Dual VFD Elevator Regenerative Energy Routing Without Load Banks
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Solution Overview
Problem
Elevator systems face inefficiencies in managing regenerative electrical power, as existing methods like large resistor load banks are costly and wasteful in absorbing excess energy.
Innovation Solution
An elevator energy management system utilizing two variable frequency drives, where one drive delivers power and receives regenerative energy, and the second drive selectively receives and manages this energy through energy receiving devices such as storage or dissipation components, allowing for controlled distribution and storage or absorption of regenerative power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If large 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:
The patent divides the single VFD into two separate VFDs. The first VFD receives regenerative energy from the elevator machine, and the second VFD selectively receives a controlled amount of that regenerative energy. This segmentation allows for more granular control over energy absorption, preventing the excessive energy loss associated with traditional resistor load banks while managing the complexity through modular drive units.
Solution Approach 2:
The patent changes the operational parameters by introducing selective energy reception. The second VFD can dynamically adjust how much regenerative energy it receives from the first VFD based on system needs. This parameter control enables the system to absorb only the necessary amount of regenerative energy rather than forcing all excess energy through resistors, thereby reducing unnecessary energy loss while maintaining manageable system complexity.
2Loss of energy
If regenerative energy is fed back to the power grid, then energy waste is reduced, but power quality issues and grid stability concerns arise
Solution Approach 1:
The first VFD acts as an intermediary between the elevator machine and the power grid. Instead of directly feeding regenerative energy from the elevator machine to the grid (which causes power quality issues), the energy passes through the first VFD that can buffer, condition, and regulate the energy before it is transferred to the second VFD and ultimately to the grid or load. This intermediary function maintains reliability while enabling energy utilization.
Solution Approach 2:
The patent applies parameter changes by using the VFDs to transform and regulate the electrical parameters of regenerative energy. The VFDs can adjust voltage, frequency, and power factor of the regenerative energy before grid injection, ensuring that the energy is fed back in a form that maintains power quality and grid stability. This allows the system to utilize regenerative energy without compromising reliability.
3Device complexity
If a single VFD handles both motor control and regenerative energy management, then device complexity is reduced, but control precision and energy management flexibility are limited
Solution Approach 1:
The patent segments the energy management function into two distinct VFDs: the first VFD specialized in receiving regenerative energy from the elevator machine, and the second VFD specialized in selectively receiving and managing that regenerative energy. This segmentation provides control precision and flexibility that a single VFD cannot achieve, while the modular nature of using standard VFD units keeps the overall device complexity manageable.
Solution Approach 2:
Each VFD in the system is a universal drive unit that can perform multiple functions. The first VFD can operate as a motor controller and simultaneously as a regenerative energy receiver. The second VFD can selectively receive regenerative energy or operate independently. This multi-functionality allows the system to achieve high adaptability and versatility while using standardized, off-the-shelf VFD components, thereby controlling device complexity.
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, optimizing energy use and reducing waste by allowing for flexible and economical handling of regenerative power within the elevator system.
Implementation Method 1
An elevator machine consumes electrical power to propel the elevator car under certain circumstances. 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.
Implementation Method 2
A second variable frequency drive is configured to selectively receive regenerative energy from the first variable frequency drive during the second operating condition
Implementation Method 3
the at least one energy receiving device comprises at least one energy dissipation component
Data Source
AI summary
An elevator energy management system includes a first variable frequency drive configured to deliver electrical power from a power source to an elevator machine during a first operating condition and to receive regenerative energy from the elevator machine during a second operating condition. A second variable frequency drive is configured to selectively receive regenerative energy from the first variable frequency drive during the second operating condition. At least one energy receiving device is coupled with the second variable frequency drive. The energy receiving device is configured to receive regenerative energy from the second variable frequency drive.