CN111130421A

CN111130421A - Frequency converter control method

Info

Publication number: CN111130421A
Application number: CN201811186789.9A
Authority: CN
Inventors: 黄嘉楠; 吴小萍
Original assignee: Lexing Electric Wuxi Co Ltd
Current assignee: Lexing Electric Wuxi Co Ltd
Priority date: 2018-10-12
Filing date: 2018-10-12
Publication date: 2020-05-08
Anticipated expiration: 2038-10-12
Also published as: CN111130421B

Abstract

The present disclosure provides a method for controlling a frequency converter, including: step S1, controlling the output frequency of the frequency converter to be a preset waiting frequency in a first preset time, and detecting the voltage of the direct current end; step S2, if the voltage of the direct current terminal does not reach the first preset value or exceeds the second preset value, the step S1 is returned after waiting for the second preset time; step S3, if the voltage of the direct current terminal reaches the first preset value, the output frequency is controlled to be a preset starting frequency within a third preset time; and step S4, adjusting the lifting speed of the output frequency in real time according to the voltage of the direct current end, and lifting the output frequency to a preset working frequency of the motor. The frequency converter control method can improve the solar energy utilization efficiency, and enables the load of the frequency converter to obtain the maximum output power.

Description

Frequency converter control method

Technical Field

The disclosure relates to the technical field of electronic power, in particular to a frequency converter control method.

Background

The frequency converter for the solar electric pump is supplied with direct current by obtaining direct current from the solar power module, and is inverted into alternating current in the frequency converter so as to drive the electric pump, and can generate electricity and drive loads by utilizing photovoltaic solar energy in areas without power grids in mountainous regions, hills, remote mountainous and villages and the like, or electric pump equipment of fan water pumps in remote and special areas is used for farmland irrigation or drinking water allocation and transportation, so that the full utilization of energy is realized, the application of green energy is promoted, and the frequency converter has good promotion effect on environmental protection and economic development.

In the related art, the control of the frequency converter is realized by detecting the voltage of the direct current input terminal of the frequency converter, increasing the output frequency when the voltage is smaller than a preset value, and reducing the output frequency when the voltage is smaller than the preset value. Because the output of the solar power supply is unstable, the control mode can reduce the output frequency in the stable operation process of the motor, and the use efficiency is influenced.

Therefore, a control method of a solar cell-adapted inverter that can improve the use efficiency is required.

It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.

Disclosure of Invention

An object of the present disclosure is to provide a control method of an inverter for converting a power source of a solar cell into an alternating current, which overcomes, at least to some extent, the problem of low driving efficiency due to the limitations and disadvantages of the related art.

According to a first aspect of embodiments of the present disclosure, there is provided a control method including:

step S1, controlling the output frequency of the frequency converter to be a preset waiting frequency in a first preset time, and detecting the voltage of the direct current end;

step S2, if the voltage of the direct current terminal does not reach the first preset value or exceeds the second preset value, the step S1 is returned after waiting for the second preset time;

step S3, if the voltage of the direct current terminal reaches the first preset value, the output frequency is controlled to be a preset starting frequency within a third preset time;

and step S4, adjusting the lifting speed of the output frequency in real time according to the voltage of the direct current end, and lifting the output frequency to a preset working frequency of the motor.

In an exemplary embodiment of the present disclosure, step S4 includes:

detecting the voltage of the direct current terminal in real time;

if the direct-current end voltage is in a preset undervoltage interval, controlling the lifting speed of the output frequency to be a preset minimum speed;

if the direct-current end voltage is in a preset medium-voltage interval, controlling the lifting speed of the output frequency to be a preset basic speed;

and if the direct-current end voltage is in a preset sufficient voltage interval, controlling the lifting speed of the output frequency to be twice of the preset basic speed.

In an exemplary embodiment of the present disclosure, step S4 further includes:

if the direct-current end voltage is in a preset low-voltage interval, controlling the output frequency to be a preset minimum value;

and if the direct-current end voltage is in a preset high-voltage interval, controlling the lifting speed of the output frequency to be five times of the preset basic speed.

In an exemplary embodiment of the present disclosure, further comprising:

step S5, monitoring the voltage of the direct current end in real time after the output frequency reaches the preset working frequency;

and step S6, when the voltage of the direct current terminal is smaller than the first preset value, starting retry until the voltage of the direct current terminal reaches the first preset value or the retry frequency reaches a preset value.

In an exemplary embodiment of the present disclosure, the retrying includes:

controlling the frequency converter to stand by within preset standby time corresponding to a reset sequence;

detecting the voltage of the direct current end after controlling the output power to be the preset starting frequency within the preset reset time corresponding to the reset sequence;

if the direct current terminal voltage reaches the first preset value, returning to the step S4;

if the direct-current end voltage is smaller than the first preset value, judging whether the reset times reach a preset value according to the reset sequence;

and starting the next retry when the reset sequence does not reach the preset value.

In an exemplary embodiment of the present disclosure, further comprising:

step S7, after the output frequency reaches the preset working frequency, if the output frequency is larger than or equal to a preset frequency value, monitoring the load value of the motor in real time;

step S8, determining a current standard load value corresponding to the current output frequency according to a preset frequency-load curve and the output frequency;

step S9, if the load value is less than the preset minimum load value, a fault alarm is sent out;

and step S10, if the time that the load value is less than the current standard load value reaches the preset alarm time, sending out a fault alarm.

According to a second aspect of the embodiments of the present disclosure, there is provided a frequency converter, including:

the detection part is provided with a direct current input end, is coupled to the power output end of the solar battery and is used for receiving and detecting the voltage of the direct current output by the solar battery so as to obtain the direct current end voltage;

the inverter is coupled to the motor and the detection part and used for generating alternating current according to the voltage of the direct current end and outputting the alternating current to the motor;

the control part is coupled to the frequency conversion part and the detection part, and is used for controlling the inverter to adjust the output frequency of the alternating current according to the voltage of the direct current end, and the control part is arranged to execute the following steps:

In some embodiments, the control section is configured to:

detecting the voltage of the direct current terminal in real time;

if the direct-current end voltage is in a preset adaptation interval, controlling the lifting speed of the output frequency to be a preset basic speed;

According to a third aspect of the present disclosure, there is provided a frequency converter control circuit comprising: a memory; and a processor coupled to the memory, the processor configured to perform the method of any of the above based on instructions stored in the memory.

According to a fourth aspect of the disclosure, there is provided a computer readable storage medium having a program stored thereon, which when executed by a processor, performs the method as described in any one of the above.

The frequency converter and the frequency converter control method can be better adapted to the solar battery. By using the Pre-PID mode in the starting process, the motor can be effectively protected from being influenced by unstable voltage when being started. The motor can be stably driven by controlling the lifting speed of the alternating current output frequency according to the voltage of the direct current end, and the motor is effectively protected to work at the preset working frequency. Because the change speed of the output frequency changes along with the voltage of the direct-current end, the maximum power of the load can be ensured, and the application efficiency of the solar energy is improved.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and together with the description, serve to explain the principles of the disclosure. It is to be understood that the drawings in the following description are merely exemplary of the disclosure, and that other drawings may be derived from those drawings by one of ordinary skill in the art without the exercise of inventive faculty.

Fig. 1 is an example of an application scenario and a connection mode of a frequency converter in the embodiment of the present disclosure.

Fig. 2 schematically shows a flow chart of a frequency converter control method in an exemplary embodiment of the present disclosure.

Fig. 3 is a schematic diagram of dividing the dc terminal voltage according to the embodiment of the disclosure.

Fig. 4 is a schematic diagram illustrating the control of the rising speed of the output frequency according to the dc voltage according to the embodiment of the disclosure.

Fig. 5 is another schematic diagram of controlling the rising speed of the output frequency according to the dc terminal voltage according to the embodiment of the disclosure.

Fig. 6A is a flowchart of a control method provided in an embodiment of the present disclosure.

Fig. 6B is a sub-flowchart of the retry process shown in fig. 6A.

Fig. 7 is a flowchart of a control method provided in an embodiment of the present disclosure.

Fig. 8 is a block diagram of a frequency converter in an exemplary embodiment of the present disclosure.

Fig. 9 is a block diagram of a frequency converter control circuit in an exemplary embodiment of the present disclosure.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.

Further, the drawings are merely schematic illustrations of the present disclosure, in which the same reference numerals denote the same or similar parts, and thus, a repetitive description thereof will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices.

The following detailed description of exemplary embodiments of the disclosure refers to the accompanying drawings.

Referring to fig. 1, in practical applications, a dc terminal of the inverter 1 is coupled to a power output terminal of the solar cell 2, and an ac terminal may be coupled to a power input terminal of the motor 3. In the embodiment shown in fig. 1, the motor may be, for example, a three-phase ac motor that may be used to drive a water pump or other machine.

Fig. 2 schematically shows a flow chart of a frequency converter control method in an exemplary embodiment of the present disclosure. Referring to fig. 1, the control method 100 may include:

FIG. 2 is a schematic diagram of the operation curves from step S1 to step S4.

Referring to fig. 2, the operation signal input may be given by confirming whether the solar cell voltage is sufficient or not at the time of the start of the inverter. In the embodiment shown in fig. 2, the first preset time may be 5s, for example, and the preset waiting frequency may be 5Hz, for example.

In fig. 2, the inverter is first controlled to operate at 5Hz within 5 seconds, and then the next action is determined according to the magnitude of the dc terminal voltage (i.e. the voltage of the solar cell) of the inverter.

If the voltage of the solar cell does not reach the first preset value, the method proceeds to step S2, and automatically waits for a second preset time, for example, 5 minutes. When the mobile terminal enters the standby state, a 'waiting' state can be displayed on the display screen, and the remaining standby time can be displayed in the standby process. In the standby state, if a stop instruction (fault occurs or the frequency converter is controlled to stop running manually) is received, the frequency converter can be controlled to enter a ready state, and the standby time is cleared.

If the solar cell voltage reaches the first preset value, the process proceeds to step S3, and the Pre-Pid function is performed. Pre-Pid (Pre-Proportional integral Differential coefficient control) is a control method implemented when the frequency converter is started in order to make the electric pump reach operable pressure in the early stage of operation according to the embodiment of the present disclosure.

Referring to fig. 2, in step S3, the output frequency of the frequency converter may be controlled to maintain the Pre-PID frequency for a third preset time (Pre-PID delay period).

With continued reference to fig. 2, after the Pre-PID process is completed, the output frequency of the frequency converter may be gradually controlled to be increased to the preset operating frequency of the motor, and in order to achieve high operation efficiency of the motor, in the embodiment of the present disclosure, the increasing speed of the output frequency is controlled according to the dc terminal voltage of the frequency converter.

Referring to fig. 3 in an embodiment of the present disclosure, six reference voltages may be set from low to high.

Firstly, a fault voltage V0 can be set according to the lowest extreme value of the running voltage of the frequency converter, namely, if the direct-current end voltage is lower than the fault voltage, the frequency converter enters a state that the frequency converter cannot be started; secondly, a preset first preset value V1 can be set, which indicates that the frequency converter can start to increase the lowest voltage of the output frequency; the preset under-voltage value V2, the preset medium-voltage value V3 and the preset foot-voltage value V4 represent voltage ranges in which the frequency converter can increase the output frequency, and these values can be set by those skilled in the art according to actual situations, for example, V2 can be 30% of V4, and V3 can be 50% of V4; for controlling the high voltage fault, a second preset value V5 measuring the high voltage level may also be provided.

The six reference voltages divide the dc voltage into several intervals. The voltage between the fault voltage and the first preset value can be called as a preset low-voltage interval; the interval between the first preset value and the preset undervoltage value can be called a preset undervoltage interval; the interval between the preset undervoltage value and the preset medium-voltage value can be called a preset medium-voltage interval; the interval between the preset medium pressure value and the preset foot pressure value can be called a preset foot pressure interval; the interval between the preset foot pressure value and the second preset value may be referred to as a preset high-pressure interval.

Referring to fig. 4, after detecting the dc voltage in real time, if the dc voltage is in a preset under-voltage interval, controlling the increasing speed of the output frequency to be a preset minimum speed; if the direct-current end voltage is in a preset adaptation interval, controlling the lifting speed of the output frequency to be a preset basic speed; and if the direct-current end voltage is in a preset sufficient voltage interval, controlling the lifting speed of the output frequency to be twice of the preset basic speed.

Fig. 5 is another schematic diagram of the embodiment of the present disclosure controlling the boosting speed of the output frequency according to the dc terminal voltage on the basis of fig. 4.

Referring to fig. 5, if the dc voltage is less than the first preset value, controlling the output frequency to be a preset minimum value; and if the direct-current end voltage is positioned in the preset high-voltage interval, controlling the lifting speed of the output frequency to be five times of the preset basic speed.

Referring to fig. 6A, in some embodiments, the frequency converter control method further comprises:

Fig. 6B is a sub-flowchart of the retry process shown in fig. 6A.

Referring to fig. 6B, the process of retry may be, for example:

step S61, controlling the frequency converter to stand by in a preset standby time corresponding to a reset sequence;

step S62, detecting the dc terminal voltage after controlling the output power to the preset start frequency within a preset reset time corresponding to the reset sequence;

step S63, if the voltage of the direct current terminal reaches the first preset value, returning to step S4;

step S64, if the DC end voltage is less than the first preset value, judging whether the reset times reach the preset value according to the reset sequence;

and step S64, starting the next retry when the reset sequence does not reach the first preset value.

In the normal operation process of the frequency converter, if the direct-current end voltage drops below the first preset value, the starting retry can be carried out for multiple times. The standby time and the frequency control time for each retry may be different according to the number of retries. For example, the reset time may be preset to 5 times, and the preset reset time and the standby time for the first retry may be shorter than those for the fifth retry. And if the voltage of the direct current end does not rise to the first preset value after 5 times of retry processes, determining that the retry fails, and performing fault alarm. If the dc terminal voltage is found to have risen back to or above the first preset value during the retry process, the output frequency may be raised to the preset operating frequency again according to the method of step S4.

Through setting up retry mechanism, can allow the converter to give certain buffer time when solar cell output is unstable, avoid because the voltage that solar cell appears by the influence of weather condition unstable causes frequent start and stop influence to converter and motor.

Referring to fig. 7, in some embodiments, the control method of the frequency converter may further include:

During the normal operation process of the frequency converter (after the output frequency reaches the preset working frequency, the output frequency is greater than or equal to the preset frequency value), the load can be monitored in real time, and the adverse effect of the load fault on the frequency converter is avoided.

First, the frequency-load curve can be set by the user to determine the corresponding standard load value of the frequency converter at an operating frequency. Then, the change of the load value is monitored, and when the time that the load value is below the frequency-load curve reaches the preset alarm time, a fault alarm can be triggered.

In addition, a fault alarm may be triggered when the load value does not satisfy the set load state.

It should be noted that if the current operating frequency is below the preset frequency value, the function shown in fig. 7 is not triggered, so as to avoid misjudgment of the cause of the fault due to the operating setting of the frequency converter itself.

Fig. 8 schematically illustrates a block diagram of a frequency converter in an exemplary embodiment of the disclosure.

Referring to fig. 8, the frequency converter 1 may include:

a detecting part 11 having a dc input end coupled to the power output end of the solar cell, for receiving and detecting the voltage of the dc output by the solar cell to obtain a dc end voltage;

an inverter 12, coupled to the motor and the detection unit, for generating an ac power according to the dc terminal voltage and outputting the ac power to the motor;

a control unit 13, coupled to the frequency conversion unit and the detection unit, for controlling the inverter to adjust the output frequency of the ac power according to the dc terminal voltage, and configured to perform the following steps:

In some embodiments, step S4 includes:

detecting the voltage of the direct current terminal in real time;

and if the direct-current end voltage is positioned in the preset high-voltage interval, controlling the lifting speed of the output frequency to be five times of the preset basic speed.

In some embodiments, the controller 13 is further configured to perform the steps of:

Wherein the retry procedure may include:

after the output frequency reaches the preset working frequency, if the output frequency is greater than or equal to a preset frequency value, monitoring the load value of the motor in real time;

determining a current standard load value corresponding to the current output frequency according to a preset frequency-load curve and the output frequency;

if the load value is smaller than a preset minimum load value, sending a fault alarm;

and if the time that the load value is less than the current standard load value reaches the preset alarm time, sending out a fault alarm.

In addition, the frequency converter 1 may further have a display screen for displaying information such as a standby signal, standby time, current accumulated power consumption, and the like.

Since the functions of the apparatus 800 have been described in detail in the corresponding method embodiments, the disclosure is not repeated herein.

It should be noted that although in the above detailed description several modules or units of the device for action execution are mentioned, such a division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit, according to embodiments of the present disclosure. Conversely, the features and functions of one module or unit described above may be further divided into embodiments by a plurality of modules or units.

Furthermore, the above-described figures are merely schematic illustrations of processes involved in methods according to exemplary embodiments of the invention, and are not intended to be limiting. It will be readily understood that the processes shown in the above figures are not intended to indicate or limit the chronological order of the processes. In addition, it is also readily understood that these processes may be performed synchronously or asynchronously, e.g., in multiple modules.

In an exemplary embodiment of the present disclosure, there is also provided a frequency converter control circuit capable of implementing the above method.

As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as a system, method or program product. Thus, various aspects of the invention may be embodied in the form of: an entirely hardware embodiment, an entirely software embodiment (including firmware, microcode, etc.) or an embodiment combining hardware and software aspects that may all generally be referred to herein as a "circuit," module "or" system.

The frequency converter control circuit 900 according to this embodiment of the present invention is described below with reference to fig. 9. The frequency converter control circuit 900 shown in fig. 9 is only an example and should not bring any limitation to the function and the scope of use of the embodiment of the present invention.

As shown in fig. 9, the components of the frequency converter control circuit 900 may include, but are not limited to: the at least one processing unit 910, the at least one memory unit 920, and a bus 930 that couples various system components including the memory unit 920 and the processing unit 910.

Wherein the storage unit stores program code that can be executed by the processing unit 910, such that the processing unit 910 performs the steps according to various exemplary embodiments of the present invention described in the above section "detailed description of the present specification. For example, the processing unit 910 may execute step S1 shown in fig. 1, control the output frequency of the frequency converter to be a preset waiting frequency within a first preset time, and detect the dc voltage; step S2, if the voltage of the direct current terminal does not reach the first preset value or exceeds the second preset value, the step S1 is returned after waiting for the second preset time; step S3, if the voltage of the direct current terminal reaches the first preset value, the output frequency is controlled to be a preset starting frequency within a third preset time; and step S4, adjusting the lifting speed of the output frequency in real time according to the voltage of the direct current end, and lifting the output frequency to a preset working frequency of the motor.

The storage unit 920 may include a readable medium in the form of a volatile storage unit, such as a random access memory unit (RAM)9201 and/or a cache memory unit 9202, and may further include a read only memory unit (ROM) 9203.

Storage unit 920 may also include a program/utility 9204 having a set (at least one) of program modules 9205, such program modules 9205 including but not limited to: an operating system, one or more application programs, other program modules, and program data, each of which, or some combination thereof, may comprise an implementation of a network environment.

Bus 930 can be any of several types of bus structures including a memory unit bus or memory unit controller, a peripheral bus, an accelerated graphics port, a processing unit, or a local bus using any of a variety of bus architectures.

Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which may be a personal computer, a server, a terminal device, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.

In an exemplary embodiment of the present disclosure, there is also provided a computer-readable storage medium having stored thereon a program product capable of implementing the above-described method of the present specification. In some possible embodiments, aspects of the invention may also be implemented in the form of a program product comprising program code means for causing a terminal device to carry out the steps according to various exemplary embodiments of the invention described in the above-mentioned "detailed description of the invention" section of the present description, when said program product is run on said terminal device.

In the disclosed embodiments, a readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

The program product may employ any combination of one or more readable media. The readable medium may be a readable signal medium or a readable storage medium. A readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination of the foregoing. More specific examples (a non-exhaustive list) of the readable storage medium include: an electrical connection having one or more wires, a portable disk, a hard disk, a Random Access Memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

A computer readable signal medium may include a propagated data signal with readable program code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated data signal may take many forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A readable signal medium may also be any readable medium that is not a readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

Program code embodied on a readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

Program code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object oriented programming language such as Java, C + + or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computing device, partly on the user's device, as a stand-alone software package, partly on the user's computing device and partly on a remote computing device, or entirely on the remote computing device or server. In the case of a remote computing device, the remote computing device may be connected to the user computing device through any kind of network, including a Local Area Network (LAN) or a Wide Area Network (WAN), or may be connected to an external computing device (e.g., through the internet using an internet service provider).

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A control method of a frequency converter, wherein a DC terminal of the frequency converter is coupled to a power output terminal of a solar battery, and an AC terminal of the frequency converter is coupled to a power input terminal of a motor, the method comprises the following steps:

2. The control method according to claim 1, wherein step S4 includes:

detecting the voltage of the direct current terminal in real time;

3. The control method according to claim 2, wherein step S4 further includes:

4. The control method according to claim 1, further comprising:

5. The control method of claim 4, wherein the retrying comprises:

6. The control method according to claim 1, further comprising:

step S8, if the load value is less than the preset minimum load value, a fault alarm is sent out;

step S9, determining a current standard load value corresponding to the current output frequency according to a preset frequency-load curve and the output frequency;