Dual VFD Elevator Drive for Regenerative Energy Routing
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Solution Overview
Problem
Elevator systems face inefficiencies in managing regenerative energy, as existing methods like resistor load banks are costly and wasteful, and existing power systems do not effectively manage regenerative energy without additional load.
Innovation Solution
A dual variable frequency drive system is employed, where the second drive selectively receives and manages regenerative energy from the first drive, directing it to energy storage, dissipation components, or the power grid, with real-time communication between drives for efficient energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If resistor load banks are added to absorb excess regenerative energy, then regenerative energy can be managed, but additional cost is introduced and more energy is absorbed than necessary
Solution Approach 1:
A second variable frequency drive acts as an intermediary to manage regenerative energy from the first drive. The second drive receives regenerative energy, controls the amount to be received, and directs it to appropriate destinations (energy storage devices, dissipation components, or grid), eliminating the need for direct resistor load bank connection and enabling more intelligent energy management
Solution Approach 2:
The system implements feedback control where the second variable frequency drive determines the amount of regenerative energy to be received based on system conditions, and the first drive adjusts its regenerative energy output accordingly. This closed-loop control optimizes energy management by matching supply and demand in real-time
2Loss of energy
If large resistor load banks are added to the power lines, then excess energy can be absorbed, but additional cost and energy waste are introduced
Solution Approach 1:
The second variable frequency drive serves multiple functions: it manages regenerative energy from the first drive, controls motor operation, and directs energy to various destinations (storage, dissipation, or grid). This multi-functional approach eliminates the need for separate resistor load banks while providing more flexible and cost-effective energy management
3Use of energy by moving object
If regenerative energy is fed back to the power bus, then energy consumption is reduced, but existing power systems cannot effectively manage regenerative energy without additional load
Solution Approach 1:
The system dynamically adjusts energy management based on real-time conditions. The second variable frequency drive continuously determines the optimal amount of regenerative energy to receive and directs it to the most appropriate destination (storage when available, dissipation when necessary, or grid when suitable), providing adaptive energy management that responds to changing system conditions
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 system efficiently manages regenerative energy without the need for expensive resistor load banks, allowing for flexible and economical handling of excess energy through storage, dissipation, or utilization in the power grid.
Implementation Method 1
Sometimes the desired movement of the elevator car can be accomplished using gravity and the elevator machine can operate as a generator providing regenerative electrical power
Data Source
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AI summary
An elevator energy management system (20) includes a first variable frequency drive (32) configured to deliver electrical power from a power source to an elevator machine (30) during a first operating condition and to receive regenerative energy from the elevator machine (30) during a second operating condition. A second variable frequency drive (34) is configured to selectively receive regenerative energy from the first variable frequency drive (32) during the second operating condition. At least one energy receiving device (36) is coupled with the second variable frequency drive (34). The energy receiving device (36) is configured to receive regenerative energy from the second variable frequency drive (34).