Battery Pack Heating Film PWM Control for Bus Voltage Fluctuations
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Solution Overview
Problem
Existing battery heating solutions using a heating film and a switching transistor are prone to damage due to excessive operating power caused by voltage fluctuations between the positive and negative direct current buses, leading to potential safety issues and reduced efficiency.
Innovation Solution
A battery pack system with a heating film and a first switching transistor connected in series and parallel between the buses, controlled by a drive circuit to output a pulse signal, with a controller adjusting the duty cycle based on voltage thresholds to manage power, and incorporating a current detection circuit to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the heating film is directly connected to the direct current bus without duty cycle control, then the heating film can operate at full power, but the operating power becomes excessively high when voltage increases, causing damage to the heating film
Solution Approach 1:
The patent applies pulse width modulation (PWM) to dynamically adjust the duty cycle of the switching transistor, transforming the static direct connection into a dynamic controlled connection. The controller adjusts the duty cycle based on voltage levels, making the heating power adaptable rather than fixed, thus resolving the contradiction between maintaining heating effectiveness and preventing excessive power damage
Solution Approach 2:
The patent implements a feedback control mechanism where the controller monitors the voltage between the positive and negative direct current buses and adjusts the duty cycle accordingly. When voltage exceeds a threshold, the controller reduces the duty cycle to limit power; when voltage is within normal range, the controller increases the duty cycle to maximize heating efficiency, creating a closed-loop control system that resolves the power-safety contradiction
2Reliability
If the duty cycle is reduced to limit power when voltage is high, then the heating film safety is improved, but the heating efficiency decreases
Solution Approach 1:
The patent uses dynamic duty cycle adjustment based on real-time voltage conditions. When voltage is high, the duty cycle is reduced to protect the heating film; when voltage returns to normal, the duty cycle is increased to restore heating efficiency. This dynamic adaptation allows the system to temporarily sacrifice efficiency for safety while maintaining high efficiency under normal conditions
Solution Approach 2:
The patent employs periodic pulse signaling with variable duty cycles. Instead of continuous operation, the heating film receives periodic pulses whose width varies based on voltage conditions. This periodic action with adaptive duty cycle allows the system to achieve both safety (by limiting maximum power exposure) and efficiency (by maximizing power delivery when conditions permit)
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
The system effectively controls operating power to prevent damage to the heating film and switching transistor, ensuring safe and efficient heating of the electrochemical cell while adapting to different specifications and scenarios without additional voltage conversion circuits.
Implementation Method 1
An operating principle of the heating film is to convert electric energy into thermal energy based on electrothermal effect, to heat an electrochemical cell
Data Source
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AI summary
This application provides an energy storage system and a heating control method for a battery pack. The energy storage system includes one or more battery packs and a controller. The battery pack includes an electrochemical cell, a heating film, a first switching transistor, and a first drive circuit. The heating film is configured to heat the electrochemical cell. The heating film and the first switching transistor are connected in series, and then connected in parallel between a positive direct current bus and a negative direct current bus. The first drive circuit is configured to output a pulse signal, to drive the first switching transistor to be turned on and turned off. The controller is configured to: if a voltage between the positive direct current bus and the negative direct current bus is greater than a voltage threshold, reduce a duty cycle of the pulse signal, to reduce operating power of the heating film; or if a voltage between the positive direct current bus and the negative direct current bus is less than or equal to a voltage threshold, increase a duty cycle of the pulse signal, to increase operating power of the heating film. According to the solution of this application, excessively high operating power of the heating film can be avoided, so that a risk of damage to the heating film can be reduced.