Self-adaptive virtual inertia control system and method for UPQC

Abstract

The invention discloses a self-adaptive virtual inertia control system and method for a UPQC, and relates to the technical field of power distribution networks. A frequency voltage droop unit is used for applying active droop frequency control and reactive droop voltage control to a self-adaptive virtual synchronous machine; the self-adaptive virtual inertia calculation unit is used for determining a small disturbance quantity corresponding to actual active power, a small disturbance quantity corresponding to actual reactive power and a small disturbance quantity corresponding to actual frequency which are output by the self-adaptive virtual synchronous machine based on a virtual synchronous machine algorithm, active droop frequency control and reactive droop voltage control; and based on the small disturbance quantity corresponding to the actual active power, the small disturbance quantity corresponding to the actual reactive power and the small disturbance quantity corresponding to the actual frequency, a self-adaptive adjustment model of the virtual inertia is determined. The problems of power fluctuation and overcurrent in the transient process of traditional VSG control are effectively solved, better dynamic response is achieved, and the stability of the frequency and voltage of the independent microgrid is improved.

Description

Technical Field

[0001] The present invention relates to the field of power grid technology and can also be used in the field of virtual synchronous generator control technology, and in particular to an adaptive virtual inertia control system and method for UPQC. Background Art

[0002] As the proportion of distributed renewable energy in grid power generation continues to rise, virtual synchronous generator (VSG) technology, which enables "friendly" grid integration of distributed renewable energy sources such as wind and solar power, and droop inertia control, will be an inevitable development trend for future distributed renewable energy grid integration. Consequently, it has become a research hotspot for high-proportion distributed renewable energy grid integration. Furthermore, as a leading performer in the flexible AC transmission domain, the unified power quality conditioner (UPQC) can regulate line flow, voltage support, and system damping by controlling multiple electrical parameters, such as voltage amplitude and phase, to improve steady-state and transient stability.

[0003] Current research on VSG control strategies mainly focuses on the operating conditions of a single converter. However, if the VSG algorithm is introduced into UPQC, more attention needs to be paid to the coordinated operation control of the series and parallel converters in UPQC. However, research in this area is still blank.

[0004] This section is intended to provide a background or context to the embodiments of the invention that are recited in the claims. No statement herein is admitted to be prior art by virtue of its inclusion in this section. Summary of the Invention

[0005] In order to solve at least one of the technical problems mentioned in the above background technology section, this application proposes an adaptive virtual inertia control system and method for UPQC, which enables the new energy power generation device to have the frequency and voltage support capabilities of a traditional synchronous generator without changing the original control of the new energy power generation device.

[0006] In a first aspect, an embodiment of the present invention provides an adaptive virtual inertia control system for an UPQC, wherein the UPQC includes a series voltage source converter and a parallel voltage source converter. The adaptive virtual inertia control system includes: a frequency-voltage droop unit, an adaptive virtual synchronous machine, and an adaptive virtual inertia calculation unit, wherein:

[0007] The frequency and voltage droop unit is used to apply frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine;

[0008] The adaptive virtual inertia calculation unit is used to determine, based on a virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, the frequency control of the active power droop, and the voltage control of the reactive power droop, a small disturbance amount corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance amount corresponding to the actual reactive power, and a small disturbance amount corresponding to the actual frequency, and determine an adaptive adjustment model of the virtual inertia based on the small disturbance amount corresponding to the actual active power, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency. The adaptive adjustment model of the virtual inertia is as follows:

[0009]

[0010]

[0011] Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

[0012] In some optional aspects of this embodiment, the frequency-voltage droop unit includes a frequency droop subunit and a voltage droop subunit, wherein:

[0013] The frequency droop subunit is configured to apply the active power droop frequency control to the adaptive virtual synchronous machine based on the grid reference frequency, the actual frequency of the parallel voltage source converter port, the active power-frequency characteristic coefficient, the active power reference value output by the parallel voltage source converter, and the active power transmitted by the UPQC through the parallel voltage source converter;

[0014] The voltage droop subunit is used to apply reactive droop voltage control to the adaptive virtual synchronous machine based on the rated voltage amplitude of the power grid, the voltage amplitude of the port of the parallel voltage source converter, the reactive power-voltage amplitude characteristic coefficient, the reactive power reference value output by the parallel voltage source converter, and the reactive power transmitted by UPQC through the parallel voltage source converter.

[0015] In some optional aspects of this embodiment, the virtual synchronous machine algorithm uses a second-order model of a synchronous generator to establish a mathematical model for simulating the motion characteristics of the rotor. The expression corresponding to the virtual synchronous machine algorithm is:

[0016]

[0017] Where, is the virtual inertia of the rotor; 、 are respectively the actual frequency and the rated frequency of the adaptive virtual synchronous machine; is the deviation between the actual frequency and the rated frequency of the adaptive virtual synchronous machine; 、 are respectively the actual output torque and torque given value of the adaptive virtual synchronous machine; is the active damping coefficient; 、 are respectively the actual active power and the active power given value output by the adaptive virtual synchronous machine; Indicates the power angle.

[0018] In some optional aspects of this embodiment, the adaptive virtual inertia calculation unit is further configured to:

[0019] Determining an expression for a virtual electromotive force output by the adaptive virtual synchronous machine based on the voltage control of the reactive power droop;

[0020] Determine a steady-state equation of the adaptive virtual synchronous machine based on the frequency control of the active power droop, the expression of the virtual synchronous machine algorithm, the expression of the virtual electromotive force, the expression of the actual active power and the expression of the actual reactive power output by the adaptive virtual synchronous machine;

[0021] A disturbance is superimposed on the steady-state equation, and a Laplace transform is performed after disturbance separation and linearization to determine a small signal model corresponding to the adaptive virtual synchronous machine, wherein an expression of the small signal model includes a small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance function corresponding to the actual reactive power, a small disturbance function corresponding to the actual frequency, and a small disturbance function corresponding to the virtual electromotive force.

[0022] In some optional aspects of this embodiment, the expression of the virtual electromotive force is as follows:

[0023]

[0024] Where, is the virtual electromotive force of the adaptive virtual synchronous machine; is the no-load electromotive force of the adaptive virtual synchronous machine; is the reactive voltage droop regulating part of the virtual electromotive force; is the terminal voltage deviation of the adaptive virtual synchronous machine; is the reactive damping coefficient; 、 are respectively the actual reactive power and the reactive power set value output by the adaptive virtual synchronous machine; is the voltage excitation regulation coefficient; is the actual voltage at the machine end of the adaptive virtual synchronous machine.

[0025] In some optional aspects of this embodiment, the steady-state equation of the adaptive virtual synchronous machine is expressed as follows:

[0026]

[0027] Where, is the port voltage of the adaptive virtual synchronous machine; is the synchronous reactance of the adaptive virtual synchronous machine.

[0028] In some optional aspects of this embodiment, the expression of the small signal model is as follows:

[0029]

[0030] Where, They are respectively the small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, the small disturbance function corresponding to the actual reactive power, the small disturbance function corresponding to the actual frequency, the small disturbance function corresponding to the virtual electromotive force and the small disturbance function corresponding to the power angle; 、 They are respectively the active power given control quantity and reactive power given control quantity of the adaptive virtual synchronous machine; is a complex variable.

[0031] In some optional aspects of this embodiment, the adaptive virtual synchronous machine is connected to a control port of the parallel voltage source converter, and is configured to determine a voltage reference value and a phase angle reference value of the parallel voltage source converter based on the frequency voltage droop unit and the adaptive virtual inertia calculation unit, wherein the parallel voltage source converter is configured in a virtual synchronous generator control mode;

[0032] The adaptive virtual inertia control system further includes an SVPWM modulation unit for determining a pulse control signal for the parallel voltage source converter based on the voltage reference value and the phase angle reference value.

[0033] In some optional aspects of this embodiment, the UPQC further includes a bidirectional DC / DC converter and a battery energy storage device, wherein the battery energy storage device is connected in parallel with a DC capacitor of a common DC bus through the bidirectional DC / DC converter;

[0034] When the AC side frequency of the UPQC drops, the adaptive virtual synchronous machine extracts energy from the DC capacitor to provide inertia response, causing the voltage of the common DC bus to drop instantaneously. The bidirectional DC / DC converter adjusts the inductor current in real time through the voltage outer loop to control the charge and discharge power of the battery energy storage device, thereby providing voltage support for the DC capacitor.

[0035] The adaptive virtual inertia calculation unit is further configured to:

[0036] Based on the maximum current ramp rate of the ramp limiter in the battery energy storage device, the power synchronization coefficient, and the rated frequency of the adaptive virtual synchronous machine, a frequency step amplitude boundary required to trigger the ramp limiter is determined, wherein the frequency step amplitude boundary is expressed as follows:

[0037]

[0038] Based on the frequency step amplitude boundary, it is determined that the active adaptive virtual inertia satisfies the following constraints:

[0039]

[0040] Where, is the frequency step amplitude boundary; is the maximum current ramp rate; is the power synchronization coefficient; is the rated frequency of the adaptive virtual synchronous machine.

[0041] In a second aspect, an embodiment of the present application provides an adaptive virtual inertia control method for UPQC, comprising:

[0042] Constructing a UPQC system and a control model of an adaptive virtual synchronous machine in the UPQC system, wherein the UPQC system includes a series voltage source converter and a shunt voltage source converter, the adaptive virtual synchronous machine is connected to a port of the shunt voltage source converter, and is configured to configure the shunt voltage source converter to a virtual synchronous generator control mode;

[0043] Applying frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine;

[0044] Based on a virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, the frequency control of the active power droop, and the voltage control of the reactive power droop, a small disturbance amount corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance amount corresponding to the actual reactive power, and a small disturbance amount corresponding to the actual frequency are determined. Based on the small disturbance amount corresponding to the actual active power, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency, an adaptive regulation model of virtual inertia is determined to satisfy the following equation:

[0045]

[0046]

[0047] Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

[0048] An embodiment of the present invention provides an adaptive virtual inertia control system and method for UPQC. Through adaptive control, under the same conditions, the moment of inertia can be increased, effectively solving the power fluctuation and overcurrent problems of traditional VSG control during transient processes, with better dynamic response, and improved frequency and voltage stability of independent microgrids. Without changing the original control of the new energy power generation device, it enables the device to have the frequency and voltage support capabilities of a traditional synchronous generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0050] Figure 1 Schematic diagram of the structure of an adaptive virtual inertia control system for UPQC in an embodiment of the present invention;

[0051] Figure 2Schematic diagram of the structure of a UPQC with energy storage capability in an embodiment of the present invention;

[0052] Figure 3 A simplified schematic diagram of a UPQC-BESS power transmission system according to an embodiment of the present invention;

[0053] Figure 4 This is a schematic diagram of the harmonic voltage detection principle in an embodiment of the present invention;

[0054] Figure 5 SEC active filter control block diagram in an embodiment of the present invention;

[0055] Figure 6 This is a block diagram of a virtual synchronous generator control system applicable to UPQC in an embodiment of the present invention;

[0056] Figure 7 4 is a flow chart of an adaptive virtual inertia control method for UPQC in an embodiment of the present invention. DETAILED DESCRIPTION

[0057] To make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0058] Virtual synchronous generators can be divided into two types: power station type and unit type. The power station type refers to connecting to the power system at the power station grid connection point, simulating the synchronous external characteristics of the entire power station. Currently, it only refers to energy storage virtual synchronous machines; the unit type is mainly used for distributed energy such as photovoltaics and wind turbines to connect to the power grid. In recent years, research has focused on the field of distributed and unitized virtual synchronous generators, and few scholars have studied the power station type.

[0059] For wind turbines, leveraging rotor kinetic energy or reserving spare capacity can achieve system inertial stability. However, the former relies on rotor kinetic energy and can only increase active power output for a limited time, while the latter can result in significant power generation losses, resulting in poor economic efficiency and failing to meet current grid requirements for fully accommodating distributed renewable energy while ensuring power supply security. Currently, the most common virtual synchronous machine algorithms for photovoltaic and wind turbines mostly add energy storage (electrochemical energy storage or supercapacitors) to the DC bus between their converters to provide inertial support for the power system, adjust the voltage amplitude and frequency at the grid connection point, and achieve virtual synchronous control of individual distributed renewable energy units. However, upgrading the "unit-based virtual synchronous machine" algorithm for current wind turbines or photovoltaic power plants according to the proposed solution requires shutting down each individual generating unit and adding energy storage units on a "one-by-one" basis. This modification is cumbersome and costly. Therefore, a "station-based virtual synchronous machine" solution for large-scale wind and photovoltaic power plants is urgently needed to achieve "friendly" grid connection of distributed renewable energy.

[0060] It is recommended to add energy storage devices, primarily batteries, to the UPQC's common DC bus. This would achieve a wider range of transmission capacity and network control capabilities at a relatively low cost, increasing the UPQC's appeal to power companies, transmission companies, and distributed renewable energy operators. Furthermore, by fully leveraging the controllable and adjustable voltage amplitude and phase of the UPQC's series and parallel outputs, and upgrading the virtual synchronous generator algorithm on a traditional UPQC, the drawbacks of unit-type virtual synchronous generator retrofits could be avoided, further reducing the cost of distributed renewable energy retrofits. Furthermore, due to the UPQC's isolation, the voltage at the distributed renewable energy access point remains relatively stable, reducing the requirements for grid adaptability and fault ride-through capability.

[0061] Based on this, an embodiment of the present invention provides an adaptive virtual inertia control method for UPQC, including:

[0062] Constructing a UPQC system and a control model of an adaptive virtual synchronous machine in the UPQC system, wherein the UPQC system includes a series voltage source converter, a parallel voltage source converter, and an adaptive virtual inertia control system, wherein the adaptive virtual synchronous machine is connected to a port of the parallel voltage source converter to configure the parallel voltage source converter in a virtual synchronous generator control mode;

[0063] Among them, Figure 1 As shown, the adaptive virtual inertia control system includes: a frequency and voltage droop unit, an adaptive virtual synchronous machine and an adaptive virtual inertia calculation unit, wherein:

[0064] The frequency and voltage droop unit is used to apply frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine;

[0065] The adaptive virtual inertia calculation unit is used to determine a small disturbance amount corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance amount corresponding to the actual reactive power, and a small disturbance amount corresponding to the actual frequency based on a virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, the frequency control of the active power droop, and the voltage control of the reactive power droop, and based on the small disturbance amount corresponding to the actual active power, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency, determine that an adaptive adjustment model of the virtual inertia satisfies the following equation:

[0066]

[0067]

[0068] Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

[0069] It should be noted that the operating architecture of the UPQC system equipped with energy storage function is as follows Figure 2As shown in the figure. Under normal operation, distributed renewable energy generators transmit their generated energy to a remote AC grid. When renewable energy generation is in excess or insufficient, the energy storage battery system absorbs or compensates for the shortfall, ensuring stable power supply to the load center. The UPQC system consists of three core components: a series voltage source converter (SEC), a shunt voltage source 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 transformer, while the SHC is connected directly in parallel to node M2. The energy storage system is connected in parallel with the supporting capacitors 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 and dynamic energy balance management.

[0070] After detecting and extracting the harmonic voltage at node M1, the UPQC can use the SEC to generate a harmonic voltage of equal magnitude and opposite direction to offset the harmonic voltage generated by the harmonic source, thereby ensuring the voltage quality of the power grid. The SHC is controlled as a sinusoidal voltage source, so that the output voltage of the distributed renewable energy is a standard sinusoidal value. Because the voltage source has a small impedance to the harmonic current, the harmonic current of the power grid flows into the parallel converter, thereby offsetting the harmonic current and making the current flowing into the power grid close to the sinusoidal purpose. The voltage amplitude, phase, and frequency at the parallel connection of the UPQC can all be used as controllable electrical quantities to control the coordination between the UPQC and the distributed renewable energy, simulating the dynamic response capability of traditional synchronous generators to the grid voltage and frequency. This method provides a research approach for site-based virtual synchronous generators, which can autonomously maintain the stability and power quality of the power grid without shutting down and renovating existing wind turbines.

[0071] Considering the harmonic suppression effect of system filter components, a simplified model of the UPQC-BESS transmission system under the power frequency components of AC voltage and current is established as follows: Figure 3 shown. Represents the line impedance between the output terminal of the UPQC series side and the distribution network; It represents the line impedance between its parallel output terminal and the distributed new energy plant and the equivalent output impedance of its grid-connected inverter. 、 Represent the voltage amplitudes of the distribution network and distributed renewable energy respectively; 、 Respectively represent their voltage phases; 、 , 、 Represent the voltage amplitude and phase of nodes M1 and M2 respectively; 、 , 、 Represent the output voltage amplitude and phase of SEC and SHC respectively; Indicates the equivalent impedance of the UPQC series part, including the equivalent impedance of the series transformer , the line impedance between the UPQC series and parallel ports And the output impedance of SEC ; The equivalent impedance of the UPQC parallel part is represented by the output impedance of the SHC. For the Lord; Represents the apparent power transmitted to the distribution network; Represents the output apparent power of distributed renewable energy; 、 Represent the output apparent power of SEC and SHC respectively. Output power S from node M2 ​​through the main feeder line M2 There are two destinations: one is the power exchanged with the UPQC series part , and the other part is transmitted to the distribution network through transmission lines , including impedance losses on long transmission lines .like Figure 3 As shown, the UPQC series unit can be equivalent to a controllable voltage source and a dynamic output impedance in the steady state. An equivalent model of the voltage source, in which the amplitude-phase parameters of the voltage source are all controlled by the control.

[0072] Once the DC bus voltage is stabilized, the DC / DC converter and battery can be used as ideal energy storage sources to balance power differentials. Therefore, the DC / DC component is not further analyzed, and only its basic power model is presented. The bidirectional DC / DC power converter, SEC, and SHC in the battery energy storage system are electrically coupled via a shared DC bus. This architecture not only fulfills the core function of maintaining DC-side voltage stability for the UPQC but also provides the necessary real-time active power compensation for the two parallel-connected converter units. This energy interaction hub structure achieves dynamic power balancing within the system through a coordinated control strategy.

[0073] It should also be noted that in this application, when the series active filter is working, it is first necessary to accurately detect the harmonic voltage to be compensated, and then, by controlling the SEC, generate a compensation signal of equal magnitude and opposite direction to the harmonic voltage to offset the harmonic voltage, so that the harmonics in the network are finally compensated and the voltage and current waveforms are close to sine waves.

[0074] This device detects the three-phase grid voltage and obtains the grid voltage phase angle through phase-locked loop control. The transformation is converted into DC quantity, and the harmonics are filtered out by low-pass filter to obtain the fundamental component, which is then restored to the three-phase fundamental voltage after coordinate inverse transformation and subtracted from the original harmonic voltage to obtain the harmonic component. The basic principle is as follows Figure 4 As shown, where LPF is a low-pass filter.

[0075] The capacitor voltage and filter inductor current output by SEC are used as feedback quantities. The voltage outer loop adopts a proportional link to track the harmonic voltage, and the inner loop adopts a proportional link to improve the dynamic response of the active filter system. The SEC active filter control block diagram is shown in the figure below. Figure 5 As shown, 、 , They represent the voltage outer loop gain, current inner loop gain and PWM gain respectively.

[0076] In some implementations of this embodiment, the frequency-voltage droop unit includes a frequency droop subunit and a voltage droop subunit, wherein:

[0077] The frequency droop subunit is configured to apply the active power droop frequency control to the virtual synchronous generator (i.e., the adaptive virtual synchronous machine) based on the grid reference frequency, the actual frequency of the parallel voltage source converter port, the active power-frequency characteristic coefficient, the active power reference value output by the parallel voltage source converter, and the active power transmitted by the UPQC through the parallel voltage source converter;

[0078] The voltage droop subunit is used to apply reactive droop voltage control to the virtual synchronous generator (i.e., the adaptive virtual synchronous machine) based on the rated voltage amplitude of the power grid, the voltage amplitude of the port of the parallel voltage source converter, the reactive power-voltage amplitude characteristic coefficient, the reactive power reference value output by the parallel voltage source converter, and the reactive power transmitted by UPQC through the parallel voltage source converter.

[0079] Specifically, a VSG control model is constructed in UPQC to accurately reproduce the mechanical-electrical coupling dynamic characteristics of the synchronous generator at the grid interface. In the UPQC architecture with integrated energy storage, its parallel compensation port needs to build AC voltage stability support for distributed renewable energy grid connection points. Given this topological constraint, the SHC should be configured as a virtual synchronous generator control mode. The virtual synchronous generator control block diagram applicable to UPQC is shown below. Figure 6 shown.

[0080] Figure 6 middle, 、 Respectively represent the active and reactive power reference values ​​output by the SHC; 、 They represent the active power and reactive power transmitted by UPQC through SHC respectively; 、 Respectively represent the grid reference frequency and the actual frequency of the SHC port; 、 Respectively represent the rated voltage amplitude of the power grid and the voltage amplitude of the parallel port; is the active power-frequency characteristic coefficient, is the reactive power-voltage amplitude characteristic coefficient; 、 Respectively represent the grid voltage angular frequency and the output voltage amplitude of the parallel converter; is the active damping coefficient; 、 They represent the phase and SHC voltage amplitude instructions obtained by the virtual synchronous machine algorithm respectively; It’s the points-scoring phase.

[0081] In some implementations of this embodiment, the virtual synchronous machine algorithm adopts a second-order model of a traditional synchronous generator. The virtual synchronous machine algorithm corresponding to the virtual synchronous generator satisfies the following formula to simulate the motion characteristics of the rotor:

[0082]

[0083] Where, is the virtual inertia of the rotor; 、 are respectively the actual frequency and the rated frequency of the adaptive virtual synchronous machine; is the deviation between the actual frequency and the rated frequency of the adaptive virtual synchronous machine; 、 are respectively the actual output torque and torque given value of the adaptive virtual synchronous machine; is the active damping coefficient; P, P set are respectively the actual active power and the active power given value output by the adaptive virtual synchronous machine; Indicates the power angle.

[0084] It should be noted that in this application, the active power setting value of the adaptive virtual synchronous machine is That is, the active power reference value output by SHC ; Adaptive reactive power setpoint of virtual synchronous machine That is, the reactive power reference value output by SHC The actual active power P output by the adaptive virtual synchronous machine is the active power transmitted by UPQC through SHC. The actual active power Q output by the adaptive virtual synchronous machine is the reactive power transmitted by UPQC through SHC. .

[0085] In some implementations of this embodiment, the adaptive virtual inertia calculation unit is further configured to:

[0086] Determining an expression for a virtual electromotive force output by the adaptive virtual synchronous machine based on the voltage control of the reactive power droop;

[0087] Determine a steady-state equation of the adaptive virtual synchronous machine based on the frequency control of the active power droop, the expression of the virtual synchronous machine algorithm, the expression of the virtual electromotive force, the expression of the actual active power and the expression of the actual reactive power output by the adaptive virtual synchronous machine;

[0088] A disturbance is superimposed on the steady-state equation, and a Laplace transform is performed after disturbance separation and linearization to determine a small signal model corresponding to the adaptive virtual synchronous machine, wherein an expression of the small signal model includes a small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance function corresponding to the actual reactive power, a small disturbance function corresponding to the actual frequency, and a small disturbance function corresponding to the virtual electromotive force.

[0089] Specifically, the virtual electromotive force output by the VSG can be adjusted through the reactive voltage droop relationship. , wherein the virtual electromotive force Satisfies the following formula:

[0090]

[0091] Where, is the virtual electromotive force of the adaptive virtual synchronous machine; is the no-load electromotive force of the adaptive virtual synchronous machine; is the reactive voltage droop regulating part of the virtual electromotive force; is the terminal voltage deviation of the adaptive virtual synchronous machine; is the reactive damping coefficient; 、 are respectively the actual reactive power and the reactive power set value output by the adaptive virtual synchronous machine; is the voltage excitation regulation coefficient; is the actual voltage at the machine end of the adaptive virtual synchronous machine.

[0092] Furthermore, combined with the expressions of active power and reactive power output by the hidden-pole generator, the steady-state equation of the VSG is determined as follows:

[0093]

[0094] Where, is the port voltage of the adaptive virtual synchronous machine; is the synchronous reactance of the adaptive virtual synchronous machine.

[0095] Furthermore, the steady-state equation is superimposed with disturbances, and Laplace transform is performed after disturbance separation and linearization. It can be seen from the power angle characteristics of the synchronous motor that It is very small during normal operation, so the following approximate relationship can be obtained: , , At the same time, from the small signal assumption, we know that From this, we can get the system small signal model in which active and reactive power are relatively independent. Based on the small signal assumption, we can get the system small signal model in which active and reactive power are relatively independent:

[0096]

[0097] Where, They are respectively the small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, the small disturbance function corresponding to the actual reactive power, the small disturbance function corresponding to the actual frequency, the small disturbance function corresponding to the virtual electromotive force and the small disturbance function corresponding to the power angle; 、 They are respectively the active power given control quantity and reactive power given control quantity of the adaptive virtual synchronous machine; is a complex variable.

[0098] The overshoot and oscillation of the system are weakened by the automatic adjustment of the moment of inertia. When the power grid fluctuates too much, the moment of inertia is adjusted to improve the system damping ratio, reduce the power overshoot, shorten the oscillation period, and make the VSG system frequency always within the allowable range. When too large, Not exceeding the threshold , and in When too large, Not exceeding the threshold , the moment of inertia can be changed, that is, it satisfies:

[0099]

[0100]

[0101] Furthermore, it is determined that the adaptive adjustment model of the virtual inertia satisfies the following equation, that is, the expression of the adaptive virtual inertia is:

[0102]

[0103]

[0104] Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

[0105] In some implementations of this embodiment, the adaptive virtual synchronous machine is connected to the control port of the parallel voltage source converter, and is used to determine the voltage reference value of the parallel voltage source converter based on the frequency voltage droop unit and the adaptive virtual inertia calculation unit. and phase angle reference value , wherein the parallel voltage source converter is configured in a virtual synchronous generator control mode;

[0106] The adaptive virtual inertia control system further includes an SVPWM modulation unit for determining a pulse control signal for the parallel voltage source converter based on the voltage reference value and the phase angle reference value.

[0107] The UPQC further includes a bidirectional DC / DC converter and a battery energy storage device, wherein the battery energy storage device is connected in parallel with a DC capacitor of a common DC bus through the bidirectional DC / DC converter.

[0108] When the AC side frequency of the UPQC drops, the adaptive virtual synchronous machine extracts energy from the DC capacitor to provide inertia response, causing the voltage of the common DC bus to drop instantaneously. The bidirectional DC / DC converter adjusts the inductor current in real time through the voltage outer loop to control the charge and discharge power of the battery energy storage device, thereby providing voltage support for the DC capacitor.

[0109] The adaptive virtual inertia calculation unit is further configured to:

[0110] Based on the maximum current ramp rate of the ramp limiter in the battery energy storage device, the power synchronization coefficient, and the rated frequency of the adaptive virtual synchronous machine, a frequency step amplitude boundary required to trigger the ramp limiter is determined, wherein the frequency step amplitude boundary is expressed as follows:

[0111]

[0112] Based on the frequency step amplitude boundary, it is determined that the active adaptive virtual inertia satisfies the following constraints:

[0113]

[0114] Where, is the frequency step amplitude boundary; is the maximum current ramp rate; is the power synchronization coefficient; is the rated frequency of the adaptive virtual synchronous machine.

[0115] Specifically, when the AC side frequency of a UPQC system drops, the VSG prioritizes extracting energy from the DC capacitors to provide inertia response, causing a transient drop in the DC bus voltage. At this point, the DC-side DC / DC converter uses the voltage outer loop to regulate the inductor current in real time, controlling the battery charge and discharge power to rapidly support the DC capacitor voltage.

[0116] In some implementations of this embodiment, the VSG inertia frequency modulation power requirement satisfies the following formula:

[0117]

[0118] Where, is the VSG inertia frequency modulation power requirement, is the battery charging and discharging power, is the DC capacitor charging and discharging power, is the power transmission loss between the battery and the DC / DC converter;

[0119] In the system dynamic analysis, the charge and discharge current of the battery during the ramp period can be regarded as:

[0120]

[0121] Where, is the initial charge and discharge current of the battery, is the maximum current ramp rate of the ramp limiter.

[0122] In some implementations of this embodiment, the battery SOC change during hill climbing satisfies the following formula:

[0123]

[0124] Where, is the initial value of SOC, is the rated capacity of the battery, is the battery charging and discharging current;

[0125] The power output of the energy storage system to the front stage of the DC / DC converter during the ramp period satisfies the following formula:

[0126]

[0127] Where, is the voltage before the DC / DC converter, which is 0 at the moment when the battery starts to climb. A moment after the start of the climb.

[0128] When the battery charge and discharge rates are high, the SOC changes significantly during a single inertia frequency modulation cycle. Especially at the end of the charge and discharge cycle, the battery terminal voltage will fluctuate significantly with the rapid change in SOC. The fluctuation range of the DC bus capacitor voltage is mainly constrained by the rated withstand voltage level of the power electronic components and the modulation ratio of the pulse width modulation strategy. The fluctuation range of the DC side voltage of the inverter is generally controlled within ±15% of the rated voltage. The frequency step amplitude required to trigger the ramp limiter is bounded by:

[0129]

[0130] Taking into account the frequency step boundary, the constraint for determining the active adaptive inertia coefficient is:

[0131]

[0132] Where, is the power synchronization coefficient; is the rated frequency of the adaptive virtual synchronous machine.

[0133] The present invention also provides an adaptive virtual inertia control method for UPQC, as described in the following embodiments. Since the principle of solving the problem by this method is similar to that of the system, the implementation of this method can refer to the implementation of the system, and the repeated parts will not be repeated.

[0134] like Figure 7 As shown in FIG, the adaptive virtual inertia control method for UPQC includes:

[0135] Step 10: constructing a UPQC system and a control model of an adaptive virtual synchronous machine in the UPQC system, wherein the UPQC system includes a series voltage source converter and a parallel voltage source converter, and the adaptive virtual synchronous machine is connected to a port of the parallel voltage source converter to configure the parallel voltage source converter to a virtual synchronous generator control mode;

[0136] Step 20: Applying frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine;

[0137] Step 30: Based on the virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, the frequency control of the active power droop, and the voltage control of the reactive power droop, determine the small disturbance amount corresponding to the actual active power output by the adaptive virtual synchronous machine, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency.

[0138] Step 40: Based on the small disturbance amount corresponding to the actual active power, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency, determine whether the adaptive adjustment model of the virtual inertia satisfies the following equation:

[0139]

[0140]

[0141] Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

[0142] In some optional aspects of this embodiment, applying frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine includes:

[0143] Applying frequency control of the active power droop to the adaptive virtual synchronous machine based on a grid reference frequency, an actual frequency of the parallel voltage source converter port, an active power-frequency characteristic coefficient, an active power reference value output by the parallel voltage source converter, and active power transmitted by the UPQC through the parallel voltage source converter;

[0144] Based on the rated voltage amplitude of the power grid, the voltage amplitude of the port of the parallel voltage source converter, the reactive power-voltage amplitude characteristic coefficient, the reactive power reference value output by the parallel voltage source converter, and the reactive power transmitted by UPQC through the parallel voltage source converter, voltage control of reactive droop is applied to the adaptive virtual synchronous machine.

[0145] The virtual synchronous machine algorithm uses the second-order model of the synchronous generator to establish a mathematical model for simulating the motion characteristics of the rotor. The expression corresponding to the virtual synchronous machine algorithm is:

[0146]

[0147] Where, is the virtual inertia of the rotor; 、 are respectively the actual frequency and the rated frequency of the adaptive virtual synchronous machine; is the deviation between the actual frequency and the rated frequency of the adaptive virtual synchronous machine; 、 are respectively the actual output torque and torque given value of the adaptive virtual synchronous machine; is the active damping coefficient; 、 are respectively the actual active power and the active power given value output by the adaptive virtual synchronous machine; Indicates the power angle.

[0148] In some optional aspects of this embodiment, determining a small disturbance amount corresponding to actual active power, actual reactive power, and actual frequency output by the adaptive virtual synchronous machine based on a virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, frequency control of the active power droop, and voltage control of the reactive power droop includes:

[0149] Determining an expression for a virtual electromotive force output by the adaptive virtual synchronous machine based on the voltage control of the reactive power droop;

[0150] Determine a steady-state equation of the adaptive virtual synchronous machine based on the frequency control of the active power droop, the expression of the virtual synchronous machine algorithm, the expression of the virtual electromotive force, the expression of the actual active power and the expression of the actual reactive power output by the adaptive virtual synchronous machine;

[0151] A disturbance is superimposed on the steady-state equation, and a Laplace transform is performed after disturbance separation and linearization to determine a small signal model corresponding to the adaptive virtual synchronous machine, wherein an expression of the small signal model includes a small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance function corresponding to the actual reactive power, a small disturbance function corresponding to the actual frequency, and a small disturbance function corresponding to the virtual electromotive force.

[0152] In some optional aspects of this embodiment, the expression of the virtual electromotive force is as follows:

[0153]

[0154] Where, is the virtual electromotive force of the adaptive virtual synchronous machine; is the no-load electromotive force of the adaptive virtual synchronous machine; is the reactive voltage droop regulating part of the virtual electromotive force; is the terminal voltage deviation of the adaptive virtual synchronous machine; is the reactive damping coefficient; 、 are respectively the actual reactive power and the reactive power set value output by the adaptive virtual synchronous machine; is the voltage excitation regulation coefficient; is the actual voltage at the machine end of the adaptive virtual synchronous machine.

[0155] In some optional aspects of this embodiment, the steady-state equation of the adaptive virtual synchronous machine is expressed as follows:

[0156]

[0157] Where, is the port voltage of the adaptive virtual synchronous machine; is the synchronous reactance of the adaptive virtual synchronous machine.

[0158] In some optional aspects of this embodiment, the expression of the small signal model is as follows:

[0159]

[0160] Where, They are respectively the small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, the small disturbance function corresponding to the actual reactive power, the small disturbance function corresponding to the actual frequency, the small disturbance function corresponding to the virtual electromotive force and the small disturbance function corresponding to the power angle; 、 They are respectively the active power given control quantity and reactive power given control quantity of the adaptive virtual synchronous machine; is a complex variable.

[0161] In some optional aspects of this embodiment, the UPQC further includes a bidirectional DC / DC converter and a battery energy storage device, wherein the battery energy storage device is connected in parallel with a DC capacitor of a common DC bus through the bidirectional DC / DC converter;

[0162] When the AC side frequency of the UPQC drops, the adaptive virtual synchronous machine extracts energy from the DC capacitor to provide inertia response, causing the voltage of the common DC bus to drop instantaneously. The bidirectional DC / DC converter adjusts the inductor current in real time through the voltage outer loop to control the charge and discharge power of the battery energy storage device, thereby providing voltage support for the DC capacitor.

[0163] The adaptive virtual inertia control method further includes:

[0164] Based on the maximum current ramp rate of the ramp limiter in the battery energy storage device, the power synchronization coefficient, and the rated frequency of the adaptive virtual synchronous machine, a frequency step amplitude boundary required to trigger the ramp limiter is determined, wherein the frequency step amplitude boundary is expressed as follows:

[0165]

[0166] Based on the frequency step amplitude boundary, it is determined that the active adaptive virtual inertia satisfies the following constraints:

[0167]

[0168] Where, is the frequency step amplitude boundary; is the maximum current ramp rate; is the power synchronization coefficient; is the rated frequency of the adaptive virtual synchronous machine.

[0169] To address the coordinated operation and control issues of series and parallel converters in UPQC, this paper proposes an adaptive virtual inertia control method that enables the new energy power generation device to have the frequency and voltage support capabilities of a traditional synchronous generator without changing the original control system. Combined with the verification of simulation experiments, the following conclusions are drawn:

[0170] 1) Analyze the mathematical model of the UPQC system with energy storage capacity in steady state, explain the power flow mechanism inside the UPQC, and design a virtual synchronous generator control strategy suitable for the UPQC.

[0171] 2) Aiming at the virtual synchronization control strategy of the unified power quality conditioner, a UPQC power mathematical model is established based on the operation scheme of the UPQC system with energy storage capability. By simulating traditional synchronous generator sets, no external modification is required, and only the original converter control of the renewable energy power generation is modified to implement a virtual synchronization control strategy suitable for UPQC.

[0172] 3) Based on the VSG small signal model, an adaptive control strategy for the moment of inertia is proposed to adaptively adjust the moment of inertia and automatically adjust it to weaken the overshoot and oscillation of the system, thereby improving the active power and frequency stability of the distribution network.

[0173] It can be understood that the above examples are merely examples listed for a better understanding of the technical solutions of the embodiments of the present invention, and are not intended to be the sole limitation on the embodiments of the present invention.

[0174] It should be noted that, in the description of this application, the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of this application and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0175] It should also be noted that, in the description of the present application, relational terms such as first and second, etc. are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply the existence of any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0176] In the embodiments of this application, the singular forms "a," "the," etc. include plural forms and should be broadly understood to mean "a" or "a type" rather than being limited to "one." Furthermore, the term "said" should be understood to include both singular and plural forms, unless the context clearly indicates otherwise. Furthermore, the term "according to" should be understood to mean "at least in part based on...", and the term "based on" should be understood to mean "at least in part based on...", unless the context clearly indicates otherwise.

[0177] It should be understood that the various forms of the processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this disclosure can be performed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions of this disclosure can be achieved. This is not a limitation herein.

[0178] The above specific embodiments do not constitute a limitation on the scope of protection of this disclosure. Those skilled in the art will appreciate that various modifications, combinations, sub-combinations, and substitutions may be made based on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this disclosure shall be included within the scope of protection of this disclosure.

[0179] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. An adaptive virtual inertia control system for an UPQC, wherein the UPQC comprises a series voltage source converter and a parallel voltage source converter, characterized in that: The adaptive virtual inertia control system includes: a frequency and voltage droop unit, an adaptive virtual synchronous machine, and an adaptive virtual inertia calculation unit, wherein: The frequency and voltage droop unit is used to apply frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine; The adaptive virtual inertia calculation unit is used to determine, based on a virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, the frequency control of the active power droop, and the voltage control of the reactive power droop, a small disturbance amount corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance amount corresponding to the actual reactive power, and a small disturbance amount corresponding to the actual frequency, and determine an adaptive adjustment model of the virtual inertia based on the small disturbance amount corresponding to the actual active power, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency. The adaptive adjustment model of the virtual inertia is as follows: Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; U n is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

2. The adaptive virtual inertia control system according to claim 1, characterized in that: The frequency and voltage droop unit includes a frequency droop subunit and a voltage droop subunit, wherein: The frequency droop subunit is configured to apply the active power droop frequency control to the adaptive virtual synchronous machine based on the grid reference frequency, the actual frequency of the parallel voltage source converter port, the active power-frequency characteristic coefficient, the active power reference value output by the parallel voltage source converter, and the active power transmitted by the UPQC through the parallel voltage source converter; The voltage droop subunit is used to apply reactive droop voltage control to the adaptive virtual synchronous machine based on the rated voltage amplitude of the power grid, the voltage amplitude of the port of the parallel voltage source converter, the reactive power-voltage amplitude characteristic coefficient, the reactive power reference value output by the parallel voltage source converter, and the reactive power transmitted by UPQC through the parallel voltage source converter.

3. The adaptive virtual inertia control system according to claim 2, characterized in that: The virtual synchronous machine algorithm uses the second-order model of the synchronous generator to establish a mathematical model for simulating the motion characteristics of the rotor. The model corresponding to the virtual synchronous machine algorithm is: Where, is the virtual inertia of the rotor; 、 are respectively the actual frequency and the rated frequency of the adaptive virtual synchronous machine; is the deviation between the actual frequency and the rated frequency of the adaptive virtual synchronous machine; 、 are respectively the actual output torque and torque given value of the adaptive virtual synchronous machine; is the active damping coefficient; 、 are respectively the actual active power and the active power given value output by the adaptive virtual synchronous machine; Indicates the power angle.

4. The adaptive virtual inertia control system according to claim 3, characterized in that: The adaptive virtual inertia calculation unit is further configured to: Determining a model of a virtual electromotive force output by the adaptive virtual synchronous machine based on the voltage control of the reactive power droop; Determining a steady-state model of the adaptive virtual synchronous machine based on the frequency control of the active power droop, the model of the virtual synchronous machine algorithm, the model of the virtual electromotive force, the model of the actual active power output by the adaptive virtual synchronous machine, and the model of the actual reactive power; A disturbance is superimposed on the steady-state model, and a Laplace transform is performed after disturbance separation and linearization to determine a small signal model corresponding to the adaptive virtual synchronous machine, wherein the small signal model includes a small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, a small disturbance function corresponding to the actual reactive power, a small disturbance function corresponding to the actual frequency, and a small disturbance function corresponding to the virtual electromotive force.

5. The adaptive virtual inertia control system according to claim 4, characterized in that: The model of the virtual electromotive force is as follows: Where, is the virtual electromotive force of the adaptive virtual synchronous machine; is the no-load electromotive force of the adaptive virtual synchronous machine; is the reactive voltage droop regulating part of the virtual electromotive force; is the terminal voltage deviation of the adaptive virtual synchronous machine; is the reactive damping coefficient; 、 are respectively the actual reactive power and the reactive power set value output by the adaptive virtual synchronous machine; is the voltage excitation regulation coefficient; is the actual voltage at the machine end of the adaptive virtual synchronous machine.

6. The adaptive virtual inertia control system according to claim 4, characterized in that: The steady-state model of the adaptive virtual synchronous machine is as follows: Where, is the port voltage of the adaptive virtual synchronous machine; is the synchronous reactance of the adaptive virtual synchronous machine.

7. The adaptive virtual inertia control system according to claim 4, characterized in that: The small signal model is as follows: Where, 、 、 、 、 They are respectively the small disturbance function corresponding to the actual active power output by the adaptive virtual synchronous machine, the small disturbance function corresponding to the actual reactive power, the small disturbance function corresponding to the actual frequency, the small disturbance function corresponding to the virtual electromotive force and the small disturbance function corresponding to the power angle; 、 They are respectively the active power given control quantity and reactive power given control quantity of the adaptive virtual synchronous machine; is a complex variable.

8. The adaptive virtual inertia control system according to claim 1, characterized in that: The adaptive virtual synchronous machine is connected to a control port of the parallel voltage source converter and is configured to determine a voltage reference value and a phase angle reference value of the parallel voltage source converter based on the frequency voltage droop unit and the adaptive virtual inertia calculation unit, wherein the parallel voltage source converter is configured in a virtual synchronous generator control mode; The adaptive virtual inertia control system further includes an SVPWM modulation unit for determining a pulse control signal for the parallel voltage source converter based on the voltage reference value and the phase angle reference value.

9. The adaptive virtual inertia control system according to claim 1, characterized in that: The UPQC further includes a bidirectional DC / DC converter and a battery energy storage device, wherein the battery energy storage device is connected in parallel with a DC capacitor of a common DC bus through the bidirectional DC / DC converter; When the AC side frequency of the UPQC drops, the adaptive virtual synchronous machine extracts energy from the DC capacitor to provide inertia response, causing the voltage of the common DC bus to drop instantaneously. The bidirectional DC / DC converter adjusts the inductor current in real time through the voltage outer loop to control the charge and discharge power of the battery energy storage device, thereby providing voltage support for the DC capacitor. The adaptive virtual inertia calculation unit is further configured to: Based on the maximum current ramp rate of the ramp limiter in the battery energy storage device, the power synchronization coefficient, and the rated frequency of the adaptive virtual synchronous machine, a frequency step amplitude boundary required to trigger the ramp limiter is determined, wherein the frequency step amplitude boundary is expressed as follows: Based on the frequency step amplitude boundary, it is determined that the active adaptive virtual inertia satisfies the following constraints: Where, is the frequency step amplitude boundary; is the maximum current ramp rate; is the power synchronization coefficient; is the rated frequency of the adaptive virtual synchronous machine.

10. An adaptive virtual inertia control method for UPQC, characterized in that: include: Constructing a UPQC system and a control model of an adaptive virtual synchronous machine in the UPQC system, wherein the UPQC system includes a series voltage source converter and a shunt voltage source converter, the adaptive virtual synchronous machine is connected to a port of the shunt voltage source converter, and is configured to configure the shunt voltage source converter to a virtual synchronous generator control mode; Applying frequency control of active power droop and voltage control of reactive power droop to the adaptive virtual synchronous machine; Determining a small disturbance amount corresponding to actual active power, actual reactive power, and actual frequency output by the adaptive virtual synchronous machine based on a virtual synchronous machine algorithm corresponding to the adaptive virtual synchronous machine, frequency control of the active power droop, and voltage control of the reactive power droop; Based on the small disturbance amount corresponding to the actual active power, the small disturbance amount corresponding to the actual reactive power, and the small disturbance amount corresponding to the actual frequency, an adaptive adjustment model of the virtual inertia is determined, wherein the adaptive adjustment model of the virtual inertia is as follows: Where, is the steady-state virtual inertia; It is active adaptive virtual inertia; is the reactive adaptive virtual inertia; is the small disturbance corresponding to the actual active power; is the small disturbance amount corresponding to the actual frequency; is the maximum deviation between the actual frequency and the rated frequency; is the small disturbance corresponding to the actual reactive power; is the rated voltage of the machine end of the adaptive virtual synchronous machine; It is the maximum deviation between the actual voltage at the machine end and the rated voltage at the machine end.

Images