Patent Application
20250012498
The application claims the benefit of China Patent Application No. 202310815394.5 filed Jul. 4, 2023, the contents of which are hereby incorporated in their entirety.
The present application relates to air conditioning technology and motor control technology, and in particular to a motor drive system for a chiller unit, a chiller unit comprising the motor drive system, a control method for a chiller unit, and a computer-readable storage medium on which is stored a computer program for implementing the method.
Screw chiller unit is a chiller unit with various forms of screw compressor as a host, which is increasingly widely used in the field of refrigeration and air conditioning. A typical screw chiller unit includes a screw compressor, condenser, evaporator, expansion mechanism, oil separator, as well as self-control components and instruments.
For the sake of energy conservation and efficiency improvement, the motor used for the compressor often utilizes a variable frequency drive as the driving component. However, the variable frequency drive is expensive, which leads to an extended investment payback period, especially when the screw chiller unit includes multiple compressors, the above problem is particularly prominent.
In accordance with an aspect of the present application, there is provided a motor drive system for a chiller unit, the chiller unit comprising a first compressor, a first motor for the first compressor, a second compressor and a second motor for the second compressor, the motor drive system comprising:
Optionally, in the motor drive system, a rated power of the first compressor is greater than or equal to a rated power of the second compressor.
Optionally, in the motor drive system, the number of the first compressors is one and the number of the second compressors is one or more.
Optionally, in the motor drive system, the control unit controls the output power of the variable frequency drive unit and the power frequency drive unit in the following manner:
Further optionally, in the motor drive system, the first output power is less than the output power of the variable frequency drive unit when the load demand is equal to the first critical value, and the second output power is equal to a maximum output power of the power frequency drive unit.
Alternatively, in the motor drive system, the first compressor and the second compressor are same types of compressors, the chiller unit is a screw chiller unit, and the first critical value is 50% of a rated load demand of the screw chiller unit.
Alternatively, in the motor drive system, the first compressor and the second compressor are different types of compressors, the chiller unit is a screw chiller unit, and the first critical value is 40% of a rated load demand of the screw chiller unit.
In accordance with another aspect of the present application, there is provided a chiller unit comprising:
In accordance with a further aspect of the present application, there is provided a control method for a chiller unit, the chiller unit comprising a first compressor, a first motor for the first compressor, a second compressor and a second motor for the second compressor, the method comprising:
In accordance with a still further aspect of the present application, there is provided a computer-readable storage medium on which a computer program suitable for running on a processor of a terminal device is stored, the running of the computer program resulting in the steps of the method as described above being performed.
The above and/or other aspects and advantages of the present application will be clearer and more easily understood from the following description of various aspects in conjunction with the accompanying drawings, in which the same or similar units are denoted by the same reference numerals. The accompanying drawings include:
The present application is described more fully below with reference to the accompanying drawings, in which illustrative embodiments of the application are illustrated. However, the present application may be implemented in different forms and should not be construed as limited to the embodiments presented herein. The presented embodiments are intended to make the disclosure herein comprehensive and complete, so as to more comprehensively convey the protection scope of the application to those skilled in the art.
In this specification, terms such as “comprising” and “including” mean that in addition to units and steps that are directly and clearly stated in the specification and claims, the technical solution of the application does not exclude the presence of other units and steps that are not directly or clearly stated in the specification and claims.
Unless otherwise specified, terms such as “first” and “second” do not indicate the order of the units in terms of time, space, size, etc., but are merely used to distinguish the units.
A screw chiller unit 10 shown in
Continuing to refer to
For exemplary purposes only, in the embodiment shown in
In the embodiment shown in
The control logic of the control unit 133 for the variable frequency drive unit 131 and the power frequency drive unit 132 is further described below.
For the purpose of energy conservation and efficiency improvement, it is natural to prioritize the operation of the variable frequency drive unit in the screw chiller unit shown in
In the control logic to be described hereinafter as the “equalization mode”, the variable frequency drive unit and the power frequency drive unit are enabled in a more equalized manner than in the priority mode. Specifically, when the load demand of the screw chiller unit starts to rise from zero, priority is still given to increasing the output power of the variable frequency drive unit 131 to adapt to the load demand, but unlike the priority mode, after the output power of the variable frequency drive unit 131 reaches a higher value (e.g., 70% of the maximum value), the subsequent load demand increment is adapted by alternately increasing the output power of the power frequency drive unit 132 and the variable frequency drive unit 131. On the other hand, when the load demand of the screw chiller unit decreases from a high point, the reduction in load demand is adapted by alternately decreasing the output power of the power frequency drive unit 132 and the variable frequency drive unit 131.
The inventors of the present application have found, after in-depth research, that when the following control logic (hereinafter referred to as the “crossover mode”) is adopted, the effect of energy conservation and efficiency improvement can be significantly improved as compared with the abovementioned priority mode and equalization mode.
Table 1 gives an example of the output power PVFD of the variable frequency drive unit 131 and the output power PFD of the power frequency drive unit 132 in the crossover mode vary in response to an increase in the load demand TOL_CAP. In Table 1, the output power PVFD and PFD are expressed as a percentage with respect to a maximum value of the respective output power, and the load demand TOL_CAP is expressed as a percentage with respect to the maximum load demand.
Table 2 gives an example of the output power PVFD of the variable frequency drive unit 131 and the output power PFD of the power frequency drive unit 132 in the crossover mode vary in response to a decrease in the load demand TOL_CAR. In Table 2) the output power PVFD and PFD are expressed as a percentage with respect to a maximum value of the respective output power, and the load demand TOL_CAP is expressed as a percentage with respect to the maximum load demand.
In the examples shown in Tables 1 and 2) the load demand TOL_CAP of the screw chiller unit is divided into the following multiple intervals:
When the load demand TOL_CAP is within the interval I, the load demand is adapted by operating only the variable frequency drive unit 131. For example, the variable frequency drive unit 131 is operated at a variable output power to adapt to changes in the load demand within the interval I. In this example, an upper limit of 40% of the interval I is equivalent to a critical point or critical value (hereinafter referred to as the first critical value T1). When this critical value is not exceeded, only the variable frequency drive unit 131 is in operation. Once exceeded, the power frequency drive unit 132 is operated in concert with the variable frequency drive unit 131 to match the desired load demand.
After the load demand TOL_CAP enters the interval II, the load demand is adapted by operating the variable frequency drive unit 131 and the power frequency drive unit 132 simultaneously. In particular, when the load demand increases from 40% to 50%, the load demand is adapted by gradually decreasing the output power of the variable frequency drive unit 131 and gradually increasing the output power of the power frequency drive unit 132. On the other hand, when the load demand decreases from 50% to 40%, the decreased load demand is adapted by simultaneously decreasing the output power of the variable frequency drive unit 131 and the output power of the power frequency drive unit 132.
Table 3 gives an example of the output power PVFD of the variable frequency drive unit 131 and the output power PFD of the power frequency drive unit 132 vary with the increase of the load demand TOL_CAP when the load demand TOL_CAP is within the interval II.
In the example shown in Table 3, when the load demand TOL_CAP reaches 50%, the output power of the variable frequency drive unit 131 is rapidly reduced from 80% to 50%, and at the same time, the output power of the power frequency drive unit 132 is increased from 20% to 50% to compensate for the reduction in the output power of the variable frequency drive unit 131, so that the overall output power of the first and second compressors is adapted to the load demand.
Table 4 gives an example of the output power PVFD of the variable frequency drive unit 131 and the output power PFD of the power frequency drive unit 132 vary with the decrease of the load demand TOL_CAP when the load demand TOL_CAP is within the interval II.
In the example shown in Table 4, when the load demand TOL_CAP reaches 40% (the aforementioned first critical value T1), the output power of the variable frequency drive unit 131 is rapidly increased from 40% to 80%, and at the same time, the output power of the power frequency drive unit 132 is rapidly reduced from 40% to 0, so that the overall output power of the first and second compressors remains adapted to the load demand.
When the load demand TOL_CAP is within the interval III, the load demand is adapted by simultaneously operating the variable frequency drive unit 131 and the power frequency drive unit 132. In particular, the variation of the load demand within the interval III is adapted by operating the variable frequency drive unit 131 at a first output power P1 and operating the power frequency drive unit 132 at a variable output power. In this example, a lower limit of 50% of the interval III is equivalent to a critical point or critical value (hereinafter referred to as the second critical value T2). Once this critical value is exceeded, the variable frequency drive unit 131 will operate at a fixed output power P1. Optionally, the output power P1 may be set to be less than the output power of the variable frequency drive unit 131 when the load demand is equal to the first critical value T1 (e.g., 80% of the maximum output power of the variable frequency drive unit 131 as shown in Table 1). For example, the output power P1 may be set to 50% of the maximum output power of the variable frequency drive unit 131 as shown in Table 1.
When the load demand TOL_CAP is within the interval IV, the variation of the load demand within the interval IV is adapted by operating the variable frequency drive unit 131 at a variable output power and operating the power frequency drive unit 132 at the second output power P2. In this example, a lower limit of 75% of the interval IV is equivalent to a critical point or critical value (hereinafter referred to as the third critical value T3). Once this critical value is exceeded, the variable frequency drive unit 131 will operate at a variable output power and the power frequency drive unit 132 will operate at a fixed output power. Optionally, the output power P2 may be set to the maximum output power of the power frequency drive unit 132.
As may be seen in
It should be noted that the interval division methods of load demand shown in Tables 1 and 2 are merely exemplary. Optionally, the upper limit or first critical value T1 of the interval I may be determined based on the types of the first and second compressors. For example, when the first and second compressors have different types, the first critical value T1 may be set to about 40% of the rated load demand of the screw chiller unit. When the first and second compressors have the same types, the first critical value T1 may be set to about 50% of the rated load demand of the screw chiller unit. Furthermore, the number of intervals shown in Tables 1 and 2 are also non-limiting. For example, in some other examples, the load demand TOL_CAP of the screw chiller unit is divided into the following multiple intervals:
In the above-described division, the first critical value T1 and the second critical value T2 may be combined into a critical value T. For example, when the critical value T is not exceeded, only the variable frequency drive unit 131 is in operation, whereas once the critical value T is exceeded, the variable frequency drive unit 131 will be operated at a fixed output power P1′ and the power frequency drive unit 132 will be operated at a variable output power. Optionally, the output power P1′ may be set to a smaller output power (e.g., 50%) relative to the output power (e.g., 80%) of the variable frequency drive unit 131 at the upper limit of the interval I.
As shown in
The communication unit 310 serves as a communication interface configured to establish a communication connection between the processing device and an external device (e.g., a variable frequency drive unit 131, a power frequency drive unit 132, a sensor, etc.) or a network (e.g., the Internet).
The memory 320 stores the computer program 340 that may be executed by the processor 330. In addition, the memory 320 may also store data generated by the processor 330 when executing the computer program and data or commands received externally via the communication unit 310.
The processor 330 is configured to run the computer program 340 stored on the memory 320 and to access data on the memory 320.
The method shown in
Step 401: The processing device 30 obtains or determines a current load demand of the screw chiller unit 10.
Step 402: The processing device 30 executes the control logic based on the aforementioned crossover mode based on the current load demand obtained or determined in step 401, so as to adapt the load demand of the screw chiller unit 10 by controlling the output power of the variable frequency drive unit 131 and the power frequency drive unit 132.
The control logic based on the crossover mode has been described in detail above and will not be repeated here.
Step 403: The processing device 30 determines whether it is necessary to continue executing the control logic, and if so, returns to step 401, otherwise, exits the process shown in
In accordance with another aspect of the present application, there is also provided a computer-readable storage medium on which is stored a computer program which, when executed by the processor, may implement one or more of the steps contained in the method described above with the aid of
The computer-readable storage medium referred to in the application includes various types of computer storage media, which may be any usable medium that may be accessed by a general-purpose or specialized computer. Byway of example, the computer-readable storage medium may include RAM, ROM, EPROM, E2PROM, registers, hard disks, removable disks, CD-ROM or other optical disk memories, magnetic disk memories, or other magnetic storage devices, or any other temporary or non-transitory medium that may be used to carry or store desired program code units in the form of instructions or data structures and may be accessed by general-purpose or special-purpose computers, or general-purpose or special-purpose processors. Combinations of the foregoing should also be included within the scope of protection of computer-readable storage medium. Exemplary storage medium are coupled to a processor to enable the processor to read and write information from/to the storage medium. In alternative embodiments, the storage medium may be integrated into the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In alternative embodiments, the processor and the storage medium may reside in the user terminal as discrete components.
Those skilled in the art will appreciate that various illustrative logical blocks, modules, circuits, and algorithm steps described herein may be implemented as electronic hardware, computer software, or combinations of both.
To demonstrate this interchangeability between the hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented in hardware or software depends on the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in changing ways for the particular application. However, such implementation decisions should not be interpreted as causing a departure from the scope of the present application.
Although only a few of the specific embodiments of the present application have been described, those skilled in the art will appreciate that the present application may be embodied in many other forms without departing from the spirit and scope thereof. Accordingly, the examples and implementations shown are to be regarded as illustrative and not restrictive, and various modifications and substitutions may be covered by the application without departing from the spirit and scope of the application as defined by the appended claims.
The embodiments and examples presented herein are provided to best illustrate embodiments in accordance with the present technology and its particular application, and to thereby enable those skilled in the art to implement and use the present application. However, those skilled in the art will appreciate that the above description and examples are provided for convenience of illustration and example only. The presented description is not intended to cover every aspect of the application or to limit the application to the precise form disclosed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023108153945 | Jul 2023 | CN | national |
