Parallel Power Converter Modulation via Staggered Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for controlling parallel-connected power converters face challenges in achieving high power ratings without additional components, particularly in synchronizing switching sequences across multiple converters, which can lead to increased harmonic distortion and switching losses.
Innovation Solution
The method involves generating complementary switching sequences with staggered starting instants and using a common modulation reference to calculate duty cycles, allowing for efficient control of switch states in parallel-connected converters, thereby increasing effective output pulse frequency without increasing switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional inductances are placed between parallel phases to cope with timing mismatches, then reliability improves, but device complexity increases
Solution Approach 1:
A modulation controller acts as an intermediary device that receives a modulation reference signal and generates synchronized switching sequences for multiple parallel-connected power converters. The controller includes a counter that generates switching sequence signals with controlled phase shifts, eliminating the need for additional inductances between parallel phases while maintaining timing synchronization and reducing device complexity
2Productivity
If switching frequency is increased to reduce output filter size, then productivity improves, but loss of energy increases
Solution Approach 1:
The patent implements periodic switching sequences with optimized duty cycles for parallel-connected power converters. By using complementary switching patterns where converters operate in alternating phases, the effective output pulse frequency is doubled while maintaining the same switching loss level, as each converter switches at the original frequency but their combined output produces pulses at twice the frequency
Solution Approach 2:
The patent changes the switching sequence parameters by introducing phase shifts between parallel converters and optimizing duty cycle values. This parameter optimization allows the system to achieve higher effective output pulse frequency without proportionally increasing switching losses, as the phase-shifted switching patterns create constructive interference in the output waveform
Data Source
Figure 1~2
Figure 3a~3b
Figure 4~5
AI summary
The present disclosure describes a modulation method for controlling at least two parallel-connected, multi-phase power converters. The method comprises generating synchronized switching sequences for the power converters on the basis of a common modulation reference, wherein each synchronized switching sequence comprises a first half sequence followed by a second half sequence, and wherein, for at least one of the power converters, the first half sequence is a rising-edge half sequence rising-edge half sequence and the second half sequence is a falling-edge half sequence, and, for at least one other of the power converters, the first half sequence is a falling-edge half sequence and the second half sequence is a rising-edge half sequence.