Hybrid line offshore wind power flexible direct current system control method and device, terminal and medium

Abstract

The invention discloses a hybrid line offshore wind power flexible direct current system control method, a hybrid line offshore wind power flexible direct current system control device, a terminal and a medium, and the scheme provided by the invention is applied to a hybrid line offshore wind power flexible direct current system comprising a series connection type direct current energy consumption device. The main loop switch module is controlled to be switched off, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to an energy consumption loop where the energy consumption valve module is located, and the voltage value of each energy consumption valve unit is increased; when the voltage value of each energy consumption valve unit reaches a preset voltage threshold value, according to the output power of the offshore converter station and a preset control target voltage, in combination with a preset system surplus power constraint condition, on-off of a switch element in the energy consumption valve unit is controlled, and the switching number of an energy consumption resistor of each energy consumption valve unit is controlled; therefore, total energy consumed by the energy consumption loop is controlled, and surplus power balance of the system is achieved.

Description

Technical Field

[0001] The present application relates to the field of offshore wind power technology, and in particular to a control method, device, terminal and medium for a hybrid line offshore wind power flexible direct current system. Background Art

[0002] With its high utilization rate and abundant resource reserves, offshore wind power is rapidly becoming one of the key areas for the development of new energy sources at present and in the future. As the scale of offshore wind power continues to expand and the transmission distance increases, intensive and centralized unified development and utilization will be the main way to utilize offshore wind power in the future. At present, offshore wind power is generally sent to onshore converter stations via submarine DC cables, and then the DC is converted into AC through converters and connected to the coastal power grid. However, with the rapid growth of the scale of offshore wind power development, this offshore wind power nearshore grid connection method is no longer suitable for future ultra-large-scale offshore wind power development scenarios. In order to further compress the transmission corridor, reduce the transmission cost, and avoid increasing the short-circuit current of the nearshore power grid, offshore wind power will be directly sent to the load center via a hybrid DC line of submarine cables and overhead lines, which will become one of the main ways to develop ultra-large-scale offshore wind power in the future.

[0003] In existing offshore wind power flexible direct current transmission projects, generally only direct current submarine cables are used for power transmission, and parallel direct current energy consumption devices are used to achieve fault voltage regulation. The specific principle is: after a fault occurs in the receiving power grid, the direct current voltage increases, and the parallel direct current energy consumption device is started to consume surplus power and maintain the direct current voltage. However, this device is not suitable for offshore wind power flexible direct current systems that are a mixture of submarine cables and overhead lines, resulting in the technical problem of low reliability in existing offshore wind power flexible direct current systems that are a mixture of submarine cables and overhead lines. Summary of the invention

[0004] The present application provides a hybrid line offshore wind power flexible direct current system control method, device, terminal and medium, which are used to solve the technical problem of low reliability of the existing offshore wind power flexible direct current system that is a mixture of submarine cables and overhead lines.

[0005] In order to solve the above technical problems, the first aspect of the present application provides a hybrid line offshore wind power flexible direct current system control method, which is applied to a hybrid line offshore wind power flexible direct current system including a series direct current energy consumption device, characterized in that the series direct current energy consumption device includes: a submarine cable port, an overhead line port, a main circuit switch module and an energy consumption valve module, the main circuit switch module and the energy consumption valve module are arranged between the submarine cable port and the overhead line port, and the main circuit switch module and the energy consumption valve module are connected in parallel; a plurality of energy consumption valve units are connected in series in the energy consumption valve module, and each energy consumption valve unit includes an energy consumption resistor and a switch element for controlling the energy consumption resistor to be switched in or out; the control method includes:

[0006] When a fault is detected in the hybrid line offshore wind power flexible direct current system, the main circuit switch module is controlled to be disconnected, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consumption circuit where the energy consumption valve module is located, so as to raise the voltage value of each energy consumption valve unit;

[0007] When the voltage value of each energy-consuming valve unit reaches a preset voltage threshold, the on-off of the switch elements in the energy-consuming valve unit is controlled according to the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint conditions, so as to consume the system surplus power of the hybrid line offshore wind power flexible direct current system.

[0008] Preferably, the expression of the system surplus power constraint condition is specifically:

[0009]

[0010] Where P w is the output power of the offshore converter station, n ch is the number of energy-consuming valve units with energy-consuming resistors in the switched-on state, U C To control the target voltage, R ch is the resistance value of the energy dissipation resistor.

[0011] Preferably, raising the voltage value of each energy-consuming valve unit includes:

[0012] The first switch tube in the energy-consuming valve unit is controlled to be disconnected so that the direct current flows to the energy storage capacitor in the energy-consuming valve unit, wherein the first switch tube is a bypass switch of the energy storage capacitor, and is used to control the access or bypass of the energy storage capacitor.

[0013] Preferably, when the voltage value of each energy-consuming valve unit reaches a preset voltage threshold, the method further includes:

[0014] The capacitor voltage value of each energy-consuming valve unit is monitored, and the on-off state of the first switch tube is controlled according to the comparison result between the capacitor voltage value and the upper and lower voltage thresholds.

[0015] Preferably, according to the comparison result between the capacitor voltage value and the voltage upper and lower thresholds, controlling the on and off state of the first switch tube specifically includes:

[0016] When the capacitor voltage value is not less than the voltage lower limit threshold and not greater than the voltage upper limit threshold, maintaining the current on-off state of the first switch tube;

[0017] When the capacitor voltage value is less than the voltage lower limit threshold, turning off the first switch tube;

[0018] When the capacitor voltage value is greater than the voltage lower limit threshold, the first switch tube is closed.

[0019] Preferably, the method for determining the upper and lower voltage thresholds specifically includes:

[0020] The voltage upper and lower thresholds are determined according to the average capacitor voltage value of each energy-consuming valve unit and the sum and difference between the average capacitor voltage value and a preset voltage-sharing threshold.

[0021] At the same time, the second aspect of the present application provides a hybrid line offshore wind power flexible direct current system control device, which is applied to a hybrid line offshore wind power flexible direct current system including a series direct current energy consumption device, wherein the series direct current energy consumption device includes: a submarine cable port, an overhead line port, a main circuit switch module and an energy consumption valve module, wherein the main circuit switch module and the energy consumption valve module are arranged between the submarine cable port and the overhead line port, and the main circuit switch module and the energy consumption valve module are connected in parallel; a plurality of energy consumption valve units are connected in series in the energy consumption valve module, and each energy consumption valve unit includes an energy consumption resistor and a switch element for controlling the energy consumption resistor to be switched in or out; the control device includes:

[0022] A current transfer unit is used to control the main circuit switch module to disconnect when a fault is detected in the hybrid line offshore wind power flexible direct current system, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consumption circuit where the energy consumption valve module is located, so as to raise the voltage value of each energy consumption valve unit;

[0023] The active energy consumption unit is used to control the on and off of the switch elements in the energy consumption valve unit when the voltage value of each energy consumption valve unit reaches a preset voltage threshold, according to the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint conditions, so as to consume the system surplus power of the hybrid line offshore wind power flexible direct current system.

[0024] Preferably, the expression of the system surplus power constraint condition is specifically:

[0025]

[0026] Where P w is the output power of the offshore converter station, n ch is the number of energy-consuming valve units with energy-consuming resistors in the switched-on state, U C To control the target voltage, R ch is the resistance value of the energy dissipation resistor.

[0027] The third aspect of the present application also provides a hybrid line offshore wind power flexible direct current system control terminal, including: a memory and a processor;

[0028] The memory is used to store program codes, and the program codes correspond to a hybrid line offshore wind power flexible direct current system control method as described in the first aspect of the present application;

[0029] The processor is used for reading and executing the program code.

[0030] The fourth aspect of the present application also provides a computer-readable storage medium, which stores a program code corresponding to a hybrid line offshore wind power flexible direct current system control method as described in the first aspect of the present application. When the program code is executed by a processor, a hybrid line offshore wind power flexible direct current system control method as described in the first aspect of the present application can be implemented.

[0031] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0032] The solution provided in the present application is applied to a hybrid line offshore wind power flexible direct current system including a series direct current energy consuming device, the series direct current energy consuming device including: a submarine cable port, an overhead line port, a main circuit switch module and an energy consuming valve module, and the control method includes: when a fault of the hybrid line offshore wind power flexible direct current system is detected, the voltage of the overhead line port of the series distributed direct current energy consuming device is controlled to zero according to the fixed direct current voltage control commonly used in the onshore converter station, and the voltage drop of the overhead line is considered. At this time, the direct current voltage at the port of the onshore converter station is negative. At this time, the main circuit switch module is controlled to be disconnected, so that the direct current current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consuming circuit where the energy consuming valve module is located, so that the voltage value of each energy consuming valve unit is raised; when the voltage value of each energy consuming valve unit reaches a preset voltage threshold, according to the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint, the switching element in the energy consuming valve unit is controlled to be on and off, and the number of energy consuming resistors of each energy consuming valve unit is controlled to be switched on and off, thereby controlling the total energy consumed by the energy consuming circuit and achieving system surplus power balance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 A schematic diagram of the architecture of an offshore wind power flexible direct current system including a submarine cable-overhead line hybrid line provided for this application.

[0035] Figure 2A schematic diagram of the circuit structure of the energy-consuming valve unit in the series DC energy-consuming device provided in the present application.

[0036] Figure 3 A flow chart of an embodiment of a hybrid line offshore wind power flexible direct current system control method provided in the present application.

[0037] Figure 4 A schematic flow chart of the overall logic of a hybrid line offshore wind power flexible direct current system control method provided in this application.

[0038] Figure 5 A flow chart of the logic of the active voltage balancing strategy in a hybrid line offshore wind power flexible direct current system control method provided in this application.

[0039] Figure 6 A structural schematic diagram of an embodiment of a hybrid line offshore wind power flexible direct current system control device provided in this application.

[0040] Figure 7 A structural schematic diagram of an embodiment of a hybrid line offshore wind power flexible direct current system control terminal provided in this application. DETAILED DESCRIPTION

[0041] In view of the problems existing in the existing technology, it has been found through research that since the existing offshore wind power flexible direct current transmission projects generally only use direct current submarine cables, there is no need to consider the problem of direct current fault ride-through. However, the fault rate of overhead lines is high and direct current faults cannot be ignored. After a fault occurs in the overhead line, in addition to clearing the direct current fault, the system also needs to consume the system surplus power to avoid the direct current voltage being too high to trigger the system protection and cause shutdown, or even endanger the safety of the equipment. Therefore, it is necessary to install energy-consuming devices in the system. However, the offshore wind power flexible direct current system of the submarine cable-overhead line hybrid direct current line needs to consider the problem of direct current fault ride-through. However, based on the full half-bridge hybrid direct current line, the DC fault ride-through problem is not solved. When clearing a DC fault, the MMC needs to reduce the DC voltage to zero or negative voltage, which conflicts with the need to maintain a stable DC voltage when the parallel DC energy consumption device is working. Therefore, the parallel DC energy consumption device is not compatible with the submarine cable-overhead line hybrid line flexible DC system, and cannot effectively consume surplus power for the submarine cable-overhead line hybrid line system, resulting in the current technical status quo of low reliability of the existing offshore wind power flexible DC system that is a hybrid of submarine cables and overhead lines. Therefore, seeking a surplus power consumption solution that is compatible with the submarine cable-overhead line hybrid line system has become one of the key research goals of technical personnel in this field.

[0042] The embodiments of the present application provide a hybrid line offshore wind power flexible direct current system control method, device, terminal and medium, which are used to solve the technical problem of low reliability of the existing offshore wind power flexible direct current system that is a mixture of submarine cables and overhead lines.

[0043] In order to make the purpose, features, and advantages of the invention of this application more obvious and easy to understand, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the embodiments described below are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0044] First, a detailed description of an embodiment of a hybrid line offshore wind power flexible direct current system for implementing the control method of the present application is provided, as follows:

[0045] Please refer to Figure and Figure 2 ,like Figure 1 As shown, the hybrid line offshore wind power flexible direct current system based on the submarine cable-overhead line of the series DC energy consumption device provided in this embodiment includes an offshore converter station, a submarine cable, a terminal conversion station, an overhead line, and an onshore converter station, wherein the series distributed DC energy consumption device in the terminal conversion station is composed of a main circuit and an energy consumption circuit in parallel, and the device is connected in series in the DC positive and negative lines respectively, one end is connected to the submarine cable, and the other end is connected to the overhead line, and the main circuit includes a main circuit mechanical switch and a main circuit power electronic switch array, wherein the main circuit power electronic switch array is composed of submodules (SM) connected in series and parallel, and since the main circuit is used to realize current transfer during the breaking process, it only needs to withstand a voltage drop higher than the on-state voltage drop of the power device of the energy consumption circuit, and the number of series connections is very small, so the loss generated by the main circuit power electronic switch array can be basically ignored. The main circuit mechanical switch is used to flow the DC current in the normal operating state, and the main circuit current is quickly disconnected after it is fully transferred to the energy consumption circuit during the fault period, and bears half the voltage of the DC bus voltage. The submodule in the main circuit power electronic switch array is composed of a power electronic switch array, and a full-bridge module is composed of power devices, anti-parallel diodes and capacitors. When the power device is in the on state, the capacitor voltage is zero. When the power device is in the off state, the DC current charges the capacitor and the capacitor voltage rises.

[0046] The energy-consuming valve module is composed of multiple energy-consuming valve units in series. One feasible energy-consuming valve topology is as follows: Figure 2 As shown, each energy-consuming valve unit specifically includes: a first diode D1, a first switch tube T1, a dynamic voltage-equalizing resistor R d , energy storage capacitor C, second diode D2, second switch tube T2 and energy dissipation resistor R ch ;

[0047] The cathode of the first diode D1 is connected to the first port of the energy-consuming valve unit, and the anode is connected to the second port of the energy-consuming valve unit;

[0048] The first switch tube is connected in parallel with the first diode D1, and the anode of the first switch tube D1 is connected to the first port of the energy-consuming valve unit, and the cathode is connected to the second port of the energy-consuming valve unit;

[0049] Dynamic voltage balancing resistor R d In parallel with the second diode D2, the dynamic voltage balancing resistor R d One end of the second diode D2 is connected to the anode of the second diode D2 and the first port of the energy consumption valve unit, and the dynamic voltage balancing resistor R d The other end is connected in series with the cathode of the second diode D2 and the energy storage capacitor C, and then connected to the second port of the energy consumption valve unit to form an RCD buffer loop;

[0050] Energy dissipation resistor R ch The second switch tube T2 is connected in series to form an energy-consuming resistance loop, and the energy-consuming resistance loop is connected in parallel with the RCD buffer loop.

[0051] It should be noted that a single energy-consuming valve consists of a capacitor C and a dynamic voltage-equalizing resistor R d , diode D2, energy dissipation resistor R ch , integrated gate commutated thyristors (IGCT) T1 and T2, anti-parallel diode D1, bypass switch K, R d Connected in parallel with D2 and then in series with capacitor C to form an RCD snubber circuit. ch Together with T2, it forms an energy-consuming circuit. The RCD buffer circuit and the energy-consuming circuit are then connected in parallel with T1, D1 and K. When T1 is turned on, the capacitor voltage is zero. When T1 is turned off, the current charges the capacitor through the RCD buffer circuit. The capacitor voltage can be controlled by controlling the on and off of T1. When the capacitor voltage is maintained at the rated voltage, turning on T2 connects the energy-consuming resistor to consume the surplus power of the system. Turning off T2 cuts out the energy-consuming resistor. By controlling the on and off of T2, the surplus power of the system can be accurately consumed. The anti-parallel diode D1 is used to reverse the DC current when the offshore converter station is started.

[0052] In addition, the energy-consuming valve unit mentioned in this embodiment is not only Figure 2 This topology structure shown in the figure can control the energy dissipation resistor R ch Energy-consuming circuit topologies with input and output functions can be used as alternative implementations.

[0053] More specifically, the energy-consuming valve unit also includes: an energy-consuming valve bypass switch K, which is used to control the input or output of the energy-consuming valve unit. If the energy-consuming valve fails, the bypass switch will be closed. Under normal operating conditions, the switch will be opened or actuated when the voltage of the energy-consuming valve is too high, so as to protect the device from over-pressure damage.

[0054] It can be understood that the series DC energy consumption device mentioned in this embodiment is equipped with a control device, and the control device is specifically used to control each switching element in the series DC energy consumption device according to the control method of the present application, so as to implement the control method provided by the present application, wherein the specific description of the control method and the control device can be found in the following embodiment description.

[0055] Next is a detailed description of a hybrid line offshore wind power flexible direct current system control method provided by this application, which is as follows:

[0056] See also Figure 3 and Figure 4 The present embodiment provides a hybrid line offshore wind power flexible direct current system control method, comprising:

[0057] Step 101: When a hybrid line offshore wind power flexible direct current system fault is detected, the main circuit switch module is controlled to be disconnected, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consumption circuit where the energy consumption valve module is located, so as to raise the voltage value of each energy consumption valve unit;

[0058] It should be noted that when there is no fault in the system, the mechanical switch of the main circuit of the system is closed, the power device of the power electronic switch array is turned on, and the current of the system flows to the onshore converter station through the main circuit. The power device T1 of each energy-consuming valve in the energy-consuming circuit is turned on, T2 is turned off, and the energy-consuming resistor is in the bypass cut-out state.

[0059] When a fault occurs in the system, the current transfer control phase corresponding to step 101 is first entered, which specifically includes: controlling the power electronic switch array power devices of the main circuit to be turned off, and the capacitor voltage to be raised; when the main circuit current passes through zero, the mechanical switch is opened. When the mechanical switch is in the opening position, the power devices T1 of each energy-consuming valve in the energy-consuming circuit are closed, and the capacitor voltage is raised.

[0060] Step 102: When the voltage value of each energy-consuming valve unit reaches a preset voltage threshold, the on-off of the switch elements in the energy-consuming valve unit is controlled according to the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint conditions, to consume the system surplus power of the hybrid line offshore wind power flexible direct current system.

[0061] It should be noted that after the voltage value of each energy-consuming valve unit reaches a certain level, the active energy-consuming processing stage corresponding to step 102 is entered. To ensure the voltage consistency of each energy-consuming valve capacitor, when the voltage of each energy-consuming valve capacitor rises to the rated voltage, the power device T2 is controlled to be turned on or off according to the system surplus power constraint condition of the embodiment to accurately consume the system surplus power.

[0062] More specifically, the expression of the system surplus power constraint is:

[0063]

[0064] Where P w is the output power of the offshore converter station, n ch is the number of energy-consuming valve units with energy-consuming resistors in the switched-on state, U C To control the target voltage, R ch is the resistance value of the energy dissipation resistor.

[0065] When an overhead line fails, the offshore converter station still uses VF control to maintain stable AC voltage. The onshore converter station still uses fixed DC voltage control, and the control target is to control the voltage at the overhead line port of the series-connected distributed DC energy-consuming device to zero. Considering the voltage drop of the overhead line, the DC voltage at the port of the onshore converter station is negative at this time. When the main circuit mechanical switch and the main circuit power electronic switch array of the series-connected distributed energy-consuming device are both closed, DC current flows through the energy-consuming circuit, and the energy-consuming valve controls the voltage at both ends of the energy-consuming valve by controlling the conduction and disconnection of the T1 switch tube. The control target is the rated voltage U C , and satisfies , where N is the number of energy-consuming valves in a single series distributed energy-consuming device, U dc is the rated voltage of the DC system.

[0066] In order to balance the system surplus power, a series of distributed energy consumption devices is set to obtain the power P sent by the offshore converter station. w When the switch tube of energy-consuming valve T2 is turned on, the energy consumed by the energy-consuming valve is Therefore, by controlling the switch tubes of each energy-consuming valve T2, the total energy consumed by the energy-consuming circuit can be controlled, and the , where n ch is the number of energy-consuming valves in which the T2 switch tube is in the on state, according to The constraint condition formula is used to determine the number of energy-consuming valves that need to be equipped with energy-consuming resistors, and the on-off state of the T2 switch tube in each energy-consuming valve unit is controlled according to the number.

[0067] In addition, in the process of controlling the power device T2 to consume the system surplus power, at the same time, the preset active voltage equalization strategy can be used to control the on and off of the power device T1 to maintain the stability of the capacitor voltage, thereby further improving the stability and reliability of the system in the surplus power processing process.

[0068] It should be noted that when the mechanical switch is in the open position, the power device T1 of each energy-consuming valve in the energy-consuming circuit is disconnected, and the capacitor voltage rises. When the capacitor voltage rises beyond a certain limit, in order to ensure the consistency of the capacitor voltage of each energy-consuming valve, an active voltage balancing strategy can be adopted to control the conduction and cutoff of the power device T1 to maintain the capacitor voltage stability. The active voltage balancing strategy is as follows Figure 5As shown, U sm_avg is the average voltage value of each energy-consuming valve, is the voltage balancing threshold, which is used to reduce the switching frequency of the power device T1. smi Greater than , indicating that the energy consumption valve voltage is too high, then the power device T1 is turned on, and the capacitor will pass through R d , T1 discharges; if the i-th energy consumption valve voltage U smi Less than , indicating that the energy consumption valve voltage is too low, the power device T1 is disconnected, and the DC current will charge the capacitor through the diode D2. If the i-th energy consumption valve voltage U smi In , the current switch state remains unchanged.

[0069] The above is a detailed description of an embodiment of a hybrid line offshore wind power flexible direct current system control method provided in the present application. The following is a detailed description of an embodiment of a hybrid line offshore wind power flexible direct current system control device provided in the present application.

[0070] See also Figure 6 This embodiment provides a hybrid line offshore wind power flexible direct current system control device, which is applied to a hybrid line offshore wind power flexible direct current system including a series direct current energy consumption device, and the control device includes:

[0071] The current transfer unit 201 is used to control the main circuit switch module to disconnect when a fault of the hybrid line offshore wind power flexible direct current system is detected, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consumption circuit where the energy consumption valve module is located, so as to raise the voltage value of each energy consumption valve unit;

[0072] The active energy consumption unit 202 is used to control the on and off of the switch elements in the energy consumption valve unit when the voltage value of each energy consumption valve unit reaches a preset voltage threshold, based on the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint conditions, so as to consume the system surplus power of the hybrid line offshore wind power flexible direct current system.

[0073] More specifically, the expression of the system surplus power constraint is:

[0074]

[0075] Where P w is the output power of the offshore converter station, n ch is the number of energy-consuming valve units with energy-consuming resistors in the switched-on state, U C To control the target voltage, R ch is the resistance value of the energy dissipation resistor.

[0076] Further, raising the voltage value of each energy-consuming valve unit includes:

[0077] The first switch tube in the energy-consuming valve unit is controlled to be disconnected so that a direct current flows to the energy storage capacitor in the energy-consuming valve unit, wherein the first switch tube is a bypass switch of the energy storage capacitor, and is used to control the access or bypass of the energy storage capacitor.

[0078] Furthermore, when the voltage value of each energy-consuming valve unit reaches a preset voltage threshold, the method further includes:

[0079] The capacitor voltage value of each energy-consuming valve unit is monitored, and the on-off state of the first switch tube is controlled according to the comparison result between the capacitor voltage value and the upper and lower voltage thresholds.

[0080] Furthermore, according to the comparison result between the capacitor voltage value and the voltage upper and lower thresholds, controlling the on and off state of the first switch tube specifically includes:

[0081] When the capacitor voltage value is not less than the voltage lower limit threshold and not greater than the voltage upper limit threshold, the current on-off state of the first switch tube is maintained;

[0082] When the capacitor voltage value is less than the voltage lower limit threshold, the first switch tube is turned off;

[0083] When the capacitor voltage value is greater than the voltage lower limit threshold, the first switch tube is closed.

[0084] Furthermore, the voltage upper and lower thresholds are determined by:

[0085] The voltage upper and lower thresholds are determined according to the average capacitor voltage value of each energy-consuming valve unit and the sum and difference between the average capacitor voltage value and a preset voltage-sharing threshold value.

[0086] like Figure 7 As shown, the present application also provides a hybrid line offshore wind power flexible direct current system control terminal, including: a memory and a processor;

[0087] The memory is used to store program codes, and the program codes correspond to a hybrid line offshore wind power flexible direct current system control method mentioned in the above embodiment;

[0088] The processor is used to read and execute program code.

[0089] The present application also provides a computer-readable storage medium, which stores a program code corresponding to a hybrid line offshore wind power flexible direct current system control method as mentioned in the above embodiment. When the program code is executed by a processor, a hybrid line offshore wind power flexible direct current system control method as mentioned in the above embodiment can be implemented.

[0090] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the terminals, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0091] In the several embodiments provided in the present application, it should be understood that the disclosed terminals, devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of units is only a logical function division, and there may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces, devices or units, which can be electrical, mechanical or other forms.

[0092] The terms "first", "second", "third", "fourth", etc. (if any) in the specification of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0093] It should be understood that in the present application, "at least one (item)" means one or more, and "plurality" means two or more. "And / or" is used to describe the association relationship of associated objects, indicating that three relationships may exist. For example, "A and / or B" can mean: only A exists, only B exists, and A and B exist at the same time, where A and B can be singular or plural. The character " / " generally indicates that the objects associated before and after are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can mean: a, b, c, "a and b", "a and c", "b and c", or "a and b and c", where a, b, c can be single or multiple.

[0094] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0095] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0096] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0097] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A hybrid line offshore wind power flexible direct current system control method, applied to a hybrid line offshore wind power flexible direct current system including a series direct current energy consumption device, characterized in that: The series DC energy dissipation device comprises: a submarine cable port, an overhead line port, a main circuit switch module and an energy dissipation valve module, wherein the main circuit switch module and the energy dissipation valve module are arranged between the submarine cable port and the overhead line port, and the main circuit switch module and the energy dissipation valve module are connected in parallel; a plurality of energy dissipation valve units are connected in series in the energy dissipation valve module, and each energy dissipation valve unit comprises an energy dissipation resistor and a switch element for controlling the energy dissipation resistor to be switched in or out; the control method comprises: When a fault is detected in the hybrid line offshore wind power flexible direct current system, the main circuit switch module is controlled to be disconnected, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consumption circuit where the energy consumption valve module is located, so as to raise the voltage value of each energy consumption valve unit; When the voltage value of each energy-consuming valve unit reaches a preset voltage threshold, the on-off of the switch elements in the energy-consuming valve unit is controlled according to the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint conditions, so as to consume the system surplus power of the hybrid line offshore wind power flexible direct current system.

2. A hybrid line offshore wind power flexible direct current system control method according to claim 1, characterized in that: The expression of the system surplus power constraint condition is specifically: Where P w is the output power of the offshore converter station, n ch is the number of energy-consuming valve units with energy-consuming resistors in the switched-on state, U C To control the target voltage, R ch is the resistance value of the energy dissipation resistor.

3. A hybrid line offshore wind power flexible direct current system control method according to claim 1, characterized in that: The voltage values ​​for raising each energy-consuming valve unit include: The first switch tube in the energy-consuming valve unit is controlled to be disconnected so that the direct current flows to the energy storage capacitor in the energy-consuming valve unit, wherein the first switch tube is a bypass switch of the energy storage capacitor, and is used to control the access or bypass of the energy storage capacitor.

4. A hybrid line offshore wind power flexible direct current system control method according to claim 3, characterized in that: When the voltage value of each energy-consuming valve unit reaches a preset voltage threshold, the method further includes: The capacitor voltage value of each energy-consuming valve unit is monitored, and the on-off state of the first switch tube is controlled according to the comparison result between the capacitor voltage value and the upper and lower voltage thresholds.

5. A hybrid line offshore wind power flexible direct current system control method according to claim 4, characterized in that: According to the comparison result of the capacitor voltage value and the voltage upper and lower thresholds, controlling the on and off state of the first switch tube specifically includes: When the capacitor voltage value is not less than the voltage lower limit threshold and not greater than the voltage upper limit threshold, maintaining the current on-off state of the first switch tube; When the capacitor voltage value is less than the voltage lower limit threshold, turning off the first switch tube; When the capacitor voltage value is greater than the voltage lower limit threshold, the first switch tube is closed.

6. A hybrid line offshore wind power flexible direct current system control method according to claim 4, characterized in that: The method for determining the voltage upper and lower thresholds specifically includes: The voltage upper and lower thresholds are determined according to the average capacitor voltage value of each energy-consuming valve unit and the sum and difference between the average capacitor voltage value and a preset voltage-sharing threshold.

7. A hybrid line offshore wind power flexible direct current system control device, applied to a hybrid line offshore wind power flexible direct current system including a series direct current energy consumption device, characterized in that: The series DC energy dissipation device comprises: a submarine cable port, an overhead line port, a main circuit switch module and an energy dissipation valve module, wherein the main circuit switch module and the energy dissipation valve module are arranged between the submarine cable port and the overhead line port, and the main circuit switch module and the energy dissipation valve module are connected in parallel; a plurality of energy dissipation valve units are connected in series in the energy dissipation valve module, and each energy dissipation valve unit comprises an energy dissipation resistor and a switch element for controlling the energy dissipation resistor to be switched in or out; the control device comprises: A current transfer unit is used to control the main circuit switch module to disconnect when a fault is detected in the hybrid line offshore wind power flexible direct current system, so that the direct current of the hybrid line offshore wind power flexible direct current system is transferred to the energy consumption circuit where the energy consumption valve module is located, so as to raise the voltage value of each energy consumption valve unit; The active energy consumption unit is used to control the on and off of the switch elements in the energy consumption valve unit when the voltage value of each energy consumption valve unit reaches a preset voltage threshold, according to the output power of the offshore converter station and the preset control target voltage, combined with the preset system surplus power constraint conditions, so as to consume the system surplus power of the hybrid line offshore wind power flexible direct current system.

8. A hybrid line offshore wind power flexible direct current system control device according to claim 7, characterized in that: The expression of the system surplus power constraint condition is specifically: Where P w is the output power of the offshore converter station, n ch is the number of energy-consuming valve units with energy-consuming resistors in the switched-on state, U C To control the target voltage, R ch is the resistance value of the energy dissipation resistor.

9. A hybrid line offshore wind power flexible direct current system control terminal, characterized in that: include: Memory and processor; The memory is used to store program codes, and the program codes correspond to a hybrid line offshore wind power flexible direct current system control method according to any one of claims 1 to 6; The processor is used for reading and executing the program code.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a program code corresponding to a hybrid line offshore wind power flexible direct current system control method as described in any one of claims 1 to 6. When the program code is executed by a processor, a hybrid line offshore wind power flexible direct current system control method as described in any one of claims 1 to 6 can be implemented.

Images