Parallel Power Converter Startup Control for Inrush Current Reduction
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Solution Overview
Problem
In power conversion systems where multiple power converters are directly connected to a DC system, controlling the DC voltages simultaneously is challenging due to timing errors and communication delays, leading to increased inrush currents during startup, which can damage semiconductor switching elements.
Innovation Solution
A power conversion system where the first power converter operates before the second, with its control device adjusting the voltage of the first DC terminal based on the status of the second power converter to reduce inrush currents by staggering the startup process and maintaining voltage balance across DC terminals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple power converters are directly connected to a DC system, then the system capacity and power conversion capability are improved, but inrush current increases during startup due to voltage timing errors and communication delays
Solution Approach 1:
The patent applies preliminary action by having the first power converter start up and stabilize its DC voltage before the second power converter is connected. The control device of the first power converter performs preliminary voltage regulation based on expected load conditions, ensuring that when the second converter connects, the voltage difference is minimized. This prevents inrush current by preparing the system state in advance.
Solution Approach 2:
The patent implements dynamics by enabling the control device to dynamically adjust the DC voltage of the first power converter in real-time based on the connection status and load conditions of the second power converter. The control device monitors system state and continuously optimizes voltage output, transitioning from a static voltage approach to a dynamic adaptive approach that responds to changing system conditions.
2Stability of the object's composition
If DC voltages of all power converters are controlled simultaneously, then voltage balance is improved, but control difficulty increases due to timing errors and communication delays
Solution Approach 1:
The patent applies segmentation by dividing the control of multiple power converters into hierarchical levels. The control device of the first power converter independently manages its own DC voltage and provides reference voltage information to the second converter. This segmented control approach avoids the complexity of centralized simultaneous control while maintaining voltage balance through coordinated operation of individual control units.
Solution Approach 2:
The patent implements feedback by having the control device of the first power converter monitor its own DC voltage output and adjust it based on detected voltage deviations. The control device uses feedback signals from voltage detectors to continuously regulate the converter output, ensuring voltage balance without requiring complex inter-converter communication and timing synchronization.
3Loss of time
If AC circuit breakers are turned on simultaneously for all power converters, then startup time is reduced, but charging current increases
Solution Approach 1:
The patent applies preliminary action by having the first power converter complete its AC circuit breaker operation and DC voltage stabilization before the second power converter's AC circuit breaker is closed. This staged approach allows the first converter to prepare the DC system in advance, so when the second converter connects, the charging current is minimized due to the pre-established voltage reference.
Data Source
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AI summary
A power conversion system includes a first power converter (1A) and a second power converter (1B) which are capable of converting an alternating-current (AC) power into a direct-current (DC) power or converting a DC power into an AC power. The first power converter (1A) is interconnectable to a first AC system (9A) via a first AC circuit breaker (13A). The second power converter (1B) is interconnectable to a second AC system (9B) via a second AC circuit breaker (13B). A first DC terminal (2A, 3A) of the first power converter (1A) and a second DC terminal (2B, 3B) of the second power converter (1B) are connectable. The first power converter (1A) begins operation prior to the second power converter (1B). A first control device (100) controls a voltage of the first DC terminal (2A, 3A), based on a status of the second power converter (1B) sent from a second control device (100B).