I*). The inverter (10) is controlled in such a way that the current space vector (I*) is provided at a phase angle (alpha_I) which differs from the reference phase angle (alpha_R), a difference (delta_I) of the phase angle (alpha_I) from the reference phase angle (alpha_R) being determined according to a power loss (PA, PB, PC) and/or a temperature (TA, TB, TC) of at least one of the switches (S).