WO2019080276A1

WO2019080276A1 - Dynamic heating frequency optimization and control method for two-stage variable-frequency and two-stage compression heat pump water heater

Info

Publication number: WO2019080276A1
Application number: PCT/CN2017/115118
Authority: WO
Inventors: 吴治将; 李东洺; 李锡宇; 王斯焱; 徐言生; 彭莺; 陈妙阳
Original assignee: 顺德职业技术学院
Priority date: 2017-10-27
Filing date: 2017-12-08
Publication date: 2019-05-02
Also published as: CN107763872A

Abstract

A dynamic heating frequency optimization and control method for a two-stage variable-frequency and two-stage compression heat pump water heater, for optimizing and adjusting, throughout the operation of dynamic heating, the operating frequencies of a low-pressure stage variable-frequency compressor and a high-pressure stage variable-frequency compressor, segmenting and setting the operating frequency of the low-pressure stage compressor (1), enabling the segmented operating frequencies of the low-pressure stage variable-frequency compressor (1) in various temperature ranges to be distributed in a manner of arithmetic progression, such that the total energy consumption of the heat pump water heater throughout the operation is minimized. When the actual operation condition of the heat pump water heater deviates from a reference operation condition, the segmented operation frequency of the low-pressure stage variable-frequency compressor (1) corresponding to each temperature range of a water tank (7) is corrected according to the actual outdoor temperature.

Description

Dynamic heating frequency optimization and control method for two-stage variable frequency two-stage compression heat pump water heater

Technical field

The invention relates to a heat pump water heater control method, in particular to a dynamic heating frequency optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater.

Background technique

The two-stage compression heat pump water heater can produce high temperature hot water at a lower outdoor ambient temperature. Both low-pressure compressors and high-pressure compressors use variable-frequency compressors with two-stage inverter two-stage compression heat pump water heaters for higher heat regulation and energy efficiency ratio. In order to improve the energy efficiency ratio of the inverter for the low-voltage stage and the variable-frequency two-stage compression heat pump water heater using the fixed-frequency compressor, the Chinese patent announces “a control method for dynamic heating of a variable-frequency two-stage compression heat pump water heater”. The patent number is the invention patent of ZL201410759807.3; it can adjust the working frequency of the low-pressure compressor and the intermediate temperature of the heat pump according to the heat demand of the user and the outdoor ambient temperature of the heat pump water heater and the temperature of the water tank; the basic principle is to make the heat pump water heater run through the whole process. The instantaneous energy efficiency ratio at each moment is as close as possible to the optimal energy efficiency ratio under the operating conditions, that is, the higher the instantaneous energy efficiency ratio at each moment, and the total energy consumption of the heat pump water heater during the whole operation process under the condition of obtaining the same total heating capacity. The smaller, but the conclusion is that the instantaneous heat transfer of the heat pump must be equal throughout the operation. In fact, during the operation of the heat pump water heater, due to changes in operating conditions and changes in compressor frequency, the instantaneous heat generation of the heat pump water heater varies greatly; therefore, the frequency regulation of the low-pressure compressor of the variable-frequency two-stage heat pump water heater proposed in the aforementioned patent document The method still needs to be optimized, that is, in the process of optimizing the frequency of the low-pressure compressor of the variable-frequency two-stage heat pump water heater, it is also necessary to consider the change of the instantaneous heat generation to minimize the total energy consumption of the heat pump water heater during the whole operation process. In addition, the existing two-stage variable frequency two-stage heat pump water heater compressor frequency adjustment method is mainly based on a stable heating mode. During the heating operation, the water in the water tank is closed and heated, that is, the water tank does not discharge hot water during the process. There is no cold water to enter, and the water temperature is always rising. In fact, in most cases, when the user is using water, the water tank will be replenished with cold water from the outside. The water temperature in the water tank will continuously decrease. During the heating process, the water temperature of the water tank is a dynamic process of first falling and then rising, that is, dynamic heating, the US Department of Energy. The relevant standards for energy efficiency testing of heat pump water heaters are also based on dynamic heating. For the dynamic heating process of the two-stage variable frequency two-stage compression heat pump water heater, it is necessary to consider the change of instantaneous heat generation, and also consider the situation of the water inlet and outlet of the water tank, and optimize the adjustment of the low-frequency compressor frequency and the high-pressure stage compressor frequency. The heat pump water heater has the lowest total energy consumption during the entire operation process.

Summary of the invention

The object of the present invention is to overcome the deficiencies of the prior art and provide a dynamic heating frequency optimization and control method for a variable frequency two-stage compression heat pump water heater, which can be based on the outdoor environmental temperature of the heat pump water heater, the temperature of the water tank and the water consumption of the user. Optimize the operating frequency of the low-voltage inverter compressor during heating, and according to the heat pump water heater refrigeration system The optimal intermediate temperature adjusts the operating frequency of the high-pressure stage inverter compressor to minimize the total energy consumption of the heat pump water heater during the entire operation process, thereby achieving energy saving purposes.

In order to achieve the above object, the present invention is achieved by the present invention, which is a dynamic heating frequency optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater, and the two-stage variable frequency two-stage compression heat pump water heater includes a low-voltage inverter compressor and low-voltage compression. Engine exhaust temperature sensor, high pressure stage inverter compressor, high pressure stage compressor exhaust temperature sensor, controller, water tank sensor, water tank, condenser, high pressure stage electronic expansion valve, intercooler temperature sensor, intercooler, low pressure stage Electronic expansion valve, evaporator and outdoor temperature sensor; characterized in that: the two-stage variable frequency two-stage compression heat pump water heater performs dynamic heating operation, that is, the heat pump water heater performs heating operation simultaneously during the user's use of hot water, during the whole dynamic heating operation Optimize the operating frequency of the low-voltage inverter compressor and the high-voltage inverter compressor to minimize the total energy consumption of the heat pump water heater during the whole operation process; the optimal adjustment method of the operating frequency of the low-voltage inverter compressor and the high-voltage inverter compressor is as follows:

(a) Determine the dynamic heating reference conditions of the heat pump water heater, including the outdoor ambient temperature T _W and the relative humidity φ, the set upper limit temperature T _{S of the} water tank, the lower limit temperature T _X , the inlet cold water temperature and the hot water temperature, and the rated water consumption;

(b) Establish the relationship between the heat pump water heater with the outdoor ambient temperature T _O and the actual temperature T of the water tank, and the intermediate temperature T ₃ of the heat pump refrigeration system with the best instantaneous energy efficiency ratio EER as the target: T ₃ =F(T _O , T);

(c) Set the operating frequency of the low-pressure compressor f: According to the difference between the upper limit water temperature T _S and the lower limit water temperature T _X of the heat pump water tank, the temperature difference is n temperature segments, n ≥ 2, in The low-voltage inverter compressors of different temperature sections adopt different segmentation working frequencies f _i ;

(d) According to the temperature difference section of the water tank, the segmentation working frequency f _i of the low-voltage stage variable frequency compressor in each temperature section is distributed according to the arithmetic progression, and the calculation formula II of the segmentation working frequency f _i of each temperature rise section is obtained: f _i =f _g -(f _g -f _d )(i-1)/(n-1), in formula II, f _g is the highest frequency value of the low-voltage inverter compressor during the whole operation; f _d is the whole operation The lowest frequency value of the low-voltage inverter compressor in the process; i represents the respective heating range corresponding to the initial heating, i=1, 2,...,n;

(e) With the goal of minimizing the total energy consumption during the whole dynamic operation of the heat pump water heater, the highest frequency f _g and the lowest frequency f _{d of the} low-pressure stage inverter compressor under the standard working conditions are obtained through experiments, and the respective temperatures are obtained according to the calculation formula II. The segmentation operating frequency f _i of the low-voltage inverter compressor corresponding to the segment;

(f) When the actual operating condition of the heat pump water heater deviates from the reference working condition, the sectional operating frequency f _i of the low-voltage stage variable frequency compressor corresponding to each temperature section of the water tank is corrected according to the actual outdoor environmental temperature T _O ; the actual operating condition is the low-voltage stage The actual operating frequency g _{i of the} inverter compressor is corrected according to the formula III: g _i = kf _i , and different outdoor ambient temperatures T _O correspond to different k, which are obtained through experiments;

(g) During the water temperature drop and rise of the water tank, the operating frequency of the low-voltage inverter compressor is operated according to the actual operating frequency g _i calculated by Equation III;

(h) The controller detects the outdoor ambient temperature T _O and the actual temperature T of the water tank, and calculates the optimal intermediate temperature T ₃ according to the relationship I, and adjusts the operating frequency f _{b of the} high-voltage stage inverter compressor to detect the intermediate temperature sensor. The actual intermediate temperature approaches the value of the calculated optimal intermediate temperature T ₃ ;

(i) The frequency range for stable operation of the inverter compressor is generally 20 Hz-100 Hz. For each temperature range obtained according to formula III, a temperature range of less than 20 Hz occurs in the actual operating frequency g _i of the low-voltage inverter compressor. The operating frequency of the inverter compressor is operated at 20 Hz; if there is a temperature range greater than 100 Hz, the operating frequency of the low-voltage inverter compressor in this temperature section is operated at 100 Hz; similarly, the operating frequency requirement of the high-voltage inverter compressor is less than 20 Hz. Run at 20Hz, when required to be greater than 100Hz, run at 100Hz.

In the technical solution, in each temperature rise section of the water tank, the sectional operating frequency f _{i of the} low-voltage stage variable frequency compressor can be distributed according to a quadratic curve, that is, the formula IV: f _i = ai ² + bi + c, in the formula IV a, b, and c are the coefficients of the quadratic curve obtained by experiment.

In the technical solution, the low-voltage inverter compressor and the high-voltage inverter compressor can be an AC inverter compressor or a DC speed compressor.

Compared with the prior art, the main advantage of the invention is that the two-stage variable frequency two-stage compression heat pump water heater optimizes the working frequency of the low-pressure stage inverter compressor and the high-pressure stage compressor during the whole dynamic heating operation, so that the whole operation process is always Minimal energy consumption.

DRAWINGS

1 is a schematic diagram of a two-stage variable frequency two-stage compression heat pump water heater system according to an embodiment of the present invention;

2 is a schematic view showing the temperature change of the water tank during the dynamic heating process of the two-stage variable frequency two-stage compression heat pump water heater according to the present invention.

Detailed ways

Embodiments of the invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are intended to be illustrative of the invention and are not to be construed as limiting.

As shown in Figure 1, the two-stage variable frequency two-stage compression heat pump water heater includes a low-pressure stage inverter compressor, a low-pressure stage inverter compressor exhaust temperature sensor 2, a high-pressure stage inverter compressor 3, and a high-pressure stage compressor exhaust temperature sensor. The controller 5, the water tank sensor 6, the water tank 7, the condenser 8, the high-pressure stage electronic expansion valve 9, the intercooler temperature sensor 10, the intercooler 11, the low-pressure stage electronic expansion valve 12, the evaporator 13 and the outdoor temperature sensor 14; As shown in Fig. 2, the dynamic heating process of the heat pump water heater is as follows: at the beginning, the water temperature of the water tank 7 is the set upper limit temperature T _S , and when the user starts using the hot water from time t ₁ , the water tank will replenish the cold water from the outside, and the water temperature in the water tank 7 starts. Lower, the heat pump water heater also starts heating operation. Since the heat of the hot water is greater than the heat of the heat pump, the water temperature in the water tank 7 continues to decrease. When the water temperature reaches the set temperature lower limit T _X , the user stops using water, and the time is t ₂ , because only the heat pump water heater system, users do not have heat, temperature begins to rise until time t ₃ reaches the set limit temperature T _S, the heat pump water heater is stopped, times t ₁ to t ₃ A heat pump water heater full dynamic heating process; dynamic throughout the heating process, and a low-pressure stage compressor inverter operating frequency of the high-pressure stage compressor 3 optimized frequency adjustment method is as follows:

Two-stage variable frequency two-stage compression heat pump water heater dynamic heating frequency optimization and control method, two-stage variable frequency two-stage compression heat pump water heater including low-voltage stage inverter compressor 1, low-pressure stage compressor exhaust temperature sensor 2, high-voltage stage inverter compressor 3, high voltage Stage compressor exhaust temperature sensor 4, controller 5, water tank sensor 6, water tank 7, condenser 8, high pressure stage electronic expansion valve 9, intercooler temperature sensor 10, intercooler 11, low pressure stage electronic expansion valve 12, The evaporator 13 and the outdoor temperature sensor 14; the two-stage variable frequency two-stage compression heat pump water heater performs dynamic heating operation, that is, the heat pump water heater simultaneously performs heating operation during the hot water process of the user, and the low-voltage stage frequency conversion compression during the whole dynamic heating operation process The operating frequency of the machine 1 and the high-voltage stage inverter 3 is optimally adjusted to minimize the total energy consumption of the heat pump water heater throughout the operation process; the operating frequency optimization adjustment methods of the low-pressure stage inverter 1 and the high-voltage stage inverter 3 are as follows:

(a) Determine the dynamic heating reference conditions of the heat pump water heater, including the outdoor ambient temperature T _W and the relative humidity φ, the set upper limit temperature T _{S of the} water tank 7, the lower limit temperature T _X , the inlet cold water temperature and the hot water temperature, and the rated water consumption. ;

(b) establishing with the heat pump water heater, the actual temperature change of the outdoor temperature T _O T 7 of the tank, the instantaneous optimum energy efficiency (EER) heat pump refrigeration systems intermediate target temperature T ₃ is the relation of formula _{I: T 3 = F (T} O , T);

(c) setting the operating frequency f of the low-pressure compressor 1 in stages: according to the difference between the set upper limit water temperature T _S and the lower limit water temperature T _X of the heat pump water tank 7 , the temperature difference is made into n temperature segments, n ≥ 2 In each temperature section, the low-voltage inverter compressor 1 adopts different segmentation operating frequencies f _i ;

(d) According to the temperature difference section of the water tank 7, the segmentation operating frequency f _i of the low-voltage stage variable frequency compressor 1 in each temperature section is distributed by the arithmetic progression, and the calculation formula II of the segmentation working frequency f _i of each temperature rise section is obtained: f _i =f _g -(f _g -f _d )(i-1)/(n-1), in formula II, f _g is the highest frequency value of the low-voltage inverter (1) during the whole operation; f _d is the lowest frequency value of the low-voltage inverter compressor 1 during the whole operation; i represents each temperature rising section corresponding to the initial heating, i=1, 2,...,n;

(e) Taking the minimum energy consumption during the whole dynamic operation of the heat pump water heater as the target, the highest frequency f _g and the lowest frequency f _{d of the} low-voltage inverter compressor 1 under the standard working conditions are obtained through experiments, and each is obtained according to the calculation formula II. The segmentation operating frequency f _i of the low-voltage stage inverter 1 corresponding to the temperature section;

(f) when the actual operating state of the heat pump water heater deviates from the reference conditions, the actual outdoor temperature T _O is corrected tank section 7 corresponding to each temperature low-pressure stage compressor inverter operating frequency f _i 1 segment; the actual operating conditions The actual operating frequency g _{i of the} low-voltage inverter compressor 1 is corrected according to the formula III: g _i = kf _i , and different outdoor ambient temperatures T _O correspond to different k, which are obtained through experiments;

(g) during the water temperature drop and rise of the water tank 7, the operating frequency of the low-pressure stage inverter compressor 1 is operated according to the actual operating frequency g _i calculated by the formula III;

(h) The controller 5 detects the outdoor ambient temperature T _O , the actual temperature T of the water tank 7, calculates the optimum intermediate temperature T ₃ according to the relationship I, and adjusts the operating frequency f _{b of the} high-voltage stage inverter 3 to make the intermediate temperature The actual intermediate temperature detected by the sensor 11 approaches the value of the calculated optimal intermediate temperature T ₃ ;

(i) The frequency range of the stable operation of the inverter compressor is generally 20 Hz-100 Hz. For each temperature range obtained according to formula III, a temperature range of less than 20 Hz appears in the actual operating frequency g _i of the low-voltage inverter compressor 1 . The operating frequency of the low-voltage inverter compressor 1 is operated at 20 Hz; if a temperature range greater than 100 Hz occurs, the operating frequency of the low-voltage inverter compressor 1 is operated at 100 Hz; similarly, the operating frequency of the high-voltage inverter 3 It is required to run at 20 Hz when it is less than 20 Hz, and at 100 Hz when it is required to be greater than 100 Hz.

In the present embodiment, in each temperature rise section of the water tank 7, the sectional operating frequency f _{i of the} low-voltage stage inverter compressor 1 can be distributed according to a quadratic curve, that is, the formula IV: f _i = ai ² + bi + c, the formula In IV, a, b, and c are the coefficients of the quadratic curve obtained by experiment.

In this embodiment, the low-voltage stage inverter compressor 1 and the high-voltage stage inverter compressor 3 may both be an AC inverter compressor or a DC speed-regulating compressor.

While the embodiments of the present invention have been shown and described, the embodiments of the invention The scope of the invention is defined by the claims and their equivalents.

Claims

Dynamic heating frequency optimization and control method for two-stage variable frequency two-stage compression heat pump water heater, two-stage variable frequency two-stage compression heat pump water heater including low-pressure stage inverter compressor (1), low-pressure stage compressor exhaust temperature sensor (2), high-pressure stage Inverter compressor (3), high-pressure compressor exhaust temperature sensor (4), controller (5), water tank sensor (6), water tank (7), condenser (8), high-pressure electronic expansion valve (9) , intercooler temperature sensor (10), intercooler (11), low-voltage electronic expansion valve (12), evaporator (13) and outdoor temperature sensor (14); characterized by: two-stage variable frequency two-stage compression heat pump The water heater is dynamically heated, that is, the heat pump water heater is simultaneously heated during the hot water process, and the operating frequency of the low-pressure inverter compressor (1) and the high-voltage inverter compressor (3) during the entire dynamic heating operation. Optimize the adjustment to minimize the total energy consumption of the heat pump water heater during the whole operation process; the optimal adjustment method of the operating frequency of the low-pressure stage inverter compressor (1) and the high-pressure stage inverter compressor (3) is as follows:

Determine the dynamic heating reference condition of the heat pump water heater, including the outdoor ambient temperature T W and the relative humidity φ, the set upper limit temperature T S of the water tank (7), the lower limit temperature T X , the inlet cold water temperature and the hot water temperature, and the rated water consumption;

Establish the relationship between the heat pump water heater with the outdoor ambient temperature T O and the actual temperature T of the water tank (7), and the intermediate temperature T 3 of the heat pump refrigeration system with the best instantaneous energy efficiency ratio EER as the target. I: T 3 =F(T O , T);

The operating frequency f of the low-pressure compressor (1) is set in sections: according to the difference between the upper limit water temperature T S and the lower limit water temperature T X of the heat pump water tank (7), the temperature difference is made into n temperature segments, n≥ 2, in each temperature section low-voltage inverter compressor (1) uses different segmentation operating frequency f i ;

According to the temperature difference section of the water tank (7), the segmentation working frequency f i of the low-voltage inverter compressor (1) in each temperature section is distributed according to the arithmetic progression, and the calculation formula of the segmentation working frequency f i of each temperature rise section is obtained. :f i =f g -(f g -f d )(i-1)/(n-1), in formula II, f g is the highest frequency value of the low-voltage inverter (1) during the whole operation ;f d is the lowest frequency value of the low-voltage inverter (1) during the whole operation; i represents the respective heating range corresponding to the initial heating, i=1, 2,...,n;

Taking the minimum energy consumption during the whole dynamic operation of the heat pump water heater as the target, the highest frequency f g and the lowest frequency f d of the low-voltage inverter compressor (1) under the standard working condition are obtained through experiments, and the temperature is obtained according to the calculation formula II. The segmentation operating frequency f i of the low-voltage inverter (1) corresponding to the segment;

When the actual operating state of the heat pump water heater deviates from the reference conditions, the actual outdoor temperature T O is corrected tank (7) at each temperature corresponding to the low-pressure section of the inverter compressor stage (1) segment operating frequency f i; actual operating The actual operating frequency g i of the low-voltage inverter compressor (1) is corrected according to the formula III: g i = kf i , and different outdoor ambient temperatures T O correspond to different k, which are obtained through experiments;

During the water temperature drop and rise of the water tank (7), the operating frequency of the low-voltage inverter compressor (1) is operated according to the actual working frequency g i calculated by Formula III;

The controller (5) detects the outdoor ambient temperature T O , the actual temperature T of the water tank (7), calculates the optimal intermediate temperature T 3 according to the relationship I, and adjusts the operating frequency f b of the high-voltage inverter compressor (3). Having the actual intermediate temperature detected by the intermediate temperature sensor (11) approach the value of the calculated optimal intermediate temperature T 3 ;

The frequency range of the stable operation of the inverter compressor is generally 20 Hz-100 Hz. For each temperature section obtained according to formula III, the temperature range of less than 20 Hz appears in the actual operating frequency g i of the low-voltage inverter (1). The operating frequency of the inverter compressor (1) is operated at 20 Hz; if a temperature range greater than 100 Hz occurs, the operating frequency of the low-voltage inverter compressor (1) is operated at 100 Hz; similarly, the high-voltage inverter compressor ( 3) When the working frequency requirement is less than 20Hz, run at 20Hz, when the requirement is greater than 100Hz, run at 100Hz.
The dynamic heating frequency optimization and control method for a variable frequency two-stage compression heat pump water heater according to claim 1, characterized in that in each temperature rise section of the water tank (7), the sectional operating frequency f i of the low-voltage stage inverter compressor (1) It can be distributed as a quadratic curve, that is, the formula IV: f i = ai 2 + bi + c, and a, b, c in the formula IV are the coefficients of the quadratic curve obtained by the experiment.
The frequency dynamic optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater according to claim 1, wherein the low-voltage stage inverter compressor (1) and the high-voltage stage inverter compressor (3) are both AC frequency conversion compression Machine or DC speed control compressor.