Stacked Voltage Source Inverter Segmentation for Grid Reliability
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Solution Overview
Problem
Current solar inverter technologies face inefficiencies due to high cost and low operating frequency, particularly in high voltage applications, leading to suboptimal energy transfer to the grid and increased lifetime costs.
Innovation Solution
A stacked voltage source inverter system utilizing a plurality of full bridge inverters interconnected in series, with local and system controllers to generate sinusoidal voltage waveforms, allowing for high switching frequency and efficient power conversion, and capable of operating in both grid-tied and off-grid applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional central or string inverters are used, then unit efficiency is high (98%), but the system is vulnerable to panel failures and has limited adaptability to partial shading conditions
Solution Approach 1:
The patent divides the inverter system into multiple independent full-bridge inverter modules, each handling a portion of the DC input. This segmentation allows individual modules to operate independently, so that panel failures or shading conditions in one module do not affect the entire system, thereby improving both reliability and adaptability to partial shading.
Solution Approach 2:
The patent implements dynamic control of the inverter modules through phase-shifting techniques and modular activation/deactivation. The system can dynamically adjust the number and configuration of active modules based on operating conditions, enabling adaptation to varying shading patterns and maintaining optimal efficiency across different scenarios.
2Adaptability or versatility
If micro-inverters are used for each solar panel, then adaptability to partial shading is improved, but unit efficiency decreases to 95% or less
Solution Approach 1:
The patent combines multiple full-bridge inverter modules in a stacked configuration where their outputs are series-connected. This merging approach allows the system to achieve micro-inverter-level adaptability to partial shading while maintaining higher efficiency through the inherent efficiency of full-bridge topologies and reduced switching losses compared to traditional micro-inverters.
Solution Approach 2:
The patent employs phase-shifting parameter changes between parallel inverter modules to optimize power transfer and reduce losses. By dynamically adjusting phase angles and operating parameters, the system maintains high efficiency while adapting to varying shading conditions across different modules.
3Power
If high voltage switching components are used for parallel grid application, then power handling capability is improved, but operating frequency decreases due to high switching losses
Solution Approach 1:
The patent segments the high power application into multiple parallel full-bridge inverter modules, each handling a portion of the total power. This segmentation allows each module to operate at higher switching frequencies with lower individual power ratings, reducing switching losses while maintaining overall high power handling capability through the combined output of multiple modules.
Data Source
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AI summary
A stacked voltage source inverter having separate DC sources is described herein. This inverter is applicable to low or medium voltage, low to medium power applications such as photovoltaic utility interface systems, battery storage application such as peak shaving with renewables, motor drive applications and for electric vehicle drive systems. The stacked inverter consists of at least one phase wherein each phase has a plurality of low voltage full bridge inverters equipped with an independent DC source. This inverter develops a near sinusoidal approximation voltage waveform with fast switching and small low pass AC output filter. A system controller controls operating parameters for each inverter. The inverter may have either single]phase or multi]phase embodiments connected in either wye or delta configurations.