Rectifier Phase Control for Switching Loss Reduction
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Solution Overview
Problem
Power converters experience excessive heating due to switching losses, which can lead to premature aging or damage if the maximum operating temperature is exceeded, and existing control methods fail to efficiently manage temperature distribution across phases.
Innovation Solution
Adapting the switch-on and switch-off times of pulse-width-modulated drives to reduce switching operations by merging consecutive pulses in a first electrical phase, effectively halving the switching frequency in that phase, thereby minimizing heating and optimizing temperature distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional uniform control of all switching elements is used, then the power converter can operate with simple control logic, but switching losses cause excessive heating and temperature rise in the switching elements
Solution Approach 1:
The patent applies local quality by differentiating the control strategy for different phases based on their thermal conditions. The control device identifies phases with higher temperature rises and applies reduced switching frequency specifically to those phases, while maintaining normal switching frequency in cooler phases. This localized adaptation optimizes the temperature distribution without unnecessarily reducing the overall power converter performance.
2Temperature
If the switching frequency is reduced to minimize switching losses, then heating is reduced, but the electrical power output capability is also reduced
Solution Approach 1:
The patent implements dynamic control by continuously monitoring the temperature distribution and switching losses in each phase, then dynamically adjusting the switching frequency of individual phases in real-time. This dynamic adaptation allows the system to maintain high power output capability when thermal conditions permit, while actively reducing switching frequency in specific phases when temperature rise becomes excessive, thus optimizing both power output and thermal management.
3Device complexity
If switching operations are performed uniformly across all phases, then the control implementation is simple, but uneven temperature distribution occurs across the power converter phases
Solution Approach 1:
The patent employs feedback control by continuously measuring or estimating the temperature rise and switching losses in each phase, then using this feedback information to adjust the switching frequency of individual phases. The control device calculates the switching losses based on measured current and voltage, identifies phases with excessive temperature rise, and applies compensatory reduced switching frequency to those specific phases, creating a closed-loop thermal management system.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces switching losses and associated heating, allowing for higher electrical power output without exceeding the maximum permissible operating temperature, leading to a more uniform and sustainable temperature distribution across the power converter.
Implementation Method 1
the switching elements are controlled, for example, by means of a pulse width modulation method
Implementation Method 2
switching operations of the switching elements in a power converter are associated with switching losses. These switching losses can cause the switching elements and thus the entire power converter to heat up
Data Source
Figure 1
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AI summary
The invention relates to the controlling of a rectifier with multiple electrical phases. In at least one electrical phase, the duty cycles are merged with one another in two consecutive cycles of the pulse-width modulated controlling, i.e. in a first PWM-pulse, the duty cycle is shifted to the end of the PWM-pulse, and in a subsequent PWM-pulse, the duty cycle is shifted to the start of the PWM-pulse. As a result, there must be no switching process between two consecutive PWM-pulses. In this way, the switching losses and consequently the rise in temperature of the rectifier can be minimised.