Solid-State Rapid Shutdown Circuit for PV Arrays

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Solution Overview

Problem

Existing rapid shutdown systems for photovoltaic energy generation systems are expensive, large in size, and prone to failure, making them unsuitable for large-scale implementation, particularly in the context of reducing costs to compete with fossil-fuel-based energy sources, while also failing to effectively disconnect power from photovoltaic arrays during emergencies.

Innovation Solution

A solid-state circuit utilizing high voltage power transistors and a control circuit to rapidly disconnect photovoltaic arrays from power lines, accompanied by a discharge circuit to safely dissipate residual charges, ensuring compliance with safety standards such as 2014 NEC 690.12, which is smaller, cheaper, and more reliable than existing solutions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If electrically controlled switches such as DC contactors or relays are used to effect rapid shutdown, then the shutdown function is achieved, but the devices are relatively expensive, large in size, and prone to failure

Engineering Contradiction:

Improveshutdown reliabilityVSAvoiddevice size and cost

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical DC contactors or relays with solid-state power transistors to achieve rapid shutdown. The solid-state circuit uses electronic switching components instead of mechanical moving parts, eliminating the size, cost, and reliability issues associated with traditional electromagnetic switches while maintaining the rapid shutdown function required by NEC 690.12

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the operational parameters of the switching device by using solid-state transistors that can switch much faster and more reliably than mechanical contactors. The solid-state circuit maintains voltage and power within safe limits (30 volts and 240 volt-amperes within 10 seconds) through electronic control rather than mechanical interruption

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If separate DC shutoff switch is installed between PV power lines and inverter, then safety is improved, but system complexity and cost increase

Engineering Contradiction:

Improveelectric shock riskVSAvoidsystem complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent combines the rapid shutdown function with the existing inverter system by integrating solid-state power transistors into the circuit between the PV array and inverter. This merged approach eliminates the need for separate DC shutoff switches while maintaining safety, as the solid-state circuit performs both power transmission during normal operation and rapid shutdown during emergencies through the same electronic components

Inventive Principle:

Principle #5Merging (Combining)

3Object-affected harmful factors

If rapid shutdown is implemented to meet NEC 690.12 requirements, then safety compliance is achieved, but system cost increases

Engineering Contradiction:

Improvefire fighter safetyVSAvoidsystem cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent employs cost-effective solid-state power transistors and simple control circuitry to achieve rapid shutdown compliance with NEC 690.12. The solid-state circuit uses affordable electronic components rather than expensive mechanical contactors or complex relay systems, making the safety feature economically viable for widespread residential and commercial solar installations

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Data Source

PatentUS9496710B2Rapid shutdown solid state circuit for photovoltaic energy generation systems

Publication Date: 2016.11.15 TESLA INC

AI summary

A solid state circuit for performing rapid shutdown of a photovoltaic power generation system includes a pair of high voltage power transistors connected between a photovoltaic array and a pair of high voltage lines that function to supply power generated by the photovoltaic array to a DC to AC inverter. The solid state circuit further includes a control circuit configured so that when the photovoltaic power generation system operates under normal conditions, the control circuit maintains the pair of high voltage power transistors in the on state so that power produced by the photovoltaic array can be transmitted to the DC to AC inverter through the pair of high voltage lines. The control circuit is further configured so that upon receiving a rapid shutdown command, the control circuit turns off the pair of high voltage power transistors to thereby electrically disconnect the photovoltaic array from the pair of power lines.