Frequency control method based on frequency conversion cascade heat pump system

Abstract

The invention relates to the technical field of variable-frequency control, in particular to a frequency control method based on a variable-frequency cascade heat pump system, the variable-frequency cascade heat pump system comprises a variable-frequency compressor and a fixed-frequency compressor, and the method comprises the following steps: S1, starting the variable-frequency compressor, raising the frequency to a preset starting frequency, and keeping a preset starting duration; s2, setting a high-temperature alarm value of a preset low-temperature section; s3, according to the preset low-temperature section high-temperature alarm value, the variable-frequency compressor and the fixed-frequency compressor are used for heating, and frequency increasing or frequency decreasing is conducted on the variable-frequency compressor according to the current low-temperature section high-pressure value; and S4, after heating reaches the preset target temperature, the variable-frequency compressor and the fixed-frequency compressor are closed. The pressure fluctuation in the variable-frequency cascade heat pump system is reduced, so that the stability of the system is ensured, and the user experience is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of variable frequency control, and in particular to a frequency control method based on a variable frequency cascade heat pump system. Background Art

[0002] Now the application of controllers based on single chip microcomputer is becoming more and more popular, and the requirements for control systems are getting higher and higher.

[0003] For the heating industry, whether the heat pump system can operate stably and reliably will directly affect the customer's product experience and industry reputation. Among them, the variable frequency cascade heating system is a system with better heating performance at present. For the variable frequency cascade heating system, since its heating depends on the operation of the compressor, the frequency control of the compressor in the system is one of the most important links.

[0004] In the variable frequency cascade heating system of the related technology, the compressor only adjusts the frequency of operation according to the change of the target temperature. Such a design is prone to system pressure fluctuations in actual use, causing the machine to frequently shut down due to high-pressure protection, affecting the user experience. Summary of the invention

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

[0006] In order to solve the above technical problems, the present 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 comprises the following steps:

[0007] S1, starting the variable frequency compressor and increasing the frequency to a preset starting frequency, and maintaining a preset starting time;

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

[0009] S3, using the variable frequency compressor and the fixed frequency compressor for heating 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 pressure value;

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

[0011] Furthermore, in step S3, the step of increasing or decreasing the frequency of the variable frequency compressor according to the current high pressure value of the low temperature section is specifically as follows:

[0012] Setting an adjustment interval according to the preset low temperature section high temperature alarm value;

[0013] If the current low-temperature section high pressure value is greater than the preset adjustment interval of the preset low-temperature section high temperature alarm value, the variable frequency compressor is frequency-reduced;

[0014] If the current low-temperature section high pressure value is less than the preset adjustment interval of the preset low-temperature section high temperature alarm value, the variable frequency compressor is subjected to frequency increase processing;

[0015] If the current low-temperature section high pressure value is within the preset adjustment interval of the preset low-temperature section high temperature alarm value, the frequency of the variable frequency compressor is kept unchanged.

[0016] Furthermore, step S3 further includes:

[0017] If any one of the variable frequency compressor and the fixed frequency compressor is shut down for protection, the variable frequency compressor and the fixed frequency compressor are shut down at the same time.

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

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

[0020] Furthermore, the adjustment interval is specifically:

[0021] The preset low temperature section high temperature alarm value is defined as A, the stable heating difference value of the low temperature section high pressure value compared to the preset low temperature section high temperature alarm value is defined as B, and the adjustment interval is [AB, A+B].

[0022] Furthermore, the preset low temperature section 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 variable frequency compressor is increased or decreased in frequency according to the current high pressure value of the low temperature section, the variable frequency compressor is increased or decreased by a preset adjustment frequency every time a preset adjustment cycle passes.

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

[0025] The beneficial effect achieved by the present invention is that a frequency control method based on a variable frequency cascade heat pump system is proposed. The method adjusts the frequency according to the heating pressure of the variable frequency cascade heat pump system, and reduces the pressure fluctuation in the variable frequency cascade heat pump system by setting a pressure range and a periodic frequency adjustment strategy, thereby ensuring the stability of the system and improving the user experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic flow chart of the steps of a frequency control method based on a variable frequency cascade heat pump system provided by an embodiment of the present invention;

[0027] Figure 2 It is a frequency conversion logic diagram of a variable frequency compressor provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] Please refer to Figure 1 , Figure 1 It is a schematic flow chart of the steps of a frequency control method based on a variable frequency cascade heat pump system provided by an embodiment of the present invention. The variable frequency cascade heat pump system includes a variable frequency compressor and a fixed frequency compressor. It can be understood that in the variable frequency cascade heat pump system, the fixed frequency compressor performs heating at a fixed frequency after starting, which is used to stably provide heating capacity, while the frequency of the variable frequency compressor after starting can be changed. According to the target temperature, the variable frequency compressor speeds up heating to the target temperature by changing the frequency, or delays heating to the target temperature as needed. 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 a preset starting frequency, and maintain a preset starting time.

[0031] Furthermore, in step S1, the preset starting frequency is 30 Hz, and the preset starting duration is 2 minutes. In the embodiment of the present invention, by increasing the frequency of the variable frequency compressor to the preset starting frequency and maintaining the preset starting duration, the variable frequency compressor can be preheated before starting heating to optimize working performance.

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

[0033] S3. According to the preset low-temperature section high-temperature alarm value, the variable-frequency compressor and the fixed-frequency compressor are used for heating, wherein the variable-frequency compressor is increased or decreased in frequency according to the current low-temperature section high-pressure value.

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

[0035] For further information, please refer to Figure 2 , Figure 2: is a frequency conversion logic diagram of the variable frequency compressor provided by an embodiment of the present invention. In step S3, the step of increasing or decreasing the frequency of the variable frequency compressor according to the current high pressure value of the low temperature section is specifically as follows:

[0036] Setting an adjustment interval according to the preset low temperature section high temperature alarm value;

[0037] If the current low-temperature section high pressure value is greater than the preset adjustment interval of the preset low-temperature section high temperature alarm value, the variable frequency compressor is frequency-reduced;

[0038] If the current low-temperature section high pressure value is less than the preset adjustment interval of the preset low-temperature section high temperature alarm value, the variable frequency compressor is subjected to frequency increase processing;

[0039] If the current low-temperature section high pressure value is within the preset adjustment interval of the preset low-temperature section high temperature alarm value, the frequency of the variable frequency compressor is kept unchanged.

[0040] Furthermore, the adjustment interval is specifically:

[0041] The preset low temperature section high temperature alarm value is defined as A, the stable heating difference value of the low temperature section high pressure value compared to the preset low temperature section high temperature alarm value is defined as B, and the adjustment interval is [AB, A+B].

[0042] Furthermore, the preset low-temperature section 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 an artificially set safety threshold. The above parameters can be set according to actual needs during implementation), and the stable heating difference B is 100kPa.

[0043] Furthermore, in step S3, when the variable frequency compressor is increased or decreased in frequency according to the current low temperature section high pressure value, the variable frequency compressor is increased or decreased by a preset adjustment frequency every preset adjustment period. Furthermore, the preset adjustment period is 10s, and the preset adjustment frequency is 1Hz.

[0044] Through such a frequency regulation method, the pressure fluctuation in the variable frequency cascade heat pump system can be reduced as much as possible, and the frequency stability of the variable frequency compressor in the variable frequency cascade heat pump system can be maintained.

[0045] Furthermore, step S3 further includes:

[0046] If any one of the variable frequency compressor and the fixed frequency compressor is shut down for protection, the variable frequency compressor and the fixed frequency compressor are shut down at the same time.

[0047] Furthermore, in step S4, before shutting down the variable frequency compressor, the variable frequency compressor is frequency-reduced to 0 Hz. Such a design can avoid the performance instability problem caused by the sudden shutdown of the variable frequency compressor at high frequency.

[0048] The beneficial effect achieved by the present invention is that a frequency control method based on a variable frequency cascade heat pump system is proposed. The method adjusts the frequency according to the heating pressure of the variable frequency cascade heat pump system, and reduces the pressure fluctuation in the variable frequency cascade heat pump system by setting a pressure range and a periodic frequency adjustment strategy, thereby ensuring the stability of the system and improving the user experience.

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

[0050] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0051] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present invention.

[0052] The embodiments of the present invention are described above in conjunction with the accompanying drawings. What is disclosed is only the preferred embodiment of the present invention. However, the present invention is not limited to the above-mentioned specific implementation manner. The above-mentioned specific implementation manner is only illustrative rather than restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms and equivalent changes without departing from the scope of protection of the purpose of the present invention and the claims, all of which are within the protection 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 comprises a variable frequency compressor and a fixed frequency compressor, characterized in that: The following steps are involved: S1, starting the variable frequency compressor and increasing the frequency to a preset starting frequency, and maintaining a preset starting time; S2. Set the preset low temperature section high temperature alarm value; S3, using the variable frequency compressor and the fixed frequency compressor for heating 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 pressure value; S4. After the heating reaches a preset target temperature, the variable frequency compressor and the fixed frequency compressor are turned off.

2. The frequency control method based on the variable frequency cascade heat pump system according to claim 1, characterized in that: In step S3, the step of increasing or decreasing the frequency of the variable frequency compressor according to the current high pressure value of the low temperature section is specifically as follows: Setting an adjustment interval according to the preset low temperature section high temperature alarm value; If the current low-temperature section high pressure value is greater than the preset adjustment interval of the preset low-temperature section high temperature alarm value, the variable frequency compressor is frequency-reduced; If the current low-temperature section high pressure value is less than the preset adjustment interval of the preset low-temperature section high temperature alarm value, the variable frequency compressor is subjected to frequency increase processing; If the current low-temperature section high pressure value is within the preset adjustment interval of the preset low-temperature section high temperature alarm value, the frequency of the variable frequency compressor is kept unchanged.

3. The frequency control method based on the variable frequency cascade heat pump system according to claim 1, characterized in that: Step S3 also includes: If any one of the variable frequency compressor and the fixed frequency compressor is shut down for protection, the variable frequency compressor and the fixed frequency compressor are shut down at the same time.

4. The frequency control method based on the 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 0 Hz.

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

6. The frequency control method based on the variable frequency cascade heat pump system according to claim 2, characterized in that: The adjustment interval is specifically: The preset low temperature section high temperature alarm value is defined as A, the stable heating difference value of the low temperature section high pressure value compared to the preset low temperature section high temperature alarm value is defined as B, and the adjustment interval is [AB, A+B].

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

8. The frequency control method based on the variable frequency cascade heat pump system according to claim 2, characterized in that: In step S3, when the frequency conversion compressor is increased or decreased according to the current high pressure value of the low temperature section, the frequency conversion compressor is increased or decreased by a preset adjustment frequency every time a preset adjustment cycle passes.

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

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