Parallel Converter PWM Control for Fast Current Response
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Solution Overview
Problem
Existing power conversion systems struggle to improve control responsiveness of current control on the power system side while reducing switching ripple.
Innovation Solution
A power conversion system interconnected to a multi-phase AC power system, featuring multiple converters in parallel for each phase, controlled using carrier comparison type PWM control with carrier signals having a prescribed phase difference. The control unit detects currents at specific timings, generates a reference voltage, and updates it to enhance control responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If switching frequency is increased to improve control responsiveness, then current control responsiveness is improved, but switching ripple increases
Solution Approach 1:
The patent applies periodic action by using multiple carrier signals with different phases (e.g., three-phase carrier signals with 120-degree phase differences) to perform periodic current detection and reference voltage updates. This periodic multi-phase control approach allows the system to achieve high control responsiveness through frequent updates while the distributed phase structure naturally reduces switching ripple through cancellation effects, thus resolving the contradiction between responsiveness and ripple reduction.
2Object-generated harmful factors
If multiple converters are connected in parallel to reduce switching ripple, then switching ripple is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a control unit that can simultaneously perform multiple functions: controlling multiple parallel converters, detecting currents from multiple phases, generating multiple phase-shifted carrier signals, and updating reference voltages for all converters. This multi-functional control approach enables the system to reduce switching ripple through parallel converter configuration while avoiding the complexity of requiring separate dedicated control circuits for each converter, thus resolving the contradiction between ripple reduction and complexity increase.
Data Source
AI summary
According to an embodiment, a power conversion system includes a plurality of converters and a control unit. The plurality of converters are provided in parallel for each phase of a multi-phase alternating current power system. The control unit uses a plurality of carrier signals having a prescribed phase difference from each other in carrier comparison type pulse width modulation (PWM) control. The control unit detects a current of a primary side of the plurality of converters at each of four or more even-numbered timings when the four or more even-numbered timings are defined at prescribed time intervals during one cycle of a specific carrier signal among the plurality of carrier signals. The control unit generates a reference voltage for the PWM control using a value of the detected current of the primary side and a value of a reference current of the primary side and updates the reference voltage at each of the four or more even-numbered timings. The control unit controls a specific converter among the plurality of converters using the specific carrier signal and the updated reference voltage.