Balancer Circuit Control for DC-Link Midpoint Voltage Oscillation
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Solution Overview
Problem
Existing photovoltaic power converter systems experience undesirable DC voltage oscillations at the intermediate point, leading to increased stress on capacitors and potential converter operation perturbations, which existing control methods fail to adequately address.
Innovation Solution
A controller and control method for a balancer circuit that regulates DC voltage balance by determining the phase-angle and magnitude of voltage differences across DC links, providing switching signals to minimize oscillations and optimize power conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a balancer circuit is added to suppress neutral point voltage fluctuations, then voltage stability is improved, but device complexity increases
Solution Approach 1:
The controller continuously monitors the neutral point voltage and uses feedback control to adjust the switching signals of the balancer circuit, dynamically compensating for voltage fluctuations and maintaining stability without requiring complex circuit modifications
Solution Approach 2:
The balancer circuit is designed to perform multiple functions: suppressing neutral point voltage fluctuations, balancing DC link voltages, and optimizing power conversion capacity, thereby reducing the need for separate dedicated circuits for each function
2Productivity
If the balancer circuit actively balances DC voltages, then power conversion capacity is optimized, but energy loss increases
Solution Approach 1:
The balancer circuit operates dynamically, actively engaging when DC voltage imbalance exceeds a threshold and reducing activity when balance is achieved, thereby optimizing power conversion capacity while minimizing unnecessary energy consumption during balancing operations
Solution Approach 2:
The controller adjusts switching parameters and duty cycles based on real-time voltage measurements, optimizing the balancing action to achieve voltage equality with minimal energy loss and maximum power conversion efficiency
Data Source
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Figure 3a
AI summary
A controller (200) for controlling a balancer circuit (130) is configured to: determine a difference value (211) between a first Direct Current, DC, link voltage value (123) across a first DC link (121) of a power converter (110) and a second DC link voltage value (124) across a second DC link (122) of the power converter (110); determine a phase-angle (221) and a magnitude (222) of the difference value (211) for an integer harmonic of a predetermined grid frequency; and provide a switching signal (131) for switching between the first DC link (121) and the second DC link (122) based on the phase-angle (221) and the magnitude (222), wherein the controller (200) is configured to control a mid-point current (125) at a mid-point terminal (113) of the power converter (110) in terms of magnitude and direction based on the switching signal (131).