Active Filter Topology for Cascaded Inverter Waveform Control
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Solution Overview
Problem
Existing power inverter systems face challenges in matching a generated alternating voltage waveform to a target waveform, particularly when the generated waveform is staircase-shaped with large amplitude and time steps, leading to unwanted frequency components and inefficiencies.
Innovation Solution
A method and system that utilize a voltage equalizer with an energy storage element to measure and adjust the output waveform, adding or subtracting voltage to match the target waveform, thereby improving the matching and control of the output AC without increasing switching frequency, reducing the need for large passive filters, and allowing operation at lower switching frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If passive filters (inductors and capacitors) are used to reduce unwanted frequency components, then harmonic content is reduced, but device complexity and size increase
Solution Approach 1:
The patent extracts and eliminates the need for large passive filter components by using active control through voltage equalizers. Each switching unit incorporates a voltage equalizer that actively compensates for voltage deviations, removing the requirement for bulky inductors and capacitors that would otherwise be needed to filter harmonics.
Solution Approach 2:
The patent implements feedback control through voltage equalizers in each switching unit. The equalizers continuously monitor voltage deviations from the target waveform and adjust their output accordingly, creating a closed-loop system that actively suppresses harmonics without requiring passive filter components.
2Manufacturing precision
If switching frequency is increased to improve waveform matching, then output waveform quality improves, but switching losses increase
Solution Approach 1:
The patent applies preliminary action by using voltage equalizers to pre-compensate for voltage deviations before they propagate through the system. The equalizers adjust voltages in advance during the switching process, improving waveform matching accuracy without requiring increased switching frequency that would generate excessive losses.
3Manufacturing precision
If voltage equalizers are added to each switching unit, then waveform matching improves, but device complexity increases
Solution Approach 1:
The patent segments the power inverter system into multiple independent switching units, each equipped with its own voltage equalizer. This modular segmentation allows each unit to independently control its output voltage, improving overall waveform matching while distributing the complexity across manageable modules rather than requiring a single complex control system.
Solution Approach 2:
The voltage equalizer circuit is designed as a universal multi-functional component that performs multiple functions: voltage regulation, harmonic suppression, and waveform shaping. By making the equalizer versatile, the patent reduces the need for separate dedicated circuits for each function, thereby managing device complexity while achieving improved waveform matching.
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
The solution enhances the matching of the output AC to the target waveform, reduces switching losses, and allows for a more efficient and compact power inverter system, capable of operating at lower frequencies while maintaining improved waveform quality and reduced harmonic content.
Implementation Method 1
a voltage equaliser having an energy storage element adapted to be charged by the combined output voltage and to add an adjustable voltage to the combined output waveform
Data Source
AI summary
A method for generating a combined output waveform (VOUT) in a power inverter system (100) is disclosed. The power inverter system comprises a voltage equaliser (120) having an energy storage element adapted to be charged by a combined output voltage from a plurality of switching units and to add an adjustable voltage to the combined output waveform. A voltage of the combined output waveform is measured, a difference (Δ) between the measured voltage of the output waveform and a voltage of a target waveform (UT) is determined, and a voltage (UCORR) corresponding to the determined difference is added, by the voltage equaliser, to the combined output waveform so as to improve the matching of the combined output power waveform and the target power waveform.