DC converter control method, control terminal and storage medium

Abstract

The present invention provides a DC converter control method, a control terminal, and a storage medium. The input end of the DC converter is connected to an uncontrolled rectifier, and the output end of the DC converter is used to power a load; and the DC converter adopts a voltage loop and a current loop control mode; the above-mentioned control method includes: obtaining the output current and voltage loop error of the DC converter; if the output current is less than a first preset current, and the voltage loop error is less than a preset error value, determining a target integral coefficient according to the output current and the voltage loop error; setting the integral coefficient of the current loop PI controller to the target integral coefficient; wherein the preset error value is a negative value. When the DC converter is suddenly unloaded, the present invention adjusts the integral coefficient of the current loop PI controller according to the output current and the current loop error, reduces the influence of the current error, prevents the output voltage of the DC converter from being too high due to sudden load unloading, and improves the safety of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to a direct current converter control method, a control terminal and a storage medium. Background Art

[0002] In a hybrid power supply system, photovoltaic panels, wind turbines, diesel generators or mains power input are usually rectified, and then stepped up or down by a DC converter for use by the load.

[0003] In existing technologies, because rectifiers typically use uncontrolled rectification, the power remains constant (uncontrolled). When the load suddenly drops, the DC converter's output current drops sharply, raising the DC converter's output voltage and causing overvoltage at the DC converter input, impacting system safety. Summary of the Invention

[0004] The embodiments of the present invention provide a DC converter control method, a control terminal and a storage medium to solve the problem in the prior art that a DC converter suddenly unloads its load and the DC bus voltage is too high, affecting the safe operation of the system.

[0005] In a first aspect, an embodiment of the present invention provides a method for controlling a DC converter, wherein an input end of the DC converter is connected to an uncontrolled rectifier, and an output end of the DC converter is used to power a load; and the DC converter adopts a voltage loop and a current loop control mode. The control method includes:

[0006] Obtain the output current and voltage loop error of the DC converter;

[0007] If the output current is less than the first preset current and the voltage loop error is less than the preset error value, determining a target integral coefficient according to the output current and the voltage loop error;

[0008] Set the integral coefficient of the current loop PI controller to the target integral coefficient;

[0009] The preset error value is a negative value.

[0010] In a second aspect, an embodiment of the present invention provides a control terminal comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the DC converter control method according to the first aspect or any possible implementation of the first aspect are implemented.

[0011] In a third aspect, an embodiment of the present invention provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, it implements the steps of the DC converter control method as described in the first aspect or any possible implementation of the first aspect.

[0012] The embodiment of the present invention provides a DC converter control method, a control terminal and a storage medium. The input end of the DC converter is connected to an uncontrolled rectifier, and the output end of the DC converter is used to power the load; and the DC converter adopts a voltage loop and a current loop control mode; the above-mentioned control method includes: obtaining the output current and voltage loop error of the DC converter; if the output current is less than a first preset current, and the voltage loop error is less than a preset error value, then determining a target integral coefficient according to the output current and the voltage loop error; setting the integral coefficient of the current loop PI controller to the target integral coefficient; wherein the preset error value is a negative value. When the load of the DC converter is suddenly unloaded, the output current suddenly changes. In the embodiment of the present invention, when the load of the DC converter is suddenly unloaded, the integral coefficient of the current loop PI controller is adjusted according to the output current and the current loop error, reducing the influence of the current error, preventing the output voltage of the DC converter from being too high due to the sudden unloading of the load, and improving the safety of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0014] Figure 1 is a connection topology diagram of a DC converter provided by an embodiment of the present invention;

[0015] Figure 2 This is a flow chart of an implementation method of a DC converter control method provided by an embodiment of the present invention;

[0016] Figure 3 1 is a schematic structural diagram of a DC converter control device provided by an embodiment of the present invention;

[0017] Figure 4 is a schematic diagram of a control terminal provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0018] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below with reference to the accompanying drawings.

[0020] Figure 1 The figure shows a connection topology diagram of a DC converter 11. The input of DC converter 11 is connected to an uncontrolled rectifier 12 (composed of uncontrolled rectifier diodes, whose DC voltage cannot be adjusted). The output of DC converter 11 is connected to a load 13. Because the output power of uncontrolled rectifier 12 is uncontrolled and therefore fixed, when the load suddenly drops (abruptly), the output current of DC converter 11 drops sharply. The loop circuit increases the output voltage of DC converter 11 to raise the output current. Consequently, the output voltage of DC converter 11 increases, causing equipment failure.

[0021] Based on the above, see Figure 2 , which shows a flow chart of an implementation of a DC converter control method provided by an embodiment of the present invention, and is described in detail as follows:

[0022] refer to Figure 1 The input end of the DC converter 11 is connected to the uncontrolled rectifier 12, and the output end of the DC converter 11 is used to power the load 13; and the DC converter 11 adopts the control mode of the voltage loop and the current loop; the above control method includes:

[0023] S101: Obtaining the output current and voltage loop error of the DC converter 11;

[0024] S102: If the output current is less than a first preset current and the voltage loop error is less than a preset error value, determining a target integral coefficient according to the output current and the voltage loop error;

[0025] S103: setting the integral coefficient of the current loop PI controller to a target integral coefficient;

[0026] The preset error value is a negative value.

[0027] When the output current of DC converter 11 decreases while the output voltage of DC converter 11 increases, it indicates that the load of DC converter 11 has suddenly shed. Because DC converter 11 uses voltage and current loop control modes, when the voltage loop error is less than a preset error value (the preset error value is negative), it indicates that the output voltage of DC converter 11 is too high. Therefore, combined with the output current of DC converter 11, it can be used to determine whether the load has suddenly shed.

[0028] When a sudden load unloading is detected, the integral coefficient of the current loop PI controller is dynamically adjusted according to the output current and voltage loop error to reduce the influence of the current loop error, that is, reduce the influence of the load 13, prevent the output voltage of the DC converter 11 from being too high due to the sudden load unloading, and improve the safety and stability of the system.

[0029] In a possible implementation, S102 may include:

[0030] S1021: Determine a compensation coefficient based on the output current;

[0031] S1022: Calculate a target integral coefficient based on the compensation coefficient and the voltage loop error using the first formula;

[0032] The first formula can be:

[0033] K=1+m*U_ERRO

[0034] Where K is the target integral coefficient, m is the compensation coefficient, and U_ERRO is the voltage loop error.

[0035] In the embodiment of the present invention, the DC converter 11 adopts a voltage loop and current loop control mode. When the output current of the DC converter 11 decreases, the output voltage of the DC converter 11 will be raised to increase the output current. Since the voltage loop error is negative when the load is suddenly unloaded, the smaller the output current, the greater the sudden change in the output current. The integral coefficient of the current loop should be smaller to reduce the impact of the current loop error, thereby preventing the output voltage of the DC converter 11 from being too high. At the same time, the smaller the voltage loop error, the more the output voltage of the DC converter 11 is raised, and the smaller the integral coefficient of the current loop should be.

[0036] Based on this, the embodiment of the present invention determines the compensation coefficient according to the output current, and then combines the compensation coefficient with the voltage loop error to determine the target integral coefficient according to the first formula. The integral coefficient of the current loop can be dynamically adjusted according to the actual output current and the voltage loop error, so that the output voltage of the DC converter 11 is stable, not affected by the load 13, and will not be raised due to sudden load unloading.

[0037] In a possible implementation, S1021 may include:

[0038] 1. If the output current is less than the first preset current and greater than the second preset current, the compensation coefficient is the first preset compensation coefficient;

[0039] 2. If the output current is not greater than the second preset current, the compensation coefficient is the second preset compensation coefficient;

[0040] The first preset compensation coefficient is smaller than the second preset compensation coefficient.

[0041] Based on the above analysis, the smaller the output current, the greater the output current mutation, and the smaller the integral coefficient of the current loop should be to prevent the output voltage of DC converter 11 from being too high. Therefore, in this embodiment of the present invention, if the output current is not greater than the second preset current (smaller), the compensation coefficient is the larger second preset compensation coefficient. According to the first formula above, the smaller K is. If the output current is less than the first preset current and greater than the second preset current (larger), the compensation coefficient is the smaller first preset compensation coefficient. According to the first formula above, the larger K is.

[0042] The embodiment of the present invention also adjusts the size of the compensation coefficient according to the output current, so that the output current of the DC converter 11 can be accurately controlled within the entire range, and the control effect will not be affected by changes in the output current. The control of the DC converter 11 is more precise, and the output voltage of the DC converter 11 is more stable, and overvoltage will not occur within the entire range.

[0043] In a possible implementation, the first preset compensation coefficient may be 0.001, and the second preset compensation coefficient may be 0.01.

[0044] Specifically, the first preset compensation coefficient and the second preset compensation coefficient may also be set according to actual application requirements, which is not limited here.

[0045] In a further embodiment, the first preset current may be 50A, and the second preset current may be 5A.

[0046] For example, for a DC converter 11, usually when the output current is 35A, the output voltage of the DC converter 11 will be raised, leaving a certain margin, and the first preset current is set to 50A. When the output current drops to 50A, the control is started to ensure that the output voltage of the DC converter 11 is not raised, thereby ensuring the effectiveness of the control.

[0047] Specifically, the first preset current and the second preset current may also be set according to actual application requirements, which is not limited here.

[0048] In a possible implementation, after S102, the control method may further include:

[0049] S104: Determine whether the target integral coefficient is within a preset range;

[0050] S105: If the integral coefficient is less than the lower limit of the preset range, the target integral coefficient is corrected to the lower limit;

[0051] S106: If the integral coefficient is greater than the upper limit of the preset range, the target integral coefficient is corrected to the upper limit;

[0052] S107: If the integral coefficient is within the preset range, the target integral coefficient remains unchanged;

[0053] Accordingly, S103 may specifically be: setting the integral coefficient of the current loop PI controller to the corrected target integral coefficient.

[0054] In the embodiment of the present invention, in order to ensure normal control of the current loop, the target integral coefficient may be limited to prevent over-control.

[0055] In a possible implementation, the control method may further include:

[0056] S108: If the output current is not less than the first preset current, or the voltage loop error is not less than the preset error value, then the integral coefficient of the current loop PI controller is set to 1.

[0057] If the output current is not less than the first preset current, or the voltage loop error is not less than the preset error value, it means that the load 13 is not suddenly unloaded, and there is no need to adjust the integral parameter of the current loop PI controller. Therefore, the integral parameter of the current loop PI controller is set to the parameter during normal control, that is, 1.

[0058] In a possible implementation, before S101, the control method may further include:

[0059] S109: Acquire multiple output voltages of the DC converter 11 sampled within a preset time period;

[0060] S1010: Filtering multiple output voltages to obtain a target output voltage;

[0061] S1011: Subtract the target output voltage from the reference voltage to obtain a voltage loop error.

[0062] To prevent sampling errors, the sampled voltage may be filtered in the embodiment of the present invention to prevent sampling errors from affecting the accuracy of control.

[0063] In a further embodiment, a 2 kHz low-pass filter is used.

[0064] In a possible implementation, the DC converter 11 may be a buck type, a boost type, or a four-switch buck-boost type.

[0065] The DC converter control method in the embodiment of the present invention is applicable to various types of DC converters 11 capable of dual-loop control, such as buck type, boost type, or four-switch buck-boost type, and is not limited to the above three types.

[0066] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0067] The following are device embodiments of the present invention. For details not fully described therein, reference may be made to the corresponding method embodiments described above.

[0068] Figure 3 The following is a schematic diagram of the structure of a DC converter control device provided by an embodiment of the present invention. For ease of explanation, only the parts related to the embodiment of the present invention are shown, which are described in detail as follows:

[0069] like Figure 1 As shown, the input end of the DC converter 11 is connected to the uncontrolled rectifier 12, and the output end of the DC converter 11 is used to power the load 13; and the DC converter 11 adopts the control mode of the voltage loop and the current loop; Figure 3 As shown, the above-mentioned control device includes:

[0070] The parameter acquisition module 21 is used to obtain the output current and voltage loop error of the DC converter 11;

[0071] an integral coefficient determination module 22 for determining a target integral coefficient based on the output current and the voltage loop error if the output current is less than a first preset current and the voltage loop error is less than a preset error value;

[0072] A first integral coefficient adjustment module 23 is used to set the integral coefficient of the current loop PI controller to a target integral coefficient;

[0073] The preset error value is a negative value.

[0074] In a possible implementation, the integral coefficient determination module 22 may include:

[0075] A first coefficient determining unit 221 is configured to determine a compensation coefficient according to the output current;

[0076] The second coefficient determination unit 222 is configured to calculate a target integral coefficient based on the compensation coefficient and the voltage loop error in combination with the first formula;

[0077] The first formula can be:

[0078] K=1+m*U_ERRO

[0079] Where K is the target integral coefficient, m is the compensation coefficient, and U_ERRO is the voltage loop error.

[0080] In a possible implementation, the first coefficient determination unit 221 may be specifically configured to:

[0081] 1. If the output current is less than the first preset current and greater than the second preset current, the compensation coefficient is the first preset compensation coefficient;

[0082] 2. If the output current is not greater than the second preset current, the compensation coefficient is the second preset compensation coefficient;

[0083] The first preset compensation coefficient is smaller than the second preset compensation coefficient.

[0084] In a possible implementation, the first preset compensation coefficient may be 0.001, and the second preset compensation coefficient may be 0.01.

[0085] In a possible implementation, the control device may further include:

[0086] A range determination module 24 is used to determine whether the target integral coefficient is within a preset range;

[0087] A first correction module 25 is configured to correct the target integral coefficient to the lower limit value if the integral coefficient is less than the lower limit value of the preset range;

[0088] A second correction module 26 is configured to correct the target integral coefficient to the upper limit value if the integral coefficient is greater than the upper limit value of the preset range;

[0089] A third correction module 27 is configured to keep the target integral coefficient unchanged if the integral coefficient is within a preset range;

[0090] Accordingly, the integral coefficient adjustment module 23 may be specifically configured to set the integral coefficient of the current loop PI controller to the corrected target integral coefficient.

[0091] In a possible implementation, the control device may further include:

[0092] The second integral coefficient adjustment module 28 is configured to set the integral coefficient of the current loop PI controller to 1 if the output current is not less than a first preset current or the voltage loop error is not less than a preset error value.

[0093] In a possible implementation, the control device may further include:

[0094] The voltage sampling module 29 is used to obtain multiple output voltages of the DC converter 11 sampled within a preset time period;

[0095] A filtering module 210 is configured to filter the multiple output voltages to obtain a target output voltage;

[0096] The error determination module 211 is configured to subtract the target output voltage from the reference voltage to obtain a voltage loop error.

[0097] In a possible implementation, the DC converter 11 may be a buck type, a boost type, or a four-switch buck-boost type.

[0098] Figure 4 Schematic diagram of a control terminal provided by an embodiment of the present invention. Figure 4 As shown, the control terminal 3 of this embodiment includes: a processor 30 and a memory 31. The memory 31 is used to store a computer program 32, and the processor 30 is used to call and run the computer program 32 stored in the memory 31 to perform the steps in the above-mentioned embodiments of the DC converter control method, such as Figure 2 Alternatively, the processor 30 is used to call and run the computer program 32 stored in the memory 31 to implement the functions of each module / unit in the above-mentioned device embodiments, such as Figure 3 The functions of modules 21 to 23 are shown.

[0099] For example, the computer program 32 may be divided into one or more modules / units, one or more modules / units being stored in the memory 31 and executed by the processor 30 to implement the present invention. One or more modules / units may be a series of computer program instruction segments capable of implementing specific functions, and the instruction segments are used to describe the execution process of the computer program 32 in the control terminal 3. For example, the computer program 32 may be divided into Figure 3 Modules / units 21 to 23 are shown.

[0100] The control terminal 3 can be a computing device such as a desktop computer, a notebook, a palmtop computer, or a cloud server. The control terminal 3 can include, but is not limited to, a processor 30 and a memory 31. Those skilled in the art will understand that Figure 4 It is only an example of the control terminal 3 and does not constitute a limitation on the control terminal 3. It may include more or fewer components than shown in the figure, or a combination of certain components, or different components. For example, the control terminal may also include input and output devices, network access devices, buses, etc.

[0101] The processor 30 may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or any conventional processor.

[0102] Memory 31 can be an internal storage unit of control terminal 3, such as the hard drive or memory of control terminal 3. Memory 31 can also be an external storage device of control terminal 3, such as a plug-in hard drive, a Smart Media Card (SMC), a Secure Digital (SD) card, a flash memory card, etc. Furthermore, memory 31 can include both the internal storage unit of control terminal 3 and an external storage device. Memory 31 is used to store computer programs and other programs and data required by the control terminal. Memory 31 can also be used to temporarily store data that has been output or is about to be output.

[0103] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of this application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0104] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0105] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of 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. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0106] In the embodiments provided by the present invention, it should be understood that the disclosed devices / control terminals and methods can be implemented in other ways. For example, the device / control terminal embodiments described above are merely illustrative. For example, the division of modules or units is merely a logical functional division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of devices or units, and can be electrical, mechanical or other forms.

[0107] Units described as separate components may or may not be physically separate, and components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0108] In addition, the functional units in the various embodiments of the present invention may be integrated into a single processing unit, each unit may exist physically separately, or two or more units may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0109] If the integrated module / unit is implemented as a software functional unit and sold or used as a standalone product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention can implement all or part of the process steps in the above-mentioned method embodiments by using a computer program to instruct the relevant hardware. The computer program can be stored in a computer-readable storage medium. When executed by a processor, the computer program can implement the steps of each of the above-mentioned method embodiments. The computer program includes computer program code, which can be in source code form, object code form, executable file, or some intermediate form. Computer-readable media can include: any entity or device capable of carrying computer program code, recording media, USB flash drives, mobile hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunications signals, and software distribution media.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A DC converter control method, characterized in that: The input end of the DC converter is connected to the uncontrolled rectifier, and the output end of the DC converter is used to power the load; and the DC converter adopts a voltage loop and a current loop control mode; the control method includes: Obtaining the output current and voltage loop error of the DC converter; If the output current is less than a first preset current and the voltage loop error is less than a preset error value, determining a target integral coefficient according to the output current and the voltage loop error; Setting the integral coefficient of the current loop PI controller to the target integral coefficient; Wherein, the preset error value is a negative value; The determining of a target integral coefficient according to the output current and the voltage loop error includes: determining a compensation coefficient according to the output current; The target integral coefficient is calculated based on the compensation coefficient and the voltage loop error in combination with the first formula; The first formula is: K=1+m*U_ERRO Wherein, K is the target integral coefficient, m is the compensation coefficient, and U_ERRO is the voltage loop error.

2. The DC converter control method according to claim 1, wherein: The determining of the compensation coefficient according to the output current includes: If the output current is less than the first preset current and greater than the second preset current, the compensation coefficient is the first preset compensation coefficient; If the output current is not greater than the second preset current, the compensation coefficient is the second preset compensation coefficient; The first preset compensation coefficient is smaller than the second preset compensation coefficient.

3. The DC converter control method according to claim 2, characterized in that: The first preset compensation coefficient is 0.001, and the second preset compensation coefficient is 0.

01.

4. The DC converter control method according to any one of claims 1 to 3, characterized in that: If the output current is less than a first preset current and the voltage loop error is less than a preset error value, after determining a target integral coefficient according to the output current and the voltage loop error, the control method further includes: Determining whether the target integral coefficient is within a preset range; If the integral coefficient is less than the lower limit of the preset range, the target integral coefficient is corrected to the lower limit; If the integral coefficient is greater than the upper limit of the preset range, the target integral coefficient is corrected to the upper limit; If the integral coefficient is within a preset range, the target integral coefficient remains unchanged; Accordingly, setting the integral coefficient of the current loop PI controller to the target integral coefficient includes: The integral coefficient of the current loop PI controller is set to the corrected target integral coefficient.

5. The DC converter control method according to any one of claims 1 to 3, characterized in that: The control method further includes: If the output current is not less than the first preset current, or the voltage loop error is not less than the preset error value, the integral coefficient of the current loop PI controller is set to 1.

6. The DC converter control method according to claim 1, wherein: Before obtaining the output current and voltage loop error of the DC converter, the control method further includes: Acquire multiple output voltages of the DC converter sampled within a preset time period; filtering the plurality of output voltages to obtain a target output voltage; The target output voltage is subtracted from the reference voltage to obtain the voltage loop error.

7. The DC converter control method according to claim 1, characterized in that: The DC converter is a buck type, a boost type or a four-switch buck-boost type.

8. A control terminal, characterized in that: The device comprises a processor and a memory, wherein the memory is used to store a computer program, and the processor is used to call and run the computer program stored in the memory to execute the DC converter control method according to any one of claims 1 to 7.

9. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the DC converter control method according to any one of claims 1 to 7 are implemented.

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