Pulsed Coupling Units for Stable Power Supply Branch Voltage
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Solution Overview
Problem
Conventional energy storage systems in electric vehicles and wind turbines face reliability issues due to the series connection of battery cells, where a single cell failure can cause the entire system to fail, leading to potential safety threats and system breakdowns.
Innovation Solution
The method involves activating and bypassing energy storage cells in a pulsed manner using controllable coupling units to adjust the arithmetic mean output voltage, allowing for continuous voltage adjustment and avoiding torque deviations in electrical machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If multiple battery cells are connected in series to achieve high output voltage, then the voltage requirement is met, but the system reliability deteriorates because a single cell failure causes complete system failure
Solution Approach 1:
The battery system is divided into multiple independent power supply branches, each capable of operating autonomously. Within each branch, battery cells are connected in series to achieve the required voltage. The coupling units enable independent control of each branch, so that a failure in one branch does not propagate to other branches, thus maintaining system reliability while achieving high output voltage through series connection within branches.
Solution Approach 2:
The invention dynamically changes the operating parameters by selectively activating different numbers of power supply branches and adjusting the series connection configuration within branches. This allows the system to adapt to different load requirements and maintain optimal voltage levels while ensuring that sufficient branches remain operational even when some branches fail, thereby resolving the contradiction between voltage requirements and reliability.
2Power
If battery cells are connected in parallel to increase maximum current, then the current capacity is improved, but the device complexity increases due to additional coupling units and control mechanisms
Solution Approach 1:
The coupling units serve multiple functions: they enable series connection of battery cells within branches to achieve high voltage, provide parallel connection capability across branches for increased current capacity, and offer isolation functionality for fault management. This multi-functionality allows the system to achieve high current capacity without proportionally increasing complexity, as the same coupling infrastructure serves multiple purposes.
3Stress or pressure
If the output voltage is adjusted in steps based on the voltage of individual energy storage modules, then the voltage can be controlled, but torque fluctuations occur in electrical machines particularly at low output voltages
Solution Approach 1:
The invention employs pulse-width modulation (PWM) technique where coupling units are switched on and off periodically at high frequency. By controlling the duty cycle of these periodic switching actions, the effective output voltage can be continuously adjusted rather than in discrete steps. This periodic switching smooths the voltage delivery to the electrical machine, eliminating torque fluctuations while maintaining precise voltage control capability.
Data Source
Figure 1
Figure 2~3
AI summary
The invention relates to a method for setting a desired output voltage U_Soll in a power supply branch (3-3) of a controllable energy store (2) used for controlling and supplying electric power to an n-phase electric machine (1), where n = 1. The controllable energy store (2) has n parallel power supply branches (3-1, 3-2, 3-3), each of which includes at least two serially connected energy storage modules (4). Each energy storage module comprises at least one electric power cell (5) having an associated controllable coupling unit (6) and is connected to a reference bus (T-) and to one respective phase (U, V, W) of the electric machine (1). At least one coupling unit (6-3m) is triggered by pulses in such a way that the arithmetic mean of the output voltage in a power supply branch (3-3) corresponds to the desired output voltage U_Soll, wherein the power cells (5-3m) associated with the at least one coupling unit (6-3m) are connected to the respective power supply branch (3-3) for the duration of a pulse and are bridged during an interpulse period.