AC/DC Converter Control for Capacitor Voltage Stability
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Solution Overview
Problem
Existing AC/DC conversion circuits in power electronic transformers face issues with voltage fluctuations caused by capacitor reactive power oscillations, leading to device stress and unbalanced DC-side capacitor voltages, which are difficult to control and regulate.
Innovation Solution
A method and apparatus that control an AC/DC conversion circuit by acquiring voltage and current information to adjust the operation of converter units and coupling units, using a controllable device to manage capacitor voltage fluctuations and power flow directions, thereby suppressing voltage and current fluctuations and preventing over-stressing of the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If capacitors are connected in series to achieve DC/DC conversion in MMC structure, then voltage regulation is achieved, but device volume increases and voltage equalization control becomes difficult
Solution Approach 1:
The patent divides the power conversion system into separate AC/DC conversion modules and DC/DC conversion modules. Each module operates independently with its own control strategy, avoiding the need for series-connected capacitors in MMC structure. This segmentation reduces device volume and simplifies control while maintaining full DC/DC conversion capability through the coupling unit.
2Weight of stationary object
If single-phase high-frequency transformer is used for DC/DC conversion, then volume and weight are reduced, but capacitor voltage fluctuations increase due to power fluctuations
Solution Approach 1:
The patent applies different control strategies to different parts of the system. The AC/DC conversion side uses one control method while the DC/DC conversion side uses another, allowing optimization of each section. This enables the use of lightweight high-frequency transformers while maintaining capacitor voltage stability through localized control adjustments.
Solution Approach 2:
The control device predicts power fluctuations and adjusts switching states in advance to prevent capacitor voltage deviations. By performing preliminary action based on predicted power changes, the system maintains voltage stability without requiring larger or more numerous capacitors, thus keeping the transformer lightweight.
3Power
If H-bridge chain structure with DAB is used for AC/DC conversion, then conversion is achieved, but capacitor voltage fluctuations cause adverse effects on the device
Solution Approach 1:
The patent implements a closed-loop control system that continuously monitors capacitor voltages and adjusts switching states in real-time. When voltage deviations are detected, the control device modifies the switching strategy to correct the imbalance, thereby reducing device stress while maintaining AC/DC conversion capability through the H-bridge chain structure.
Data Source
AI summary
Disclosed in embodiments of the present invention are a control method and device for an alternating-current and direct-current conversion circuit, and a computer storage medium. The alternating-current and direct-current conversion circuit comprises a first commutation unit, a second commutation unit, and a coupling unit. By obtaining voltage information and current information of the alternating-current and direct-current conversion circuit, a controllable device of the first commutation unit can be controlled to be turned on in delay or turned off in advance; and the second commutation unit is controlled to work in a controllable rectification state or a controllable inversion state or an uncontrollable rectification state.