Control method and system based on multi-terminal hybrid DC networking

Abstract

The invention discloses a control method and system based on multi-terminal hybrid DC networking, and the method comprises the steps: determining the multi-terminal hybrid DC networking, enabling the AC sides of a transmitting end MMC and a transmitting end LCC to be connected with a first new energy base and a second new energy base correspondingly, and enabling the DC sides of the transmitting end MMC and the transmitting end LCC to be connected in parallel; the direct current side of the sending end MMC and the direct current side of the sending end LCC are connected in parallel and then are connected with the direct current side of the receiving end LCC through a direct current line, and the alternating current side of the receiving end LCC is connected with a receiving end alternating current power grid; based on the connection state of a first new energy base connected with the sending end MMC and the operation states of the sending end MMC and the sending end LCC, determining the operation mode of the DC networking; and based on the operation mode of the direct current network, determining a corresponding control method and a starting method, and completing the operation of the hybrid direct current system. The invention provides a new direct current networking mode suitable for some large-scale new energy transmission scenes, and the capability of transmitting large-scale new energy through direct current is improved.

Description

Technical Field

[0001] The present invention relates to the field of high voltage direct current transmission technology in the field of power systems, and more specifically, to a control method and system based on multi-terminal hybrid direct current networking. Background Art

[0002] Since the western new energy base is far away from the sending-end AC main grid, DC transmission is one of the main forms of transmission.

[0003] Considering the natural geographical and resource and environmental limitations, the gathering forms of new energy bases are complex and diverse. In some cases, the entire source-side system presents weak voltage support and even some large-scale new energy sites present island transmission characteristics. If conventional DC transmission based on line commutated converter (LCC) is used to transmit power from large-scale new energy bases, when the sending end is a new energy base with a grid-following type or a new energy base with a low proportion of grid-building equipment, both the source side and the DC need strong supporting power sources to operate stably. The operating conditions are relatively harsh, which seriously limits the new energy transmission capacity. Flexible DC transmission based on modular multilevel converter (MMC) can provide a certain voltage support capability for the new energy base at the sending end, but due to the voltage level and capacity, further technical improvement is still needed in the context of large-scale new energy base consumption. The single-type DC transmission technology of new energy can no longer meet the transmission needs of multi-type large-scale new energy with ultra-large scale and decentralized development. It is urgent to study the networking form of new multi-type converter hybrid DC transmission system. Summary of the invention

[0004] The technical solution of the present invention provides a control method and system based on multi-terminal hybrid DC networking to solve the problem of how to network and control multi-terminal hybrid DC transmitted by large-scale renewable energy.

[0005] In order to solve the above problems, the present invention provides a control method based on multi-terminal hybrid DC networking, the method:

[0006] Determine a multi-terminal hybrid DC network, wherein: the AC sides of the sending-end MMC and the sending-end LCC are connected to the corresponding first new energy base and second new energy base respectively, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel;

[0007] The DC sides of the sending-end MMC and the sending-end LCC are connected in parallel and then connected to the DC side of the receiving-end LCC through a DC line, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid;

[0008] Based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, the operation mode of the DC network is determined; wherein the connection state includes: connection and disconnection; the operation state includes: start and stop; the operation model includes: a first operation mode, a second operation mode, a third operation mode and a fourth operation mode;

[0009] Based on the operation mode of the DC network, the corresponding control method and starting method are determined to complete the operation of the hybrid DC system.

[0010] Preferably, the operation mode of the DC network is determined based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, and the first operation mode is:

[0011] The first new energy base is connected to the sending-end AC power grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is in an exited operation state;

[0012] The second operating mode is:

[0013] The second new energy base is connected to the sending-end AC power grid, the sending-end MMC is in an exited operation state, and the sending-end LCC and the receiving-end LCC are in an operating state;

[0014] The third operating mode is:

[0015] The first new energy base operates in an isolated island, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation;

[0016] The fourth operation mode is:

[0017] The first new energy base is connected to the sending-end AC power grid, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation.

[0018] Preferably, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the first control method of the first operation mode is:

[0019] The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop;

[0020] The receiving-end LCC adopts constant DC voltage control.

[0021] Preferably, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the third control method of the third operation mode is:

[0022] The sending-end MMC adopts a constant AC voltage and a constant frequency control mode, and the constant AC voltage and a constant frequency control mode includes a voltage loop and a current loop;

[0023] The sending-end LCC adopts fixed active power or fixed DC current control;

[0024] The receiving-end LCC adopts constant DC voltage control.

[0025] Preferably, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the fourth control method of the fourth operation mode is:

[0026] The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop;

[0027] The sending-end LCC adopts fixed active power or fixed DC current control;

[0028] The receiving-end LCC adopts constant DC voltage control.

[0029] Preferably, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the first starting method of the first operation mode is:

[0030] Performing uncontrollable charging on the sending-end MMC;

[0031] Controllably charging the sending-end MMC;

[0032] Unlocking the receiving-end LCC;

[0033] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0034] Preferably, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the starting method of the third operation mode is:

[0035] Starting the sending-end LCC and the receiving-end LCC;

[0036] Performing uncontrollable charging on the sending-end MMC;

[0037] Controllably charging the sending-end MMC;

[0038] Switching the control strategy of the sending-end MMC to constant AC voltage and constant frequency control;

[0039] The first new energy base is connected to the grid for operation.

[0040] Preferably, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the starting method of the fourth operation mode is:

[0041] Starting the sending-end LCC and the receiving-end LCC;

[0042] Performing uncontrollable charging on the sending-end MMC;

[0043] Controllably charging the sending-end MMC;

[0044] Connecting the sending-end MMC to the DC side;

[0045] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0046] Based on another aspect of the present invention, the present invention provides a multi-terminal hybrid DC networking and control system, wherein:

[0047] A first networking unit, used for connecting the AC sides of the sending-end MMC and the sending-end LCC to the corresponding first new energy base and the second new energy base respectively, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel;

[0048] A second networking unit is used for connecting the DC sides of the sending-end MMC and the sending-end LCC in parallel and then connecting them to the DC side of the receiving-end LCC through a DC line, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid;

[0049] A determination unit, configured to determine an operation mode of the DC network based on a connection state of a first new energy base connected to the sending-end MMC, and an operation state of the sending-end MMC and the sending-end LCC; wherein the connection state includes: connected and disconnected; the operation state includes: started and disabled; the operation model includes: a first operation mode, a second operation mode, a third operation mode, and a fourth operation mode;

[0050] The result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network to complete the operation of the hybrid DC system.

[0051] Preferably, the determining unit is used to determine the operation mode of the DC network based on the connection state of the first new energy base connected to the sending-end MMC and the operation states of the sending-end MMC and the sending-end LCC, and is also used to:

[0052] The operation mode includes a first operation mode, wherein the first operation mode is:

[0053] The first new energy base is connected to the sending-end AC power grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is in an exited operation state;

[0054] The operation mode includes a second operation mode, and the second operation mode is:

[0055] The second new energy base is connected to the sending-end AC power grid, the sending-end MMC is in an exited operation state, and the sending-end LCC and the receiving-end LCC are in an operating state;

[0056] The operation mode includes a third operation mode, and the third operation mode is:

[0057] The first new energy base operates in an isolated island, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation;

[0058] The operation mode includes a fourth operation mode, and the fourth operation mode is:

[0059] The first new energy base is connected to the sending-end AC power grid, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation.

[0060] Preferably, the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the first control method of the first operation mode is:

[0061] The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop;

[0062] The receiving-end LCC adopts constant DC voltage control.

[0063] Preferably, the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the third control method of the third operation mode is:

[0064] The sending-end MMC adopts a constant AC voltage and a constant frequency control mode, and the constant AC voltage and a constant frequency control mode includes a voltage loop and a current loop;

[0065] The sending-end LCC adopts fixed active power or fixed DC current control;

[0066] The receiving-end LCC adopts constant DC voltage control.

[0067] Preferably, the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the fourth control method of the fourth operation mode is:

[0068] The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop;

[0069] The sending-end LCC adopts fixed active power or fixed DC current control;

[0070] The receiving-end LCC adopts constant DC voltage control.

[0071] Preferably, the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the first starting method of the first operation mode is:

[0072] Performing uncontrollable charging on the sending-end MMC;

[0073] Controllably charging the sending-end MMC;

[0074] Unlocking the receiving-end LCC;

[0075] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0076] Preferably, the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the starting method of the third operation mode is:

[0077] Starting the sending-end LCC and the receiving-end LCC;

[0078] Performing uncontrollable charging on the sending-end MMC;

[0079] Controllably charging the sending-end MMC;

[0080] Switching the control strategy of the sending-end MMC to constant AC voltage and constant frequency control;

[0081] The first new energy base is connected to the grid for operation.

[0082] Preferably, the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the starting method of the fourth operation mode is:

[0083] Starting the sending-end LCC and the receiving-end LCC;

[0084] Performing uncontrollable charging on the sending-end MMC;

[0085] Controllably charging the sending-end MMC;

[0086] Connecting the sending-end MMC to the DC side;

[0087] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0088] Based on another aspect of the present invention, the present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program is used to execute a control method based on a multi-terminal hybrid DC networking.

[0089] Based on another aspect of the present invention, the present invention provides an electronic device, the electronic device comprising: a processor and a memory; wherein,

[0090] The memory is a memory for storing instructions executable by the processor;

[0091] The processor is used to read the executable instructions from the memory and execute the instructions to implement a control method based on multi-terminal hybrid DC networking.

[0092] The technical solution of the present invention provides a control method and system based on multi-terminal hybrid DC networking, wherein the method: determines the multi-terminal hybrid DC networking, wherein: the AC sides of the sending-end MMC and the sending-end LCC are respectively connected to the corresponding first new energy base and second new energy base, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel; the DC sides of the sending-end MMC and the sending-end LCC are connected to the DC side of the receiving-end LCC through a DC line after being connected in parallel, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid; based on the connection state of the first new energy base connected to the sending-end MMC, and the operating state of the sending-end MMC and the sending-end LCC, the operating mode of the DC networking is determined; wherein the connection state includes: connection and disconnection; the operating state includes: start-up and deactivation; the operating model includes: a first operating mode, a second operating mode, a third operating mode and a fourth operating mode; based on the operating mode of the DC networking, the corresponding control method and starting method are determined to complete the operation of the hybrid DC system. The technical solution of the present invention provides a new DC networking method suitable for certain large-scale renewable energy transmission scenarios, improves the ability of large-scale renewable energy transmission through DC, and reduces the operating cost and loss of the DC system. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] A more complete understanding of exemplary embodiments of the present invention may be obtained by referring to the following drawings:

[0094] Figure 1 A flow chart of a control method based on multi-terminal hybrid DC networking according to a preferred embodiment of the present invention;

[0095] Figure 2 1 is a system structure diagram of a multi-terminal hybrid DC networking method according to a preferred embodiment of the present invention.

[0096] Figure 3It is a structural diagram of a sending-end MMC according to a preferred embodiment of the present invention;

[0097] Figure 4 It is a structural diagram of a sending-end / receiving-end LCC bipolar single 12-pulse wiring mode according to a preferred embodiment of the present invention;

[0098] Figure 5 It is a wiring diagram of operation mode 1 according to a preferred embodiment of the present invention;

[0099] Figure 6 This is a wiring diagram of operation mode 2 according to a preferred embodiment of the present invention;

[0100] Figure 7 This is a wiring diagram of operation mode 3 according to a preferred embodiment of the present invention;

[0101] Figure 8 It is a wiring diagram of operation mode 4 according to a preferred embodiment of the present invention;

[0102] Fig. 9 A schematic diagram of the control of a sending-end MMC virtual synchronous machine according to a preferred embodiment of the present invention;

[0103] Fig.10 A schematic diagram of a receiving-end LCC constant DC voltage control according to a preferred embodiment of the present invention;

[0104] Fig.11 It is a schematic diagram of a constant AC voltage / constant frequency control of a sending-end MMC according to a preferred embodiment of the present invention;

[0105] Fig.12 A schematic diagram of a sending-end LCC fixed active power control according to a preferred embodiment of the present invention;

[0106] Fig.13 A flowchart of a mode 1 starting method according to a preferred embodiment of the present invention;

[0107] Fig.14 A flowchart of a mode 3 starting method according to a preferred embodiment of the present invention;

[0108] Fig.15 A flowchart of a mode 4 starting method according to a preferred embodiment of the present invention;

[0109] Fig.16 The figure is a structural diagram of a control system based on multi-terminal hybrid DC networking according to a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0110] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0111] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0112] Figure 1 The present invention is a flowchart of a control method based on multi-terminal hybrid DC networking according to a preferred embodiment of the present invention.

[0113] The present invention comprehensively utilizes the voltage support capability of flexible direct current transmission and the advantages of low cost and large capacity of conventional direct current to form a new direct current networking mode suitable for certain large-scale renewable energy transmission scenarios. The purpose is to improve the ability of large-scale renewable energy transmission through direct current and reduce the operating cost and loss of the direct current system.

[0114] like Figure 1 As shown, the present invention provides a control method based on multi-terminal hybrid DC networking, the method:

[0115] Step 101: Determine a multi-terminal hybrid DC network, wherein: the AC sides of the sending-end MMC and the sending-end LCC are connected to the corresponding first new energy base and second new energy base respectively, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel; the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel to the DC side of the receiving-end LCC through a DC line, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid;

[0116] Figure 2 The multi-terminal hybrid DC networking structure for large-scale renewable energy transmission proposed in the present invention is composed of a sending-end MMC, a sending-end LCC, a receiving-end LCC, a DC line, etc. Among them, the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel, and the AC sides are connected to the new energy base 1 and the new energy base 2 respectively; the receiving-end LCC is connected to the receiving-end AC power grid; the sending-end DC and the receiving-end DC are connected through a DC line. In the actual power grid, the new energy base 1 connected to the sending-end MMC can operate in an isolated island or be connected to the sending-end AC power grid, and the new energy base 2 needs to be connected to the sending-end AC power grid.

[0117] The sending-end MMC of the present invention adopts a bipolar wiring method, including a commutation bus, a commutation transformer, a half-bridge MMC converter, a pole line reactor, a neutral line reactor, an AC starting resistor, a DC starting resistor and a grounding electrode system, etc. The structure is as follows: Figure 3 The sending-end LCC and the receiving-end LCC have the same structure and adopt a bipolar connection method, including a commutation bus, a commutation transformer, an LCC converter, an AC filter, a DC filter, a smoothing reactor, and a grounding electrode system. The converter can adopt a bipolar single 12-pulse connection method or a bipolar double 12-pulse connection method according to different voltage levels. The LCC structure of the bipolar single 12-pulse connection method is shown in the figure. Figure 4 shown.

[0118] The capacity of the receiving-end LCC of the present invention is equal to the sum of the capacities of the sending-end MMC and LCC, that is, the total capacity of the DC system. At the same time, the capacity of the sending-end MMC and LCC needs to match the capacity of the new energy to be sent, so as to ensure that the new energy output can still be sent to the receiving-end AC power grid through the DC system when it reaches the maximum.

[0119] Step 102: Based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, determine the operation mode of the DC network; wherein the connection state includes: connection and disconnection; the operation state includes: start and stop; the operation model includes: the first operation mode, the second operation mode, the third operation mode and the fourth operation mode;

[0120] Step 103: Based on the operation mode of the DC network, a corresponding control method and a starting method are determined to complete the transmission of DC.

[0121] Preferably, the operation mode of the DC network is determined based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, and the first operation mode is:

[0122] The first new energy base is connected to the sending-end AC power grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is in an exited operation state;

[0123] The second operating mode is:

[0124] The second new energy base is connected to the sending-end AC power grid, the sending-end MMC is in the exited operation state, and the sending-end LCC and the receiving-end LCC are in the operating state;

[0125] The third operating mode is:

[0126] The first new energy base operates in an isolated island, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, sending-end LCC and receiving-end LCC are in operation;

[0127] The fourth operating mode is:

[0128] The first new energy base is connected to the sending-end AC power grid, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation.

[0129] The DC networking method of the present invention has four operation modes according to whether the sending-end new energy base 1 is connected to the sending-end AC power grid, and whether the sending-end MMC and the sending-end LCC are put into operation.

[0130] Figure 5 This is the wiring diagram for operation mode 1, where the new energy base 1 is connected to the AC grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is out of operation. In this mode, the sending-end new energy base 1 can be sent through the sending-end MMC and the receiving-end LCC.

[0131] Figure 6 This is the wiring diagram for operation mode 2, the sending-end MMC is out of operation, and the sending-end LCC and the receiving-end LCC are in operation. In this mode, the sending-end new energy base 2 can be sent through the sending-end LCC and the receiving-end LCC.

[0132] Figure 7 This is the wiring diagram for operation mode 3. The sending-end new energy base 1 is operating in an isolated manner, and both the sending-end and receiving-end DC are in operation. In this mode, the sending-end new energy base 1 can be sent through the sending-end MMC, and the new energy base 2 can be sent through the sending-end LCC.

[0133] Figure 8 This is the wiring diagram for operation mode 4, where the sending-end new energy base 1 is connected to the sending-end AC grid, and both the sending-end and receiving-end DC are in operation. In this mode, the sending-end new energy can be sent out through the hybrid DC system.

[0134] Preferably, based on the operation mode of the DC network, the corresponding control method and starting method are determined, wherein the first control method of the first operation mode is:

[0135] The sending-end MMC uses virtual synchronous machine, reactive loop, voltage loop and current loop for control;

[0136] The receiving end LCC adopts constant DC voltage control.

[0137] Preferably, based on the operation mode of the DC network, the corresponding control method and starting method are determined, wherein the third control method of the third operation mode is:

[0138] The sending-end MMC adopts a constant AC voltage and constant frequency control mode, which includes a voltage loop and a current loop;

[0139] The sending-end LCC adopts fixed active power or fixed DC current control;

[0140] The receiving end LCC adopts constant DC voltage control.

[0141] Preferably, based on the operation mode of the DC network, the corresponding control method and starting method are determined, wherein the fourth control method of the fourth operation mode is:

[0142] The sending-end MMC uses virtual synchronous machine, reactive loop, voltage loop and current loop for control;

[0143] The sending-end LCC adopts fixed active power or fixed DC current control;

[0144] The receiving end LCC adopts constant DC voltage control.

[0145] Preferably, based on the operation mode of the DC network, the corresponding control method and starting method are determined, wherein the first starting method of the first operation mode is:

[0146] Uncontrollably charge the MMC at the sending end;

[0147] Controllable charging of the sending-end MMC;

[0148] Unlock the LCC at the receiving end;

[0149] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0150] Preferably, based on the operation mode of the DC network, the corresponding control method and starting method are determined, wherein the starting method of the third operation mode is:

[0151] Start the sending-end LCC and the receiving-end LCC;

[0152] Uncontrollably charge the MMC at the sending end;

[0153] Controllable charging of the sending-end MMC;

[0154] Switch the control strategy of the sending-end MMC to constant AC voltage and constant frequency control;

[0155] The first new energy base was connected to the grid.

[0156] Preferably, based on the operation mode of the DC network, the corresponding control method and starting method are determined, wherein the starting method of the fourth operation mode is:

[0157] Start the sending-end LCC and the receiving-end LCC;

[0158] Uncontrollably charge the MMC at the sending end;

[0159] Controllable charging of the sending-end MMC;

[0160] Make DC side connections to the sending-end MMC;

[0161] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0162] The present invention performs steady-state control of a DC networking mode, including:

[0163] 1) Mode 1 Steady-state Control Method

[0164] In mode 1, the new energy base 1 is connected to the AC power grid, and the sending-end MMC adopts virtual synchronous machine control to improve the inertia support and voltage support capabilities of the sending-end power grid. The virtual synchronous machine control consists of four parts, namely the virtual synchronous machine, reactive loop, voltage loop and current loop. The control frame is as follows Fig. 9 shown.

[0165] Among them, P ref and P are the reference and measured values ​​of active power, ω0 and ω are the rated and reference values ​​of angular frequency, θ is the phase reference value, J is the moment of inertia, D is the damping coefficient, Q ref and Q are the reactive power reference and measured values, U ref is the AC voltage amplitude reference value, u sdref 、u sd is the grid d-axis voltage reference value and measured value, u sqref 、u sq is the grid q-axis voltage reference value and measured value, i dref 、i d is the d-axis current reference value and measured value, i qref 、i q is the reference value and measured value of the q-axis current (the current flowing into the converter is positive), u vdr 、u vqr are the d-axis reference value and q-axis reference value of the converter output voltage, and L is the leakage inductance of the commutation transformer.

[0166] Since the system active power is determined by the sending end, the receiving end LCC is mainly responsible for controlling the stability of the DC voltage. It adopts typical constant DC voltage control. The control frame is as follows: Fig.10 shown.

[0167] Among them, U dc2 is the measured value of the DC voltage at the receiving end, U dcref is the reference value of the DC voltage at the sending end, I dc2 is the measured value of the DC current at the receiving end, R line is the DC line resistance, and γ is the turn-off angle reference value.

[0168] 2) Mode 2 Steady-state Control Method

[0169] Mode 2 is LCC end-to-end DC, which can adopt existing mature control methods without designing special control strategies.

[0170] 3) Mode 3 Steady-state Control Method

[0171] In mode 3, the new energy base 1 operates in an isolated island and requires AC voltage support. Therefore, the sending-end MMC needs to be responsible for providing the isolated new energy AC voltage. Here, a typical constant AC voltage / constant frequency (V / f) control method is adopted. The control box is as follows: Fig.11 shown.

[0172] The sending-end MMC constant AC voltage / constant frequency control of the present invention includes a voltage loop and a current loop, which are the same as the voltage loop and current loop of the virtual synchronous machine control. Here, the angular frequency reference value ω=2πf, and f is the power frequency 50Hz.

[0173] Mode 3 The sending-end LCC adopts fixed active power or fixed DC current control, where the fixed active power control frame is as follows Fig.12 shown.

[0174] Among them, P LCCref is the reference value of the sending-end LCC active power, U dc1 is the DC voltage measurement value at the sending end, I LCC ,I LCCref is the measured value and reference value of the LCC DC side current (the current flowing from the sending end to the receiving end is positive), and α is the reference value of the LCC trigger angle.

[0175] The receiving-end LCC adopts constant DC voltage control, which is the same as mode 1.

[0176] 4) Mode 4 Steady-state Control Method

[0177] In mode 4, the new energy base 1 is connected to the AC power grid, and the sending-end MMC adopts virtual synchronous machine control, which is the same as mode 1.

[0178] The sending-end LCC adopts constant active power or constant DC current control, which is the same as mode 3.

[0179] The receiving-end LCC adopts constant DC voltage control, which is the same as mode 1.

[0180] (3) Starting method of DC network

[0181] The starting method of the new DC networking mode needs to be designed according to different operating modes. Mode 2 is LCC end-to-end DC, which can adopt the existing mature starting method without special design.

[0182] For mode 1, when the new energy base 1 is connected to the grid, the sending-end MMC can be charged through the AC side first, and then the DC power transmission is started. The specific steps are as follows:

[0183] 1) Uncontrolled charging of the MMC at the sending end: When the AC circuit breaker is closed, the AC grid charges the submodule capacitor, the starting resistor suppresses overcurrent during the charging process, and the submodule capacitor voltage rises to U p-p / N, where U p-p is the peak value of the AC line voltage at the sending end, N is the total number of MMC single bridge arm submodules, and then the bypass AC starting resistor.

[0184] 2) MMC controllable charging at the sending end: unlock the converter, put the MMC into constant DC voltage control, and set the reference value to the DC voltage reference value U dcref , the DC side voltage rises to U dcref , the submodule capacitor voltage reaches U dcref / N.

[0185] 3) Receiving end LCC unlocking: The receiving end LCC is unlocked and controlled by constant DC voltage.

[0186] 4) Switching of control strategy of MMC at the sending end: The MMC at the sending end quickly switches the control strategy to virtual synchronous machine control to transmit the minimum DC current. After that, the new energy base 1 at the sending end is started and the DC power transmission power is increased accordingly. The new energy output is sent to the receiving power grid.

[0187] Mode 1 start control method flow is as follows Fig.13 shown.

[0188] For mode 3, the new energy base 1 operates in an isolated island. It is necessary to start the LCC at both ends first, and then start the MMC at the sending end. The specific steps are as follows:

[0189] 1) Starting of LCC at the sending and receiving end: The LCC starting method adopts the conventional LCC DC starting method. After the receiving end is unlocked, the sending end is unlocked, the DC voltage is established, and the minimum DC current is transmitted. After that, according to the grid operation requirements, the LCC sending end new energy base 2 can be started and the LCC power transmission power can be increased accordingly. The power of the new energy base 2 is transmitted from the sending end LCC to the receiving end LCC.

[0190] 2) Uncontrolled charging of the MMC at the sending end: When the DC circuit breaker is closed, the DC line charges the submodule capacitor, and the DC starting resistor suppresses overcurrent during the charging process until the submodule capacitor voltage rises to U dc1 / 2N, where U dc1 is the DC voltage at the sending end.

[0191] 3) Controllable charging of MMC at the sending end: The MMC submodules continue to charge through the DC side using the active charging method, unlock the MMC by putting all submodules into use, adjust the number of submodules put into use in each bridge arm to N / 2, and at the same time ensure that the capacitor voltage of the submodules in a single bridge arm is consistent through the voltage balancing strategy until the capacitor voltage of each submodule reaches U dc1 / N, then bypass the DC starting resistor.

[0192] 4) Switching of MMC control strategy at the sending end: After active charging is completed, the MMC control strategy switches to V / f control to establish the AC voltage on the new energy side.

[0193] 5) Grid-connected operation of isolated island renewable energy: Start the isolated island renewable energy base 1 connected to the sending-end MMC, and the isolated island renewable energy will send power through the sending-end MMC-receiving-end LCC.

[0194] Mode 3 start control method flow is as follows Fig.14 shown.

[0195] For mode 4, the new energy base 1 is connected to the network and the specific starting steps are as follows:

[0196] 1) Starting of LCC at the sending and receiving end: The LCC starting method adopts the conventional LCC DC starting method. After the receiving end is unlocked, the sending end is unlocked, the DC voltage is established, and the minimum DC current is transmitted. After that, according to the grid operation requirements, the LCC sending end new energy base 2 can be started and the LCC power transmission power can be increased accordingly. The power of the new energy base 2 is transmitted from the sending end LCC to the receiving end LCC.

[0197] 2) Uncontrolled charging of the MMC at the sending end: When the AC circuit breaker is closed, the AC grid charges the submodule capacitor, and the AC starting resistor suppresses overcurrent during the charging process until the submodule capacitor voltage rises to U p-p / N, then bypass the AC starting resistor.

[0198] 3) MMC controllable charging at the sending end: unlock the converter, put the MMC into fixed DC voltage control, and the DC voltage reference value is the DC voltage measurement value U at the sending end dc1 , the DC side voltage rises to U dc1 , the submodule capacitor voltage reaches U dc1 / N.

[0199] 4) Connection of MMC DC side at the sending end: The DC circuit breaker at the MMC DC side outlet is closed, and the MMC DC side and LCC operate in parallel.

[0200] 5) Switching of control strategy of MMC at the sending end: The MMC fixed DC voltage control is switched to virtual synchronous machine control. After that, the sending-end new energy base 1 can be started according to the grid operation requirements, and the MMC DC power transmission power can be increased accordingly. The power of the new energy base 1 is transmitted from the sending-end MMC to the receiving-end LCC.

[0201] Mode 4 start control method flow is as follows Fig.15 shown.

[0202] The present invention provides a multi-terminal hybrid DC networking mode for large-scale renewable energy transmission. The sending end is LCC and MMC in parallel. The LCC at the sending end can transmit renewable energy with voltage support, and the MMC can transmit isolated renewable energy or improve the inertia and voltage support capacity of the power grid at the sending end. The two transmit the renewable energy power to the receiving end through a DC line, and the LCC at the receiving end is used to control the DC voltage.

[0203] At the same time, the present invention provides a control method for the proposed DC networking mode, and its steady-state control method can ensure the stable delivery of new energy output, and the system starting method can start LCC, MMC and new energy units in an orderly manner to ensure the normal establishment of active power transmission of new energy and hybrid DC systems, and finally enable the system to enter stable operation.

[0204] The DC networking method of the present invention can fully utilize the advantages of MMC and LCC, provide a feasible solution for large-scale renewable energy transmission scenarios, improve the ability of the DC system to transmit large-scale renewable energy, and reduce investment costs and operating losses.

[0205] The multi-terminal hybrid DC networking method for large-scale renewable energy transmission proposed in the present invention includes a sending-end MMC, a sending-end LCC, a receiving-end LCC, a DC line, and other equipment. According to the renewable energy connection method and whether the sending-end DC is put into operation, the DC networking method has four operating modes.

[0206] The multi-terminal hybrid DC networking control method for large-scale renewable energy transmission proposed in the present invention is designed for different operation modes, including a steady-state control method and a starting method.

[0207] Fig.16 The figure is a structural diagram of a control system based on multi-terminal hybrid DC networking according to a preferred embodiment of the present invention.

[0208] like Fig.16 As shown, the present invention provides a control system based on multi-terminal hybrid DC networking, the system:

[0209] The first networking unit 1601 is used to connect the AC sides of the sending-end MMC and the sending-end LCC to the corresponding first new energy base and the second new energy base respectively, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel;

[0210] The second networking unit 1602 is used for connecting the DC sides of the sending-end MMC and the sending-end LCC in parallel and then connecting them to the DC side of the receiving-end LCC through a DC line, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid;

[0211] The determining unit 1603 is used to determine the operation mode of the DC network based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC; wherein the connection state includes: connected and disconnected; the operation state includes: started and disabled; the operation model includes: a first operation mode, a second operation mode, a third operation mode and a fourth operation mode;

[0212] Preferably, the determining unit 1603 is used to determine the operation mode of the DC network based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, and the first operation mode is:

[0213] The first new energy base is connected to the sending-end AC grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is out of operation;

[0214] The second operating mode is:

[0215] The second new energy base is connected to the sending-end AC power grid, the sending-end MMC is in the exited operation state, and the sending-end LCC and the receiving-end LCC are in the operating state;

[0216] The third operating mode is:

[0217] The first new energy base operates in an isolated island, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, sending-end LCC and receiving-end LCC are in operation;

[0218] The fourth operating mode is:

[0219] The first new energy base is connected to the sending-end AC power grid, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation.

[0220] The result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network to complete the transmission of DC.

[0221] Preferably, the result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the first control method of the first operation mode is:

[0222] The sending-end MMC uses virtual synchronous machine, reactive loop, voltage loop and current loop for control;

[0223] The receiving end LCC adopts constant DC voltage control.

[0224] Preferably, the result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the third control method of the third operation mode is:

[0225] The sending-end MMC adopts a constant AC voltage and constant frequency control mode, which includes a voltage loop and a current loop.

[0226] The sending-end LCC adopts fixed active power or fixed DC current control;

[0227] The receiving end LCC adopts constant DC voltage control.

[0228] Preferably, the result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the fourth control method of the fourth operation mode is:

[0229] The sending-end MMC uses virtual synchronous machine, reactive loop, voltage loop and current loop for control;

[0230] The sending-end LCC adopts fixed active power or fixed DC current control;

[0231] The receiving end LCC adopts constant DC voltage control.

[0232] Preferably, the result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the first starting method of the first operation mode is:

[0233] Uncontrollably charge the MMC at the sending end;

[0234] Controllable charging of the sending-end MMC;

[0235] Unlock the LCC at the receiving end;

[0236] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0237] Preferably, the result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the starting method of the third operation mode is:

[0238] Start the sending-end LCC and the receiving-end LCC;

[0239] Uncontrollably charge the MMC at the sending end;

[0240] Controllable charging of the sending-end MMC;

[0241] Switch the control strategy of the sending-end MMC to constant AC voltage and constant frequency control;

[0242] The first new energy base was connected to the grid for operation.

[0243] Preferably, the result unit 1604 is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the starting method of the fourth operation mode is:

[0244] Start the sending-end LCC and the receiving-end LCC;

[0245] Uncontrollably charge the MMC at the sending end;

[0246] Controllable charging of the sending-end MMC;

[0247] Make DC side connections to the sending-end MMC;

[0248] The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

[0249] A multi-terminal hybrid DC networking and control system according to a preferred embodiment of the present invention corresponds to a control method based on a multi-terminal hybrid DC networking according to another preferred embodiment of the present invention, and will not be described in detail here.

[0250] The present invention provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and the computer program is used to execute a control method based on multi-terminal hybrid DC networking.

[0251] The present invention provides an electronic device, the electronic device comprising: a processor and a memory; wherein:

[0252] Memory, a memory for storing processor executable instructions;

[0253] The processor is used to read executable instructions from the memory and execute the instructions to implement a multi-terminal hybrid DC networking and control method.

[0254] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0255] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0256] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0257] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0258] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0259] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0260] The invention has been described above with reference to a few embodiments. However, it is readily apparent to a person skilled in the art that other embodiments than the ones disclosed above are equally within the scope of the invention, as defined by the appended patent claims.

[0261] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / / the [means, component, etc.]" are to be openly interpreted as at least one instance of a means, component, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not necessarily have to be performed in the exact order disclosed, unless explicitly stated otherwise.

Claims

1. A control method based on multi-terminal hybrid DC networking, the method comprising: Determine a multi-terminal hybrid DC network, wherein: the AC sides of the sending-end MMC and the sending-end LCC are respectively connected to the corresponding first new energy base and second new energy base, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel; the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel to the DC side of the receiving-end LCC through a DC line, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid; Based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, the operation mode of the DC network is determined; wherein the connection state includes: connection and disconnection; the operation state includes: start and stop; the operation model includes: a first operation mode, a second operation mode, a third operation mode and a fourth operation mode; Based on the operation mode of the DC network, the corresponding control method and starting method are determined to complete the operation of the hybrid DC system.

2. The method according to claim 1, wherein the operation mode of the DC network is determined based on the connection state of the first new energy base connected to the sending-end MMC, and the operation states of the sending-end MMC and the sending-end LCC, and the first operation mode is: The first new energy base is connected to the sending-end AC power grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is in an exited operation state; The second operating mode is: The second new energy base is connected to the sending-end AC power grid, the sending-end MMC is in an exited operation state, and the sending-end LCC and the receiving-end LCC are in an operating state; The third operating mode is: The first new energy base operates in an isolated island, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation; The fourth operating mode is: The first new energy base is connected to the sending-end AC power grid, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation.

3. The method according to claim 2, wherein the operation mode based on the DC network determines the corresponding control method and starting method, wherein the first control method of the first operation mode is: The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop; The receiving-end LCC adopts constant DC voltage control.

4. The method according to claim 2, wherein the operation mode based on the DC network determines the corresponding control method and starting method, wherein the third control method of the third operation mode is: The sending-end MMC adopts a constant AC voltage and a constant frequency control mode, and the constant AC voltage and a constant frequency control mode includes a voltage loop and a current loop; The sending-end LCC adopts fixed active power or fixed DC current control; The receiving-end LCC adopts constant DC voltage control.

5. According to the method of claim 1, the operation mode based on the DC network determines the corresponding control method and starting method, wherein the fourth control method of the fourth operation mode is: The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop; The sending-end LCC adopts fixed active power or fixed DC current control; The receiving-end LCC adopts constant DC voltage control.

6. The method according to claim 2, wherein the operation mode based on the DC network determines the corresponding control method and starting method, wherein the first starting method of the first operation mode is: Performing uncontrollable charging on the sending-end MMC; Controllably charging the sending-end MMC; Unlocking the receiving-end LCC; The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

7. The method according to claim 2, wherein the operation mode based on the DC network determines the corresponding control method and starting method, wherein the starting method of the third operation mode is: Starting the sending-end LCC and the receiving-end LCC; Performing uncontrollable charging on the sending-end MMC; Controllably charging the sending-end MMC; Switching the control strategy of the sending-end MMC to constant AC voltage and constant frequency control; The first new energy base is connected to the grid for operation.

8. The method according to claim 2, wherein the operation mode based on the DC network determines the corresponding control method and starting method, wherein the starting method of the fourth operation mode is: Starting the sending-end LCC and the receiving-end LCC; Performing uncontrollable charging on the sending-end MMC; Controllably charging the sending-end MMC; Connecting the sending-end MMC to the DC side; The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

9. A control system based on multi-terminal hybrid DC networking, the system comprising: A first networking unit, used for connecting the AC sides of the sending-end MMC and the sending-end LCC to the corresponding first new energy base and the second new energy base respectively, and the DC sides of the sending-end MMC and the sending-end LCC are connected in parallel; A second networking unit is used for connecting the DC sides of the sending-end MMC and the sending-end LCC in parallel and then connecting them to the DC side of the receiving-end LCC through a DC line, and the AC side of the receiving-end LCC is connected to the receiving-end AC power grid; A determination unit, configured to determine an operation mode of the DC network based on a connection state of a first new energy base connected to the sending-end MMC, and an operation state of the sending-end MMC and the sending-end LCC; wherein the connection state includes: connected and disconnected; the operation state includes: started and disabled; the operation model includes: a first operation mode, a second operation mode, a third operation mode, and a fourth operation mode; The result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network to complete the operation of the hybrid DC system.

10. The system according to claim 9, wherein the determining unit is configured to determine the operation mode of the DC network based on the connection state of the first new energy base connected to the sending-end MMC and the operation states of the sending-end MMC and the sending-end LCC, wherein the first operation mode is: The first new energy base is connected to the sending-end AC power grid, the sending-end MMC and the receiving-end LCC are in operation, and the sending-end LCC is in an exited operation state; The second operating mode is: The second new energy base is connected to the sending-end AC power grid, the sending-end MMC is in an exited operation state, and the sending-end LCC and the receiving-end LCC are in an operating state; The third operating mode is: The first new energy base operates in an isolated island, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation; The fourth operating mode is: The first new energy base is connected to the sending-end AC power grid, the second new energy base is connected to the sending-end AC power grid, and the sending-end MMC, the sending-end LCC and the receiving-end LCC are in operation.

11. The system according to claim 10, wherein the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the first control method of the first operation mode is: The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop; The receiving-end LCC adopts constant DC voltage control.

12. The system according to claim 10, wherein the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the third control method of the third operation mode is: The sending-end MMC adopts a constant AC voltage and a constant frequency control mode, and the constant AC voltage and a constant frequency control mode includes a voltage loop and a current loop; The sending-end LCC adopts fixed active power or fixed DC current control; The receiving-end LCC adopts constant DC voltage control.

13. The system according to claim 10, wherein the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the fourth control method of the fourth operation mode is: The sending-end MMC is controlled by a virtual synchronous machine, a reactive loop, a voltage loop and a current loop; The sending-end LCC adopts fixed active power or fixed DC current control; The receiving-end LCC adopts constant DC voltage control.

14. The system according to claim 10, wherein the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the first starting method of the first operation mode is: Performing uncontrollable charging on the sending-end MMC; Controllably charging the sending-end MMC; Unlocking the receiving-end LCC; The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

15. The system according to claim 10, wherein the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the starting method of the third operation mode is: Starting the sending-end LCC and the receiving-end LCC; Performing uncontrollable charging on the sending-end MMC; Controllably charging the sending-end MMC; Switching the control strategy of the sending-end MMC to constant AC voltage and constant frequency control; The first new energy base is connected to the grid for operation.

16. The system according to claim 10, wherein the result unit is used to determine the corresponding control method and starting method based on the operation mode of the DC network, wherein the starting method of the fourth operation mode is: Starting the sending-end LCC and the receiving-end LCC; Performing uncontrollable charging on the sending-end MMC; Controllably charging the sending-end MMC; Connecting the sending-end MMC to the DC side; The control strategy of the sending-end MMC is switched to virtual synchronous machine control.

17. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program is used to execute the method according to any one of claims 1 to 8.

18. An electronic device, characterized in that: The electronic device comprises: a processor and a memory; wherein, The memory is a memory for storing instructions executable by the processor; The processor is configured to read the executable instructions from the memory and execute the instructions to implement the method according to any one of claims 1 to 8.

Images