Magnetic bias elimination and overload prevention and control fusion method independent of flux linkage observation

Abstract

The invention provides a magnetic bias elimination and overload prevention and control fusion method independent of flux linkage observation, and relates to the technical field of power transmission and distribution converter control. The method comprises the following steps: S1, excitation current calculation: measuring primary side and secondary side currents of a transformer, and calculating the excitation current of the transformer; s2, direct-current component extraction and per-unit value calculation: extracting the direct-current component of the exciting current, and calculating the per-unit value of the direct-current component; s3, bias elimination enabling: outputting a bias elimination enabling signal according to the per unit value of the direct-current component of the exciting current and the criterion; s4, current transformer overload threshold value calculation: calculating the current transformer overload threshold value according to the current transformer operation point; and S5, magnetic bias elimination execution: inputting a magnetic bias eliminator and a current inner ring matching controller according to the magnetic bias elimination enable signal, and actively eliminating the magnetic bias of the transformer. According to the method, the functions of magnetic bias elimination and overload prevention and control are integrated, the functions of the converter are efficiently multiplexed, a complex flux linkage observation algorithm and extra hardware equipment investment are not needed, and the method is easy to implement and good in economical efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of power transmission and distribution converter control, and in particular to a method for integrating magnetic bias elimination and overload prevention and control that does not rely on flux linkage observation. Background Art

[0002] Transformers are core devices for achieving AC voltage conversion and electrical isolation and are widely used in converter grid-connected systems. When a grid disturbance occurs or the transformer is started up at no-load, the DC bias of the busbar voltage can cause transformer bias, leading to voltage distortion at the transformer port and harmonic current output. This degrades the converter's output waveform quality and can even cause overvoltage and overcurrent faults. Traditional methods for eliminating transformer bias require the additional configuration of costly demagnetization equipment. Using converters to actively suppress transformer bias allows for efficient reuse of converter functions, which is crucial for improving the anti-interference operation capability and output waveform quality of converter grid-connected systems.

[0003] Chinese patent CN112202179A discloses a flux control method for suppressing magnetic saturation in a series transformer connected to a voltage compensator. This method constructs a state-space equation to observe and control the flux of the series transformer. However, this flux observation method assumes a linear relationship between transformer voltage and flux, requiring high precision in model parameters and resulting in a complex controller structure and computation. Actual transformers have nonlinear characteristics, and circuit parameter estimation can be biased. The effectiveness of this method in practical applications requires further verification.

[0004] Chinese patent CN119651492A discloses a method and device for suppressing flux saturation in a flexible DC converter transformer. This method estimates the transformer flux by measuring the transformer port voltage and current and using an integration algorithm, and then performs feedback suppression on the DC bias of the flux. However, this method requires multiple voltage and current sensors, as well as the transformer's leakage resistance, leakage reactance, and residual magnetism. Due to parameter estimation bias and cumulative integration errors, this method generates flux estimation errors, limiting its practical application.

[0005] In summary, the current method of using the converter to actively suppress transformer bias relies on a high-precision flux observation algorithm, which has high requirements for sensor configuration, model parameter accuracy and control algorithm. It does not consider the converter overload problem during the bias suppression process, which can easily cause converter overvoltage and overcurrent faults, making it difficult to meet the anti-disturbance operation requirements of the converter grid-connected system. Summary of the Invention

[0006] The purpose of the present invention is to propose a fusion method of bias magnetic elimination and overload prevention and control that does not rely on flux linkage observation to solve the problems raised in the background technology.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The integrated method of magnetic bias elimination and overload prevention and control that does not rely on magnetic flux observation includes the following:

[0009] S1. Excitation current calculation: measure the primary and secondary currents of the transformer and calculate the transformer excitation current;

[0010] S2. DC component extraction and per-unit value calculation: extract the DC component of the excitation current and calculate its per-unit value;

[0011] S3, bias magnetic elimination enable: output bias magnetic elimination enable signal according to the per-unit value of the DC component of the excitation current and the judgment criteria;

[0012] S4. Converter overload threshold calculation: Calculate the converter overload threshold according to the converter operating point;

[0013] S5, bias elimination execution: according to the bias elimination enable signal, the bias elimination device and the current inner loop matching controller are activated to actively eliminate the bias of the transformer.

[0014] Preferably, the excitation current in S1 is denoted as i f =[i fA ,i fB ,i fC ] T , T is the matrix transpose operator, and its calculation formula is:

[0015]

[0016] Where i 1A 、i 1B 、i 1C Indicates the measured three-phase current of the primary side of the transformer, and the current flowing into the transformer is in the positive direction; i 2A 、i 2B 、i 2C , represents the measured three-phase current on the secondary side of the transformer, with the current flowing out of the transformer in the positive direction; k is the transformer primary-to-secondary voltage ratio.

[0017] Preferably, S2 specifically includes the following contents:

[0018] Use the filter to extract the excitation current i f The DC component in the excitation current is obtained as fdc , denoted as i fdc =[i fAdc ,i fBdc ,i fCdc ] T , calculate the per-unit value of the DC component of the excitation current i fdc_pu , denoted as i fdc_pu =[i fAdc_pu ,i fBdc_pu ,i fCdc_pu ]T , the calculation formula is:

[0019]

[0020] Where U B is the transformer primary line voltage reference value; S B is the transformer capacity.

[0021] Preferably, the S3 specifically includes the following contents: the excitation current criterion is:

[0022] J:|i fAdc_pu |>d or |i fBdc_pu |>d or |i fCdc_pu |>d

[0023] Where i fAdc_pu 、i fBdc_pu 、i fCdc_pu is the per-unit value of the DC component of the excitation current obtained in S2; d is the judgment threshold.

[0024] When the criterion J is true, the bias magnetization elimination enable signal is assigned a value of 1; when the criterion J is false, the bias magnetization elimination enable signal is assigned a value of 0.

[0025] Preferably, the converter overload threshold in S4 is denoted as I limit , the calculation formula is as follows:

[0026] I limit =I max -II reserve

[0027] Where, I max is the maximum current allowed to flow through the converter bridge arm; I is the peak current of the bridge arm calculated according to the converter operating point; I reserve is the margin.

[0028] Preferably, the bias magnetization elimination in S5 includes the following steps:

[0029] S5.1, bias magnetic negative feedback controller output i fref , denoted as i fref =[i fAref ,i fBref ,i fCref ] T If the enable signal is 1, the bias magnetic negative feedback controller performs negative feedback control on the per-unit value of the DC component of the excitation current and outputs a current adjustment reference value; if the enable signal is 0, the bias magnetic negative feedback controller outputs 0; the calculation formula is as follows:

[0030]

[0031] Where ifAdc_pu 、i fBdc_pu 、i fCdc_pu is the per-unit value of the DC component of the excitation current obtained in S2; G(s) is the frequency domain transfer function of the bias magnetic negative feedback controller, and s is the Laplace operator.

[0032] S5.2, according to the overload threshold I obtained in S4 limit The output i of the bias magnetic negative feedback controller obtained in S5.1 is fref Limit the current to obtain the current reference value increment Δi ref , denoted as Δi ref =[Δi Aref ,Δi Bref ,Δi Cref ] T , the calculation formula is as follows:

[0033]

[0034]

[0035] Where i fAref 、i fBref 、i fCref is the output of the bias magnetic negative feedback controller obtained in S5.1; I limit is the converter overload threshold obtained in S4.

[0036] S5.3. Increment Δi of the current reference value obtained in S5.2 ref Perform ABC / dq transformation to obtain the dq axis current reference value increment Δi dqref , denoted as Δi dqref =[Δi dref ,Δi qref ] T , the calculation formula is as follows:

[0037]

[0038] Where θ g is the synchronous phase angle of the transformer secondary voltage v2.

[0039] S5.4. The current inner loop matching controller is connected in parallel with the original controller to output the dq axis voltage reference value increment Δe dqref , denoted as Δe dqref =[Δe dref ,Δe qref ] T If the enable signal is 1, the matching controller enables the control function and outputs the dq axis voltage reference value increment; if the enable signal is 0, the matching controller outputs 0; the calculation formula is as follows:

[0040]

[0041] Where H(s) is the frequency domain transfer function of the matching controller, s is the Laplace operator; i dref0 、i qref0 is the initial reference value of the dq axis current; Δi dref , Δi qref is the increment of the dq axis current reference value obtained in 5.3; i 2d 、i 2q is the dq axis current measurement value, and the calculation formula is as follows:

[0042]

[0043] Where θ g is the synchronous phase angle of the transformer secondary voltage v2, i 2A 、i 2B 、i 2C is the three-phase current of the secondary side of the transformer obtained in S1.

[0044] S5.5. Increment Δe of the dq axis voltage reference value obtained in S5.4 dqref , and the initial reference value of dq axis voltage e dqref0 , denoted as e dqref0 =[e dref0 ,e qref0 ] T , calculate the dq axis voltage reference value e dqref , denoted as e dqref =[e dref ,e qref ] T , and for e dqref Perform dq / ABC transformation to obtain the converter three-phase voltage reference value e ref , denoted as e ref =[e Aref ,e Bref ,e Cref ] T , the calculation formula is as follows:

[0045]

[0046] Where θ g is the synchronous phase angle of the transformer secondary voltage v2.

[0047] Compared with the existing technology, the present invention provides a method for integrating magnetic bias elimination and overload prevention and control that does not rely on flux linkage observation, and has the following beneficial effects:

[0048] (1) The present invention uses the converter to actively eliminate the transformer bias magnetism and adopts the transformer excitation current as the feedback signal. It does not rely on a high-precision flux observation algorithm and can avoid the problem of bias elimination failure caused by model parameter deviation and flux observation algorithm error.

[0049] (2) The present invention takes into account the converter overload problem during the demagnetization process. By calculating the converter overload threshold and implementing the overload limiter, the converter can be prevented from overvoltage and overcurrent failures during the demagnetization process.

[0050] (3) The present invention has the ability to automatically identify and eliminate bias magnetism. When the excitation current criterion is true, the bias magnetism negative feedback controller and the current inner loop matching controller are automatically enabled, which can improve the bias magnetism elimination response speed;

[0051] (4) The present invention integrates the functions of bias magnetic elimination and overload prevention and control, realizes efficient reuse of converter functions, does not require additional hardware equipment investment, and has good economic efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 This is a block diagram of the bias magnetic elimination and overload prevention and control fusion system proposed in Example 1 of the present invention;

[0053] Figure 2 This is a control block diagram of the bias magnetic eliminator proposed in Example 1 of the present invention;

[0054] Figure 3 This is a block diagram of the current inner loop control proposed in Example 1 of the present invention;

[0055] Figure 4 This is a diagram showing the DC component of the transformer magnetic flux when the method proposed by the present invention is not adopted in Example 1 of the present invention;

[0056] Figure 5 This is a diagram showing the effect of the DC component of the transformer magnetic flux when the method proposed by the present invention is adopted in Example 1 of the present invention. DETAILED DESCRIPTION

[0057] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0058] Example 1:

[0059] See also Figure 1 The block diagram of the integrated system for bias magnetic elimination and overload prevention and control is as follows: Figure 1 As shown, based on Figure 1 The present invention proposes a method for integrating magnetic bias elimination and overload prevention and control that does not rely on flux linkage observation, which specifically includes the following contents:

[0060] S1: Excitation current calculation link:

[0061] Link S1 measures the transformer primary current i1, which is recorded as i1 = [i 1A ,i 1B ,i 1C ] T , T is the matrix transpose operator; measure the secondary current i2 of the transformer, record it as i2=[i 2A ,i 2B ,i 2C ] T ; Calculate the transformer excitation current i f , denoted as i f =[i fA ,i fB ,i fC ] T Taking a YY connected transformer as an example, the excitation current calculation formula is:

[0062]

[0063] Where i 1A 、i 1B 、i 1C Indicates the measured three-phase current of the primary side of the transformer, and the current flowing into the transformer is in the positive direction; i 2A 、i 2B 、i 2C , represents the measured three-phase current on the secondary side of the transformer, with the current flowing out of the transformer in the positive direction; k is the transformer primary-to-secondary voltage ratio.

[0064] S2: DC component extraction and per-unit value calculation:

[0065] Link S2 is for the excitation current i obtained in S1 f , extract the DC component of the excitation current i fdc , and calculate its per-unit value i fdc_pu Extracting the DC component of the excitation current can be accomplished through a filter. For example, the DC component of the three-phase excitation current can be extracted by connecting a band-stop filter and a low-pass filter in series. The transfer function LPF(s) of the low-pass filter is:

[0066]

[0067] ω c1 =2πf c1

[0068] Where ζ is the damping coefficient; π is the circumference of a circle; f c1 is the cutoff frequency of the low-pass filter; s is the Laplace operator. Generally, ζ can be taken as 0.707, and f c1 is 10Hz. The band-stop filter transfer function BSF(s) is:

[0069]

[0070] ω c2 =2πf c2

[0071] B=2πf b

[0072] Where, f c2 For the cutoff frequency of the band-stop filter, take f c2 is 50Hz; B=2πf b , f b is the bandwidth frequency, which can generally be taken as f b The frequency range is 5 to 15 Hz. f The DC component in the excitation current is extracted and filtered, and the DC component of the excitation current is recorded as i fdc =[i fAdc ,i fBdc ,i fCdc ] T .

[0073] Calculate the per-unit value i of the DC component of the excitation current fdc_pu , denoted as i fdc_pu =[i fAdc_pu ,i fBdc_pu ,i fCdc_pu ] T , the calculation formula is:

[0074]

[0075] Where U B is the transformer primary line voltage reference value; S B is the transformer capacity.

[0076] S3: Bias magnetic elimination enabling link:

[0077] Link S3 outputs the bias magnetization elimination enable signal based on the per-unit value of the DC component of the excitation current and the criterion. The excitation current criterion is:

[0078] J:|i fAdc_pu |>d or |i fBdc_pu |>d or |i fCdc_pu |>d

[0079] Where i fAdc_pu 、i fBdc_pu 、i fCdc_pu is the per-unit value of the DC component of the excitation current obtained in S2; d is the judgment threshold, which needs to be adjusted according to the actual transformer equipment.

[0080] When the criterion J is true, the bias magnetization elimination enable signal is assigned a value of 1; when the criterion J is false, the bias magnetization elimination enable signal is assigned a value of 0.

[0081] S4: Converter overload threshold calculation step:

[0082] Step S4 calculates the converter overload threshold value according to the converter operating point, which is denoted as I limit If the converter is a modular multilevel converter (MMC), the calculation formula is as follows:

[0083] I limit =I max -II reserve

[0084] Where, I max is the maximum current allowed to flow through the MMC bridge arm, I is the peak current of the bridge arm calculated according to the MMC operating point; I reserve It is the margin, which should be selected reasonably according to the actual situation, and generally 10% I max The calculation formula of I is as follows:

[0085]

[0086] Where, P ref is the MMC active power reference value, Q ref is the MMC reactive power reference value, U m is the peak value of the MMC AC phase voltage, U dc is the MMC DC voltage.

[0087] S5: Bias elimination execution link.

[0088] Section S5 includes the following:

[0089] S5.1. Please refer to Figure 2 , the control block diagram of the bias magnetic eliminator is as follows Figure 2 Based on Figure 2 , the bias magnetic negative feedback controller output i fref , denoted as i fref =[i fAref ,i fBref ,i fCref ] T If the enable signal is 1, the bias magnetic negative feedback controller will set the DC component of the excitation current to the unit value i fdc_pu Perform negative feedback control and output current adjustment reference value; if the enable signal is 0, the bias magnetic negative feedback controller outputs 0; the calculation formula is as follows:

[0090]

[0091] Where i fAdc_pu 、i fBdc_pu 、i fCdc_pu is the per-unit value of the DC component of the excitation current obtained in S2; G(s) is the frequency domain transfer function of the bias magnetic negative feedback controller, s is the Laplace operator; K p is the proportional coefficient of G(s); K i is the integral coefficient of G(s).

[0092] S5.2, according to the overload threshold I obtained in S4 limit For i obtained in S5.1 fref Limit the current to obtain the current reference value increment Δi ref , denoted as Δi ref =[Δi Aref ,Δi Bref ,Δi Cref ] T , the calculation formula is as follows:

[0093]

[0094] Where i fAref 、i fBref 、i fCref is the output of the bias magnetic negative feedback controller obtained in S5.1; I limit is the converter overload threshold obtained in S4.

[0095] S5.3. Increment Δi of the current reference value obtained in S5.2 ref Perform ABC / dq transformation to obtain the dq axis current reference value increment Δi dqref , denoted as Δi dqref =[Δi dref ,Δi qref ] T , the calculation formula is as follows:

[0096]

[0097] Where θ g is the synchronous phase angle of the transformer secondary voltage v2.

[0098] S5.4, see Figure 3 , the current inner loop control block diagram is as follows Figure 3 Based on Figure 3 The current inner loop matching controller H(s) is connected in parallel with the original controller to output the dq axis voltage reference value increment Δe dqref , denoted as Δe dqref =[Δe dref ,Δe qref ] TIf the enable signal is 1, the matching controller enables the control function and outputs the dq axis voltage reference value increment; if the enable signal is 0, the matching controller outputs 0; the calculation formula is as follows:

[0099]

[0100] Where H(s) is the frequency domain transfer function of the matching controller, s is the Laplace operator, and K r is the gain coefficient, ω1 is the resonant frequency, ω1=100π; i dref0 、i qref0 is the initial reference value of the dq axis current, which is determined by the initial operating point; Δi dref , Δi qref is the increment of the dq axis current reference value obtained in 5.3; i 2d 、i 2q is the dq axis current measurement value, and the calculation formula is as follows:

[0101]

[0102] Where θ g is the synchronous phase angle of the transformer secondary voltage v2, i 2A 、i 2B 、i 2C is the three-phase current of the secondary side of the transformer obtained in S1.

[0103] S5.5. Increment Δe of the dq axis voltage reference value obtained in S5.4 dqref , and the initial reference value of dq axis voltage e dqref0 , denoted as e dqref0 =[e dref0 ,e qref0 ] T , calculate the dq axis voltage reference value e dqref , denoted as e dqref =[e dref ,e qref ] T , and for e dqref Perform dq / ABC transformation to obtain the converter three-phase voltage reference value e ref , denoted as e ref =[e Aref ,e Bref ,e Cref ] T , the calculation formula is as follows:

[0104]

[0105] Where θ g is the synchronous phase angle of the transformer secondary voltage v2.

[0106] See also Figure 4 The effect diagram of the DC component of the transformer flux when the method proposed by the present invention is not adopted is as follows: Figure 4 As shown. Figure 4 It can be seen that after the transformer is biased, when the method proposed in the present invention is not adopted, the DC component of the transformer magnetic flux is not zero and decays slowly.

[0107] See also Figure 5 The effect diagram of the DC component of the transformer flux when the method proposed by the present invention is adopted is as follows: Figure 5 As shown. Figure 5 It can be seen that after the transformer is magnetized, the DC component of the transformer flux is quickly eliminated when the proposed method is used.

[0108] It should be noted that the contents not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

[0109] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the present invention, and should not be regarded as an admission or any form of implication that the information constitutes prior art already known to those skilled in the art.

Claims

1. A method for integrating magnetic bias elimination and overload prevention and control that does not rely on flux linkage observation, characterized in that: Includes the following: S1. Excitation current calculation: measure the primary and secondary currents of the transformer and calculate the transformer excitation current; S2. DC component extraction and per-unit value calculation: extract the DC component of the excitation current and calculate its per-unit value; S3, bias magnetic elimination enable: output bias magnetic elimination enable signal according to the per-unit value of the DC component of the excitation current and the judgment criteria; S4. Converter overload threshold calculation: Calculate the converter overload threshold according to the converter operating point; S5, bias elimination execution: according to the bias elimination enable signal, the bias elimination device and the current inner loop matching controller are activated to actively eliminate the bias of the transformer.

2. The method according to claim 1, wherein The excitation current in S1 is denoted as i f =[i fA ,i fB ,i fC ] T , T is the matrix transpose operator, and its calculation formula is: Where i 1A 、i 1B 、i 1C Indicates the measured three-phase current of the primary side of the transformer, and the current flowing into the transformer is in the positive direction; i 2A 、i 2B 、i 2C It represents the measured three-phase current on the secondary side of the transformer, with the current flowing out of the transformer in the positive direction; k is the transformer primary-to-secondary voltage ratio.

3. The method according to claim 2, characterized in that The S2 specifically includes the following contents: Use the filter to extract the excitation current i f The DC component in the excitation current is obtained as fdc , denoted as i fdc =[i fAdc ,i fBdc ,i fCdc ] T , calculate the per-unit value of the DC component of the excitation current i fdc_pu , denoted as i fdc_pu =[i fAdc_pu ,i fBdc_pu ,i fCdc_pu ] T , the calculation formula is: Where U B is the transformer primary line voltage reference value; S B is the transformer capacity.

4. The method according to claim 3, wherein The excitation current criterion in S3 is: J:|i fAdc_pu |>d or |i fBdc_pu |>d or |i fCdc_pu |>d Where i fAdc_pu 、i fBdc_pu 、i fCdc_pu is the per-unit value of the DC component of the excitation current obtained in S2; d is the judgment threshold; When the criterion J is true, the bias magnetization elimination enable signal is assigned a value of 1; when the criterion J is false, the bias magnetization elimination enable signal is assigned a value of 0.

5. The method according to claim 4, characterized in that The converter overload threshold in S4 is denoted as I limit , the calculation formula is as follows: I limit =I max -I-I reserve Where, I max is the maximum current allowed to flow through the converter bridge arm; I is the peak current of the bridge arm calculated according to the converter operating point; I reserve is the margin.

6. The method according to claim 5, characterized in that The execution of the bias magnetization elimination in S5 includes the following: S5.1, bias magnetic negative feedback controller output i fref , denoted as i fref =[i fAref ,i fBref ,i fCref ] T If the enable signal is 1, the bias magnetic negative feedback controller performs negative feedback control on the per-unit value of the DC component of the excitation current and outputs a current adjustment reference value. If the enable signal is 0, the bias magnetic negative feedback controller outputs 0. The calculation formula is as follows: Where i fAdc_pu 、i fBdc_pu 、i fCdc_pu is the per-unit value of the DC component of the excitation current; G(s) is the frequency domain transfer function of the bias magnetic negative feedback controller, and s is the Laplace operator; S5.2, according to the overload threshold I limit The output of the bias magnetic negative feedback controller i fref Limit the current to obtain the current reference value increment Δi ref , denoted as Δi ref =[Δi Aref ,Δi Bref ,Δi Cref ] T , the calculation formula is as follows: Where i fAref 、i fBref 、i fCref is the output of the bias magnetic negative feedback controller; I limit is the converter overload threshold; S5.

3. Increment Δi of the current reference value obtained in S5.2 ref Perform ABC / dq transformation to obtain the dq axis current reference value increment Δi dqref , denoted as Δi dqref =[Δi dref ,Δi qref ] T , the calculation formula is as follows: Where θ g is the synchronous phase angle of the transformer secondary voltage v2; S5.

4. The current inner loop matching controller is connected in parallel with the original controller to output the dq axis voltage reference value increment Δe dqref , denoted as Δe dqref =[Δe dref ,Δe qref ] T If the enable signal is 1, the matching controller enables the control function and outputs the dq axis voltage reference value increment; if the enable signal is 0, the matching controller outputs 0; the calculation formula is as follows: Where H(s) is the frequency domain transfer function of the matching controller, s is the Laplace operator; i dref0 、i qref0 is the initial reference value of dq axis current; Δi dref , Δi qref is the dq axis current reference value increment; i 2d 、i 2q is the dq axis current measurement value, and the calculation formula is as follows: Where θ g is the synchronous phase angle of the transformer secondary voltage v2, i 2A 、i 2B 、i 2C is the three-phase current of the secondary side of the transformer obtained in S1; S5.

5. Increment Δe of the dq axis voltage reference value obtained in S5.4 dqref , and the initial reference value of dq axis voltage e dqref0 , denoted as e dqref0 =[e dref0 ,e qref0 ] T , calculate the dq axis voltage reference value e dqref , denoted as e dqref =[e dref ,e qref ] T , and for e dqref Perform dq / ABC transformation to obtain the converter three-phase voltage reference value e ref , denoted as e ref =[e Aref ,e Bref ,e Cref ] T , the calculation formula is as follows: Where θ g is the synchronous phase angle of the transformer secondary voltage v2.

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