Dynamic Voltage Control for DC Railroad Battery Energy Storage
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Solution Overview
Problem
Conventional electric energy storage devices for DC electric railroads face challenges such as increased charging/discharging cycles, reduced reliability due to multiple connected elements, and energy wastage from floating current control, leading to shorter lifetimes and higher costs.
Innovation Solution
An electric energy storage device with a power converter system that dynamically adjusts charging/discharging start and saturated voltages based on line voltage and charging rate, minimizing unnecessary charging/discharging cycles and optimizing energy usage by controlling output currents through a control table and output current controller.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If floating control mode is used to maintain constant charging rate, then charging rate is maintained at arbitrary value, but charging/discharging cycles increase and energy is wasted
Solution Approach 1:
The patent changes the control parameters dynamically by adjusting charging/discharging start and end voltages based on the current charging rate SOC. Instead of maintaining a fixed floating control range, the system adapts the voltage thresholds according to SOC levels, thereby eliminating unnecessary charging/discharging cycles while maintaining accurate charging rate control.
2Power
If multiple electric energy storage elements are connected in series and parallel to achieve high output, then device capacity increases, but reliability decreases due to increased number of monitoring substrates
Solution Approach 1:
The patent divides the electric energy storage device into multiple independent modules, each with its own monitoring substrate. This segmentation allows for localized monitoring and control, reducing the impact of failures in one module on the entire system. The modular architecture improves reliability by isolating faults while maintaining high overall capacity through parallel connection of modules.
3Use of energy by moving object
If deep charging/discharging is performed to maximize energy utilization, then energy efficiency improves, but element lifetime is reduced due to heat and stress
Solution Approach 1:
The patent implements dynamic control of charging/discharging operations by continuously adjusting the start and end voltage thresholds based on the current charging rate SOC. This dynamic approach allows the system to optimize energy utilization by performing deeper charging/discharging when conditions permit, while protecting element lifetime by reducing stress during critical SOC ranges. The control voltages are dynamically modified to balance energy efficiency and element durability.
4Loss of energy
If regenerative inverter is installed to enable power regeneration, then regenerative power can be returned to AC system, but system complexity and cost increase
Solution Approach 1:
The patent enables the electric energy storage device to perform self-service by directly absorbing and storing regenerative power from the DC railroad system without requiring a regenerative inverter. The energy storage device acts as a direct energy buffer, capturing regenerative energy during vehicle deceleration and releasing it during acceleration, thereby eliminating the need for complex AC-side power conversion equipment while achieving effective energy recovery.
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 approach reduces energy wastage, extends the lifespan of the energy storage elements, enhances system reliability, and minimizes feeder system losses by aligning charging/discharging operations with regenerative energy absorption, thereby achieving energy savings and improved efficiency.
Implementation Method 1
an electric energy storage device that absorbs regenerative power of the vehicle is installed in the feeder system
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
Frequent charging/discharging to an electric energy storage element is suppressed to accomplish an energy saving and a longer lifetime. A transmission-line-side power converter device 2 converts power from a transmission line 1, and supplies DC power to a feeder line 3. The feeder line 3 is connected to an electric energy storage element 4 via a power converter device 5. An output current controller 6 is connected with a line voltage detector 7 that detects a line voltage of the feeder line 3, and a charging rate detector 8 that detects a charging rate SOC of the electric energy storage element 4. The output current controller 6 is connected with a control table 9 that sets charging/discharging start voltages and charging/discharging current saturated voltages based on the detected line voltage and charging rate. The control table 9 is provided with a data inputter/outputter 10. The output current controller 6 performs a control in such a manner as to facilitate the electric energy storage element to discharge even at a high line voltage as the charging rate becomes high, and to suppress the electric energy storage element to be charged at the low line voltage. Moreover, the output current controller 6 controls in such a manner as to make the discharging difficult at a low line voltage and to facilitate charging at the low line voltage as the charging rate becomes low.