Inverter Bridge-Arm Phase Shifting for Ripple Current Reduction
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Solution Overview
Problem
High-frequency ripple currents generated by inverter circuits in power converters can damage capacitors, affecting the stability and lifespan of the converter, and existing solutions to mitigate this often increase costs or require additional components.
Innovation Solution
A power converter with a controller that adjusts the phase difference between the output voltages of bridge arms in the inverter circuit to either exceed or fall within specific thresholds based on the voltage and current directions, reducing the high-frequency ripple current without altering the circuit structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional components are used to reduce high-frequency ripple current, then capacitor reliability is improved, but device complexity and cost increase
Solution Approach 1:
The patent changes the phase angle parameter of the PWM signals driving different bridge arms. By adjusting the phase difference between PWM signals of adjacent bridge arms, the high-frequency ripple currents are made to cancel each other out, reducing the total ripple current without adding any physical components to the circuit.
2Temperature
If additional components are used to reduce high-frequency ripple current, then capacitor temperature is reduced, but manufacturing cost increases
Solution Approach 1:
The patent modifies the operating parameters (phase angles) of the existing circuit rather than adding components. This parameter adjustment reduces the ripple current and consequently the heat generation in capacitors, achieving temperature reduction without increasing manufacturing complexity or cost.
3Power
If switching frequency is increased to improve power conversion, then power efficiency is improved, but high-frequency ripple current increases
Solution Approach 1:
The patent converts the harmful high-frequency ripple currents into a beneficial effect by deliberately introducing phase differences between bridge arms. The ripple currents from different bridge arms, which would normally be harmful, are made to cancel each other out through phase-shifted PWM signals, thus reducing the net ripple current while maintaining high switching frequencies.
Data Source
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AI summary
This application provides a power converter and a method for controlling an inverter circuit, applied to the field of power electronics technologies, to reduce costs while reducing a high-frequency ripple current caused by the inverter circuit. The power converter includes the inverter circuit and a controller. The inverter circuit includes a plurality of bridge arms. The controller is configured to: if output voltage directions of any two bridge arms in the plurality of bridge arms are the same and output current directions of the any two bridge arms are the same, control a phase difference between output voltages output by the any two bridge arms to be greater than a first threshold. Based on this, when output voltage directions of any two bridge arms in the inverter circuit are the same and output current directions corresponding to the two bridge arms are the same, the controller may control the two bridge arms to enable a phase difference between output voltages of the two bridge arms to be greater than the first threshold, and therefore enable the output voltages of the two bridge arms to be phase-shifted, to reduce the high-frequency ripple current output by the inverter circuit.