Bidirectional EV Charging Stations for Battery Charge Balancing
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Solution Overview
Problem
Charging stations with batteries at electric vehicle charging sites face imbalances due to varying usage rates, leading to depletion of batteries in frequently used stations, causing driver frustration and hindering the adoption of electric vehicles.
Innovation Solution
A vehicle charging system with bidirectional inverters and a system controller that enables charge transfers between stations through a local AC circuit or DC bus, balancing energy storage and ensuring reliable power by converting AC to DC and vice versa based on triggering conditions such as battery levels, demand, and disconnection from the power source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If charging stations use local batteries to store energy, then reliability of charging is improved, but charge imbalance between stations worsens due to varying usage rates
Solution Approach 1:
Multiple charging stations are electrically connected through a DC bus, merging their battery systems into a shared energy pool. This allows batteries from different stations to be combined, where stations with excess charge can supply energy to stations with depleted batteries, resolving the charge imbalance problem while maintaining individual station reliability
Solution Approach 2:
A DC bus acts as an intermediary energy transfer medium between charging stations. The bidirectional inverter converts AC power to DC power for battery charging and can also convert DC power from the battery to AC power for supply to other stations, enabling balanced energy distribution across the network
2Device complexity
If charging stations operate independently with local batteries, then device complexity is reduced, but energy utilization efficiency worsens due to idle battery capacity
Solution Approach 1:
Each charging station's battery system serves multiple functions: it can charge local vehicles, supply energy to other charging stations through the DC bus, and receive energy from other stations when depleted. This multi-functionality ensures that battery capacity is fully utilized rather than remaining idle, improving overall energy utilization efficiency
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 solution ensures each charging station has sufficient power by reducing charge imbalances, maintaining reliable charging capabilities, and allowing for efficient energy management, even during peak demand or power source disconnection.
Implementation Method 1
the bidirectional inverter is configured to convert AC power from the one or more AC power ports into DC power to charge the battery and to convert DC power from the battery into AC power to be supplied from the vehicle charging system to the one or more AC power ports
Data Source
AI summary
In order to ensure reliable power for charging electric vehicles is available at each charging station at a charging site having multiple charging stations, the systems and methods disclosed herein provide for charge transfers between batteries of such charging stations. A plurality of charging stations at a charging site are connected via local alternating current (AC) circuit in order to transfer energy between the charging stations, such as to balance the energy stored at the respective batteries of the charging stations. Each charging station includes a system controller controlling operation of the charging station and a bidirectional inverter to convert AC input power from a power grid or the local AC circuit to direct current (DC) power for storage in a battery of the charging station and to convert DC power from the battery to AC output power to the local AC circuit, as controlled by the system controller.