Dynamic Minimum Voltage Control for Electric Motor Braking Energy
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Solution Overview
Problem
Existing energy storage systems, such as capacitors in electric motor inverter systems, face inefficiencies in energy storage and utilization due to voltage limitations, leading to suboptimal energy absorption and efficiency during braking phases, with storage capacity and efficiency being contradictory, and initial voltage requirements hindering maximum power absorption.
Innovation Solution
A method dynamically adjusts the minimum energy storage voltage during braking phases by increasing it when peak voltage is below the maximum permissible voltage and reducing it when exceeded, using factors to increment or decrement the voltage in small or large steps, ensuring efficient energy absorption and storage without exceeding destructive voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the energy store is precharged to a fixed voltage (25-50% of maximum), then the system ensures safe operation and prevents overvoltage damage, but the storage capacity and efficiency cannot be optimized for varying braking conditions
Solution Approach 1:
The patent implements dynamic adjustment of the minimum voltage threshold from a fixed value to a variable parameter that adapts to actual braking conditions. The control unit continuously monitors braking energy and adjusts the minimum voltage accordingly, allowing the system to transition from static to dynamic operation for optimized performance.
Solution Approach 2:
The invention changes the operating parameters of the energy store by dynamically modifying the minimum voltage threshold based on braking conditions. This parameter adjustment enables the system to operate at optimal efficiency points while maintaining safety margins, rather than being constrained by a fixed precharge voltage.
2Loss of energy
If the minimum voltage threshold is increased to improve efficiency in the upper voltage range, then energy storage efficiency improves, but the storage capacity available for braking energy absorption decreases
Solution Approach 1:
The system dynamically adjusts the minimum voltage threshold based on real-time braking conditions rather than using a fixed value. During light braking, a higher minimum voltage maintains efficiency, while during heavy braking, the threshold is lowered to maximize energy absorption capacity.
Solution Approach 2:
The patent allows temporary operation below the normal minimum voltage threshold when braking conditions require maximum energy absorption. This partial relaxation of the voltage constraint enables the system to capture excessive braking energy that would otherwise be lost, then returns to normal operation once the energy is stored.
3Quantity of substance
If the minimum voltage threshold is decreased to increase storage capacity, then more braking energy can be absorbed, but energy storage efficiency decreases due to operation in the lower voltage range
Solution Approach 1:
The control system dynamically determines the appropriate minimum voltage threshold based on the magnitude and duration of braking events. For prolonged light braking, the system operates at higher voltages to maintain efficiency, while for brief heavy braking, it temporarily lowers the threshold to maximize capacity.
Solution Approach 2:
The invention changes the operating parameters by adjusting the minimum voltage threshold in response to varying braking conditions. This adaptive parameter modification allows the system to optimize the trade-off between efficiency and capacity for each specific braking scenario rather than being constrained by a fixed threshold.
4Device complexity
If a fixed minimum voltage is used for the energy store, then the control system is simple and reliable, but it cannot adapt to changing braking behavior and operational conditions
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors braking energy, voltage levels, and operational conditions, then adjusts the minimum voltage threshold accordingly. This closed-loop control enables the system to adapt to changing conditions while maintaining relatively simple implementation.
Solution Approach 2:
The control system automatically adjusts the minimum voltage threshold based on real-time conditions without requiring manual intervention or complex external control. The system serves itself by making adaptive decisions about optimal operating parameters based on the current braking scenario.
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 optimizes energy storage and absorption efficiency by maintaining higher initial power absorption and improved efficiency in the upper voltage range, while minimizing the need for a ballast resistor, thus enhancing the overall energy storage process.
Implementation Method 1
an energy storage device (2) for connection to an intermediate circuit (1.3.1) of an inverter (1.4) and for temporarily storing electrical braking energy from a motor (1.2) operated on the inverter (1.4)
Data Source
Figure 1
Figure 2
Figure 3
AI summary
To optimize the operation of an energy storage device, in particular to optimize the intermediate storage of electrical energy from an electric motor operated by an inverter during the braking phase in an energy storage device, the invention provides a method in which the peak voltage Ucs reached at the energy storage device during a braking phase is determined and recorded, the peak voltage Ucs is compared with the regular permissible maximum voltage of the energy storage device Ucmax, and the minimum voltage of the energy storage device Ucmin, to which it may be discharged in its subsequent discharge phase and from which charging takes place in a subsequent braking phase of the electric motor, is increased if the peak voltage at the energy storage device Ucs is equal to or less than the regular permissible maximum voltage of the energy storage device Ucmax.