Three-Phase Charging Pile Circuit for Balanced Single-Phase Loads
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Solution Overview
Problem
Conventional three-phase AC charging piles lack a three-phase balanced power distribution function, leading to three-phase imbalance and increased burden on the AC power grid when used in single-phase charging mode.
Innovation Solution
A three-phase balanced power distribution circuit design using a dual-contact type main relay and power distribution function relays, allowing switching between three-phase and single-phase charging modes based on load balancing algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional three-phase AC charging piles are connected to three-phase power without balanced power distribution, then the charging pile can provide three-phase charging capability, but it causes three-phase imbalance and increased burden on the AC power grid when operating in single-phase mode
Solution Approach 1:
The patent implements dynamic relay switching that adjusts the connection configuration between three-phase power input and single-phase charging output based on real-time power distribution status. The control unit monitors the three-phase power input and dynamically switches between different relay states (K1-K8) to achieve either three-phase balanced charging or single-phase charging with load balancing, thereby adapting to different operating conditions and eliminating three-phase imbalance.
Solution Approach 2:
The patent changes the connection parameters (which phases are connected to which terminals) dynamically through relay switching. By controlling the state of relays K1-K8, the system can switch between different connection configurations: three-phase connection (L1-L3 to charging terminals), single-phase connection (one phase to charging terminal), or balanced power distribution mode, thereby optimizing power distribution based on grid conditions.
2Device complexity
If a three-phase AC charging pile uses fixed single-phase connection, then the circuit design is simple, but it cannot switch between phases and causes three-phase imbalance
Solution Approach 1:
The patent designs a universal relay switching system that can perform multiple functions: three-phase charging, single-phase charging with load balancing, and dynamic phase switching. The same relay circuit (K1-K8) and control unit handle both three-phase and single-phase operating modes, as well as phase switching operations, eliminating the need for separate dedicated circuits for each function.
Solution Approach 2:
The patent introduces dynamic relay switching that enables the charging pile to adaptively change connection configurations based on power distribution needs. The control unit dynamically controls relays K1-K8 to switch between different phase connections, allowing the system to transition from fixed single-phase connection to dynamic multi-mode connection with phase switching capability.
3Adaptability or versatility
If dual-contact type main relay is used for main circuit switching, then both three-phase and single-phase charging modes are supported, but the relay configuration becomes more complex
Solution Approach 1:
The patent segments the relay control into modular functional units: main relays (K1, K2) for primary circuit switching, and power distribution function relays (K3-K8) for phase-specific power distribution. This segmentation allows independent control of main circuit switching and power distribution functions, simplifying the overall control logic despite the multiple relays involved.
Solution Approach 2:
The patent merges the functions of main circuit switching and power distribution into a unified relay control system. The dual-contact main relays (K1, K2) simultaneously handle both main circuit switching and power distribution tasks, reducing the need for separate relay sets and simplifying the overall configuration while supporting both three-phase and single-phase charging modes.
Data Source
AI summary
A design of a three-phase balanced power distribution circuit for a three-phase AC charging pile, relating to the field of electric vehicle charging, which comprises an IT grounding system, a TN grounding system, a power distribution function relay, and a main relay. The IT grounding system is provided with incoming ports L1, L2, and L3, and the TN grounding system is provided with incoming ports N, L1, L2, L3, and PE. The invention is provided with a power distribution function relay and a main relay. The power distribution function relay only has an off-load switching function, so the performance requirements for the relay are lower than those for the main relay. The cost of the relay can be greatly reduced, and the main relay will be used in load switching scenarios, so the performance requirements of the main relay are higher.