Subsequent commutation failure suppression strategy for adjusting direct current instruction based on power balance

Abstract

The invention discloses a follow-up commutation failure suppression strategy for adjusting a direct current instruction based on power balance, and the method comprises the steps: collecting the equipment data of an inverter station of a direct current system, and respectively constructing a lookup table of alternating voltage, quasi-steady-state active power and quasi-steady-state reactive power; collecting an inversion station pole control direct current instruction, a direct current voltage and a three-phase alternating current voltage in real time; selecting a three-phase AC voltage, and calculating a voltage effective value; obtaining an active expected direct current and a reactive expected direct current in combination with the voltage effective value and the lookup table; respectively taking a large value of the direct current instruction and the active expected current and a small value of the direct current instruction and the reactive expected current as an active instruction and a reactive instruction; comparing the active expected direct current with the reactive expected direct current, outputting a current comparison state, and selecting an active instruction or a reactive instruction as a final power current instruction according to the current comparison state. The direct current is adjusted based on power balance, the subsequent commutation failure is effectively inhibited, and stable operation of the direct current system is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of power systems and their automation technology, and specifically to a subsequent commutation failure suppression strategy based on power balance to regulate DC current commands. Background Technology

[0002] High-voltage direct current (HVDC) transmission systems with commutation converters perform exceptionally well in long-distance, high-capacity power transmission, offering high efficiency and stability, and playing a crucial role in my country's power resource allocation. However, because the semi-controlled thyristors in the converter components lack self-turn-off capability, AC faults on the inverter side can cause commutation failures in the HVDC inverter station converter. During the recovery process after the initial commutation failure, improper DC system control can lead to subsequent commutation failures, resulting in significant power fluctuations again. This invention focuses on the recovery phase after the initial commutation failure, proposing a new DC current command based on the balance of active and reactive power to suppress subsequent commutation failures.

[0003] Subsequent commutation failures directly reflect exceeding the turn-off angle limit. There is a clear relationship between the turn-off angle and active and reactive power: increasing the active power of the DC system is contingent on reducing the reactive power or turn-off angle of the AC system at the inverter station. The balance between active and reactive power determines whether the turn-off angle can maintain a safe level. Existing DC control systems do not adequately consider power balance. The control system restores active power by controlling the DC current or ensures safe commutation of the converter by controlling the turn-off angle. The effectiveness of a control system based on a single control objective is easily affected by various factors such as the DC current recovery characteristics, operating conditions, and fault intensity. The control time and adjustment range of the control system differ between restoring active power and controlling the turn-off angle. If the control system continuously increases the DC current, the restored active power will be high, resulting in a reactive power deficit, and the turn-off angle will inevitably fall below the limit, increasing the risk of subsequent commutation failures.

[0004] Therefore, power balance considerations need to be introduced into the control system of DC system: based on real-time DC voltage and AC voltage, DC current is adaptively adjusted to dynamically balance active power and reactive power, effectively suppressing subsequent commutation failure. Summary of the Invention

[0005] In view of this, the present invention provides a subsequent commutation failure suppression strategy based on power balancing to adjust the DC current command. By adjusting the current command from a power perspective, subsequent commutation failures are effectively suppressed, ensuring the transient stable operation of the DC system.

[0006] A subsequent commutation failure suppression strategy based on power balancing to regulate DC current command, applied to a high-voltage direct current transmission system, the method comprising:

[0007] Collect the series number and pole number of the six-pulse converter in the inverter station of the DC transmission system, the turns ratio and leakage reactance of the converter transformer in the inverter station, the capacitive reactance of the AC filter in the inverter station, the control command value of the constant turn-off angle in the inverter station, and the low-voltage current limiting control parameters.

[0008] Based on the collected data, an AC voltage-quasi-steady-state active power lookup table and an AC voltage-quasi-steady-state reactive power lookup table were constructed.

[0009] Collect the DC current command, DC voltage and three-phase AC voltage of the AC bus output from the inverter station pole control;

[0010] Based on the three-phase AC voltage of the inverter station's AC bus, the effective value of the AC voltage is calculated using the square average method.

[0011] By combining the effective value of AC voltage and the AC voltage-quasi-steady-state active power lookup table, the expected DC current of active power is calculated, and the maximum value of the expected DC current of active power and the pole control DC current command is taken as the active power command.

[0012] By combining the effective value of AC voltage and the AC voltage-quasi-steady-state reactive power lookup table, the expected DC current of reactive power is calculated, and the minimum value between the expected DC current of reactive power and the pole control DC current command is taken as the reactive power command.

[0013] The expected DC current of active power is compared with the expected DC current of reactive power to obtain the current comparison status;

[0014] Based on the current comparison status, either an active power command or a reactive power command is selected as the final power and current command.

[0015] Furthermore, the construction of the AC voltage-quasi-steady-state active power lookup table and the AC voltage-quasi-steady-state reactive power lookup table specifically includes:

[0016] Collect low-voltage current limiting control parameters I dcv =f v (U dcv ), where I dcv =f v (U dcv )for:

[0017] I dcv =f v (U dcv U is a pre-defined piecewise linear function relationship set by DC system operators. dcv I is the input for low-voltage current limiting control. dcv The output quantity for low-voltage current limiting control is as follows:

[0018]

[0019] Where k1, k2, ..., k n Let b1, b2, ..., b be the slopes of the piecewise linear functions corresponding to each voltage range. n U represents the intercept of the piecewise linear function corresponding to each voltage interval. dcv1 U dcv2 , ..., U dcvn Set threshold values ​​for each voltage segment. Collect data from the low-voltage current limiting control loop I. VD =f v (U dcv The data includes the slope of the piecewise linear function corresponding to each voltage range, the intercept of the piecewise linear function corresponding to each voltage range, and the threshold data for each voltage segment.

[0020] In the DC voltage range [0, U] dcvn In the sample, an average of 200 points were taken to obtain U. dci (i = 1, 2, ..., 200). Combined with I dcv =f v (U dcv ), calculate U dci Corresponding I dci ;Change U dci with I dci Pairing and constructing lookup tables for DC voltage and DC current (U dc ,I dc ).

[0021] Based on lookup table (U dc ,I dc ), calculate each pair of U dci with I dci The corresponding AC voltage value U aci As shown in the following formula:

[0022]

[0023] Where N is the number of six-pulse converters in series in the DC transmission system inverter station, and K p The number of poles of the inverter station of the collected DC transmission system, X T To collect the leakage reactance value of the converter transformer in the inverter station, K T The collected inverter station converter transformer turns ratio, γ ord The collected inverter station set the shut-off angle control command value.

[0024] Will U aci with U dci Pairing and constructing lookup tables for AC and DC voltages (U ac U dc ), change U aci with I dci Pairing and constructing lookup tables for AC voltage and DC current (U ac,I dc );

[0025] Based on lookup table (U ac ,I dc ), calculate each pair of U aci with I dci The corresponding active power P aci As shown in the following formula:

[0026]

[0027] Will U aci With P aci Pairing and constructing an inverter station AC voltage-quasi-steady-state active power lookup table (U ac ,P acU ).

[0028] Based on lookup table (U ac U dc ) and lookup table (U ac I dc ), calculate U for each group aci U dcvi and I dovi The corresponding reactive power Q aci As shown in the following formula:

[0029]

[0030] Where C represents the collected capacitive reactance of the inverter station's AC filter.

[0031] Will U aci With Q aci Pairing and constructing an inverter station AC voltage-quasi-steady-state reactive power lookup table (U ac Q acU Furthermore, the effective value of the AC voltage is calculated using the square average method based on the three-phase AC voltage of the inverter station's AC bus, as shown in the following formula;

[0032]

[0033] Among them, u acrms U represents the effective value of AC voltage. a u b u c This indicates the three-phase AC voltage of the AC bus of the inverter station.

[0034] Furthermore, the calculation of the expected DC current for active power, combining the effective value of AC voltage and the AC voltage-quasi-steady-state active power lookup table, and taking the maximum value between the expected DC current for active power and the pole control DC current command as the active power command, specifically includes:

[0035] Combined with the effective value of AC voltage uacrms AC voltage-quasi-steady-state active power lookup table (U ac P acU ), retrieve the value of u from the lookup table acrms The two closest AC voltage values ​​are named U. acp1 and U acp2 And obtain the corresponding active power, which is named P. acp1 and P acp2 .

[0036] u is calculated using linear interpolation. acrms The corresponding quasi-steady-state active power is given by the following formula:

[0037]

[0038] Where, p ac For u acrms The corresponding quasi-steady-state active power.

[0039] Furthermore, the expected DC current for active power is calculated as follows:

[0040]

[0041] Among them, i dcp The active power is the expected DC current.

[0042] Furthermore, the active power command is calculated as follows:

[0043] i pf =max(i dcp i dco )

[0044] Among them, i pf For active instructions, i dco This is a DC current command for the inverter station pole control output.

[0045] The method involves combining the effective value of AC voltage and the AC voltage-quasi-steady-state reactive power lookup table to calculate the expected DC current for reactive power. The minimum value between the expected DC current for reactive power and the pole control DC current command is taken as the reactive power command. Specifically, this includes:

[0046] Combined with the effective value of AC voltage u acrms AC voltage-quasi-steady-state reactive power lookup table (U ac Q acU ), retrieve the value of u from the lookup table acrms The two closest AC voltages are named U. acq1 and U acq2 And obtain the corresponding reactive power, which is named Q. acq1 and Q acq2 .

[0047] u is calculated using linear interpolation. acrms The corresponding quasi-steady-state reactive power is given by the following formula;

[0048]

[0049] Where, q ac For u acrms The corresponding quasi-steady-state reactive power.

[0050] Furthermore, the expected DC current for reactive power is calculated as follows:

[0051]

[0052] Among them, i dcq For the desired DC current of active power, u dc This is the collected DC voltage.

[0053] Furthermore, the reactive power command is calculated as follows:

[0054] i qf =min(i dcq i dco )

[0055] Among them, i qf This is a reactive instruction.

[0056] Furthermore, the comparison of the expected DC current for active power with the expected DC current for reactive power to obtain the current comparison state is as follows:

[0057]

[0058] Among them, s pq This is the current comparison state.

[0059] Furthermore, based on the current comparison state, an active power command or a reactive power command will be selected as the final power current command, as shown in the following formula:

[0060]

[0061] Among them, i dcf This is the final power current command.

[0062] The present invention has the following advantages over the prior art:

[0063] This invention proposes a strategy for suppressing subsequent commutation failures by adjusting the DC current command based on power balance. By setting the DC current command based on the inverter station's power characteristics, dynamic coordination of active and reactive power in the inverter station is achieved, effectively ensuring a safe commutation margin, suppressing subsequent commutation failures, and significantly improving the fault ride-through capability of the DC transmission system. Attached Figure Description

[0064] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0065] Figure 1 The flowchart of the commutation failure suppression strategy of Embodiment 1 of the present invention is shown in the abstract figure.

[0066] Figure 2 This is a logic diagram of the commutation failure suppression strategy in Embodiment 1 of the present invention.

[0067] Figure 3 This is a schematic diagram of the inverter station structure of the high-voltage direct current transmission system according to Embodiment 1 of the present invention.

[0068] Figure 4 The low-voltage current limiting control circuit I in Embodiment 1 of the present invention dcv =f V (U dov ).

[0069] Figure 5 The lookup table (U) of Embodiment 1 of the present invention ac U dc ) and lookup table (U ac I dc ).

[0070] Figure 6 The lookup table (U) of Embodiment 1 of the present invention ac ,P acU ) and lookup table (U ac Q acU ).

[0071] Figure 7 The three-phase AC voltage u of the inverter station AC bus in Embodiment 1 of the present invention a u b u c and its effective value u acrms The waveform diagram.

[0072] Figure 8The active power expected DC current i in Embodiment 1 of the present invention dcp Reactive power and expected DC current i dcq Current comparison state s pq DC current final command value i dcf The waveform diagram. Detailed Implementation

[0073] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0074] Example 1:

[0075] like Figure 1 and Figure 2 As shown, this embodiment provides a subsequent commutation failure suppression strategy based on power balancing to adjust DC current commands. This method is applied to high-voltage direct current transmission systems and includes the following steps:

[0076] S1. Construct an AC voltage-quasi-steady-state active power lookup table and an AC voltage-quasi-steady-state reactive power lookup table.

[0077] S11. Collect the series number and pole number of the six-pulse converter in the inverter station of the DC transmission system, the turns ratio and leakage reactance of the converter transformer in the inverter station, the capacitive reactance of the AC filter in the inverter station, the control command value of the constant turn-off angle in the inverter station and the low-voltage current limiting control parameters.

[0078] The inverter station structure of the high-voltage direct current transmission system in this embodiment is as follows: Figure 3 As shown. The pulse number N and pole number K of the converter in the inverter station of the DC transmission system are collected. p The turns ratio K of the converter transformer in the inverter station T With leakage reactance value X T The capacitive reactance C of the inverter station AC filter, and the control command value γ of the inverter station's set-off angle. ord Low-voltage current limiting control circuit I dcv =f v (U dcv ). I dcv =f v (U dcv )like Figure 4 As shown. In the DC voltage range [0, U... dcvn In the sample, an average of 200 points were taken to obtain U. dci (i = 1, 2, ..., 200), and according to I dcv =fv (U dcv ) Calculate the corresponding I dcvi ;Change U dcvi with I dcvi Pairing and constructing lookup tables for DC voltage and DC current (U dc ,I dc ).

[0079] Based on lookup table (U dc ,I dc ), calculate each pair of U dci with I dci The corresponding AC voltage value U aci As shown in the following formula:

[0080]

[0081] Will U aci with U dci Pairing and constructing lookup tables for AC and DC voltages (U ac U dc ), change U aci with I dci Pairing and constructing lookup tables for AC voltage and DC current (U ac I dc );

[0082] S12. Based on the collected data, construct an AC voltage-quasi-steady-state active power lookup table and an AC voltage-quasi-steady-state reactive power lookup table.

[0083] Based on lookup table (U ac ,I dc ), calculate each pair of U aci with I dci The corresponding active power P aci As shown in the following formula:

[0084]

[0085] Will U aci With P aci Pairing and constructing an inverter station AC voltage-quasi-steady-state active power lookup table (U ac P acU ),like Figure 6 As shown.

[0086] Based on lookup table (U ac U dc ) and lookup table (U ac ,I dc ), calculate U for each group aci U dcvi and I dcvi The corresponding reactive power Q aciAs shown in the following formula:

[0087]

[0088] Where C represents the collected capacitive reactance of the inverter station's AC filter.

[0089] Will U aci With Q aci Pairing and constructing an inverter station AC voltage-quasi-steady-state reactive power lookup table (U ac Q acU ),like Figure 6 As shown.

[0090] S2. Collect the DC current command, DC voltage and three-phase AC voltage of the inverter station pole control output; calculate the effective value of AC voltage using the square average method based on the three-phase AC voltage of the inverter station AC bus, as shown in the following formula;

[0091]

[0092] Among them, u acrms U represents the effective value of AC voltage. a u b u c This indicates the three-phase AC voltage of the AC bus of the inverter station.

[0093] u a u b u c and u acrms like Figure 7 As shown.

[0094] S3. Calculate the expected DC current for active power and the expected DC current for reactive power. Take the larger value of the pole control DC current command and the smaller value of the expected active current and the expected reactive current, respectively, as the active command and the reactive command.

[0095] S31. Combining the effective value of AC voltage and the AC voltage-quasi-steady-state active power lookup table, calculate the expected DC current for active power, and take the maximum value between the expected DC current for active power and the pole control DC current command as the active power command; specifically including:

[0096] Combined with the effective value of AC voltage u acrms AC voltage-quasi-steady-state active power lookup table (U ac ,P acU ), retrieve the value of u from the lookup table acrms The two closest AC voltage values ​​are named U. acp1 and U acp2 And obtain the corresponding active power, which is named P. acp1 and P acp2 .

[0097] u is calculated using linear interpolation. acrms The corresponding quasi-steady-state active power is given by the following formula:

[0098]

[0099] Where, p ac For u acrms The corresponding quasi-steady-state active power.

[0100] Furthermore, the expected DC current for active power is calculated as follows:

[0101]

[0102] Among them, i dcp The active power is the expected DC current.

[0103] i dcp like Figure 8 As shown.

[0104] Next, the active power command is calculated as follows:

[0105] i pf =max(i dcp i dco )

[0106] Among them, i pf For active instructions, i dco This is a DC current command for the inverter station pole control output.

[0107] S32. Combining the effective value of AC voltage and the AC voltage-quasi-steady-state reactive power lookup table, calculate the expected DC current for reactive power. Take the minimum value between the expected DC current for reactive power and the pole control DC current command as the reactive power command. Specifically, this includes:

[0108] Combined with the effective value of AC voltage u acrms AC voltage-quasi-steady-state reactive power lookup table (U ac Q acU ), retrieve the value of u from the lookup table acrms The two closest AC voltages are named U. acq1 and U acq2 And obtain the corresponding reactive power, which is named Q. acq1 and Q acq2 .

[0109] u is calculated using linear interpolation. acrms The corresponding quasi-steady-state reactive power is given by the following formula:

[0110]

[0111] Where, qac For u acrms The corresponding quasi-steady-state reactive power.

[0112] Furthermore, the expected DC current for reactive power is calculated as follows:

[0113]

[0114] Among them, i dcq For the desired DC current of active power, u dc This is the collected DC voltage.

[0115] i dcq like Figure 8 As shown.

[0116] Furthermore, the reactive power command is calculated as follows:

[0117] i qf =min(i dcq i doo )

[0118] Among them, i qf This is a reactive instruction.

[0119] S4. Compare the expected DC current of active power with the expected DC current of reactive power to obtain the current comparison state, as shown in the following formula:

[0120]

[0121] Among them, s pq This is the current comparison state.

[0122] s pq like Figure 8 As shown.

[0123] S5. Based on the current comparison status, select either the active power command or the reactive power command as the final power and current command, as shown in the following formula:

[0124]

[0125] Among them, i dcf This is the final power current command.

[0126] i dcf like Figure 8 As shown.

[0127] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware, and the corresponding program can be stored in a computer-readable storage medium.

[0128] It should be noted that although the method operations of the above embodiments are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the order of execution of the described steps may be changed. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

Claims

1. A subsequent commutation failure suppression strategy based on power balancing to adjust DC current command, which suppresses subsequent commutation failure by adjusting DC current command based on power balancing, and is applied to high-voltage direct current transmission systems, characterized in that... The method includes: Collect the series number and pole number of the six-pulse converter in the inverter station of the DC transmission system, the turns ratio and leakage reactance of the converter transformer in the inverter station, the capacitive reactance of the AC filter in the inverter station, the constant turn-off angle control command and the low-voltage current limiting control parameters of the inverter station; Based on the collected data, an AC voltage-quasi-steady-state active power lookup table and an AC voltage-quasi-steady-state reactive power lookup table were constructed. Collect the DC current command, DC voltage and three-phase AC voltage of the AC bus output from the inverter station pole control; Based on the three-phase AC voltage of the inverter station's AC bus, the effective value of the AC voltage is calculated using the square average method. By combining the effective value of AC voltage and the AC voltage-quasi-steady-state active power lookup table, the expected DC current of active power is calculated, and the maximum value of the expected DC current of active power and the pole control DC current command is taken as the active power command. By combining the effective value of AC voltage and the AC voltage-quasi-steady-state reactive power lookup table, the expected DC current of reactive power is calculated, and the minimum value between the expected DC current of reactive power and the DC current command of pole control is taken as the reactive power command. Compare the magnitudes of the expected DC current for active power and the expected DC current for reactive power to obtain the current comparison status; Based on the current comparison status, either an active power command or a reactive power command is selected as the final power and current command.

2. The subsequent commutation failure suppression strategy according to claim 1, characterized in that, The construction of the AC voltage-quasi-steady-state active power lookup table and the AC voltage-quasi-steady-state reactive power lookup table specifically includes: Collect low-voltage current limiting control parameters I dcv =f v (U dcv ), where I dcv =f v (U dcv )for: I dcv＝ f v (U dcv U is a pre-defined piecewise linear function relationship set by DC system operators. dcv I is the input for low-voltage current limiting control. dcv The output quantity for low-voltage current limiting control is as follows: Where k1, k2, ..., k n Let b1, b2, ..., b be the slopes of the piecewise linear functions corresponding to each voltage range. n U represents the intercept of the piecewise linear function corresponding to each voltage interval. dcv1 U dcv2 , ..., U dcvn Set threshold values ​​for each voltage segment. Collect data from the low-voltage current limiting control loop I. VD =f v (U dcv The data includes the slope of the piecewise linear function corresponding to each voltage range, the intercept of the piecewise linear function corresponding to each voltage range, and the threshold data for each voltage segment. In the DC voltage range [0, U] dcvn In the sample, an average of 200 points were taken to obtain U. dci (i = 1, 2, ..., 200). Combined with I dcv =f v (U dcv ), calculate U dci Corresponding I dci ;Change U dci with I dci Pairing and constructing lookup tables for DC voltage and DC current (U dc ,I dc ). Based on lookup table (U dc ,I dc ), calculate each pair of U dci with I dci The corresponding AC voltage value U aci As shown in the following formula: Where N is the number of six-pulse converters in series in the DC transmission system inverter station, and K p The number of poles of the inverter station of the collected DC transmission system, X T To collect the leakage reactance value of the converter transformer in the inverter station, K T The collected inverter station converter transformer turns ratio, γ ord The collected inverter station set the shut-off angle control command value. Will U aci with U dci Pairing and constructing lookup tables for AC and DC voltages (U ac U dc ), change U aci with I dci Pairing and constructing lookup tables for AC voltage and DC current (U ac ,I dc ); Based on lookup table (U ac ,I dc ), calculate each pair of U aci with I dci The corresponding active power P aci As shown in the following formula: Will U aci With P aci Pairing and constructing an inverter station AC voltage-quasi-steady-state active power lookup table (U ac ,P acU ). Based on lookup table (U ac U dc ) and lookup table (U ac ,I dc ), calculate U for each group aci U dcvi and I dcvi The corresponding reactive power Q aci As shown in the following formula: Where C represents the collected capacitive reactance of the inverter station's AC filter. Will U aci With Q aci Pairing and constructing an inverter station AC voltage-quasi-steady-state reactive power lookup table (U ac Q acU ).

3. The subsequent commutation failure suppression strategy according to claim 1, characterized in that, The effective value of the AC voltage is calculated using the square average method based on the three-phase AC voltage of the inverter station's AC bus, as shown in the following formula: Among them, u acrms U represents the effective value of AC voltage. a u b u c This indicates the three-phase AC voltage of the AC bus of the inverter station.

4. The subsequent commutation failure suppression strategy according to claim 1, characterized in that, The method involves combining the effective value of AC voltage and the AC voltage-quasi-steady-state active power lookup table to calculate the expected DC current for active power. The maximum value between the expected DC current for active power and the pole control DC current command is taken as the active power command. Specifically, this includes: Combined with the effective value of AC voltage u acrms AC voltage-quasi-steady-state active power lookup table (U ac ,P acU ), retrieve the value of u from the lookup table acrms The two closest AC voltage values ​​are named U. acp1 and U acp2 And obtain the corresponding active power, which is named P. acp1 and P acp2 . u is calculated using linear interpolation. acrms The corresponding quasi-steady-state active power is given by the following formula: Where, p ac For u acrms The corresponding quasi-steady-state active power. Furthermore, the expected DC current for active power is calculated as follows: Among them, i dcp The active power is the expected DC current. Furthermore, the active power command is calculated as follows: i pf =max(i dcp ,i dco ) Among them, i pf For active instructions, i dco This is a DC current command for the inverter station pole control output.

5. The subsequent commutation failure suppression strategy according to claim 1, characterized in that, Combining the effective value of AC voltage and the AC voltage-quasi-steady-state reactive power lookup table, the expected DC current for reactive power is calculated. The minimum value between the expected DC current for reactive power and the pole control DC current command is taken as the reactive power command, specifically including: Combined with the effective value of AC voltage u acrms AC voltage-quasi-steady-state reactive power lookup table (U ac Q acU ), retrieve the value of u from the lookup table acrms The two closest AC voltages are named U. acq1 and U acq2 And obtain the corresponding reactive power, which is named Q. acq1 and Q acq2 . u is calculated using linear interpolation. acrms The corresponding quasi-steady-state reactive power is given by the following formula: Where, q ac For u acrms The corresponding quasi-steady-state reactive power. Furthermore, the expected DC current for reactive power is calculated as follows: Among them, i dcq For the desired DC current of active power, u dc This is the collected DC voltage. Furthermore, the reactive power command is calculated as follows: in qf =min(in dcq ,in dco ) Among them, i qf This is a reactive instruction.

6. The subsequent commutation failure suppression strategy according to claim 1, characterized in that, The expected DC current for active power is compared with the expected DC current for reactive power to obtain the current comparison state, as shown in the following formula: Among them, s pq This is the current comparison state.

7. The subsequent commutation failure suppression strategy according to claim 1, characterized in that, The active or reactive power command will be selected as the final power and current command based on the current comparison status, as shown in the following formula: Among them, i dcf This is the final power current command.

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