Dynamic Charge Discharge Control for Railcar Power Storage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing power storage devices for electric railcars face inefficiencies in charge/discharge control, leading to regenerative power cancellation and increased energy losses due to unclear charge/discharge characteristics and voltage regulation, which affects the state of charge and overall energy management.
Innovation Solution
A power storage device with a converter, voltage detecting unit, charging rate detection unit, storage unit, and current control unit that sets specific charge and discharge voltages based on detected charging rates, using a table to define control characteristics for efficient charge/discharge operations, thereby optimizing energy storage and retrieval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the charge start voltage is set to a high value (e.g., 1620 V) to ensure the power storage device charges, then the device can absorb regenerative power, but the charge start voltage rises with SOC increase, causing regenerative narrowing and reducing the amount of regenerative power absorbed
Solution Approach 1:
The patent applies dynamics by making the charge start voltage variable rather than fixed. The charge start voltage is dynamically adjusted based on the SOC of the power storage device and the no-load feeding voltage of the rectifier. This dynamic adjustment prevents the voltage from rising excessively with SOC, thereby avoiding regenerative narrowing while ensuring proper charging operation.
Solution Approach 2:
The patent changes the parameter of charge start voltage from a constant value to a variable value that depends on SOC and rectifier operating conditions. By establishing a relationship where the charge start voltage is determined by both the no-load feeding voltage and SOC, the system optimizes regenerative power absorption across different operating states.
2Ease of operation
If the charge/discharge control uses fixed voltage thresholds, then the control is simple, but it cannot adapt to no-load feeding voltage variations and load distribution changes, leading to increased charge/discharge loss
Solution Approach 1:
The patent transforms fixed voltage thresholds into dynamic thresholds that adapt to changing operating conditions. The charge and discharge start voltages are adjusted based on the no-load feeding voltage and SOC, allowing the control system to respond to voltage variations and load changes while maintaining relatively simple control logic.
Solution Approach 2:
The patent implements feedback mechanisms where the charge/discharge control voltages are determined based on the detected no-load feeding voltage and the current SOC state. This feedback loop ensures that the control thresholds adapt to actual system conditions, reducing unnecessary charge/discharge cycles and associated energy losses.
3Stability of the object's composition
If the power storage device charges at high SOC values, then it can maintain voltage stability, but the regenerative cancellation increases and energy efficiency decreases
Solution Approach 1:
The patent ensures continuous useful action by optimizing the charge/discharge control to maintain voltage stability while avoiding excessive charging at high SOC values. The dynamic voltage thresholds ensure that charging occurs when beneficial and stops when SOC is sufficient, preventing unnecessary charge/discharge cycles that would cause regenerative cancellation.
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 improves charge/discharge efficiency, suppresses regenerative cancellation, and maintains the state of charge within a predetermined range, reducing energy losses and enabling efficient energy management during load changes and power supply variations.
Implementation Method 1
a converter (42) which converts voltage between a direct-current power supply system and the power storage element (43)
Data Source
Figure 1
Figure 2~3
AI summary
A power storage device of an embodiment has a power storage element, a table, and a current control unit. A charge characteristic in which any one or more of a first voltage in which charge is started and a second voltage in which charge is started with a maximum current are represented and a discharge characteristic in which any one or more of a third voltage in which discharge is started and a fourth voltage in which discharge is started with a maximum current are represented are defined in sectional ranges of a charging rate in which a charging rate indicating a range of an amount of charge in which the power storage element is capable of storing power is divided into some sections in the table. The current control unit selects a characteristic according to a detected charging rate of the power storage element from the table, sets each voltage of a selected characteristic at a control point of a charge/discharge control characteristic for charging and discharging to/from the power storage element, and performs charge and discharge between a direct-current power supply system and the power storage element through a converter according to a voltage of the direct-current power supply system in accordance with the charge/discharge control characteristic.