15-Level Multilevel Inverter Topology for Low Harmonic Distortion
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Solution Overview
Problem
Conventional multilevel inverters require a large number of switches and DC voltage sources to increase the number of voltage levels, leading to high operational costs and limited useful lifetime due to aging and overheating, while also suffering from high harmonic distortion.
Innovation Solution
A 15-level multilevel inverter design that uses a reduced number of components, including five DC voltage supplies and thirteen unidirectional power switches, employing a Switched Capacitor Based Single Source (SCSS) circuit topology and hybrid modulation to generate 15 output voltage levels with reduced harmonic distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional multilevel inverters increase the number of voltage levels by adding more switches and DC voltage sources, then the approximation of sinusoidal waveforms improves, but the device complexity and operational costs increase
Solution Approach 1:
The patent combines multiple DC voltage sources into a single DC voltage source by using capacitors to generate artificial voltage levels. Instead of requiring multiple independent DC sources, the invention uses one DC source with capacitive energy storage to create multiple voltage levels (±Vdc, ±2Vdc, ±3Vdc, ±4Vdc, 0), thereby reducing system complexity while maintaining 15-level output capability
Solution Approach 2:
The patent introduces capacitors as intermediary energy storage elements between the single DC voltage source and the output terminals. These capacitors act as mediators that store and release energy to generate artificial voltage levels, enabling multilevel output without requiring multiple DC sources or excessive switches
2Object-generated harmful factors
If conventional multilevel inverters increase the number of voltage levels, then harmonic distortion is reduced, but the useful lifetime is limited due to aging and overheating of components
Solution Approach 1:
The patent uses capacitors as energy storage elements that can be easily replaced compared to large DC voltage sources and power switches. The capacitive topology distributes stress across multiple capacitive elements rather than concentrating it in a few critical components, extending system lifetime while maintaining low harmonic distortion through reduced switching frequency
Solution Approach 2:
The patent employs periodic charging and discharging of capacitors to generate the multilevel voltage waveform. By using periodic capacitor discharge to create voltage steps instead of continuous high-frequency switching, the system reduces thermal stress on components, lowering operating temperature and extending useful lifetime while maintaining waveform quality
3Quantity of substance
If conventional multilevel inverters use a large number of switches and DC voltage sources, then more voltage levels are generated, but operational costs increase
Solution Approach 1:
The patent makes a single DC voltage source perform multiple functions by using capacitors to derive multiple voltage levels from it. The same single DC source generates ±Vdc, ±2Vdc, ±3Vdc, ±4Vdc levels through capacitive combination, eliminating the need for multiple independent DC sources and reducing overall system cost
Solution Approach 2:
The patent changes the voltage level parameter by using capacitive voltage division and combination rather than requiring proportional increases in the number of DC sources. The system maintains 15 voltage levels (±4Vdc, ±3Vdc, ±2Vdc, ±Vdc, 0) using a single DC source with capacitors, fundamentally changing how voltage multiplication is achieved and reducing component costs
Data Source
AI summary
A 15-level multilevel inverter circuit includes an outer circuit, an inner circuit, a polarity changing circuit and a computing device. The outer circuit and the inner circuit include a plurality of DC voltage supplies. Each DC voltage supply has a positive and a negative terminal. The outer circuit, the inner circuit and the polarity changing circuit include a plurality of unidirectional power switches. Each unidirectional power switch is a transistor with a diode connected in parallel to the transistor. The computing device is configured to provide control signals to the gates of the plurality of the unidirectional power switches of the outer circuit and the inner circuit to add or subtract the voltage of each of inner DC voltage supplies to form square waveforms approximating sinusoidal waveforms, and to the gates of the plurality of the unidirectional power switches of the polarity changing circuit to switch the polarity of the voltage.