Boost converter dc fault adaptive recovery method, device, equipment and medium

Abstract

The present application relates to the field of power system fault recovery, and more particularly to a kind of boost converter DC fault adaptive recovery method, device and equipment, adaptive recovery control is carried out to MMC-DR type DC boost converter, comprising: the difference of wind farm active power instruction value and active power actual value is obtained, the active power-voltage control link of realizing internal grid-connected point voltage amplitude coordinated stability is realized through no-static-difference active power control, and d-axis voltage reference value is generated;The difference of reactive power instruction value and reactive power actual value is obtained, the reactive frequency control link of realizing internal grid-connected point frequency coordinated stability is realized through the reactive droop control based on phase-locked loop, q-axis voltage instruction value is generated and real-time angular frequency and phase information are obtained;Through voltage control ring and current control ring, MMC control signal is generated;When detecting that the DC fault of certain port MMC occurs, the MMC of this end is locked, and the MMC of non-fault end is adaptively coordinated to operate at new operating point, i.e. internal AC voltage is stabilized at new amplitude and frequency, to realize fault ride-through;After removing fault, the MMC of fault end is unlocked and MMC control signal is updated, to realize the recovery of fault port.

Description

Technical Field

[0001] This invention relates to the field of power system fault recovery technology, and in particular to an adaptive recovery method, apparatus, equipment and medium for DC faults in a boost converter. Background Technology

[0002] As offshore wind power develops towards longer distances, larger scales, and deeper waters, traditional AC collection or AC transmission methods suffer from technical problems such as high reactive power demand, severe overvoltage, and high turbine coupling. In this context, a full DC offshore wind power "DC collection-DC transmission" system based on DC turbines offers advantages such as high conversion efficiency and small footprint, making it an effective way to support medium-voltage DC collection and high-voltage DC transmission for large-capacity units in future offshore wind farms. High-voltage, high-capacity, high-gain DC / AC converters are the core equipment for achieving medium-voltage DC collection and high-voltage DC transmission in full DC offshore wind power systems, meeting the requirements of high voltage ratio and high transmission efficiency at high voltage levels. Their topology and control strategies have become research hotspots in related fields.

[0003] Current research on DC-DC converter topologies has yielded some results, among which the isolated DC-DC converter structure based on MMC (Modular Multilevel Converter) and DR (Diode Rectifier) ​​is a good choice. This structure combines the advantages of low switching losses and low harmonic content of MMC with the high reliability and low cost of diode rectifiers. Furthermore, it can achieve high voltage gain and fault isolation through an AC transformer, exhibiting high technical and economic efficiency and system reliability. However, this structure has two problems due to the diode rectifier: First, due to the uncontrollability of the diode rectifier, the DC-DC boost converter lacks a controllable converter port control dimension, and cannot adopt the control strategy of ordinary isolated converters, i.e., constant DC voltage / power and constant reactive power control of the primary converter, and constant AC voltage and constant frequency control of the secondary converter; Second, when a DC fault occurs at one or more ports on the primary side of the DC-DC boost converter, due to the "low inertia" of the system, the fault develops and spreads extremely quickly, which will have a great impact on the normal operation of non-faulty ports, resulting in complex fault characteristics and propagation mechanisms, and difficulties in fault identification and isolation.

[0004] In existing technologies, protection schemes for DC-DC boost converters generally only consider the case where fault traveling waves cross the faulted port, without considering the impact of fault traveling waves crossing non-faulted ports. In recent years, with the continuous expansion of offshore wind power, the number and capacity of the collection-side ports of DC-DC boost converters will continue to increase, making the above problems increasingly apparent. To ensure the reliability of all-DC offshore wind power systems, it is necessary to study protection strategies for DC-DC boost converters to achieve fault crossing of non-faulted ports and rapid recovery of faulted ports after fault clearance in the event of a DC fault at one or more ports.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method, apparatus, device, and medium for adaptive recovery of DC faults in a boost converter, thereby effectively solving the problems in the background art.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a DC fault adaptive recovery method for a boost converter, which performs adaptive recovery control on an MMC-DR type DC boost converter, including:

[0008] The difference between the wind farm's active power command value and the actual active power value is obtained. Through active power control without steady-state error, an active power-voltage control loop with coordinated and stable voltage amplitude at the grid connection point inside the DC-DC boost converter is realized, generating a d-axis voltage reference value.

[0009] The difference between the reactive power command value and the actual reactive power value is obtained. The reactive frequency control loop of the DC boost converter with coordinated and stable frequency at the grid connection point is realized through reactive power droop control based on phase-locked loop. The q-axis voltage command value is generated and the real-time angular frequency and phase information are obtained.

[0010] MMC control signals are generated through voltage control loop and current control loop;

[0011] When a DC fault is detected in a port MMC, that port MMC is blocked. The non-faulty port MMCs will adaptively coordinate to operate at a new operating point through the MMC control signal, that is, the internal AC voltage is stabilized at a new amplitude and frequency, thus achieving fault ride-through.

[0012] After clearing the fault, the faulty end MMC is unlocked and the MMC control signal is updated to restore the faulty port.

[0013] Further, generating the d-axis voltage reference value includes: summing the difference after control by the PI controller with the AC voltage amplitude to generate the d-axis voltage reference value.

[0014]

[0015] Among them, P refi P is given by summing the transmitted power of each wind turbine in the wind farm at different locations operating under maximum power point tracking (MPPT). Wi k represents the actual active power value of each MMC. P k T These are the control parameters for active power PI control with zero steady-state error, V dref V0 is the AC voltage reference value on the d-axis and the AC voltage amplitude.

[0016] Furthermore, the reactive power command value is obtained by proportionally allocating values ​​based on the active power transmitted by the three-terminal MMC.

[0017] Furthermore, the generation of the q-axis voltage command value includes:

[0018] The difference between the reactive power command value and the actual value is controlled by droop.

[0019] The angular frequency command value is obtained by summing the angular frequency with the reference value.

[0020] The q-axis voltage command value is obtained by subtracting the angular frequency command value from the real-time angular frequency.

[0021] Furthermore, the q-axis voltage command value includes:

[0022]

[0023] Among them, Q refi Q is determined by the proportional distribution of active power transmitted by the three-terminal MMC based on their respective transmission ratios and by the droop factor. W k represents the actual capacitive reactive power output by the MMC. q k f These are the droop control system, ω ref ω and V are the reference and actual values ​​of the AC angular frequency, respectively; qref This is the reference value for the q-axis AC voltage.

[0024] Further, the step of inputting the q-axis voltage command value into the distributed phase-locked loop (PLL) to obtain real-time angular frequency and phase information includes:

[0025]

[0026] Where ω0 is the AC angular frequency command value; v qThis represents the q-axis component of the AC voltage.

[0027] Further, the step of inputting the d-axis voltage reference value into the voltage inner loop to obtain the current inner loop command value, and then inputting it into the current inner loop, includes:

[0028]

[0029] Among them, i dref with i qref This is the reference value for the d-axis current and the q-axis current; k vdP ,,k vqP k vdT k vqT These are the PI control parameters of the voltage control loop; C is the capacitance value of the AC filter.

[0030] Furthermore, the reference value of the internal potential of the modular multilevel converter (MMC) obtained through PI control is used to generate a control signal, including:

[0031]

[0032] Among them, e dref With e qref k represents the dq-axis component of the internal potential of the MMC. idP ,,k iqP k idT k iqT These are the PI control parameters for the current control loop; L eq This is the equivalent inductance on the AC side of the MMC.

[0033] A DC fault adaptive recovery device for a boost converter, using the method described above, includes:

[0034] The active power control unit acquires the difference between the wind farm's active power command value and the actual active power value. Through zero steady-state error active power control, it realizes a coordinated and stable active power-voltage control loop for the voltage amplitude at the grid connection point inside the DC-DC boost converter, and generates a d-axis voltage reference value.

[0035] The reactive power and frequency control unit obtains the difference between the reactive power command value and the actual reactive power value, and realizes the reactive frequency control link with frequency coordination and stability at the grid connection point inside the DC boost converter through reactive power droop control based on phase-locked loop, generates q-axis voltage command value and obtains real-time angular frequency and phase information.

[0036] The MMC control unit is used to generate MMC control signals through a voltage control loop and a current control loop;

[0037] The fault recovery unit is used to block the MMC at a certain port when a DC fault is detected at a certain port MMC. The non-faulty MMCs will adaptively coordinate to operate at a new operating point through the MMC control signal, that is, the internal AC voltage will be stabilized at a new amplitude and frequency, thus achieving fault ride-through.

[0038] It is also used to unlock the faulty end MMC and update the MMC control signal after clearing the fault, so as to realize the recovery of the faulty port.

[0039] The present invention also includes a computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the method as described above.

[0040] The present invention also includes a storage medium having a computer program stored thereon, which, when executed by a processor, implements the method as described above.

[0041] The beneficial effects of this invention are as follows:

[0042] When one or two MMCs experience a DC fault, the system detects and blocks the MMCs after the fault occurs. This reduces the active power transmitted by the entire system, causing fluctuations in the AC side voltage and current of the non-faulty MMCs, resulting in oscillations. In the DC fault adaptive recovery control method for the MMC-DR type DC-DC boost converter, the active power-voltage control loop determines the AC grid-connected point voltage amplitude based on the real-time changes in the system's transmitted active power, while the reactive power frequency control loop determines the AC grid-connected point voltage frequency based on the reactive power reference value that changes by tracking the changes in the system's transmitted active power. Through these two controls, the steady-state operating point of the MMC-DR type DC-DC boost converter is determined under the new state. Control signals are then sent to the MMCs through voltage and current control to ensure they operate at the new steady-state operating point, achieving stable system operation and fault ride-through for non-faulty ports. After the fault is cleared, the faulty MMC is put back into operation, and the wind farm power begins to be transmitted. At this time, the active power transmitted by the entire system begins to rise. In the DC fault adaptive recovery control method of the MMC-DR type DC boost converter, the active power-voltage control link can determine the AC grid connection point voltage amplitude according to the real-time changes in the system transmitted active power, and the reactive power frequency control link can determine the AC grid connection point voltage frequency according to the reactive power reference value that changes by tracking the changes in the system transmitted active power. The steady-state operating point of the MMC-DR type DC boost converter under the new state is determined through the two controls, and control signals are sent to the MMC through voltage control and current control so that the faulty MMC can be quickly connected to the AC system and achieve mutual synchronization. Attached Figure Description

[0043] 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 recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0044] Figure 1 This is a flowchart of the method in Example 1;

[0045] Figure 2 This is a schematic diagram of the device in Example 1;

[0046] Figure 3 This is a schematic diagram of the all-DC offshore wind power system in Example 2;

[0047] Figure 4 This is a schematic diagram of the control strategy in Example 2;

[0048] Figure 5 This is a flowchart of the system adaptive recovery process in the fault situation in Example 2;

[0049] Figure 6 The AC voltage waveform diagram is shown in Example 2;

[0050] Figure 7 The active power waveform diagram is shown in Example 2;

[0051] Figure 8 The reactive power waveform diagram is shown in Example 2.

[0052] Figure 9 This is a frequency waveform diagram from Example 2;

[0053] Figure 10 This is a schematic diagram of the structure of a computer device. Detailed Implementation

[0054] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0055] like Figure 1 As shown: An adaptive recovery method for DC faults in a boost converter, comprising the following steps:

[0056] Adaptive recovery control for the MMC-DR type DC-DC boost converter includes:

[0057] The difference between the wind farm's active power command value and the actual active power value is obtained. Through active power control without steady-state error, an active power-voltage control loop with coordinated and stable voltage amplitude at the grid connection point inside the DC-DC boost converter is realized, generating a d-axis voltage reference value.

[0058] The difference between the reactive power command value and the actual reactive power value is obtained. The reactive frequency control loop of the DC boost converter with coordinated and stable frequency at the grid connection point is realized through reactive power droop control based on phase-locked loop. The q-axis voltage command value is generated and the real-time angular frequency and phase information are obtained.

[0059] MMC control signals are generated through voltage control loop and current control loop;

[0060] When a DC fault is detected in a port MMC, that port MMC is blocked. The non-faulty port MMCs will adaptively coordinate to operate at a new operating point through the MMC control signal, that is, the internal AC voltage is stabilized at a new amplitude and frequency, thus achieving fault ride-through.

[0061] After clearing the fault, the faulty end MMC is unlocked and the MMC control signal is updated to restore the faulty port.

[0062] When one or two MMCs experience a DC fault, the system detects and blocks the MMCs after the fault occurs. This reduces the active power transmitted by the entire system, causing fluctuations in the AC side voltage and current of the non-faulty MMCs, resulting in oscillations. In the DC fault adaptive recovery control method for the MMC-DR type DC-DC boost converter, the active power-voltage control loop determines the AC grid-connected point voltage amplitude based on the real-time changes in the system's transmitted active power, while the reactive power frequency control loop determines the AC grid-connected point voltage frequency based on the reactive power reference value that changes by tracking the changes in the system's transmitted active power. Through these two controls, the steady-state operating point of the MMC-DR type DC-DC boost converter is determined under the new state. Control signals are then sent to the MMCs through voltage and current control to ensure they operate at the new steady-state operating point, achieving stable system operation and fault ride-through for non-faulty ports. After the fault is cleared, the faulty MMC is put back into operation, and the wind farm power begins to be transmitted. At this time, the active power transmitted by the entire system begins to rise. In the DC fault adaptive recovery control method of the MMC-DR type DC boost converter, the active power-voltage control link can determine the AC grid connection point voltage amplitude according to the real-time changes in the system transmitted active power, and the reactive power frequency control link can determine the AC grid connection point voltage frequency according to the reactive power reference value that changes by tracking the changes in the system transmitted active power. The steady-state operating point of the MMC-DR type DC boost converter under the new state is determined through the two controls, and control signals are sent to the MMC through voltage control and current control so that the faulty MMC can be quickly connected to the AC system and achieve mutual synchronization.

[0063] In this embodiment, the active power command value of the wind farm is obtained through the wind farm maximum power tracking (MPPT).

[0064] Generating the d-axis voltage reference value includes: summing the difference after PI controller control with the AC voltage amplitude to generate the d-axis voltage reference value.

[0065]

[0066] Among them, P refi P is given by summing the transmitted power of each wind turbine in the wind farm at different locations operating under maximum power point tracking (MPPT). Wi k represents the actual active power value of each MMC. P k T These are the control parameters for active power PI control with zero steady-state error, V dref V0 is the AC voltage reference value on the d-axis and the AC voltage amplitude.

[0067] The reactive power command value is obtained by proportionally allocating the active power transmitted by each of the three-terminal MMC.

[0068] The generated q-axis voltage command values ​​include:

[0069] The difference between the reactive power command value and the actual value is controlled by droop.

[0070] The angular frequency command value is obtained by summing the angular frequency with the reference value.

[0071] The q-axis voltage command value is obtained by subtracting the angular frequency command value from the real-time angular frequency.

[0072] The q-axis voltage command values ​​include:

[0073] w ref =w0+k q (Q w -Q refi );

[0074] V qref =k f (w ref -w);

[0075] Among them, Q refi Q is determined by the proportional distribution of active power transmitted by the three-terminal MMC based on their respective transmission ratios and by the droop factor. W k represents the actual capacitive reactive power output by the MMC. q k f These are the droop control system, ω ref ω and V are the reference and actual values ​​of the AC angular frequency, respectively; qref This is the reference value for the q-axis AC voltage.

[0076] The q-axis voltage command value is input into the distributed phase-locked loop (PLL) to obtain real-time angular frequency and phase information, including:

[0077]

[0078] Where ω0 is the AC angular frequency command value; v q This represents the q-axis component of the AC voltage.

[0079] Input the d-axis voltage reference value into the voltage inner loop to obtain the current inner loop command value, and input the current inner loop, including:

[0080]

[0081] Among them, i dref with i qref This is the reference value for the d-axis current and the q-axis current; k vdP ,,k vqP k vdT k vqT These are the PI control parameters of the voltage control loop; C is the capacitance value of the AC filter.

[0082] The reference value of the internal potential of the modular multilevel converter (MMC) is obtained through PI control and used to generate control signals, including:

[0083]

[0084] Among them, e dref With e qref k represents the dq-axis component of the internal potential of the MMC. idP ,,k iqP k idT k iqT These are the PI control parameters for the current control loop; L eq This is the equivalent inductance on the AC side of the MMC.

[0085] like Figure 2 As shown, this embodiment also includes a DC fault adaptive recovery device for a boost converter, using the method described above, including:

[0086] The active power control unit acquires the difference between the wind farm's active power command value and the actual active power value. Through zero steady-state error active power control, it realizes a coordinated and stable active power-voltage control loop for the voltage amplitude at the grid connection point inside the DC-DC boost converter, and generates a d-axis voltage reference value.

[0087] The reactive power and frequency control unit obtains the difference between the reactive power command value and the actual reactive power value, and realizes the reactive frequency control link with frequency coordination and stability at the grid connection point inside the DC boost converter through reactive power droop control based on phase-locked loop, generates q-axis voltage command value and obtains real-time angular frequency and phase information.

[0088] The MMC control unit is used to generate MMC control signals through a voltage control loop and a current control loop;

[0089] The fault recovery unit is used to block the MMC at a certain port when a DC fault is detected at a certain port MMC. The non-faulty MMCs will adaptively coordinate to operate at a new operating point through the MMC control signal, that is, the internal AC voltage will be stabilized at a new amplitude and frequency, thus achieving fault ride-through.

[0090] It is also used to unlock the faulty end MMC and update the MMC control signal after clearing the fault, so as to realize the recovery of the faulty port.

[0091] Example 2:

[0092] Reference Figure 3 The all-DC offshore wind power system comprises an offshore DC wind farm, a DC boost converter, and an onshore AC system. The all-DC offshore wind farm consists of DC wind turbines configured in a specific grid arrangement. The DC wind turbine structure typically uses a full-power turbine + AC / DC converter + DC / DC converter structure, with the two converter stages implementing maximum power point tracking (MPPT) and constant DC voltage control, respectively. The DC boost converter consists of an MMC and a diode rectifier. The multi-port input side of the MMC is called the medium-voltage collection side, used to collect the active power from the wind farm at medium voltage; the transformer is used for DC voltage boosting and fault isolation; and the diode rectifier is used to output active power. The onshore AC system generally consists of an onshore converter station and an AC grid. The onshore converter station is an MMC converter station, employing constant DC voltage control. In this invention, the MMC is a three-phase voltage fully controlled converter, operating in inverter mode during normal operation.

[0093] Based on the above-mentioned all-DC offshore wind power system and DC boost converter structure, this invention proposes a method such as... Figure 4 The DC fault adaptive recovery and protection strategy for a full DC offshore wind power DC-DC boost converter, as shown, includes the following steps:

[0094] Step 1: The difference between the active power command value given by the wind farm MPPT and the actual value is adjusted by a PI controller with zero steady-state error, and summed with the AC voltage amplitude to generate a d-axis voltage reference value. This can be expressed as:

[0095]

[0096] Among them, P ref k is the active power command given by the maximum power point tracking (MPPT) on the wind farm side. P k T These are the control parameters for PI control. V dref V0 is the AC voltage reference value on the d-axis and the AC voltage amplitude.

[0097] Step Two: The reactive power control loop setpoint is proportionally allocated to the output by the three-terminal MMC based on the active power transmitted by each terminal. The difference between the reactive power command value and the actual value is summed with the reference angular frequency through droop control to obtain the angular frequency command value. The difference between the angular frequency command value and the real-time angular frequency yields the q-axis voltage command value. This can be expressed as:

[0098] w ref =w0+k q (Q w -Q refi (2)

[0099] V qref =k f (w ref -w) (3)

[0100] Among them, Q ref k is the active power command given by the maximum power point tracking (MPPT) on the wind farm side. q k f These are the droop control system, ω ref ω and V are the reference and actual values ​​of the AC angular frequency, respectively; qref This is the reference value for the q-axis AC voltage.

[0101] Step 3: The frequency control loop of the distributed PLL takes the q-axis voltage as input, sums it with the angular frequency reference value through a PI circuit to obtain the real-time angular frequency, and then obtains the phase information of the port through integration. This can be expressed as:

[0102]

[0103] Where ω0 is the AC angular frequency command value; v q This represents the q-axis component of the AC voltage.

[0104] Step 4: The voltage inner loop, based on the received voltage command, uses PID control to obtain the current inner loop command value and sends it to the current inner loop. This can be represented as:

[0105]

[0106] Among them, i dref with i qref This is the reference value for the d-axis current and the q-axis current; k vdP ,,kvqP k vdT k vqT These are the PI control parameters; C is the capacitance of the AC filter.

[0107] Step 5: The inner current loop, based on the received current command, obtains the MMC internal potential reference value through PI control, which is then used to generate the control signal. This can be represented as...

[0108]

[0109] Among them, e dref With e qref k represents the dq-axis component of the internal potential of the MMC. idP ,,k iqP k idT k iqT These are the PI control parameters; L eq This is the equivalent inductance on the AC side of the MMC.

[0110] Step 6: When a DC fault is detected in a port MMC, immediately lock out that port.

[0111] Based on the above control strategy, the adaptive recovery process of non-faulty ports is as follows: Figure 5 As shown. When the i-th MMC experiences a DC fault, its port is immediately blocked, and its output active power decreases. At this time, its active power reference value P... refi The voltage decreases. Under the action of the active power-AC voltage control loop, the MMC AC voltage v i This also reduces the reactive power Q supplied by the MMC. wi Subsequently, under the reactive power-frequency control, both the MMC AC angular frequency ω and phase angle difference δi will decrease to 0, until blocking occurs. Simultaneously, the active power P transferred by the MMC to the diode rectifier... wi Reduce to 0, gradually tracking the already decreasing active power reference value P. refi This process leads to a new equilibrium state. Furthermore, this process causes a decrease in both active and reactive power transmitted by the diode rectifier. Under the action of reactive power-frequency control droop control, the AC side frequency ω of the non-faulty MMCj... j It also gradually decreases until a new synchronization state is reached.

[0112] Simulation verification

[0113] Build in PSCAD / EMTDC Figure 3 The simulation model of a full DC offshore wind power system is shown. In the simulation model, a fault occurs on the DC side of MMC3 at 1.5 seconds, locking the converter; the fault is cleared at 1.6 seconds. According to... Figure 6 , Figure 7 , Figure 8 , Figure 9 It can be seen that the DC fault adaptive control and protection strategy proposed in this invention can achieve fault crossing of non-faulty ports and rapid recovery of faulty ports when a certain port fails.

[0114] Please see Figure 10 The diagram shows a structural schematic of a computer device provided in an embodiment of this application. An embodiment of this application provides a computer device 400, including a processor 410 and a memory 420. The memory 420 stores a computer program executable by the processor 410, and when the computer program is executed by the processor 410, it performs the method described above.

[0115] This application embodiment also provides a storage medium 430, on which a computer program is stored, and the computer program is executed by a processor 410 to perform the above method.

[0116] The storage medium 430 can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0117] In the description of this invention, 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 indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0118] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0119] 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. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, 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.

[0120] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0121] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0122] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0123] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0124] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be 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 DC fault adaptive recovery method for a boost converter, comprising adaptive recovery control of an MMC-DR type DC boost converter, characterized in that, include: The difference between the wind farm's active power command value and the actual active power value is obtained. Through active power control without steady-state error, an active power-voltage control loop with coordinated and stable voltage amplitude at the grid connection point inside the DC boost converter is realized, generating a d-axis voltage reference value. The difference between the reactive power command value and the actual reactive power value is obtained. The reactive frequency control loop of the DC boost converter with coordinated and stable frequency at the grid connection point is realized through reactive power droop control based on phase-locked loop. The q-axis voltage command value is generated and the real-time angular frequency and phase information are obtained. MMC control signals are generated through voltage control loop and current control loop; When a DC fault is detected in a port MMC, that port MMC is blocked. The non-faulty port MMCs will adaptively coordinate to operate at a new operating point through the MMC control signal, that is, the internal AC voltage is stabilized at a new amplitude and frequency, thus achieving fault ride-through. After clearing the fault, the faulty end MMC is unlocked and the MMC control signal is updated to restore the faulty port; The generation of the d-axis voltage reference value includes: summing the difference after control by the PI controller with the AC voltage amplitude to generate the d-axis voltage reference value. ； Among them, P refi P is given by summing the transmitted power of each wind turbine in the wind farm at different locations operating under maximum power point tracking (MPPT). Wi k represents the actual active power value of each MMC. P k T These are the control parameters for active power PI control with zero steady-state error, V dref V0 is the AC voltage reference value on the d-axis, and V0 is the AC voltage amplitude. The generated q-axis voltage command value includes: The difference between the reactive power command value and the actual value is controlled by droop. The angular frequency command value is obtained by summing the angular frequency with the reference value. The q-axis voltage command value is obtained by subtracting the angular frequency command value from the real-time angular frequency. The q-axis voltage command value includes: ； ； Among them, Q refi Q is determined by the proportional distribution of active power transmitted by the three-terminal MMC based on their respective transmission ratios and by the droop factor. W k represents the actual capacitive reactive power output by the MMC. q k f These are the droop control system, ω ref ω and ω0 represent the reference and actual values ​​of the AC angular frequency, respectively; ω0 is the reference AC angular frequency; V qref This is the reference value for the q-axis AC voltage.

2. The adaptive DC fault recovery method for boost converter according to claim 1, characterized in that, The reactive power command value is obtained by proportionally allocating the values ​​of the active power transmitted by the three-terminal MMC.

3. The adaptive DC fault recovery method for boost converter according to claim 1, characterized in that, Acquire real-time angular frequency and phase information, including: The q-axis voltage command value is input into the distributed phase-locked loop (PLL) to obtain the real-time angular frequency, and the phase information is obtained based on the real-time angular frequency. ； Where ω0 is the AC angular frequency command value; k lP k is the proportional control parameter for the frequency control loop of a distributed phase-locked loop (PLL). lT The integral control parameters for the frequency control loop of the distributed phase-locked loop (PLL); v q This represents the q-axis component of the AC voltage.

4. The adaptive DC fault recovery method for boost converter according to claim 1, characterized in that, The MMC control signal is generated through the voltage control loop and the current control loop, including: The d-axis voltage reference value is input into the voltage control loop to obtain the current inner loop command value, and the current inner loop command value is input into the current control loop, wherein the current inner loop command value includes the d-axis current reference value and the q-axis current reference value: ； Among them, i dref with i qref This is the reference value for the d-axis current and the q-axis current; k vdP ,,k vqP k vdT k vqT These are the PI control parameters of the voltage control loop; C is the capacitance of the AC filter; v d and v q These represent the d-axis and q-axis components of the AC voltage at the grid connection point inside the DC-DC boost converter in the dq coordinate system.

5. The adaptive DC fault recovery method for a boost converter according to claim 4, characterized in that, The MMC control signal is generated through a voltage control loop and a current control loop, and also includes: ； Among them, e dref With e qref k represents the dq-axis component of the internal potential of the MMC. idP ,,k iqP k idT k iqT These are the PI control parameters for the current control loop; L eq The equivalent inductance of the MMC AC side; i q and i d These represent the d-axis and q-axis components of the AC side current of the modular multilevel converter (MMC) in the dq coordinate system.

6. A DC fault adaptive recovery device for a boost converter, characterized in that, Using the method as described in any one of claims 1 to 5, comprising: The active power control unit acquires the difference between the wind farm's active power command value and the actual active power value. Through zero steady-state error active power control, it realizes a coordinated and stable active power-voltage control loop at the grid connection point voltage amplitude inside the DC-DC boost converter, generating a d-axis voltage reference value. The reactive power and frequency control unit obtains the difference between the reactive power command value and the actual reactive power value, and realizes the reactive frequency control link with frequency coordination and stability at the grid connection point inside the DC boost converter through reactive power droop control based on phase-locked loop, generates q-axis voltage command value and obtains real-time angular frequency and phase information. The MMC control unit is used to generate MMC control signals through a voltage control loop and a current control loop; The fault recovery unit is used to block the MMC at a certain port when a DC fault is detected at a certain port MMC. The non-faulty MMCs will adaptively coordinate to operate at a new operating point through the MMC control signal, that is, the internal AC voltage will be stabilized at a new amplitude and frequency, thus achieving fault ride-through. It is also used to unlock the faulty end MMC and update the MMC control signal after clearing the fault, so as to realize the recovery of the faulty port.

7. A computer device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the method as described in any one of claims 1-5.

8. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the method as described in any one of claims 1-5.

Images