Power Converter Controller with Phase-Dependent Carrier Frequency
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Solution Overview
Problem
Power converters with fixed-frequency carriers generate audible magnetostrictive noise due to harmonic currents in reactors, and parallel connections without synchronized carriers can lead to circulating currents, reducing efficiency and reliability.
Innovation Solution
A controller that adjusts carrier frequencies based on phase angles to normalize ripple components and synchronize carrier frequencies across multiple power converters, using a carrier calculating unit to set high and low ripple carrier frequencies within specific limits to reduce noise and prevent circulating currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed-frequency carrier is used in power converters, then the control system is simple and stable, but magnetostrictive noise is generated due to harmonic currents in reactors
Solution Approach 1:
The patent applies dynamics by making the carrier frequency variable rather than fixed. The control system dynamically adjusts the carrier frequency based on the phase angle of the output voltage, switching between high and low frequencies to normalize ripple components and eliminate magnetostrictive noise while maintaining control stability
Solution Approach 2:
The patent changes the carrier frequency parameter dynamically. By switching between high and low carrier frequencies according to phase angle conditions, the system normalizes the ripple current spectrum and eliminates the harmonic components that cause magnetostrictive noise in the reactor
2Power
If multiple power converters are connected in parallel without carrier synchronization, then system capacity is increased, but circulating currents occur between converters
Solution Approach 1:
The patent synchronizes carrier frequencies by dynamically adjusting them based on a common reference signal. All converters use the same phase angle information to switch between high and low frequencies simultaneously, ensuring carrier frequency synchronization and preventing circulating currents while allowing parallel operation for increased system capacity
Solution Approach 2:
The patent uses feedback by monitoring the phase angle of the output voltage and using this information to control the carrier frequency switching. This feedback mechanism ensures that all parallel-connected converters operate with synchronized carriers, preventing circulating currents while maintaining increased system capacity
3Object-generated harmful factors
If carrier frequency is varied to reduce noise, then magnetostrictive noise is suppressed, but control complexity increases
Solution Approach 1:
The patent varies the carrier frequency parameter between two predetermined values (high and low) based on phase angle conditions. This binary switching approach reduces noise by normalizing the ripple spectrum while keeping the control logic relatively simple, as it only requires comparing phase angle information and switching between two fixed frequency values
Data Source
AI summary
The present disclosure provides a controller for a power converter that converts input power to a prescribed form and outputs the power by switching a semiconductor switching device ON and OFF and that has an output circuit including a filtering reactor on an output side, the controller including: a carrier calculating unit that generates a carrier having prescribed frequencies for generating a control signal that switches the semiconductor switching device ON and OFF, wherein the carrier calculating unit generates the carrier such that a carrier frequency at phase angles where ripple components in a current flowing through the reactor are relatively high in magnitude, which is defined as a high ripple carrier frequency, is higher than a carrier frequency at phase angles where the ripple components are relatively low in magnitude, which is defined as a low ripple carrier frequency.