Three-Phase Vienna Rectifier Control Reducing Switching Losses
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Solution Overview
Problem
Existing three-phase Vienna rectifiers for on-board charging devices in electric and hybrid vehicles face challenges in reducing switching losses due to measurement errors and inefficient duty cycle applications, leading to significant power wastage.
Innovation Solution
A method of controlling the power factor corrector circuit using pulse width modulation (PWM) signals to systematically switch only two out of three switching arms based on the sign change of setpoint currents, with a 100% duty cycle applied to the arm with intermediate voltage, reducing switching losses by minimizing unnecessary switch operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If duty cycles are applied to all three switching arms based on conventional control methods, then the rectifier can maintain target voltages, but switching losses increase significantly due to unnecessary switch operations
Solution Approach 1:
The patent extracts the control action from all three switching arms and applies it only to two arms. By identifying that one arm can be kept in a fixed state (either always on or always off) based on the sign of its current, the control complexity and switching operations are reduced while maintaining the necessary voltage regulation function through the remaining two arms.
Solution Approach 2:
Instead of applying duty cycle control to all three switching arms equally, the patent applies partial control only to two arms while leaving the third arm in a fixed state. This partial action approach reduces unnecessary switching operations and associated losses while providing sufficient control authority to maintain the required output voltages.
2Measurement precision
If measurement errors occur when input current is close to zero, then the wrong switch may not be driven, but applying conventional duty cycles leads to significant switching losses
Solution Approach 1:
The patent takes preliminary action by determining the sign of the current in advance and using this information to fix the state of one switching arm before control issues arise. By pre-establishing which arm should remain in a fixed state based on current sign analysis, the system avoids the measurement error problem near zero current while also eliminating the switching losses that would occur with conventional duty cycle application.
3Reliability
If all three switching arms are controlled with PWM signals, then voltage regulation is maintained, but the complexity of the control system increases
Solution Approach 1:
The patent extracts the PWM control signal generation from the system by determining the fixed state (on or off) of one switching arm based on current sign. This removes the need to generate and process PWM signals for all three arms, simplifying the control system while maintaining voltage regulation through the remaining two controlled arms.
Solution Approach 2:
Instead of controlling all three arms with PWM and then trying to reduce switching frequency, the patent inverts the approach by deliberately fixing one arm in a non-switching state and only applying PWM control to two arms. This inversion of the conventional control strategy simplifies the control system architecture while maintaining regulation performance.
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 effectively reduces switching losses and maintains target voltages, enhancing the efficiency and reliability of the charging process while minimizing electromagnetic disturbances and harmonic emissions.
Implementation Method 1
a power factor corrector circuit (11, 110), said power factor corrector circuit being a three-phase Vienna rectifier (110) comprising three switching arms (S1, S2, S3), each capable of being connected to one of the respective phases (A, B, C) of the three-phase power supply network (4) via an inductance coil (L1, L2, L3) in series
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention relates to a method for controlling a power-factor-correcting circuit (11) of the three-phase Vienna rectifier type, comprising three switching arms (S1, S2, S3) connected to one of the respective phases of a three-phase network and each comprising a high switch (1H) and a low switch (1L) that can be respectively controlled for a positive and negative network current, by means of control signals having a cyclic ratio determined according to nominal current values at the inlet of the rectifier. During each period of the nominal currents, only two arms out of three are systematically switched according to a change of sign of the nominal currents and the switching state of the switches in question is distributed between the two arms that switch by varying the cyclic ratios according to the values of the voltages between phases at each given moment.