Multi-type converter ac coupling system

Abstract

The application discloses a multi-type converter AC coupling system. The system comprises a first DC power supply, a second DC power supply, a first converter, a second converter and a transformer. The first converter and the second converter are connected in parallel to the transformer. The second converter is different from the first converter in converter type. The first converter is used for controlling a first switching frequency of the first converter to be the same as a second switching frequency of the second converter. Based on the first switching frequency, the first converter is controlled to switch on or off a first switching device to convert first DC power into first AC power. The second converter is used for controlling a second switching device of the second converter to switch on or off based on the second switching frequency to convert second DC power into second AC power. Since the first converter and the second converter are connected in parallel to the transformer and the switching frequencies of the first converter and the second converter are the same, the system cost is reduced, the circulating current is significantly reduced, and the reliability of the system is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of converter control, in particular to a multi-type converter AC coupling system. BACKGROUND

[0002] With the development of new energy, the installed capacity of photovoltaic power is rapidly increasing. In order to balance the output curve, adding energy storage in photovoltaic power stations has become a development trend.

[0003] The coupling mode of photovoltaic and energy storage in power stations includes DC coupling and AC coupling, and the AC coupling is the main photovoltaic and energy storage coupling mode at present because it is flexible and simple to control.

[0004] In the photovoltaic and energy storage AC coupling scheme, the existing technical scheme mostly adopts a medium-voltage AC coupling scheme, that is, the energy storage converter and the photovoltaic converter are connected in parallel after a transformer. This scheme directly connects the existing photovoltaic and energy storage collection schemes in parallel, which is simple to realize, but the cost is high. SUMMARY

[0005] The present application provides a multi-type converter AC coupling system and a multi-type converter AC coupling system control method, which can reduce the system cost and improve the reliability of the system.

[0006] In a first aspect, a multi-type converter AC coupling system is provided, comprising: a first DC power supply, a second DC power supply, a first converter, a second converter, and a transformer.

[0007] The first DC power supply is connected with the first converter, the second DC power supply is connected with the second converter, the first converter and the second converter are connected in parallel to the transformer, and the types of the first converter and the second converter are different.

[0008] The first DC power supply is configured to provide first DC power to the first converter.

[0009] The second DC power supply is configured to provide second DC power to the second converter.

[0010] The first converter is configured to control the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, and based on the first switching frequency, control the conduction or disconnection of the first switching device of the first converter to convert the first DC power into first AC power.

[0011] The second converter is configured to control the conduction or disconnection of the second switching device of the second converter based on the second switching frequency to convert the second DC power into second AC power.

[0012] The transformer is configured to adjust the AC voltage corresponding to the first AC power and the AC voltage corresponding to the second AC power.

[0013] In the system, the first converter and the second converter are connected in parallel and then connected to the transformer, which reduces the system cost, and the first converter controls the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, that is, the first converter and the second converter control the on or off of the switching devices at the same switching frequency, which can significantly reduce the circulating current in the system and improve the reliability of the system.

[0014] In a possible design, the first converter determines the target switching frequency of the first converter according to the first switching frequency, where the target switching frequency is the same as the second switching frequency.

[0015] Through the design, the first converter can adjust the first switching frequency to the target switching frequency which is the same as the second switching frequency, so that the first converter and the second converter can control the on or off of the switching devices at the same switching frequency.

[0016] In a possible design, the first converter determines the target switching frequency as the first switching frequency after determining that the first switching frequency is the same as the second switching frequency according to the switching frequency setting information.

[0017] Through the design, the first converter can determine the target switching frequency based on the switching frequency setting information.

[0018] In a possible design, the first converter determines the frequency of the circulating current in the multi-type converter alternating current coupling system, and determines the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0019] Through the design, the first converter can determine the target switching frequency according to the obtained frequency of the circulating current and the first switching frequency.

[0020] In a possible design, if the frequency of the circulating current is the same as the first switching frequency, the first converter determines the target switching frequency as the first switching frequency; if the frequency of the circulating current includes a frequency different from the first switching frequency, the first converter determines the second switching frequency as the frequency, and determines the difference between the second switching frequency and the first switching frequency; then, the first converter determines the target switching frequency according to the frequency difference.

[0021] Through the design, the first converter can determine the target switching frequency according to the relationship between the frequency of the circulating current and the first switching frequency.

[0022] In a possible design, if the frequency difference is less than or equal to a set difference threshold, the first converter determines the target switching frequency as the first switching frequency; if the frequency difference is greater than the difference threshold, the first converter determines the target switching frequency as the second switching frequency.

[0023] In a possible design, after the first converter controls the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, the first converter determines, according to the port voltage corresponding to the first converter, the first switching time of the first switching device in a switching period, where the first switching time includes the turn-on time and the turn-off time of the first switching device.

[0024] By this design, the first converter can determine the turn-on time and the turn-off time of the first switching device in the switching period.

[0025] In a possible design, the first converter controls the first switching device of the first converter to turn on or turn off to convert the first direct current into the first alternating current based on the target switching frequency and the first switching time.

[0026] In a possible design, the second converter determines, according to the port voltage corresponding to the second converter, the second switching time of the second switching device in a switching period, where the second switching time includes the turn-on time and the turn-off time of the second switching device. Then, the second converter controls the second switching device of the second converter to turn on or turn off to convert the second direct current into the second alternating current based on the second switching frequency and the second switching time.

[0027] In a possible design, the first switching time is the same as the second switching time.

[0028] By this design, the first converter and the second converter can control the corresponding switching devices to turn on or turn off at the same switching frequency and switching time, thereby effectively reducing the circulating current in the system and improving the reliability of the system.

[0029] In a second aspect, a method for controlling a multi-type converter alternating current coupling system is provided, the method being applied to a first converter in the multi-type converter alternating current coupling system, where the multi-type converter alternating current coupling system further includes a first direct current power supply, a second direct current power supply, a second converter, and a transformer; the first direct current power supply is connected to the first converter; the second direct current power supply is connected to the second converter; the first converter and the second converter are connected in parallel to the transformer; the first converter and the second converter are of different types; and the method includes the following steps.

[0030] controlling the first switching frequency of the first converter to be the same as the second switching frequency of the second converter;

[0031] controlling the first switching device of the first converter to turn on or turn off to convert the first direct current into the first alternating current based on the first switching frequency, where the first direct current is provided by the first direct current power supply to the first converter.

[0032] In a possible design, the control of the first switching frequency of the first converter to be the same as the second switching frequency of the second converter comprises the following steps.

[0033] According to the first switching frequency, the target switching frequency of the first converter is determined.

[0034] In a possible design, the determination of the target switching frequency of the first converter according to the first switching frequency comprises the following steps.

[0035] According to switching frequency setting information, it is determined that the first switching frequency is the same as the second switching frequency.

[0036] The first switching frequency is taken as the target switching frequency.

[0037] In a possible design, the determination of the target switching frequency of the first converter according to the first switching frequency comprises the following steps.

[0038] The frequency of a circulating current in the multi-type converter AC coupling system is determined.

[0039] Based on the frequency of the circulating current and the first switching frequency, the target switching frequency is determined.

[0040] In a possible design, the determination of the target switching frequency based on the frequency of the circulating current and the first switching frequency comprises the following steps.

[0041] If the frequency of the circulating current is the same as the first switching frequency, the first switching frequency is taken as the target switching frequency.

[0042] If there is a frequency different from the first switching frequency in the frequency of the circulating current, the frequency is taken as the second switching frequency; a frequency difference between the second switching frequency and the first switching frequency is determined; and the target switching frequency is determined according to the frequency difference.

[0043] In a possible design, the determination of the target switching frequency according to the frequency difference comprises the following steps.

[0044] If the frequency difference is less than or equal to a set difference threshold, the first switching frequency is taken as the target switching frequency.

[0045] If the frequency difference is greater than the difference threshold, the second switching frequency is taken as the target switching frequency.

[0046] In a possible design, after the control of the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, the method further comprises the following steps.

[0047] determine a first switching time of a first switching device of the first converter in a switching period according to a port voltage corresponding to the first converter; the first switching time includes a turn-on time and a turn-off time of the first switching device; the first switching time is the same as a second switching time of the second converter.

[0048] In a possible design, the control of the turn-on or turn-off of the first switching device of the first converter based on the first switching frequency to convert the first direct current into the first alternating current includes:

[0049] the control of the turn-on or turn-off of the first switching device of the first converter based on the target switching frequency and the first switching time to convert the first direct current into the first alternating current.

[0050] In a third aspect, a first converter is provided, and is applied to a multi-type converter alternating current coupling system; the multi-type converter alternating current coupling system further includes a first direct current power supply, a second direct current power supply, a second converter, and a transformer; the first direct current power supply is connected to the first converter; the second direct current power supply is connected to the second converter; the first converter and the second converter are connected in parallel to the transformer; the first converter and the second converter are of different types.

[0051] The first converter includes a control module and a direct current alternating current power conversion circuit.

[0052] The control module is configured to control the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, and control the turn-on or turn-off of a first switching device in the direct current alternating current power conversion circuit based on the first switching frequency to convert the first direct current into a first alternating current; the first direct current is provided by the first direct current power supply to the first converter.

[0053] In a possible design, the control module is specifically configured to:

[0054] determine a target switching frequency of the first converter according to the first switching frequency; the target switching frequency is the same as the second switching frequency.

[0055] In a possible design, the control module is specifically configured to:

[0056] determine that the first switching frequency and the second switching frequency are the same according to switching frequency setting information;

[0057] set the first switching frequency as the target switching frequency.

[0058] In a possible design, the control module is specifically configured to:

[0059] determine a frequency of the circulating current in the multi-type converter AC coupling system;

[0060] determine the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0061] In a possible design, the control module is specifically configured to:

[0062] if the frequency of the circulating current is the same as the first switching frequency, the first switching frequency is taken as the target switching frequency;

[0063] if there is a frequency different from the first switching frequency in the frequency of the circulating current, the frequency is taken as the second switching frequency; a frequency difference between the second switching frequency and the first switching frequency is determined; and the target switching frequency is determined according to the frequency difference.

[0064] In a possible design, the control module is specifically configured to:

[0065] if the frequency difference is less than or equal to a set difference threshold, the first switching frequency is taken as the target switching frequency;

[0066] if the frequency difference is greater than the difference threshold, the second switching frequency is taken as the target switching frequency.

[0067] In a possible design, after the first switching frequency of the first converter and the second switching frequency of the second converter are controlled to be the same, the control module is specifically configured to:

[0068] determine a first switching time of a first switching device of the first converter in a switching period according to a port voltage corresponding to the first converter; the first switching time includes a turn-on time and a turn-off time of the first switching device; and the first switching time is the same as a second switching time of the second converter.

[0069] In a possible design, the control module is specifically configured to:

[0070] control turn-on or turn-off of the first switching device in the DC-AC power conversion circuit based on the target switching frequency and the first switching time, so as to convert the first DC power into the first AC power.

[0071] In a fourth aspect, the present application provides a multi-type converter AC coupling system control device, which is applied to a first converter in a multi-type converter AC coupling system; the multi-type converter AC coupling system further comprises a first DC power supply, a second DC power supply, a second converter and a transformer; the first DC power supply is connected with the first converter; the second DC power supply is connected with the second converter; the first converter and the second converter are connected in parallel to the transformer; the first converter and the second converter are of different types; and the device comprises:

[0072] a control unit configured to control a first switching frequency of the first converter to be the same as a second switching frequency of the second converter;

[0073] a conversion unit configured to control a first switching device of the first converter to be turned on or turned off to convert the first DC power into first AC power based on the first switching frequency; the first DC power is provided by the first DC power supply to the first converter.

[0074] In an optional design, the control unit is specifically configured to:

[0075] determine a target switching frequency of the first converter according to the first switching frequency; the target switching frequency is the same as the second switching frequency.

[0076] In an optional design, the control unit is specifically configured to:

[0077] determine the first switching frequency and the second switching frequency to be the same according to switching frequency setting information;

[0078] determine the first switching frequency as the target switching frequency.

[0079] In an optional design, the control unit is specifically configured to:

[0080] determine a frequency of a circulating current in the multi-type converter AC coupling system;

[0081] determine the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0082] In an optional design, the control unit is specifically configured to:

[0083] if the frequency of the circulating current is the same as the first switching frequency, determine the first switching frequency as the target switching frequency;

[0084] If there is a frequency different from the first switching frequency in the frequency of the circulating current, the frequency is taken as the second switching frequency; a frequency difference between the second switching frequency and the first switching frequency is determined; and the target switching frequency is determined according to the frequency difference.

[0085] In an alternative design, the control unit is specifically configured to:

[0086] If the frequency difference is less than or equal to a set difference threshold, the first switching frequency is taken as the target switching frequency.

[0087] If the frequency difference is greater than the difference threshold, the second switching frequency is taken as the target switching frequency.

[0088] In an alternative design, after the first switching frequency of the first converter and the second switching frequency of the second converter are controlled to be the same, the control unit is further configured to:

[0089] determine a first switching time of a first switching device of the first converter in a switching period according to a port voltage corresponding to the first converter; the first switching time includes a turn-on time and a turn-off time of the first switching device; and the first switching time is the same as a second switching time of the second converter.

[0090] In an alternative design, the conversion unit is specifically configured to:

[0091] control the first switching device of the first converter to turn on or turn off to convert the first direct current into the first alternating current based on the target switching frequency and the first switching time.

[0092] In a fifth aspect, the present application provides a computer readable storage medium having a computer program or instructions stored thereon, which, when executed, cause a computer to perform the method in the second aspect or any possible implementation manner of the second aspect.

[0093] In a sixth aspect, the present application provides a computer program product, which, when executed by a computer, causes the computer to perform the method in the second aspect or any possible implementation manner of the second aspect.

[0094] The advantages of the second aspect and the fourth aspect are described above in the description of the advantages of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0095] Figure 1 An architecture schematic diagram of a possible multi-type converter AC coupling system provided by the embodiments of the present application;

[0096] Figure 2 Another possible multi-type converter AC coupling system architecture diagram of the scheme provided by the embodiments of the present application;

[0097] Figure 3 A possible AC current diagram of the scheme provided by the embodiments of the present application;

[0098] Figure 4 A possible multi-type converter AC coupling system control method complete flow diagram of the scheme provided by the embodiments of the present application;

[0099] Figure 5 A possible multi-type converter AC coupling system control method diagram of the scheme provided by the embodiments of the present application;

[0100] Figure 6 A possible first converter structure diagram of the scheme provided by the embodiments of the present application;

[0101] Figure 7 Another possible first converter structure diagram of the scheme provided by the embodiments of the present application;

[0102] Figure 8 A possible multi-type converter AC coupling system control device structure diagram of the scheme provided by the embodiments of the present application. DETAILED DESCRIPTION

[0103] The embodiments of the present application provide a multi-type converter AC coupling system and a control method thereof. The method and the storage system are based on the same concept. Since the principles of the method and the multi-type converter AC coupling system for solving problems are similar, the implementation of the multi-type converter AC coupling system and the method can be mutually referred to, and the repeated parts will not be described again.

[0104] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings. In the description of the embodiments of the present application, the terms "first" and "second" are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features with "first" and "second" can explicitly or implicitly include one or more of the features.

[0105] In order to facilitate understanding, an exemplary description of the related concepts of the present application is given for reference.

[0106] 1) Converter, a kind of power electronic power conversion device, for converting DC into AC.

[0107] 2) circulating current, current flowing between multiple converters. Since the current does not flow to the load / grid, it becomes a circulating current.

[0108] In the description of the embodiments of the present application, the association relationship of the associated objects is described by "and / or", which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The character " / " generally represents that the associated objects before and after it are in an "or" relationship. At least one involved in the present application means one or more; multiple means two or more. In addition, it should be understood that in the description of the present application, "first", "second", etc. are used only for the purpose of distinguishing the description, and cannot be understood as indicating or implying relative importance. The embodiments of the present application will be described in detail below with reference to the drawings.

[0109] Generally, in the light storage alternating current coupling scheme, the prior art mostly adopts a medium voltage alternating current coupling scheme, that is, the energy storage converter and the photovoltaic converter are connected in parallel after a transformer. This scheme directly connects the existing photovoltaic and energy storage collection schemes in parallel, which is simple to implement, but has a high cost.

[0110] In order to solve the problem of high cost of the multi-type converter alternating current coupling system and ensure the reliability of the system, the embodiments of the present application provide a multi-type converter alternating current coupling system. The system includes a first direct current power supply, a second direct current power supply, a first converter, a second converter, and a transformer. The converter types of the first converter and the second converter are different. In the system, the first direct current power supply is connected to the first converter, the second direct current power supply is connected to the second converter, and the first converter and the second converter are connected in parallel to the transformer, thereby reducing the system cost. In addition, after the first converter controls the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, the first converter controls the conduction or disconnection of the first switching device of the first converter based on the first switching frequency to convert direct current into alternating current. The second converter controls the conduction or disconnection of the second switching device of the second converter based on the second switching frequency to convert direct current into alternating current. The first converter and the second converter in the system can control the conduction or disconnection of the corresponding switching devices based on the same switching frequency to convert direct current into alternating current, which can significantly reduce the circulating current in the system, thereby improving the reliability of the system.

[0111] The embodiments of the present application will be described in detail below with reference to the drawings.

[0112] Figure 1 A possible multi-type converter alternating current coupling system architecture to which the scheme provided by the embodiments of the present application is applicable is shown in FIG. 1. As shown in FIG. 1, the system includes at least a first direct current power supply, a second direct current power supply, a first converter, a second converter, and a transformer. Figure 1 As shown in FIG. 1, the system includes at least a first direct current power supply, a second direct current power supply, a first converter, a second converter, and a transformer.

[0113] The first DC power supply is connected with the first converter; the second DC power supply is connected with the second converter; the first converter and the second converter are connected in parallel to the transformer. The second converter is different from the first converter in converter type.

[0114] The first DC power supply is configured to provide the first DC to the first converter.

[0115] The second DC power supply is configured to provide the second DC to the second converter.

[0116] The first converter is configured to control the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, and control the turn-on or turn-off of the first switching device of the first converter based on the first switching frequency to convert the first DC into the first AC.

[0117] The second converter is configured to control the turn-on or turn-off of the second switching device of the second converter based on the second switching frequency to convert the second DC into the second AC.

[0118] The transformer is configured to adjust the AC voltage corresponding to the first AC and the AC voltage corresponding to the second AC.

[0119] The converter types in the embodiments of the present application can be classified according to the use. For example, the converter used to convert AC into DC is called a rectifier; the converter used to convert DC into AC is called an inverter; the converter used to convert AC with a given voltage, frequency and phase number into AC with different voltage, frequency and / or phase number is called an AC converter; the energy storage converter capable of realizing bidirectional conversion between an energy storage battery and AC.

[0120] The first converter and the second converter in the embodiments of the present application are connected in parallel to the low-voltage side of the transformer, and the high-voltage side of the transformer can be connected to the power grid or the load, which is not limited in the present application. The multi-type converter AC coupling system formed by directly connecting the first converter and the second converter in parallel to the transformer has lower system cost compared with connecting the first converter and the second converter in parallel through the transformer. In addition, the first converter controls the first switching frequency to be the same as the second switching frequency, so that the first converter and the second converter can control the turn-on or turn-off of the corresponding switching devices to convert DC into AC at the same switching frequency, thereby effectively reducing the circulating current between the first converter and the second converter, and further improving the reliability of the system.

[0121] The direct current power supply includes various types, including but not limited to: direct current battery, photovoltaic cell, energy storage battery, power supply formed by series connection of direct current batteries, battery or battery + direct current output generated by power electronic device. The first direct current power supply and the second direct current power supply in the application can be any of the above. Moreover, the first direct current voltage and the second direct current voltage can be the same type of direct current power supply or different direct current power supplies, which are not limited in the application.

[0122] In some optional embodiments, as shown in Figure 2 The multi-type converter AC coupling system can be a low-voltage AC coupling system. Figure 1 The system further includes a first AC cable, a second AC cable and a power grid based on the system shown in The first converter is connected to the first AC cable, the second converter is connected to the second AC cable, the first AC cable and the second AC cable are connected in parallel to the low-voltage side of the transformer, and the high-voltage side of the transformer is connected to the power grid. Optionally, the first converter can be a photovoltaic inverter, and the second converter can be an energy storage converter; or the first converter can be an energy storage converter, and the second converter can be a photovoltaic inverter. The photovoltaic inverter and the energy storage converter are connected in parallel at a ratio of 5:1 to the low-voltage side of the transformer, and the high-voltage side of the transformer can be connected to the power grid to form a low-voltage AC coupling system.

[0123] It should be noted that the multi-type converter AC coupling system shown in Figures 1-2 The above-mentioned multi-type converter AC coupling system is only an exemplary description of the multi-type converter AC coupling system applicable to the scheme of the application, and does not limit the system architecture applicable to the scheme of the application. Other devices or modules can be added to the above-mentioned system architecture, or some devices or modules can be reduced or modified.

[0124] After the first converter operates at the first switching frequency, the first switching frequency is controlled to be the same as the second switching frequency.

[0125] Optionally, after the first converter converts the first direct current into the first alternating current by controlling the conduction or disconnection of the first switching device of the first converter according to the first switching frequency, the first switching frequency is controlled to be the same as the second switching frequency.

[0126] It should be noted that the first converter includes a plurality of first switching devices.

[0127] In some optional embodiments, the way in which the first converter controls the first switching frequency to be the same as the second switching frequency includes but is not limited to: the first converter determines the target switching frequency of the first converter according to the first switching frequency.

[0128] It should be noted that the target switching frequency is the same as the second switching frequency.

[0129] Optionally, the first converter can determine the target switching frequency according to the first switching frequency in the following ways, but is not limited thereto.

[0130] Method 1: The first converter determines that the first switching frequency is the same as the second switching frequency according to the switching frequency setting information, and takes the first switching frequency as the target switching frequency.

[0131] The switching frequency setting information is set by the user in advance.

[0132] In some optional embodiments, the user sets the first switching frequency of the first converter to be the same as the second switching frequency of the second converter in advance.

[0133] The first converter obtains the switching frequency setting information, and determines that the first switching frequency set by the user is the same as the second switching frequency, and then takes the first switching frequency as the target switching frequency.

[0134] It should be noted that the switching frequency setting information is the switching frequency corresponding to the switching device in the converter set by the user in advance. The switching frequency setting information can include the first switching frequency set by the user for the first converter, and the switching frequency set by the user for the second converter. The switching frequency setting information can be stored in the first converter, or in other devices in communication connection with the first converter.

[0135] Optionally, the first converter obtains the switching frequency information after starting, and obtains the first switching frequency and the second switching frequency.

[0136] In some optional embodiments, if the first converter determines that the first switching frequency is the same as the second switching frequency, the first switching frequency is taken as the target switching frequency.

[0137] In some other optional embodiments, the first converter determines that the first switching frequency is different from the second switching frequency, and after the first direct current is converted into the first alternating current by controlling the conduction or disconnection of the first switching device according to the first switching frequency, the circulating current in the multi-type converter alternating current coupling system can be obtained, and the target switching frequency is determined according to the circulating current.

[0138] Method 2: The first converter determines the frequency of the circulating current in the multi-type converter alternating current coupling system, and determines the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0139] In some optional embodiments, the first converter can determine the target switching frequency in the following steps, but is not limited thereto.

[0140] A1: The first converter determines the frequency of the circulating current in the multi-type converter alternating current coupling system.

[0141] Optionally, the first converter obtains a circulating current between the first converter and the second converter, and detects the circulating current to determine a frequency of the circulating current.

[0142] A2: The first converter determines a target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0143] Optionally, the first converter can, but is not limited to, perform A2 by the following steps:

[0144] In some optional embodiments, if the first converter determines that the frequency of the circulating current is the same as the first switching frequency, the first switching frequency is taken as the target switching frequency.

[0145] The first converter determines that the frequency of the circulating current is the same as the first switching frequency, determines that the second switching frequency is the same as the first switching frequency, and takes the first switching frequency as the target switching frequency.

[0146] In other optional embodiments, if the first converter determines that there is a frequency different from the first switching frequency in the frequency of the circulating current, the frequency is taken as the second switching frequency. The first converter determines a frequency difference between the second switching frequency and the first switching frequency, and determines the target switching frequency according to the frequency difference.

[0147] In some optional embodiments, if the frequency difference is less than or equal to a set difference threshold, the first converter takes the first switching frequency as the target switching frequency.

[0148] When the frequency difference is less than or equal to the difference threshold, the first converter determines that the first switching frequency is the same as the second switching frequency, and takes the first switching frequency as the target switching frequency.

[0149] In other optional embodiments, if the frequency difference is greater than the difference threshold, the first converter takes the second switching frequency as the target switching frequency.

[0150] The first converter determines that the frequency difference is greater than the difference threshold, determines that the first switching frequency is different from the second switching frequency, and takes the second switching frequency as the target switching frequency.

[0151] After the first converter determines the target switching frequency according to the first switching frequency, and controls the first switching frequency to be the same as the second switching frequency, the first switching frequency determines a first switching time of a first switching device of the first converter in a switching period according to a port voltage corresponding to the first converter.

[0152] It should be noted that the first switching time includes a conduction time and a disconnection time of the first switching device. The first converter includes a plurality of first switching devices, and each first switching device corresponds to a first switching time. Each first switching device can have the same first switching time or different first switching times.

[0153] In some optional embodiments, after determining the first switching time, the first converter controls the turn-on or turn-off of the first switching device of the first converter to convert the first direct current into the first alternating current based on the target switching frequency and the first switching time.

[0154] When the first converter operates based on the first switching frequency, the second converter controls the turn-on or turn-off of the second switching device of the second converter to convert the second direct current into the second alternating current based on the second switching frequency.

[0155] It should be noted that the second converter includes a plurality of second switching devices; each second switching device corresponds to a second switching time; and the second switching time includes a turn-on time and a turn-off time of the second switching device.

[0156] The second switching device is a power electronic device in a direct-current alternating-current power conversion circuit in the second converter.

[0157] In some optional embodiments, the second converter determines the second switching time of the second switching device of the second converter in a switching period according to the port voltage corresponding to the second converter.

[0158] After determining the second switching time, the second converter controls the turn-on or turn-off of the second switching device of the second converter to convert the second direct current into the second alternating current based on the second switching frequency and the second switching time.

[0159] The first switching time is the same as the second switching time.

[0160] Since the first switching time and the second switching time are determined according to the corresponding port voltage, the first switching time is the same as the second switching time.

[0161] Optionally, in each switching period, the turn-on time and the turn-off time of the switching device corresponding to the first converter and the switching device corresponding to the second converter are the same.

[0162] In some other optional embodiments, the first switching time is determined to be the same as the second switching time when the deviation between the first switching time and the second switching time is less than a set proportion of the switching period.

[0163] For example, the set proportion is 5%; the first switching time is determined to be the same as the second switching time when the difference between the turn-on time of the first switching time and the turn-on time of the second switching time, and the difference between the turn-off time of the first switching time and the turn-off time of the second switching time are both less than 5% of the switching period.

[0164] The first converter converts the first direct current into the first alternating current according to the target switching frequency and the first switching time by controlling the first switching device to be turned on or turned off.

[0165] Figure 3 An alternating current schematic diagram is provided for the embodiment of the present application. Wherein, Figure 3 3a in FIG. 3 is a schematic diagram of the first alternating current and the second alternating current output by the first converter and the second converter when the first converter does not control the first switching frequency to be the same as the second switching frequency. Figure 3 3b in FIG. 3 is a schematic diagram of the first alternating current and the second alternating current output by the first converter and the second converter after the first converter controls the first switching frequency to be the same as the second switching frequency. Wherein, from Figure 3 As can be seen from the comparison of the current waveforms of 3a and 3b, the fluctuation degree of the current in the peak region and the trough region of 3b is obviously smaller than that of 3a. Therefore, after the first converter controls the first switching frequency to be the same as the second switching frequency, the circulating current between the converters can be effectively suppressed.

[0166] After the first converter and the second converter output the alternating current to the transformer, the transformer adjusts the alternating voltage corresponding to the first alternating current and the alternating voltage corresponding to the second alternating current.

[0167] Optionally, the transformer can output the adjusted alternating voltage to the power grid or the load.

[0168] In the above embodiment, after the first converter controls the first switching frequency to be the same as the second switching frequency, the first switching time determined by the first converter is the same as the second switching time determined by the second converter, so that the frequency of the alternating current generated by the first converter and the second converter in the subsequent process can remain consistent, thereby effectively suppressing the circulating current.

[0169] Based on the multi-type converter alternating coupling system provided in the above embodiment, the present application further provides a multi-type converter alternating coupling system control method. Figure 4 A complete flowchart of a multi-type converter alternating coupling system control method is provided for the present application. Wherein, the multi-type converter alternating coupling system control method can be applied to Figure 1 the first converter in the multi-type converter alternating coupling system shown in FIG. 1, or can be applied to the first converter in the multi-type converter alternating coupling system shown in FIG. 2. The multi-type converter alternating coupling system further comprises a first direct current power supply, a second direct current power supply, a second converter and a transformer. Figure 2

[0170] ​The flow of the method is described below taking the first converter as an example. As shown in Figure 4 The method includes the following steps.

[0171] S401. The first converter converts the first direct current into the first alternating current based on the first switching frequency controlling the turn-on or turn-off of the first switching device of the first converter.

[0172] It should be noted that the first direct current is provided by the first direct current source to the first converter.

[0173] S402. The first converter determines whether the first switching frequency is the same as the second switching frequency of the second converter according to the switching frequency setting information. If yes, step S403 is performed. If no, step S404 is performed.

[0174] S403. The first converter takes the first switching frequency as the target switching frequency.

[0175] It should be noted that the target switching frequency is the same as the second switching frequency.

[0176] S404. The first converter determines the frequency of the circulating current in the multi-type converter alternating current coupling system.

[0177] S405. The first converter determines whether there is a frequency different from the first switching frequency in the frequency of the circulating current. If no, step S403 is performed. If yes, step S406 is performed.

[0178] S406. The first converter takes the frequency different from the first switching frequency in the frequency of the circulating current as the second switching frequency.

[0179] S407. The first converter determines the frequency difference between the second switching frequency and the first switching frequency.

[0180] S408. The first converter determines whether the frequency difference is greater than the difference threshold. If yes, step S409 is performed. If no, step S403 is performed.

[0181] S409. The first converter takes the second switching frequency as the target switching frequency.

[0182] S410. The first converter determines the first switching time of the first switching device of the first converter in a switching period according to the port voltage corresponding to the first converter.

[0183] It should be noted that the first switching time includes the turn-on time and the turn-off time of the first switching device.

[0184] S411. The first converter converts the first direct current into the first alternating current based on the target switching frequency and the first switching time controlling the turn-on or turn-off of the first switching device of the first converter.

[0185] Based on the above embodiments and the same concept, as shown in Figure 5 the application also provides a multi-type converter AC coupling system control method, which can be applied to Figure 1 the first converter in the multi-type converter AC coupling system as shown, and can also be applied to Figure 2 the first converter in the multi-type converter AC coupling system as shown; the multi-type converter AC coupling system includes a first DC power supply, a second DC power supply, the first converter, a second converter, and a transformer; the first DC power supply is connected with the first converter; the second DC power supply is connected with the second converter; the first converter and the second converter are connected in parallel to the transformer; the first converter and the second converter are different in type; the method comprises:

[0186] S501, the first converter controls the first switching frequency of the first converter to be the same as the second switching frequency of the second converter.

[0187] S502, the first converter controls the conduction or disconnection of the first switching device of the first converter based on the first switching frequency to convert the first DC power into the first AC power.

[0188] It should be noted that the first DC power is provided by the first DC power supply to the first converter.

[0189] An optional implementation is to control the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, comprising:

[0190] determining the target switching frequency of the first converter according to the first switching frequency; the target switching frequency is the same as the second switching frequency.

[0191] An optional implementation is to determine the target switching frequency of the first converter according to the first switching frequency, comprising:

[0192] determining that the first switching frequency and the second switching frequency are the same according to the switching frequency setting information;

[0193] taking the first switching frequency as the target switching frequency.

[0194] An optional implementation is to determine the target switching frequency of the first converter according to the first switching frequency, comprising:

[0195] determining the frequency of the circulating current in the multi-type converter AC coupling system;

[0196] determining the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0197] An optional implementation involves determining a target switching frequency based on the frequency of the circulating current and a first switching frequency, including:

[0198] If the frequency of the circulating current is the same as the first switching frequency, then the first switching frequency is taken as the target switching frequency.

[0199] If there is a frequency in the circulating current that is different from the first switching frequency, then that frequency is taken as the second switching frequency; determine the frequency difference between the second switching frequency and the first switching frequency; and determine the target switching frequency based on the frequency difference.

[0200] One optional implementation involves determining the target switching frequency based on the frequency difference, including:

[0201] If the frequency difference is less than or equal to the set difference threshold, the first switching frequency will be used as the target switching frequency.

[0202] If the frequency difference is greater than the difference threshold, the second switching frequency will be used as the target switching frequency.

[0203] An optional implementation further includes, after controlling the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, the method further includes:

[0204] Based on the port voltage corresponding to the first converter, the first switching time of the first switching device in the switching cycle of the first converter is determined; the first switching time includes the turn-on time and the turn-off time of the first switching device; the first switching time is the same as the second switching time of the second converter.

[0205] An optional implementation involves controlling the switching of a first switching device in a first converter to convert a first direct current into a first alternating current based on a first switching frequency, including:

[0206] Based on the target switching frequency and the first switching moment, the first switching device of the first converter is controlled to turn on or off to convert the first DC power into the first AC power.

[0207] This application also provides a first converter applied to a multi-type converter AC coupling system; the multi-type converter AC coupling system further includes a first DC power supply, a second DC power supply, a second converter, and a transformer; the first DC power supply is connected to the first converter; the second DC power supply is connected to the second converter; the first converter and the second converter are connected in parallel to the transformer; the first converter and the second converter are of different types;

[0208] Among them, such as Figure 6 As shown, the first converter 600 includes: a control module 601 and a DC-AC power conversion circuit 602;

[0209] The control module 601 is configured to control the first switching frequency of the first converter to be the same as the second switching frequency of the second converter, and control the first switching device in the direct-current alternating-current power conversion circuit 602 to be turned on or turned off based on the first switching frequency to convert the first direct current into the first alternating current. The first direct current is provided by the first direct-current power supply to the first converter.

[0210] In some optional embodiments, the control module 601 is specifically configured to:

[0211] determine a target switching frequency of the first converter according to the first switching frequency; and the target switching frequency is the same as the second switching frequency.

[0212] In some optional embodiments, the control module 601 is specifically configured to:

[0213] determine that the first switching frequency is the same as the second switching frequency according to the switching frequency setting information; and

[0214] determine the first switching frequency as the target switching frequency.

[0215] In some optional embodiments, the control module 601 is specifically configured to:

[0216] determine a frequency of a circulating current in the multi-type converter alternating-current coupling system;

[0217] determine the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0218] In some optional embodiments, the control module 601 is specifically configured to:

[0219] if the frequency of the circulating current is the same as the first switching frequency, determine the first switching frequency as the target switching frequency;

[0220] if there is a frequency different from the first switching frequency in the frequency of the circulating current, determine the frequency as the second switching frequency, determine a frequency difference between the second switching frequency and the first switching frequency, and determine the target switching frequency according to the frequency difference.

[0221] In some optional embodiments, the control module 601 is specifically configured to:

[0222] if the frequency difference is less than or equal to a set difference threshold value, determine the first switching frequency as the target switching frequency;

[0223] if the frequency difference is greater than the difference threshold value, determine the second switching frequency as the target switching frequency.

[0224] In some optional embodiments, after the first switch frequency of the first converter is controlled to be the same as the second switch frequency of the second converter, the control module 601 is specifically configured to:

[0225] determine, according to the port voltage corresponding to the first converter, a first switch time of a first switch device of the first converter in a switch period; the first switch time includes a turn-on time and a turn-off time of the first switch device; and the first switch time is the same as a second switch time of the second converter.

[0226] In some optional embodiments, the control module 601 is specifically configured to:

[0227] control the turn-on or turn-off of the first switch device in the direct-current alternating-current power conversion circuit 602 based on the target switch frequency and the first switch time, so as to convert the first direct current into the first alternating current.

[0228] In another optional embodiment, as shown in Figure 7 the first converter 600 further includes a sampling module 603 and a calculation module 604.

[0229] The sampling module 603 can obtain the port voltage corresponding to the first converter and the circulating current.

[0230] The calculation module 604 can analyze the circulating current obtained by the sampling module 603, determine the frequency of the circulating current, and send the obtained frequency of the circulating current to the control module 601.

[0231] Optionally, the control module 601 can determine, by the calculation module 604, the first switch time of the first switch device of the first converter in the switch period according to the port voltage corresponding to the first converter.

[0232] It should be noted that the first converter shown in the above Figures 6-7 is only an exemplary description of the converter applicable to the scheme of the present application, and does not limit the structure of the converter applicable to the scheme of the present application. Other devices or modules can be added to the above converter structure, or some devices or modules can be reduced or modified.

[0233] The present application also provides a multi-type converter alternating-current coupling system control device, as shown in Figure 8As shown, the device 800 is applied to a first converter in a multi-type converter AC coupling system; the multi-type converter AC coupling system further includes a first DC power supply, a second DC power supply, a second converter, and a transformer; the first DC power supply is connected with the first converter; the second DC power supply is connected with the second converter; the first converter and the second converter are connected in parallel to the transformer; the first converter and the second converter are of different types; and the device 800 includes:

[0234] a control unit 801 configured to control a first switching frequency of the first converter to be the same as a second switching frequency of the second converter.

[0235] a conversion unit 802 configured to control a first switching device of the first converter to turn on or off to convert the first DC power into first AC power based on the first switching frequency; the first DC power is provided by the first DC power supply to the first converter.

[0236] In some optional embodiments, the control unit 801 is specifically configured to:

[0237] determine a target switching frequency of the first converter according to the first switching frequency; the target switching frequency is the same as the second switching frequency.

[0238] In some optional embodiments, the control unit 801 is specifically configured to:

[0239] determine the first switching frequency and the second switching frequency to be the same according to switching frequency setting information;

[0240] determine the first switching frequency as the target switching frequency.

[0241] In some optional embodiments, the control unit 801 is specifically configured to:

[0242] determine a frequency of a circulating current in the multi-type converter AC coupling system;

[0243] determine the target switching frequency based on the frequency of the circulating current and the first switching frequency.

[0244] In some optional embodiments, the control unit 801 is specifically configured to:

[0245] if the frequency of the circulating current is the same as the first switching frequency, determine the first switching frequency as the target switching frequency.

[0246] If there is a frequency different from the first switching frequency in the frequency of the circulating current, the frequency is taken as the second switching frequency; a frequency difference between the second switching frequency and the first switching frequency is determined; and the target switching frequency is determined according to the frequency difference.

[0247] In some optional embodiments, the control unit 801 is specifically configured to:

[0248] If the frequency difference is less than or equal to a set difference threshold, the first switching frequency is taken as the target switching frequency.

[0249] If the frequency difference is greater than the difference threshold, the second switching frequency is taken as the target switching frequency.

[0250] In some optional embodiments, after the first switching frequency of the first converter is controlled to be the same as the second switching frequency of the second converter, the control unit 801 is further configured to:

[0251] According to the port voltage corresponding to the first converter, a first switching time of a first switching device of the first converter in a switching period is determined; the first switching time includes a turn-on time and a turn-off time of the first switching device; and the first switching time is the same as a second switching time of the second converter.

[0252] In some optional embodiments, the conversion unit 802 is specifically configured to:

[0253] Based on the target switching frequency and the first switching time, the turn-on or turn-off of the first switching device of the first converter is controlled to convert the first direct current into the first alternating current.

[0254] Based on the above and the same idea, the present application provides a computer readable storage medium having a computer program or instructions stored thereon, which, when executed, causes a computing device to perform the method in the multi-type converter alternating coupling system control method.

[0255] Based on the above and the same idea, the present application provides a computer program product, which, when executed by a computer, causes a computing device to perform the method in the multi-type converter alternating coupling system control method.

[0256] Those skilled in the art will appreciate that embodiments of the present application can be devised for a method, a system, or a computer program product. Accordingly, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application can take the form of a computer program product on one or more computer readable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage devices, etc.) embodying computer readable program code.

[0257] The present application is described in reference to the flow diagrams and / or block diagrams of the methods, apparatus (systems) and computer program products according to this application. It will be understood that each block of the flow diagrams and / or block diagrams, and combinations of blocks in the flow diagrams and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processing device or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flow diagrams and / or block diagrams block or blocks. Figure One one or more functions specified in the flow diagram and / or block diagram block or blocks. Figure One one or more functions specified in the flow diagram and / or block diagram block or blocks.

[0258] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flow diagram and / or block diagram block or blocks. Figure One one or more functions specified in the flow diagram and / or block diagram block or blocks. Figure One one or more functions specified in the flow diagram and / or block diagram block or blocks.

[0259] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flow diagram and / or block diagram block or blocks. Figure One one or more functions specified in the flow diagram and / or block diagram block or blocks. Figure One Figure One one or more functions specified in the flow diagram and / or block diagram block or blocks.

[0260] Obviously, numerous modifications and variations of the present application are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims and their legal equivalents, the application can be practiced otherwise than as specifically described.

Claims

1. A multi-type converter AC coupling system, characterized by, include: First DC power supply, second DC power supply, first converter, second converter, transformer; Wherein, the first DC power supply is connected to the first converter; the second DC power supply is connected to the second converter; the first converter and the second converter are connected in parallel to the transformer; the second converter and the first converter are of different converter types; The first DC power supply is used to provide first DC power to the first converter; The second DC power supply is used to provide a second DC power to the second converter; The first converter is used to control the frequency of the circulating current in the AC coupling system of the multi-type converter; if there is a frequency in the circulating current that is different from the first switching frequency of the first converter, and the frequency difference between the frequency different from the first switching frequency and the first switching frequency is greater than the difference threshold, then the first switching device of the first converter is controlled to turn on or off to convert the first DC power into the first AC power; the switching frequency of the first switching device is the frequency in the circulating current that is different from the first switching frequency. The second converter is used to control the switching of a second switching device of the second converter to convert the second direct current into a second alternating current when there is a frequency in the circulating current that is different from the first switching frequency; the switching frequency of the second switching device is a frequency in the circulating current that is different from the first switching frequency. The transformer is used to adjust the AC voltage corresponding to the first AC power and the AC voltage corresponding to the second AC power.

2. The system of claim 1, wherein, The first converter is specifically used for: If the frequency of the circulating current is the same as the first switching frequency, then the first switching device of the first converter is turned on or off to convert the first DC power into the first AC power; the switching frequency of the first switching device is the first switching frequency.

3. The system of claim 1, wherein, The first converter is specifically used for: If the frequency difference is less than or equal to a set difference threshold, the first switching device of the first converter is controlled to turn on or off to convert the first DC power into the first AC power; the switching frequency of the first switching device is the first switching frequency.

4. The system according to any of claims 1-3, characterized in that, The first converter is also used for: Based on the port voltage corresponding to the first converter, the first switching moment of the first switching device in the switching cycle of the first converter is determined; the first switching moment includes the on moment and the off moment of the first switching device.

5. The system of claim 4, wherein, The first converter is specifically used for: The first switching device of the first converter is controlled to turn on or off to convert the first DC power into the first AC power; the switching frequency of the first switching device is a frequency that is different from the first switching frequency or the frequency of the circulating current; and the switching time of the first switching device is the first switching time.

6. The system according to any one of claims 1-5, characterized in that, The second converter is specifically used for: determining a second switching time of a second switching device of the second converter in a switching period according to a port voltage corresponding to the second converter; the second switching time comprises a turn-on time and a turn-off time of the second switching device; controlling turn-on or turn-off of the second switching device of the second converter to convert the second direct current into the second alternating current; a switching frequency of the second switching device is a frequency different from the first switching frequency in the frequency of the circulating current, and a switching time of the second switching device is the second switching time.

7. The system according to any of claims 4-6, characterized in that, The first switching time is the same as the second switching time.

8. A multi-type converter AC coupling system control method, characterized by, The method is applied to a first converter in a multi-type converter alternating current coupling system; the multi-type converter alternating current coupling system further comprises a first direct current source, a second direct current source, a second converter and a transformer; the first direct current source is connected with the first converter; the second direct current source is connected with the second converter; The first converter and the second converter are connected in parallel to the transformer; The types of the first converter and the second converter are different; the method comprises: controlling the frequency of the circulating current in the multi-type converter alternating current coupling system; If there is a frequency different from the first switching frequency of the first converter in the frequency of the circulating current, and the frequency difference between the frequency and the first switching frequency is greater than a difference threshold, controlling turn-on or turn-off of a first switching device of the first converter to convert a first direct current into a first alternating current; the first direct current is provided by the first direct current source to the first converter; a switching frequency of the first switching device is the frequency different from the first switching frequency in the frequency of the circulating current.

9. The method of claim 8, wherein, The method further comprises: If the frequency of the circulating current is the same as the first switching frequency, controlling turn-on or turn-off of a first switching device of the first converter to convert the first direct current into the first alternating current; a switching frequency of the first switching device is the first switching frequency.

10. The method of claim 8, wherein, The method further comprises: If the frequency difference is less than or equal to the difference threshold, controlling turn-on or turn-off of a first switching device of the first converter to convert the first direct current into the first alternating current; a switching frequency of the first switching device is the first switching frequency.

11. The method according to any one of claims 8-10, characterized in that, The method further comprises: determining a first switching time of a first switching device of the first converter in a switching period according to a port voltage corresponding to the first converter; the first switching time comprises a turn-on time and a turn-off time of the first switching device; the first switching time is the same as the second switching time of the second converter.

12. The method of claim 11, wherein, controlling turn-on or turn-off of the first switching device of the first converter to convert the first direct current into the first alternating current based on the first switching frequency, comprises: Controlling the turn-on or turn-off of a first switching device of the first converter converts the first direct current into the first alternating current; a switching frequency of the first switching device is a frequency different from the first switching frequency among the first switching frequency or the frequency of the circulating current, and a switching time of the first switching device is the first switching time.

Images