Bus Capacitor Voltage Control for Parallel Non-Isolated Modules
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Solution Overview
Problem
Circulating current between non-isolated modules operating in parallel leads to excessive input current, limiting total output power and potentially damaging modules due to inefficiencies in power distribution.
Innovation Solution
A method and system that adjusts the voltage of bus capacitors in non-isolated modules by comparing input power signals with reference values, decreasing voltage when input power is higher and increasing it when lower, to ensure each module supplies power only to its own stage, thereby reducing or eliminating circulating current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple non-isolated modules are connected in parallel to increase total output power, then the system power capacity is improved, but circulating current occurs between modules causing excessive input current and potential module damage
Solution Approach 1:
The patent changes the operating parameters of each module by dynamically adjusting the bus capacitor voltage. When circulating current is detected, the control system modifies the voltage parameter of the bus capacitor to alter the input impedance of the module, thereby eliminating the circulating current condition while maintaining parallel operation capability
Solution Approach 2:
The patent implements a feedback control mechanism that continuously monitors the input current and bus capacitor voltage of each module. When circulating current is detected through current comparison, the system provides feedback signals to adjust the PWM duty cycle or bus capacitor voltage, creating a closed-loop control system that actively suppresses circulating current
2Power
If modules operate with higher input current to meet power demand, then the total output power is improved, but current limiting is triggered preventing rated power achievement
Solution Approach 1:
By dynamically adjusting the bus capacitor voltage parameter, the system changes the input characteristics of each module to prevent current limiting activation, allowing the modules to deliver rated power without triggering protective current limits
3Reliability
If circulating current is eliminated through voltage adjustment, then module reliability is improved, but control system complexity increases
Solution Approach 1:
While feedback control adds complexity, the patent implements a relatively simple feedback mechanism using basic current comparison and PWM duty cycle adjustment, which is manageable in practical power supply systems
Solution Approach 2:
The bus capacitor voltage serves as an intermediary parameter that mediates between the input current and output power. By controlling this intermediate voltage parameter, the system indirectly controls the circulating current without requiring direct intervention in the power flow path
Data Source
AI summary
The present disclosure discloses a method and system for reducing a circulating current between a plurality of non-isolated modules operating in parallel. The input terminals and the output terminals of the plurality of non-isolated modules are respectively connected in parallel, and each of the non-isolated modules comprises a first stage converter, a bus capacitor and a second stage converter, which are electrically connected in sequence. For each of the non-isolated modules, the method comprises: comparing a first signal reflecting the input power of the non-isolated module with a reference value to obtain a comparison result; and adjusting the voltage of the bus capacitor according to the comparison result, wherein the voltage of the bus capacitor is decreased when the first signal is greater than the reference value, and the voltage of the bus capacitor is increased when the first signal is less than the reference value.