Parallel Inverter Filter Assembly for Harmonic and Ripple Cancellation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inverter technologies face limitations in reducing volume, harmonics, and cost while improving efficiency, particularly in applications like UPS and active power filters, with prior topologies requiring large filters and high-voltage IGBTs, leading to inefficiencies and compatibility issues.
Innovation Solution
A multiple inverter system comprising multiple inverter units with three-phase bridges, output inductor modules, and filter assemblies, including notch and damping filters, connected in parallel, which reduces harmonics and increases efficiency by canceling ripple currents and shifting drive signals between units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two-level inverter topology is used, then the structure is simple, but high-voltage IGBTs are required and efficiency is low
Solution Approach 1:
The inverter is divided into multiple independent inverter units (first inverter unit, second inverter unit, etc.), each with its own three-phase bridge circuit. These units work in parallel with phase-shifted drive signals, allowing each unit to operate at optimized switching frequencies and voltages, improving overall efficiency while maintaining structural simplicity.
2Device complexity
If two-level inverter topology is used, then the structure is simple, but switching frequency is low and filter size must be large
Solution Approach 1:
Multiple inverter units operate in parallel with phase-shifted switching frequencies. The segmentation of the inverter into multiple units allows each unit to use smaller individual filters, and the combined output achieves higher effective switching frequency, reducing the total filter volume required.
Solution Approach 2:
The inverter units are driven with periodic phase-shifted square wave signals. By adjusting the phase shift between units, the switching ripple frequencies are distributed across multiple frequencies, allowing smaller filters to effectively attenuate the combined output ripple.
3Object-generated harmful factors
If three-level inverter topology is used, then harmonic output and volume are decreased, but compatibility with three-phase-three-wire and three-phase-four-wire systems is poor
Solution Approach 1:
The multiple inverter unit configuration with parallel connection and phase-shifted drive signals creates a universal topology that can operate in both three-phase-three-wire and three-phase-four-wire systems. The modular structure allows flexible adaptation to different system requirements while maintaining low harmonic output.
4Object-generated harmful factors
If larger filter is designed to reduce switching ripple, then ripple is reduced, but loss increases
Solution Approach 1:
Instead of using one large filter, the system uses multiple smaller filters for each inverter unit. The phase-shifted operation of multiple units causes their ripple currents to partially cancel each other, achieving effective ripple reduction with smaller total filter capacity and lower losses.
Data Source
AI summary
A multiple inverter and an active power filter system are disclosed in the invention, said multiple inverter can decrease the volume and harmonics, increase the efficiency and decrease the cost, and can be applied to various occasions. The technical scheme is: the filter assembly in the multiple inverter is installed at the output inductor of the multiple inverter for filtering the harmonics.