Parallel DC Power Supply Access Control for Insulation Safety
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Solution Overview
Problem
In grid-connected photovoltaic power generation, when the insulation resistance to ground of a direct current power supply is too low, it leads to power generation loss as all connected supplies are forced to stop outputting, causing safety alarms and inefficiencies.
Innovation Solution
An access control method and device that detect individual insulation resistances to ground, disconnecting non-compliant supplies and reconnecting compliant ones to ensure the total insulation resistance meets preset safety conditions, preventing unnecessary shutdowns and maintaining power generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter detects low insulation resistance to ground in one of the parallel direct current power supplies, then safety requirements are met through shutdown, but all direct current power supplies are forced to stop outputting causing power generation loss
Solution Approach 1:
The patent segments the parallel direct current power supply system into individually controllable units. Each direct current power supply is equipped with independent switching devices (contactors or disconnectors) that allow selective disconnection of faulty supplies while maintaining operation of healthy supplies. This segmentation enables the system to isolate insulation resistance problems to specific units rather than forcing a complete system shutdown, thus resolving the contradiction between safety and power generation.
2Object-affected harmful factors
If the inverter stops all output when insulation resistance is too low, then human safety is protected, but efficiency is reduced due to complete shutdown
Solution Approach 1:
The patent extracts the faulty direct current power supply unit from the parallel system by selectively disconnecting only the specific supply with insufficient insulation resistance. The control unit identifies which supply unit has the insulation problem and opens the corresponding switching device, removing only the problematic element from operation. This allows the remaining healthy power supplies to continue generating power, thereby protecting human safety while minimizing energy loss.
3Reliability
If all direct current power supplies are disconnected when one has low insulation resistance, then safety alarm is resolved, but power generation efficiency is reduced
Solution Approach 1:
The patent implements dynamic control of the parallel direct current power supply system through a control unit that continuously monitors insulation resistance and dynamically adjusts the connection status of individual supplies. Based on real-time detection results, the control unit selectively connects or disconnects specific power supply units, optimizing the system configuration to maintain safety compliance while maximizing power generation output at any given moment.
Data Source
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AI summary
The application provides an access control method of parallel direct current power supplies and a device thereof. Direct current power supplies with single insulation resistances to ground failing to meet a first preset condition or causing a total insulation resistances to fail to meet a second preset condition are disconnected from a grid-connected inverter, and direct current power supplies with single insulation resistance to ground meeting the first preset condition and enabling the total insulation resistance to meet the second preset condition are connected with the grid-connected inverter for grid-connected inverting. Unlike in conventional technology, not all the direct current power supplies connected to a direct current bus are made stop outputting, thereby avoiding the loss of inverter power generation.