Carrier modulation method of converter system

Abstract

The invention provides a carrier modulation method of a converter system. The converter system comprises a plurality of converters connected in parallel. The plurality of converters comprise a master converter and a slave converter. The output ends of the plurality of converters are connected to the bus. The bus is connected with a grid. The carrier modulation method comprises the following steps: determining a bus voltage phase of a bus according to slave converter detection parameters at the output end of a slave converter; the parameters detected from the converter comprise at least one of active power, reactive power, voltage and current; acquiring an actual carrier phase of the slave converter when the bus voltage phase reaches a set phase; determining a reference carrier phase of the slave converter; and adjusting the actual carrier phase of the slave converter to the reference carrier phase of the slave converter. According to the method, the actual carrier phase of the slave converter can be accurately determined, so that the multiple converters connected in parallel can apply a carrier modulation method to suppress higher harmonics on the power grid side.

Description

Technical Field

[0001] The present application relates to the technical field of converter modulation, and in particular to a carrier modulation method for a converter system. Background Art

[0002] The parallel grid-connected converter system can use the carrier interleaving phase shifting method to suppress high-order and ultra-high-order harmonics on the bus, thereby reducing the current distortion rate on the grid side. The existing related technologies are mainly aimed at centralized parallel converters, which simultaneously obtain the carrier phase of all converters, and then adjust the actual relative carrier phase of the slave converter according to the pre-calculated reference carrier phase, thereby achieving harmonic suppression.

[0003] However, for multi-access parallel grid-connected converter systems, due to the long physical distance between converters, the signal communication delay will increase significantly, making it difficult to simultaneously determine the phase detection time of all converters. Since the carrier frequency is generally several kilohertz or above, the communication delay will be greater than the carrier period, which can easily lead to failure of the converter carrier phase modulation, reducing the reliability of system operation.

[0004] It can be seen that for multiple parallel grid-connected converters, the existing centralized carrier phase modulation method has poor applicability and needs to be improved urgently. Summary of the invention

[0005] The present application provides a carrier modulation method applicable to a multi-parallel grid-connected converter system.

[0006] The present application provides a carrier modulation method for a converter system, wherein the converter system includes a plurality of converters connected in parallel, wherein the plurality of converters include a master converter and a slave converter, wherein output ends of the plurality of converters are connected to a bus, and the bus is connected to a power grid; the carrier modulation method includes:

[0007] Determine the bus voltage phase of the bus according to the slave converter detection parameter at the output end of the slave converter; the slave converter detection parameter includes at least one of active power, reactive power, voltage and current;

[0008] Acquire the actual carrier phase of the slave converter when the bus voltage phase reaches the set phase;

[0009] determining a reference carrier phase of the slave converter;

[0010] The actual carrier phase of the slave converter is adjusted to a reference carrier phase of the slave converter.

[0011] Optionally, the acquiring the actual carrier phase of the slave converter when the bus voltage phase reaches the set phase includes:

[0012] The actual carrier phase of the slave converter is obtained when the bus voltage phase passes through zero.

[0013] Optionally, the obtaining the actual carrier phase of the slave converter when the bus voltage phase passes through zero includes:

[0014] When the bus voltage phase is in a preset interval, obtaining the current actual carrier phase of the slave converter; the preset interval includes a zero point;

[0015] The actual carrier phase when the bus voltage phase passes through zero is determined according to the current actual carrier phase.

[0016] Optionally, the current actual carrier phase includes a first actual carrier phase and a second actual carrier phase, and the bus voltage phase includes a first bus voltage phase and a second bus voltage phase;

[0017] The determining, according to the current actual carrier phase, the actual carrier phase when the bus voltage phase passes through zero includes:

[0018] When the bus voltage phase is in a preset interval, obtaining a first actual carrier phase and a first bus voltage phase of the slave converter at a current sampling moment;

[0019] Obtaining a second actual carrier phase and a second bus voltage phase of the slave converter at a next sampling moment;

[0020] The actual carrier phase of the slave converter when the bus voltage phase passes through zero is determined by interpolation based on the first actual carrier phase, the first bus voltage phase, the second actual carrier phase and the second bus voltage phase.

[0021] Optionally, the preset interval is determined according to a sampling frequency of the parameter detected by the slave converter and a basic frequency of the power grid.

[0022] Optionally, determining the reference carrier phase of the slave converter includes:

[0023] determining an actual carrier phase of the main converter;

[0024] determining a phase offset;

[0025] A reference carrier phase of the slave converter is determined according to the actual carrier phase of the master converter and the phase offset.

[0026] Optionally, determining the actual carrier phase of the main converter includes:

[0027] Determine the bus voltage phase of the bus according to the main converter detection parameter of the output end of the main converter; the main converter detection parameter includes at least one of active power, reactive power, voltage and current;

[0028] The actual carrier phase of the main converter is obtained when the bus voltage phase reaches the set phase.

[0029] Optionally, determining the phase offset includes:

[0030] Obtaining the higher harmonic frequency of the power grid;

[0031] Acquiring a carrier frequency of the converter system;

[0032] The phase offset is determined according to the corresponding relationship between the higher harmonic frequency, the carrier frequency and the carrier phase difference.

[0033] Optionally, adjusting the actual carrier phase of the slave converter to the reference carrier phase of the slave converter includes:

[0034] Determining an actual carrier frequency of the slave converter according to an actual carrier phase of the slave converter;

[0035] determining a reference carrier frequency of the slave converter according to a reference carrier phase of the slave converter;

[0036] The actual carrier frequency of the slave converter is adjusted to the reference carrier frequency of the slave converter.

[0037] The present application provides a computer-readable storage medium having a program stored thereon. When the program is executed by a processor, the carrier modulation method of the converter system described in any one of the above items is implemented.

[0038] In some embodiments, the bus voltage phase of the bus is determined based on the slave converter detection parameters at the output end of the slave converter, and the actual carrier phase of the slave converter when the bus voltage phase reaches the set phase is obtained. In this way, the actual carrier phase of the slave converter at the same time can be obtained, and the actual carrier phase of the slave converter can be accurately determined, so that multiple converters connected in parallel can apply carrier modulation methods to suppress high-order harmonics on the grid side.

[0039] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0041] Figure 1 Shown is a circuit diagram of an embodiment of a converter system to which the carrier modulation method of the converter system of the present application is applied.

[0042] Figure 2 FIG. 1 is a flow chart of an embodiment of a carrier modulation method of a converter system of the present application.

[0043] Figure 3 Shown is the vector relationship between the voltage at the output and the bus voltage.

[0044] Figure 4 Shown is a control block diagram of an embodiment of a carrier modulation method for a converter system of the present application.

[0045] Figure 5 Shown is a circuit diagram of another embodiment of a converter system to which the carrier modulation method of the converter system of the present application is applied.

[0046] Figure 6 Shown is a structural block diagram of an embodiment of a carrier modulation device of a converter system of the present application. DETAILED DESCRIPTION

[0047] The present application provides a carrier modulation method for a converter system. The carrier modulation method for a converter system of the present application is described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the features of the following embodiments and implementations can be combined with each other.

[0048] Figure 1 FIG. 1 is a circuit diagram of an embodiment of a converter system 10 to which the carrier modulation method of the converter system of the present application is applied. Figure 1 As shown, the converter system 10 includes a plurality of converters 100 connected in parallel. The plurality of converters 100 include a master converter 11 and a slave converter 12. The converter system 10 may include one slave converter 12, or may include a plurality of slave converters 12. The plurality of converters 100 may be grid-following converters or grid-forming converters. The output terminals POC of the plurality of converters 100 are connected to the bus PCC. The bus PCC is connected to the power grid E. The converter system 10 is a distributed converter system 10, and the plurality of converters 100 are located in different places.

[0049] Figure 2 FIG. 1 is a flow chart of an embodiment of a carrier modulation method 20 of a converter system of the present application.

[0050] The carrier modulation method 20 of the converter system includes:

[0051] Step 21, determining the bus voltage phase of the bus PCC according to the slave converter detection parameter of the output terminal POC of the slave converter 12. The slave converter detection parameter includes at least one of active power, reactive power, voltage and current.

[0052] According to the slave converter detection parameter of the output terminal POC of the slave converter 12 , the voltage phase of the output terminal POC can be determined, and then the bus voltage phase can be determined.

[0053] For a grid-following converter, the parameters detected from the converter include voltage. By sampling the output voltage of the output terminal POC, the voltage phase of the output terminal POC can be determined. The output voltage of the output terminal POC can be obtained by sampling the phase-locked loop. Taking a second-order generalized integral phase-locked loop as an example, the voltage phase of the output terminal POC is determined by formulas (1) to (3).

[0054]

[0055] Among them, V POC is the output voltage of the output terminal POC, θ POC is the voltage phase of the output terminal POC, V POC(α) is the vector synchronized with the voltage signal of the power grid E, V * POC(α) is the vector of the voltage signal of the lagging grid E by 90°; SOGI is the resonant frequency of the phase-locked loop; ε is the gain coefficient of the phase-locked loop; k p_PLL is the proportional gain of the PI regulator; k i_PLL is the integral coefficient of the PI regulator.

[0056] For the grid-type converter, the voltage phase θ of the output terminal POC POC It can be directly obtained through the power loop. Taking the virtual synchronous machine as an example, the voltage phase θ of the output terminal POC POC It can be determined by formula (4).

[0057]

[0058] Among them, ω GFM is the output angular frequency of the virtual synchronous machine; ω0 is the reference angular frequency of the virtual synchronous machine; P e is the actual output power; P ref is the reference output power; D is the virtual damping; J is the virtual inertia.

[0059] When the power grid is in steady state operation and power tracking is accurate, the active power reference value and reactive power reference value can be used to replace the actual power. Let k be the kth sampling period, and the voltage phase θ of the output terminal POC is POC The voltage relationship with the bus PCC is shown in formula (5):

[0060]

[0061] Among them, P ref (k) is the active power reference value, Q ref (k) is the reactive power reference value, is the current at the output terminal POC, is the voltage at the output terminal POC, R L , X L is the line impedance, is the voltage of bus PCC.

[0062] When the line impedance remains unchanged, the phase difference Δθ(k) between the bus PCC and the output POC is as shown in formula (6):

[0063]

[0064] Then the bus voltage phase θ can be obtained PCC (k):

[0065] θ PCC (k) = θ POC (k)+Δθ(k) Formula (7)

[0066] Figure 3 The vector relationship between the voltage at the output terminal POC and the bus voltage is shown.

[0067] Step 22, obtaining the actual carrier phase of the slave converter 12 when the bus voltage phase reaches the set phase.

[0068] If the converter system 10 includes multiple slave converters 12, the actual carrier phases of the multiple slave converters 12 at the same time can be obtained through step 22. For multiple distributed slave converters 12, the problem of being unable to determine the sampling time of the actual carrier phase due to communication delay is solved.

[0069] Step 23 , determining the reference carrier phase of the slave converter 12 .

[0070] The reference carrier phase is determined based on the higher harmonics that need to be suppressed in the power grid E. The reference carrier phase is a target carrier phase modulated by the slave converter 12 .

[0071] Step 24 , adjusting the actual carrier phase of the slave converter 12 to the reference carrier phase of the slave converter 12 .

[0072] After determining the actual carrier phase and the reference carrier phase of the slave converter 12, the actual carrier phase of the slave converter 12 is adjusted to the reference carrier phase to achieve high-order harmonic suppression of the power grid E. For multiple slave converters 12, the actual carrier phase and the reference carrier phase of each slave converter 12 are determined, and the actual carrier phase of each slave converter 12 is adjusted to the corresponding reference carrier phase.

[0073] In some embodiments, the bus voltage phase of the bus PCC is determined based on the slave converter detection parameters at the output end of the slave converter 12, and the actual carrier phase of the slave converter 12 when the bus voltage phase reaches the set phase is obtained. In this way, the actual carrier phase of the slave converter 12 at the same time can be obtained, and the actual carrier phase of the slave converter 12 can be accurately determined, so that multiple converters 100 connected in parallel can apply a carrier modulation method to suppress higher harmonics on the grid side.

[0074] In some embodiments, step 22 includes: obtaining an actual carrier phase of the slave converter 12 when the bus voltage phase passes through zero.

[0075] The bus voltage phase has a better linear characteristic near the zero-crossing point. By determining the specific phase as the bus voltage phase at the zero-crossing point, the actual carrier phase of the slave converter 12 at that moment can be obtained more accurately.

[0076] In some embodiments, the method of obtaining the actual carrier phase of the slave converter 12 when the bus voltage phase passes through zero includes: when the bus voltage phase is in a preset interval, obtaining the current actual carrier phase of the slave converter 12; the preset interval includes a zero point; and determining the actual carrier phase when the bus voltage phase passes through zero based on the current actual carrier phase.

[0077] The preset interval is a phase interval including the zero point. Considering that there may be slight jitters in the voltage phase angle of the power grid E or unknown angle changes caused by power quality problems or sudden changes in the output power of the converter, a preset interval in which the bus voltage phase may pass through zero can be set. Since the sampling of the parameters detected from the converter is discrete, it cannot be guaranteed that the sampling is performed exactly when the bus voltage phase passes through zero. Therefore, when the bus voltage phase enters the preset interval, the calculation of the actual carrier phase when the bus voltage phase passes through zero is triggered. It is not necessary to determine the actual carrier phase when the bus voltage phase passes through zero during the sampling process, which can reduce the amount of calculation.

[0078] In some embodiments, the preset interval is determined according to the sampling frequency of the parameter detected from the converter and the basic frequency of the power grid E.

[0079] The bus voltage phase difference between two adjacent samplings can be determined by formula (8).

[0080]

[0081] Among them, Δθ PCC is the bus voltage phase difference between two adjacent samplings, f c is the sampling frequency of the parameters detected from the converter, and f0 is the basic frequency of the power grid E.

[0082] Set the preset interval S = [-θ s ,θ s ],θ s =Δθ PCC The preset interval is determined according to the bus voltage phase difference between two adjacent samples, so that the zero crossing point of the bus voltage phase will not be missed, and the actual carrier phase when the bus voltage phase crosses zero does not need to be calculated multiple times.

[0083] In some embodiments, the current actual carrier phase includes a first actual carrier phase and a second actual carrier phase, and the bus voltage phase includes a first bus voltage phase and a second bus voltage phase; and determining the actual carrier phase when the bus voltage phase passes through zero according to the current actual carrier phase includes:

[0084] When the bus voltage phase is in a preset interval, obtaining a first actual carrier phase and a first bus voltage phase at a current sampling moment of the slave converter 12;

[0085] Obtaining a second actual carrier phase and a second bus voltage phase at a next sampling moment from the converter 12;

[0086] According to the first actual carrier phase, the first bus voltage phase, the second actual carrier phase and the second bus voltage phase, the actual carrier phase of the slave converter 12 when the bus voltage phase passes through zero is determined by interpolation.

[0087] Assume that the first bus voltage phase θ is detected at the sampling period k PCC (k), θ PCC (k)∈S, it will trigger the calculation of the actual carrier phase when the bus voltage phase passes zero, and trigger the detection of the carrier phase, record the first actual carrier phase φ(k) at this time, and record the second bus voltage phase θ at the next detection time k+1 PCC (k+1) and the second actual carrier phase φ(k+1). Since fixed rate sampling is used and the zero-crossing calculation is enabled within a fixed angular width range, it is impossible to directly obtain the actual carrier phase φ when the bus voltage phase crosses zero θPCC＝0 Since the bus voltage has good linear characteristics near the zero-crossing point, the linear interpolation method can be used to approximate the actual carrier phase φ at the time when the bus voltage phase crosses zero. θPCC＝0 , as shown in formula (9).

[0088]

[0089] Where sgn represents the sign function. When the input is positive, the function value is 1, otherwise it is -1.

[0090] In some embodiments, step 23 includes: determining an actual carrier phase of the master converter 11 ; determining a phase offset; and determining a reference carrier phase of the slave converter 12 based on the actual carrier phase of the master converter 11 and the phase offset.

[0091] Due to the application of carrier modulation technology, the phase difference between adjacent converters 100 is consistent. Therefore, according to the actual carrier phase and phase offset of the master converter 11, the reference carrier phase of the slave converter 12 can be determined. For a converter system 10 including multiple slave converters 12, the actual carrier phase of the master converter 11 is set to φ1, and the phase offset is Δφ * , then the reference carrier phase of slave converter 12 No. 2 is φ ref,2 =φ1+Δφ * , the reference carrier phase of slave converter 12 is φ ref,2 =φ1+2Δφ * , and so on.

[0092] In some embodiments, determining the actual carrier phase of the main converter 11 includes: determining the bus voltage phase of the bus PCC according to the main converter detection parameters at the output end of the main converter 11; the main converter detection parameters include at least one of active power, reactive power, voltage, and current; obtaining the actual carrier phase of the main converter 11 when the bus voltage phase reaches the set phase.

[0093] The set phase is consistent with the "set phase" in step 22. In this way, the actual carrier phases of the master converter 11 and the slave converter 12 can be obtained at the same time to ensure successful carrier modulation. According to the master converter detection parameters at the output end of the master converter 11, the bus voltage phase of the bus PCC can be determined by referring to the above formulas (1) to (7).

[0094] In some embodiments, determining the phase offset includes: obtaining the higher harmonic frequency of the power grid E; obtaining the carrier frequency of the converter system 10; and determining the phase offset according to the corresponding relationship between the higher harmonic frequency, the carrier frequency and the carrier phase difference.

[0095] Assume the high-order harmonic frequency of the power grid E is f x , the carrier frequency of the converter system 10 is f c , we can get The corresponding relationship between the coefficient m and the carrier phase difference is a known relationship and can be obtained by looking up a table and calculating. According to the corresponding relationship, the phase offset Δφ can be determined.

[0096] In order to prevent the carrier phase from frequently jittering, the dead zone value of the phase offset of the carrier phase shift is set as follows:

[0097]

[0098] where τ is the threshold, Δφ * is the final phase offset.

[0099] In some embodiments, step 24 includes: determining an actual carrier frequency of the slave converter 12 based on an actual carrier phase of the slave converter 12; determining a reference carrier frequency of the slave converter 12 based on a reference carrier phase of the slave converter 12; and adjusting the actual carrier frequency of the slave converter 12 to the reference carrier frequency of the slave converter 12.

[0100] A proportional regulator is used to dynamically adjust the actual carrier frequency of the slave converter 12, as shown in formula (11):

[0101]

[0102] where k φ is the proportional gain of the carrier frequency regulator, f c is the actual carrier frequency from the converter 12, and f cref is the reference carrier frequency of the slave converter 12. By means of the above-mentioned dynamic frequency adjustment method, the relative phase of the carrier of the converter system 10 can be slowly adjusted until it completes the interleaving.

[0103] For multiple slave converters 12, the reference carrier frequency of each slave converter 12 is determined according to the reference carrier phase of each slave converter 12, and the actual carrier frequency of each slave converter 12 is adjusted to the reference carrier frequency of the slave converter 12. After the modulation is completed, the actual carrier phase of each slave converter 12 is staggered, and the actual carrier frequencies should be equal.

[0104] Figure 4 FIG. 1 is a control block diagram of an embodiment of a carrier modulation method 20 of a converter system of the present application.

[0105] The bus voltage phase is calculated based on the sampled master converter detection parameters and slave converter detection parameters, and the bus voltage phase zero crossing detection is performed to determine the actual carrier phase when the bus voltage phase crosses zero. The reference carrier phase is determined based on the actual carrier phase and phase offset of the master converter. Based on the limit difference between the actual carrier phase and the reference carrier phase, the carrier frequency of the slave converter 12 is adjusted under the preset dead zone limit so that the carrier frequency of the slave converter 12 reaches the reference carrier frequency.

[0106] Figure 5FIG. 1 is a circuit diagram of another embodiment of a converter system 10 to which the carrier modulation method of the converter system of the present application is applied.

[0107] exist Figure 5 In the illustrated embodiment, the converter system 10 includes two converters, a grid-type converter No. 1 and a grid-following converter No. 2. The grid-type converter No. 1 includes a three-phase converter 1 and a filter 1. The grid-following converter No. 2 includes a three-phase converter 2 and a filter 2. The output end of the grid-type converter No. 1 is POC1, which is connected to the bus PCC through line 1. The output end of the grid-following converter No. 2 is POC2, which is connected to the bus PCC through line 2. The bus PCC is connected to the power grid.

[0108] When applying the carrier modulation method 20 of the converter system of the present application, first determine the higher harmonics to be suppressed in the power grid and the carrier frequency of the converter system 10 when no modulation is performed. According to the corresponding relationship between the higher harmonic frequency, the carrier frequency and the carrier phase difference, the phase offset is determined. The preset interval is determined according to the sampling frequency of the detection parameters of the slave converter and the basic frequency of the power grid E. The No. 1 grid-type converter is used as the main converter and the No. 2 grid-type converter is used as the slave converter. According to the detection parameters of the main converter at the output end POC1, the bus voltage phase is determined. At the same time, according to the detection parameters of the slave converter at the output end POC2, the bus voltage phase is determined. Determine the actual carrier phase of the No. 1 grid-type converter and the No. 2 grid-type converter at the zero-crossing moment of the bus voltage phase. According to the actual carrier phase of the No. 1 grid-type converter and the phase offset, determine the reference carrier phase of the No. 2 grid-type converter. Then, the carrier frequency of the No. 2 grid-following converter is adjusted so that its actual carrier phase reaches its reference carrier phase, realizing carrier interleaving phase shifting, thereby achieving the purpose of suppressing high-order harmonics of the power grid.

[0109] Figure 6 Shown is a structural block diagram of an embodiment of a carrier modulation device of a converter system of the present application.

[0110] like Figure 6 As shown, the carrier modulation device of the converter system includes one or more processors 31, which are used to implement the carrier modulation method 20 of the converter system as described above.

[0111] In some embodiments, the carrier modulation device of the converter system may include a computer-readable storage medium 32, which may store a program that can be called by the processor 31 and may include a non-volatile storage medium. In some embodiments, the carrier modulation device of the converter system may include a memory 33 and an interface 34. In some embodiments, the carrier modulation device of the converter system may also include other hardware according to actual applications.

[0112] The computer-readable storage medium 32 of the embodiment of the present application stores a program thereon, and when the program is executed by the processor 31, it is used to implement the carrier modulation method 20 of the converter system described above.

[0113] The present application may take the form of a computer program product implemented on one or more computer-readable storage media 32 (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing program code. The computer-readable storage medium 32 includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. The information can be a computer-readable instruction, a data structure, a module of a program, or other data. Examples of computer-readable storage media 32 include but are not limited to: phase change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technology, read-only compact disk read-only memory (CD-ROM), digital versatile disk (DVD) or other optical storage, magnetic cassette, tape disk storage or other magnetic storage device or any other non-transmission medium that can be used to store information that can be accessed by a computing device.

Claims

1. A carrier modulation method for a converter system, characterized in that: The converter system includes a plurality of converters connected in parallel, the plurality of converters include a master converter and a slave converter, the output ends of the plurality of converters are connected to a bus, and the bus is connected to a power grid; the carrier modulation method includes: Determine the bus voltage phase of the bus according to the slave converter detection parameter at the output end of the slave converter; the slave converter detection parameter includes at least one of active power, reactive power, voltage and current; Acquire the actual carrier phase of the slave converter when the bus voltage phase reaches the set phase; determining a reference carrier phase of the slave converter; The actual carrier phase of the slave converter is adjusted to a reference carrier phase of the slave converter.

2. The carrier modulation method of the converter system according to claim 1, characterized in that: The obtaining the actual carrier phase of the slave converter when the bus voltage phase reaches the set phase includes: The actual carrier phase of the slave converter is obtained when the bus voltage phase passes through zero.

3. The carrier modulation method of the converter system according to claim 2, characterized in that: The obtaining of the actual carrier phase of the slave converter when the bus voltage phase passes through zero includes: When the bus voltage phase is in a preset interval, obtaining the current actual carrier phase of the slave converter; the preset interval includes a zero point; The actual carrier phase when the bus voltage phase passes through zero is determined according to the current actual carrier phase.

4. The carrier modulation method of the converter system according to claim 3, characterized in that: The current actual carrier phase includes a first actual carrier phase and a second actual carrier phase, and the bus voltage phase includes a first bus voltage phase and a second bus voltage phase; The determining, according to the current actual carrier phase, the actual carrier phase when the bus voltage phase passes through zero includes: When the bus voltage phase is in a preset interval, obtaining a first actual carrier phase and a first bus voltage phase of the slave converter at a current sampling moment; Obtaining a second actual carrier phase and a second bus voltage phase of the slave converter at a next sampling moment; The actual carrier phase of the slave converter when the bus voltage phase passes through zero is determined by interpolation based on the first actual carrier phase, the first bus voltage phase, the second actual carrier phase and the second bus voltage phase.

5. The carrier modulation method of the converter system according to claim 3, characterized in that: The preset interval is determined according to a sampling frequency of the parameter detected by the slave converter and a basic frequency of the power grid.

6. The carrier modulation method of the converter system according to claim 1, characterized in that: The determining of the reference carrier phase of the slave converter comprises: determining an actual carrier phase of the main converter; determining a phase offset; A reference carrier phase of the slave converter is determined according to the actual carrier phase of the master converter and the phase offset.

7. The carrier modulation method of the converter system according to claim 6, characterized in that: The determining the actual carrier phase of the main converter comprises: Determine the bus voltage phase of the bus according to the main converter detection parameter of the output end of the main converter; the main converter detection parameter includes at least one of active power, reactive power, voltage and current; The actual carrier phase of the main converter is obtained when the bus voltage phase reaches the set phase.

8. The carrier modulation method of the converter system according to claim 6, characterized in that: The determining of the phase offset comprises: Obtaining the higher harmonic frequency of the power grid; Acquiring a carrier frequency of the converter system; The phase offset is determined according to the corresponding relationship between the higher harmonic frequency, the carrier frequency and the carrier phase difference.

9. The carrier modulation method of the converter system according to claim 1, characterized in that: The adjusting the actual carrier phase of the slave converter to the reference carrier phase of the slave converter comprises: Determining an actual carrier frequency of the slave converter according to an actual carrier phase of the slave converter; determining a reference carrier frequency of the slave converter according to a reference carrier phase of the slave converter; The actual carrier frequency of the slave converter is adjusted to the reference carrier frequency of the slave converter.

10. A computer-readable storage medium, characterized in that: A program is stored thereon, and when the program is executed by a processor, the carrier modulation method of the converter system according to any one of claims 1 to 9 is implemented.

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