HK1160434B

HK1160434B - Management of power from multiple sources based on elevator usage patterns

Info

Publication number: HK1160434B
Application number: HK12100853.2A
Authority: HK
Inventors: William A. Veronesi; Stella M. Oggianu
Original assignee: Otis Elevator Company
Filing date: 2008-09-04
Publication date: 2015-10-02

Description

Management of power from multiple sources based on elevator usage patterns

Technical Field

The present invention relates to power systems. More particularly, the invention relates to a system for managing power from multiple sources in an elevator system based on elevator usage patterns.

Background

The power demand for operating an elevator ranges from a positive value, where externally generated power is used (e.g. generated from a power utility), to a negative value, where the load in the elevator drives the motor so that it produces electricity as a generator. The use of an electric motor as a generator to generate electricity is commonly referred to as regeneration. In conventional systems, if the regenerated energy is not provided to another component of the elevator system or returned to the utility grid, it is dissipated through a dynamic braking resistor or other electrical load. In such a configuration, the utility maintains all demand for power to the elevator system even during peak power conditions (e.g., when more than one motor is started simultaneously or during periods of high demand). Accordingly, components of an elevator system that deliver power from a power utility need to be sized to accommodate power demands, which can be more costly and require more space. In addition, the dissipated regenerative energy is not used, thereby reducing the efficiency of the power system.

In addition, elevator drive systems are typically designed to operate at a specific input voltage range of the power supply. The voltage and current ratings of the driven components allow the drive to operate continuously while the power supply remains within a specified input voltage range. In conventional systems, when the utility voltage drops beyond design limits, the elevator system fails. When a utility power failure occurs or under conventional system poor quality conditions, the elevator may stop between floors in the elevator shaft until the power returns to normal operation or a mechanic intervenes.

Disclosure of Invention

The present invention relates to managing energy in an elevator system including an elevator hoist motor, a main power supply, and an energy storage system. The predicted usage pattern of the hoist motor is established based on past hoist motor power demands in the elevator system or elevator systems of similar buildings. The target state of stored energy (or storage state) of the energy storage system is then set according to the predicted usage pattern. The power exchanged between the hoist motor, the main power supply and the energy storage system is controlled to address (address) the power demand of the hoist motor and to maintain the storage state of the energy storage system in the vicinity of the target storage state.

Drawings

Fig. 1 is a schematic diagram of an elevator power system including a controller for managing power from multiple sources.

Fig. 2 is a block diagram of a drive controller for controlling power distribution to components of an elevator system based on a target storage state of an energy storage system.

Fig. 3 is a flow chart of a process for managing power exchanged between a hoist motor, a main power source, and an energy storage system according to a target storage state.

Detailed Description

Fig. 1 is a schematic diagram of a power system 10, the power system 10 including a primary power source 20, a power converter 22, a power bus 24, a smoothing capacitor 26, a power inverter 28, a voltage regulator 30, an electrical or mechanical Energy Storage (ES) system 32, an ES system controller 34, and a drive controller 36. The power converter 22, the DC bus 24, the smoothing capacitor 26, and the power converter 28 are included in the regenerative drive 29. The main power supply 20 may be an electric utility power distribution grid (electric utility grid). The ES system 32 includes a device or devices capable of storing electrical or mechanical energy. Elevator 14 includes an elevator car 40 and a counterweight 42 that are connected to hoist motor 12 by roping 44. Elevator 14 also includes a load sensor 46 connected to drive control 36 for measuring the weight of the load in elevator car 40.

As will be described herein, power system 10 is configured to control the power exchanged between elevator hoist motor 12, main power supply 20, and/or ES system 32 in order to address the power demand of hoist motor 12 and maintain the storage state of ES system 32 near a target level. The target storage state is set based on the usage pattern of elevator hoist motor 12 and other factors such as specifications for minimum and maximum grid usage. The usage pattern may be established by hoist motor power demand during previous use of power system 10, by hoist motor power demand in an elevator system of a similar building, or a combination of both. For example, when the power demand of elevator hoist motor 12 is positive, power system 10 drives hoist motor 12 from main power supply 20 and ES system 32 at a rate that maintains the storage state of ES system 32 near the target level. As another example, when the power demand of elevator hoist motor 12 is negative, power system 10 provides power generated by elevator hoist motor 12 to power source 20 and ES system 32 at a rate that increases the storage state of ES system 32 back to near the target storage state. The ratio of power provided by the ES system 32 or returned to the ES system 32 may be a function of the proximity of the storage state of the ES system 32 to the target storage state. Power system 10 also controls the distribution of power between main power supply 20 and ES system 32 when the power demand of elevator hoist motor 12 is near zero and between ES system 32 and elevator hoist motor 12 in the event of a failure of main power supply 20.

Power converter 22 and power converter 28 are connected by DC bus 24. A smoothing capacitor 26 is connected across the DC bus 24 (connected across DC bus 24). The main power supply 20 provides power to a power converter 22. Power converter 22 is a three-phase power converter operable to convert three-phase AC power from primary power source 20 to DC power. In one embodiment, power converter 22 includes a plurality of power transistor circuits including parallel connected transistor 50 and diode 52. Each transistor 50 may be, for example, an Insulated Gate Bipolar Transistor (IGBT). The control electrode (i.e., gate or base) of each transistor 50 is connected to the drive controller 36. Drive controller 36 controls the power transistor circuit to convert the three-phase AC power from main power supply 20 to DC output power. The DC output power is provided by the power converter 22 on the DC bus 24. Smoothing capacitor 26 smoothes the rectified power provided by power converter 22 on DC bus 24. It is important to note that while primary power source 20 is shown as a three-phase AC power source, power system 10 may be adapted to receive power from any type of power source, including, but not limited to, a single-phase AC power source and a DC power source.

The power transistor circuitry of power converter 22 also allows the power on DC bus 24 to be converted (inverted) and provided to primary power supply 20. In one embodiment, drive controller 36 employs Pulse Width Modulation (PWM) to generate gate pulses to periodically switch transistor 50 of power converter 22 to provide a three-phase AC power signal to main power supply 20. This regenerative configuration, along with other loads on main power supply 20, reduces the demand on main power supply 20.

Power converter 28 is a three-phase power converter operable to convert DC power from DC bus 24 to three-phase AC power. Power converter 28 includes a plurality of power transistor circuits including parallel connected transistor 54 and diode 56. Each transistor 54 may be, for example, an Insulated Gate Bipolar Transistor (IGBT). The control electrode (i.e., gate or base) of each transistor 54 is connected to a drive controller 36, which drive controller 36 controls the power transistor circuit to convert the DC power on the DC bus 24 to three-phase AC output power. Three-phase AC power at the output of power converter 28 is provided to hoist motor 12. In one embodiment, drive controller 36 employs PWM to generate gate pulses to periodically switch transistors 54 of power converter 28 to provide a three-phase AC power signal to hoist motor 12. Drive controller 36 may vary the speed and direction of movement of elevator 14 by adjusting the frequency and duration of the gating pulses to transistor 54.

Additionally, the power transistor circuitry of power converter 54 is operable to rectify power generated when elevator 14 drives hoist motor 12. For example, if hoist motor 12 is generating power, drive controller 36 controls transistor 54 of power converter 28 to allow the generated power to be converted and provided to DC bus 24. Smoothing capacitor 26 smoothes the converted power provided by power converter 28 on DC bus 24. The regenerated power on DC bus 24 may be used to recharge storage elements of ES system 32, may be returned to main power supply 20 as described above, or may be dissipated in a dynamic braking resistor (not shown).

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 the elevator car 40 is being accelerated, traveling up with a load greater than the weight of the counterweight 42 (i.e., a heavy load), or traveling down with a load less than the weight of the counterweight 42 (i.e., a light load), a maximum amount of power is required to drive the hoist motor 12. In this case, the power demand of the hoist motor 12 is a positive value. If the elevator car 40 travels down with a heavy load or travels up with a light load, the elevator car 40 drives the hoist motor 12, thereby regenerating energy. In this case of negative power demand, hoist motor 12 generates three-phase AC power that is converted to DC power by power converter 28 under the control of drive controller 36. As described above, the converted DC power may be returned to primary power supply 20 for recharging ES system 32 and/or dissipated in dynamic braking resistors connected across DC bus 24. Elevator 14 may use a smaller amount of power if it is leveling or traveling at a fixed speed with a balanced load. If hoist motor 12 is neither motoring nor generating power (i.e., idle), the power requirements of hoist motor 12 are near zero.

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 power multiple hoist motors 12. For example, multiple power converters 28 may be connected in parallel across DC bus 24 to provide power to multiple hoist motors 12. Additionally, although ES system 32 is shown connected to DC bus 24, ES system 32 may alternatively be connected to one phase of the three-phase input of power converter 22.

The ES system 32 may include one or more devices in series or parallel that are capable of storing electrical energy. When the ES system 32 stores electrical energy, the storage state may be referred to as a state-of-charge (SOC). In some embodiments, the ES system 32 includes at least one ultracapacitor, which may include symmetric or asymmetric ultracapacitors. In other embodiments, the ES system 32 includes at least one auxiliary or rechargeable battery, which may include any of the following: nickel cadmium (NiCd), lead acid, nickel metal hydride (NiMH), lithium ion (Li-ion), lithium ion polymer (Li-Poly), iron electrode, nickel zinc, zinc dioxide/alkali/manganese, zinc bromine flow, vanadium flow, and sodium sulfur battery.

In other embodiments, the ES system 32 is a mechanical energy storage system. For example, a mechanical device such as a flywheel may be used to store kinetic energy.

Fig. 2 is a block diagram of the drive controller 36 connected to the regenerative drive 29 and the ES system controller 34. The drive controller 36 includes a processor 60, a data storage module 62, and a hoist motor operation module 64. The drive controller 36 may also include other components not specifically shown in fig. 2. The hoist motor operation module 64 provides input to the data storage device module 62, and the data storage device module 62 provides input to the processor 60. Based on input from the data storage module 62, the processor 60 generates signals that control the operation of the regenerative drive 29 and the ES system controller 34.

Fig. 3 is a flow chart of a process for managing the power exchanged between elevator hoist motor 12, main power supply 20, and ES system 32 based on a target storage state. In this example, the ES system 32 stores electrical energy, and the storage state is a state of charge (SOC). The predicted usage pattern is first established (step 70) based on a forecast hoist motor demand (forecast), which may include past or predicted demand or a combination of both. Hoist motor operation module 64 monitors usage characteristics of elevator hoist motor 12 and stores data related to these usage characteristics in data storage device module 62. In some embodiments, the usage characteristics include the time between each run of elevator hoist motor 12 and the power requirements of each run. The usage characteristics may also include information such as the number of passengers transferred during each run, the load in the elevator car 40 (as measured by the load sensor 46) during each run, and the length of time for each run. Building schedules may also be considered as part of formulating predicted usage patterns. The data in the data storage module 62 is provided to the processor 60 and the processor 60 analyzes the usage characteristics to determine usage patterns. In some embodiments, the processor 62 employs sequential data analysis of the data, wherein the data is analyzed for patterns as it is stored in the data storage module 62. Processor 62 may update the predicted usage pattern after each elevator run to ensure that the pattern is based on as many data points as possible.

Processor 60 then sets the target SOC for ES system 32 based on the predicted usage pattern (step 72). Specifically, for each point in the predicted usage pattern, a target SOC is established that maximizes the amount of energy stored in ES system 32 while maintaining main power supply 20 below current and voltage limits and maintaining ES system 32 within storage capacity limits. To set the target SOC for ES system 30 at a given time, processor 60 monitors the current usage characteristics of elevator 14 and correlates these usage characteristics to a predicted usage pattern. When a current usage state with respect to the predicted usage pattern is established, a target SOC for the current usage state is set. By determining the current usage state of elevator 14 relative to the predicted usage pattern, processor 60 may predict future energy demand and adjust the target SOC of ES system 32 accordingly.

By observing the power limits of primary power source 20, the total power demand on primary power source 20 is reduced, which permits a reduction in the size of the components that deliver power from primary power source 20 to power system 10. In addition, when the SOC of the ES system 32 is maintained near the target SOC, the life of the ES system 32 may be extended by controlling the swing charge limit (swing charge limit) of the ES system 32. Although establishing the usage pattern and setting the target SOC are performed by the processor 60 of the drive controller 36 in the illustrated embodiment, these functions may also be performed by a processor that controls the scheduling of the elevator 14 or by a separate dedicated processor connected to the drive controller 36.

As one example, the predicted usage pattern may indicate that a large number of passengers are ascending to their floors on elevators during the monday through friday morning time period, and that the elevators are generally returning empty to the main floor. During that time period, it is expected that there will be a positive demand for power by the elevator motor, and a lower regeneration (negative demand) will occur. During that time period, the target SOC may be high, such that the regeneration and grid provide power (during idle times) for charging the ES 32. By counting the number of passengers who have gone up and comparing with the predicted patterns of passengers, a more accurate setting of the target SOC (a more accurate curing of the target SOC can be the only time of day used) can be accomplished than using only the time of day. If the SOC target results in a current above the design limit, the scheduler may adjust the time of the elevator stopping position to allow a lower level of current while meeting the SOC requirements.

In this example, in the evening of monday through friday, most passengers will descend to the main floor, and fewer people will ascend. Therefore, it is expected that more regeneration (negative demand) will occur than positive demand. During that time period, the target SOC may be reduced because charging of the ES system 32 will be less desirable during the idle period. Most of the recharge may be provided by regeneration.

Drive controller 36 controls the power exchanged between hoist motor 12, main power supply 20, and ES system 32 to address the power demand of hoist motor 12 and maintain the SOC of ES system 32 near the target SOC (step 74). Voltage regulator 30 (fig. 1) establishes the power demand of elevator hoist motor 12 and provides a signal related to this demand to drive controller 36. When hoist motor 12 power demand is positive, power is provided to hoist motor 12 at least partially from ES system 32 while the SOC of the ES system is at or above the target SOC. The proportion of power provided by the ES system 32 may also be a function of the proximity of the SOC to the target SOC. More specifically, a smaller portion of the power may be provided by ES system 32 to hoist motor 12 when the SOC of ES system 32 approaches the target SOC. Drive controller 36 controls regenerative drive 29 and ES system controller 34 to provide power to hoist motor 12 at the appropriate rate.

When the power demand of hoist motor 12 is negative, regenerative power from hoist motor 12 may be delivered to ES system 32 while the SOC of ES system 32 is below the target SOC. When the SOC of ES system 32 is at or above the target SOC during a negative hoist motor power demand period, regenerative power from hoist motor 12 may be delivered to main power supply 20. The proportion of power delivered from hoist motor 12 to ES system 32 during negative power demand cycles may also be a function of the proximity of SOC to the target SOC and provide a design tradeoff between system life and energy efficiency targets. The drive controller 36 controls the regenerative drive 29 and the ES system controller 34 to deliver power from the hoist motor 12 to the power supply 20 and the ES system 32 at an appropriate rate.

When the power demand of hoist motor 12 approaches zero, processor 60 may control regenerative drive 29 and ES system control 34 to deliver power from main power supply 20 to ES system 32 while the SOC of ES system 32 is below the target SOC. This recharges ES system 32 to near the target SOC, which ensures that the projected power demand of hoist motor 12 is effectively addressed (according to the predicted usage pattern).

By maintaining the SOC of ES system 32 near the target SOC, ES system 32 may also address the power requirements of hoist motor 12 in the event of a failure of primary power source 20. The target SOC is set such that power may be delivered to ES system 32 while hoist motor 12 is regenerating power without dissipating any energy. Additionally, the target SOC is high enough to allow for extended positive power demand operation of hoist motor 12 after a failure of main power supply 20.

During a failure of main power supply 20, ES system 32 addresses the power requirements of hoist motor 12. Thus, if the power demand of hoist motor 12 is positive, ES system 32 provides the demand, and if the power demand of hoist motor 12 is negative, ES system 32 stores the power regenerated by hoist motor 12. ES system 32 may be controlled as a function of the SOC of ES system 32 and address hoist motor power requirements only when the SOC of ES system 32 is within a certain range.

In summary, the present invention relates to managing power in an elevator system including an elevator hoist motor, a main power supply, and an electrical Energy Storage (ES) system. The predicted usage pattern for the hoist motor is established based on past hoist motor power demands. The target storage state (e.g., SOC) of the ES system is set according to the predicted usage pattern. Power exchanged between the hoist motor, the main power source, and the ES system is controlled to address the power demand of the hoist motor and maintain the storage state of the ES system near the target storage state. By controlling the storage state of the ES system according to past traffic (traffic) and power demand patterns, the energy stored in the ES system can be maximized while keeping it within the constraints of peak power drawn from the main power supply and the storage limits of the ES system, and minimizing the need to dissipate regenerative power. In addition, the life of the ES system may be extended by controlling the swing charge limit of the ES system while the storage state of the ES system remains near the target storage state.

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

1. A method for managing power distribution in an elevator system including an elevator hoist motor, a primary power source, and an energy storage system, the method comprising the steps of:

establishing a predicted usage pattern based at least in part on elevator hoist motor demand data;

setting a target storage state of the energy storage system according to the predicted usage pattern; and

controlling power exchanged between the elevator hoist motor, the primary power source, and the energy storage system to address a power demand of the elevator hoist motor and maintain the storage state of the energy storage system near the target storage state, wherein when the power demand of the elevator hoist motor is positive, the primary power source and the energy storage system provide power to the elevator hoist motor at a rate that maintains the storage state of the energy storage system near a target level, and when the power demand of the elevator hoist motor is negative, the power generated by the elevator hoist motor is provided to the primary power source and the energy storage system at a rate that increases the storage state of the energy storage system back near the target storage state.

2. The method of claim 1, wherein establishing a predicted usage pattern comprises:

storing elevator operation data including time between operations and power requirements for each operation; and

analyzing the elevator operating data to determine a usage pattern.

3. The method of claim 2, wherein analyzing the elevator operation data comprises performing a sequential analysis of the elevator operation data.

4. The method of claim 1, wherein the controlling step comprises:

employing the energy storage system to address elevator hoist motor power demand in proportion to a function of proximity of a storage state of the energy storage system to the target storage state.

5. The method of claim 1, wherein when the power demand of the elevator hoist motor is negative, the controlling step comprises:

delivering regenerative power from the elevator hoist motor to the energy storage system while the storage state of the energy storage system is below the target storage state; and

delivering regenerative power from the elevator hoist motor to the primary power source while the storage state of the energy storage system is at or above the target storage state.

6. The method of claim 1, wherein when the power demand of the elevator hoist motor is near zero, the controlling step comprises:

delivering power from the primary power source to the energy storage system while the storage state of the energy storage system is below the target storage state.

7. The method of claim 1, wherein when the power demand of the elevator hoist motor is positive, the controlling step comprises:

providing power at least partially from the energy storage system to the elevator hoist motor while the storage state of the energy storage system is at or above the target storage state.

8. The method of claim 1, wherein the predicted usage pattern is based in part on a predicted building schedule.

9. A method for addressing power requirements of an elevator hoist motor with a primary power source and an energy storage system, the method comprising:

monitoring usage characteristics related to the elevator hoist motor demand;

correlating the usage characteristics with the stored usage patterns;

setting a target storage state of the energy storage system according to the usage characteristics and the usage pattern; and

10. The method of claim 9, wherein the usage characteristics include time between runs of the elevator hoist motor and power requirements for each run.

11. The method of claim 9, wherein the controlling step comprises:

12. The method of claim 9, wherein when the power demand of the elevator hoist motor is negative, the controlling step comprises:

13. The method of claim 9, wherein when the power demand of the elevator hoist motor is near zero, the controlling step comprises:

14. The method of claim 9, wherein when the power demand of the elevator hoist motor is positive, the controlling step comprises:

15. The method of claim 9, further comprising:

the usage pattern is updated after operation of the elevator hoist motor.

16. An elevator system comprising:

an elevator hoist motor operable to control movement of an elevator car;

an elevator power system connected to the elevator hoist motor operable to address a power demand of the elevator hoist motor, the elevator power system connected to receive power from a primary power source and including an energy storage system; and

a controller operable to set a target storage state of the energy storage system as a function of current usage characteristics and predicted usage patterns of the elevator hoist motor, wherein the controller is further operable to control power exchanged between the elevator hoist motor, the primary power source, and the energy storage system in order to address power demand of the elevator hoist motor and maintain the storage state of the energy storage system near the target storage state,

wherein when the power demand of the elevator hoist motor is positive, the primary power source and the energy storage system provide power to the elevator hoist motor at a rate that maintains the storage state of the energy storage system near a target level, and when the power demand of the elevator hoist motor is negative, the power generated by the elevator hoist motor is provided to the primary power source and the energy storage system at a rate that increases the storage state of the energy storage system back near the target storage state.

17. The elevator system of claim 16, wherein the controller employs the energy storage system to address elevator hoist motor power demand in proportion as a function of proximity of the storage state of the energy storage system to the target storage state.

18. The elevator system of claim 16, wherein the controller stores elevator run data including time between runs of the elevator hoist motor and power demand for each run, and analyzes the elevator run data to determine usage patterns.

19. The elevator system of claim 16, wherein the controller updates the predicted usage pattern after elevator hoist motor operation.

20. The elevator system of claim 16, wherein the current usage characteristics include time between runs of the elevator hoist motor and power requirements of each run.