PV Combiner Box Arc Prevention via Controllable Switches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional PV string combiner boxes face challenges in safely disconnecting and reconnecting PV strings without damaging internal components, particularly due to undesired current flows and overcurrent or overvoltages, which can lead to arc generation and module damage, especially when only one module in a string is affected.
Innovation Solution
A photovoltaic string combiner box with protection functions, featuring controllable switches, disconnectors, and a controllable network that blocks current flow, along with current and voltage monitoring capabilities, to safely isolate and reconnect PV strings using power electronics and AC circuit breakers, preventing arcs and interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fuses are used to protect PV strings, then short-circuit protection is provided, but modules may be damaged when only one module is affected due to insufficient current to activate the fuse
Solution Approach 1:
The patent divides the PV string into multiple segments with individual controllable switches for each module or module group. This segmentation allows isolated faulty modules to be detected and disconnected independently, enabling protection even when only one module is affected without requiring high fault currents to trigger protection.
Solution Approach 2:
The system performs preliminary monitoring and detection of module conditions before faults escalate. Controllable switches are positioned to enable pre-emptive disconnection of potentially faulty modules, and the system can detect abnormal conditions (such as reverse current or voltage anomalies) before they cause module damage.
2Ease of operation
If disconnectors are used to isolate PV strings, then safe disconnection is achieved, but arc generation may occur during connection/disconnection due to undesired current flow
Solution Approach 1:
The patent introduces controllable switches as intermediary devices between the PV strings and disconnectors. These switches can open the circuit before the disconnector operates, ensuring that no current flows through the disconnector contacts during switching operations, thereby preventing arc generation while maintaining safe disconnection capability.
Solution Approach 2:
The controllable switches perform preliminary circuit opening before the disconnector is actuated. By预先 opening the controllable switches, the system ensures that the disconnector operates on a de-energized circuit, eliminating the risk of arc generation during disconnector operation while preserving the ability to safely isolate PV strings.
3Ease of operation
If PV strings are disconnected for maintenance, then access is enabled, but internal components may be damaged during re-connection due to overcurrent or overvoltages
Solution Approach 1:
Before re-connecting a PV string after maintenance, the system performs preliminary checks and prepares the circuit by closing controllable switches in a controlled sequence. This preliminary action ensures that voltage and current levels are monitored and controlled during the re-connection process, preventing overcurrent or overvoltage damage to internal components while enabling maintenance access.
Data Source
AI summary
A photovoltaic string combiner box with protection functions includes: a plurality of input connections for connecting a plurality of photovoltaic strings to the combiner box, the plurality of input connections respectively including a first input terminal and a second input terminal; an output connection for connecting an inverter to the combiner box; a plurality of current lines, a respective one of the current lines being connected to a respective one of the input connections; a plurality of controllable switches being connected to the plurality of input connections for short-circuiting a respective one of the first and second input terminals; a plurality of disconnectors; a common current line connected to the output connection and having an input node connected to each of the plurality of current lines by a respective one of the disconnectors; and a controllable network arranged in the common current line between the output connection and input node.