DC/DC Converter for Elevator Energy Storage
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Solution Overview
Problem
Existing elevator systems face inefficiencies in energy management, particularly in regenerative braking systems, where excess energy generated by motors is often fed back into the power line through braking resistors, and the supply systems are not optimized for low-power single-phase AC voltage sources with high peak motor power requirements.
Innovation Solution
A device utilizing a DC/DC converter independent of the voltage source, which supplies energy to both the energy store and inverter, allowing for efficient energy storage and regulation, eliminating the need for braking resistors and enabling high peak power operation with low supply power, using a rectifier connected via a Schuko connector or sliding line, and featuring an inductance with controllable switches for bidirectional power flow and voltage regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If excess energy generated as a generator is fed back into the line-side voltage source, then the energy is lost, but if a braking resistor is provided, then the device complexity increases
Solution Approach 1:
The system implements a feedback mechanism where the DC/DC converter continuously monitors the state of charge of the energy store and the power generated by generator operation. When excess energy is generated, the converter automatically directs it to charge the energy store instead of feeding it back to the grid or dissipating it through a braking resistor. This closed-loop control eliminates energy loss while avoiding the need for complex braking resistor circuits.
Solution Approach 2:
The energy store serves itself by automatically absorbing excess energy from generator operation without requiring external intervention or additional components. The DC/DC converter enables the energy store to self-regulate its charging state, and when the energy store is full, the system naturally prevents overcharging by stopping the power flow, eliminating the need for braking resistors or complex energy management hardware.
2Device complexity
If the voltage supplying the energy store and inverter is dependent on the voltage supplying the DC/DC converter, then the system is simple, but the intermediate circuit voltage cannot be maintained at high levels with low supply voltage
Solution Approach 1:
The DC/DC converter acts as an intermediary device between the low-voltage single-phase supply and the high-voltage intermediate circuit. It mediates the voltage transformation by using high-frequency switching and electromagnetic induction to step up the voltage from the rectifier output to the required intermediate circuit voltage level. This intermediary function allows the system to maintain high intermediate circuit voltage even when the supply voltage is low, while keeping the overall system architecture relatively simple.
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 solution allows for efficient energy storage and reuse, reducing installation and running costs, increasing system reliability, and eliminating the need for braking resistors, while maintaining high intermediate circuit voltage with low supply voltage, and enabling operation across a wide mains voltage range.
Implementation Method 1
the rectifier can be supplied from a mains-side voltage source
Implementation Method 2
the DC/DC converter is designed and set up in such a way that the rectified mains-side voltage is always or at least temporarily lower than or equal to the voltage occurring on the output side
Implementation Method 3
the DC/DC converter has an inductance which is connected in series with a first controllable switch
Data Source
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AI summary
The invention relates to a device, in particular a machine or plant, and method for operating a device, wherein an energy store and at least one inverter can be supplied in parallel from a DC/DC converter.