Inverter EMI Filter Switching for Harmonic Distortion Suppression
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Solution Overview
Problem
Conventional methods for suppressing harmonic distortion in alternating current systems, such as adding electrical components, increase hardware costs and affect system reliability with limited effectiveness.
Innovation Solution
An inverter system with a first and second alternating current switch, and a split capacitor disposed between them, which is connected in parallel to the alternating current EMI filter, allowing dynamic adjustment of capacitance values to suppress harmonic distortion by changing the resonant frequency of the alternating current system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If electrical components are added to suppress resonance, then harmonic distortion is reduced, but hardware cost increases and system reliability deteriorates
Solution Approach 1:
The patent applies the dynamics principle by making the capacitance value adjustable through switching between different capacitor configurations. The capacitor can be dynamically reconfigured between series and parallel connections based on operating conditions, allowing the resonance frequency to be adjusted to avoid amplification of harmonic voltages while maintaining system reliability without adding permanent additional components.
Solution Approach 2:
The patent applies parameter changes by varying the capacitance value of the existing capacitor through different switching states. By changing the capacitance parameter, the resonance frequency of the EMI filter is adjusted to avoid coinciding with harmonic voltage frequencies, thereby suppressing harmonic distortion without requiring additional hardware components.
2Object-generated harmful factors
If electrical components are added to suppress resonance, then harmonic distortion is reduced, but hardware cost increases
Solution Approach 1:
The patent applies universality by making the existing capacitor serve multiple functions: it provides EMI filtering capability while also being reconfigurable to suppress resonance. The same capacitor is used for both normal filtering operation and resonance suppression by changing its connection configuration, eliminating the need for separate resonance suppression components and reducing hardware cost.
Solution Approach 2:
The patent uses dynamic reconfiguration of the capacitor through switching devices to achieve resonance suppression without adding permanent hardware. The capacitor can be switched between different configurations (series/parallel connections) to adjust resonance frequency as needed, providing a cost-effective solution that utilizes existing components.
3Device complexity
If the inverter is off-grid and the EMI filter is directly connected to the power grid, then filtering is simplified, but resonance occurs and harmonic voltage is amplified
Solution Approach 1:
The patent applies parameter changes by adjusting the capacitance value of the EMI filter capacitor through different switching configurations. When off-grid, the capacitor can be reconfigured to change the resonance frequency of the filter, ensuring it does not coincide with harmonic voltage frequencies in the power grid, thereby preventing harmonic amplification while maintaining a relatively simple filtering structure.
Solution Approach 2:
The patent applies dynamics by enabling the EMI filter to dynamically adjust its resonance characteristics through switching. The filter can change its capacitance configuration based on operating mode (on-grid/off-grid) to avoid resonance with power grid harmonics, preventing harmful voltage amplification while keeping the filtering structure simple and integrated.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses harmonic distortion without adding additional hardware, maintaining system reliability and reducing costs by dynamically adjusting capacitance values to avoid resonance amplification of harmonic voltages.
Implementation Method 1
a first split capacitor is disposed between the first alternating current switch and the second alternating current switch. When the first alternating current switch is turned off and the second alternating current switch is turned on, the first split capacitor is disconnected from the output port of the alternating current filter, and the first split capacitor is connected to a circuit in which an alternating current system connected to the output port of the alternating current EMI filter is located, to suppress harmonic distortion input into the alternating current system
Implementation Method 2
The capacitors connected in parallel and an inductor of the power grid constitute a resonance circuit to generate a resonance. When the resonance circuit overlaps with a frequency band of a harmonic voltage in the power grid, the harmonic voltage is excessively amplified
Data Source
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AI summary
This application provides an inverter, a power generating system, and a method for suppressing harmonic distortion of an alternating current system. The inverter includes an inverter circuit; an alternating current filter, where an input port of the alternating current filter is connected to an output port of the inverter circuit; an alternating current electromagnetic interference EMI filter; and a first alternating current switch, connected between an output port of the alternating current filter and an input port of the alternating current EMI filter; where the alternating current filter includes a first split capacitor, and the first split capacitor is disposed between the first alternating current switch and the input port of the alternating current EMI filter; and when the first alternating current switch is turned off, the first split capacitor is disconnected from the output port of the alternating current filter, and the first split capacitor is connected to a circuit in which an alternating current system connected to the output port of the alternating current EMI filter is located, to suppress harmonic distortion of the alternating current system. The embodiments of this application can suppress the harmonic distortion of the alternating current system.