Sequential PV Subgenerator Disconnection via Semiconductor Mediators
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Solution Overview
Problem
In photovoltaic systems, simultaneous disconnection of multiple PV subgenerators from an inverter can lead to instability and hinder arc localization, as the inertia of electromechanical switches results in prolonged switching durations, potentially causing safety hazards and violating safety standards.
Innovation Solution
Implementing a method that uses semiconductor switches to sequentially disconnect or connect PV subgenerators from the inverter by transferring the switching state from electromechanical switches, allowing for rapid and controlled disconnection or connection, thereby preventing arc formation and enabling quick localization of arcs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electromechanical switches are used to disconnect PV subgenerators, then galvanic isolation is achieved, but switching duration is prolonged due to inertia
Solution Approach 1:
A semiconductor switch is introduced as an intermediary device between the PV subgenerator and the electromechanical switch. The semiconductor switch handles the initial switching operation rapidly, while the electromechanical switch provides reliable galvanic isolation. This mediator approach allows the system to benefit from both the speed of semiconductor switching and the reliability of electromechanical isolation without suffering from the slow switching of the electromechanical switch alone.
Solution Approach 2:
The patent replaces the purely electromechanical switching mechanism with a hybrid system where a semiconductor switch (electronic component) performs the rapid switching operation. This substitution eliminates the mechanical inertia limitations of the electromechanical switch while maintaining the galvanic isolation function through the coordinated operation of both switch types.
2Productivity
If all PV subgenerators are disconnected simultaneously, then disconnection speed is maximized, but arc localization becomes impossible and system instability occurs
Solution Approach 1:
The disconnection process is segmented into individual operations for each PV subgenerator rather than a simultaneous bulk disconnection. The control device manages each switching unit separately, allowing the system to maintain high overall disconnection speed while enabling arc localization by observing which specific subgenerator causes instability or arc formation during the sequential disconnection process.
Solution Approach 2:
The system incorporates feedback mechanisms where the control device monitors the disconnection process and system response. By observing which individual subgenerator disconnection causes system instability or arc formation, the system can identify the location of arcs and adjust the disconnection sequence accordingly, maintaining both speed and diagnostic capability.
3Difficulty of detecting and measuring
If sequential disconnection of PV subgenerators is implemented, then arc localization is enabled, but total switching time increases due to switch inertia
Solution Approach 1:
The semiconductor switch acts as a mediator that performs the rapid switching operation for each PV subgenerator in sequence, while the electromechanical switch provides galvanic isolation. This arrangement enables arc localization through sequential disconnection while minimizing the time penalty by using the fast semiconductor switch for the actual switching operation, reducing the impact of electromechanical switch inertia on total switching time.
4Object-affected harmful factors
If semiconductor switches are used in parallel with electromechanical switches, then arc formation is prevented, but device complexity increases
Solution Approach 1:
The patent merges the semiconductor switch and electromechanical switch into a single integrated switching unit with coordinated control. The control device manages both switch types together, allowing them to work as a unified system where the semiconductor switch handles rapid switching and arc prevention while the electromechanical switch provides reliable isolation. This merging approach reduces overall system complexity compared to having separate, independently controlled switching systems.
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 approach allows for rapid sequential disconnection or connection of PV subgenerators, reducing the risk of arc persistence and enabling efficient arc localization, improving safety and compliance with standards by minimizing switching time and preventing arc-related hazards.
Implementation Method 1
semiconductor switches are often used in parallel with the electromechanical switches. The semiconductor switches bypass the electromechanical switch temporarily during the switching operation and thus prevent the formation of an arc
Implementation Method 2
isolation, under certain circumstances also galvanic isolation or even galvanic isolation at all poles, is generally required between the PV subgenerators and the inverter, which isolation is implemented by an electromechanical switch
Data Source
AI summary
The disclosure relates to methods for sequentially disconnecting at least two electrical current sources from a common load or for sequentially connecting the current sources to a load, wherein the current sources are each connected to the common load via a switching unit, each comprising a parallel circuit comprising an electromechanically actuated switch and an associated semiconductor switch. In the two methods, first semiconductor switches are closed if they are still not closed and the relevant electromechanical switches are opened. In the method for sequential disconnection, then at least two of the semiconductor switches that were actuated or that were already closed are opened sequentially. In the method for sequential connection, a plurality of the semiconductor switches are first opened, of which then at least two are closed sequentially. The disclosure also relates to a photovoltaic system comprising an apparatus that is suitable for implementing the method.