Model Predictive Damping for Electrical Converter Oscillations
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Solution Overview
Problem
The introduction of an LC filter in electrical converter systems to reduce current harmonics leads to resonant behavior, which can be mitigated by passive damping but at the cost of energy efficiency, and existing control methods require additional damping loops or high computing power.
Innovation Solution
A control method using model predictive control that determines a modified pulse pattern by time-shifting switching instants to damp resonant oscillations, eliminating the need for passive damping and reducing computing power, while maintaining strong attenuation of higher current harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an LC filter is installed to reduce current harmonics, then current distortion is attenuated, but resonant behavior is introduced into the system
Solution Approach 1:
The patent introduces a damping controller as an intermediary component between the tracking controller and the electrical converter. This damping controller acts as a mediator that processes the reference pulse pattern from the tracking controller and generates a modified pulse pattern that compensates for resonant oscillations, thereby resolving the contradiction between harmonic attenuation and system stability
Solution Approach 2:
The damping controller implements feedback by continuously monitoring the system state and adjusting the pulse pattern accordingly. The controller uses the reference pulse pattern and system parameters to generate corrective actions that dampen resonant oscillations, creating a closed-loop control mechanism that maintains stability while preserving the harmonic filtering benefits of the LC filter
2Stability of the object's composition
If passive damping with a resistive element is added to the LC filter, then resonant behavior is mitigated, but energy efficiency is reduced due to energy dissipation
Solution Approach 1:
The patent replaces the passive mechanical/resistive damping approach with an active electronic control system. Instead of using a resistive element that dissipates energy physically, the damping controller uses computational algorithms to generate corrective pulse patterns that electronically compensate for resonant oscillations, achieving the same stability benefit without energy loss
Solution Approach 2:
The damping controller dynamically adjusts control parameters including the pulse pattern timing and amplitude based on system conditions. By changing these control parameters in real-time, the system achieves adaptive damping that maintains stability while minimizing energy consumption, unlike fixed passive damping components
3Stability of the object's composition
If an additional damping loop with an auxiliary controller is added, then resonant oscillation is compensated, but device complexity increases
Solution Approach 1:
The patent merges the damping control function with the existing tracking controller by having the damping controller process the reference pulse pattern from the tracking controller and output a modified pulse pattern. This integrated approach combines multiple control functions in a unified structure, reducing overall system complexity compared to completely separate control loops
Solution Approach 2:
The damping controller is designed with multi-functionality, serving both as a harmonic filter coordinator and a resonant oscillation compensator. By making the controller universal in its capabilities, the patent reduces the need for specialized dedicated components for each control function, thereby simplifying the overall device architecture
4Manufacturing precision
If optimized pulse patterns are selected to improve steady state performance, then current distortion is reduced, but higher current harmonics are supplied to the electrical machine
Solution Approach 1:
The patent applies dynamic modulation to the pulse pattern by introducing time-varying adjustments based on system conditions. The damping controller dynamically modifies the reference pulse pattern in real-time, creating a dynamic control strategy that adapts to changing operating conditions and effectively reduces current harmonics while maintaining steady state performance
Solution Approach 2:
The control system employs periodic switching actions with optimized timing. By carefully designing the periodic pulse pattern and its modifications, the system achieves reduced current distortion and minimized harmonic content through synchronized switching that aligns with the fundamental frequency and its harmonics
Data Source
AI summary
A method for controlling an electrical converter system, including: determining a reference output (ωm*) and an estimated output (ωm) of the electrical converter system based on measurements in the electrical converter system; determining an optimized pulse pattern (ui,n) by selecting from a table of precalculated optimized pulse patterns, which is chosen based on the reference output (ωm*) and the estimated output (ωm), a pulse pattern including a sequence of switching instants (t*) applied to the electrical converter system; determining a resonant oscillation (ψs,h) in the electrical converter system, the resonant oscillation(ψs,h) is composed of an electrical machine and a LC filter of the electrical converter system; determining a sequence of future states of the electrical converter system by solving a mathematical model of the electrical converter system subject to optimizing a cost function and subject to a constraint that a modified pulse pattern (ui) is applied to the electrical converter system, which modified pulse pattern (ui) comprises time shifted switching instants with respect to the optimized pulse pattern (ui,n), wherein the cost function comprises a term compensating the resonant oscillation (ψs,h) with a pulse response oscillation caused by the time shifted switching instants of the modified pulse pattern (ui) and wherein the mathematical model is constrained such that the switching instants of the modified pulse pattern (ui) have the same order as the switching instants of the optimized pulse pattern (ui,n); applying the modified pulse pattern (ui) to the electrical converter system.