HK1159591B - Elevator and building power system with secondary power supply management - Google Patents

Description

Elevator and building power system with secondary power management

Technical Field

The present invention relates to power systems. More particularly, the present invention relates to power systems for managing power from a secondary power source to elevator and building electrical systems.

Background

Elevator drive systems are typically designed to operate over a specific input voltage range from the power source. The components of the drive have voltage and current ratings that allow the drive to continue to operate while the power supply remains within a specified input voltage range. However, utility grids are less reliable in certain markets, and utility voltage sags, voltage surges, local temporary limit power conditions (i.e., voltage conditions below the allowable band of the drive), and/or power loss conditions are common.

When a power dip or loss occurs, the elevator may become stopped in the elevator hoistway between floors until the power source returns to the nominal operating voltage range. In conventional systems, passengers in an elevator may become trapped until a maintenance worker can release the brake for controlling the cab to move up or down to allow the elevator to move to the nearest floor. More recently, elevator systems employing automatic rescue operation have been introduced. These elevator systems include an electrical energy storage device that is controlled to provide power to move the elevator to the next floor to land passengers after a power failure. However, many current automatic rescue operation systems are complex and expensive to implement, and may provide unreliable power to the elevator drive after a power failure. In addition, these systems often fail to provide power to building lighting and control systems, communication systems, and heating, ventilation, and air conditioning systems required for basic rescue or evacuation capabilities.

Disclosure of Invention

The present invention relates to a system for managing power from a secondary power source to supply power to elevator and building systems after a failure of a primary power source. The available power monitor provides an indication of power available from the secondary power source. A demand monitoring system generates a signal relating to the passenger demand of each elevator in the elevator system. The controller then prioritizes the distribution of power from the secondary power source to the elevator and building systems based on the power available from the secondary power source and the passenger demand in the elevator system.

Drawings

Fig. 1 is a schematic diagram of a power system for driving an elevator and building electrical systems during normal and power failure conditions.

Fig. 2 is a flow chart of a process for managing power from a secondary power source to supply power to an elevator and building electrical system after a power failure.

Detailed Description

Fig. 1 is a schematic diagram of power system 10 for driving hoist motor 12 of elevator 14, elevator electrical system 16, and building electrical system 18. The elevator electrical system 16 may include, for example, an elevator lighting and control electrical system. A heating, ventilation, and air conditioning (HVAC) system 18a, a building communication system 18b (e.g., high volume speakers), and a building information display system 18c are shown as examples of the building electrical system 18. Power system 10 also includes a primary power source 20, a power converter 22, a power bus 24, a smoothing capacitor 26, a power inverter 28, a power failure sensor 29, a secondary power source 30, an available power monitor 32, a control block 34, a destination entry system 36, a destination entry input device 37a, a video sensor 37b, a power converter 38, and switches 39a, 39b, 39c, 39d, and 39 e. The primary power source 20 may be a utility grid, such as a utility power source or the like. Secondary power source 30 may be a building backup power source, such as a generator, or a renewable power source, such as a rechargeable battery, that is activated in the event of a failure of primary power source 20. Elevator 14 includes an elevator car 40 and a counterweight 42 that are connected to hoist motor 12 by ropes 44. Load weight sensor 46 is configured to provide a signal related to the weight of the load in elevator car 40 to control block 34.

As will be explained herein, power system 10 is configured to drive hoist motor 12, elevator electrical system 16, and building electrical system 18 when power from main power supply 20 is insufficient. For example, utility grids are less reliable in certain markets, where sustained utility voltage sags or local temporary limit power conditions (i.e., voltage conditions below the allowable band of the drive) are common. The power system 10 according to the invention allows continuous operation of the hoist motor 12, the elevator electrical system 16 and the building electrical system 18 during these irregular periods. After a power failure or during a local temporary limited power condition, power system 10 manages power from secondary power source 30 to provide extended operation of the elevator and building systems.

The power converter 22 and the power inverter 28 are connected by a power bus 24. Smoothing capacitor 26 is connected across power bus 24. The main power supply 20 provides power to a power converter 22. Power converter 22 is a three-phase power inverter operable to convert three-phase AC power from main power source 20 to DC power. In one embodiment, power converter 22 includes a plurality of power transistor circuits including a transistor 50 and a diode 52 connected in parallel. Each transistor 50 may be, for example, an Insulated Gate Bipolar Transistor (IGBT). The controlled electrode (i.e., gate or base) of each transistor 50 is connected to control block 34. Control block 34 controls the power transistor circuits to convert three-phase AC power from main power supply 20 to DC output power. The DC output power is provided by a power converter 22 on a power bus 24. Smoothing capacitor 26 smoothes the rectified power provided by power converter 22 on DC power bus 24. It is important to note that although primary power source 20 and secondary power source 30 are shown as three-phase AC power sources, power system 10 may be adapted to receive power from any type of power source, including, but not limited to, single-phase AC power sources and DC power sources.

The power transistor circuits of power converter 22 also allow power on power bus 24 to be inverted and provided to primary power source 20 and/or secondary power source 30. In one embodiment, control block 34 employs Pulse Width Modulation (PWM) to generate gating pulses to periodically switch transistors 50 of power converter 22 to provide a three-phase AC power signal to main power supply 20. In another embodiment, control block 34 operates transistor 50 to provide DC power to secondary power supply 30. This regenerative configuration reduces the need for primary power source 20 and/or allows for recharging of secondary power source 20.

Power inverter 28 is a three-phase power inverter operable to invert DC power from power bus 24 to three-phase AC power. Power inverter 28 includes a plurality of power transistor circuits including transistors 54 and diodes 56 connected in parallel. Each transistor 54 may be, for example, an Insulated Gate Bipolar Transistor (IGBT). The controlled electrode (i.e., gate or base) of each transistor 54 is connected to control block 34. Control block 34 controls the power transistor circuits to invert the DC power on power bus 24 to three-phase AC output power. The three-phase AC power at the output of power inverter 28 is provided to hoist motor 12. In one embodiment, control block 34 employs PWM to generate gate pulses to periodically switch transistors 54 of power inverter 28 to provide a three-phase AC power signal to hoist motor 12. Control block 34 may vary the speed and direction of movement of elevator 14 by adjusting the frequency and magnitude of the gating pulses to transistors 54.

In addition, the power transistor circuits of power inverter 54 are operable to rectify power generated when elevator 14 drives hoist motor 12. For example, if hoist motor 12 is generating power, control block 34 controls transistors 54 in power inverter 28 to allow the generated power to be converted and provided to DC power bus 24. Smoothing capacitor 26 smoothes the converted power provided by power inverter 28 on power bus 24.

Hoist motor 12 controls the speed and direction of movement between elevator car 40 and counterweight 42. The power required to drive hoist motor 12 varies with the acceleration and direction of elevator 14 and the load in elevator car 40. For example, if elevator car 40 is accelerating, traveling up with a load greater than the weight of counterweight 42 (i.e., a heavy load), or traveling down with a load less than the weight of counterweight 42 (i.e., a light load), a maximum amount of power is required to drive hoist motor 12. If elevator 14 is operating at a fixed speed or leveling (leveling) with a balanced load, it may use a smaller amount of power. If elevator car 40 is decelerating, either down with a heavy load or up with a light load, elevator car 40 drives hoist motor 12. In this case, hoist motor 12 generates three-phase AC power, which is converted to DC power by power inverter 28 under the control of control block 34. The converted DC power may be returned to the primary power source 20, returned to the secondary power source 30, and/or dissipated in dynamic braking resistors connected across the power bus 24.

It should be noted that although a single hoist motor 12 is shown connected to power system 10, power system 10 may be modified to supply power to multiple hoist motors 12. For example, multiple power inverters 28 may be connected in parallel across power bus 24 to provide power to multiple hoist motors 12. Additionally, it should be noted that although the secondary power source is shown connected to one phase of the three-phase input of power converter 22, secondary power source 30 may alternatively be connected to DC power bus 24.

When primary power source 20 is unable to supply sufficient power to drive hoist motor 12, elevator electrical system 16, and building electrical system 18 (e.g., due to a power failure or scheduled or unscheduled local temporary limit power usage, etc.), secondary power source 30 provides power to drive these systems. Power failure sensor 29 senses complete power failure and local temporary limit power usage conditions and signal controller 34, which distributes power from secondary power source 30 to hoist motor 12, elevator electrical system 16, and building electrical system 18.

Fig. 2 is a flow chart of a process for managing power from secondary power source 30 to supply power to hoist motor 12, elevator electrical system 16, and building electrical system 18 and building systems after a failure of primary power source 20. The voltage of the secondary power supply 30 is measured by the voltage sensor 32 (step 60). Signals relating to the power available from secondary power source 30 are provided by available power monitor 32 to control block 34. When the secondary power source 30 is an electrical energy storage system (e.g., a battery or ultracapacitor, etc.), the available power signal may be an estimate of state of charge (SOC) based on one or more of the sensed voltage, the temperature of the secondary power source 30, and the current.

In embodiments where the secondary power source 30 stores mechanical energy (e.g., a flywheel system, etc.), the available power monitor 32 may provide a signal based on the stored mechanical energy. In embodiments where the secondary power source 30 is a fuel-based generator, the signal from the available power monitor 32 may be a function of the remaining fuel.

Control block 34 also determines the passenger demand of each elevator after the power failure to establish the number of passengers using or waiting to use the elevator system (step 62). In some embodiments, control block 34 receives a signal from load weight sensor 46 related to the weight of the load in elevator car 40. Control block 34 may then use the weight measurement to estimate the number of passengers in elevator car 40. The weight measurement can also be used to establish whether there are any passengers in the elevator car 40 when a power failure occurs. Control block 34 may then determine how much power will be needed from secondary power source 30 to service the remaining demand in the elevator system.

In other embodiments, control block 34 receives information from destination entry system 36 relating to the demand of passengers in the elevator system, including the number of passengers in elevator cab 40 and the number of passengers waiting to board elevator cab 40. The destination entry system 36 can serve a single elevator car 40 as shown, but is typically used in conjunction with multiple elevator systems. In the destination entry system 36, passengers enter their desired destination floors on destination entry input devices 37a provided on each floor level in the building. In addition, the video sensor 37b may provide input to the destination entry system 36 of the number of passengers waiting for service at each floor. Each passenger is then assigned to an elevator car 40 that will most efficiently service his or her destination request. Those floors requested by passengers whose elevators are stopped on the assigned elevator, and those floors on which the assigned elevator has committed to take another passenger. Control block 34 may use this assignment information to help determine how much power will be needed from secondary power source 30 to service the remaining demand in the elevator system.

Control block 34 then prioritizes power distribution from secondary power source 30 based on the measured voltage of secondary power source 30 and the passenger demand (step 64). Prioritizing the use of power from the secondary power source 30 allows the elevator and building electrical systems to be powered to efficiently, quickly, and safely service passenger needs or evacuate passengers from the building in an emergency. The electrical systems in power system 10 include hoist motor 12, elevator electrical system 16, HVAC system 18a, building communication system 18b, and building information display system 18 c. Control block 34 may set minimum emergency building functions, such as power to drive hoist motor 12 and minimum lighting in elevator electrical system 16, etc., at a highest priority in the event of a power failure. Control block 34 may set other electrical systems (or their subsystems) at a lower priority level based on their criticality to meeting passenger demand and building safety. These priority levels may be based on the voltage of the secondary power source 30 such that when the energy of the secondary power source 30 is depleted, power is disconnected first from the lowest priority electrical system and the highest priority electrical system is disconnected last. By extending the operation of the elevator electrical system 16, HVAC system 18a, building communication system 18b, and building information display 18c as long as possible, information about the power failure can be more easily communicated to occupants of the building and passengers in the elevator cab 40. This allows the occupants of the building to remain informed and allows more efficient and rapid evacuation of the building in case of an emergency.

Control block 34 may also adjust the power distribution priority level from secondary power source 30 based on the current conditions in the building and elevator system. For example, if the signals from load weight sensor 40 and/or destination entry system 36 indicate that there is a remaining passenger demand to be serviced after a power failure, providing power to hoist motor 12 and elevator electrical system 16 (e.g., elevator lighting, elevator communications, etc.) may take priority over providing power to other systems that are not as critical to servicing the passenger demand, such as HVAC system 18a or building display 18c, etc. After all passenger demands have been serviced, the control block may re-prioritize the distribution priority levels so that the HVAC system 18a, the building communication system 18b, and the building display 18c have a higher priority than the power of the elevator electrical system 16 and hoist motor 12. In this way, prioritization of power distribution in the control block 16 is dynamic, as priority levels may change as building conditions change.

The combination of signals from the load weight sensor 46 and the destination entry system 36 can also be used to ensure that all passenger demands assigned to the elevator car 40 are serviced while efficiently using power from the secondary power source 30. For example, as described above, if elevator car 40 is decelerating, either with a heavy load going down or with a light load going up, elevator car 40 drives hoist motor 12. Control block 34 may thus control the number of passengers assigned to elevator cab 40 via destination entry system 36 to maximize the number of elevator runs, causing hoist motor 12 to regenerate power. This allows power typically dedicated to driving hoist motor 12 to be available to power other elevator and building electrical systems. Thus, control block 34 may re-prioritize building electrical system 18 to a higher priority while the hoist motor is regenerating power. In addition, regenerative power can be converted and returned to the secondary power source 30 to prolong operation of the elevator and building electrical systems after a power failure and to avoid running out of the battery after the point where initiation of additional regenerative operation would be possible.

Control block 34 then distributes power to hoist motor 12, elevator electrical system 16, and building electrical system 18 based on the prioritized power distribution (step 66). In the embodiment shown in fig. 1, control block 34 is configured to provide signals to switches 39a, 39b, 39c, 39d, and 39 e. The switches 39a-39e may be any type of power control device that facilitates a controllable connection between two nodes, including transistors, mechanical switches, or DC/DC converters. Control block 34 controls the state of switches 39a-39e to connect elevator electrical system 16 and building electrical system 18 to secondary power source 30 based on the priority levels of the various systems and the measured voltage of secondary power source 30. The switches 39a-39e may simply turn power on or off, or may be capable of regulating the amount of power delivered. Each switch 39a-39e may be a single switching device or may be multiple devices such that power may be directed to selected individual components or subsystems of elevator electrical system 16 and building electrical system 18.

A suitably sized DC/DC power converter 38 is connected between the secondary power source 30 and each electrical system to step up or step down the voltage from the secondary power source 30 to a level appropriate for the system. For example, if the measured voltage and priority level of secondary power source 30 are such that power is only distributed to hoist motor 12 and elevator electrical system 16, control block 34 closes switches 39a and 39b to connect elevator electrical system 16 to secondary power source 30 and operates converter 22 and inverter 24 to supply three-phase power to hoist motor 12. As another example, if all passenger demands have been serviced, control block 34 may close switches 39a, 39c, 39d, and 39e and open switch 39b to connect secondary power source 30 to building electrical system 18 to facilitate evacuation of the building.

During building evacuation with power outage, empty elevator cars traveling up generate power and cars traveling down with more than 50% payload also generate power. If evacuation can be managed to take advantage of this, the power available from secondary power source 30 can be expanded when compared to random operation with energy production and energy consumption operations, after energy losses are taken into account. Thus, controller 34 may force operation of elevator 14 into a mode in which passengers are encouraged (guided by voice or display associated with destination entry input device 37 a) to transport down and exit the building. Evacuation will start at the top of the building and move downwards. The sensor 37b on the floor near the stop (landing) and the load sensor 46 in the car 40 determine whether the car 40 is empty or light.

The present invention relates generally to systems for managing power from a secondary power source to supply power to elevator and building systems after a failure of a primary power source. An available power monitor determines power available from the secondary power source. A demand monitoring system generates a signal relating to the passenger demand of each elevator in the elevator system. The controller then prioritizes the allocation of power from the secondary power source to the elevator and building systems based on the power available from the secondary power source and the passenger demand in the elevator system. By managing power from the secondary power source, enhanced and prolonged rescue, emergency or evacuation elevator services and capabilities may be provided. In addition, power from the secondary power source can be used to power critical emergency devices outside of the elevator system in the building as well as elevator and building lighting and information displays. These additional capabilities may be crucial to efficiently and effectively serve the remaining passenger needs in the elevator system after a power failure or a local temporary limit of power usage.

Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.

Claims (28)

1. A system for managing power from a secondary power source to power elevator and building systems after a failure of a primary power source, the system comprising:

an available power monitor operable to provide an indication of power available from the secondary power source;

a passenger demand monitoring system operable to generate a signal relating to the passenger demand of each elevator in the elevator system, wherein the signal comprises information about the number of passengers in an elevator car and the number of passengers waiting to board an elevator car; and

a controller configured to prioritize the distribution of power from the secondary power source to the elevator and building systems based on the indication of power available from the secondary power source and the passenger demand in the elevator system such that power of the low priority electrical system of the elevator and building systems is disconnected first as power available from the secondary power source is depleted.

2. The system of claim 1, wherein the passenger demand monitoring system includes a load sensor associated with each elevator operable to measure elevator load weight.

3. The system of claim 2, wherein movement of each elevator is controlled by a hoist motor, and wherein the controller is further configured to allow operation of an elevator if the elevator load weight is sufficient for the hoist motor to regenerate power supplied to the secondary power source.

4. The system of claim 1, the controller minimizing power supplied to the building system from the secondary power source and allocating power to the elevator system to service remaining passenger demand when the indication of power available from the secondary power source is below a threshold.

5. The system of claim 1, wherein the passenger demand monitoring system comprises a destination entry system that tracks passenger demand assigned to each elevator.

6. The system of claim 2, wherein the passenger demand monitoring system provides a signal based on an estimate of passengers waiting on each floor.

7. The system of claim 1, and further comprising:

a plurality of power control devices each connected between the secondary power source and a component of the elevator or building system to control power delivered to the component from the secondary power source, wherein the controller is further operable to control the plurality of power control devices based on an indication of power available from the secondary power source and passenger demand in the elevator system.

8. The system of claim 1, wherein the secondary power source comprises an energy storage system.

9. The system of claim 8, wherein the energy storage system comprises an electrical energy storage system, and wherein the indication of available power comprises a state of charge signal.

10. The system of claim 1, and further comprising:

a passenger alert system for providing status information relating to a power failure.

11. The system of claim 10, wherein the passenger alert system provides instructions to occupants of a building for evacuating the building using an elevator system powered by the secondary power source.

12. A method for managing power from a secondary power source to power elevator and building systems after a failure of a primary power source, the method comprising:

determining power available from the secondary power source;

determining passenger demand for each elevator in the elevator system, wherein the passenger demand includes information about the number of passengers in an elevator car and the number of passengers waiting to board an elevator car;

prioritizing power distribution from the secondary power source to the elevator and building systems based on the determined power available from the secondary power source and passenger demand in the elevator system; and

allocating power to the elevator and building systems based on prioritized power distribution such that power of low priority electrical systems of the elevator and building systems is disconnected first as power available from the secondary power source is depleted.

13. The method of claim 12, wherein determining passenger demand for each elevator comprises measuring elevator load weight for each elevator.

14. The method of claim 13, and further comprising:

allowing an elevator to run if the elevator load weight is sufficient to cause a hoist motor associated with the elevator to regenerate power; and is

Supplying the regenerated electric power to the secondary power source.

15. The method of claim 12, wherein prioritizing power distribution to the elevators and building systems comprises:

determining whether power available from the secondary power source is below a threshold; and

if the power available from the secondary power source is below the threshold, the power supplied to the elevator system is prioritized over the power supplied to the building system to service remaining passenger demand.

16. The method of claim 12, wherein the step of assigning includes controlling power control devices, each connected between the secondary power source and a component of the elevator or building system, based on the prioritized power distribution.

17. The method of claim 12, wherein the secondary power source comprises an electrical energy storage system and determining the available power comprises estimating a state of charge of the electrical energy storage system.

18. A system for managing power from a secondary power source to supply power to elevators and building systems after a failure of a primary power source, wherein the elevator system includes one or more elevators each associated with a hoist motor, the system comprising:

a regenerative drive for delivering power from the secondary power source to the hoist motor;

an available power monitor operable to determine power available from the secondary power source;

a passenger demand monitoring system operable to generate a signal relating to the passenger demand of each elevator in the elevator system, wherein the signal comprises information about the number of passengers in an elevator car and the number of passengers waiting to board an elevator car; and

a controller configured to prioritize the distribution of power from the secondary power source to the elevator and building systems based on the power available from the secondary power source and the passenger demand in the elevator system such that as the power available from the secondary power source is depleted, power is first disconnected for the low priority electrical systems of the elevator and building systems.

19. The system of claim 18, wherein the passenger demand monitoring system includes a load sensor associated with each elevator operable to measure elevator load weight.

20. The system of claim 19, wherein movement of each elevator is controlled by a hoist motor, and wherein the controller is further configured to allow operation of an elevator if the elevator load weight is sufficient for the hoist motor to regenerate power supplied to the secondary power source.

21. The system of claim 18, wherein the controller allocates sufficient power to the one or more hoist motors to service remaining passenger demand when the power available from the secondary power source is below a threshold.

22. The system of claim 18, wherein the passenger demand monitoring system comprises a destination entry system that tracks passenger demand assigned to each elevator.

23. The system of claim 18, and further comprising:

a plurality of power control devices each connected between the secondary power source and a component of the elevator or building system, wherein the controller is further operable to control the plurality of power control devices based on the power available from the secondary power source and the passenger demand in the elevator system.

24. The system of claim 18, wherein the secondary power source comprises an electrical energy storage system.

25. The system of claim 24 wherein the available power monitor generates a state of charge estimate of the electrical energy storage system as a measure of available power.

26. The system of claim 18, and further comprising:

a passenger alert system for providing status information relating to a power failure.

27. The system of claim 26, wherein the passenger alert system provides instructions to occupants of a building for evacuating the building using an elevator system powered by the secondary power source.

28. The system of claim 18, wherein the regenerative drive comprises:

a converter that converts Alternating Current (AC) power from the main power supply to Direct Current (DC) power;

an inverter that drives the hoist motor by converting DC power from the converter into AC power and converts AC power generated by the hoist motor into DC power when the hoist motor generates power; and

a power bus connected between the converter and the inverter to receive DC power from the converter and the inverter.