Stacked DC Voltage Source Inverters for Grid Coupling
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Solution Overview
Problem
Conventional micro-inverter technologies for distributed solar panel systems have conversion efficiencies of 95% or less, limiting the efficient coupling of power to the grid in photovoltaic systems.
Innovation Solution
The system employs multiple DC voltage source inverters with full bridge inverter stages, stacked inverter phases, and a system controller for efficient power conversion and synchronization, allowing for scalable, reliable, and efficient AC power generation using a minimal number of wires.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional micro-inverters are used for distributed inversion of solar panel DC sources, then individual panel conversion is enabled, but the conversion efficiency is limited to 95% or less
Solution Approach 1:
The system divides the inverter function into modular full-bridge inverter stages that can be stacked in series. Each stage processes a portion of the total power, allowing the system to achieve higher overall efficiency through optimized individual stage operation while maintaining distributed processing capabilities.
Solution Approach 2:
Multiple full-bridge inverter stages are combined in a stacked configuration where the secondary node of one stage connects to the primary node of the next stage. This merging of stages in series enables the system to exceed the 95% efficiency limitation of conventional single-stage micro-inverters while processing power from multiple solar panels.
2Loss of energy
If multiple full bridge inverter stages are stacked in series, then conversion efficiency increases beyond 95%, but system complexity and control requirements increase
Solution Approach 1:
The system employs dynamic control where a system controller coordinates multiple local controllers across the stacked stages. Each local controller manages its associated full-bridge stage with adjustable switching frequencies and pulse width modulation, allowing the system to adapt to varying power conditions and maintain optimal efficiency across different operating points.
Solution Approach 2:
Local controllers receive feedback signals from their respective full-bridge stages and adjust switching parameters accordingly. The system controller aggregates information from all stages and provides coordinated control signals, creating a feedback loop that optimizes overall system efficiency while managing the complexity of multiple stacked stages.
3Loss of energy
If distributed inverter stages are used, then power conversion efficiency improves, but synchronization and control coordination become more difficult
Solution Approach 1:
The system controller acts as an intermediary between the distributed local controllers and the power grid. It receives synchronization signals from the grid, processes them into coordinated control commands, and distributes these commands to each local controller. This intermediary role simplifies the synchronization task for individual stages while maintaining overall system coordination.
Solution Approach 2:
The system replaces mechanical synchronization methods with electronic signal processing. Synchronization signals are transmitted electronically from the system controller to local controllers via communication interfaces, eliminating the need for complex mechanical timing mechanisms and enabling precise digital control of switching operations across all stages.
4Ease of manufacture
If conventional parallel micro-inverter connections are used, then installation is simplified, but power coupling efficiency to the grid is limited
Solution Approach 1:
The system transitions from parallel connection architecture to a series-stacked architecture, adding a vertical dimension to the inverter stage configuration. This dimensional change allows multiple full-bridge stages to be connected in series, enabling higher voltage operation and improved power coupling efficiency to the grid while maintaining modular scalability for installation flexibility.
Data Source
AI summary
Systems and methods are disclosed with multiple direct current (DC) voltage source inverters to supply power to an alternating current (AC) power system. The system includes a plurality of full bridge inverter stages, each having a primary node and a secondary node, each of said full bridge inverter stages having positive and negative node, each of said full bridge inverter stages having a voltage supporting device electrically connected in a parallel relationship between said positive node and said negative node and a direct current (DC) source connected between the positive and negative nodes; at least one stacked inverter phase, each stacked inverter phase having a plurality of said full bridge inverter stages, each of said full bridge inverter stages in each stacked inverter phase interconnected in a series relationship with said secondary node of one of said full bridge inverter stages connected to said primary node of another full bridge inverter, said series interconnection defining a first full bridge inverter stage and a last full bridge inverter stage, each phase having an input node at said primary node of said first full bridge inverter stage and an output node at said secondary node of said last full bridge inverter stage; a local controller coupled to each full bridge inverter stage providing the control signals to each full bridge inverter stage to output an approximate nearly sinusoidal voltage waveform; and a system controller which communicating with each local controller; the system controller generating system control signals for configuration, synchronization, activation, deactivation and operating mode selection of said local controller.