WO2019080278A1

WO2019080278A1 - Method for dynamically optimizing and controlling frequency two-stage variable frequency two-stage compression heat pump water heater

Info

Publication number: WO2019080278A1
Application number: PCT/CN2017/115120
Authority: WO
Inventors: 吴治将; 李锡宇; 李东洺; 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: CN107906752A; CN107906752B

Abstract

A method for dynamic optimizing and controlling the frequency of a two-stage variable frequency two-stage compression heat pump water heater, comprising a low pressure stage variable frequency compressor (1), a low pressure stage compressor exhaust gas temperature sensor (2), a high pressure stage variable frequency compressor (3), a high pressure stage compressor exhaust gas temperature sensor (4), a controller (5), a water tank sensor (6), a water storage tank (7), a condenser (8), a high pressure stage electric expansion valve (9), an intermediate cooler temperature sensor (10), an intermediate cooler (11), a low pressure stage electric expansion valve (12), an evaporator (13) and an outdoor temperature sensor (14); the heat pump water heater dynamically optimizes and regulates the working frequency of the low pressure stage variable frequency compressor (1) and the high pressure stage variable frequency compressor (3) during the entire operation process so as to to minimize the total energy consumption of the heat pump water heater during the entire operation process.

Description

Frequency dynamic optimization and control method of 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 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 with high-frequency stage using fixed-frequency compressor, the Chinese patent announces the invention patent of “control method for a variable-frequency two-stage compression heat pump water heater”. The invention patent number is ZL201410759807.3, which can dynamically adjust the working frequency of the low-pressure compressor and the intermediate temperature of the heat pump according to the user's heat demand and the outdoor 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 throughout The instantaneous energy efficiency ratio at each moment in the operation process 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, the total heat pump water heater under the condition of obtaining the same total heating capacity. The lower the energy consumption; however, this conclusion is established on the condition that the instantaneous heat generation of the heat pump must be equal throughout the operation. In fact, during the operation of the heat pump water heater, due to the change of operating conditions and the change of the compressor frequency, the instantaneous heat quantity of the heat pump water heater varies greatly. Therefore, the frequency regulation method of the low-pressure stage compressor of the variable-frequency two-stage heat pump water heater proposed in the aforementioned patent document is still To be optimized, that is, in the frequency optimization process of the low-pressure compressor of the variable-frequency two-stage heat pump water heater, it is 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 two-stage variable frequency two-stage compression heat pump water heater also has a coupling problem between the operating frequency of the low-pressure stage compressor and the operating frequency of the high-pressure stage compressor.

Summary of the invention

The object of the present invention is to overcome the deficiencies of the prior art to provide a two-stage variable frequency two-stage compression heat pump water heater frequency dynamic optimization and control method, which can dynamically adjust the low voltage according to the user's heat demand and the outdoor temperature of the heat pump water heater and the temperature of the water tank. The operating frequency of the inverter compressor is adjusted according to the optimal intermediate temperature of the heat pump water heater refrigeration system. The operating frequency of the high-pressure inverter compressor is minimized, so that the total energy consumption of the heat pump water heater is minimized and the energy saving effect is achieved.

In order to achieve the above object, the present invention is achieved by the present invention, which is a frequency dynamic 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 comprises a low-voltage inverter compressor and a low-pressure compressor. Exhaust gas temperature sensor, high pressure stage variable frequency 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 voltage level electronics Expansion valve, evaporator and outdoor temperature sensor; characterized in that the operating frequency of the low-pressure stage inverter compressor and the high-pressure stage inverter compressor is dynamically optimized during the whole operation of the heat pump water heater, so that the total energy consumption of the heat pump water heater during the whole operation process is minimized. The dynamic optimization adjustment method of the operating frequency of the low-voltage inverter compressor and the high-voltage inverter compressor is as follows:

(a) Establish the relationship between the heat pump water heater with the outdoor ambient temperature T ₁ and the actual temperature T _{2 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. I: T ₃ =F(T ₁ , T ₂ );

(b) Establish the relationship between the instantaneous heat quantity q of the heat pump water heater and the outdoor ambient temperature T ₁ , the actual temperature T _{2 of the} water tank, and the operating frequency f _{a of the} low-voltage stage inverter compressor: II=q=E(T ₁ , T ₂ , f _a ); according to the relationship II, the expression III of the total calorific value Q in the whole running time t of the heat pump water heater can be obtained:

(c) Establish _a relationship between the instantaneous energy consumption p of the heat pump water heater and the outdoor ambient temperature T ₁ , the actual temperature T _{2 of the} water tank, and the operating frequency f _{a of the} low-voltage inverter compressor: IV=p=F(T ₁ , T ₂ , f _a ); according to the relationship IV, the expression V of the total energy consumption P in the whole running time t of the heat pump water heater can be obtained:

(d) The user sets the specific time t _{0 of} water and the water temperature T of the water tank. The controller detects the actual temperature T _{2 of the} current water tank and calculates the required total heating capacity Q. The minimum energy consumption P of the heat pump water heater is the minimum. The value, according to Expression III and Expression V, is calculated according to the relationship between the operating frequency f _a of the low-voltage inverter compressor and the running time t during the whole operation. VI: f _a =F(t), the heat pump water heater is in the whole running process. Dynamically adjust the operating frequency f _{a of the} low-voltage inverter compressor according to the relationship VI;

(e) The controller detects the outdoor ambient temperature T ₁ , the actual temperature T _{2 of the} water tank, 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 to detect the intermediate temperature sensor. The actual intermediate temperature approaches the value of the calculated optimum intermediate temperature T ₃ .

In the technical solution, in the whole operation process of the heat pump water heater, the relationship VI is simplified to obtain a simplified adjustment method of the operating frequency of the temperature-segment, non-continuous low-voltage stage inverter compressor, and the high-voltage inverter compressor The working frequency is adjusted accordingly, as follows:

(a) Set the operating frequency of the low-voltage inverter compressor f _a : according to the difference between the set water temperature T and the initial water temperature T ₀ of the water tank, divide the heating process into n segments, n≥2, and each temperature rise range is 2- 15 ° C, preferably the temperature rise is 5 ° C, in each temperature rise section low-pressure stage inverter compressors use different operating frequencies f _ai ;

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

(c) The controller detects the outdoor ambient temperature T ₁ , the current actual water temperature T _{2 of the} water tank, the specific water time t ₀ set by the user, and the set water temperature T of the water tank, and sets the lowest frequency of the low-pressure stage inverter compressor. The initial value of f _d is 30 Hz, and the initial value of the highest frequency f _g of the low-voltage inverter compressor is 80 Hz;

(d) The controller calculates the time t _s between the current time and the specific water time t ₀ set by the user, and calculates the water temperature of the water tank to reach the set temperature T according to the expression III, the expression V and the calculation formula VII. It takes time t _j , such as |t _s -t _j |≤5min, which indicates that the operating frequency of the low-voltage inverter compressor is reasonable, and the low-voltage inverter compressor 1 starts to work; if t _s -t _j ≥5min , the maximum frequency f _{g of the} low-voltage inverter compressor is reduced by 1 Hz each time until it satisfies |t _s -t _j | ≤ 5min, if the requirement is still not met when the f _{g is} reduced to 30 Hz, then the low-voltage frequency conversion compression is delayed. The start time of the machine and the high-voltage inverter compressor, the delay time is calculated according to the low-voltage inverter compressor always running at 30Hz frequency; if t _s -t _j ≤-5min, the lowest frequency of the low-voltage inverter compressor f _{d is} calculated again by increasing 1 Hz every time until |t _s -t _j | ≤ 5min, if the requirement of f _{d is} increased to 80 Hz, the low-pressure inverter compressor maintains a fixed frequency during the whole operation of the heat pump water heater. On the basis of 80Hz, increase 1Hz each time Sub-calculation until the requirements are met; if the calculated operating frequency of the low-voltage inverter is greater than the operating upper-frequency protection frequency of the low-pressure inverter installed by the heat pump water heater, the low-voltage inverter compressor operates at the upper protection frequency; The upper limit protection frequency is generally 100 Hz;

In the technical solution, the operating frequency f _ai of the low-pressure stage variable frequency compressor of each temperature rise section of the water tank can be simplified by the quadratic curve f _ai =ai ² +bi+c.

In the present technical solution, the initial value of the lowest frequency f _d of the low-voltage stage inverter compressor ranges from 10 to 40 Hz, and the initial value of the highest frequency f _g ranges from 60 to 100 Hz.

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 dynamically optimizes the working frequency of the low-pressure compressor and the high-pressure compressor during the whole operation process, so that the total energy consumption of the whole operation process is minimized. .

DRAWINGS

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

Specific embodiment 1

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.

The two-stage variable frequency two-stage compression heat pump water heater includes a low-pressure stage variable frequency compressor, a low-pressure stage compressor exhaust temperature sensor 2, a high-pressure stage inverter compressor 3, a high-pressure stage compressor exhaust temperature sensor 4, a controller 5, and a water tank sensor 6 , water storage tank 7, condenser 8, high-pressure stage electronic expansion valve 9, intercooler temperature sensor 10, intercooler temperature sensor 11, low-pressure stage electronic expansion valve 12, evaporator 13 and outdoor temperature sensor 14; low-voltage stage variable frequency compression The dynamic optimization adjustment method of the operating frequency of the machine 1 and the high-voltage inverter compressor 3 is as follows:

(a) Establish the relationship between the heat pump water heater with the outdoor ambient temperature T ₁ and the actual temperature T _{2 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: T ₃ =F(T ₁ , T ₂ );

(b) establishing _a relationship between the instantaneous heating quantity q of the heat pump water heater and the outdoor ambient temperature T ₁ , the actual temperature T _{2 of the} water tank 7, and the operating frequency f _{a of the} low-voltage stage inverter 1 : q=E(T ₁ , T ₂ , f _a ); according to the relationship II, the expression III of the total calorific value Q in the whole running time t of the heat pump water heater can be obtained:

(c) establishing _a relationship between the instantaneous energy consumption p of the heat pump water heater and the outdoor ambient temperature T ₁ , the actual temperature T _{2 of the} water tank 7, and the operating frequency f _{a of the} low-voltage inverter compressor 1 : IV=p=F(T ₁ , T ₂ , f _a ); according to the relationship IV, the expression V of the total energy consumption P in the whole running time t of the heat pump water heater can be obtained:

(d) The user sets the specific time t _{0 of the} water and the water temperature T of the water tank, the controller 5 detects the actual temperature T _{2 of the} current water tank 7, and calculates the required total heating capacity Q, so that the total energy consumption P of the heat pump water heater is the minimum during the entire operation process. As the target value, according to Expression III and Expression V, the relationship between the operating frequency f _a of the low-voltage inverter compressor 1 and the running time t during the entire operation is calculated as VI: f _a = F(t), and the heat pump water heater is During the whole operation process, the operating frequency f _{a of the} low-voltage inverter compressor 1 is dynamically adjusted according to the relationship VI;

(e) The controller 5 detects the outdoor ambient temperature T ₁ , the actual temperature T _{2 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 stage inverter 3 to make the middle The actual intermediate temperature detected by the temperature sensor 11 approaches the value of the calculated optimum intermediate temperature T ₃ .

In the present embodiment, during the entire operation of the heat pump water heater, the relationship VI is simplified to obtain a simplified adjustment method for the operating frequency of the temperature-segment, non-continuous low-voltage inverter compressor 1, and the high-voltage inverter compressor 3 The working frequency is adjusted accordingly, as follows:

(a) Setting the operating frequency f _{a of the} low-voltage inverter compressor 1 : According to the difference between the set water temperature T of the water tank 7 and the initial water temperature T ₀ , the temperature rising process is divided into n segments, n ≥ 2, and each temperature rise range is 2-15 ° C, preferably the temperature rise is 5 ° C, in each temperature rise section low-voltage stage inverter 1 uses a different operating frequency f _ai ;

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

(c) The controller 5 detects the outdoor ambient temperature T ₁ , the current actual water temperature T _{2 of the} water tank 7, the specific water time t ₀ set by the user, and the set water temperature T of the water tank 7, and sets the low-pressure stage inverter compressor The initial value of the lowest frequency f _d of 1 is 30 Hz, and the initial value of the highest frequency f _g of the low-voltage inverter compressor 1 is 80 Hz;

(d) The controller 5 calculates the time t _s between the current time and the specific water time t ₀ set by the user, and calculates the water temperature of the water tank 7 to reach the set temperature T according to Expression III, Expression V and Calculation Formula VII. The running time t _j , such as |t _s -t _j | ≤ 5min, indicates that the operating frequency of the low-voltage inverter compressor 1 in each temperature rise section is set properly, and the low-voltage inverter compressor 1 starts to work; for example, t _s -t _j ≥ 5min, then calculate the maximum frequency f _{g of the} low-voltage inverter compressor 1 by 1Hz every time until it satisfies |t _s -t _j | ≤ 5min, if the requirement is still not met when f _g drops to 30Hz, then the delay When the low-voltage inverter compressor 1 and the high-voltage inverter compressor 3 start to start, the delay time is calculated according to the low-voltage inverter compressor 1 always running at 30Hz; if t _s -t _j ≤-5min, the low voltage will be The lowest frequency f _{d of the} inverter compressor 1 is calculated again by increasing 1 Hz each time until |t _s -t _j | ≤ 5min is satisfied. If the f _{d is} increased to 80 Hz, the requirements are still not met, and the low-pressure frequency conversion of the heat pump water heater during the whole operation process. Compressor 1 maintains a fixed frequency and will be based on 80 Hz each time The high 1Hz is calculated again until the requirement is met; if the calculated operating frequency of the low-voltage inverter compressor 1 is greater than the operating upper limit protection frequency of the low-pressure compressor 1 set by the heat pump water heater, the low-voltage inverter compressor 1 is pressed according to the upper limit. Protection frequency operation; the upper protection frequency is generally 100Hz;

(e) The controller 5 detects the outdoor ambient temperature T ₁ , the actual temperature T _{2 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 stage inverter 3 to make the middle The actual intermediate temperature detected by the temperature sensor 11 approaches the value of the calculated optimal intermediate temperature T ₃ ; the lower limit protection frequency of the operating frequency f _b of the high-voltage stage inverter 3 is 20 Hz, and the upper limit protection frequency is 100 Hz, that is, when When the operating frequency f _{b of the} high-voltage stage inverter 3 is required to be lower than 20 Hz, it is operated at 20 Hz, and when it is higher than 100 Hz, it is operated at 100 Hz.

In the present embodiment, the operating frequency f _ai of the low-pressure stage inverter 1 of each temperature rise section of the water tank 7 can be simplified by the quadratic curve f _ai =ai ² +bi+c.

In the present embodiment, the initial value of the lowest frequency f _d of the low-voltage stage inverter compressor 1 ranges from 10 to 40 Hz, and the initial value of the highest frequency f _g ranges from 60 to 100 Hz.

In the present embodiment, the low-voltage stage inverter compressor 1 and the high-voltage stage inverter compressor 3 may both be an AC variable frequency compressor or a DC speed control 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

A frequency dynamic optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater, the two-stage variable frequency two-stage compression heat pump water heater comprises a low-voltage stage variable frequency compressor (1), a low-pressure stage compressor exhaust temperature sensor (2), a high-voltage stage frequency conversion 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 heat pump water heater throughout the operation, low pressure The dynamic frequency optimization of the operating frequency of the inverter compressor (1) and the high-voltage inverter compressor (3) minimizes the total energy consumption of the heat pump water heater during the whole operation process; the low-voltage inverter compressor (1) and the high-voltage inverter compressor ( 3) The dynamic optimization of the operating frequency is as follows:

Establish the relationship between the heat pump water heater with the outdoor ambient temperature T 1 and the actual temperature T 2 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 1 , T 2 );

Establish the relationship between the instantaneous heating capacity q of the heat pump water heater and the outdoor ambient temperature T 1 , the actual temperature T 2 of the water tank (7) and the operating frequency f a of the low-voltage inverter (1): II=q=E(T 1 , T 2 , f a ); according to the relationship II, the expression III of the total calorific value Q in the whole running time t of the heat pump water heater can be obtained:

Establish the relationship between the instantaneous energy consumption p of the heat pump water heater and the outdoor ambient temperature T 1 , the actual temperature T 2 of the water tank (7) and the operating frequency f a of the low-voltage inverter (1): p=F (T 1 , T 2 , f a ); according to the relationship IV, the expression V of the total energy consumption P in the whole running time t of the heat pump water heater can be obtained:

The user sets the specific time t 0 of the water and the water temperature T of the water tank. The controller (5) detects the actual temperature T 2 of the current water tank (7), calculates the required total heating capacity Q, and uses the total energy consumption of the heat pump water heater throughout the running process. The minimum value as the target value is calculated according to Expression III and Expression V. The relationship between the operating frequency f a of the low-voltage inverter (1) and the running time t during the whole operation is VI: f a =F(t), The heat pump water heater dynamically adjusts the operating frequency f a of the low-voltage inverter (1) according to the relationship VI during the whole operation process;

The controller (5) detects the outdoor ambient temperature T 1 , the actual temperature T 2 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). the intermediate temperature sensor (11) detecting the actual temperature approaches the intermediate value calculated optimal intermediate temperature T 3 of the.
The frequency dynamic optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater according to claim 1, characterized in that in the whole operation process of the heat pump water heater, the relationship VI is simplified to obtain a sub-temperature section and a discontinuous low pressure. The operating frequency of the inverter compressor (1) is simplified and the operating frequency of the high-voltage inverter (3) is adjusted accordingly. The specific method is as follows:

(a) Set the operating frequency f a of the low-voltage inverter (1) in sections: according to the difference between the set water temperature T of the water tank (7) and the initial water temperature T 0 , divide the heating process into n segments, n ≥ 2, The temperature rise range of each section is 2-15 ° C, preferably the temperature rise is 5 ° C. In each temperature rise section, the low-voltage stage inverter compressor (1) adopts different working frequencies f ai ;

(b) According to the temperature rise segmentation of the water tank (7), the operating frequency f ai of the low-pressure stage inverter compressor (1) in each temperature rise section is distributed by the arithmetic progression to obtain the formula VII of the frequency f ai of each temperature rise section. :f ai =f g -(f g -f d )(i-1)/(n-1), in formula VII, 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;

(c) The controller (5) detects the outdoor ambient temperature T 1 , the current actual water temperature T 2 of the water tank (7), the specific water time t 0 set by the user, and the water temperature T of the set water tank (7), and is set. The initial value of the lowest frequency f d of the fixed low-voltage inverter (1) is 30 Hz, and the initial value of the highest frequency f g of the low-voltage inverter (1) is 80 Hz;

(d) The controller (5) calculates the time t s between the current time and the specific water time t 0 set by the user, and calculates the water temperature of the water tank (7) according to the expression III, the expression V and the calculation formula VII. Set the required time t j for the temperature T operation, such as |t s -t j | ≤ 5min, indicating that the operating frequency setting of the low-voltage inverter compressor (1) is reasonable, and the low-voltage inverter compressor 1 starts to work. If t s -t j ≥5min, calculate the highest frequency f g of the low-voltage inverter compressor (1) by 1Hz every time until it reaches |t s -t j |≤5min, if f g drops to 30Hz When the requirements are still not met, the time for starting the start-up of the low-voltage inverter (1) and the high-voltage inverter (3) is delayed. The calculation of the delay time is calculated according to the low-voltage inverter (1) running at 30 Hz. If t s -t j ≤-5min, calculate the lowest frequency f d of the low-voltage inverter compressor (1) by 1Hz each time until |t s -t j |≤5min, if f d is increased to At 80Hz, the requirements are still not met. During the whole operation of the heat pump water heater, the low-voltage inverter (1) maintains a fixed frequency and will be at 80Hz. On the basis of each increase of 1Hz, until the requirements are met; if the calculated operating frequency of the low-voltage inverter (1) is greater than the operating upper limit of the low-voltage inverter (1) set by the heat pump water heater, Then the low-voltage inverter compressor (1) operates according to the upper limit protection frequency; the upper limit protection frequency is generally 100 Hz;

(e) The controller (5) detects the outdoor ambient temperature T 1 , the actual temperature T 2 of the water tank (7), calculates the optimal intermediate temperature T 3 according to the relationship I, and adjusts the operation of the high-voltage inverter compressor (3). The frequency f b causes the actual intermediate temperature detected by the intermediate temperature sensor (11) to approach the value of the calculated optimum intermediate temperature T 3 .
The frequency dynamic optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater according to claim 2, characterized in that the operating frequency f ai of the low-pressure stage variable frequency compressor (1) of each temperature rise section of the water tank (7) You can simplify the relational VI by the quadratic curve f ai =ai 2 +bi+c.
The frequency dynamic optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater according to claim 1, 2, 3, characterized in that the initial value of the lowest frequency f d of the low-voltage stage inverter compressor (1) is 10-40 Hz, the initial value of the highest frequency f g ranges from 60 to 100 Hz.
The frequency dynamic optimization and control method for a two-stage variable frequency two-stage compression heat pump water heater according to claim 1, 2, 3, characterized in that the low-voltage stage inverter compressor (1) and the high-voltage stage inverter compressor (3) are both For AC inverter compressor or DC speed control compressor.