A method, device, medium and computer equipment for measuring water pump current

Abstract

The present invention provides a water pump current measurement method, device, medium and computer equipment, the method comprising: determining the corresponding specified carrier frequency f based on the actual operating frequency F of the water pump set ; Based on the specified carrier frequency f set Calculate the time difference ΔT; calculate the current sampling time point T u1 ; At the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampling current i t , calculate the effective current I provided to the single-phase motor; this method can accurately obtain the AC usage of the single-phase motor by measuring the DC power in the bus at a predetermined current sampling time point, avoiding the influence of the high-frequency carrier on the sampling accuracy of the sampling resistor. And using the sampling resistor to detect the working current of the single-phase motor can effectively reduce the production cost of the motor and inverter and improve the enterprise efficiency compared with the use of Hall sensor to measure the current.

Description

Technical Field

[0001] The present invention relates to the technical field of water pump control, and more specifically, to a water pump current measurement method, device, medium and computer equipment. Background Art

[0002] In the prior art, a single-phase motor in a water pump usually needs to be controlled by a high-frequency carrier current, such as Figure 4 As shown, an existing water pump driving circuit specifically includes a rectifier module for converting direct current into alternating current, and an inverter for converting direct current into alternating current.

[0003] In order to ensure the stable operation of the water pump, the switching frequency of the inverter cannot be too low. If the switching frequency is too low, it will affect the output waveform of the inverter and may generate a rough output current waveform, requiring a more complex filtering system to suppress these harmonics. Secondly, the switching frequency of the inverter cannot be too high. A high switching frequency requires faster switching speed and lower switching loss, which requires higher performance of power semiconductor components. A high switching frequency will generate more high-frequency harmonics, which are likely to cause electromagnetic interference to surrounding equipment.

[0004] During the operation of the water pump, in order to monitor the operating status of the water pump, it is also necessary to determine whether the water pump is operating normally by measuring the current in the water pump. If the current exceeds the rated value, it may be due to pipeline blockage, valve abnormality, impeller wear or pump jam. Timely detection can avoid damage to the water pump due to overload. When idling, there is no water flow through the water pump, the load decreases sharply, and the current value is usually lower than the normal operating value. Idling can cause overheating or mechanical damage to the pump body. Current detection can trigger an alarm or automatic shutdown protection. For a single-phase water pump, its operation process requires the use of alternating current. If a sampling resistor is directly set on its power supply line to detect its current, the resistor itself and the connecting line, PCB layout, etc. will form a certain capacitance. These parasitic capacitors will filter the current waveform at high frequencies, weaken the signal change, and increase the measurement error. The faster the current changes, the more obvious the influence of the parasitic capacitance, which makes the change of the voltage signal lag and produce errors. Under high frequency conditions, the current tends to flow through the surface of the conductor. This phenomenon is called the skin effect. The skin effect makes the current distribution in the resistor uneven, and the current is concentrated in the surface area of ​​the resistor, resulting in a reduction in the effective area of ​​the resistor, thereby increasing the total resistance of the resistor, further affecting the current measurement. Unlike the resistor sampling circuit, the Hall sensor measures the current by inducing a magnetic field, which is not affected by the current frequency. The Hall effect is essentially a non-contact measurement method that can maintain a good response within a wide frequency band. Therefore, under high-frequency conditions, the response of the Hall sensor is more stable and can accurately reflect the changes in high-frequency current without being affected by parasitic inductance, capacitance and skin effect. However, the expensive price of the Hall sensor will lead to an increase in the cost of motor equipment and affect the economic benefits of the enterprise. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a water pump current measurement method, device, medium and computer equipment to overcome the shortcomings of the existing sampling resistors that have errors when measuring the high-frequency switching current of a single-phase motor.

[0006] The above technical objectives of the present invention are achieved through the following technical solutions: a water pump current measurement method, applied to a frequency converter and a single-phase water pump; the frequency converter is used to invert the direct current on the bus to generate three-phase alternating current, the two ends of the single-phase water pump are respectively electrically connected to any two of the three output ends of the frequency converter, and at least one of the busbars is also provided with a sampling resistor for detecting current; the method comprises:

[0007] Based on the actual operating frequency F of the water pump, determine the corresponding specified carrier frequency f set ;

[0008] Based on the specified carrier frequency f setCalculate the time difference ΔT, which is the first turn-on time point T of the first phase PWM signal. 1 and the second turn-on time point T of the second phase PWM signal 2 time interval;

[0009] Based on the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off;

[0010] At the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

[0011] In one embodiment, the corresponding specified carrier frequency f is determined based on the actual operating frequency F of the water pump. set , specifically including:

[0012] Get the maximum operating frequency F of the water pump max ; Divide the operating frequency of the water pump into several operating frequency intervals; determine a corresponding standard carrier frequency for each operating frequency interval;

[0013] Based on the actual operating frequency F of the water pump max The specified carrier frequency f set .

[0014] In one embodiment, the operation frequency of the water pump is divided into several operation frequency intervals, specifically including:

[0015] The operating frequency of the water pump is divided into four operating frequency intervals: 0~F 1 、F 1 ~F 2 、F 2 ~F 3 and F 3 ~F max ; Among them, F 1 、F 2 、F 3 Satisfaction: F 2 >F 1 +F min ; F3 >F 2 +F min ; F max >F 3 +F min ; F min is the minimum frequency deviation;

[0016] The standard carrier frequency specifically includes: a first standard carrier frequency f 1 , the second standard carrier frequency f 2 , the third standard carrier frequency f 3 And the fourth standard carrier frequency f 4 , and satisfy f 4 >f 3 >f 2 >f 1 ; The first standard carrier frequency f 1 And the operating frequency range 0 ~ F 1 Correspondingly, the second standard carrier frequency f 2 and operating frequency range F 1 ~F 2 Correspondingly, the third standard carrier frequency f 3 and operating frequency range F 2 ~F 3 Correspondingly, the fourth standard carrier frequency f 4 and operating frequency range F 3 ~F max corresponding;

[0017] The specified carrier frequency f is determined based on the operating frequency interval to which the actual operating frequency F of the water pump belongs and the standard carrier frequency corresponding to the interval. set , specifically including:

[0018] In F∈(0,F 1 ), f set =f 1 ;

[0019] In F∈(F 1 ,F 2 ), f set =f 2 ;

[0020] In F∈(F 2 ,F 3 ), f set =f 3 ;

[0021] In F∈(F 3 ,F max ), f set =f4 .

[0022] In one embodiment, the carrier frequency f set Calculate the time difference ΔT, specifically including:

[0023] The first opening time point T is calculated by the following formula 1 And the second opening time point T 2 :

[0024]

[0025] Among them, K g is the SVPWM modulation coefficient; θ is the SVPWM phase angle; T s =1 / f set ;

[0026] According to the first opening time point T 1 And the second opening time point T 2 Calculate the time difference ΔT, specifically including: ΔT = T 2 -T 1 .

[0027] In one embodiment, the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , specifically including:

[0028] Determine the time difference ΔT and the bus current stabilization time T st And the sampling chip current conversion time T sa Whether: ΔT>T st +T sa , if so, then T u1 =T 1 +T st .

[0029] In one embodiment, at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , specifically including:

[0030] If ΔT>T st +T sa , then at the current sampling time point T u1 Detect the current in the sampling resistor and obtain the corresponding sampling current i t ;

[0031] If ΔT≤T st +T sa , then use the sampling current i of the previous cycle t-1 As the sampling current i at the current time point t :i t =i t-1 .

[0032] In one embodiment, the sampling current i t , calculating the effective current I provided to the single-phase motor, specifically comprising:

[0033] Within a predetermined time, a plurality of the sampling currents i are obtained in sequence. t ; Calculate the effective current I of a single-phase motor using the following formula:

[0034] A water pump current measuring device, comprising:

[0035] Carrier frequency determination unit: used to determine the corresponding specified carrier frequency f based on the actual operating frequency F of the water pump set ;

[0036] The time difference calculation unit is used to calculate the time difference based on the specified carrier frequency f set Calculate the time difference ΔT, which is the first turn-on time point T of the first phase PWM signal. 1 and the second turn-on time point T of the second phase PWM signal 2 time interval;

[0037] A time point calculation unit is used to calculate the time point based on the time difference ΔT and the first opening time point T 1 And the preset bus current stabilization time T st , calculate the current sampling time point T u1 , the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off;

[0038] Current calculation unit: used to calculate the current at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

[0039] A computer-readable storage medium stores a computer program, which implements the steps of the above method when executed by a processor.

[0040] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0041] In summary, the present invention has the following beneficial effects: a method, device, medium and computer for measuring water pump current, the method comprising: determining the corresponding specified carrier frequency f based on the actual operating frequency F of the water pump set ; Based on the specified carrier frequency f set Calculate the time difference ΔT; based on the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 At the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I provided to the single-phase motor; by using the method of the present application, by measuring the size of the DC power in the bus at a predetermined current sampling time point, the AC power usage in the single-phase motor can be accurately obtained, avoiding the influence of the high-frequency carrier on the sampling accuracy of the sampling resistor. And using the sampling resistor to detect the working current of the single-phase motor can effectively reduce the production cost of the motor and the inverter and improve the enterprise efficiency compared to using the Hall sensor to measure the current. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 A flow chart of a water pump current measurement method of the present invention;

[0043] Figure 2 A structural diagram of a water pump current measuring device in an embodiment of the present invention;

[0044] Figure 3 is an internal structure diagram of a computer device in an embodiment of the present invention;

[0045] Figure 4 Schematic diagram of the connection of a water pump, an inverter and a sampling resistor in an embodiment of the present invention;

[0046] Figure 5 is a schematic diagram of the structure of an inverter switch circuit in an embodiment of the present invention;

[0047] Figure 6 It is a phase sector diagram of SVPWM technology;

[0048] Figure 7 It is a schematic diagram of voltage vector synthesis of SVPWM technology;

[0049] Figure 8 The PWM signal opening sequence timing diagram for each sector;

[0050] Fig. 9 This is the PWM voltage vector control timing diagram corresponding to sector I.

[0051] In the figure: 1. Carrier frequency determination unit; 2. Time difference calculation unit; 3. Time point calculation unit; 4. Current calculation unit. DETAILED DESCRIPTION

[0052] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. Several embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0053] In the embodiments of the present application, "at least one" refers to one or more, and "plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and subsequent associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0054] Those of ordinary skill in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented in a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0055] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0056] In several embodiments provided in the present application, any function can be stored in a computer-readable storage medium if it is implemented in the form of a software functional unit and sold or used as an independent product. Based on this understanding, the technical solution of the present application can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium, including several instructions for enabling a device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0057] The above is only a specific implementation of the present application. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. The protection scope of the present application should be based on the protection scope of the claims.

[0058] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments.

[0059] Embodiment 1

[0060] In order to facilitate the understanding of the technical solution of the present application, the relevant knowledge and content of the present application are briefly described first: when using an inverter to convert DC power into AC power to drive a motor to work, SVPWM technology is usually used to control the output end of the inverter to generate three-phase power, such as Figure 5 As shown in the figure, it is a circuit diagram of an inverter in the prior art. The inverter has three bridge arms: bridge arm a, bridge arm b, and bridge arm c. Each bridge arm has two switches, which are used to control the conduction or disconnection of the upper bridge arm and the lower bridge arm respectively. The SVPWM algorithm actually calculates when the six switches of the inverter shown in the figure above are turned on and when they are cut off. By controlling the conduction and disconnection of these six switches, the DC voltage source V on the left is coordinated with the dc , the inverter can generate the required sinusoidal voltage on the three loads on the right. Secondly, in the SVPWM algorithm, the states of the upper and lower switches on each bridge arm are complementary, that is, when the switch V T1 When conducting, V T4 is in the off state; when the switch V T3 When conducting, V T6 is in the off state; when the switch V T5 When conducting, V T2It is in the disconnected state, and vice versa. Then by defining the switching function S of the bridge arm x (x=a,b,c), which can represent the conduction state of the bridge arm, S x =1 means that the upper arm of the bridge is turned on and the lower arm is turned off; S x =0 means that the lower arm of the bridge arm is turned on and the upper arm is turned off. Then a vector can be used to represent the switch states of the three bridge arms, for example: (1,0,0), which means that the upper arm of bridge arm a is turned on and the lower arm is turned off, the upper arm of bridge arm b is turned off and the lower arm is turned on, and the upper arm of bridge arm c is turned off and the lower arm is turned on. Since the three output terminals of the three-phase power are placed 120° apart in space, the three output terminals together form a spatial voltage vector.

[0061] like Figure 6 Schematic diagram of the spatial voltage vector generated by different switching states of the bridge arm; Figure 6 The voltage values ​​corresponding to the vertices of the hexagon in are calculated using the following formula, where: Indicates the position rotated 60° counterclockwise from the axis. Indicates the position rotated 120° counterclockwise from the axis.

[0062]

[0063] The above voltage vectors include two zero vectors V 0 、V 7 , and six non-zero vectors V 1 、V 2 、V 3 、V 4 、V 5 、V 6 By using six voltage vectors with fixed directions and amplitudes and controlling the switching period of each voltage vector, it is possible to synthesize an output voltage vector V with any angle and amplitude in space. δ , and the more times it is synthesized, the smoother the output voltage trajectory will be.

[0064] like Figure 7 As shown, u a 、u b 、u c After synthesis, the synthetic voltage vector V δ :

[0065]

[0066] Among them, e -j120° It means that it rotates 120° clockwise starting from phase A; e j120° It means that the counterclockwise rotation is 120° starting from phase A, ω e is the three-phase electrical angular frequency.

[0067] like Figure 8 As shown, it is the synthetic voltage vector V δ In the process of counterclockwise rotation, when passing through each sector, the upper bridge arm needs to form a time sequence of PWM waveforms (the lower bridge arm and the upper bridge arm are complementary waveforms). Observing the sequence, it can be seen that there are two time periods in each sector, and only one upper bridge arm is in the open state during the time period. That is, the second time period and the second to last time period in each sector. For example, in the second time period in the first sector, PWMA is turned on and becomes a high level, but PWMB and PWMC are both low levels; for another example, in the second time period in the second sector, PWMB is turned on and becomes a high level, but PWMA and PWMC are both low levels.

[0068] According to the loop current method, when the current flows forward from the upper bridge arm, there must be a current of the same magnitude but opposite direction flowing back to the negative pole of the DC power supply from the lower bridge arm to form a loop. If this time period is regarded as a balanced state, the positive output current on the busbar during this time period can be regarded as the current flowing into the single-phase motor. Therefore, how to accurately collect current from this time period has become the main obstacle to accurately measuring the working current of the single-phase motor.

[0069] In order to solve the above problems, the present invention provides a water pump current measurement method, which is applied to Figure 4 The inverter and the single-phase water pump shown in the figure; the inverter is used to invert the DC power on the bus to generate three-phase AC power, the two ends of the single-phase water pump are respectively electrically connected to any two of the three output ends of the inverter, and at least one of the busbars is also provided with a sampling resistor for detecting current; Figure 1 As shown, the method includes:

[0070] S1. Determine the corresponding specified carrier frequency f based on the actual operating frequency F of the water pump set ;

[0071] S2, based on the specified carrier frequency f set Calculate the time difference ΔT, which is the first turn-on time point T of the first phase PWM signal. 1 and the second turn-on time point T of the second phase PWM signal 2 time interval;

[0072] S3, based on the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1, the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off;

[0073] S4, at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

[0074] Specifically, in this application, it is first necessary to determine the actual operating frequency F of the water pump; based on the actual operating frequency F of the water pump, determine the corresponding specified carrier frequency f set , the purpose is to make the specified carrier frequency f set Match it with the actual operating frequency F of the water pump to avoid the carrier frequency being too low affecting the smoothness and stability of the output waveform, and to avoid the carrier frequency being too high causing the switching device to be in a high load state for a long time affecting its service life, or the switching time being too short affecting the current sampling accuracy.

[0075] The water pump used in this application is a single-phase water pump, but in order to improve the versatility of the inverter, the inverter outputs three-phase electricity, so the two ends of the single-phase water pump are connected to two phases of the three-phase electricity to ensure that the single-phase water pump can work normally. When actually measuring the current, the time difference ΔT here refers to the first opening time point T of the first phase PWM signal in any sector when the seven-segment control method of SVPWM technology is used to generate three-phase electricity. 1 and the second turn-on time point T of the second phase PWM signal 2 In the seven-segment control method, the time length corresponding to each sector is the same. When the sector is divided into seven stages, the duration of each stage is also equal. Therefore, in the actual control process, the time difference ΔT can be determined by measuring the change of current or the corresponding time based on frequency measurement.

[0076] Since the current pulse does not change suddenly in the actual conversion process, but gradually changes, the bus current stabilization time T is also required in the actual operation process. st , and the sampling chip current conversion time T sa The current can only be sampled when the current rises and reaches stability after a predetermined time. Therefore, it is necessary to determine whether the time difference ΔT is greater than the bus current stabilization time T st , and the sampling chip current conversion time T sa The sum of the time difference ΔT is longer than the bus current stabilization time Tst , and the sampling chip current conversion time T sa If the sum is longer, then we can start from the first opening time point T 1 Start and postpone the bus current stabilization time T st , to determine the current sampling time point T u1 , and the remaining time length in the time difference ΔT is also longer than the sampling chip current conversion time T sa Longer, so there is sufficient time to ensure that the sampling chip can accurately collect the current data within this time period.

[0077] Since the PWM carrier signal is periodic and is generated all the time, the actual current data can be calculated by collecting current sample points multiple times within a predetermined time period.

[0078] In summary, this application proposes a method for calculating the current of a single-phase motor based on a sampling resistor. This application uses the principle of SVPWM technology to accurately obtain the usage of AC power in a single-phase motor by measuring the size of the DC power in the bus at a predetermined current sampling time point, thereby avoiding the influence of the high-frequency carrier on the sampling accuracy of the sampling resistor. In addition, the use of a sampling resistor to detect the working current of a single-phase motor can effectively reduce the production cost of the motor and the inverter and improve the efficiency of the enterprise compared to using a Hall sensor to measure the current.

[0079] In one embodiment, the corresponding specified carrier frequency f is determined based on the actual operating frequency F of the water pump. set , specifically including:

[0080] Get the maximum operating frequency F of the water pump max ; Divide the operating frequency of the water pump into several operating frequency intervals; determine a corresponding standard carrier frequency for each operating frequency interval;

[0081] Based on the actual operating frequency F of the water pump max The specified carrier frequency f set .

[0082] Specifically, dividing the frequency intervals according to the operating frequency of the water pump and assigning a standard carrier frequency to each interval can avoid the energy waste that may be caused by a fixed carrier frequency. When operating at low frequency, using a lower carrier frequency can reduce high-frequency harmonics, thereby reducing electromagnetic interference. Matching the appropriate carrier frequency in different frequency intervals can optimize the electromagnetic compatibility of the system while meeting performance requirements. When operating at high frequency, a higher carrier frequency can generate a smoother output waveform, thereby improving the stability and control accuracy of the water pump operation; when operating at low frequency, appropriately reducing the carrier frequency can reduce the switching frequency and reduce the switching loss of the inverter switching elements.

[0083] In one embodiment, the operation frequency of the water pump is divided into several operation frequency intervals, specifically including:

[0084] The operating frequency of the water pump is divided into four operating frequency intervals: 0~F 1 、F 1 ~F 2 、F 2 ~F 3 and F 3 ~F max ; Among them, F 1 、F 2 、F 3 Satisfaction: F 2 >F 1 +F min ; F 3 >F 2 +F min ; F max >F 3 +F min ; F min is the minimum frequency deviation;

[0085] The standard carrier frequency specifically includes: a first standard carrier frequency f 1 , the second standard carrier frequency f 2 , the third standard carrier frequency f 3 And the fourth standard carrier frequency f 4 , and satisfy f 4 >f 3 >f 2 >f 1 ; The first standard carrier frequency f 1 And the operating frequency range 0 ~ F 1 Correspondingly, the second standard carrier frequency f 2 and operating frequency range F 1 ~F 2 Correspondingly, the third standard carrier frequency f 3 and operating frequency range F 2 ~F3 Correspondingly, the fourth standard carrier frequency f 4 and operating frequency range F 3 ~F max corresponding;

[0086] The specified carrier frequency f is determined based on the operating frequency interval to which the actual operating frequency F of the water pump belongs and the standard carrier frequency corresponding to the interval. set , specifically including:

[0087] In F∈(0,F 1 ), f set =f 1 ;

[0088] In F∈(F 1 ,F 2 ), f set =f 2 ;

[0089] In F∈(F 2 ,F 3 ), f set =f 3 ;

[0090] In F∈(F 3 ,F max ), f set =f 4 .

[0091] Specifically, in order to make the operating frequency of the water pump match the carrier frequency, the operating frequency of the water pump is first divided into several intervals, and a corresponding designated carrier frequency is preset for each frequency interval. When the water pump is running in the operating frequency interval, the designated carrier frequency is adjusted to the corresponding standard carrier frequency. In addition, in order to avoid the designated carrier frequency jumping back and forth when the operating frequency of the water pump runs at the critical point of the interval, affecting the accuracy of the technical solution, it is also necessary to use the minimum frequency deviation F min , limit the operating frequency range of the water pump.

[0092] When the pump speed increases, the following criteria apply:

[0093] In F∈(0,F 1 +F min ), f set =f 1 ;

[0094] In F∈(F 1 +F min ,F 2 +F min), f set =f 2 ;

[0095] In F∈(F 2 +F min ,F 3 +F min ), f set =f 3 ;

[0096] In F∈(F 3 +F min ,F max ), f set =f 4 .

[0097] That is to say, when the operating frequency of the water pump is rising, it is further higher than the critical point F min After that, the standard carrier frequency of the next interval will be adopted; when the operating frequency of the water pump decreases, the original interval demarcation point is still used to determine the specified operating frequency f set Since the method in this application is executed periodically based on the carrier frequency, each variable refers to the variable in the current cycle, and the variable in the current cycle may also use the variable in the previous cycle. Specifically, before the cycle starts, an initial value needs to be set. The initial specified carrier frequency f set =16KHz.

[0098] In this embodiment, three operating frequency distinction points F are used. 1 、F 2 and F 3 , the operating frequency of the water pump is divided into four intervals, so each operating frequency interval will also have a corresponding standard carrier frequency, so that the water pump can run smoothly in this interval. This embodiment also provides a specific division method for a single-phase motor with a rated frequency of 60Hz, and explains the above interval division: the four operating frequency intervals of the operating frequency of the water pump are: 0~15Hz, 15Hz~25Hz, 25Hz~35Hz and 35Hz~60Hz; the minimum frequency deviation F min Specifically: 3Hz. The standard carrier frequency corresponding to each operating frequency range is specifically: the first standard carrier frequency f 1 =4KHz, the second standard carrier frequency f 2 =8KHz, the third standard carrier frequency f 3 =12KHz and the fourth standard carrier frequency f 4 =16KHz.

[0099] In one embodiment, the carrier frequency f set Calculating the time difference ΔT specifically includes: calculating the first opening time point T by the following formula 1 And the second opening time point T 2 :

[0100]

[0101] Among them, K g is the SVPWM modulation coefficient; θ is the SVPWM phase angle; T s =1 / f set ; The first opening time point T 1 And the second opening time point T 2 Calculate the time difference ΔT, specifically including: ΔT = T 2 -T 1 .

[0102] Time T s With the specified carrier frequency f set are reciprocals of each other, such as Fig. 9 As shown, T a 、T b Corresponding to the duration of the two basic voltage vectors, according to the technical principle of SVPWM, only Fig. 9 T a 、T b There is a voltage vector in two time periods. 1 、T 7 The voltage vector of the two stages is 0, and 2T 1 =T 7 PWM control is symmetrical along the time direction, T a Indicates the time span from when PWM1 pulse jumps to high level until PWM2 jumps to high level in the figure; T b In the figure, it represents the time span from when the PWM2 pulse jumps to a high level until when PWM3 jumps to a high level; if the starting point of a complete PWM sector is regarded as time 0, then the time length from time 0 to the time when the PWM1 pulse jumps to a high level should be T 1 That is to say, the time point when the PWM1 pulse jumps to a high level corresponds to T 1 The moment when the PWM2 pulse jumps to a high level is at T 1 Further increase T based on the time point a The duration of 2 In this embodiment, the time difference ΔT and T a Keep it equal in time.

[0103] In one embodiment, the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , specifically including:

[0104] Determine the time difference ΔT and the bus current stabilization time T st And the sampling chip current conversion time T sa Whether: ΔT>T st +T sa , if so, then T u1 =T 1 +T st .

[0105] Determine ΔT>T st +T sa The purpose is to ensure that the duration of the generated pulse electrical signal is sufficient to be detected by the detection component, so as to avoid affecting the final current calculation due to the detected current being not stable and accurate enough.

[0106] In one embodiment, at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , specifically including:

[0107] If ΔT>T st +T sa , then at the current sampling time point T u1 Detect the current in the sampling resistor and obtain the corresponding sampling current i t ;

[0108] If ΔT≤T st +T sa , then use the sampling current i of the previous cycle t-1 As the sampling current i at the current time point t :i t =i t-1 .

[0109] Specifically, if the duration of the high-level current is longer than the bus current stabilization time T st And the sampling chip current conversion time T sa The sum of the current in the sampling resistor can be detected after the bus current stabilizes to ensure that the collected current samples are sufficiently stable. st +T sa, indicating that this time is not enough for the current sampling chip to sample the current. Even if forced sampling is performed, it will affect the accuracy of the final detection result. Therefore, the sampling current value i in the previous cycle is used. t-1 As alternative sampling. In order to ensure the accuracy of current conversion, it is necessary to ensure that the ratio of actual sampling points to alternative sampling points is greater than 6:4, that is, the alternative sampling points cannot exceed 40% to ensure the accuracy of the final calculation result.

[0110] In one embodiment, the sampling current i t , calculating the effective current I provided to the single-phase motor, specifically comprising: obtaining a plurality of the sampled currents i in sequence within a predetermined time t ; Calculate the effective current I of a single-phase motor using the following formula:

[0111] Specifically, calculating the effective current I is to convert all the sampled currents i t The result of normalization as a characteristic vector and calculation by squaring and square root extraction can intuitively reflect the intensity of the detected current.

[0112] Embodiment 2

[0113] See also Figure 2 , a water pump current measuring device, the water pump current measuring device comprising:

[0114] Carrier frequency determination unit 1: used to determine the corresponding specified carrier frequency f based on the actual operating frequency F of the water pump set ;

[0115] Time difference calculation unit 2: used for calculating the time difference based on the specified carrier frequency f set Calculate the time difference ΔT, which is the first turn-on time point T of the first phase PWM signal. 1 and the second turn-on time point T of the second phase PWM signal 2 time interval;

[0116] A time point calculation unit 3 is used to calculate the time point based on the time difference ΔT and the first opening time point T 1 And the preset bus current stabilization time T st , calculate the current sampling time point T u1 , the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off;

[0117] Current calculation unit 4: used to calculate the current at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t, and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

[0118] For the specific definition of the water pump current measuring device, please refer to the definition of the water pump current measuring method above, which will not be repeated here. Each module in the above water pump current measuring device can be implemented in whole or in part by software, hardware and a combination thereof. The above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory of the computer device in the form of software, so that the processor can call and execute the operations corresponding to the above modules.

[0119] Those skilled in the art will understand that Figure 2 The structure shown in the figure is only a block diagram of a part of the structure related to the present application scheme, and does not constitute a limitation of the present application scheme. The specific water pump current measurement device may include more or less components than those shown in the figure, or combine certain components, or have a different component arrangement.

[0120] Embodiment 3

[0121] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the water pump current measurement method as described in Example 1 is implemented.

[0122] Embodiment 4

[0123] In one embodiment, a computer device is provided. The computer device may be a server, and its internal structure diagram may be as follows: Figure 3 As shown. The computer device includes a processor, a memory, a network interface and a database connected through a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. When the computer program is executed by the processor, a water pump current measurement method is implemented.

[0124] Those skilled in the art will understand that Figure 3 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0125] In one embodiment, a computer device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0126] Based on the actual operating frequency F of the water pump, determine the corresponding specified carrier frequency f set ;

[0127] Based on the specified carrier frequency f set Calculate the time difference ΔT, which is the first turn-on time point T of the first phase PWM signal. 1 and the second turn-on time point T of the second phase PWM signal 2 time interval;

[0128] Based on the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off;

[0129] At the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

[0130] In one embodiment, the corresponding specified carrier frequency f is determined based on the actual operating frequency F of the water pump. set , specifically including:

[0131] Get the maximum operating frequency F of the water pump max ; Divide the operating frequency of the water pump into several operating frequency intervals; determine a corresponding standard carrier frequency for each operating frequency interval;

[0132] Based on the actual operating frequency F of the water pump max The specified carrier frequency f set .

[0133] In one embodiment, the operation frequency of the water pump is divided into several operation frequency intervals, specifically including:

[0134] The operating frequency of the water pump is divided into four operating frequency intervals: 0~F 1 、F1 ~F 2 、F 2 ~F 3 and F 3 ~F max ; Among them, F 1 、F 2 、F 3 Satisfaction: F 2 >F 1 +F min ; F 3 >F 2 +F min ; F max >F 3 +F min ; F min is the minimum frequency deviation;

[0135] The standard carrier frequency specifically includes: a first standard carrier frequency f 1 , the second standard carrier frequency f 2 , the third standard carrier frequency f 3 And the fourth standard carrier frequency f 4 , and satisfy f 4 >f 3 >f 2 >f 1 ; The first standard carrier frequency f 1 And the operating frequency range 0 ~ F 1 Correspondingly, the second standard carrier frequency f 2 and operating frequency range F 1 ~F 2 Correspondingly, the third standard carrier frequency f 3 and operating frequency range F 2 ~F 3 Correspondingly, the fourth standard carrier frequency f 4 and operating frequency range F 3 ~F max corresponding;

[0136] The specified carrier frequency f is determined based on the operating frequency interval to which the actual operating frequency F of the water pump belongs and the standard carrier frequency corresponding to the interval. set , specifically including:

[0137] In F∈(0,F 1 ), f set =f 1 ;

[0138] In F∈(F 1 ,F 2 ), f set =f 2;

[0139] In F∈(F 2 ,F 3 ), f set =f 3 ;

[0140] In F∈(F 3 ,F max ), f set =f 4 .

[0141] In one embodiment, the carrier frequency f set Calculate the time difference ΔT, specifically including:

[0142] The first opening time point T is calculated by the following formula 1 And the second opening time point T 2 :

[0143]

[0144]

[0145] Among them, K g is the SVPWM modulation coefficient; θ is the SVPWM phase angle; T s =1 / f set ;

[0146] According to the first opening time point T 1 And the second opening time point T 2 Calculate the time difference ΔT, specifically including: ΔT = T 2 -T 1 .

[0147] In one embodiment, the time difference ΔT, the first opening time point T 1 , preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , specifically including:

[0148] Determine the time difference ΔT and the bus current stabilization time T st And the sampling chip current conversion time T sa Whether: ΔT>T st +T sa , if so, then T u1 =T 1 +T st .

[0149] In one embodiment, at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , specifically including:

[0150] If ΔT>T st +T sa , then at the current sampling time point T u1 Detect the current in the sampling resistor and obtain the corresponding sampling current i t ;

[0151] If ΔT≤T st +T sa , then use the sampling current i of the previous cycle t-1 As the sampling current i at the current time point t :i t =i t-1 .

[0152] In one embodiment, the sampling current i t , calculating the effective current I provided to the single-phase motor, specifically comprising:

[0153] Within a predetermined time, a plurality of the sampling currents i are obtained in sequence. t ; Calculate the effective current I of a single-phase motor using the following formula:

[0154] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0155] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0156] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A water pump current measurement method, applied to a frequency converter and a single-phase water pump; the frequency converter is used to invert the direct current on the bus to generate three-phase alternating current, the two ends of the single-phase water pump are respectively electrically connected to any two of the three output ends of the frequency converter, and at least one of the busbars is also provided with a sampling resistor for detecting current; characterized in that, The method comprises: Based on the actual operating frequency F of the water pump, determine the corresponding specified carrier frequency f set ; Based on the specified carrier frequency f set Calculating a time difference ΔT, where the time difference ΔT is a time interval between a first turn-on time point T1 of the first-phase PWM signal and a second turn-on time point T2 of the second-phase PWM signal; Based on the time difference ΔT, the first opening time point T1, and the preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off; At the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

2. A water pump current measurement method according to claim 1, characterized in that: Based on the actual operating frequency F of the water pump, the corresponding specified carrier frequency f is determined set , specifically including: Get the maximum operating frequency F of the water pump max ; Divide the operating frequency of the water pump into several operating frequency intervals; determine a corresponding standard carrier frequency for each operating frequency interval; Based on the actual operating frequency F of the pump max The specified carrier frequency f set .

3. A water pump current measurement method according to claim 2, characterized in that: The operation frequency of the water pump is divided into several operation frequency intervals, specifically including: The operating frequency of the water pump is divided into four operating frequency intervals: 0-F1, F1-F2, F2-F3 and F3-F max ; Among them, F1, F2, F3 satisfy: F2>F1+F min ; F3>F2+F min ; F max >F3+F min ; F min is the minimum frequency deviation; The standard carrier frequency specifically includes: a first standard carrier frequency f1, a second standard carrier frequency f2, a third standard carrier frequency f3 and a fourth standard carrier frequency f4, and satisfies f4>f3>f2>f1; the first standard carrier frequency f1 corresponds to the operating frequency interval 0 to F1, the second standard carrier frequency f2 corresponds to the operating frequency interval F1 to F2, the third standard carrier frequency f3 corresponds to the operating frequency interval F2 to F3, the fourth standard carrier frequency f4 corresponds to the operating frequency interval F3 to F max corresponding; The specified carrier frequency f is determined based on the operating frequency interval to which the actual operating frequency F of the water pump belongs and the standard carrier frequency corresponding to the interval. set , specifically including: In the case of F∈(0,F1), f set =f1; In the case of F∈(F1,F2), f set =f2; In the case of F∈(F2, F3), f set =f3; In F∈(F3, F max ), f set =f4.

4. A water pump current measurement method according to claim 1, characterized in that: The specified carrier frequency f set Calculate the time difference ΔT, specifically including: The first activation time point T1 and the second activation time point T2 are calculated by the following formula: Among them, K g is the SVPWM modulation coefficient; θ is the SVPWM phase angle; T s =1 / f set ; Calculating the time difference ΔT according to the first activation time point T1 and the second activation time point T2 specifically includes: ΔT=T2-T1.

5. A water pump current measurement method according to claim 4, characterized in that: The time difference ΔT, the first opening time point T1, and the preset bus current stabilization time T st And the preset sampling chip current conversion time T sa , calculate the current sampling time point T u1 , specifically including: Determine the time difference ΔT and the bus current stabilization time T st And the sampling chip current conversion time T sa Whether: ΔT>T st +T sa , if so, then T u1 =T1+T st .

6. A water pump current measurement method according to claim 5, characterized in that: At the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , specifically including: If ΔT>T st +T sa , then at the current sampling time point T u1 Detect the current in the sampling resistor and obtain the corresponding sampling current i t ; If ΔT≤T st +T sa , then use the sampling current i of the previous cycle t-1 As the sampling current i at the current time point t :i t =i t-1 .

7. A water pump current measurement method according to claim 6, characterized in that: The sampling current i t , calculating the effective current I provided to the single-phase motor, specifically comprising: Within a predetermined time, a plurality of the sampling currents i are obtained in sequence. t ; Calculate the effective current I of a single-phase motor using the following formula:

8. A water pump current measuring device, characterized in that: The device comprises: Carrier frequency determination unit: used to determine the corresponding specified carrier frequency f based on the actual operating frequency F of the water pump set ; The time difference calculation unit is used to calculate the time difference based on the specified carrier frequency f set Calculating a time difference ΔT, where the time difference ΔT is a time interval between a first turn-on time point T1 of the first-phase PWM signal and a second turn-on time point T2 of the second-phase PWM signal; A time point calculation unit is used to calculate the bus current stabilization time T based on the time difference ΔT, the first opening time point T1 and the preset bus current stabilization time T st , calculate the current sampling time point T u1 , the current sampling time point T u1 Specifically, it is a time point when only the first PWM signal is turned on and the second phase PWM signal and the third phase PWM signal are turned off; Current calculation unit: used to calculate the current at the current sampling time point T u1 Detect the sampling current i in the sampling resistor t , and based on the sampled current i t , calculate the effective current I supplied to the single-phase motor.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the water pump current measurement method according to any one of claims 1 to 7 is implemented.

10. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the water pump current measurement method as described in any one of claims 1 to 7 is implemented.

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