Diode-Based Energy Storage Coupling for DC Network Stability
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Solution Overview
Problem
Significant voltage drops can occur in track-side DC networks with limited energy feed-in capacity, and it is not always desirable for energy to be fed back into the DC voltage network on the vehicle side, posing challenges for efficient energy management in DC-powered vehicles operating on such networks.
Innovation Solution
A DC-powered vehicle is equipped with a diode connected between the electrical energy storage device and the current collector, allowing charging from the DC voltage network when the network voltage exceeds the storage voltage and blocking discharge when the network voltage falls below, ensuring automatic coupling and decoupling based on the network status, along with a switch for optional energy feedback when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the energy storage device is directly connected to the DC network without a diode, then energy feedback into the DC network is enabled when the storage voltage exceeds the network voltage, but uncontrolled discharge into the network occurs causing voltage instability and potential damage
Solution Approach 1:
A diode is introduced as an intermediary component between the energy storage device and the DC network. The diode allows current to flow in only one direction (from network to storage device), enabling controlled charging while preventing uncontrolled discharge into the network. This intermediary component resolves the contradiction by selectively permitting energy flow based on voltage conditions.
Solution Approach 2:
The harmful reverse current flow path is extracted from the system by using the diode's inherent unidirectional property. The diode effectively removes the possibility of discharge current flowing back into the network, separating the charging function from any potential discharge function.
2Reliability
If a diode is connected between the energy storage device and the current collector, then automatic coupling and decoupling occurs based on voltage levels, but energy feedback into the DC network is blocked even when needed
Solution Approach 1:
The system transitions from a static connection to a dynamic one where the diode automatically couples or decouples the energy storage device from the DC network based on real-time voltage conditions. When network voltage exceeds storage voltage, the diode conducts (coupled state); when storage voltage exceeds network voltage, the diode blocks (decoupled state). This dynamic behavior enables automatic adaptation to changing operating conditions.
Solution Approach 2:
The diode's conduction state changes based on the voltage parameter comparison between the DC network and the energy storage device. The system automatically adjusts its connectivity state in response to voltage parameter changes, enabling intelligent coupling and decoupling without external control.
3Reliability
If the diode blocks discharge to prevent network voltage drops, then network stability is improved, but the energy storage device cannot provide braking energy feedback when the network is heavily loaded
Solution Approach 1:
The diode acts as a mediator that selectively permits or blocks energy flow based on voltage conditions. During normal operation, it prevents discharge into the network. During braking with high storage voltage, it blocks the reverse flow, but this can be overridden by control switches when energy feedback is needed and beneficial for the network.
Solution Approach 2:
The system incorporates feedback mechanisms where the control device monitors both the energy storage device voltage and the DC network voltage. When the storage voltage exceeds a predetermined minimum feedback voltage and the network voltage is below a threshold or experiencing excessive drop, the control device activates switches to enable energy feedback, creating a closed-loop control system that responds to network conditions.
4Productivity
If switches are added in parallel to the diode to enable controlled energy feedback, then braking energy recovery is improved, but the device complexity increases
Solution Approach 1:
Control switches are added in parallel to the diode, creating a feedback-controlled system. The control device continuously monitors the voltage conditions of both the energy storage device and the DC network, and automatically activates the switches when energy feedback is beneficial (when storage voltage exceeds network voltage by a sufficient margin). This feedback mechanism enables automatic braking energy recovery without requiring manual intervention.
Solution Approach 2:
The control system operates autonomously by monitoring its own voltage conditions and automatically deciding when to enable or disable energy feedback. The system serves itself by making real-time decisions based on its operational state, eliminating the need for external control or manual switching.
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 configuration ensures permanent charging of the energy storage device when its voltage is lower than the network voltage while preventing discharge, and allows for energy feedback to support the network when conditions are favorable, optimizing energy management and network stability.
Implementation Method 1
A diode is connected between an electrical energy storage device and a current collector, in a polarity that automatically allows a charging current flow from the DC network through the diode into the energy storage device
Data Source
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AI summary
The invention relates, among other things, to a direct current-powered vehicle (10) for operation on a trackside direct current network (20) with an internal electrical energy storage device (13, 13a, 13b) which can store braking energy released when the vehicle (10) brakes in the energy storage device (13, 13a, 13b) and make the stored energy available to a traction system (14a, 14b) of the vehicle (10) for propulsion, and a pantograph (11, 11a, 11b) for connection to the trackside direct current network (20).According to the invention, a diode (12, 12a, 12b) is connected between the electrical energy storage device (13, 13a, 13b) and the current collector (11, 11a, 11b), in a polarity that automatically allows a charging current flow from the DC network (20) through the diode (12, 12a, 12b) into the energy storage device (13, 13a, 13b) and charging of the energy storage device (13, 13a, 13b) if the DC voltage (Un) of the DC network (20) exceeds the energy storage voltage (Us), and automatically blocks discharge of the energy storage device (13, 13a, 13b) via the diode (12, 12a, 12b) towards the DC network (20) when the DC voltage (Un) of the DC network (20) the energy storage voltage (Us) falls below a certain threshold.