Active Common-Mode Damping in Multi-Phase Power Converters
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Solution Overview
Problem
Power converters with virtual ground connections face challenges in damping common-mode resonance, which leads to additional losses and performance degradation due to low natural damping in high-performance filters, and existing damping methods either increase system cost or fail under non-ideal conditions.
Innovation Solution
A method that determines the common-mode current's resonance frequency component using a band-pass filter and injects a delayed feedback signal into the common-mode voltage reference to actively dampen the resonance without additional circuitry or sensors, relying solely on output filter parameters, thus maintaining efficiency across varying AC frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If high-performance low-loss LCL filter is used, then filter performance is improved, but common-mode resonance is intensified due to low natural damping
Solution Approach 1:
The patent implements active common-mode damping by injecting a feedback signal into the common-mode voltage reference. The feedback signal is generated by filtering the common-mode current through a band-pass filter tuned to the resonance frequency, creating a control loop that actively counteracts the resonance without requiring additional passive damping components.
Solution Approach 2:
The patent changes the electrical parameters (voltage and current) at the resonance frequency through active control. By dynamically adjusting the common-mode voltage reference based on the detected resonance conditions, the system modifies the operating parameters to suppress resonance while maintaining the high-performance filter characteristics.
2Reliability
If passive damping with resistive components is used, then common-mode resonance is mitigated, but system cost increases and performance decreases
Solution Approach 1:
The patent enables the power converter to dampen its own common-mode resonance using its existing control infrastructure. The resonance damping function is integrated into the existing common-mode control loop, allowing the system to self-regulate without external auxiliary damping circuits or additional passive components.
Solution Approach 2:
The patent makes the existing common-mode control circuitry perform dual functions: maintaining common-mode voltage regulation and actively damping resonance. The same control loop and processing units that manage common-mode voltage also generate the damping feedback signal, eliminating the need for separate damping circuitry.
3Reliability
If active damping with additional sensors is used, then common-mode resonance is mitigated, but device complexity increases
Solution Approach 1:
The patent enables the power converter to dampen its own common-mode resonance using its existing control infrastructure. The feedback signal is generated from the common-mode current that is already present in the system, eliminating the need for additional sensors or measurement devices.
Solution Approach 2:
The patent implements active common-mode damping by injecting a feedback signal into the common-mode voltage reference. The feedback signal is generated by filtering the common-mode current through a band-pass filter tuned to the resonance frequency, creating a control loop that actively counteracts the resonance without requiring additional passive damping components.
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
Effectively attenuates resonance near the resonance frequency without increasing common-mode current components above the resonance frequency, ensuring stable operation without additional circuitry or measurements, and is adaptable to varying AC frequencies.
Implementation Method 1
A frequency component of the common-mode current at the resonance frequency of the virtual ground resonant circuit is determined by using a band-pass filter, for example
Implementation Method 2
The determined resonance frequency component may then be used to form a feedback signal, for example by injecting the determined resonance frequency component into a common-mode voltage reference
Implementation Method 3
A stable feedback loop may be formed by delaying the determined frequency component such that its phase shift is essentially 360° with respect to the actual common-mode current
Implementation Method 4
The virtual ground connection may be used for limiting high frequency fluctuation of the inverter DC bus with respect to a ground potential
Implementation Method 5
a strong resonance may arise via a common-mode LC circuit as the natural damping of the circuit (i.e. losses at a resonance frequency) may be very low
Data Source
Figure 1~2
Figure 3~4
AI summary
The present disclosure describes a method and arrangement for damping a resonant component of a common-mode current of a multi-phase power converter comprising an output filter with a virtual ground connection to the power converter. In the method and arrangement, the common-mode current is determined, a feedback signal is formed on the basis of the common-mode current, and the feedback signal is injected into a common mode current reference in order to dampen the resonance frequency component. A delay is added to the feedback signal so that the feedback signal has a sufficient phase margin with respect to a subsequent cycle of the resonance frequency component of the common-mode current.