Polyphase Inverter Control for Switching Loss Reduction
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Solution Overview
Problem
Current PWM control methods for polyphase inverters, particularly in automotive applications, face challenges in reducing switching losses and conducted disturbances in double three-phase rotating electrical machines, which complicates the control device and increases electromagnetic compatibility issues.
Innovation Solution
A device that generates switching signals using a set of control strategies to optimize PWM control for a double three-phase rotating electric machine, selecting strategies based on speed of rotation and power factor to reduce switching losses and effective current in the decoupling capacitor, incorporating centered vector PWM, vector PWM with shifting, and generalized discontinuous PWM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PWM control methods are used for double three-phase machines, then the control device complexity increases, but switching losses and conducted disturbances are not sufficiently reduced
Solution Approach 1:
The patent segments the control of the double three-phase machine into two independent three-phase control systems. Each three-phase system is controlled separately using established PWM techniques, avoiding the need to develop complex control algorithms for the entire six-phase system. This segmentation reduces control device complexity while maintaining effectiveness in reducing switching losses and conducted disturbances.
Solution Approach 2:
The patent applies copying by using proven three-phase PWM control strategies for each of the two three-phase systems in the double three-phase machine. Instead of creating entirely new control methods, the solution copies and adapts existing successful three-phase control approaches, thereby reducing control complexity while achieving the desired reduction in switching losses and electromagnetic disturbances.
2Stability of the object's composition
If decoupling capacitor is used to stabilize supply voltage, then voltage stability is improved, but effective current in the capacitor increases causing larger supply voltage ripples
Solution Approach 1:
The patent employs periodic PWM switching actions that are synchronized and coordinated between the two three-phase systems. By using periodic control with appropriate timing and phase relationships, the input current ripple frequency is increased, allowing the decoupling capacitor to more effectively smooth voltage variations. This periodic coordinated control reduces the effective current stress on the capacitor while maintaining voltage stability.
Solution Approach 2:
The patent changes the operating parameters of the PWM control, specifically the switching frequencies and phase relationships between the two three-phase systems. By optimizing these parameters, the input current harmonics are reduced and better distributed, which decreases the effective current through the decoupling capacitor while maintaining supply voltage stability, thereby reducing supply voltage ripples.
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
The device according to the invention controls a polyphase inverter (10, 14, 17) intended for powering from a DC current source (CC) a polyphase rotating electric machine (1). The device is of the type of those generating commutation functions driving commutation elements (9, 13) of the inverter in such a way as to obtain a reduction of the losses in the commutation elements and a decrease of an effective current in a decoupling capacitor (16) of the source (CC). According to the invention, this reduction and this decrease are obtained by means of a set of control strategies (21, 24) determining the commutation functions by using additional degrees of freedom of the polyphase machine (1) with respect to a three-phase reference machine. The polyphase machine comprises first and second phase windings forming a first three-phase system (2, 3, 4) and a second three-phase system (5, 6, 7) with distinct neutral points (11, 15) offset angularly by a predetermined angle of offset (Θ). The first and second phase windings are linked respectively to three first and three second power arms (8, 12) formed by the commutation elements.