Energy Storage Discharge Using Constant-Power Brake Resistors
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Solution Overview
Problem
Conventional systems for managing energy storage devices in generator-mode operation face challenges in safely dissipating energy and preventing the generation of high voltages, which can lead to system instability and potential damage.
Innovation Solution
A method and system that continuously supplies constant electric power to a resistor until it is fully discharged, using a controllable semiconductor switch and pulse width modulation to manage voltage and power dissipation, while integrating components like DC/DC converters and inverters to control power flow and temperature, ensuring rapid and safe discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional brake resistors are used to reduce energy in generator-mode operation, then high voltages are prevented, but the discharge process is slow and inefficient
Solution Approach 1:
The patent applies dynamic control by continuously adjusting the pulse width modulation ratio as a function of the voltage across the energy storage device. As voltage decreases during discharge, the PWM ratio increases to maintain constant power dissipation, enabling the system to adapt to changing conditions and achieve rapid discharge while maintaining safety
Solution Approach 2:
The patent changes the operational parameters by maintaining constant power P throughout the discharge process rather than using fixed resistance values. This is achieved through continuous adjustment of the PWM duty cycle, allowing the system to operate at optimal power levels across the entire discharge range from initial voltage to near-zero voltage
2Productivity
If high power is supplied to the resistor for rapid discharge, then discharge speed increases, but the resistor temperature rises excessively
Solution Approach 1:
The patent employs periodic pulse width modulation to supply power to the resistor. Instead of continuous power application, the system uses pulsed operation with variable duty cycles, allowing the resistor to dissipate heat between pulses while maintaining high average power for rapid discharge
Solution Approach 2:
The patent maintains continuous power dissipation throughout the discharge process by continuously adjusting the PWM ratio. This ensures that the energy storage device is discharged as rapidly as possible while the cooling system continuously removes heat from the resistor, preventing temperature buildup
3Productivity
If the controllable semiconductor switch is continuously closed for deep discharge, then discharge completeness improves, but voltage control becomes difficult
Solution Approach 1:
The patent implements feedback control by continuously monitoring the voltage across the energy storage device and adjusting the PWM ratio accordingly. The control system uses the measured voltage to determine the appropriate duty cycle, ensuring precise voltage control throughout the discharge process while achieving complete discharge
Solution Approach 2:
The patent uses dynamic PWM control where the duty cycle continuously changes as a function of the instantaneous voltage. This dynamic adjustment allows the system to maintain optimal control across the entire voltage range, from initial high voltage to near-zero voltage, achieving both complete discharge and precise control
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 allows for rapid and safe discharge of energy storage devices, minimizing power supply from the AC network, reducing noise emission, and preventing component damage by dissipating maximum power as heat, even at varying voltages and temperatures.
Implementation Method 1
power is applied to the resistor not only briefly for lowering the intermediate circuit voltage but continuously using the highest possible power P. This power is, e.g., so high that it falls just short of destroying the resistor. Thus, the maximally permissible power is able to be continuously dissipated into the environment in the form of heat.
Data Source
AI summary
In a method and system for operating a system having an energy storage device and a resistor, and in order to discharge the energy storage device, an electric power that is constant over time is continuously supplied to the resistor, e.g., during a time period, e.g., until the resistor has practically been fully discharged, the time period, e.g., being greater than the time constant of the temperature rise of the resistor induced by a continuous electric power that is constant over time and supplied to the resistor.