Patent Application
20240079974
Elevator systems typically include a car that moves vertically between different levels in a building. 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.
While regenerative electrical power is considered desirable to reduce energy consumption, the resulting energy has to be consumed or stored. One approach includes adding large resistor load banks to the power lines to absorb excess energy. Adding such resistors introduces additional cost and results in absorbing more energy than necessary, which is considered wasteful.
An illustrative example embodiment of 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.
In addition to one or more of the features described above, or as an alternative, the second variable frequency drive is configured to communicate with the first variable frequency drive to receive an indication of at least an amount of regenerative energy received by the first variable frequency drive or an amount of regenerative energy to be received by the second variable frequency drive during the second operating condition.
In addition to one or more of the features described above, or as an alternative, the amount of regenerative energy to be received by the second variable frequency drive is less than the amount of regenerative energy received by the first variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the second variable frequency drive controls an amount of regenerative power received by the second variable frequency drive according to the indication of the amount of regenerative energy to be received by the second variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the second variable frequency drive is configured to determine an amount of regenerative energy to be received from the first variable frequency drive during the second operating condition.
In addition to one or more of the features described above, or as an alternative, the at least one energy receiving device comprises an energy storage device configured to receive regenerative energy from the second variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the energy storage device comprises a battery.
In addition to one or more of the features described above, or as an alternative, the energy storage device comprises a flywheel.
In addition to one or more of the features described above, or as an alternative, the at least one energy receiving device comprises at least one energy dissipation component.
In addition to one or more of the features described above, or as an alternative, the at least one energy dissipation component comprises a resistive load.
An illustrative example embodiment of a method of managing energy in an elevator system includes: delivering electrical power from a power source to an elevator machine through a first variable frequency drive during a first operating condition, receiving regenerative energy from the elevator machine at the first variable frequency drive during a second operating condition, receiving at least some of the regenerative energy from the first variable frequency drive at a second variable frequency drive during the second operating condition, and delivering regenerative energy received by the second variable frequency drive to at least one energy receiving device coupled with the second variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the method includes communicating between the first variable frequency drive and the second variable frequency drive to provide the second variable frequency drive an indication of at least an amount of regenerative energy received by the first variable frequency drive or an amount of regenerative energy to be received by the second variable frequency drive during the second operating condition.
In addition to one or more of the features described above, or as an alternative, the method includes controlling the amount of regenerative energy received by the second variable frequency drive to be less than the amount of regenerative energy received by the first variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the method includes controlling an amount of regenerative power received by the second variable frequency drive according to the indication of the amount of regenerative energy to be received by the second variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the second variable frequency drive determines an amount of regenerative energy to be received by the second variable frequency drive from the first variable frequency drive during the second operating condition.
In addition to one or more of the features described above, or as an alternative, the at least one energy receiving device comprises a energy storage device configured to receive regenerative energy from the second variable frequency drive.
In addition to one or more of the features described above, or as an alternative, the energy storage device comprises a battery.
In addition to one or more of the features described above, or as an alternative, the energy storage device comprises a flywheel.
In addition to one or more of the features described above, or as an alternative, the at least one energy receiving device comprises at least one energy dissipation component.
In addition to one or more of the features described above, or as an alternative, the at least one energy dissipation component comprises a resistive load.
The various features and advantages of at least one disclosed example embodiment will become apparent to those skilled in the art from the following detailed description. The drawings that accompany the detailed description can be briefly described as follows.
An elevator machine 30 controls movement of the elevator car 22. The machine 30 includes a motor to propel the elevator car 22 as needed. The machine 30 also includes a brake that holds the elevator car 22 in a selected position, such as at a landing where passengers desire to enter or exit the elevator car 22.
A first variable frequency drive 32 is configured to deliver electrical power to the machine 30 during a first operating condition in which the motor of the machine 30 requires power for moving the elevator car 22. The first variable frequency drive 32 is also configured to receive regenerative energy from the elevator machine 30 during a second operating condition in which the motor of the machine 30 produces regenerative energy.
For example, the second operating condition occurs during movement of the elevator car 22 that results from taking advantage of gravity. One such example second operating condition includes moving the elevator car upward when the car is empty. Under such conditions, gravity pulls the counterweight 26 down resulting in the elevator car 22 moving upward because the mass of the counterweight 26 is greater than the mass of the empty elevator car 22. In a second operating condition that takes advantage of gravity for moving the elevator car 22, the motor of the elevator machine 30 acts as an electrical generator producing regenerative energy. Another example second operating condition occurs when the elevator decelerates and the motor regenerates electricity due to system mass and inertia. The first variable frequency drive 32 receives such regenerative energy from the elevator machine 30 and is configured to deliver it to the associated electrical grid so it can be used to power other loads, for example.
A second variable frequency drive 34 is configured to selectively receive at least some of the regenerative energy from the first variable frequency drive 32 during the second operating condition. The second operating drive 34 is configured to deliver regenerative energy to at least one energy receiving device 36 that is electrically coupled with the second variable frequency drive 34, such as through conventional wiring.
As shown in
The second variable frequency drive 34 selectively receives at least some of the regenerative energy from the first variable frequency drive 32. The second variable frequency drive 34 delivers regenerative energy that it receives to the energy receiving device 36. In the example of
In another example embodiment, the energy receiving device 36 has energy storage capability and includes a rechargeable battery, a flywheel, or a supercapacitor. The second variable frequency drive 34 in such embodiments is configured for bi-directional power flow. The energy stored by the energy receiving device 36 may be provided to other portions of the electrical grid including the first variable frequency drive 32 or other portions of elevator system 20 through the second variable frequency drive 34 under appropriate circumstances.
The amount of regenerative energy received by the second variable frequency drive 34 and delivered to the energy receiving device 36 can be selectively controlled to achieve a desired power balance within the overall system. Some of the regenerative energy received by the first variable frequency drive 32 may be fed back to the power source 38 under appropriate circumstances. For example, when the power source 38 is a utility grid that is capable of receiving energy, at least some of the regenerative energy may be delivered to the power source 38. Another load 40, show schematically in
The first variable frequency drive 32, the second variable frequency drive 34, or both includes control logic, an application specific integrated circuit (ASIC), or a processor for selectively controlling the amount of regenerative energy received by the second variable frequency drive 34. In one example embodiment, the first variable frequency drive 32 tracks or measures the regenerative power received by the first variable frequency drive 32 and communicates with the second variable frequency drive 34 to provide an indication to the second variable frequency drive 34 to receive regenerative power. In some such embodiments, the second variable frequency drive 34 is responsive to the first variable frequency drive 32 and receives regenerative energy until the first variable frequency drive 32 provides an indication to stop receiving such energy. In other example embodiments, the second variable frequency drive 34 is configured to determine when to receive regenerative energy and how much regenerative energy to receive.
The second variable frequency drive 34 adjusts an amount of regenerative energy that is otherwise within the system to be absorbed by the load 40, the power source 38, or both. Real time communications between the first variable frequency drive 32 and the second variable frequency drive 34 allows for managing where the regenerative energy in the system is delivered to accommodate a variety of second operating conditions and varying amounts of regenerative power produced by the motor of the elevator machine 30.
A one-to-one relationship between the variable frequency drives and an elevator is illustrated and described above for discussion purposes. Other embodiments include drives configured for group control. For example, an embodiment includes a second variable frequency drive 34 configured to receive energy from at least two elevators, which may be in a second operating condition at the same time. Alternatively, group elevator control may be included so that such a second variable frequency drive 34 receives regenerative energy from only one of the elevators at any given time.
The disclosed example embodiment and others like it accommodate the widely varying elevator system power requirements without requiring undesirably expensive resistor load banks to absorb excess energy, for example. An energy management system like that described above accommodates regenerative energy in an effective manner during elevator installation and in situations where there is minimal additional load to which the regenerative energy may otherwise be directed. Controlling the second variable frequency drive 34 to selectively receive regenerative energy from the first variable frequency drive 32 customizes the manner in which regenerative energy is handled within the system in a flexible and economical manner.
The various features of the disclosed example embodiments are not necessarily limited to those embodiments. Other combinations of such features are possible to realize additional or different embodiments.
The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this invention. The scope of legal protection given to this invention can only be determined by studying the following claims.
