Active Filter Harmonic Compensation Method
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Solution Overview
Problem
Current methods for reducing current harmonics in power electronic converters, such as active filters, face challenges including high costs, additional losses, reduced dynamics, and susceptibility to vibration due to the need for precise measurement and control of individual harmonic components, which limits their effectiveness and efficiency.
Innovation Solution
A method involving a voltage-impressing active filter that compensates for current harmonics by determining the amplitude and phase of the fundamental sinusoidal component of the input current and using this information to set a filter voltage that reduces the mains current harmonics, allowing for reliable and frequency-independent compensation over a wide frequency range without the need for precise measurement of individual harmonic components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If passive filters are used to reduce current harmonics, then harmonic distortion is reduced, but material costs and additional losses increase significantly
Solution Approach 1:
The patent replaces passive mechanical filter components (inductors, capacitors, resistors) with an active electronic control system that uses power electronic converters and control algorithms to generate compensating currents, thereby eliminating the need for bulky passive filter elements and their associated energy losses
2Object-generated harmful factors
If passive filters are used to reduce current harmonics, then harmonic distortion is reduced, but device complexity and cost increase
Solution Approach 1:
The patent substitutes complex passive filter hardware with a control-based active filter system that uses digital signal processing and power electronic switching to achieve harmonic compensation, reducing both physical complexity and material costs
Solution Approach 2:
The patent dynamically adjusts control parameters (switching frequency, pulse widths, compensation current magnitudes) based on real-time harmonic measurements, allowing the system to adapt to varying load conditions without requiring complex fixed passive filter designs
3Object-generated harmful factors
If active filters are used to reduce current harmonics, then harmonic compensation is achieved, but measurement precision and control accuracy requirements increase
Solution Approach 1:
The patent implements a feedback control loop where harmonic currents are measured, processed through Fourier analysis or wavelet transforms, and used to generate compensating currents that are injected back into the system, continuously adjusting to maintain harmonic compensation accuracy
Solution Approach 2:
The patent introduces intermediate processing stages including signal conditioning circuits, digital signal processors, and control algorithms that mediate between raw measurements and final compensation actions, reducing the direct precision demands on individual measurement components
4Object-generated harmful factors
If active filters are used to reduce current harmonics, then harmonic compensation is achieved, but dynamics and response speed are reduced
Solution Approach 1:
The patent employs periodic switching actions at high frequencies (typically 2-20 times the fundamental frequency) to synthesize the compensating currents, allowing rapid response to harmonic changes while maintaining average current control through pulse width modulation techniques
Solution Approach 2:
The patent uses dynamically controllable power electronic switches (IGBTs, MOSFETs) that can change their state rapidly, enabling the active filter to respond quickly to varying harmonic conditions and adjust compensation in real-time without the inertial limitations of passive filter components
Data Source
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AI summary
The invention relates to a method (150), a computer program, and a device (110) for reducing current harmonics, particularly in power electronic converters. The method (150) comprises the following steps: a) supplying an input current ib to a node K, which is connected to an active filter (112), wherein the input current ib comprises a sinusoidal fundamental component ib(1) and a sum of harmonic components ib(n), n ≥ 2; b) determining the amplitude and phase of the sinusoidal fundamental component ib(1) of the input current ib from the time course of the input current ib; c) measuring the time course of a mains voltage vg of an electrical network (120), to which a mains current ig flowing from node K is supplied via a network-side inductance Lg;d) Setting a setpoint for the grid current ig by means of a filter current iaf continuing to flow from node K, wherein the filter current iaf is configured such that a fundamental frequency component ig(1) of the grid current ig corresponds to the sinusoidal fundamental frequency component ib(1) of the input current ib; and e) Providing the grid current ig to the electrical grid (120) via the grid-side inductance Lg, wherein the grid current ig is adjusted by means of a filter voltage vaf provided by the active filter (112), taking into account the grid voltage vg and a grid-side inductance Lg. The invention is particularly suitable for increasing grid stability by providing good current and voltage quality in wind farms (134), solar parks, charging stations for electric vehicles, or grid-connected battery or hydrogen storage systems.