Transformerless Solar Inverter with Common Mode Choke
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current solar inverter technologies rely on isolation transformers for galvanic isolation, which add inefficiencies, complexity, weight, and cost, and are limited to specific installations, lacking a solution for large PV inverters to operate independently of transformers and directly convert to 480VAC three-phase power.
Innovation Solution
A photovoltaic system that includes a DC-AC inverter coupled with damping and trapping circuitry to filter high-frequency voltages and reduce low-frequency currents, allowing direct AC power application to distribution systems without an isolation transformer, utilizing a common mode choke and parallel resonant tank circuits to prevent high-frequency propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolation transformer is used for galvanic isolation in solar inverters, then safety and isolation are improved, but efficiency, complexity, weight, and cost worsen
Solution Approach 1:
The patent removes the isolation transformer from the inverter system entirely, extracting this component to eliminate its associated losses, complexity, weight, and cost while maintaining galvanic isolation through alternative means (utility transformer at the premises level)
Solution Approach 2:
The patent introduces an intermediary approach where the utility transformer at the premises serves as the isolation device rather than an integrally-provided transformer in the inverter, allowing the inverter to operate without its own transformer while still achieving galvanic isolation
2Reliability
If an isolation transformer is integrated with the inverter, then galvanic isolation is achieved, but device complexity and cost increase
Solution Approach 1:
The isolation transformer function is extracted from the inverter unit and relocated to the premises level utility transformer, simplifying the inverter design and reducing its complexity while maintaining the necessary galvanic isolation
3Power
If an isolation transformer is used, then voltage ratio change is achieved, but weight and cost increase
Solution Approach 1:
The voltage ratio transformation function is extracted from the inverter and handled by the utility transformer at the premises, allowing the inverter to be lighter and less costly while still achieving the necessary voltage conversion through the combined system
4Device complexity
If transformerless inverters are used, then inverter complexity is reduced, but adaptability to different installations worsens
Solution Approach 1:
The patent creates a universal transformerless inverter design that can be deployed across multiple installation types (residential, commercial, industrial, utility-scale) by leveraging the existing utility transformer infrastructure at various premises, making the solution broadly adaptable without requiring inverter-specific transformers
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
This configuration increases efficiency, reduces costs and size, enables multiple inverters to operate without isolation transformers, and allows for flexible placement, while preventing energy losses and heat generation from filtered frequencies.
Implementation Method 1
a common mode choke, a first damping circuit, and a first parallel resonant tank circuit... The first parallel resonant tank circuit is coupled to the common mode choke and is configured to filter a first frequency
Implementation Method 2
a first parallel resonant tank circuit coupled to the common mode choke and configured to filter a first frequency, wherein the first frequency is derived from a switching frequency of the inverter
Implementation Method 3
a first damping circuit coupled to the inverter and configured to damp a second frequency, wherein the second frequency is derived from the switching frequency of the inverter
Data Source
AI summary
A photovoltaic system, method and apparatus are disclosed. In an exemplary embodiment, the system includes a photovoltaic array, a distribution system that distributes power within a premises of a demand-side energy consumer, an inverter coupled to the distribution system that is configured to convert DC power from the photovoltaic array to AC power and apply the AC power to the distribution system, a damping portion configured to damp high frequency voltages derived from the inverter, and trapping circuitry coupled to the damping portion that is configured to reduce a level of low frequency current traveling through the damping portion.