A phase compensation carrier phase-shift modulation method for inhibiting common mode electromagnetic interference of MMC

Abstract

The application provides a phase compensation type carrier phase-shift modulation method for inhibiting common-mode electromagnetic interference of an MMC, comprising the following steps: under the condition of a same phase of a first term and a phase tolerance of a typical carrier phase-shift modulation three-phase multi-carrier of a modular multilevel converter (MMC), calculating phase differences between three-phase upper bridge arm voltage pulses and phase differences between three-phase lower bridge arm voltage pulses to obtain calculation results; wherein the three phases comprise an A phase, a B phase and a C phase; keeping all sub-module carrier phases of the A phase unchanged, increasing corresponding compensation values of sub-module carrier phases of the B phase and the C phase according to the calculation results to obtain updated carrier signals of each sub-module of the MMC; comparing voltage reference signals of each sub-module of the MMC with the updated carrier signals to generate driving pulses and apply the driving pulses to each sub-module of the MMC. Through the method, common-mode voltage fluctuation of the MMC is reduced without reducing direct current voltage utilization of carrier phase-shift modulation of the MMC.

Description

Technical Field

[0001] This invention belongs to the field of power electronics technology. Background Technology

[0002] Modular multilevel converters (MMCs) have broad application prospects in flexible high-voltage direct current transmission and medium- and high-voltage motor drives, offering numerous advantages such as high modularity, low harmonics, and no DC bus capacitor. MMC modulation methods are mainly divided into two categories: (1) low switching frequency modulation, such as nearest-level approximation modulation; and (2) high switching frequency modulation, such as phase-compensated carrier phase-shift modulation and carrier-stacked sinusoidal pulse width modulation. Among these, phase-compensated carrier phase-shift modulation is suitable for MMCs with lower level numbers.

[0003] However, current research on MMCs (Multi-Mode Conversion Machines) has yielded very little attention regarding common-mode electromagnetic interference (EMC). In reality, MMCs contain high-frequency common-mode voltage jumps. When using phase-compensated carrier phase-shift modulation, the amplitude of each MMC common-mode voltage jump is 1 / 6 of the submodule capacitor voltage, and the jump frequency is 6N times the carrier frequency, where N is the number of individual bridge arm submodules in the MMC. This presence is not negligible. High-frequency common-mode voltage can generate leakage current and common-mode interference through stray capacitance, damaging load motor bearings, converters, and communication systems near the lines, among other things, and urgently needs to be addressed.

[0004] Low common-mode electromagnetic interference modulation methods applicable to MMC have the advantages of small hardware changes and low cost, and therefore have been studied to some extent in the past few years. MMC low common-mode electromagnetic interference modulation is mainly divided into two categories: (1) modulation to reduce common-mode voltage fluctuations; (2) carrier spread spectrum modulation.

[0005] Previous literature has proposed that, based on MMC carrier stacking modulation, the pulse portion of the bridge arm voltage reference signal is compared with a sawtooth carrier, so that the rising edge time of the bridge arm voltage pulse is determined by the falling edge time of the previous phase bridge arm voltage pulse, and the falling edge time is determined by the sum of the falling edge time of the previous phase pulse and the pulse duration. This achieves the rearrangement of the MMC bridge arm voltage pulses, so that the voltage pulses of the upper and lower bridge arms of the three phases are connected end to end, thereby reducing the common-mode voltage fluctuation under MMC carrier stacking modulation and suppressing the common-mode electromagnetic interference generated by MMC.

[0006] Alternatively, based on the closest level approximation modulation of the MMC, a specific set of zero common-mode voltage vectors can be selected. The switching signals of each sub-module of the MMC can be determined by the zero common-mode voltage vector closest to the reference voltage vector, so that the sum of the voltages of the three-phase upper bridge arms of the MMC remains constant, thereby suppressing the common-mode electromagnetic interference of the MMC.

[0007] Alternatively, a six-segment carrier stacked modulation method can be proposed to reduce MMC common-mode electromagnetic interference. By dividing the power frequency cycle into six intervals based on the magnitude relationship of the three-phase reference voltage, the number of phase bridge arm submodules with amplitude at the maximum or minimum value in each interval is directly determined by the reference signal and carrier stacked modulation. However, the number of phase bridge arm submodules with amplitude at the intermediate value is determined by subtracting the sum of the number of other two phase bridge arm submodules from 3N / 2. The number of submodules put into operation is adjusted in real time to achieve constant MMC common-mode voltage.

[0008] Alternatively, a variable switching frequency modulation method suitable for single-phase MMC is proposed, which uses a lower frequency carrier at the peak position of the sinusoidal reference signal and a higher frequency carrier at the zero-crossing position of the reference signal, thereby reducing the peak value of the switching frequency and its multiples in the voltage spectrum of the MMC bridge arm and achieving suppression of common-mode electromagnetic interference in MMC.

[0009] Alternatively, a chaotic carrier phase-shift modulation method was proposed, which makes the carrier frequency of the MMC submodule change chaotically within a certain range, and diffuses the peak energy in the differential-mode voltage and common-mode voltage spectrum to the entire spectrum, thereby reducing the peak value of the MMC common-mode voltage spectrum.

[0010] The aforementioned low common-mode electromagnetic interference (EMC) modulation methods suppress common-mode EMC at its source. However, current common-mode voltage constant MMC carrier phase-shifting methods suffer from reduced DC voltage utilization. During the rearrangement of the bridge arm voltage pulses, the pulse width and overall pulse phase are altered. Compared to typical MMC carrier phase-shifting modulation, the DC voltage utilization of this method is reduced to 0.866 of its original value. While carrier spread spectrum modulation can suppress the peak value of the MMC common-mode voltage spectrum to some extent, the peak value of the common-mode voltage time-domain fluctuation is not reduced, and the suppression effect on the common-mode voltage spectrum peak value is far less than that of the MMC common-mode voltage constant method.

[0011] To address this, the present invention proposes a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference. This method reduces MMC common-mode voltage fluctuations to zero without reducing the DC voltage utilization rate of MMC carrier phase-shift modulation. Summary of the Invention

[0012] The present invention aims to at least partially solve one of the technical problems in the related art.

[0013] Therefore, the purpose of this invention is to propose a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference, which can reduce MMC common-mode voltage fluctuations without reducing the DC voltage utilization rate of MMC carrier phase-shift modulation.

[0014] To achieve the above objectives, a first aspect of the present invention provides a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference, comprising:

[0015] Under the condition of the same phase first term and phase tolerance of three-phase multi-carrier phase-shift modulation in a modular multilevel converter (MMC), the phase difference between the voltage pulses of the upper arm of the three phases and the phase difference between the voltage pulses of the lower arm of the three phases are calculated respectively, and the calculation results are obtained; wherein, the three phases include phase A, phase B and phase C;

[0016] Keeping the carrier phases of all submodules in phase A unchanged, the carrier phases of each submodule in phases B and C are increased by corresponding compensation values ​​according to the calculation results, so as to obtain the updated carrier signals of each submodule of MMC;

[0017] The voltage reference signals of each MMC submodule are compared with the updated carrier signal to generate drive pulses that are applied to each MMC submodule.

[0018] In addition, the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference according to the above embodiments of the present invention may also have the following additional technical features:

[0019] Furthermore, in one embodiment of the present invention, the typical carrier phase-shift modulation of MMC includes:

[0020] When an isosceles triangular carrier wave with the same amplitude and period is applied to each sub-module of the MMC, the initial phase of the carrier wave of each sub-module in the upper phase bridge arm is arranged in an arithmetic sequence with the first term being 0 and the tolerance being 2π / N. The initial phase of the carrier wave of each sub-module in the lower phase bridge arm is arranged in an arithmetic sequence with the first term being π / N and the tolerance being 2π / N.

[0021] The voltage reference signal of each bridge arm is evenly distributed to each sub-module within each bridge arm. The pulse drive signal of each sub-module within each bridge arm is obtained by comparing the per-unit value of the voltage reference signal of each sub-module within each bridge arm with the triangular carrier signal.

[0022] Further, in one embodiment of the present invention, the step of keeping the carrier phases of all sub-modules in phase A unchanged, and increasing the carrier phases of each sub-module in phases B and C by a corresponding compensation value according to the calculation result, includes:

[0023] Define the corresponding time offset τ of the in-phase upper arm. pj Let j = a, b, c. Within one control cycle T, make the voltage pulse rising edge time t of the j-phase numbered x submodule so that... prjx Increase carrier time offset τ pj Then, at the falling edge time t of the voltage pulse of the previous phase k-numbered y submodule. pfkyIncrease carrier time offset τ pk After phase coherence, the k values ​​corresponding to j = a, b, c are c, a, b, and m is any integer. The mathematical expression is: t prjx +τ pj =t pfky +τ pk +mT.

[0024] Further, in one embodiment of the present invention, after adding the corresponding compensation value to the carrier phase of each submodule of phase B and phase C according to the calculation result, the voltage pulses of the upper and lower arms of the three-phase MMC all satisfy the following: the rising edge time of the voltage pulse of submodule i of phase b is consistent with the falling edge time of the voltage pulse of submodule i of phase a; the rising edge time of the voltage pulse of submodule i1 of phase c is consistent with the falling edge time of the voltage pulse of submodule i2 of phase b; the rising edge time of the voltage pulse of submodule i of phase a is consistent with the falling edge time of the voltage pulse of submodule i of phase c, where i, i1, and i2 are all integers between 1 and N, and i1 and i2 satisfy the following relationship: when i2≤N / 2, i1=i2+N / 2, when i2>N / 2, i1=i2-N / 2”; the sum of the voltage pulses of the upper arm submodules and the sum of the voltage pulses of the lower arm submodules of the three-phase MMC are both constant values.

[0025] To achieve the above objectives, a second aspect of the present invention provides a phase-compensated carrier phase-shift modulation device for suppressing MMC common-mode electromagnetic interference, comprising a bridge arm voltage reference signal generation module, a reference signal correction module considering the numerical rounding rules in phase compensation calculation, a three-phase bridge arm sub-module carrier phase compensation value calculation module, a sub-module carrier signal generation module after phase compensation, and a PWM pulse generation module, executing the method described above, characterized in that it includes:

[0026] The arm voltage reference signal generation module is used to calculate the MMC arm voltage reference signal and the voltage reference signal of each sub-module;

[0027] The reference signal correction module is used to eliminate the error caused by converting the bridge arm voltage reference signal from a floating-point number to an integer during the phase compensation value calculation process.

[0028] The three-phase bridge arm submodule carrier phase compensation value calculation module is used to calculate in real time the time offset value corresponding to the carrier phase compensation phase of the B and C phase submodules when the target of constant MMC common mode voltage is achieved.

[0029] The sub-module carrier signal generation module after phase compensation is used to generate carrier signals for all three-phase sub-modules;

[0030] The PWM pulse generation module is used to generate pulse drive signals for each sub-module of the MMC.

[0031] To achieve the above objectives, a third aspect of the present invention provides a computer device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference as described above.

[0032] To achieve the above objectives, a fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference as described above.

[0033] The phase-compensated carrier phase-shift modulation method and apparatus for suppressing common-mode electromagnetic interference in MMC proposed in this invention solves the technical problem that high-frequency common-mode voltage in existing MMCs generates leakage current and common-mode interference through stray capacitance, which can damage motor bearings, communication systems, etc. By optimizing the submodule switching sequence, the high-frequency jump of common-mode voltage is eliminated in real time, thereby effectively reducing the leakage current and common-mode noise of MMC and improving its working performance. Attached Figure Description

[0034] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0035] Figure 1 The flowchart illustrates a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference provided in this application embodiment.

[0036] Figure 2 This is a schematic diagram of the MMC circuit structure of the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference according to an embodiment of this application.

[0037] Figure 3 This is a schematic diagram of the reference voltage signal, carrier signal, and common-mode voltage waveform of a three-phase upper bridge arm with a typical carrier phase-shift modulation of MMC with 4 bridge arm sub-modules in this application embodiment.

[0038] Figure 4 This is a schematic diagram of the common-mode voltage of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, when modulated according to the typical carrier phase-shift modulation of the MMC.

[0039] Figure 5This is a schematic diagram of the common-mode voltage spectrum of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, when modulated according to the typical carrier phase shift modulation of the MMC.

[0040] Figure 6 This is a schematic diagram of the reference voltage signal, carrier signal, and common-mode voltage waveform of a three-phase upper bridge arm of an MMC with four bridge arm sub-modules after phase compensation, as shown in an embodiment of this application.

[0041] Figure 7 This is a schematic diagram of the common-mode voltage achieved by a bridge arm submodule MMC with 4 submodules in this application under the conditions of bus voltage 4kV, effective load current 19.97A, and modulation ratio 1, according to the phase compensation carrier phase shift modulation of this application.

[0042] Figure 8 This is a schematic diagram of the common-mode voltage spectrum of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, implemented according to the phase-compensated carrier phase-shift modulation of this application.

[0043] Figure 9 This is a schematic diagram of the differential mode voltage spectrum of an MMC with 4 bridge arm submodules in this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, implemented according to the typical carrier phase shift modulation of MMC.

[0044] Figure 10 This is a schematic diagram of the differential mode voltage spectrum of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, implemented according to the phase compensation carrier phase shift modulation of this application.

[0045] Figure 11 This is a schematic diagram of a phase-compensated carrier phase-shift modulation device for suppressing MMC common-mode electromagnetic interference provided in an embodiment of this application. Detailed Implementation

[0046] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0047] The phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference according to embodiments of the present invention is described below with reference to the accompanying drawings.

[0048] Figure 1This is a schematic flowchart of a phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference provided in an embodiment of the present invention.

[0049] like Figure 1 As shown, the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference includes the following steps:

[0050] S101: Under the condition of the same phase first term and phase tolerance of three-phase multi-carrier phase-shift modulation in a modular multilevel converter (MMC), calculate the phase difference between the voltage pulses of the upper arm of the three phases and the phase difference between the voltage pulses of the lower arm of the three phases respectively, and obtain the calculation results; wherein, the three phases include phase A, phase B and phase C;

[0051] S102: Keep the carrier phase of all sub-modules in phase A unchanged, and increase the corresponding compensation value of the carrier phase of each sub-module in phases B and C according to the calculation results to obtain the updated carrier signal of each sub-module of MMC;

[0052] S103: Compare the voltage reference signals of each MMC submodule with the updated carrier signal, generate drive pulses and apply them to each MMC submodule.

[0053] Furthermore, in one embodiment of the present invention, MMC typical carrier phase shift modulation includes:

[0054] When an isosceles triangular carrier with the same amplitude and period is applied to each sub-module of the MMC, the initial phase of the carrier of each sub-module in the upper phase bridge arm is arranged in an arithmetic sequence with the first term being 0 and the tolerance being 2π / N. The initial phase of the carrier of each sub-module in the lower phase bridge arm is arranged in an arithmetic sequence with the first term being π / N and the tolerance being 2π / N.

[0055] The voltage reference signal of each bridge arm is evenly distributed to each sub-module within each bridge arm. The pulse drive signal of each sub-module within each bridge arm is obtained by comparing the per-unit value of the voltage reference signal of each sub-module within each bridge arm with the triangular carrier signal.

[0056] Furthermore, in one embodiment of the present invention, while keeping the carrier phases of all submodules in phase A unchanged, the carrier phases of each submodule in phases B and C are increased by a corresponding compensation value based on the calculation results, including:

[0057] Define the corresponding time offset τ of the in-phase upper arm. pj Let j = a, b, c. Within one control cycle T, make the voltage pulse rising edge time t of the j-phase numbered x submodule so that... prjx Increase carrier time offset τ pj Then, at the falling edge time t of the voltage pulse of the previous phase k-numbered y submodule. pfky Increase carrier time offset τ pkAfter phase coherence, the k values ​​corresponding to j = a, b, c are c, a, b, and m is any integer. The mathematical expression is: t prjx +τ pj =t pfky +τ pk +mT.

[0058] Furthermore, in one embodiment of the present invention, after adding corresponding compensation values ​​to the carrier phases of each submodule of phases B and C according to the calculation results, the voltage pulses of the upper and lower arms of the three-phase MMC all satisfy the following: the rising edge time of the voltage pulse of submodule i in phase b is consistent with the falling edge time of the voltage pulse of submodule i in phase a; the rising edge time of the voltage pulse of submodule i1 in phase c is consistent with the falling edge time of the voltage pulse of submodule i2 in phase b; the rising edge time of the voltage pulse of submodule i in phase a is consistent with the falling edge time of the voltage pulse of submodule i in phase c, where i, i1, and i2 are all integers between 1 and N, and i1 and i2 satisfy the following relationship: when i2≤N / 2, i1=i2+N / 2, when i2>N / 2, i1=i2-N / 2”; the sum of the voltage pulses of the upper arm submodules and the sum of the voltage pulses of the lower arm submodules of the three-phase MMC are both constant values.

[0059] Figure 2 This is a schematic diagram of the MMC circuit structure of the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference according to an embodiment of this application.

[0060] like Figure 2 As shown, the MMC contains three phase units, each of which includes two bridge arms, referred to as the upper bridge arm and the lower bridge arm, respectively. Each bridge arm contains N sub-modules and one bridge arm inductor L, where N is usually an even number. The DC side is connected to a DC voltage source, and the AC side is connected to a three-phase AC power grid or a three-phase AC load.

[0061] Figure 3 This is a schematic diagram of the reference voltage signal, carrier signal, and common-mode voltage waveform of a typical three-phase upper bridge arm with MMC carrier phase-shift modulation and four bridge arm sub-modules in this application embodiment, used to calculate the phase difference of the three-phase bridge arm voltage pulses.

[0062] like Figure 3 As shown, u pj * The voltage reference signal per unit value is based on the ratio of DC voltage to the number of submodules in a single bridge arm, c. pji This is a carrier signal, where the carrier value is between 0 and 1, u pj U is the output bridge arm voltage. C The capacitor voltage is shown as a constant value in the schematic diagram. pCMLet be the common-mode voltage of the three-phase upper arm, where j = a, b, c, i = 1, 2, ..., N, and N is the number of submodules in a single arm.

[0063] MMC common-mode voltage u CM It can be calculated using the following formula, where u j Let j be the phase AC voltage, where j = a, b, c.

[0064]

[0065] MMC common-mode voltage u CM The relationship between the common-mode voltage of the three-phase upper arm and the three-phase lower arm satisfies the following formula.

[0066]

[0067] In MMC phase-compensated carrier phase-shift modulation, the following three characteristics are present:

[0068] 1) Each submodule uses an isosceles triangular carrier with the same amplitude and period. The initial phase of the carrier of each submodule in the upper phase bridge arm is arranged in an arithmetic sequence with the first term being 0 and the tolerance being 2π / N. The initial phase of the carrier of each submodule in the lower phase bridge arm is also arranged in an arithmetic sequence with the first term being π / N and the tolerance being 2π / N.

[0069] 2) The voltage reference signal of each bridge arm is evenly distributed to each sub-module within that bridge arm and compared with the corresponding carrier wave to obtain the pulse drive signal of each sub-module;

[0070] 3) The sum of the three-phase upper bridge arm voltages exhibits high-frequency fluctuations, with the fluctuation limit being ±U. C / 3, the pulse frequency is close to 3N times the carrier frequency.

[0071] Figure 4 This is a schematic diagram of the common-mode voltage of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, when modulated according to the typical carrier phase-shift modulation of the MMC.

[0072] Figure 5 This is a schematic diagram of the common-mode voltage spectrum of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, when modulated according to the typical carrier phase shift modulation of the MMC.

[0073] The MMC contains a high-frequency common-mode voltage that jumps frequently. When using phase-compensated carrier phase-shift modulation, the amplitude of each jump in the MMC common-mode voltage is 1 / 6 of the submodule capacitor voltage, and the jumping frequency is 6N times the carrier frequency. With a carrier frequency of 5kHz, 4 submodules per bridge arm, and 8 submodules per phase, the peak value of the common-mode voltage is located at 40kHz, corresponding to 8 times the carrier frequency, with an amplitude of 151.77dBμV.

[0074] Figure 6 This is a schematic diagram of the reference voltage signal, carrier signal, and common-mode voltage waveform of a three-phase upper bridge arm of an MMC with four bridge arm sub-modules after phase compensation, as shown in an embodiment of this application.

[0075] like Figure 6 As shown, keeping the carrier phases of all submodules in phase A of the MMC unchanged, the carrier phases of each submodule in phases B and C are increased by the corresponding compensation value based on the calculation results. Taking the upper arm of the MMC as an example, the carrier phase compensation value of each submodule in the same phase upper arm is the same, corresponding to a time offset τ. pj j = a, b, c. Within a single control cycle, the integer number of phase shifts of the triangular carrier wave do not affect the rise and fall times of the submodule pulse. Phase compensation between the three phases can keep the MMC common-mode voltage constant, ensuring that the rise time t of the voltage pulse of submodule x in phase j is within one control cycle T. prjx Increase carrier time offset τ pj Then, the falling edge time t of the voltage pulse of the previous phase (k phase) numbered submodule y pfky Increase carrier time offset τ pk After phase coherence, the k values ​​corresponding to j = a, b, c are c, a, b, and m is any integer. The mathematical expression is as follows:

[0076] t prjx +τ pj =t pfky +τ pk +mT

[0077] The voltage reference signals of each MMC submodule are compared with the updated carrier signal to generate drive pulses, which are then applied to the submodules. The submodule drive pulses with added phase compensation have the following characteristics:

[0078] The voltage pulses of the upper and lower arms of the three-phase MMC all satisfy the following: 1) The rising edge of the voltage pulse of submodule i in phase b is consistent with the falling edge of the voltage pulse of submodule i in phase a; 2) The rising edge of the voltage pulse of submodule i1 in phase c is consistent with the falling edge of the voltage pulse of submodule i2 in phase b. When i2≤N / 2, i1=i2+N / 2, and when i2>N / 2, i1=i2-N / 2; 3) The rising edge of the voltage pulse of submodule i in phase a is consistent with the falling edge of the voltage pulse of submodule i in phase c, where i, i1, and i2 are all integers between 1 and N.

[0079] The sum of voltage pulses in both the upper and lower bridge arm submodules of the MMC is a constant value, thus suppressing common-mode electromagnetic interference (EMC). If dead-time and capacitor voltage fluctuations are ignored, the MMC common-mode voltage fluctuation is theoretically reduced to zero. Compared to typical phase-compensated carrier phase-shift modulation in MMC, the pulse width of each submodule in the phase-compensated carrier phase-shift modulation method remains unchanged, thus not reducing the DC voltage utilization rate of the MMC.

[0080] Figure 7 This is a schematic diagram of the common-mode voltage achieved by a bridge arm submodule MMC with 4 submodules in this application under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, according to the phase compensation carrier phase shift modulation of this application.

[0081] Figure 8 This is a schematic diagram of the common-mode voltage spectrum of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, implemented according to the phase-compensated carrier phase-shift modulation of this application.

[0082] Figure 5 , Figure 7 The common-mode voltage time-domain waveforms before and after implementing the phase compensation method according to this application are shown below. Figure 5 , Figure 7 As shown, after implementing the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference in this application, the MMC common-mode voltage fluctuation is reduced to near zero, thereby reducing the high-frequency common-mode voltage of the MMC from the source.

[0083] Figure 6 , Figure 8 The common-mode voltage spectrum before and after implementing the phase compensation method according to this application is shown below. Figure 6 , Figure 8 As shown, after implementing the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference in this application, the peak value of the MMC common-mode voltage spectrum in the region above 1kHz is reduced by approximately 41.2dBμV.

[0084] Figure 9 This is a schematic diagram of the differential mode voltage spectrum of an MMC with 4 bridge arm submodules in this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, implemented according to the typical carrier phase shift modulation of MMC.

[0085] Figure 10 This is a schematic diagram of the differential mode voltage spectrum of an MMC with 4 bridge arm submodules according to an embodiment of this application, under the conditions of bus voltage 4kV, effective value of load current 19.97A, and modulation ratio 1, implemented according to the phase compensation carrier phase shift modulation of this application.

[0086] Figure 9 , Figure 10 The differential-mode voltage spectrum waveforms before and after implementing the phase compensation method according to this application are shown below. Figure 9 , Figure 10 As shown, after implementing the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference in this application, the differential-mode voltage is reduced by about 0.01dB in the 50Hz spectral component, which is 99.88% of the original amplitude, with an error of less than 0.1%. Theoretically, the DC voltage utilization rate is not reduced. The MMC differential-mode voltage is defined as the difference between the A-phase output voltage and the B-phase output voltage.

[0087] Figure 11 This is a schematic diagram of a phase-compensated carrier phase-shift modulation device for suppressing MMC common-mode electromagnetic interference provided in an embodiment of this application.

[0088] like Figure 11 As shown, the device includes a three-phase bridge arm voltage reference signal generation module 20, a reference signal correction module 21 considering the numerical rounding rules in the phase compensation calculation, a three-phase bridge arm sub-module carrier phase compensation value calculation module 22, a sub-module carrier signal generation module 23 after phase compensation, and a PWM pulse generation module 24, wherein...

[0089] The bridge arm voltage reference signal generation module is used to calculate the MMC bridge arm voltage reference signal and the voltage reference signal of each sub-module;

[0090] A reference signal correction module considering the rounding rules in phase compensation calculation is used to eliminate the error caused by converting the bridge arm voltage reference signal from a floating-point number to an integer during the phase compensation value calculation process.

[0091] The three-phase bridge arm submodule carrier phase compensation value calculation module is used to calculate in real time the time offset value corresponding to the carrier phase compensation phase of the B and C phase submodules when the target of constant MMC common mode voltage is achieved.

[0092] The sub-module carrier signal generation module after phase compensation is used to generate carrier signals for all three-phase sub-modules;

[0093] The PWM pulse generator module is used to generate pulse drive signals for each sub-module of the MMC.

[0094] The phase-compensated carrier phase-shift modulation method and apparatus for suppressing common-mode electromagnetic interference in MMC proposed in this invention solves the technical problem that high-frequency common-mode voltage in existing MMCs generates leakage current and common-mode interference through stray capacitance, which can damage motor bearings, communication systems, etc. By optimizing the submodule switching sequence, the high-frequency jump of common-mode voltage is eliminated in real time, thereby effectively reducing the leakage current and common-mode noise of MMC and improving its working performance.

[0095] To achieve the above objectives, a third aspect of the present invention provides a computer device, characterized in that it includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference as described above.

[0096] To achieve the above objectives, a fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, characterized in that, when the computer program is executed by a processor, it implements the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference as described above.

[0097] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0098] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0099] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference, characterized in that, Includes the following steps: Under the condition of the same phase first term and phase tolerance of three-phase multi-carrier phase-shift modulation in a modular multilevel converter (MMC), the phase difference between the voltage pulses of the upper arm of the three phases and the phase difference between the voltage pulses of the lower arm of the three phases are calculated respectively, and the calculation results are obtained; wherein, the three phases include phase A, phase B and phase C; Keeping the carrier phases of all submodules in phase A unchanged, the carrier phases of each submodule in phases B and C are increased by corresponding compensation values ​​according to the calculation results, so as to obtain the updated carrier signals of each submodule of MMC; The voltage reference signals of each MMC submodule are compared with the updated carrier signal to generate drive pulses and apply them to each MMC submodule. The step of keeping the carrier phases of all submodules in phase A unchanged, and increasing the carrier phases of each submodule in phases B and C by a corresponding compensation value based on the calculation results, includes: Define the corresponding time offset of the in-phase upper arm. τ pj , j =a, b, c, in one control cycle T Inside, make j Phase number x Submodule voltage pulse rising edge time t prjx Increase carrier time offset τ pj Afterwards, with the previous phase k serial number y Submodule voltage pulse falling edge time t pfky Increase carrier time offset τ pk After phase consistency, j =a, b, c corresponding to k The values ​​are c, a, b. m For any integer, the mathematical expression is: .

2. The method according to claim 1, characterized in that, The typical carrier phase-shift modulation of MMC includes: When an isosceles triangular carrier wave of the same amplitude and period is applied to each submodule of the MMC, the initial phase of the carrier wave of each submodule in the in-phase upper bridge arm is arranged in an arithmetic sequence, with the first term being 0 and the common difference being 2π / N In the in-phase bridge arm, the initial carrier phases of each submodule are arranged in an arithmetic sequence, with the first term being π / N The tolerance is 2π / N ; The voltage reference signal of each bridge arm is evenly distributed to each sub-module within each bridge arm. The pulse drive signal of each sub-module within each bridge arm is obtained by comparing the per-unit value of the voltage reference signal of each sub-module within each bridge arm with the triangular carrier signal.

3. The method according to claim 1, characterized in that, After adding corresponding compensation values ​​to the carrier phases of each submodule in phases B and C based on the calculation results, the voltage pulses of the upper and lower arms of the three-phase MMC all satisfy: phase b number i The rising edge time of the voltage pulse of the submodule is related to the phase number of phase a. i The voltage pulse falling edges of the submodules are synchronized; phase c numbering i The voltage pulse rising edge time of submodule 1 is related to phase b number. i The voltage pulse falling edges of the two submodules are consistent; phase a is numbered. i The rising edge time of the voltage pulse of the submodule is related to the c-phase number. i The voltage pulse falling edges of the submodules are consistent, where i , i 1, i Both 2 are between 1 and N Integers between and i 1 and i 2 satisfies the following relationship: when i 2 ≤ N / 2 o'clock, i 1 = i 2+ N / 2, when i 2 > N / 2 o'clock, i 1 = i 2 N / 2”; The sum of voltage pulses of the MMC three-phase upper arm submodule and the sum of voltage pulses of the lower arm submodule are both constant values.

4. A phase-compensated carrier phase-shift modulation device for suppressing MMC common-mode electromagnetic interference, comprising a bridge arm voltage reference signal generation module, a reference signal correction module considering the numerical rounding rules in phase compensation calculation, a three-phase bridge arm sub-module carrier phase compensation value calculation module, a sub-module carrier signal generation module after phase compensation, and a PWM pulse generation module, performing the method as described in claim 1, characterized in that, include: The arm voltage reference signal generation module is used to calculate the MMC arm voltage reference signal and the voltage reference signal of each sub-module; The reference signal correction module that considers the numerical rounding rules in the phase compensation calculation is used to eliminate the error caused by the conversion of the bridge arm voltage reference signal from floating point to integer during the phase compensation value calculation process. The three-phase bridge arm submodule carrier phase compensation value calculation module is used to calculate in real time the time offset value corresponding to the carrier phase compensation phase of the B and C phase submodules when the target of constant MMC common mode voltage is achieved. The sub-module carrier signal generation module after phase compensation is used to generate carrier signals for all three-phase sub-modules; The PWM pulse generation module is used to generate pulse drive signals for each sub-module of the MMC.

5. A computer device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference as described in any one of claims 1-3.

6. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the phase-compensated carrier phase-shift modulation method for suppressing MMC common-mode electromagnetic interference as described in any one of claims 1-3.

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