Current Distribution Control for Electric Construction Machines
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Solution Overview
Problem
Electrically driven construction machines with multiple energy consumers face challenges in dynamically managing current distribution among electric motor devices, as individual demands vary rapidly, and existing systems struggle to prevent battery over-discharge while ensuring efficient power distribution.
Innovation Solution
A method that estimates current demands of multiple electric motor devices and splits available current based on these estimates, using a battery system's available power, while accounting for parasitic current and setting minimum and maximum limits to prevent over-discharge, allowing for dynamic and accurate distribution that meets varying demands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current distribution is dynamically adjusted to meet varying demands of multiple electric motor devices, then power distribution efficiency is improved, but system complexity increases
Solution Approach 1:
The system performs preliminary estimation of current demands for each electric motor device before actual current distribution. By predicting the current requirements in advance based on operational parameters, the control system can proactively allocate power resources, avoiding reactive adjustments and reducing the complexity of real-time control while maintaining high distribution efficiency.
Solution Approach 2:
The patent introduces a control device as an intermediary between the battery system and multiple electric motor devices. This intermediary component centralizes the decision-making process for current distribution, simplifying the overall system architecture by having a single point of control rather than distributed control across multiple devices, thus improving efficiency without proportionally increasing system complexity.
2Reliability
If minimum current limits are enforced to prevent battery over-discharge, then battery reliability is improved, but available power for motor devices is reduced
Solution Approach 1:
The system dynamically adjusts the minimum current limit threshold based on real-time battery state of charge (SOC) levels. When battery SOC is high, the minimum current limit is relaxed to allow more power availability. When battery SOC drops toward critical levels, the minimum current limit is enforced more strictly to prevent over-discharge. This dynamic adjustment maintains battery reliability while maximizing available power during safe operating conditions.
Solution Approach 2:
The patent changes the parameter of minimum current limit from a fixed value to a variable that depends on battery SOC. By making this parameter adaptive, the system can shift between prioritizing battery protection and prioritizing power availability based on current battery conditions, thus resolving the contradiction between reliability and available power.
3Productivity
If current distribution is optimized for high power delivery, then productivity is improved, but risk of battery over-discharge increases
Solution Approach 1:
The control device continuously monitors battery state of charge (SOC) levels and uses this feedback to adjust current distribution to motor devices. When SOC is high, the system allows higher current delivery to maximize productivity. As SOC decreases toward critical thresholds, the feedback mechanism automatically reduces current allocation and enforces minimum current limits, thereby preventing over-discharge. This closed-loop control optimizes power delivery while maintaining battery protection.
Solution Approach 2:
The system takes preliminary anti-action by establishing minimum current limits and monitoring mechanisms before battery over-discharge can occur. These preventive measures are put in place in advance, allowing the system to maintain high productivity during normal operation while having automatic safeguards ready to activate when battery SOC approaches dangerous levels, thus preventing over-discharge before it happens.
Data Source
AI summary
A method for controlling a current distribution between multiple electric motor devices in a current sharing system of an electrically driven construction machine is described. The method comprises estimating a first current demand for a first electric motor device powered by a battery system and estimating a second current demand for a second electric motor device powered by the battery system. The method comprises determining an available amount of current available in the current sharing system. The method comprises splitting the available amount of current into a first portion for driving the first electric motor device and a second portion for driving the second electric motor device. The splitting is based on the estimations of the first current demand and the second current demand. A control device configured to run the method and to run a current sharing system for an electrically driven construction machine is also described.