Multi-terminal networking type flexible interconnection equipment and direct-current voltage hierarchical control method thereof

Abstract

The invention belongs to the technical field of power systems, and particularly discloses multi-terminal networking type flexible interconnection equipment and a direct-current voltage hierarchical control method thereof. A traditional flexible interconnection device is based on network tracking type control and cannot actively construct power grid frequency and voltage after a main network loses power. The multi-terminal networking type flexible interconnection equipment constructed by the invention has grid-connected and off-grid operation capability, and after the connected feeder lines are subjected to unplanned power failure, the control center controls the plurality of AC / DC converters to supply power to loads on the feeder lines, so that a local micro-grid is formed, stable voltage and frequency are spontaneously established, and the micro-grid is independently constructed after a main grid fails.

Description

Technical Field

[0001] The present application belongs to the technical field of power systems, and more specifically, to a multi-terminal meshing type flexible interconnection equipment and a DC voltage hierarchical control method thereof. Background Art

[0002] Traditional flexible interconnection devices are mostly based on two back-to-back voltage source converters (VSCs) to achieve flexible interconnection and power mutual assistance between distribution networks. Among them, one port adopts DC voltage-active power control to maintain the stability of the DC voltage of the flexible interconnection equipment; the other port adopts active power-reactive power control to control the output current of the VSC and then control its output power. However, with the continuous improvement of the power supply reliability requirements of the power system, the above-mentioned traditional flexible interconnection devices face two difficulties in practical applications. On the one hand, the flexible interconnection device with grid-following control depends on the voltage and frequency given by the power grid, and cannot independently build a microgrid after the main grid fails; on the other hand, after the flexible interconnection equipment based on the master-slave control structure fails or exits operation on the main converter side, the DC voltage of the entire equipment will lose stability or even collapse. Summary of the invention

[0003] In view of the defects of the prior art, the purpose of this application is to provide a multi-terminal meshing type flexible interconnection equipment, aiming to solve the problem that the flexible interconnection device with grid-following control in the prior art depends on the voltage and frequency given by the power grid and cannot independently build a microgrid after a main grid failure.

[0004] To achieve the above objectives, in a first aspect, the present application provides a multi-terminal networking type flexible interconnection device, including: Inverter, energy storage unit and control unit; The converter includes a bidirectional DC / DC converter and multiple AC / DC converters. Each AC / DC converter is connected to a feeder. The low-voltage side of the bidirectional DC / DC converter is connected to the energy storage unit. The DC sides of the converters are cascaded and connected to the same DC bus. The control unit is used to control multiple AC / DC converters to supply power to the loads on each feeder when any feeder has an unplanned power outage.

[0005] In some embodiments, it also includes: A DC capacitor connected to the AC / DC converter is used to inertially adjust the DC voltage when the DC voltage of the multi-terminal meshing flexible interconnection equipment fluctuates due to an imbalance of DC power inside the multi-terminal meshing flexible interconnection equipment; Accordingly, the energy storage unit is used to perform inertial regulation on the DC voltage.

[0006] In some embodiments, before the DC voltage reaches a rated DC voltage, the energy storage unit is configured to: Adjust its output power and perform primary voltage regulation on the DC voltage; Accordingly, the AC / DC converter is used to adjust its output power and perform primary voltage regulation on the DC voltage.

[0007] In some embodiments, when the absolute value of the deviation between the DC voltage and the rated value of the DC voltage is greater than the voltage dead zone set by the control unit, the control unit is used to perform secondary voltage regulation on the DC voltage.

[0008] In some embodiments, when the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to the imbalance of DC power inside the multi-terminal meshed flexible interconnection equipment, the DC capacitor is also used to discharge or absorb electric energy to perform inertial regulation of the DC voltage. Accordingly, the energy storage unit is also used to perform inertial regulation of the DC voltage according to a first control signal, and the first control signal is generated according to the control strategy of the DC / DC converter.

[0009] In some embodiments, before the DC voltage reaches the rated value of the DC voltage, the energy storage unit is also used to spontaneously increase its output power according to the first control signal and perform a voltage regulation on the DC voltage. Correspondingly, the AC / DC converter is used to spontaneously reduce its corresponding output power according to the second control signal and perform a voltage regulation on the DC voltage. The second control signal is generated according to the control strategy of the AC / DC converter.

[0010] In some embodiments, when the absolute value of the deviation between the DC voltage and the rated value of the DC voltage is greater than the voltage dead zone set by the control unit, the control unit is further configured to: According to the deviation, a power deviation reference value at the DC bus is obtained; According to the rated capacity of each AC / DC converter in grid-connected operation, determine the power deviation reference value portion at the DC bus that each AC / DC converter in grid-connected operation needs to bear; According to the power deviation part at the DC bus that each AC / DC converter in grid operation needs to bear, the active power command value sent to each AC / DC converter in grid operation is determined to perform secondary voltage regulation on the DC voltage.

[0011] In view of the defects of the prior art, the purpose of this application is to provide a hierarchical control method for the DC voltage of multi-terminal meshed flexible interconnected equipment, aiming to solve the problem in the prior art that the DC voltage of the entire equipment will lose stability after a failure occurs on the main converter side or the equipment stops operating based on a master-slave control structure.

[0012] In a second aspect, an embodiment of the present application provides a DC voltage hierarchical control method for a multi-terminal meshed flexible interconnection equipment, which is applied to a multi-terminal meshed flexible interconnection equipment as described in the first aspect or any embodiment of the first aspect, including: When the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to an imbalance of the DC power inside the multi-terminal meshed flexible interconnection equipment, the DC voltage is inertially adjusted through the DC capacitor and the energy storage unit inside the multi-terminal meshed flexible interconnection equipment; Before the DC voltage reaches the rated value of the DC voltage, the DC voltage is regulated once by the energy storage unit and multiple AC / DC converters to spontaneously adjust their output power; When the absolute value of the deviation between the DC voltage and the rated value of the DC voltage is greater than the voltage dead band set by the control unit, the control unit performs secondary voltage regulation on the DC voltage.

[0013] In a third aspect, the present application provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory, wherein when the programs stored in the memory are executed, the processor is used to execute the method described in the second aspect or any embodiments of the second aspect.

[0014] In a fourth aspect, the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method described in the second aspect or any embodiments of the second aspect.

[0015] In a fifth aspect, the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method described in the second aspect or any embodiments of the second aspect.

[0016] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The multi-terminal meshed flexible interconnection equipment provided in this application has the ability to operate on and off the grid. After the connected feeder is unplanned power outage, the control center controls multiple AC / DC converters to supply power to the loads on each feeder to form a local microgrid, spontaneously establish a stable voltage and frequency, and realize the independent construction of a microgrid after the main grid fails. The DC voltage hierarchical control method of the multi-terminal meshed flexible interconnection equipment proposed in this application includes three parts: inertia regulation, primary voltage regulation, and secondary voltage regulation. After the DC voltage fluctuates: the energy storage unit and the DC capacitor can resist the rapid change of the DC voltage through inertia regulation; the energy storage unit and the VSC (i.e., the AC / DC converter) can change their output power through the primary voltage regulation link, thereby participating in the DC voltage regulation of the multi-terminal meshed flexible interconnection equipment; the secondary voltage regulation link is used to achieve the differenceless regulation of the DC voltage. Multiple converters jointly participate in the DC voltage control of the multi-terminal meshed flexible interconnection equipment, avoiding the excessive dependence of the multi-terminal meshed flexible interconnection equipment on the operating state of a single converter, and can still maintain the stability of the DC voltage after a fault occurs on any converter side or exits operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a multi-terminal networking type flexible interconnection equipment provided in an embodiment of the present application; Figure 2 is a schematic diagram of a DC voltage hierarchical control mechanism provided in an embodiment of the present application; Figure 3 is a schematic diagram of a DC / DC converter control strategy provided in an embodiment of the present application; Figure 4 is a schematic diagram of a VSC control strategy provided in an embodiment of the present application; Figure 5 is a schematic diagram of a grid voltage waveform provided in an embodiment of the present application; Figure 6 is a schematic diagram of a DC voltage waveform provided in an embodiment of the present application; Figure 7 It is a flow chart of a method for hierarchical control of DC voltage of multi-terminal meshing flexible interconnection equipment provided in an embodiment of the present application; Figure 8 It is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0019] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0020] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, the first feeder and the second feeder are used to distinguish different feeders rather than to describe a specific order of the feeders.

[0021] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0022] In the description of the embodiments of the present application, unless otherwise specified, “plurality” means two or more than two. For example, “plurality” means two or more than two AC / DC converters.

[0023] The present application provides a multi-terminal meshing type flexible interconnection equipment and a DC voltage hierarchical control method thereof. The topology structure of the multi-terminal meshing type flexible interconnection equipment is as follows: Figure 1 As shown, the control unit is able to receive the operating information of the multi-terminal meshed flexible interconnected equipment and issue power instructions to each AC / DC converter. When any feeder has an unplanned power outage, first, the VSC converter can spontaneously establish a local microgrid to supply power to important loads on the feeder. Then, the DC bus inside the multi-terminal meshed flexible interconnected equipment fluctuates under the action of unbalanced power. The energy storage unit and DC capacitor spontaneously resist the rapid changes in the DC bus voltage through inertia adjustment; the energy storage unit and VSC converter change their output power under primary voltage regulation and actively participate in the DC bus voltage regulation. Subsequently, when the absolute value of the DC voltage deviation is greater than the voltage dead zone set by the control unit , the secondary voltage regulation link of the control unit will be triggered to calculate the power deviation of the DC bus. Then, the control unit calculates the power command value, coordinates the output power of the VSC converter in normal grid-connected operation, and realizes the error-free regulation of the DC voltage of the multi-terminal meshed flexible interconnection equipment. The DC voltage hierarchical control method proposed in this application avoids the excessive dependence of the multi-terminal meshed flexible interconnection equipment on the operating status of a single converter. After a fault occurs on any converter side or it exits operation, the multi-terminal meshed flexible interconnection equipment proposed in this application can still maintain DC voltage stability.

[0024] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0025] See also Figure 1 The present application embodiment provides a multi-terminal networking type flexible interconnection device, including: Inverter, energy storage unit and control unit; The converter includes a bidirectional DC / DC converter and multiple AC / DC converters. Each AC / DC converter is connected to a feeder. The low-voltage side of the bidirectional DC / DC converter is connected to the energy storage unit. The DC sides of the converters are cascaded and connected to the same DC bus. The control unit is used to control multiple AC / DC converters to supply power to the loads on each feeder when any feeder has an unplanned power outage.

[0026] In an embodiment of the present application, the multi-terminal meshing type flexible interconnection equipment includes a converter, an energy storage unit and a control unit. Among them, the converter includes a bidirectional DC / DC converter and a plurality of AC / DC converters. Each AC / DC converter is connected to a feeder, the low-voltage side of the bidirectional DC / DC converter is connected to the energy storage unit, and the DC sides of all converters are cascaded and connected to the same DC bus. The control unit is also integrated in the multi-terminal meshing type flexible interconnection equipment to coordinate the operation of the converter. Specifically, when any feeder has an unplanned power outage, the control unit controls multiple AC / DC converters to supply power to the loads on each feeder to spontaneously establish a local microgrid.

[0027] For example, Figure 1 As shown, the multi-terminal meshed flexible interconnection equipment includes three AC / DC converters, namely the first voltage source converter (VSC), the second VSC, and the third VSC. Each AC / DC converter is connected to a 380V feeder; a bidirectional DC / DC converter, whose low-voltage side is connected to the energy storage unit; all the converters are cascaded on the DC side and connected to the same 750V DC bus.

[0028] The multi-terminal meshing type flexible interconnection equipment provided in the embodiment of the present application is based on grid-following control and cannot actively build the grid frequency and voltage after the main grid loses power, compared with the traditional flexible interconnection device. The multi-terminal meshing type flexible interconnection equipment constructed in the present application has the ability to operate on and off the grid. After the connected feeder has an unplanned power outage, the control center controls multiple AC / DC converters to supply power to the loads on each feeder to form a local microgrid, spontaneously establish a stable voltage and frequency, and realize the independent construction of a microgrid after a main grid failure.

[0029] Furthermore, in some embodiments, the multi-terminal networking type flexible interconnection equipment further includes: A DC capacitor connected to the AC / DC converter is used to inertially adjust the DC voltage when the DC voltage of the multi-terminal meshing flexible interconnection equipment fluctuates due to an imbalance of DC power inside the multi-terminal meshing flexible interconnection equipment; Accordingly, the energy storage unit is used to perform inertial regulation on the DC voltage.

[0030] In the embodiment of the present application, the DC voltage dynamics of the multi-terminal meshing flexible interconnection equipment is determined by the power at the DC bus, and its power balance equation can be expressed as formula (1).

[0031] (1) In the formula, ( ) is from Active power injection from VSC to the grid; It is the active power injection from the energy storage unit to the DC bus; It is the DC voltage of the multi-terminal meshed flexible interconnection equipment. It is a DC capacitor Capacitance value; It is the present moment.

[0032] Please see further Figure 2 In order to enhance the DC voltage stability of multi-terminal meshed flexible interconnection equipment, DC voltage control is divided into three levels: inertia regulation, primary voltage regulation and secondary voltage regulation. All converters participate in the above three stages to jointly regulate the DC voltage.

[0033] The inertia of DC voltage is understood as the ability to resist sudden changes in DC voltage. When the DC voltage fluctuates due to the imbalance of DC power inside the multi-terminal meshed flexible interconnection equipment, the DC capacitor Will be based on The signal discharges spontaneously or absorbs electrical energy, inertially adjusts the DC voltage, and thus provides DC voltage inertia. However, the capacity of the DC capacitor is limited. Therefore, virtual capacitor control is introduced in the energy storage unit, so that the DC capacitor and the energy storage unit jointly participate in the inertial adjustment link of the DC voltage, and quickly resist the change of the DC voltage.

[0034] Furthermore, in some embodiments, before the DC voltage reaches a rated DC voltage, the energy storage unit is used to: Adjust its output power and perform primary voltage regulation on the DC voltage; Accordingly, the AC / DC converter is used to adjust its output power and perform primary voltage regulation on the DC voltage.

[0035] In the embodiment of the present application, the primary voltage regulation is performed by an energy storage unit and a plurality of AC / DC converters (such as Figure 1 The first VSC, the second VSC and the third VSC in the DC voltage rating are involved. The deviation between ) , when the DC voltage does not reach the DC voltage rating The energy storage unit and AC / DC converter automatically adjust their output power to reduce the unbalanced power at the DC bus. The primary voltage regulation link no longer works.

[0036] Further, in some embodiments, when the absolute value of the deviation between the DC voltage and the rated value of the DC voltage is greater than the voltage dead zone set by the control unit, the control unit is used to perform secondary voltage regulation on the DC voltage.

[0037] In the embodiment of the present application, the secondary voltage regulation link occurs after the DC voltage fluctuates significantly. It is achieved by a control unit inside the multi-terminal meshing flexible interconnection equipment. Greater than the voltage dead zone set by the control unit When the secondary voltage regulation link in the control unit is triggered, the DC voltage is regulated by the secondary voltage.

[0038] Furthermore, in some embodiments, when the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to the DC power imbalance inside the multi-terminal meshed flexible interconnection equipment, the DC capacitor is also used to discharge or absorb electric energy to perform inertial regulation of the DC voltage. Accordingly, the energy storage unit is also used to perform inertial regulation of the DC voltage according to the first control signal, and the first control signal is generated according to the control strategy of the DC / DC converter.

[0039] In an embodiment of the present application, the inertial regulation of the DC voltage includes inertial regulation of the DC voltage by spontaneous discharge or absorption of electrical energy by a DC capacitor; and inertial regulation of the DC voltage by controlling the energy storage unit through a control signal (i.e., a first control signal) of the energy storage unit.

[0040] The first control signal of the energy storage unit is generated according to the control strategy of the DC / DC converter. The first control signal may be a pulse width modulation (PWM) signal.

[0041] In the embodiment of the present application, the method for obtaining the control strategy of the DC / DC converter may include: Determine the active power reference value output by the energy storage unit according to the active power command value sent by the control unit to the energy storage unit, the primary voltage regulation coefficient, the capacitance value of the virtual capacitor introduced by the energy storage unit, the rated voltage and the DC voltage; According to the active power reference value, the control strategy of the DC / DC converter is determined.

[0042] Specifically, the energy storage unit is integrated on the DC side of the equipment through a DC / DC converter. In order to achieve the spontaneous participation of inertia regulation and primary voltage regulation, the control strategy of the DC / DC converter consists of three parts: constant power control, primary voltage regulation control and inertia control. The control strategy of the DC / DC converter is as follows: Figure 3 shown.

[0043] The active power reference value output by the energy storage unit is shown in formula (2). When the DC voltage of the multi-terminal meshed flexible interconnection equipment decreases, due to the positive ( ) and negative , the energy storage unit will spontaneously increase its output power and participate in the DC voltage regulation of multi-terminal meshed flexible interconnected equipment.

[0044] (2) In the formula, It is the reference value of active power output by the energy storage unit; It is the power command value issued by the control unit to the DC / DC converter; is the primary voltage regulation coefficient; is the capacitance value of the virtual capacitor introduced by the energy storage unit, is the differential operator.

[0045] After obtaining the active power reference value output by the energy storage unit, a first control signal of the energy storage unit, ie, a PWM signal, is generated through two proportional integral (PI) controls.

[0046] Furthermore, in some embodiments, before the DC voltage reaches the rated value of the DC voltage, the energy storage unit is also used to spontaneously increase its output power according to the first control signal and perform a voltage regulation on the DC voltage. Correspondingly, the AC / DC converter is used to spontaneously reduce its corresponding output power according to the second control signal and perform a voltage regulation on the DC voltage. The second control signal is generated according to the control strategy of the AC / DC converter.

[0047] In the embodiment of the present application, based on the first control signal obtained as described above, the energy storage unit is controlled to spontaneously increase its output power, and a voltage regulation is performed on the DC voltage.

[0048] In order to realize the networking function of the networking flexible interconnection equipment and the primary voltage regulation of the DC voltage, all VSCs are controlled by a virtual synchronous generator (VSG) with primary voltage regulation. The control strategy is as follows: Figure 4 As shown. The control strategy consists of three parts: primary voltage regulation control, swing equation and active power-voltage (QU) control. The swing equation and QU control use the typical VSG control structure to ensure that the AC ports of the grid-forming flexible interconnection equipment have independent grid-forming capabilities; the primary voltage regulation control enables the VSC to spontaneously respond to the deviation between the DC voltage and the rated DC voltage, and participate in the hierarchical DC voltage regulation of the grid-forming flexible interconnection equipment.

[0049] The control equation of VSC is shown in formula (3). When the DC voltage of the grid-type flexible interconnection equipment decreases, VSC can ) spontaneously reduces its corresponding output power, thereby avoiding the continuous decrease of the DC voltage of the meshing flexible interconnection equipment and participating in DC voltage regulation.

[0050] (3) In the formula, is the primary voltage regulation control coefficient; is the fictitious inertia coefficient; is a differential operator; is the damping coefficient; is the output voltage angular frequency of the VSC; is the rated angular frequency, taken as 100pi; is the internal potential of VSC; is the integral coefficient of reactive power-voltage (QU) control; It is the reactive power command value issued by the control unit to the VSC; is the reactive power output by the VSC; It is the active power command value issued by the control unit to the VSC; is the active power output by the VSC; is the voltage deviation coefficient; is the rated value of the VSC output voltage; is the actual value of the VSC output voltage; is the output VSC modulation voltage phase.

[0051] In the embodiment of the present application, the control strategy of each AC / DC converter may be obtained by: The control strategy of each AC / DC converter is determined according to the internal potential and modulation voltage phase corresponding to each AC / DC converter.

[0052] Specifically, the control strategy of each AC / DC converter is based on the internal potential corresponding to each AC / DC converter. and modulation voltage phase Sure.

[0053] Furthermore, the VSC output three-phase voltage reference value is obtained, as shown in formula (4).

[0054] (4) In the formula, , , They are the three-phase voltage reference values ​​output by VSC respectively.

[0055] A control signal (ie, a second control signal) for controlling the AC / DC converter is generated according to the three-phase voltage reference value output by the VSC. The second control signal is also a PWM signal.

[0056] Based on each second control signal, the corresponding AC / DC converter is controlled to spontaneously reduce the output power corresponding to each AC / DC converter, thereby completing a primary voltage regulation of the DC voltage.

[0057] Further, in some embodiments, when the absolute value of the deviation between the DC voltage and the rated value of the DC voltage is greater than the voltage dead zone set by the control unit, the control unit is further configured to: According to the deviation, a power deviation reference value at the DC bus is obtained; According to the rated capacity of each AC / DC converter in grid-connected operation, determine the power deviation reference value portion at the DC bus that each AC / DC converter in grid-connected operation needs to bear; According to the power deviation part at the DC bus that each AC / DC converter in grid operation needs to bear, the active power command value sent to each AC / DC converter in grid operation is determined to perform secondary voltage regulation on the DC voltage.

[0058] In the embodiment of the present application, the power deviation at the DC bus is as shown in formula (5): (5) In the formula, is the power deviation reference value at the DC bus; and are the proportional coefficient and the integral coefficient respectively.

[0059] Subsequently, each VSC connected to the grid will jointly bear the DC bus power deviation reference value according to its rated capacity, thereby achieving error-free regulation of the DC voltage of the multi-terminal meshed flexible interconnected equipment.

[0060] When all VSCs (i.e., AC / DC converters) are connected to the grid, the active power command values ​​of multiple VSCs are updated as follows: (6) in, ( ) is the active power command value issued by the control unit to the first VSC, the second VSC and the third VSC in grid-connected operation; is the active power command value before updating; ( ) is the rated capacity of the first VSC, the second VSC and the third VSC ( ) related unbalanced power coefficient, satisfying formula (7): (7) When any converter exits grid-connected operation or the feeder connected to it loses power, the remaining converters that are normally connected to the grid participate in secondary voltage regulation. Taking the feeder connected to the first VSC as an example, the active power command value sent by the control unit to the second VSC and the third VSC is updated as follows: (8) For example, based on Figure 1 The multi-terminal meshed flexible interconnection equipment shown in the figure verifies the DC voltage hierarchical control method of the multi-terminal meshed flexible interconnection equipment provided in the present application. At 3 seconds, the first feeder is powered off. Figure 5 It shows the grid voltage waveform established by the first VSC, and the microgrid voltage is 1.0 pu; Figure 6 It shows the DC voltage waveform of the multi-terminal meshed flexible interconnection equipment when the first VSC exits operation.

[0061] The hierarchical control method for DC voltage of multi-terminal meshed flexible interconnected equipment provided in the embodiment of the present application is different from the traditional flexible interconnected equipment based on the master-slave control structure. After a fault occurs on the main converter side or it exits operation, the DC voltage of the entire equipment will lose stability. The method includes three parts: inertia regulation, primary voltage regulation and secondary voltage regulation. After the DC voltage fluctuates: the energy storage unit and the DC capacitor can resist the rapid change of the DC voltage through inertia regulation; the energy storage unit and the VSC (i.e., the AC / DC converter) can change their output power through the primary voltage regulation link, thereby participating in the DC voltage regulation of the multi-terminal meshed flexible interconnected equipment; the secondary voltage regulation link is used to achieve the differenceless regulation of the DC voltage. Multiple converters jointly participate in the DC voltage control of the multi-terminal meshed flexible interconnected equipment, avoiding the excessive dependence of the multi-terminal meshed flexible interconnected equipment on the operating status of a single converter, and can still maintain the stability of the DC voltage after a fault occurs on any converter side or it exits operation.

[0062] The following describes the DC voltage hierarchical control method for multi-terminal meshed flexible interconnection equipment provided in the present application. The DC voltage hierarchical control method for multi-terminal meshed flexible interconnection equipment described below can be applied to the multi-terminal meshed flexible interconnection equipment described above.

[0063] See also Figure 7 The DC voltage hierarchical control method for multi-terminal meshed flexible interconnection equipment provided in an embodiment of the present application may include: step 110, step 120 and step 130.

[0064] Step 110: When the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to an imbalance of the DC power inside the multi-terminal meshed flexible interconnection equipment, the DC voltage is inertially adjusted through the DC capacitor and the energy storage unit inside the multi-terminal meshed flexible interconnection equipment; Step 120: Before the DC voltage reaches the rated value of the DC voltage, the DC voltage is regulated by the energy storage unit and the multiple AC / DC converters to spontaneously adjust their output power; In step 130 , when the absolute value of the deviation between the DC voltage and the rated value of the DC voltage is greater than the voltage dead zone set by the control unit, the control unit performs secondary voltage regulation on the DC voltage.

[0065] The hierarchical control method for DC voltage of multi-terminal meshed flexible interconnected equipment provided in the embodiment of the present application is different from the traditional flexible interconnected equipment based on the master-slave control structure. After a fault occurs on the main converter side or it exits operation, the DC voltage of the entire equipment will lose stability. The method includes three parts: inertia regulation, primary voltage regulation and secondary voltage regulation. After the DC voltage fluctuates: the energy storage unit and the DC capacitor can resist the rapid change of the DC voltage through inertia regulation; the energy storage unit and the VSC (i.e., the AC / DC converter) can change their output power through the primary voltage regulation link, thereby participating in the DC voltage regulation of the multi-terminal meshed flexible interconnected equipment; the secondary voltage regulation link is used to achieve the differenceless regulation of the DC voltage. Multiple converters jointly participate in the DC voltage control of the multi-terminal meshed flexible interconnected equipment, avoiding the excessive dependence of the multi-terminal meshed flexible interconnected equipment on the operating status of a single converter, and can still maintain the stability of the DC voltage after a fault occurs on any converter side or it exits operation.

[0066] It can be understood that the detailed functional implementation of each of the above-mentioned units / modules can be found in the introduction of the aforementioned method embodiment, and will not be repeated here.

[0067] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the device are similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method, which will not be repeated here.

[0068] Based on the method in the above embodiment, the present application embodiment provides an electronic device, see Figure 8 The electronic device may include: a processor (Processor) 810, a communication interface (Communications Interface) 820, a memory (Memory) 830 and a communication bus 840, wherein the processor 810, the communication interface 820, and the memory 830 communicate with each other through the communication bus 840. The processor 810 may call the logic instructions in the memory 830 to execute the method in the above embodiment.

[0069] In addition, the logic instructions in the above-mentioned memory 830 can be implemented in the form of software functional units and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application.

[0070] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0071] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0072] It is understandable that the processor in the embodiment of the present application may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0073] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0074] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented by software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions may be transmitted from a website site, computer, server or data center to another website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state drive (SSD)), etc.

[0075] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0076] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A multi-terminal networking type flexible interconnection equipment, characterized in that: include: Inverter, energy storage unit and control unit; The converter includes a bidirectional DC / DC converter and multiple AC / DC converters, each AC / DC converter is connected to a feeder, the low-voltage side of the bidirectional DC / DC converter is connected to the energy storage unit, the DC sides of the converters are cascaded and connected to the same DC bus, and the control unit is used to control the multiple AC / DC converters to supply power to the loads on each feeder when any feeder has an unplanned power outage.

2. The multi-terminal networking type flexible interconnection equipment according to claim 1, characterized in that: Also includes: A DC capacitor connected to the AC / DC converter, wherein when the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to an imbalance of DC power inside the multi-terminal meshed flexible interconnection equipment, the DC capacitor is used to inertially adjust the DC voltage; Correspondingly, the energy storage unit is used to perform inertial regulation on the DC voltage.

3. The multi-terminal networking type flexible interconnection equipment according to claim 1, characterized in that: Before the DC voltage reaches a rated DC voltage value, the energy storage unit is used to: adjusting its output power and performing a primary voltage regulation on the DC voltage; Correspondingly, the AC / DC converter is used to adjust its output power and perform a primary voltage regulation on the DC voltage.

4. The multi-terminal networking type flexible interconnection equipment according to claim 1, characterized in that: In a case where an absolute value of a deviation between the DC voltage and the rated value of the DC voltage is greater than a voltage dead zone set by the control unit, the control unit is configured to perform secondary voltage regulation on the DC voltage.

5. The multi-terminal networking type flexible interconnection equipment according to claim 2, characterized in that: When the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to an imbalance in the DC power inside the multi-terminal meshed flexible interconnection equipment, the DC capacitor is also used to discharge or absorb electric energy to perform inertial regulation on the DC voltage. Accordingly, the energy storage unit is also used to perform inertial regulation on the DC voltage according to a first control signal, and the first control signal is generated according to a control strategy of the DC / DC converter.

6. The multi-terminal networking type flexible interconnection equipment as described in claim 3, characterized in that: Before the DC voltage reaches the rated value of the DC voltage, the energy storage unit is also used to spontaneously increase its output power according to the first control signal and perform a voltage regulation on the DC voltage. Correspondingly, the AC / DC converter is used to spontaneously reduce its corresponding output power according to the second control signal and perform a voltage regulation on the DC voltage. The second control signal is generated according to the control strategy of the AC / DC converter.

7. The multi-terminal networking type flexible interconnection equipment as described in claim 4, characterized in that: In a case where an absolute value of a deviation between the DC voltage and the rated value of the DC voltage is greater than a voltage dead zone set by the control unit, the control unit is further configured to: According to the deviation, obtaining a power deviation reference value at the DC bus; Determining, according to the rated capacity of each of the AC / DC converters in grid-connected operation, a power deviation reference value portion at the DC bus that each of the AC / DC converters in grid-connected operation needs to bear; According to the power deviation portion at the DC bus that each of the AC / DC converters in grid-connected operation needs to bear, the active power command value sent to each of the AC / DC converters in grid-connected operation is determined to perform secondary voltage regulation on the DC voltage.

8. A DC voltage hierarchical control method for multi-terminal meshing flexible interconnection equipment, characterized in that: The multi-terminal networking type flexible interconnection equipment as claimed in any one of claims 1 to 7 comprises: When the DC voltage of the multi-terminal meshed flexible interconnection equipment fluctuates due to an imbalance of DC power inside the multi-terminal meshed flexible interconnection equipment, inertial adjustment is performed on the DC voltage through the DC capacitor inside the multi-terminal meshed flexible interconnection equipment and the energy storage unit; Before the DC voltage reaches a rated value of the DC voltage, the energy storage unit and the plurality of AC / DC converters spontaneously adjust their output powers to perform a primary voltage regulation on the DC voltage; When an absolute value of a deviation between the DC voltage and the rated value of the DC voltage is greater than a voltage dead zone set by the control unit, the control unit performs secondary voltage regulation on the DC voltage.

9. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory, and when the program stored in the memory is executed, the processor is used to execute the method according to claim 8.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is run on a processor, the processor is caused to execute the method as claimed in claim 8.

Images