Hybrid DC Switching Device for Photovoltaic String Isolation
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Solution Overview
Problem
Photovoltaic systems face challenges with high DC string voltages and currents, leading to safety risks during maintenance, and existing solutions like DC main circuit breakers are large, expensive, and lack remote control and selective disconnection capabilities.
Innovation Solution
A hybrid switching device comprising a relay and semiconductor switches, connected in parallel, allows for safe and efficient switching of photovoltaic strings by relieving the semiconductor switches from high currents and using a relay to manage low voltage, enabling cost-effective, reliable, and compact operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DC main circuit breaker is used to disconnect photovoltaic strings, then safety during maintenance is improved, but the device size and cost increase significantly
Solution Approach 1:
The patent divides the photovoltaic system into multiple independently switchable strings, each with its own switching device. This segmentation allows individual string disconnection without requiring a large centralized breaker, reducing overall device size while maintaining safety. Each string can be independently controlled, enabling selective maintenance of specific strings while others remain operational.
Solution Approach 2:
The patent introduces switching devices as intermediary components between the photovoltaic strings and the central collection point. These intermediaries provide the necessary isolation and safety functions, distributing the protective function across multiple smaller units rather than requiring one large breaker, thus reducing device size while maintaining reliability.
2Reliability
If a manually operated DC main circuit breaker is used, then safety isolation is achieved, but remote control capability is lost
Solution Approach 1:
The patent replaces manually operated mechanical circuit breakers with electronically controlled switching devices. These electronic switches can be actuated remotely through control signals, eliminating the need for physical manual operation while maintaining the safety isolation function. The electronic control system enables automated or remote switching operations.
3Area of stationary object
If a single centralized switching device is used for all photovoltaic strings, then installation space is reduced, but selective disconnection of individual strings becomes impossible
Solution Approach 1:
The patent implements segmentation by providing individual switching devices for each photovoltaic string rather than a single centralized switch. This allows selective disconnection of any individual string while maintaining compact installation through standardized modular units. Each switching device is designed to be space-efficient, and the modular approach enables flexible configuration.
Solution Approach 2:
The patent designs universal switching devices that can be applied to any photovoltaic string with standardized characteristics. Each switching device performs multiple functions: isolation, protection, remote control, and selective disconnection. This multi-functionality is achieved through integrated electronic control and switching mechanisms that consolidate what would otherwise require separate components.
4Extent of automation
If motorized emergency switches are used for remote control, then automation is improved, but device size and cost increase
Solution Approach 1:
The patent replaces motorized mechanical emergency switches with solid-state electronic switching devices controlled by electronic signals. This substitution eliminates the need for large motorized mechanisms while achieving the same remote control and automation functions. The electronic switches are significantly smaller and more cost-effective while providing equivalent or superior performance.
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
The solution provides a safe, efficient, and cost-effective method for switching photovoltaic strings, ensuring high safety standards, ease of maintenance, and flexibility during maintenance, while being compatible with existing systems.
Implementation Method 1
a relay (54) and a semiconductor switching device (50), in particular back-to-back connected field effect transistors (MOSFETs) (52), which are connected in parallel to one another
Data Source
AI summary
The present disclosure relates to a photovoltaic system comprising a switching device for switching on and off at least one photovoltaic string, to an electronically controlled direct current hybrid switching device for switching on and off at least one photovoltaic string, in a user-controlled manner, to the use of a hybrid switch for switching a photovoltaic string, and to a method for switching off and back on at least one photovoltaic string of the photovoltaic system. The photovoltaic system comprises:at least one photovoltaic string, wherein the at least one photovoltaic string is formed by photovoltaic modules which are series-connected by means of a string line and thus generate a string voltage;a switching device which is installed in series in the string line to switch on and off the at least one photovoltaic string with the switching device,wherein the switching device comprises a hybrid switch with a relay and a semiconductor switching device which is connected in parallel to the relay and has at least one semiconductor switch.