Charging Pile Relay Timing for Zero-Voltage Bus Pre-Charge
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Solution Overview
Problem
Conventional charging piles with three-phase AC contactors face space and cost issues due to the need for arc quenching devices to manage impulse currents during pre-charging, leading to bulkiness and increased space occupation.
Innovation Solution
A method and power module that control the closing of relays to pre-charge a bus capacitor when the line voltage is near zero, eliminating the need for arc quenching devices by accurately timing the relay closure to minimize impulse currents, thereby reducing the internal space and cost of the charging pile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-phase AC contactor is used to connect the power module to the mains supply, then the power module can be reliably connected and disconnected, but the contactor requires arc quenching devices to manage impulse currents, increasing its volume and occupying large space in the charging pile
Solution Approach 1:
The patent segments the three-phase power connection into individual phase control. Instead of using a single three-phase AC contactor that switches all phases simultaneously, the invention uses three separate relays (first relay for phase A, second relay for phase B, third relay for phase C) that can be controlled independently. This segmentation allows each relay to be smaller and eliminates the need for a bulky arc quenching device, while maintaining reliable connection and disconnection functionality.
Solution Approach 2:
The patent extracts the arc quenching device from the three-phase AC contactor system. By removing the arc quenching device and using individual relays with controlled closing timing instead, the invention eliminates the source of the volume problem while maintaining the essential function of safe power connection.
2Reliability
If arc quenching devices are provided in the three-phase AC contactor to avoid contact adhesion, then contact reliability is improved, but the volume of the contactor is increased
Solution Approach 1:
The patent extracts the arc quenching device from the system entirely. Instead of including arc quenching devices within the contactor, the invention removes them and replaces the three-phase AC contactor with three individual relays that are controlled to close at specific moments when line voltage is near zero, eliminating the need for arc quenching and the associated volume.
Solution Approach 2:
The patent changes the operating parameters of the relay closing timing. By controlling the relays to close when the line voltage is near zero (a specific parameter condition), the invention prevents impulse currents and contact adhesion without requiring arc quenching devices, thus maintaining reliability while reducing volume.
3Device complexity
If the relays are closed without precise timing control, then the control system is simpler, but impulse currents occur when pre-charging the bus capacitor
Solution Approach 1:
The patent implements feedback control by monitoring the line voltage and using this information to determine the optimal closing moment for the relays. The controller acquires line voltage information and uses it to trigger relay closing only when the voltage is near zero, thereby preventing impulse currents while maintaining manageable system complexity through automated feedback-based timing.
Solution Approach 2:
The patent changes the timing parameter of relay closing from arbitrary or simultaneous closure to precise timing based on line voltage conditions. By controlling the closing moment to occur when line voltage is near zero, the invention eliminates impulse currents during bus capacitor pre-charging while keeping the control system sufficiently simple through automated voltage-based triggering.
Data Source
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AI summary
A charging pile, a power module, and a method for controlling the same. In response to receiving a signal of operation, samples of an input voltage of three relays corresponding to three phases, respectively, at an input of a power module are acquired to determine whether a line voltage between inputs of two of the three relays is within a predetermined voltage range. The two relays are closed to pre-charge a bus capacitor in a converting circuity of the power module, in response to determining that the line voltage is within the predetermined voltage range. The predetermined voltage range comprises zero voltage, such that each relay can be closed when a voltage at its input is close to zero. An impulse current is decreased without help of an arc quenching device, thereby saving an internal space of the charging pile.