LC Filter Converter Control via Corrective Flux
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Solution Overview
Problem
Electrical converters with LC filters face significant power losses and instability due to resonant oscillations, which are difficult to dampen effectively, leading to inadequate current profiles and potential system instability.
Innovation Solution
A method involving an outer control loop that uses a mathematical model and a quadratic cost function to determine a corrective flux, which is added to the estimated flux to generate control input signals for the converter, actively damping oscillations caused by the LC filter, thereby improving stability and reducing power losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an LC filter is used without a damping resistor, then power losses are reduced, but the system becomes unstable due to resonant oscillations
Solution Approach 1:
The patent implements a control method that uses feedback from the system state to generate corrective flux signals. The controller continuously monitors the electrical converter's operation and adjusts the corrective flux based on the actual system state, creating a closed-loop feedback mechanism that actively dampens resonant oscillations without requiring passive resistive damping, thereby maintaining system stability while minimizing power losses.
Solution Approach 2:
The patent introduces a corrective flux as an intermediary control element that mediates between the LC filter's resonant behavior and the system's stability requirements. This corrective flux acts as a virtual damping mechanism, providing the necessary stabilization without the energy dissipation associated with physical resistors, thus resolving the contradiction between power loss reduction and stability maintenance.
2Loss of energy
If an LC filter is used without a damping resistor, then the current profile becomes inadequate with slow decay rate, but adding a resistor increases power losses
Solution Approach 1:
The control method employs feedback mechanisms that monitor the current profile and adjust the corrective flux accordingly. This active control approach enables the system to achieve appropriate current decay rates by dynamically adjusting the corrective flux based on real-time system state, eliminating the need for resistive damping while maintaining adequate current profile characteristics.
Solution Approach 2:
The patent replaces the mechanical/passive resistive damping mechanism with an active electronic control mechanism. Instead of using a physical resistor to provide damping and improve current decay rate, the system uses a controller that generates corrective flux signals based on mathematical models and cost functions, substituting electronic control for passive mechanical damping components.
3Stability of the object's composition
If model predictive control is used to dampen oscillations, then computational complexity increases, but system stability is improved
Solution Approach 1:
The patent applies parameter changes by modifying the flux parameters through corrective flux addition rather than fundamentally changing the control architecture. The method maintains the existing model predictive control framework but adjusts specific flux parameters dynamically, reducing the overall computational complexity while still achieving oscillation dampening and system stability improvement.
Data Source
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AI summary
An electrical converter (12) is interconnected via a filter (14) with an electrical load (16) or an electrical power source (20). A method for controlling the converter (12) comprises the steps of: receiving a reference flux (ψ*i) for the electrical converter (12); determining output signals (y) comprising currents and/or voltages measured in the filter (14); determining an estimated flux (ψi) from the output signals (y); determining a corrective flux (ψi,damp) from the output signals (y) based on a mathematical model of the filter (14) and a quadratic cost function; determining control input signals (u) for the electrical converter (12) based on a sum of the estimated flux (ψi) and the corrective flux (ψi,damp); controlling the converter (12) with the control input signals (u); and algorithmic filtering of at least one of the output signals (y) by applying a signal filter (32) to the at least one output signal, which is designed for amplifying the at least one output signal at a resonance frequency (40) of the filter (14), whereby the corrective flux (ψi,damp) is determined from the filtered output signals.