DC-DC Converter Droop Control and Initial Charging
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Solution Overview
Problem
Energy storage systems face challenges in initial charging of DC links without separate configurations, reduced power conversion efficiency below predetermined output ratios, inability to operate without battery replacement when discharged, and limitations in droop control due to communication delays.
Innovation Solution
A power supply system incorporating a DC/DC converter with a switch between the DC link capacitor and battery, capable of providing current for initial charging, maintaining high power conversion efficiency, and operating without battery replacement, along with droop control that does not require separate communication lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If initial charging power is supplied from power generation device or system, then DC link voltage can be charged, but system complexity increases and reliability decreases when power generation is unavailable
Solution Approach 1:
The DC/DC converter is designed to perform multiple functions: it serves as both the power conversion device during normal operation and the initial charging device for the DC link. By integrating the initial charging function into the existing DC/DC converter, the patent eliminates the need for separate initial charging configurations while maintaining reliable DC link voltage charging capability regardless of power generation availability.
Solution Approach 2:
The DC/DC converter utilizes the battery's stored energy to charge the DC link capacitor during initial charging operations. This self-service mechanism allows the system to bootstrap its operation without requiring external power generation or separate charging infrastructure, thereby improving reliability while reducing system complexity.
2Productivity
If DC/DC converter operates below predetermined output power ratio, then power conversion efficiency drastically decreases
Solution Approach 1:
The system performs preliminary action by charging the DC link capacitor to the required operating voltage before the battery begins discharging through the DC/DC converter. This preliminary charging ensures that when power conversion starts, the DC/DC converter operates within its efficient power ratio range, avoiding efficiency degradation that would occur at low output power ratios.
Solution Approach 2:
The patent changes the operating parameters of the DC/DC converter by ensuring it operates above a predetermined output power ratio threshold. Through coordinated control of the DC link voltage and converter switching parameters, the system maintains the converter in its high-efficiency operating region, preventing the drastic efficiency decrease that occurs below the threshold power ratio.
3Ease of operation
If battery is completely discharged, then DC/DC converter cannot operate requiring battery replacement
Solution Approach 1:
The system performs preliminary action by charging the DC link capacitor before battery discharge begins. This stored energy in the DC link acts as a buffer that allows the DC/DC converter to continue operating even when the battery becomes completely discharged or over-discharged, eliminating the need for battery replacement and ensuring continuous converter operation.
Solution Approach 2:
The DC link capacitor serves as a cushioning energy reservoir that protects the DC/DC converter from battery discharge limitations. By having this energy buffer in place beforehand, the system can maintain converter operation continuity even when the battery reaches its discharge limits, thereby improving ease of operation and reliability without requiring battery replacement.
4Stability of the object's composition
If droop control uses communication line with BMS, then stability improves, but feedback speed decreases due to communication delay
Solution Approach 1:
The patent extracts the droop control function from the battery management system and implements it directly within the DC/DC converter control unit. This eliminates the communication line and associated delays, allowing the converter to perform fast local feedback control while maintaining charging and discharging stability through the inherent droop characteristic.
Solution Approach 2:
The DC/DC converter performs droop control autonomously using its own control unit, without requiring external communication with the BMS. This self-service implementation of droop control eliminates communication delays while maintaining stability, as the converter can immediately respond to changes in DC link voltage and adjust its operation accordingly.
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
Enables fast initial charging, high energy efficiency during charging and discharging, and quick mode determination for battery operations, eliminating the need for battery replacement and communication lines for droop control.
Implementation Method 1
a DC/DC converter for providing a current to a DC link capacitor before a discharging operation of a battery is started, so as to charge a voltage of the DC link capacitor up to an operating voltage of an inverter
Data Source
AI summary
A DC-DC converter including a bridge circuit unit electrically connected to a DC link capacitor and comprising at least one full bridge circuit comprising switching elements; a sensing unit for sensing a voltage between the bridge circuit unit and the DC link capacitor; and a control unit for controlling the bridge circuit unit according to the sensed voltage, wherein a power of one end of a battery is controlled to a droop curve-shaped power value according to the sensed voltage, wherein the DC-DC converter further comprises an inductor and a capacitor electrically connected to the bridge circuit unit, the inductor is connected to one end of a battery, the capacitor is connected to one end of the battery and a node on the other end of the battery, and the node is connected to and arranged between the inductor and the battery.