Electrical wiring system of offshore wind and light same-field power station based on direct-current power grid and control method of electrical wiring system

Abstract

The invention discloses an electrical wiring system for offshore wind-light same-field power stations based on a direct-current power grid and a control method of the electrical wiring system, and belongs to the field of offshore wind-light same-field power generation. The electrical wiring system comprises a plurality of distributed offshore wind-light same-field power stations which are consistent in structure and are connected in series, and each offshore wind-light same-field power station comprises an offshore direct-current switching station; two sections of parallel buses are arranged in the offshore direct current switching station, an offshore wind power generation system is connected to the two sections of buses through a fan rectifier, an offshore photovoltaic power generation system is connected to the two sections of buses through a string type photovoltaic DC / DC converter to serve as input, and an alternating current power grid system is connected to the two sections of buses through an onshore converter station to serve as output. The distributed offshore wind and light same-field power stations are connected through bus section switches, and different control strategies are adopted according to different working conditions. The operation reliability of the offshore wind and light same-field power station and the convenience of construction installation and equipment overhaul and maintenance are improved, meanwhile, the engineering cost is saved, and engineering application and popularization are facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of offshore wind and solar power generation, in particular to an offshore wind and solar power plant electrical connection system based on a DC power grid and a control method thereof. BACKGROUND

[0002] Offshore wind and solar resources are extremely abundant: compared with land, offshore wind speed is large and wind conditions are good; offshore photovoltaic has the characteristics of high power generation and easy combination with other industries; and offshore power generation, especially deep-sea power generation, is far away from human activity space and has little impact on human life.

[0003] The electrical connection system is a core component of the offshore wind and solar power plant, and is directly related to whether the power plant can operate safely, reliably and efficiently. At present, offshore wind and solar power plants mostly use power frequency AC power grid as the core of power transmission, and the grid connection mode is mainly through the setting of offshore booster stations to collect the power generated by offshore wind and solar power, and then transmit it to the land control center through the main transformer for grid connection. Although this technical route has relatively simple connection structure, mature technology and rich engineering experience, it has significant limitations: limited by cable charging current and charging power, the power transmission distance is limited, and the higher the voltage level, the greater the charging current; as the distance of the power plant from the shore increases and the scale continues to expand, in order to solve the influence of the charging capacity of the sea cable, the point-to-point scheme needs to be used for sending and grid connection, that is, the power is rectified to DC through the offshore flexible HVDC station and then transmitted to the land, and then converted to AC to access the grid, the process is more complex.

[0004] More importantly, the AC transmission network structure is originally mainly based on the construction of traditional large power sources, and as the scale of offshore new energy continues to expand, the original AC transmission network gradually tends to saturation in terms of consumption capacity, and the grid needs to be upgraded and reconstructed with huge investment. At the same time, the inherent randomness and volatility of new energy make the grid connection control and grid stability face great challenges when large-scale new energy uses the existing grid connection scheme. These problems not only restrict the large-scale development of offshore wind and solar power plants, but also affect the economy and reliability of the operation of the power plant, and an electrical connection system and control method that adapts to the characteristics of offshore wind and solar power and meets the demand for long-distance and large-capacity transmission are needed to break through the existing technical bottlenecks. SUMMARY

[0005] The technical problem to be solved by the present application is to provide an offshore wind and solar power plant electrical connection system based on a DC power grid and a control method thereof. The purpose is to solve the problem of connecting new energy power generation to the existing system without the need for large-scale upgrading and reconstruction of the original grid system, which not only improves the reliability of the operation of the offshore wind and solar power plant, the convenience of construction, installation and equipment maintenance, but also saves engineering cost and facilitates engineering application and promotion.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an electrical wiring system for an offshore wind and solar co-station based on a DC grid, comprising multiple distributed offshore wind and solar co-stations with identical structures connected in series. Each offshore wind and solar co-station includes an offshore DC switch station, which is equipped with two parallel busbars. The two busbars are connected to an offshore wind power generation system via a wind turbine rectifier, and an offshore photovoltaic power generation system is connected to the system via a string photovoltaic DC / DC converter as input. The two busbars are connected to the AC grid system via an onshore converter station as output. The distributed offshore wind and solar co-stations are connected to each other via busbar sectionalizing switches.

[0007] A further improvement of the technical solution of the present invention is that: the offshore DC switch station is equipped with a DC power distribution device, and the station load of the offshore DC switch station is powered by a DC / AC inverter.

[0008] A further improvement of the technical solution of the present invention is that a battery energy storage system is also installed on the offshore wind and solar power station. The battery energy storage system is connected to two bus sections through an energy storage DC / DC converter. The battery energy storage system includes a battery energy storage unit, an energy management system, and a measurement and protection unit.

[0009] A further improvement of the technical solution of the present invention is that: the offshore wind power generation system includes a wind turbine generator, a frequency converter and a wind turbine monitoring and protection device; the offshore photovoltaic power generation system includes a photovoltaic cell module, a DC combiner device and a photovoltaic local monitoring device.

[0010] A control method for the electrical wiring system of an offshore wind-solar co-station based on a DC grid is proposed. This method employs a three-layer collaborative control strategy: "normal operation—minor fault support—major fault self-healing." Through hierarchical optimization of the objective function and constraints, it achieves optimal power balance under normal operating conditions; priority reactive power support and DC voltage stability under minor faults; and converter station blocking, energy storage takeover, and power flow self-healing under major faults. The specific steps are as follows:

[0011] Step 1: Determine the status of the AC power grid system to which the electrical wiring system of the offshore wind and solar co-current power station based on the DC grid is connected, and use different control strategies according to different statuses;

[0012] Step 2: When the AC power grid system is in normal operating condition, the offshore wind power system and the offshore photovoltaic power system shall operate according to MPPT respectively;

[0013] Step 3: When the AC power grid system is in a fault condition, further determine whether the fault is a minor fault condition or a major fault condition.

[0014] Step 4: When the AC power grid system is under minor fault conditions, the onshore converter station of the offshore wind and solar co-current power station based on the DC power grid operates in the converter station adaptive STATCOM mode.

[0015] Step 5: When the AC power grid system is under severe fault conditions, the electrical wiring system of the offshore wind and solar co-location power station based on the DC power grid will operate in the mode of onshore converter station lockout + battery energy storage system takeover + DC power flow redistribution to achieve system self-healing.

[0016] A further improvement to the technical solution of this invention lies in the following steps: Step 2 specifically involves the following steps: Under normal conditions of the AC power grid system, the offshore wind-solar co-generation power station transmits power bidirectionally to the power grid through an onshore converter station. Each station in the system actively optimizes power flow allocation, dynamically satisfying multiple objective optimizations.

[0017]

[0018] in Indicates system transmission efficiency. This indicates the voltage of the offshore DC bus. Describe the target voltage of the DC bus;

[0019] According to the dynamic energy conservation of the DC bus, we have:

[0020]

[0021] in This represents the equivalent capacitance of the DC bus. This represents the total instantaneous active power of offshore wind / solar power connected to the DC grid. This indicates that the DC-side energy storage output power is positive when discharging and negative when charging;

[0022] The state equation of the energy storage system is:

[0023]

[0024] in Indicates the battery's state of charge. Indicates the rated energy of the energy storage. Indicates the charging efficiency of the energy storage system. Indicates the discharge efficiency of the energy storage system;

[0025] in, ;when At that time, energy storage system ;

[0026] Under stable operating conditions, the following applies: .

[0027] in, This represents the active power sent to or absorbed from the AC side by the k-th station. Active power is defined in the positive direction.

[0028] Among them, offshore wind power generation systems and offshore photovoltaic power generation systems are operated according to MPPT;

[0029] The onshore converter station operates in constant DC voltage mode to provide DC bus voltage support for the offshore DC power grid;

[0030] Battery energy storage system control strategy tracking ,Right now: ;

[0031] For each onshore converter station k that has not entered the STATCOM / lockdown state, its control adopts voltage and current control. Under this control strategy, the current command is: ;in , , Indicates control parameters;

[0032] When the battery storage system is fully charged, that is, Offshore wind power systems and offshore photovoltaic power systems transmit electrical energy to the grid through onshore converter stations, that is, ;

[0033] in Indicates loss.

[0034] A further improvement to the technical solution of the present invention is as follows: Step 3 is specifically as follows:

[0035] Voltage sag is measured by measuring the amplitude of AC bus voltage. and duration of the fault This is used to determine the severity of the fault, that is:

[0036] and This is considered a minor fault condition.

[0037] or This is considered a serious fault condition; among them This represents the per-unit voltage amplitude of the corresponding AC bus; the value measured during a fault is recorded as follows. , Indicates the duration of the fault.

[0038] A further improvement to the technical solution of the present invention is as follows: Step 4 is specifically as follows:

[0039] The adaptive STATCOM mode of the converter station can be represented as follows:

[0040]

[0041] in This represents the reactive power injection at station k, which is the main quantity under STATCOM mode;

[0042] The operation strategy for onshore converter stations is as follows:

[0043] Step 4.1: Switch the running mode to STATCOM running mode;

[0044] Step 4.2: Active power output satisfies: And consider prioritizing the needs of reactive power support;

[0045] Step 4.3: Adopt a reactive power control strategy. And it should satisfy the current constraint condition:

[0046] ,

[0047] Step 4.4: Other onshore converter stations continue to use constant DC voltage mode control, with energy storage systems participating in DC voltage support.

[0048] ,

[0049] Step 4.5: After the fault is cleared, the onshore converter station related to the faulty AC grid exits STATCOM operation mode and gradually restores active power according to the active power recovery slope. To avoid impacting the AC power grid and ultimately achieve the expected active power value: , .

[0050] A further improvement to the technical solution of the present invention is as follows: Step 5 is specifically as follows:

[0051] Under severe fault conditions, the operating mode of converter station shutdown + battery energy storage system takeover + DC power flow redistribution is expressed as:

[0052]

[0053] The specific operation method is as follows:

[0054] Step 5.1: The onshore converter station k associated with the faulty AC power grid is locked out;

[0055] Step 5.2: Other onshore converter stations continue to use constant DC voltage mode control to support the main DC bus voltage;

[0056] Step 5.3: Offshore wind power systems and offshore photovoltaic power systems are adjusted downwards according to EMS instructions.

[0057] Step 5.4: The battery energy storage system absorbs / releases excess power to stabilize the system. :

[0058] Step 5.5: Achieve DC power balance:

[0059] Step 5.6: Fault Clearing and Grid Reconnection (Controlled Synchronization): The AC side circuit breaker of the grid-connected converter station is closed, the locked station is unlocked, and synchronization is restored according to the synchronization recovery slope. Controlling grid connection: , ;

[0060] Meanwhile, offshore wind power systems, offshore photovoltaic power systems, and battery energy storage systems gradually recovered MPPT output according to the controlled curve.

[0061] The technological advancements achieved by this invention, due to the adoption of the above-mentioned technical solutions, are as follows: By employing a DC grid scheme, DC lines do not suffer from the inductive and capacitive reactance issues of AC lines during long-distance transmission, resulting in higher transmission efficiency. Furthermore, the DC system eliminates frequency issues, avoiding stability challenges caused by frequency fluctuations. The voltage of the DC grid can be precisely controlled through rectifiers, converters, and other equipment, maximizing system stability. Simultaneously, precise control of the DC grid through rectifiers, converters, and other equipment allows for maximum grid-connected control, further enhancing system stability. By configuring a battery energy storage system, system power quality can be improved, fluctuations can be smoothed, power output can be stabilized, and peak shaving can be participated in to improve system power supply reliability. During AC grid system failures, the energy storage system absorbs excess power, maintaining DC voltage stability. Simultaneously, it provides power to critical loads during DC switchyard maintenance. By proposing a three-tiered collaborative control strategy of "normal operation—minor fault support—major fault self-healing," and through hierarchical optimization of the objective function and constraints, the following were achieved: optimal power balance under normal operating conditions; reactive power priority support and DC voltage stability under minor faults; and converter station blocking, energy storage takeover, and power flow self-healing under major faults. This effectively improves the safety, stability, and robustness of the offshore wind-solar co-current DC grid system. Attached Figure Description

[0062] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a schematic diagram of the electrical wiring system of the present invention;

[0064] The components include: 1. Offshore DC switch station; 2. Busbar; 3. Wind turbine rectifier; 4. Offshore wind power generation system; 5. String photovoltaic DC / DC converter; 6. Offshore photovoltaic power generation system; 7. Onshore converter station; 8. AC power grid system; 9. DC / AC inverter; 10. Battery energy storage system; and 11. Energy storage DC / DC converter. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to embodiments:

[0066] like Figure 1 The diagram shows a schematic of the electrical wiring system for an offshore wind-solar co-station based on a DC grid. It includes multiple distributed, interconnected offshore wind-solar co-stations with identical structures. Each offshore wind-solar co-station includes an offshore DC switch station 1, which has two parallel busbars 2. Offshore wind power generation systems 4 are connected to the two busbars 2 via wind turbine rectifiers 3, and offshore photovoltaic power generation systems are connected as inputs via string photovoltaic DC / DC converters 5. The string DC / DC converters have MPPT functionality. The two busbars 2 are connected to the AC grid system via onshore converter stations as outputs. The distributed offshore wind-solar co-stations are connected via sectionalizing switches on busbars 2. The distributed offshore DC switch stations 1 are interconnected via sectionalizing switches on busbars 2. When one section of busbar 2 fails, the faulty section can be isolated via the sectionalizing switches. The onshore converter station is based on Modular Multilevel (MMC) technology and Voltage Source Type High Voltage Direct Current (VSC-HVDC) technology. The offshore DC switch station 1 is equipped with a DC power distribution device, and the station load of the offshore DC switch station 1 is powered by a DC / AC inverter 9. The offshore wind and solar co-generation power station is also equipped with a battery energy storage system 10. By configuring the battery energy storage system 10, the power quality of the DC grid system is improved, fluctuations are smoothed, power output is stabilized, and peak shaving is participated in to improve the reliability of the system power supply. The battery energy storage system 10 is connected to two bus sections 2 through an energy storage DC / DC converter 11. The battery energy storage system 10 includes battery energy storage units, an energy management system, and a measurement and protection unit. The offshore wind power generation system 4 includes wind turbine generators, frequency converters, and wind turbine monitoring and protection devices; the offshore photovoltaic power generation system 6 includes photovoltaic modules, DC combiner devices, and local photovoltaic monitoring devices. This system adopts a DC networking scheme, which eliminates the inductive and capacitive reactance issues of AC lines during long-distance transmission, resulting in higher transmission efficiency. In addition, the DC system does not have frequency issues, avoiding the stability challenges caused by frequency fluctuations. The voltage of the DC network can be precisely controlled by rectifiers, converters, and other equipment, which can maximize the stability of the system.

[0067] A control method for the electrical wiring system of an offshore wind-solar co-station based on a DC grid is proposed. This method employs a three-layer collaborative control strategy: "normal operation—minor fault support—major fault self-healing." Through hierarchical optimization of the objective function and constraints, it achieves optimal power balance under normal operating conditions; reactive power priority support and DC voltage stability under minor faults; and converter station blocking, energy storage takeover, and power flow self-healing under major faults. The specific steps are as follows:

[0068] Step 1: Determine the status of the AC power grid system to which the electrical wiring system of the offshore wind and solar co-current power station based on the DC grid is connected, and use different control strategies according to different statuses; when a normal operating condition is detected, proceed to step 2, and when a fault is detected, proceed to step 3.

[0069] Step 2: When the AC power grid system is in normal operating condition, the offshore wind power system 4 and the offshore photovoltaic power system operate according to MPPT respectively; under normal AC power grid conditions, the offshore wind and solar power station transmits power bidirectionally to the grid through the onshore converter station. Each station in the system actively optimizes power flow distribution and dynamically meets multi-objective optimization:

[0070]

[0071] in Indicates system transmission efficiency. This indicates the voltage of the offshore DC bus 2. Describe the target voltage of DC bus 2;

[0072] According to the dynamic energy conservation of DC bus 2, we have:

[0073]

[0074] in This represents the equivalent capacitance of DC bus 2. This represents the total instantaneous active power of offshore wind / solar power connected to the DC grid. This indicates that the DC-side energy storage output power is positive when discharging and negative when charging;

[0075] The state equation of the energy storage system is:

[0076]

[0077] in Indicates the battery's state of charge. Indicates the rated energy of the energy storage. Indicates the charging efficiency of the energy storage system. Indicates the discharge efficiency of the energy storage system;

[0078] in, ;when At that time, energy storage system ;

[0079] Under stable operating conditions, the following applies: .

[0080] in, This represents the active power sent to or absorbed from the AC side by the k-th station. Active power is defined in the positive direction.

[0081] Among them: offshore wind power generation system 4 and offshore photovoltaic power generation system are operated according to MPPT;

[0082] The onshore converter station operates in constant DC voltage mode to provide DC bus 2 voltage support for the offshore DC power grid;

[0083] Battery energy storage system control strategy tracking ,Right now: ;

[0084] For each onshore converter station k that has not entered the STATCOM / lockdown state, its control adopts voltage and current control. Under this control strategy, the current command is: ;in , , Indicates control parameters;

[0085] When the battery storage system is fully charged, that is, 4. Offshore wind power generation system; offshore photovoltaic power generation system transmits electrical energy to the grid through onshore converter stations, i.e. ;

[0086] in Indicates loss.

[0087] Step 3: When the AC power grid system is in a fault condition, further determine whether the fault is a minor or major fault condition; voltage sag is measured by measuring the AC bus voltage amplitude. and duration of the fault This is used to determine the severity of the fault, that is:

[0088] and This is considered a minor fault condition.

[0089] or This is considered a serious fault condition; among them This represents the per-unit voltage amplitude of the corresponding AC bus; the value measured during a fault is recorded as follows. , Indicates the duration of the fault.

[0090] Step 4: When the AC grid system is under minor fault conditions, the onshore converter station of the offshore wind-solar co-location power station based on the DC grid operates in the converter station adaptive STATCOM mode; the converter station adaptive STATCOM mode can be represented as follows:

[0091]

[0092] in This represents the reactive power injection at station k, which is the main quantity under STATCOM mode;

[0093] The operation strategy for onshore converter stations is as follows:

[0094] Step 4.1: Switch the running mode to STATCOM running mode;

[0095] Step 4.2: Active power output satisfies: And consider prioritizing the needs of reactive power support;

[0096] Step 4.3: Adopt a reactive power control strategy. And it should satisfy the current constraint condition:

[0097] ,

[0098] Step 4.4: Other onshore converter stations continue to use constant DC voltage mode control, with energy storage systems participating in DC voltage support.

[0099] ,

[0100] Step 4.5: After the fault is cleared, the onshore converter station related to the faulty AC grid exits STATCOM operation mode and gradually restores active power according to the active power recovery slope. To avoid impacting the AC power grid and ultimately achieve the expected active power value: , .

[0101] Step 5: When the AC power grid system is under severe fault conditions, the electrical wiring system of the offshore wind-solar co-location power station based on the DC power grid operates in a mode of onshore converter station interlocking + battery energy storage system takeover + DC power flow redistribution to achieve system self-healing. The operating mode of converter station interlocking + battery energy storage system takeover + DC power flow redistribution under severe fault conditions is expressed as follows:

[0102]

[0103] The specific operation method is as follows:

[0104] Step 5.1: The onshore converter station k associated with the faulty AC power grid is locked out;

[0105] Step 5.2: Other onshore converter stations continue to use constant DC voltage mode control to support the main DC bus voltage;

[0106] Step 5.3: Offshore wind power system 4. Offshore photovoltaic power system adjusted according to EMS instructions.

[0107] Step 5.4: The battery energy storage system absorbs / releases excess power to stabilize the system. :

[0108] Step 5.5: Achieve DC power balance:

[0109] Step 5.6: Fault Clearing and Grid Reconnection (Controlled Synchronization): The AC side circuit breaker of the grid-connected converter station is closed, the locked station is unlocked, and synchronization is restored according to the synchronization recovery slope. Controlling grid connection: , ;

[0110] Meanwhile, the offshore wind power system 4, the offshore photovoltaic power system and the battery energy storage system gradually restored MPPT output according to the controlled curve.

[0111] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An electrical wiring system for an offshore wind-solar co-current power station based on a DC power grid, characterized in that: It includes multiple distributed offshore wind and solar power stations connected in series with consistent structure. Each offshore wind and solar power station includes an offshore DC switch station (1). The offshore DC switch station is equipped with two parallel busbars (2). The two busbars (2) are connected to an offshore wind power generation system (4) through a wind turbine rectifier (3). The offshore photovoltaic power generation system (6) is connected to a string photovoltaic DC / DC converter (5) as input. The two busbars (2) are connected to the AC power grid system (8) through an onshore converter station (7) as output. The distributed offshore wind and solar power stations are connected to each other through busbar sectional switches.

2. The electrical wiring system for a marine wind-solar co-current power station based on a DC power grid according to claim 1, characterized in that: The offshore DC switch station (1) is equipped with a DC power distribution device, and the station load of the offshore DC switch station is powered by a DC / AC inverter (9).

3. The electrical wiring system for a marine wind-solar co-current power station based on a DC power grid according to claim 1, characterized in that: The offshore wind and solar power station is also equipped with a battery energy storage system (10). The battery energy storage system is connected to two busbars (2) through an energy storage DC / DC converter (11). The battery energy storage system includes a battery energy storage unit, an energy management system and a measurement and protection unit.

4. The electrical wiring system for a marine wind-solar co-current power station based on a DC power grid according to claim 1, characterized in that: Offshore wind power generation system (4) includes wind turbine generator set, frequency converter and wind turbine monitoring and protection device; offshore photovoltaic power generation system (6) includes photovoltaic cell module, DC combiner device and photovoltaic local monitoring device.

5. A control method for an electrical wiring system of a marine wind-solar co-current power station based on a DC power grid, as described in any one of claims 1-4, characterized in that: A three-tiered collaborative control strategy of "normal operation—minor fault support—major fault self-healing" is adopted. Through hierarchical optimization of the objective function and constraints, optimal power balance is achieved under normal operating conditions; reactive power priority support and DC voltage stability are achieved under minor faults; and converter station blocking, energy storage takeover, and power flow self-healing are achieved under major faults. The specific steps are as follows: Step 1: Determine the status of the AC power grid system to which the electrical wiring system of the offshore wind and solar co-current power station based on the DC grid is connected, and use different control strategies according to different statuses; Step 2: When the AC power grid system is in normal operating condition, the offshore wind power system and the offshore photovoltaic power system shall operate according to MPPT respectively; Step 3: When the AC power grid system is in a fault condition, further determine whether the fault is a minor fault condition or a major fault condition. Step 4: When the AC power grid system is under minor fault conditions, the onshore converter station of the offshore wind and solar co-current power station based on the DC power grid operates in the converter station adaptive STATCOM mode. Step 5: When the AC power grid system is under severe fault conditions, the electrical wiring system of the offshore wind and solar co-location power station based on the DC power grid will operate in the mode of onshore converter station lockout + battery energy storage system takeover + DC power flow redistribution to achieve system self-healing.

6. The control method for an electrical wiring system of a marine wind-solar co-current power station based on a DC power grid according to claim 5, characterized in that: Step 2 involves the following steps: Under normal AC grid conditions, the offshore wind-solar co-generation power station transmits power bidirectionally to the grid via an onshore converter station. Each station in the system actively optimizes power flow distribution to dynamically meet multiple optimization objectives. in Indicates system transmission efficiency. This indicates the voltage of the offshore DC bus. Describe the target voltage of the DC bus; According to the dynamic energy conservation of the DC bus, we have: in This represents the equivalent capacitance of the DC bus. This represents the total instantaneous active power of offshore wind / solar power connected to the DC grid. This indicates that the DC-side energy storage output power is positive when discharging and negative when charging; The state equation of the energy storage system is: in Indicates the battery's state of charge. Indicates the rated energy of the energy storage. Indicates the charging efficiency of the energy storage system. Indicates the discharge efficiency of the energy storage system; in, ;when At that time, energy storage system ; Under stable operating conditions, the following applies: . in, This represents the active power sent to or absorbed from the AC side by the k-th station. Active power is defined in the positive direction. Among them, offshore wind power generation systems and offshore photovoltaic power generation systems are operated according to MPPT; The onshore converter station operates in constant DC voltage mode to provide DC bus voltage support for the offshore DC power grid; Battery energy storage system control strategy tracking ,Right now: ; For each onshore converter station k that has not entered the STATCOM / lockdown state, its control adopts voltage and current control. Under this control strategy, the current command is: ;in , , Indicates control parameters; When the battery storage system is fully charged, that is, Offshore wind power systems and offshore photovoltaic power systems transmit electrical energy to the grid through onshore converter stations, that is, ; in Indicates loss.

7. The control method for an electrical wiring system of a marine wind-solar co-current power station based on a DC power grid according to claim 5, characterized in that: Step 3 is detailed below: Voltage sag is measured by measuring the amplitude of AC bus voltage. and duration of the fault This is used to determine the severity of the fault, that is: and This is considered a minor fault condition. or This is considered a serious fault condition; among them This represents the per-unit voltage amplitude of the corresponding AC bus; the value measured during a fault is recorded as follows. , Indicates the duration of the fault.

8. The control method for an electrical wiring system of a marine wind-solar co-current power station based on a DC power grid according to claim 5, characterized in that: Step 4 is detailed below: The adaptive STATCOM mode of the converter station can be represented as follows: in This represents the reactive power injection at station k, which is the main quantity under STATCOM mode; The operation strategy for onshore converter stations is as follows: Step 4.1: Switch the running mode to STATCOM running mode; Step 4.2: Active power output satisfies: And consider prioritizing the needs of reactive power support; Step 4.3: Adopt a reactive power control strategy. And it should satisfy the current constraint condition: ， Step 4.4: Other onshore converter stations continue to use constant DC voltage mode control, with energy storage systems participating in DC voltage support. ， Step 4.5: After the fault is cleared, the onshore converter station related to the faulty AC grid exits STATCOM operation mode and gradually restores active power according to the active power recovery slope. To avoid impacting the AC power grid and ultimately achieve the expected active power value: , .

9. The control method for an electrical wiring system of a marine wind-solar co-current power station based on a DC power grid according to claim 5, characterized in that: Step 5 is detailed below: Under severe fault conditions, the operating mode of converter station shutdown + battery energy storage system takeover + DC power flow redistribution is expressed as: The specific operation method is as follows: Step 5.1: The onshore converter station k associated with the faulty AC power grid is locked out; Step 5.2: Other onshore converter stations continue to use constant DC voltage mode control to support the main DC bus voltage; Step 5.3: Offshore wind power systems and offshore photovoltaic power systems are adjusted downwards according to EMS instructions. Step 5.4: The battery energy storage system absorbs / releases excess power to stabilize the system. : Step 5.5: Achieve DC power balance: Step 5.6: Fault Clearing and Grid Reconnection (Controlled Synchronization): The AC side circuit breaker of the grid-connected converter station is closed, the locked station is unlocked, and synchronization is restored according to the synchronization recovery slope. Controlling grid connection: , ; Meanwhile, offshore wind power systems, offshore photovoltaic power systems, and battery energy storage systems gradually recovered MPPT output according to the controlled curve.

Images