Frequency control method based on variable frequency cascade heat pump system

Abstract

The present application relates to the technical field of variable frequency control, and particularly relates to a frequency control method based on a variable frequency cascade heat pump system, the variable frequency cascade heat pump system comprising a variable frequency compressor and a fixed frequency compressor, the method comprising the following steps: S1, starting the variable frequency compressor and increasing the frequency to a preset starting frequency, and keeping the preset starting time length; S2, setting a preset low-temperature section high-temperature alarm value; S3, using the variable frequency compressor and the fixed frequency compressor to heat according to the preset low-temperature section high-temperature alarm value, wherein the variable frequency compressor is increased or decreased in frequency according to the current low-temperature section high-temperature value; S4, after heating reaches a preset target temperature, the variable frequency compressor and the fixed frequency compressor are turned off. The present application reduces pressure fluctuation in the variable frequency cascade heat pump system, thereby ensuring the stability of the system and improving user experience.

Description

Technical Field

[0001] This invention relates to the field of frequency conversion control technology, and in particular to a frequency control method based on a frequency conversion cascade heat pump system. Background Technology

[0002] The application of microcontroller-based controllers is becoming increasingly widespread, and the requirements for control systems are also becoming more and more demanding.

[0003] For the heating industry, the stability and reliability of heat pump systems directly impact customer user experience and industry reputation. Among these systems, variable frequency cascade heating systems currently offer superior heating performance. Since heating in variable frequency cascade heating systems relies on the operation of the compressor, compressor frequency control is a crucial aspect of the system.

[0004] In variable frequency cascade heating systems with related technologies, the compressor adjusts its frequency only according to changes in the target temperature. This design is prone to system pressure fluctuations in actual use, leading to frequent high-pressure protection shutdowns and affecting the user experience. Summary of the Invention

[0005] The present invention aims to solve the technical problem that existing variable frequency cascade heating systems are prone to shutdown due to pressure fluctuations during heating.

[0006] To address the aforementioned technical problems, this invention provides a frequency control method based on a variable frequency cascade heat pump system, wherein the variable frequency cascade heat pump system includes a variable frequency compressor and a fixed frequency compressor, and includes the following steps:

[0007] S1. Start the variable frequency compressor and increase the frequency to the preset start frequency, and maintain the preset start time;

[0008] S2. Set the preset high temperature alarm value for the low temperature range;

[0009] S3. According to the preset low-temperature high-temperature alarm value, use the variable frequency compressor and the fixed frequency compressor to perform heating, wherein the frequency of the variable frequency compressor is increased or decreased according to the current low-temperature high-pressure value.

[0010] S4. After the heating reaches the preset target temperature, turn off the variable frequency compressor and the fixed frequency compressor.

[0011] Furthermore, in step S3, the step of increasing or decreasing the frequency of the variable frequency compressor based on the current low-temperature high-pressure value specifically includes:

[0012] The adjustment range is set according to the preset low-temperature high-temperature alarm value;

[0013] If the current high pressure value in the low-temperature range is greater than the preset adjustment range of the preset high temperature alarm value in the low-temperature range, the frequency converter is frequency reduced.

[0014] If the current high pressure value in the low-temperature range is less than the preset adjustment range of the preset high temperature alarm value in the low-temperature range, the variable frequency compressor will be frequency-increased.

[0015] If the current high pressure value in the low temperature range is within the preset adjustment range of the preset high temperature alarm value in the low temperature range, the frequency of the variable frequency compressor remains unchanged.

[0016] Furthermore, step S3 also includes:

[0017] If either the variable frequency compressor or the fixed frequency compressor experiences a shutdown protection event, both the variable frequency compressor and the fixed frequency compressor will be shut down simultaneously.

[0018] Furthermore, in step S4, before shutting down the variable frequency compressor, the variable frequency compressor is reduced to 0Hz.

[0019] Furthermore, in step S1, the preset startup frequency is 30Hz and the preset startup duration is 2min.

[0020] Furthermore, the adjustment range is specifically defined as follows:

[0021] The preset low-temperature high-temperature alarm value is defined as A, the stable heating difference between the low-temperature high pressure value and the preset low-temperature high-temperature alarm value is defined as B, and the adjustment range is [AB, A+B].

[0022] Furthermore, the preset low-temperature high-temperature alarm value A is 3800 kPa, and the stable heating difference value B is 100 kPa.

[0023] Furthermore, in step S3, when the frequency of the variable frequency compressor is increased or decreased according to the current low-temperature high-pressure value, the frequency of the variable frequency compressor is increased or decreased by a preset adjustment frequency every preset adjustment cycle.

[0024] Furthermore, the preset adjustment period is 10s, and the preset adjustment frequency is 1Hz.

[0025] The beneficial effect achieved by this invention lies in proposing a frequency control method based on a variable frequency cascade heat pump system. This method adjusts the frequency according to the heating pressure of the variable frequency cascade heat pump system, and reduces pressure fluctuations in the variable frequency cascade heat pump system by setting pressure ranges and periodic frequency adjustment strategies, thereby ensuring system stability and improving user experience. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the steps of a frequency control method based on a variable frequency cascade heat pump system provided in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the variable frequency compressor variable frequency logic provided in an embodiment of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] Please refer to Figure 1 , Figure 1 This is a flowchart illustrating the steps of a frequency control method based on a variable frequency cascade heat pump system provided in this invention. The variable frequency cascade heat pump system includes a variable frequency compressor and a fixed frequency compressor. It is understood that in the variable frequency cascade heat pump system, the fixed frequency compressor provides heating at a fixed frequency after startup to stably provide heating capacity, while the frequency of the variable frequency compressor can be changed after startup. Depending on the target temperature, the variable frequency compressor can accelerate heating to the target temperature or delay heating to the target temperature as needed by changing its frequency. Specifically, the frequency control method based on the variable frequency cascade heat pump system includes the following steps:

[0030] S1. Start the variable frequency compressor and increase the frequency to the preset start frequency, and maintain the preset start time.

[0031] Furthermore, in step S1, the preset start-up frequency is 30Hz, and the preset start-up duration is 2 minutes. In this embodiment of the invention, by increasing the frequency of the variable frequency compressor to the preset start-up frequency and maintaining the preset start-up duration, the variable frequency compressor can be preheated before heating begins, thereby optimizing its performance.

[0032] S2. Set the preset high temperature alarm value for the low temperature range.

[0033] S3. According to the preset low temperature range high temperature alarm value, use the variable frequency compressor and the fixed frequency compressor to perform heating, wherein the variable frequency compressor is increased or decreased in frequency according to the current low temperature range high pressure value.

[0034] S4. After the heating reaches the preset target temperature, turn off the variable frequency compressor and the fixed frequency compressor.

[0035] Furthermore, please refer to Figure 2 , Figure 2This is a schematic diagram of the variable frequency compressor logic provided in an embodiment of the present invention. Step S3, which involves increasing or decreasing the frequency of the variable frequency compressor based on the current high pressure value in the low-temperature range, specifically includes:

[0036] The adjustment range is set according to the preset low-temperature high-temperature alarm value;

[0037] If the current high pressure value in the low-temperature range is greater than the preset adjustment range of the preset high temperature alarm value in the low-temperature range, the frequency converter is frequency reduced.

[0038] If the current high pressure value in the low-temperature range is less than the preset adjustment range of the preset high temperature alarm value in the low-temperature range, the variable frequency compressor will be frequency-increased.

[0039] If the current high pressure value in the low temperature range is within the preset adjustment range of the preset high temperature alarm value in the low temperature range, the frequency of the variable frequency compressor remains unchanged.

[0040] Furthermore, the adjustment range is specifically defined as follows:

[0041] The preset low-temperature high-temperature alarm value is defined as A, the stable heating difference between the low-temperature high pressure value and the preset low-temperature high-temperature alarm value is defined as B, and the adjustment range is [AB, A+B].

[0042] Furthermore, the preset low-temperature high-temperature alarm value A is 3800kPa (4300kPa-500kPa, where 4300kPa is the upper limit of the working pressure of the variable frequency cascade heat pump system, and 500kPa is a manually set safety threshold. The above parameters can be set according to actual needs during implementation), and the stable heating difference value B is 100kPa.

[0043] Furthermore, in step S3, when increasing or decreasing the frequency of the variable frequency compressor based on the current low-temperature high-pressure value, the variable frequency compressor is increased or decreased by a preset adjustment frequency every preset adjustment cycle. More specifically, the preset adjustment cycle is 10 seconds, and the preset adjustment frequency is 1 Hz.

[0044] This frequency regulation method can minimize pressure fluctuations in the variable frequency cascade heat pump system and maintain the frequency stability of the variable frequency compressor in the system.

[0045] Furthermore, step S3 also includes:

[0046] If either the variable frequency compressor or the fixed frequency compressor experiences a shutdown protection event, both the variable frequency compressor and the fixed frequency compressor will be shut down simultaneously.

[0047] Furthermore, in step S4, before shutting down the inverter compressor, the inverter compressor is reduced to 0Hz. This design avoids the performance instability problem caused by the inverter compressor suddenly shutting down from a high frequency.

[0048] The beneficial effect achieved by this invention lies in proposing a frequency control method based on a variable frequency cascade heat pump system. This method adjusts the frequency according to the heating pressure of the variable frequency cascade heat pump system, and reduces pressure fluctuations in the variable frequency cascade heat pump system by setting pressure ranges and periodic frequency adjustment strategies, thereby ensuring system stability and improving user experience.

[0049] Those skilled in the art will understand that all or part of the processes in the above embodiments can be implemented by a computer program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, it can include the processes of the embodiments of the above methods. The storage medium can be a magnetic disk, optical disk, read-only memory (ROM), or random access memory (RAM), etc.

[0050] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0051] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk), and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, air conditioner, or network device, etc.) to execute the methods described in the various embodiments of the present invention.

[0052] The embodiments of the present invention have been described above with reference to the accompanying drawings. The disclosed embodiments are merely preferred embodiments of the present invention. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many equivalent changes in form without departing from the spirit and scope of the claims of the present invention, and all such changes are within the protection scope of the present invention.

Claims

1. A frequency control method based on a variable frequency cascade heat pump system, wherein the variable frequency cascade heat pump system includes a variable frequency compressor and a fixed frequency compressor, characterized in that, Includes the following steps: S1. Start the variable frequency compressor and increase the frequency to the preset start frequency, and maintain the preset start time; S2. Set the preset high temperature alarm value for the low temperature range; S3. According to the preset low-temperature high-temperature alarm value, use the variable frequency compressor and the fixed frequency compressor to perform heating, wherein the frequency of the variable frequency compressor is increased or decreased according to the current low-temperature high-pressure value. S4. After the heating reaches the preset target temperature, the variable frequency compressor and the fixed frequency compressor are turned off. Specifically, step S3, which involves adjusting the frequency of the variable frequency compressor based on the current high pressure value in the low-temperature range, includes the following steps: The adjustment range is set according to the preset low-temperature high-temperature alarm value; If the current high pressure value in the low-temperature range is greater than the preset adjustment range of the preset high temperature alarm value in the low-temperature range, the frequency converter is frequency reduced. If the current high pressure value in the low-temperature range is less than the preset adjustment range of the preset high temperature alarm value in the low-temperature range, the variable frequency compressor will be frequency-increased. If the current high pressure value in the low temperature range is within the preset adjustment range of the preset high temperature alarm value in the low temperature range, the frequency of the variable frequency compressor remains unchanged.

2. The frequency control method based on a variable frequency cascade heat pump system according to claim 1, characterized in that, Step S3 also includes: If either the variable frequency compressor or the fixed frequency compressor experiences a shutdown protection event, both the variable frequency compressor and the fixed frequency compressor will be shut down simultaneously.

3. The frequency control method based on a variable frequency cascade heat pump system according to claim 1, characterized in that, In step S4, before shutting down the variable frequency compressor, the frequency of the variable frequency compressor is reduced to 0Hz.

4. The frequency control method based on a variable frequency cascade heat pump system according to claim 1, characterized in that, In step S1, the preset startup frequency is 30Hz and the preset startup duration is 2min.

5. The frequency control method based on a variable frequency cascade heat pump system according to claim 1, characterized in that, The adjustment range is specifically as follows: The preset low-temperature high-temperature alarm value is defined as A, the stable heating difference between the low-temperature high pressure value and the preset low-temperature high-temperature alarm value is defined as B, and the adjustment range is [AB, A+B].

6. The frequency control method based on a variable frequency cascade heat pump system according to claim 5, characterized in that, The preset low-temperature range high-temperature alarm value A is 3800 kPa, and the stable heating difference value B is 100 kPa.

7. The frequency control method based on a variable frequency cascade heat pump system according to claim 1, characterized in that, In step S3, when the frequency of the variable frequency compressor is increased or decreased according to the current low temperature high pressure value, the frequency of the variable frequency compressor is increased or decreased by a preset adjustment frequency every preset adjustment cycle.

8. The frequency control method based on a variable frequency cascade heat pump system according to claim 7, characterized in that, The preset adjustment period is 10s, and the preset adjustment frequency is 1Hz.

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