EP2542842B1

EP2542842B1 - Refrigeration system comprising a controller and associated method of controlling

Info

Publication number: EP2542842B1
Application number: EP11750976.0A
Authority: EP
Inventors: David James Mcshane; David James Howell; Ross Martin Green
Original assignee: Wellington Drive Technologies Ltd; Wellington Drive Tech Ltd
Current assignee: Wellington Drive Technologies Ltd; Wellington Drive Tech Ltd
Priority date: 2010-03-05
Filing date: 2011-03-03
Publication date: 2022-02-16
Anticipated expiration: 2031-03-03
Also published as: CN102869931B; US20130205807A1; WO2011108947A1; MX2012010282A; MX338483B; EP2542842A4; BR112012022453A2; EP2542842A1; CN102869931A; BR112012022453B1

Description

Technical Field

The invention generally relates to a refrigeration system comprising a controller and an associated control method.

Background Art

Beverage coolers are one type of refrigeration system utilized throughout the world to provide cost effective storage and delivery of consumable products in retail stores and other public distribution points. Beverage coolers utilize cooling devices to maintain the product at a serving temperature below the ambient temperature. The cooling devices typically include a compressor to compress a refrigerant, a condenser to condense the refrigerant and an evaporator to evaporate the refrigerant, as is well known. Internal cabinet lighting may also be provided.
Fans are normally provided for the condenser and for the evaporator inside the dispensing cabinet. The fan for the condenser provides cooling air for the refrigerant cooling process, the evaporator cools the air within the cabinet and also directs the cooled air along a required path, for instance past any glass door panels to remove condensation or past the product to ensure that the temperature gradient within the cabinet is low.
In order to maximise performance and minimise power consumption of such beverage coolers, it is increasingly common to use an electronic system controller. Such a system controller typically involves a user interface, inputs from one or more temperature sensors, and several relays to control operation of compressor, fan motors, and lighting, all controlled by a microprocessor. Additionally, the system controller may include the facility to accept input from one or more activity detectors such as door switches and movement sensors, and a real-time clock, thus allowing the storage temperature to be automatically adjusted to minimise power consumption during low-usage periods such as store closing hours, thus minimising operating costs. Such system controllers are well known and a variety of algorithms are available to control their behaviour.
In order to further reduce operating costs, it is also becoming comon to use energy-efficient components such as high-efficiency fan and compressor motors. Such motors are typically of the permanent magnet electronically commutated (EC) type, which require an electronic commutator in order to operate. Additionally, high-efficiency LED lighting may also be used, which also requires an electronic driver.
The combination of these devices leads to a single beverage cooler having up to five independent electronics units. This leads to redundancy of componentry and to complexity of communications between them, and thus to excessive cost and reduced reliability.
There is therefore a need for a control device for beverage coolers or components of beverage coolers which incorporates the functionality of several of the existing discrete control systems.
As stated above it is known to provide a central device which can control multiple other devices, such as in US patent specification 5764010 which describes a multiplex node controller for a vehicle but a separate controller module is still required. Document US2008115512A1 shows a refrigeration system comprising a host controller and separate commutation modules for the motors, wherein the host controller provides signals to the motor control, which signals determine the motor speed and hence the commutation. Document US5303562A shows prioritization of microprocessor routines, but only in relation to generalized motor control and not in relation to commutation.
The present invention provides a solution which offers advantages over the prior art or which will at least provide the public with a useful choice. The invention, which is defined in the appended independent claims, describes a controller for an EC motor which includes system control capability for the beverage cooler, and which may also incorporate part or all of the drive electronics for other devices within the cooler.

Summary of the Invention

A refrigeration system according to the present invention is defined by the subject-matter of appended independent claim 1.
Preferably the microprocessor receives inputs from door position sensors, fan speed sensors, and other environment sensors and determines the operating conditions of any motors from these inputs.
Preferably the system controller contains means to switch on and off any motors which are not commutated by the system controller in response to signals from the temperature sensing means.
Preferably the algorithm by which the motors and any other external devices are controlled includes inputs from presence detecting means such as door status, vibration, or motion detection
Preferably the algorithm by which motors and any other external devices are controlled includes a history of presence data recorded over a period of at least a day Preferably the algorithm by which motors and any other external devices are controlled includes inputs received from a user interface or other programming means Preferably the algorithm by which the compressor is controlled includes as an input information as to the operating status of the EC motor, the compressor behaviour being controlled such as to avoid system damage if the EC motor's actual operating status does not match the desired status
Preferably the system controller also contains means to convert mains-voltage input power into one or more low voltage outputs suitable for driving LED lighting. Preferably this means also supplies low voltage power to the at least one microprocessor and to other low voltage electronics within the controller Preferably where more than one microprocessor is used all microprocessors operate off a common reference voltage and are interconnected to communicate digitally without the use of an isolated communications bus
Preferably where the system controller commutates more than one motor all motors commutated share a common high voltage DC supply
A method of controlling a refrigeration system according to the present invention is defined by the subject-matter of appended independent claim 6. Preferably the method includes controlling any cooling fan motors using the microprocessor.
Preferably the method includes detecting any stalled fan motors using the microprocessor.
Preferably the method includes controlling the refrigeration system lights from the microprocessor.
Preferably the method includes providing a single low voltage power supply for the microprocessor and the lighting system.
Preferably the method includes providing a single high voltage DC supply for the motors commutated by the system
Preferably the microprocessor controls a refrigeration system compressor in accordance with the refrigeration temperature.
These and other features of as well as advantages which characterise the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.

Brief Description of the Drawings

FIG. 1 is a block diagram of a known electronically commutated refrigeration system motor controller.
FIG. 2 is a block diagram of a typical known beverage cooler system controller.
FIG. 3 is a block diagram of an integrated refrigeration controller which includes electronically commutated control of three motors and control of LED lighting and other functions.
FIG. 4 is a possible process flow control for the initializaton of such a refrigeration controller.
FIG. 5 is a process flow diagram of other controlled portions of the inventive beverage cooler.

Description of the Invention

In FIG. 1 a block diagram of a typical known electronically commutated motor controller 101. This controller 101 includes mains input 102 to a mains inputs processing stage 103, which typically comprises electronic noise suppression, inrush current suppression, fusing, and may also include power factor correction. A high voltage DC bus stage 104 rectifies the mains and provides a high voltage DC supply capable of providing the high currents to a motor controller 107 which powers the motor, in this case an evaporator fan motor 108. A low voltage power supply 105 derived from the high voltage supply 104 reduces the DC voltage to a suitable level to power the control electronics for a microprocessor 106 and smoothes it to an acceptable standard for reliable functionality. A power stage feeds current from the high voltage supply to the motor under control of the microprocessor 106 and may pass signals to the microprocessor 106 which can be used to infer motor status parameters such as rotor position and speed.
Alternative configurations are possible, for example the low voltage supply may be taken direct from the mains via a switched mode power supply (SMPS) rather than from the high voltage DC bus, and for motors using a current sensing mains synchronous control system the DC bus itself may be redundant since the motors will be powered from an AC driven version of motor control 107, but the general layout is typical of prior art motor controls.
In FIG. 2 a block diagram 201 of a typical known beverage cooler refrigeration system controller is shown. This includes a mains input processing stage 203 for mains supply 202 similar to that described above, a low voltage power supply 210, a microprocessor 212 which takes inputs from a real-time clock 211, a user interface 214, and several external sensors such as that for temperature at 216 or activity sensors 215. All these inputs are used to calculate when to switch AC power to motors and lighting off and on through a bank of high-current relays at 204, these controlling motors either directly as for condenser fan motor 207 and refrigerant compressor 208 or via a motor controller 205 such as is described with reference to FIG. 1.
In FIG. 3 there is shown the inventive controller 301 which is supplied with mains power at 302. A mains input processing block 303 similarly cleans the mains input before supplying it to a high voltage DC supplier 304 and also supplies a low voltage converter in the form of DC switch mode power supply 311. This supply primarily produces current for the LED lighting 318 associated with illuminating the interior and the advertising of the beverage cooler but also supplies the real time clock 312, the microprocessor 313 and the input conditioning 314. The input conditioning at 314 accepts information from temperature sensors 316 and from activity sensors, such as door open position sensors and proximity motion sensors which allow the beverage dispenser to react to changes in its environment.
The microprocessor provides commutation of at least one electronically commutated motor and control for the motor control power stages of the refrigeration system, which may provide simple switched on/off power control of the remaining motors, in each case via power control stages 305, 306, 307 respectively to the evaporator fan motor, the compressor motor or the condenser fan motor. No attempt is made to vary the HVDC supply of 304 since this would require independent control for each motor and a multiplication of the more expensive parts of the power supply.
Scheduling control of the various ancillaries such as motors and the sensing and response to the various sensors requires careful design of the microprocessor software, since it is important, for instance, that the microprocessor 313 continues to produce the commutation for evaporator fan motor 308 despite having to control the other motors and react to the sensors and the user interface. For this reason , according to the present invention, control is split into the primary tasks of controlling the motors, and secondary tasks of monitoring the sensors and reacting to the inputs. The secondary tasks may be managed by a low-priority loop which calls low-level subroutines to control detail aspects of motor and system control. This loop and its subroutines may be interrupted by higher-priority interrupts related to the time-critical aspects of controlling the motors , such as their commutation.
Where there is more than one EC motor controller microprocessor the controllers may be synchronised by a simple connection between microprocessors rather than a standard communication protocol bus.
FIG. 4 shows one possible control system process flow for the low priority loop in which at step 401 the microprocessor starts the system up at power initiation and then enters a low priority initialization sequence at step 402 in which at step 403 it checks settings such as storage temperature which may have been entered via the user interface. At step 404 it checks the presence history of persons opening the beverage cooler and at step 405 it calculates from this the location status, that is, whether at the current and near future times the location where the cooler is placed can be expected to experience high, low, or zero activity. From these calculations can be performed at step 406 from the system settings for the location including such parameters as a setpoint temperature, the desired lighting status, and maximum fan speeds based on the store status and the user settings. For example if the system calculates that the store has been closed for more than 1 hour, setpoint temperature may be raised and fan speeds reduced, as the beverages need not be kept stably at a desirable drinking temperature, and display lighting may be switched off, while advertising lighting may be left on or off depending on user settings.
At steps 407 and 408, the lighting is switched off or on or dimmed to match the settings calculated in step 406, and at step 409 temperature is measured from a temperature sensor and compared with the set point calculated at step 406. At step 410 motor speed and/or torque targets for fan and compressor motor are calculated and set so as to most rapidly and economically bring temperature closer to target. The general initialization of parameters is now complete.
Block 411 contains an abbreviated version of a general system sanity check algorithm for each motor on the operating status of the motor which is carried out on a timed interrupt driven basis, but also following initialization. At step 412 the system checks whether the particular motor should be running and if it is currently off the system returns at step 413. At step 414 the motor state is detected, as a speed sensor, measuring whether the motors are actually running, and if so checks at step 415 that the speed and current being drawn are as expected. If they are then any exception flags which are set are reset at step 416 and the system enters or re-enters the main control loop at step 417.
Should the at least one of the motors be found not to be running at step 414 the number of previous start attempts is checked at step 418 and if exceeded the beverage cooler compressor is shutdown at step 419 and a general alarm issued. If there are still restart attempts left a start is attempted at step 420. Such a start is later described with reference to block 510 of FIG. 5. A detected failure to start at step 421 adds to the count of failed starts at step 423 and throws an exception before returning to the main control loop. The process will eventually return to the check at step 403 again.
The speed/current check at step 415, when failed, results in a comparison of the found conditions at step 424 with those which correspond to the beverage cooler door being open, since this results in a change in the air flow patterns within the cabinet and changes in the motor loading as the air patterns at the door are disturbed compared to the stable situation with the door closed. These transient changes can be detected by the microprocessor and correspond to the presence of a person which allows the "door open" flag to be set at step 425 and a recorded presence history updated to show an access at step 426. It may also be used to modify the machine operation to cope with the "door open" condition. When the door is closed again the fan motor should revert to its original running condition, and the door will be recorded as shut.
If the change in speed or current is not a "door open" event an attempt is made at step 427 to classify it as another known type of change, for instance one due to a clogged condenser. In such a case the appropriate flag is set at step 428 and control returns to the main loop. Otherwise the condition is analysed as either hazardous or acceptable at step 429, the system shut down to avoid damage at step 419 if hazardous (for instance if the compressor motor is overpressuring), or flagged at step 430 as an alarm condition.
FIG. 5 shows in block 501 the main control loop 502. Typically this is an idle loop, acting to accept the interrupt driven routines which actually control the motors and monitor the conditions. Among such interrupts are event driven interrupts at block 503 and time driven interrupts at block 504. Among the former might be such things as the detection of a "motor stalled" flag, while among the latter could be the increase of the beverage temperature outside the access hours of the location or the occurrence of the regular check of the environment settings and sensor as at block 505. A settings and environment check will divert at step 506 to step 403 of FIG. 4 before reentering the motor check routine.
Fig 5 at block 510 shows one typical subroutine which manages the detail of motor startup. In this routine, which is called from step 418 a request for motor startup is received at step 511. A check is made as to whether the motor is actually sustainably rotating at step 512 (in other words that the motor is turning fast enough to be considered started) and if it is not a check is made at step 513 as to whether an excessive number of previous starts have been attempted. If so then there is clearly something in error with the load on the motor, so the motor is marked as stalled at step 514 and control returns to the main loop at step 515 with a stalled exception flag set. Where no previous start has been attempted the motor is aligned at step 516 to a known position, normally by applying current to one phase for a prolonged period. Current is then stepped to the next phase at 519 after a predetermined period set at step 517 and timed at step 518, and this is repeated through step 520 at diminishing periods, thus changing phases at the poles and accelerating the motor in an open-loop period, until speed is high enough for an EMF to be detected on the non-actuated phase via the loop to step 512. If at this point EMF is detected, the routine ends by exiting at step 515 and the motor commutates as normal, controlled by interrupt-driven switching routines. If EMF is not detected, the cycle may be repeated several times, until either a successful start is achieved or the motor is determined to be stalled. This routine may be called repeatedly using different parameters to start multiple motors in sequence.
Fig 5 shows one typical interrupt-driven routine to deal with time-critical tasks, in this case commutating a motor. This routine is called whenever one of the motors is detected as having rotated far enough to require commutation. The routine is entered at a phase transition step 531 and calculates at step 532 the period since the last commutation, from which instantaneous motor speed can be inferred. If this shows motor speed as too low, the phase current setting is increased to accelerate the motor at step 533. If too high, phase current setting is decreased at step 534 to slow the motor. Power is then switched to the new phase at step 535, and the new current settings applied before exiting the routine.
A similar lower priority routine may be the ancillary task of detecting an open door, to allow load compensation or to allow some interaction with the person opening the door. While detection of the door opening may be by a pressure activated door switch it may equally well be by way of detection of a change in the loading on the evaporator fan motor within the beverage cooler, since this will alter as the air circulation alters on door opening. Thus a simple detection of a change in fan motor speed or current draw because of a different flow pattern can act to detect the opening of the beverage cooler door. Other conditions, such as vibration, may also be sensed and some specified action taken on the occurrence of unexpected values.
Multiple interrupt-driven routines such as the above can be used to manage the time-critical tasks of operating a motor or motors, or of reading inputs, as each routine is designed to have a sufficiently small duration as not to noticeably impact the main system control loop. Although an accumulation of such interrupts may slow the control loop setting machine conditions in response to environment, customer use and motor conditions, it may be slowed by several orders of magnitude compared with its uninterrupted speed without affecting overall system performance, as the time constants in the overall system are of the order of minutes rather than milliseconds. The use of a microprocessor system allows other combinations of conditions to be checked, for instance a reduction in evaporator fan loading with time probably infers that the fan or evaporator needs cleaning, and an alert could be issued to warn of this. Thus while the description above shows an example control system with example process flows the actual process flows and control system may take many forms provided that the resulting embodiment or method comprises at least all features of the respective appended independent claim.
It is to be understood that even though numerous characteristics and advantages of the various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and functioning of various embodiments of the invention, this disclosure is illustrative only, and modifications are possible within the scope of the appended claims.

Industrial Applicability

The controller of the invention is used in the control of the motors and ancillaries which are employed it the refrigeration industry. The present invention is therefore industrially applicable.

Claims

A refrigeration system containing:
at least one motor driven refrigerant compressor (309),

at least one motor driven fan (308, 310),

at least one temperature sensor (316), and

a refrigeration system controller (301),

at least one of the compressor or fan motors (308, 309, 310) being electronically commutated motors, and

the refrigeration system controller (301) containing at least one microprocessor (313) commutating at least one of the electronically commutated motors driven from the system controller and the operation of any other motors in the refrigeration system and the operation of other ancillaries of the refrigeration system,

the microprocessor (313) additionally commutating at least said electronically commutated motor in relation to at least the temperature sensor output,
characterised in the commutation of at least one motor being a primary microprocessor task and monitoring the sensors and reacting to their inputs being a secondary microprocessor task,

wherein said secondary microprocessor task is interrupted by higher-priority interrupts related to the time-critical aspects of the commutation of the motors.
A refrigeration system as claimed in claim 1 wherein the microprocessor (313) receives inputs from door position sensors, fan speed sensors, and other environment sensors (317) and determines the operating conditions of any motors from these inputs.
A refrigeration system as claimed in claim 1 wherein the system controller contains means to switch on and off any motors which are not commutated by the system controller in response to signals from the temperature sensing means.
A refrigeration system as claimed in claim 1 wherein the algorithm by which the compressor is controlled includes as an input information as to the operating status of the EC motor, the compressor behaviour being controlled such as to avoid system damage if the EC motor's actual operating status does not match the desired status.
A refrigeration system as claimed in claim 1 wherein the system controller also contains a convertor to convert mains-voltage input power into one or more low voltage outputs suitable for driving LED lighting (318).
A method of controlling a refrigeration system having at least one electronically commutated motor and other electrical ancillaries by:
providing a microprocessor (313) to commutate the electronically commutated motor;

providing to the microprocessor inputs from any sensors (316, 317) associated with the refrigeration system;

characterised in controlling from the microprocessor any outputs to a refrigeration controller (310) and other electrical ancillaries associated with the refrigeration system, the commutation of at least one motor being a primary microprocessor task and monitoring the sensors and reacting to their inputs being a secondary microprocessor task,
wherein said secondary microprocessor task is interrupted by higher-priority interrupts related to the time-critical aspects of commutation the motors.
A method of controlling a refrigeration system as claimed in claim 6 wherein the method includes controlling any cooling fan motors (308, 310) using the microprocessor (313).
A method of controlling a refrigeration system as claimed in claim 6 wherein the method includes detecting any stalled fan motors using the microprocessor (313).
A method of controlling a refrigeration system as claimed in claim 6 wherein the method includes providing a single low voltage power supply (311) for the microprocessor and the lighting system.