Capacitor Voltage Control for Regenerative Energy Recovery
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Solution Overview
Problem
Existing power supply systems for construction machines and industrial vehicles, such as hybrid vehicles and forklifts, face inefficiencies in regenerative energy recovery and battery capacity reduction, particularly with lead batteries that are not suitable for rapid charging and suffer from energy loss during regenerative braking.
Innovation Solution
A power supply system incorporating a chargeable and dischargeable capacitor connected through a DC/DC converter to an electric motor, with a control mechanism that estimates operation patterns to manage energy transfer between the capacitor and battery, allowing efficient recovery of regenerative energy and reducing battery capacity by optimizing capacitor target voltage during power running and regeneration modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a large capacity battery is used to provide sufficient energy for traveling and work operations, then the energy supply capability is improved, but the vehicle weight and system complexity increase
Solution Approach 1:
The power supply system is segmented into two distinct components: a battery for baseline energy supply and a capacitor for peak power delivery. This segmentation allows the battery to be smaller in capacity since the capacitor handles transient high-power demands, thereby reducing overall system weight while maintaining energy supply capability.
Solution Approach 2:
The system dynamically switches between battery and capacitor based on power demand characteristics. The capacitor is engaged during high-power transient events (acceleration, regenerative braking) while the battery provides steady-state power, optimizing the weight-energy tradeoff through dynamic power management.
2Device complexity
If a lead battery is used as the power source, then the system simplicity is maintained, but regenerative energy cannot be recovered efficiently due to unsuitability for rapid charging
Solution Approach 1:
The capacitor serves as an intermediary energy storage device between the lead battery and the regenerative braking process. It accepts rapid regenerative energy input that the battery cannot handle, then transfers energy to the battery at a slower rate, enabling efficient regenerative energy recovery while maintaining system simplicity.
Solution Approach 2:
The system changes the charging rate parameter by introducing the capacitor, which can accept high-rate charging from regenerative braking. This parameter change enables the lead battery to operate within its acceptable charging limits while still recovering regenerative energy through the capacitor-mediated process.
3Device complexity
If regenerative braking is implemented with a lead battery, then the control complexity is reduced, but most regenerative energy is lost and cannot be recovered
Solution Approach 1:
The capacitor acts as a mediator that simplifies the control architecture while enabling effective regenerative energy recovery. The control system only needs to manage capacitor charging/discharging based on simple state conditions, avoiding complex battery management while achieving high energy recovery efficiency through the capacitor's rapid response characteristics.
4Device complexity
If the capacitor voltage is not properly managed during power running and regeneration, then the control simplicity is maintained, but the energy transfer efficiency between capacitor and battery decreases
Solution Approach 1:
The control system incorporates feedback based on capacitor voltage thresholds to manage energy transfer between the capacitor and battery. When capacitor voltage exceeds a predetermined threshold during power running, energy is transferred to the battery. During regeneration, the system determines whether to charge the capacitor or battery based on voltage feedback, maintaining high energy transfer efficiency with relatively simple control logic.
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
The system effectively recovers regenerative energy with high efficiency and decreases the required battery capacity, improving energy utilization and reducing the burden on the battery, thereby enhancing the overall power supply system's efficiency and compactness.
Implementation Method 1
a DC/DC converter (14) connected between the capacitor (13) and the load (36a, 36b)
Implementation Method 2
AC power is supplied from the battery to the motor through an inverter
Implementation Method 3
an attempt to improve efficiency has been made by combining a battery and a capacitor to constitute a power supply system and storing the energy from a load in the capacitor
Data Source
AI summary
A construction machine or industrial vehicle having a power supply system which includes a chargeable and dischargeable capacitor and a feeder circuit connecting a battery and the capacitor to a load capable of power running and regeneration. The capacitor is connected through a DC/DC converter which includes a controller that controls energy charged or discharged by the capacitor through the DC/DC converter to the load. The controller includes a power running/regeneration operation estimater which estimates an operation pattern including a point of change between power running and regeneration modes of the motor, or DC current supplied to an inverter, or control lever information and previously stored operation pattern information, and a capacitor target voltage calculator which controls an output command value of the DC/DC converter according to the estimated operation pattern so that a capacitor target voltage sequentially decreases in power running and sequentially increases in regeneration.