Flexible interconnection switch adaptive virtual inertia control method and system

Abstract

According to the flexible interconnection switch adaptive virtual inertia control method and system, a flexible interconnection switch comprises a series voltage source type converter, a parallel voltage source type converter and a battery energy storage system, the parallel voltage source type converter adopts virtual synchronous motor control, and the virtual synchronous motor control comprises an active frequency ring and a reactive voltage ring; the method comprises the following steps: step 1, obtaining the sum of active power output by a series voltage source type converter and a parallel voltage source type converter as active power injected by a battery energy storage system; step 2, determining the SOC of the battery energy storage system; step 3, adjusting the active self-adaptive virtual inertia in the active frequency loop and the reactive self-adaptive virtual inertia in the reactive voltage loop according to the SOC; and 4, updating the active power output by the parallel voltage source converter and the active power injected by the battery energy storage system, and returning to the step 2. According to the invention, the problem of coordinated operation control of the series and parallel converters in the flexible interconnection switch is solved.

Description

Technical Field

[0001] This invention relates to the field of flexible interconnection and intelligent control technology for power distribution networks, specifically an adaptive virtual synchronous machine inertia control method and system for flexible interconnection switches (Soft Open Point, SOP). Background Technology

[0002] With the increasing proportion of distributed renewable energy generation in grid power generation, virtual synchronous generator (VSG) technology, which enables grid-friendly connection of distributed renewable energy sources such as wind and solar power and droop inertia control, will be an inevitable development trend for distributed renewable energy grid connection in the future. Therefore, it has become one of the research hotspots for high-proportion distributed renewable energy grid connection. Virtual synchronous generators can be divided into two types: power plant type and unit type. The power plant type refers to connecting to the power system at the power plant's grid connection point, simulating the synchronous external characteristics of the entire power plant; currently, this specifically refers to energy storage virtual synchronous generators. The unit type is mainly used for connecting distributed energy sources such as photovoltaics and wind turbines to the grid. In recent years, research has focused more on distributed and unit-type virtual synchronous generators, with less attention paid to the power plant type.

[0003] In existing technologies, wind turbines can achieve inertial stability by utilizing rotor kinetic energy or reserving backup capacity. However, the former relies on rotor kinetic energy and can only increase active power output for a limited time, while the latter may result in significant power generation losses, leading to poor economic efficiency and failing to meet the current requirement for full grid integration of distributed renewable energy while ensuring power supply security. Currently, the most common virtual synchronous machine algorithms for photovoltaic and wind turbines mostly involve adding electrochemical energy storage or supercapacitors to the DC bus between their converters to achieve inertial support of the power system from distributed renewable energy, adjusting the voltage amplitude and frequency at the grid connection point, and realizing virtual synchronous control of individual distributed renewable energy units. However, upgrading current wind turbines or photovoltaic power plants to unit-based virtual synchronous machine algorithms according to the above-mentioned solutions requires shutting down each independent power generation unit and adding an energy storage unit one-to-one, which is cumbersome and costly. Therefore, there is an urgent need for a power plant-based virtual synchronous machine solution for large-scale wind and solar power plants to achieve grid-friendly integration of distributed renewable energy.

[0004] Meanwhile, as the highest-performing representative in the field of flexible alternating current transmission systems (FACTS), the Soft Open Point (SOP) can regulate line power flow, voltage support, and system damping by controlling multiple electrical parameters, such as voltage amplitude and phase, thereby improving steady-state and transient stability. Adding energy storage devices, primarily battery-based, to the common DC bus of the SOP allows for greater transmission capacity and network control functions at a relatively low cost, increasing the SOP's attractiveness to power companies, transmission operators, and distributed renewable energy operators. On the other hand, by fully utilizing the controllable and adjustable voltage amplitude and phase of the SOP's series and parallel outputs, upgrading traditional SOPs with virtual synchronous machine algorithms can avoid the drawbacks of unit-based virtual synchronous machine modifications, further reducing the cost of distributed renewable energy transformation. Simultaneously, due to the isolation effect of the SOP, the voltage at the distributed renewable energy access point remains relatively stable, reducing its requirements for grid adaptability and fault ride-through capability. However, current research on VSG control strategies mainly focuses on the operating conditions of a single converter. If the VSG algorithm is introduced into the SOP, more attention needs to be paid to the coordinated operation and control of the series and parallel converters in the SOP; and research in this area is currently lacking. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a flexible interconnected switch adaptive virtual inertia control method and system, which solves the problem of coordinated operation and control of series and parallel converters in SOP, enabling it to have the frequency and voltage support capabilities of a traditional virtual synchronous machine without changing the original control of the new energy power generation device.

[0006] The present invention adopts the following technical solution.

[0007] This invention proposes an adaptive virtual inertia control method for flexible interconnected switches. The flexible interconnected switch includes a series voltage source converter and a parallel voltage source converter connected via a DC bus. The battery energy storage system is connected in parallel with the supporting capacitor of the DC bus. The parallel voltage source converter adopts virtual synchronous motor control, which includes an active frequency loop and a reactive voltage loop. The methods include: Step 1: Obtain the sum of the active power output by the series voltage source converter and the active power output by the parallel voltage source converter as the active power injected into the battery energy storage system. Step 2: Determine the SOC of the battery energy storage system based on the active power injected into the battery energy storage system; Step 3: Adjust the active adaptive virtual inertia in the active frequency loop and the reactive adaptive virtual inertia in the reactive voltage loop according to the SOC of the battery energy storage system. Step 4: Based on the adjusted virtual synchronous motor control, update the active power output of the parallel voltage source converter and the active power injected by the battery energy storage system, and return to step 2.

[0008] Preferably, the outer loop control of the series voltage source converter adopts harmonic voltage tracking suppression, and the inner loop control adopts active filter control.

[0009] Preferably, the active adaptive virtual inertia in the active frequency loop is as shown in the following formula:

[0010] In the formula, For dynamic time-active adaptive virtual inertia, This is the virtual inertia at steady state. This represents the disturbance value of active power near the steady-state point. The value of the angular velocity near the steady-state point is the disturbance value. The active damping coefficient is... The rated angular frequency, This represents the maximum difference between the actual angular velocity and the rated angular velocity. This is the inertia adjustment coefficient.

[0011] Preferably, the reactive adaptive virtual inertia in the reactive voltage loop is as shown in the following formula:

[0012] In the formula, For dynamic reactive adaptive virtual inertia, This is the virtual inertia at steady state. This represents the reactive power disturbance value near the steady-state point. The rated port voltage, This represents the maximum difference between the actual port voltage and the rated port voltage. This is the inertia adjustment coefficient.

[0013]

[0014] In the formula, , These are the minimum and maximum values ​​of the inertia adjustment coefficient, respectively. This refers to the state of charge of the battery energy storage system.

[0015] This invention also proposes a flexible interconnected switch adaptive virtual inertia control system, in which the parallel voltage source converter adopts virtual synchronous motor control, which includes an active frequency loop and a reactive voltage loop. The system includes: The power monitoring module is used to obtain the sum of the active power output by the series voltage source converter and the active power output by the parallel voltage source converter as the active power injected into the battery energy storage system. The SOC monitoring module is used to determine the SOC of the battery energy storage system based on the active power injected into the battery energy storage system. The adaptive virtual inertia adjustment module is used to adjust the active adaptive virtual inertia in the active frequency loop and the reactive adaptive virtual inertia in the reactive voltage loop according to the SOC of the battery energy storage system.

[0016] The power monitoring module is also used to update the active power output of the parallel voltage source converter and the active power injected by the battery energy storage system based on the adjusted virtual synchronous motor control.

[0017] The adaptive virtual inertia adjustment module includes an active adaptive virtual inertia calculation unit; The active adaptive virtual inertia calculation unit calculates the active adaptive virtual inertia in the active frequency loop according to the following relationship:

[0018] In the formula, For dynamic time-active adaptive virtual inertia, This is the virtual inertia at steady state. This represents the disturbance value of active power near the steady-state point. The value of the angular velocity near the steady-state point is the disturbance value. The active damping coefficient is... The rated angular frequency, This represents the maximum difference between the actual angular velocity and the rated angular velocity. This is the inertia adjustment coefficient.

[0019] The adaptive virtual inertia adjustment module includes a reactive adaptive virtual inertia calculation unit; The reactive adaptive virtual inertia calculation unit calculates the reactive adaptive virtual inertia in the reactive voltage loop according to the following relationship:

[0020] In the formula, For dynamic reactive adaptive virtual inertia, This is the virtual inertia at steady state. This represents the reactive power disturbance value near the steady-state point. The rated port voltage, This represents the maximum difference between the actual port voltage and the rated port voltage. This is the inertia adjustment coefficient.

[0021] The adaptive virtual inertia adjustment module includes an inertia adjustment coefficient calculation unit; The inertia adjustment coefficient calculation unit calculates the inertia adjustment coefficient according to the following formula:

[0022] In the formula, , These are the minimum and maximum values ​​of the inertia adjustment coefficient, respectively. This refers to the state of charge of the battery energy storage system.

[0023] The present invention is also a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0024] The present invention is also a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0025] The beneficial effects of this invention are as follows, compared with the prior art, at least including the following: The virtual synchronization control strategy for flexible interconnected switches, based on the SOP system operation scheme with energy storage capacity, establishes an SOP power mathematical model, and simulates traditional virtual synchronous generator units. Without external modifications, only the original converter control of the new energy power generation is modified to achieve a virtual synchronization control strategy suitable for SOPs. Furthermore, based on the VSG small-signal model, an adaptive control strategy for rotational inertia is proposed, which adaptively adjusts the rotational inertia to automatically reduce system overshoot and oscillation, thereby improving the stability of active power and frequency in the distribution network. Attached Figure Description

[0026] Figure 1 This is a diagram of the SOP system operation architecture equipped with energy storage function in an embodiment of the present invention.

[0027] Figure 2 This is an equivalent circuit diagram of a power transmission system with SOP-BESS in an embodiment of the present invention.

[0028] Figure 3 This is a schematic diagram of the harmonic voltage detection principle in an embodiment of the present invention.

[0029] Figure 4 This is a block diagram of the SEC control in an embodiment of the present invention.

[0030] Figure 5 This is a block diagram of the virtual synchronizer control of the SOP in this embodiment of the invention.

[0031] Figure 6 This is the control result of the distribution network voltage and current in the embodiments of the present invention.

[0032] Figure 7This is the control result of the DC bus voltage in the embodiment of the present invention.

[0033] Figure 8 This is the result of controlling the system frequency in the embodiments of the present invention.

[0034] Figure 9 This refers to the SHC output power in this embodiment of the invention.

[0035] Figure 10 This refers to the active adaptive virtual inertia in this embodiment of the invention.

[0036] Figure 11 This refers to the reactive adaptive virtual inertia in this embodiment of the invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0038] SOP system operation architecture with energy storage function, such as Figure 1 As shown, under normal operating conditions, distributed renewable energy units transmit the generated power to the remote AC grid. When renewable energy generation is excessive or insufficient, the energy storage battery system will perform energy absorption or differential compensation functions respectively to ensure stable power supply to the load center. The flexible interconnection switch adopts a unified power quality regulator-based implementation scheme, which consists of three core components: a series converter (SEC), a shunt converter (SHC), and a battery energy storage system (BESS) integrated into the common DC bus. Specifically, the SEC is connected in series between nodes M1 and M2 via a series transformer, while the SHC is directly connected in parallel to node M2. The BESS is connected in parallel with the supporting capacitor of the common DC bus via a bidirectional DC / DC converter. Its core functions include maintaining bus voltage stability and controlling the charging and discharging of the energy storage device. This topology ensures both power quality regulation capability and dynamic energy balance management.

[0039] After detecting and extracting the harmonic voltage at node M1, the SOP can use the SEC to generate a harmonic voltage of equal magnitude but opposite direction to cancel the harmonic voltage generated by the harmonic source, thus ensuring the voltage quality of the power grid. The SHC is controlled as a sinusoidal voltage source, making the output voltage of the distributed renewable energy source a standard sinusoidal value. Since the voltage source has a small impedance to the harmonic current, the grid harmonic current flows into the parallel converter, thereby canceling the harmonic current and making the current flowing to the grid close to the sinusoidal value. The voltage amplitude, phase, and frequency at the parallel connection of the SOP are all used as controllable electrical quantities to control the coordination between the SOP and the distributed renewable energy source, simulating the dynamic response capability of the traditional virtual synchronous machine to the grid voltage and frequency. Based on this, a research approach for a field-mounted virtual synchronous machine is provided, which can autonomously maintain the stability of the power grid and the power quality without shutting down and modifying existing wind turbine units.

[0040] This invention provides an adaptive virtual inertia control method for a flexible interconnected switch. The flexible interconnected switch includes: a series voltage source converter, a parallel voltage source converter, and an energy storage battery. Control methods include: Step 1: Obtain the sum of the active power output from the series voltage source converter and the active power output from the parallel voltage source converter as the active power injected into the battery energy storage system.

[0041] Establish the equivalent circuit of the power transmission system configured with flexible interconnection switches; Figure 2 This is an equivalent circuit diagram of a power transmission system with SOP-BESS in an embodiment of the present invention. Considering the harmonic suppression effect of the system filtering devices, a simplified model of the SOP-BESS power transmission system under the power frequency components of AC voltage and current is established. This indicates the line impedance between the output terminal of the SOP series-connected transformer and the distribution network. , These are the voltage amplitudes of the distribution network and distributed renewable energy sources, respectively. , These represent the voltage phases of the distribution network and distributed renewable energy sources, respectively. , These are the voltage amplitudes at nodes M1 and M2, respectively. , These represent the voltage phases of nodes M1 and M2, respectively. , These are the output voltage amplitudes of SEC and SHC, respectively. , The output voltage phases of SEC and SHC are respectively; the equivalent impedance of the SOP series section. Including: the equivalent impedance of a series transformer Line impedance between SOP series and parallel ports and the output impedance of the SEC Equivalent impedance of the parallel section of SOP Including: SHC output impedance ; For the line between the SOP series output terminal and the series transformer, and the equivalent output impedance of the series voltage source converter, These are the line impedance between the SOP series-side output terminal and the series-side transformer, and the equivalent output impedance of the parallel voltage source converter, respectively. , , , These are the active power, reactive power, and apparent power transmitted to the distribution network, respectively. , , , These are the active power, reactive power, and apparent power output by distributed renewable energy sources, respectively. , , , These are the active power, reactive power, and apparent power output by the SEC, respectively. , , , These are the active power, reactive power, and apparent power output by SHC, respectively. , Active power injected into the battery energy storage system.

[0042] Based on the equivalent circuit, the power flow from distributed renewable energy sources to the distribution network, the output power of the parallel voltage source converter, and the active power injected by the battery energy storage system are determined.

[0043] Considering only the case where the SOP is placed at the outlet of the distributed renewable energy source, to reduce the complexity of system analysis, the power flow from the distributed renewable energy source to the distribution network can be obtained, as shown in the following equation: (1) Equation (1) shows that the output power from node M2 ​​through the main feeder line is There are two destinations; one part is the power exchanged with the SOP series section. Another portion is transmitted to the distribution network via transmission lines. - This also includes impedance losses on long-distance transmission lines. ; like Figure 2 As shown, the SOP series unit can be equivalent to a controllable voltage source and an equivalent output impedance in steady state. The equivalent model is shown below, where the amplitude and phase parameters of the voltage source are controlled and adjusted; the parallel unit of SOP is equivalent to a similar power supply impedance model; the power model of SHC output is shown below: (2) Once the DC bus voltage is stabilized, the DC / DC converter and battery can be used as ideal energy storage sources to balance power differences. Therefore, the DC / DC converter section will not be analyzed further, and only its basic power model will be provided. In the battery energy storage system, the bidirectional DC / DC power converter, SEC, and SHC are electrically coupled via a shared DC bus. This architecture not only undertakes the core function of maintaining stable DC-side voltage at the start of operation (SOP), but also provides necessary real-time active power compensation for the two parallel-connected converter units. This energy interaction hub structure achieves dynamic power balance within the system through a coordinated control strategy.

[0044] Therefore, the DC connection in this part can be simplified to an algebraic relationship between active power, and assuming that the power flowing into the battery energy storage system is positive, the active power injected into the battery energy storage system can be obtained as follows: (3) Equation (3) holds true for energy storage systems on a common DC bus of any topology or form.

[0045] The above analysis clearly shows that properly controlling the output voltage amplitude and phase of SEC and SHC is the key to controlling power flow and also the key to realizing SOP virtual synchronization control.

[0046] Among them, the outer loop control of the series voltage source converter adopts harmonic voltage tracking suppression, and the inner loop control adopts active filter control.

[0047] In this embodiment, the capacitor voltage and filter inductor current output by the SEC are used as feedback quantities. The outer voltage loop uses a proportional element to track harmonic voltages, and the inner loop uses a proportional element to improve the dynamic response of the active filter system. When a series active filter is working, it first needs to accurately detect the harmonic voltage to be compensated. Then, by controlling the SEC, a compensation signal with the opposite direction and equal magnitude to the harmonic voltage is generated to cancel the harmonic voltage. In the end, the harmonics in the network are compensated, and the voltage and current waveforms are close to sine waves.

[0048] like Figure 3 As shown, the detected three-phase grid voltage The phase angle of the grid voltage is obtained after control by a phase-locked loop (PLL). , Three-phase harmonic voltage , , After abc-dq0 transformation ( Convert to DC , The fundamental component was obtained by filtering out harmonics after passing the signal through a low-pass filter (LPF). , Then, after inverse coordinate transformation ( After being restored to the three-phase fundamental voltage, the original three-phase harmonic voltage is subtracted from the three-phase fundamental voltage to obtain the three-phase harmonic voltage. , , ; like Figure 4 As shown, harmonic voltage With the capacitor voltage output by SEC The voltage difference, the current obtained after the voltage difference is controlled by the outer voltage loop, and then the current of the filter inductor of the SEC are compared. The current difference is used to obtain the modulation voltage after current inner loop control and PWM modulation. The modulation voltage is compared with the capacitor voltage output by SEC. The voltage difference is filtered by the inductor. Obtain the filter inductor current , With fundamental current The current difference through the capacitor Obtain the capacitor voltage ;in, For voltage outer loop gain, For the inner current loop gain, For PWM gain; Among them, the parallel voltage source converter adopts virtual synchronous generator (VSG) control, which also uses instantaneous active power and instantaneous reactive power as the basic concepts to perform harmonic compensation correction on the reference value.

[0049] In the SOP, a control model for the VSG is constructed to accurately reproduce the mechanical-electrical coupling dynamic characteristics of the virtual synchronous machine at the grid interface. In the SOP architecture with integrated energy storage, its parallel compensation port needs to provide AC voltage stability support for distributed renewable energy grid connection points. Given this topology constraint, the SHC should be configured in virtual synchronous machine control mode. A suitable virtual synchronous machine control block diagram for the SOP is shown below. Figure 5 As shown, the active-frequency loop passes through the power grid reference frequency. Actual sampling frequency of the parallel port with SOP The frequency deviation is controlled by active frequency and then compared with the active power reference value output by the inverter on the parallel side of SOP. The sum, minus the active power transmitted by SOP through SHC. The reference active power input is used as the prime mover input to the second-order virtual synchronous machine model, ultimately yielding the voltage phase command for the parallel voltage source converter. The rated voltage amplitude of the reactive power-voltage loop through the power grid. Voltage amplitude at the parallel port of SOP The voltage deviation is controlled by reactive power and then compared with the reactive power reference value output by the inverter on the parallel side of SOP. The sum, minus the reactive power transmitted by SOP through SHC. The reference reactive power is input to the excitation model, and finally the voltage amplitude command of the parallel voltage source converter is obtained. .

[0050] The virtual synchronous machine algorithm uses a second-order model of a traditional synchronous generator to simulate the motion characteristics of the rotor, as shown in the following equation:

[0051] In the formula, For the virtual inertia of the rotor, This is the actual angular frequency of the power grid. The rated angular frequency, This is the difference between the actual angular frequency and the rated angular frequency of the power grid. The rated torque of the virtual synchronous machine, The actual torque of the virtual synchronous machine. The active damping coefficient is... Rated active power for the virtual synchro. This represents the actual active power of the virtual synchronizer. The rotation angle of the virtual synchronizer; Based on the small-signal assumption, the small-signal model of a system where active and reactive power are relatively independent can be obtained as shown in the following equation:

[0052] In the formula, , , , , , , These are the small disturbances near the DC operating point of the actual angular frequency of the power grid, the rated active power of the virtual synchronizing machine, the actual active power of the virtual synchronizing machine, the rotation angle of the virtual synchronizing machine, the output voltage of the virtual synchronizing machine, the rated reactive power of the virtual synchronizing machine, and the actual reactive power of the virtual synchronizing machine. This is the grid voltage. This refers to the line impedance between the virtual synchronizing machine and the grid connection point.

[0053] Step 2: Determine the SOC of the battery energy storage system based on the active power injected into the battery energy storage system.

[0054] Step 3: Adjust the active adaptive virtual inertia in the active frequency loop and the reactive adaptive virtual inertia in the reactive voltage loop according to the SOC of the battery energy storage system.

[0055] The SHC system, combined with VSG control, has the ability to automatically adjust and reduce system overshoot and oscillation by adjusting the moment of inertia of the control switch. When grid fluctuations are too large, adjusting the moment of inertia increases the system damping ratio, reduces power overshoot, and shortens the oscillation period, ensuring that the VSG system frequency remains within the allowable range.

[0056] The adaptive virtual inertia is improved as shown in the following equation:

[0057]

[0058]

[0059] In the formula, For dynamic time-active adaptive virtual inertia, For dynamic reactive adaptive virtual inertia, This is the virtual inertia at steady state. This represents the disturbance value of active power near the steady-state point. This represents the reactive power disturbance value near the steady-state point. The value of the angular velocity near the steady-state point is the disturbance value. The rated port voltage, This represents the maximum difference between the actual angular velocity and the rated angular velocity. The active damping coefficient is... This represents the maximum difference between the actual port voltage and the rated port voltage. This is the inertia adjustment coefficient, used to adjust the degree of influence of active power deviation and reactive power deviation on virtual inertia; To optimize control performance, The following control law is used for tuning:

[0060] In the formula, , These are the minimum and maximum values ​​of the inertia adjustment coefficient, respectively, and SOC is the state of charge (SOC) of the BESS. This control law enables the system to use less damping to quickly release energy and maintain a high-speed response to changes in system power when the BESS stores a high amount of energy; while when the BESS stores a low amount of energy, it rapidly increases system damping, reduces BESS power exchange, and improves system stability.

[0061] Step 4: Based on the adjusted virtual synchronous motor control, update the active power output of the parallel voltage source converter and the active power injected by the battery energy storage system, and return to step 2.

[0062] To verify the effectiveness of the proposed adaptive virtual synchronous machine inertia control strategy, an SOP system was established with parameters as shown in Table 2.

[0063] Table 2 Main parameters of the SOP simulation model

[0064] To test the proposed algorithm's ability to handle high-power load input, we set up the following scenario for testing: initially with a 200kW load, distributed renewable energy generation provides 100kW of power, and then 100kW of load power is input in 1 second. The control results of the method proposed in this invention on the voltage and current of the distribution network are as follows: Figure 6 As shown, Figure 6 The horizontal axis represents time (in seconds), the vertical axis of the upper waveform represents voltage (in V), and the vertical axis of the lower waveform represents current (in A). The control results of the method proposed in this invention on the DC bus voltage are as follows: Figure 7 As shown, Figure 7 The horizontal axis represents time (in seconds), and the vertical axis represents DC voltage Udc (in V). The control results of the method proposed in this invention on the system frequency are as follows: Figure 8 As shown, Figure 8 The horizontal axis represents time (in seconds), and the vertical axis represents the system frequency (in Hz). The SHC output power in the method proposed in this invention is as follows: Figure 9 As shown, Figure 9 The horizontal axis represents time (in seconds), and the vertical axis represents active power (in W). Figure 9 The reactive power in the middle is always close to 0; The method proposed in this invention includes an active adaptive virtual inertia, such as... Figure 10 As shown, Figure 10 The horizontal axis represents time (in seconds), and the vertical axis represents virtual inertia (in J). The reactive adaptive virtual inertia in the method proposed in this invention is as follows: Figure 11 As shown, Figure 11The horizontal axis represents time (in seconds), and the vertical axis represents virtual inertia (in J). The results show that the proposed strategy can effectively ensure the stability of the system voltage frequency, with fluctuations within the allowable range. The converter output power can follow the system power demand.

[0065] This invention also proposes a flexible interconnected switch adaptive virtual inertia control system. The parallel voltage source converter adopts virtual synchronous motor control, which includes an active frequency loop and a reactive voltage loop. The system includes: The power monitoring module is used to obtain the sum of the active power output by the series voltage source converter and the active power output by the parallel voltage source converter as the active power injected into the battery energy storage system. The SOC monitoring module is used to determine the SOC of the battery energy storage system based on the active power injected into the battery energy storage system. The adaptive virtual inertia adjustment module is used to adjust the active adaptive virtual inertia in the active frequency loop and the reactive adaptive virtual inertia in the reactive voltage loop according to the SOC of the battery energy storage system.

[0066] The power monitoring module is also used to update the active power output of the parallel voltage source converter and the active power injected by the battery energy storage system based on the adjusted virtual synchronous motor control.

[0067] The adaptive virtual inertia adjustment module includes an active adaptive virtual inertia calculation unit; The active adaptive virtual inertia calculation unit calculates the active adaptive virtual inertia in the active frequency loop according to the following relationship:

[0068] In the formula, For dynamic time-active adaptive virtual inertia, This is the virtual inertia at steady state. This represents the disturbance value of active power near the steady-state point. The value of the angular velocity near the steady-state point is the disturbance value. The active damping coefficient is... The rated angular frequency, This represents the maximum difference between the actual angular velocity and the rated angular velocity. This is the inertia adjustment coefficient.

[0069] The adaptive virtual inertia adjustment module includes a reactive adaptive virtual inertia calculation unit; The reactive adaptive virtual inertia calculation unit calculates the reactive adaptive virtual inertia in the reactive voltage loop according to the following relationship:

[0070] In the formula, For dynamic reactive adaptive virtual inertia, This is the virtual inertia at steady state. This represents the reactive power disturbance value near the steady-state point. The rated port voltage, This represents the maximum difference between the actual port voltage and the rated port voltage. This is the inertia adjustment coefficient.

[0071] The adaptive virtual inertia adjustment module includes an inertia adjustment coefficient calculation unit; The inertia adjustment coefficient calculation unit calculates the inertia adjustment coefficient according to the following formula:

[0072] In the formula, , These are the minimum and maximum values ​​of the inertia adjustment coefficient, respectively. This refers to the state of charge of the battery energy storage system.

[0073] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0074] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0075] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0076] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. An adaptive virtual inertia control method for a flexible interconnected switch, wherein the flexible interconnected switch includes a series voltage source converter and a parallel voltage source converter connected via a DC bus, and a battery energy storage system is connected in parallel with the supporting capacitor of the DC bus, wherein... The parallel voltage source converter employs virtual synchronous motor control, which includes an active frequency loop and a reactive voltage loop; its characteristic is that the method includes: Step 1: Obtain the sum of the active power output by the series voltage source converter and the active power output by the parallel voltage source converter as the active power injected into the battery energy storage system. Step 2: Determine the SOC of the battery energy storage system based on the active power injected into the battery energy storage system; Step 3: Adjust the active adaptive virtual inertia in the active frequency loop and the reactive adaptive virtual inertia in the reactive voltage loop according to the SOC of the battery energy storage system. Step 4: Based on the adjusted virtual synchronous motor control, update the active power output of the parallel voltage source converter and the active power injected by the battery energy storage system, and return to step 2.

2. The adaptive virtual inertia control method for flexible interconnected switches according to claim 1, characterized in that, The outer loop control of the series voltage source converter uses harmonic voltage tracking and suppression, while the inner loop control uses active filter control.

3. The adaptive virtual inertia control method for flexible interconnected switches according to claim 1, characterized in that, The active adaptive virtual inertia in the active frequency loop is shown in the following formula: In the formula, For dynamic time-active adaptive virtual inertia, This is the virtual inertia at steady state. This represents the disturbance value of active power near the steady-state point. The value of angular velocity near the steady-state point is the disturbance value. The active damping coefficient is... The rated angular frequency, This represents the maximum difference between the actual angular velocity and the rated angular velocity. This is the inertia adjustment coefficient.

4. The adaptive virtual inertia control method for flexible interconnected switches according to claim 3, characterized in that, The reactive adaptive virtual inertia in the reactive voltage loop is shown in the following formula: In the formula, For dynamic reactive adaptive virtual inertia, This is the virtual inertia at steady state. This represents the reactive power disturbance value near the steady-state point. The rated port voltage, This represents the maximum difference between the actual port voltage and the rated port voltage. This is the inertia adjustment coefficient.

5. The adaptive virtual inertia control method for flexible interconnected switches according to claim 4, characterized in that, In the formula, , These are the minimum and maximum values ​​of the inertia adjustment coefficient, respectively. This refers to the state of charge of the battery energy storage system.

6. A flexible interconnected switch adaptive virtual inertia control system utilizing the method of any one of claims 1-5, wherein the parallel voltage source converter employs virtual synchronous motor control, the virtual synchronous motor control comprising an active frequency loop and a reactive voltage loop; characterized in that, The system includes: The power monitoring module is used to obtain the sum of the active power output by the series voltage source converter and the active power output by the parallel voltage source converter as the active power injected into the battery energy storage system. The SOC monitoring module is used to determine the SOC of the battery energy storage system based on the active power injected into the battery energy storage system. The adaptive virtual inertia adjustment module is used to adjust the active adaptive virtual inertia in the active frequency loop and the reactive adaptive virtual inertia in the reactive voltage loop according to the SOC of the battery energy storage system.

7. The flexible interconnected switch adaptive virtual inertia control system according to claim 6, characterized in that, The power monitoring module is also used to update the active power output of the parallel voltage source converter and the active power injected by the battery energy storage system based on the adjusted virtual synchronous motor control.

8. The flexible interconnected switch adaptive virtual inertia control system according to claim 6, characterized in that, The adaptive virtual inertia adjustment module includes an active adaptive virtual inertia calculation unit; The active adaptive virtual inertia calculation unit calculates the active adaptive virtual inertia in the active frequency loop according to the following relationship: In the formula, For dynamic time-active adaptive virtual inertia, This is the virtual inertia at steady state. This represents the disturbance value of active power near the steady-state point. The value of angular velocity near the steady-state point is the disturbance value. The active damping coefficient is... The rated angular frequency, This represents the maximum difference between the actual angular velocity and the rated angular velocity. This is the inertia adjustment coefficient.

9. The flexible interconnected switch adaptive virtual inertia control system according to claim 6, characterized in that, The adaptive virtual inertia adjustment module includes a reactive adaptive virtual inertia calculation unit; The reactive adaptive virtual inertia calculation unit calculates the reactive adaptive virtual inertia in the reactive voltage loop according to the following relationship: In the formula, For dynamic reactive adaptive virtual inertia, This is the virtual inertia at steady state. This represents the reactive power disturbance value near the steady-state point. The rated port voltage, This represents the maximum difference between the actual port voltage and the rated port voltage. This is the inertia adjustment coefficient.

10. The flexible interconnected switch adaptive virtual inertia control system according to claim 6, characterized in that, The adaptive virtual inertia adjustment module includes an inertia adjustment coefficient calculation unit; The inertia adjustment coefficient calculation unit calculates the inertia adjustment coefficient according to the following formula: In the formula, , These are the minimum and maximum values ​​of the inertia adjustment coefficient, respectively. This refers to the state of charge of the battery energy storage system.

11. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-5.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the program implements the steps of the method according to any one of claims 1-5.

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