Inverter Switch Control with Variable Carrier Frequency
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Solution Overview
Problem
Inverters used in electrically driven vehicles face inefficiencies due to switching losses and peak-valley values of DC link voltage, which are exacerbated by constant carrier frequencies, leading to increased capacitance, weight, and cost requirements.
Innovation Solution
A control device adjusts the carrier frequency based on operating point information, reducing the frequency in specific operating ranges to lower switching losses without increasing DC link capacitor capacitance, thereby optimizing inverter efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a constant maximum carrier frequency is used to drive switching elements, then switching speed and response time are improved, but switching losses increase significantly
Solution Approach 1:
The patent applies dynamics by transitioning from a constant carrier frequency to a variable carrier frequency that adapts to operating conditions. The control device dynamically adjusts the carrier frequency based on the instantaneous operating point (torque and rotation speed), allowing the system to optimize between switching speed and switching losses in real-time during partial-load and full-load operations.
Solution Approach 2:
The patent changes the parameter of carrier frequency from a fixed maximum value to a variable value that depends on operating point information. By modifying the carrier frequency parameter according to torque and rotation speed, the system reduces switching losses during partial-load operation while maintaining adequate switching performance when needed.
2Loss of energy
If carrier frequency is reduced to lower switching losses, then energy efficiency is improved, but peak-valley values of DC link voltage increase
Solution Approach 1:
The patent uses dynamics to continuously adjust the carrier frequency based on the instantaneous operating point rather than using a fixed frequency. This dynamic adaptation allows the system to reduce switching losses when operating at partial load while managing DC link voltage variations through real-time control adjustments.
Solution Approach 2:
The control device receives operating point information (torque and rotation speed) as feedback and uses this information to determine the appropriate carrier frequency. This feedback mechanism enables the system to adjust the carrier frequency in response to changing operating conditions, balancing switching loss reduction with DC link voltage stability.
3Stability of the object's composition
If DC link capacitor capacitance is increased to handle peak-valley voltage values, then voltage stability is improved, but device weight, volume, and cost increase
Solution Approach 1:
Instead of using a larger DC link capacitor to handle voltage variations, the patent employs dynamic carrier frequency adjustment. This active control approach manages DC link voltage stability through real-time frequency adaptation, avoiding the need for increased capacitance and the associated weight, volume, and cost penalties.
Solution Approach 2:
The patent changes the carrier frequency parameter dynamically based on operating conditions rather than relying on increased capacitor capacitance. This parameter change strategy provides an alternative solution to voltage stability problems that avoids the physical constraints of larger capacitors.
4Loss of energy
If carrier frequency is reduced in partial-load operation, then switching losses are reduced, but harmonic distortions may increase
Solution Approach 1:
The patent applies dynamics by continuously adapting the carrier frequency to the instantaneous operating point rather than using a fixed frequency. This dynamic adjustment allows the system to reduce switching losses during partial-load operation while the control device manages harmonic distortions through intelligent frequency selection based on real-time operating conditions.
Solution Approach 2:
The patent modifies the carrier frequency parameter based on operating point information to reduce switching losses. The control device carefully manages this parameter change to balance switching loss reduction with harmonic distortion control, using the variable frequency approach to optimize overall system performance.
Data Source
AI summary
A control device (8) for an inverter (2) that feeds an electric machine (3), wherein the control device (8) is configured to provide pulse-width-modulated switching signals (15) at a carrier frequency to drive switching elements (12) of the inverter (2), wherein the control device (8) is configured to ascertain the carrier frequency within at least one operating range (22, 23) depending on a piece of operating point information that describes an operating point defined by a rotation speed and a torque of the electric machine (3) in such a way that the carrier frequency is reduced within the at least one operating range (22, 23) compared to a maximum carrier frequency operating point at which a maximum carrier frequency is specified in the operating range.