A new type of grid-type supercapacitor energy storage inertial support system

Abstract

The present invention proposes a novel grid-type supercapacitor energy storage inertia support system, including photovoltaic panels, fans, supercapacitors, DC busbars, and AC main grid, wherein the photovoltaic panels are connected to the DC busbars through a DC / DC converter; the fans are connected to the DC busbars through an AC / DC rectifier; the supercapacitors are connected to the DC busbars through a DC / DC converter for rapid release / absorption of electrical energy; the DC busbars are connected to the AC main grid through a DC / AC converter and an industrial frequency step-up transformer, and an AC load is configured on the AC transmission line; the DC / AC converter is used to realize the inertia support of the new energy storage microgrid through a simulated inertia algorithm. The system proposed by the present invention can improve the inertia support capability of the DC microgrid.

Description

Technical Field

[0001] The invention belongs to the field of novel grid-type energy storage. Background Art

[0002] Renewable energy power generation uses a large number of power electronic equipment. Traditional power electronic equipment cannot provide the power system with the same rotational inertia as a rotating motor. This will seriously weaken the power system's frequency regulation ability and make it impossible to suppress frequency disturbances caused by power fluctuations. It may even cause large-scale disconnection of new energy from the grid, seriously affecting the stability of the power system.

[0003] Energy storage and new energy sources such as wind power and photovoltaics adopt DC networking, which can make the interconnection between energy storage and new energy simple and efficient. The DC networking form does not need to consider reactive power optimization problems, and there is no harmonic pollution. In the DC / AC converter of the new energy storage microgrid, strategies such as virtual inertia control, droop control, and virtual synchronous machine are adopted to provide virtual inertia support for the microgrid with frequency regulation capability. Existing method 1 adds a virtual inertia response module to the frequency control link of the microgrid converter to ensure that the output frequency of the microgrid is consistent with the frequency change deviation rate of the large power grid, and the energy storage in the microgrid absorbs / releases energy to achieve instantaneous response to frequency deviation. Existing method 2 In order to improve the synchronous inertia support capability of the system, the frequency differential signal is introduced into the energy storage converter control system to realize inertia simulation, and a robust controller is further added to improve the output frequency characteristics of the energy storage. The literature analyzes the frequency oscillation mechanism of the regional power grid caused by power imbalance at the sending and receiving ends, adopts a virtual synchronous machine control strategy, and characterizes the virtual inertia with the frequency difference change rate to improve the inertia support performance of the virtual synchronous machine for the power grid.

[0004] In a DC microgrid, power electronic devices are connected through a DC bus. The DC voltage is stably maintained within a certain range. The voltage regulation is robust in the face of power fluctuations, which is a research focus in the field of inertia control of grid-connected converters. Existing method 3 proposes an inertia control scheme that simulates a virtual DC motor, characterizes the virtual inertia with the rate of change of DC voltage, and adaptively adjusts the acceleration voltage of the virtual inertia to restore it to a steady state. Existing method 4 analyzes the power angle characteristics of the energy storage system before and after the voltage drop fault, takes reducing the acceleration area as the control target, and proposes a series of measures to maintain the stability of the energy storage output voltage during the fault. Existing method 5 introduces the DC bus voltage of the new energy microgrid as a negative feedback signal into the integral link in the voltage outer loop of the grid-connected converter, replaces the line impedance with an adjustable virtual impedance, and realizes dynamic adjustment of the DC voltage.

[0005] However, existing methods cannot achieve energy storage DC virtual inertia support. Summary of the invention

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0007] To this end, the purpose of the present invention is to propose a novel grid-forming supercapacitor energy storage inertia support system for improving the inertia support capacity of a DC microgrid.

[0008] To achieve the above-mentioned purpose, the first embodiment of the present invention proposes a novel grid-type supercapacitor energy storage inertia support system, comprising:

[0009] Photovoltaic panels, wind turbines, supercapacitors, DC bus, AC main grid, including:

[0010] The photovoltaic panel is connected to the DC bus through a DC / DC converter;

[0011] The fan is connected to the DC bus through an AC / DC rectifier;

[0012] The supercapacitor is connected to the DC bus through a DC / DC converter to quickly release / absorb electrical energy;

[0013] The DC bus is connected to the AC main grid through a DC / AC converter and an industrial frequency step-up transformer, and an AC load is configured on the AC transmission line; the DC / AC converter is used to achieve inertia support for the new energy storage microgrid through a simulated inertia algorithm.

[0014] In addition, a novel grid-type supercapacitor energy storage inertia support system according to the above embodiment of the present invention may also have the following additional technical features:

[0015] Furthermore, in one embodiment of the present invention, the DC / AC converter is also used for:

[0016] The frequency changes of the new energy storage microgrid are restored by detecting the DC voltage.

[0017] To achieve the above-mentioned purpose, the second embodiment of the present invention proposes a virtual inertia control method based on a new energy storage microgrid, which is applied to the novel grid-type supercapacitor energy storage inertia support system as described above, and is characterized in that it includes:

[0018] By configuring supercapacitor energy storage to quickly release / absorb electric energy and adopting a simulated rotating synchronous motor inertia control method in a DC / AC converter, the inertia support capacity of the new energy storage microgrid is improved.

[0019] Furthermore, in one embodiment of the present invention, the simulated rotating synchronous motor inertia control method comprises:

[0020] Definition of the rotating synchronous motor rotor rotational kinetic energy E k It is expressed as:

[0021]

[0022] Where, p is the number of motor pole pairs; J sg ,ω sg are the motor moment of inertia and mechanical angular velocity respectively;

[0023] The inertia H of a rotating synchronous motor is expressed as:

[0024]

[0025] Among them, ω n , N They are the rated mechanical angular speed and rated capacity of the motor respectively;

[0026] Rotational kinetic energy E k Taking the derivative with respect to time and introducing the inertia H, the motion equation of the rotor of the rotating synchronous motor is obtained as follows:

[0027]

[0028] Among them, P, P m , P e are the output power, mechanical power and electromagnetic power of the rotating synchronous motor respectively; ω0 and ω are the initial mechanical angular velocity and the current mechanical angular velocity respectively;

[0029] A supercapacitor is configured in the DC microgrid to provide the kinetic energy required for simulating inertia. The supercapacitor releases / absorbs electrical energy through voltage transformation. Its charging and discharging power P c It is expressed as:

[0030]

[0031] Among them, C, S c 、u c are respectively the energy storage capacitance value, rated capacity, and output voltage of the supercapacitor;

[0032] The supercapacitor energy storage release / absorption of electric energy is used to simulate the motion equation of the rotating synchronous motor rotor, and the supercapacitor inertia support equation is obtained as follows:

[0033]

[0034] Among them, H c is the virtual inertia of supercapacitor energy storage; ω c0 ,ω c They are the initial virtual angular frequency and current virtual angular frequency of supercapacitor energy storage respectively.

[0035] Furthermore, in one embodiment of the present invention, it is characterized in that it also includes:

[0036] The frequency changes of the new energy storage microgrid are restored by detecting the DC voltage.

[0037] Furthermore, in one embodiment of the present invention, it is characterized in that restoring the frequency change of the new energy storage microgrid by detecting the DC voltage includes:

[0038] The DC voltage-frequency virtual inertia control scheme is adopted in the DC / AC converter of the new energy storage microgrid, which is expressed as:

[0039] U dc =K dc (ω-ω0)+U dc0 ,

[0040] Among them, U dc , U dc0 are the current value and initial value of the DC bus voltage respectively; ω and ω0 are the current angular frequency and initial angular frequency of the AC side power grid respectively, K dc is the DC inertia gain;

[0041] According to the supercapacitor inertia support equation and the DC voltage-frequency virtual inertia control scheme, the DC virtual inertia gain is obtained, which is expressed as:

[0042]

[0043] The novel grid-connected supercapacitor energy storage inertia support system proposed in the embodiment of the present invention can improve the inertia support capacity of the DC microgrid by configuring supercapacitor energy storage to quickly release / absorb electric energy and using a simulated inertia algorithm in the grid-connected DC / AC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0045] Figure 1 A schematic diagram of a novel grid-type supercapacitor energy storage inertia support system provided in an embodiment of the present invention.

[0046] Figure 2 A frequency fluctuation interval division diagram caused by load input provided in an embodiment of the present invention.

[0047] Figure 3 A block diagram of a virtual inertia current inner loop control provided by an embodiment of the present invention.

[0048] Figure 4 A schematic diagram of a DC bus voltage deviation response curve provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0050] The novel grid-type supercapacitor energy storage inertial support system according to an embodiment of the present invention will be described below with reference to the accompanying drawings.

[0051] Figure 1 A schematic diagram of a novel grid-type supercapacitor energy storage inertia support system provided in an embodiment of the present invention.

[0052] like Figure 1 As shown, the new type of grid-type supercapacitor energy storage inertia support system includes the following:

[0053] Photovoltaic panels, wind turbines, supercapacitors, DC bus, AC main grid, including:

[0054] The photovoltaic panel is connected to the DC bus through a DC / DC converter;

[0055] The fan is connected to the DC bus through an AC / DC rectifier;

[0056] The supercapacitor is connected to the DC bus through a DC / DC converter to quickly release / absorb electrical energy;

[0057] The DC bus is connected to the AC main grid through a DC / AC converter and an industrial frequency step-up transformer, and an AC load is configured on the AC transmission line; the DC / AC converter is used to achieve inertia support for the new energy storage microgrid through a simulated inertia algorithm.

[0058] Furthermore, in one embodiment of the present invention, the DC / AC converter is also used for:

[0059] The frequency changes of the new energy storage microgrid are restored by detecting the DC voltage.

[0060] like Figure 1As shown in the figure, the photovoltaic panel is connected to the DC bus through a DC / DC converter, and the output power is represented by PPV; the wind turbine is connected to the DC bus through an AC / DC rectifier, and the output power is represented by PW; the supercapacitor is connected to the DC bus through a DC / DC converter, and the absorption / release power is represented by PC; a DC load is configured in the DC microgrid. The DC bus is connected to the AC main grid through a DC / AC converter and an industrial frequency step-up transformer, and an AC load is configured on the AC transmission line. The power exchange between the DC microgrid and the AC grid is represented by P. Load switching will cause the frequency fluctuation of the DC microgrid's grid-connected DC / AC converter, further causing the DC bus voltage fluctuation, affecting the stable operation of the DC microgrid. By configuring supercapacitor energy storage to quickly release / absorb electric energy, and using a simulated inertia algorithm in the grid-connected DC / AC converter, the inertia support capacity of the DC microgrid can be improved.

[0061] In order to implement the above embodiments, the present invention also proposes a virtual inertia control method based on a new energy storage microgrid.

[0062] The virtual inertia control method includes: quickly releasing / absorbing electric energy by configuring supercapacitor energy storage, and using a simulated rotating synchronous motor inertia control method in the DC / AC converter to improve the inertia support capacity of the new energy storage microgrid

[0063] The present invention adopts a simulated rotating synchronous motor inertia control method in a microgrid grid-connected DC / AC converter.

[0064] Furthermore, in one embodiment of the present invention, a method for simulating the inertia control of a rotating synchronous motor includes:

[0065] Definition of the rotating synchronous motor rotor rotational kinetic energy E k It is expressed as:

[0066]

[0067] Where, p is the number of motor pole pairs; J sg ,ω sg are the motor moment of inertia and mechanical angular velocity respectively;

[0068] The inertia H of a rotating synchronous motor is expressed as:

[0069]

[0070] Among them, ω n , N They are the rated mechanical angular speed and rated capacity of the motor respectively;

[0071] Rotational kinetic energy E k Taking the derivative with respect to time and introducing the inertia H, the motion equation of the rotor of the rotating synchronous motor is obtained as follows:

[0072]

[0073] Among them, P, P m , P e are the output power, mechanical power and electromagnetic power of the rotating synchronous motor respectively; ω0 and ω are the initial mechanical angular velocity and the current mechanical angular velocity respectively;

[0074] Supercapacitors are configured in the DC microgrid to provide the kinetic energy required for simulating inertia. The supercapacitor releases / absorbs electrical energy through voltage transformation. Its charging and discharging power P c It is expressed as:

[0075]

[0076] Among them, C, S c 、u c They are respectively the energy storage capacitance value, rated capacity, and output voltage of the supercapacitor;

[0077] By simulating the motion equation of the rotating synchronous motor rotor by releasing / absorbing electric energy through supercapacitor energy storage, the supercapacitor inertia support equation is obtained as follows:

[0078]

[0079] Among them, H c is the virtual inertia of supercapacitor energy storage; ω c0 ,ω c They are the initial virtual angular frequency and current virtual angular frequency of supercapacitor energy storage respectively.

[0080] Furthermore, in one embodiment of the present invention, it is characterized in that it also includes:

[0081] The frequency changes of the new energy storage microgrid are restored by detecting the DC voltage.

[0082] Furthermore, in one embodiment of the present invention, it is characterized in that restoring the frequency change of the new energy storage microgrid by detecting the DC voltage includes:

[0083] The DC voltage-frequency virtual inertia control scheme is adopted in the DC / AC converter of the new energy storage microgrid, which is expressed as:

[0084] U dc =K dc (ω-ω0)+U dc0 , (6)

[0085] Among them, U dc , U dc0 are the current value and initial value of the DC bus voltage respectively; ω and ω0 are the current angular frequency and initial angular frequency of the AC side power grid respectively, Kdc is the DC inertia gain;

[0086] According to the supercapacitor inertia support equation and the DC voltage-frequency virtual inertia control scheme, the DC virtual inertia gain is obtained, which is expressed as:

[0087]

[0088] The DC voltage-frequency virtual inertia control scheme is used in the DC / AC converter of the new energy storage microgrid to provide inertia support for the power system. However, the frequency disturbance caused by load switching is different. Setting a fixed virtual inertia gain cannot achieve the dynamic response of the simulated inertia according to the frequency change, especially in the frequency recovery stage. A large virtual inertia is not conducive to frequency recovery. This paper divides the frequency drop caused by load switching and the frequency recovery into four areas, such as Figure 2 described.

[0089] Figure 2 In the figure, the four regions correspond to frequency drop, frequency recovery, frequency overshoot and frequency stability. In order to solve the problem of inflexible frequency adjustment caused by constant virtual inertia, the traditional virtual inertia control is improved. The virtual inertia is automatically increased according to the frequency increase / decrease amplitude. The large virtual inertia can suppress the frequency fluctuation (region I and region III). The virtual inertia is reduced in the frequency recovery stage to speed up the frequency recovery (region II and region IV). The regional division and inertia adjustment are shown in Table 1.

[0090] Table 1

[0091]

[0092] According to the establishment of a new type of virtual inertia, it can be expressed as:

[0093]

[0094] In formula (8): H c0 is the initial virtual inertia; Δω is the virtual frequency adjustment; α and β are the frequency deviation threshold and frequency change rate threshold, respectively. The values ​​of α and β are determined according to the characteristics of the converter; k H is the virtual inertia adjustment coefficient.

[0095] In order to set the parameters of the initial virtual inertia and the virtual inertia adjustment coefficient, this paper analyzes the damping ratio.

[0096] The DC voltage-frequency virtual inertia control can be equivalent to a typical second-order transfer function, and the control system damping ratio ζ is:

[0097]

[0098] In formula (9), D is the virtual damping; X is the equivalent reactance of the AC line; Us is the AC line voltage; U0 is the AC side voltage of the new energy storage microgrid DC / AC converter; δ0 is the initial value of the voltage power angle, which is approximately 0, then cosδ0≈1.

[0099] When the power system frequency is regulated, the damping ratio ζ is required to be within [0.1-0.8], so the initial virtual inertia H c0 The value range is:

[0100]

[0101] According to formula (8), the virtual inertia adjustment coefficient k H satisfy:

[0102]

[0103] In formula (11): H cmax is the maximum virtual inertia of supercapacitor energy storage. When the frequency regulation of the new virtual inertia control system transitions to steady state, the angular frequency deviation can be expressed as:

[0104]

[0105] In formula (12): ΔU dc is the DC bus voltage regulation value.

[0106] Substituting equation (11) into equation (12), we can get the virtual inertia adjustment coefficient k H The expression is:

[0107]

[0108] This paper proposes a solution to configure the supercapacitor energy storage capacity according to the supercapacitor energy storage voltage variation range and the maximum virtual inertia. The DC bus adjustment range is:

[0109]

[0110] In formula (14): Δω min , Δω max are the minimum and maximum virtual frequency respectively. According to formula (12), the optimal configuration formula of supercapacitor energy storage capacitance value can be obtained as follows:

[0111]

[0112] In formula (15):

[0113] By configuring the supercapacitor energy storage capacitor according to the DC bus voltage variation range and the maximum virtual inertia, the optimal capacitance configuration can be achieved on the basis of satisfying the virtual inertia.

[0114] When the DC / AC converter of the new energy storage microgrid faces frequency fluctuations caused by load switching, transient virtual inertia support can be provided through the DC side supercapacitor energy storage. In the frequency recovery stage, if the fluctuation persists, the DC bus voltage cannot be restored to the initial value. In the low voltage / high voltage state, if the load continues to be switched on / off, the new energy storage microgrid will be disconnected from the grid due to the voltage being too low / too high, seriously affecting the stable operation of the power system. In order to quickly restore the DC bus voltage in the frequency recovery stage, the present invention proposes a high-frequency component inertia simulation method based on a high-pass filter, which enables the new energy storage microgrid to maintain a stable DC bus voltage without changing the inertia support of the supercapacitor energy storage.

[0115] Furthermore, in one embodiment of the present invention, a high-pass filter is introduced into the new energy storage microgrid to maintain the DC bus voltage stable, including:

[0116] Define the DC virtual inertia gain transfer function:

[0117]

[0118] Among them, K g is the virtual inertia high-pass gain coefficient, ω g is the high-pass filter cutoff frequency;

[0119] Substituting the DC virtual inertia gain transfer function into the DC voltage-frequency virtual inertia control scheme, the virtual inertia control equation containing a high-pass filter is obtained:

[0120]

[0121] Among them, U dc , U dc0 are the current value and initial value of the DC bus voltage respectively; ω and ω0 are the current angular frequency and initial angular frequency of the AC side power grid respectively.

[0122] According to formula (17), when a high-frequency filter is introduced into the inertia control, the frequency regulation only processes the high-frequency component, and the influence of the low-frequency component on the DC bus voltage regulation can be ignored. That is, when the load switching causes frequency fluctuations, the virtual inertia control system containing the high-pass filter link only extracts the AC side grid angular frequency ω g , and perform inertia adjustment. g When the high-pass filter is stable, the DC bus voltage returns to its initial value. By combining equation (17) and equation (7), the virtual moment of inertia expression containing the high-pass filter link can be obtained as follows:

[0123]

[0124] Next, the voltage regulation characteristics are analyzed. Referring to equation (9), we can get the damping ratio ζ of the DC voltage-frequency virtual inertia control system after the high-pass filter is introduced: H for:

[0125]

[0126] In formula (19): U dcH is the DC bus voltage high-pass filter increment. By adjusting the virtual inertia high-pass gain coefficient, the control system damping ratio can be changed to effectively reduce the frequency disturbance on the DC bus voltage. H Set as the optimal damping ratio, i.e. ζ H =0.707, the optimal virtual inertia high-pass gain K gu for:

[0127]

[0128] Virtual inertia high-pass gain maximum value K gmax It is related to the maximum modulation ratio (0.5) and frequency fluctuation range (±1%) of the new energy storage microgrid DC / AC converter, and can be expressed as:

[0129]

[0130] According to formula (20-21), the high-pass gain of the voltage-frequency virtual inertia can be determined. In this paper, a new type of virtual inertia control is used in the outer loop of the DC / AC converter of the new energy storage microgrid, and the inner loop adopts current closed-loop control. The current inner loop is given by the output ΔU of the new virtual inertia control outer loop. dc , the inner current loop is divided into dq axis current control, I d Corresponding active power, I q Corresponding to reactive power, there is no need to consider reactive power in DC microgrids. We only need to consider I d Ignoring the dynamic response of the current inner loop, the current inner loop control link can be expressed as:

[0131]

[0132] In formula (22): K p , K i They are the current inner loop proportional and integral coefficients respectively. The control block diagram is shown in Figure 4 shown.

[0133] Figure 3 middle: It is the active current reference value.

[0134] Active power current I d It is expressed as:

[0135]

[0136] In formula (23), δ is the voltage power angle. Combining formula (6), formula (22) and formula (23), we can get:

[0137]

[0138] According to formula (24), the virtual inertia control transfer function is obtained as follows:

[0139]

[0140] Substituting equation (16) into equation (25), we can get the virtual inertia control transfer function containing a high-pass filter. During the frequency fluctuation recovery process, the DC bus voltage deviation response curve is as follows: Figure 4 shown.

[0141] The novel grid-connected supercapacitor energy storage inertia support system proposed in the embodiment of the present invention can improve the inertia support capacity of the DC microgrid by configuring supercapacitor energy storage to quickly release / absorb electric energy and using a simulated inertia algorithm in the grid-connected DC / AC converter.

[0142] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0143] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0144] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A novel grid-type supercapacitor energy storage inertia support system, characterized in that: include: Photovoltaic panels, wind turbines, supercapacitors, DC bus, AC main grid, including: The photovoltaic panel is connected to the DC bus through a DC / DC converter; The fan is connected to the DC bus through an AC / DC rectifier; The supercapacitor is connected to the DC bus through a DC / DC converter to quickly release / absorb electrical energy; The DC bus is connected to the AC main grid through a DC / AC converter and an industrial frequency step-up transformer, and an AC load is configured on the AC transmission line; the DC / AC converter is used to realize inertia support for the new energy storage microgrid through a simulated inertia algorithm; The simulated inertia algorithm includes: dividing the frequency drop and frequency recovery caused by load input into four areas, the four areas correspond to frequency drop, frequency recovery, frequency overshoot and frequency stability, automatically increasing the virtual inertia according to the frequency increase or decrease amplitude, and the large virtual inertia can suppress the frequency fluctuation, and reducing the virtual inertia in the frequency recovery stage to speed up the frequency recovery; According to the establishment of a new type of virtual inertia is expressed as: Where: H c0 is the initial virtual inertia; Δω is the virtual frequency adjustment; α and β are the frequency deviation threshold and frequency change rate threshold, respectively. The values ​​of α and β are determined according to the characteristics of the converter; k H is the virtual inertia adjustment coefficient; The DC voltage-frequency virtual inertia control is equivalent to a typical second-order transfer function, and the control system damping ratio ζ is: Where: D is virtual damping; X is the equivalent reactance of the AC line; U s is the AC line voltage; U0 is the AC side voltage of the DC / AC converter of the new energy storage microgrid; δ0 is the initial value of the voltage power angle, which is approximately 0, then cosδ0≈1; When the power system frequency is regulated, the damping ratio ζ is required to be within [0.1-0.8], so the initial virtual inertia H c0 The value range is: According to the new virtual inertia formula, the virtual inertia adjustment coefficient k H satisfy: Where: H cmax is the maximum virtual inertia of supercapacitor energy storage. When the frequency regulation of the new virtual inertia control system transitions to steady state, the angular frequency deviation can be expressed as: Where: ΔU dc is the DC bus voltage regulation value; Substituting equation (11) into equation (12), we can get the virtual inertia adjustment coefficient k H The expression is: According to the supercapacitor energy storage voltage variation range and the maximum virtual inertia, the supercapacitor energy storage capacity solution is configured, and the DC bus adjustment range is: In formula (14): Δω min , Δω max are the minimum and maximum virtual frequency respectively; according to formula (12), the optimal configuration formula of supercapacitor energy storage capacitance value can be obtained as follows: In formula (15):

2. The system according to claim 1, wherein the DC / AC converter is further used for: The frequency changes of the new energy storage microgrid are restored by detecting the DC voltage.

3. A virtual inertia control method based on a new energy storage microgrid, applied to the novel grid-type supercapacitor energy storage inertia support system as claimed in claim 1, characterized in that: include: By configuring supercapacitor energy storage to quickly release / absorb electric energy, and using a simulated rotating synchronous motor inertia control method in a DC / AC converter, the inertia support capacity of the new energy storage microgrid is improved; The virtual inertia control method further includes: dividing the frequency drop and frequency recovery caused by load input into four areas, the four areas respectively corresponding to frequency drop, frequency recovery, frequency overshoot and frequency stability, automatically increasing the virtual inertia according to the frequency increase or decrease amplitude, the large virtual inertia can suppress the frequency fluctuation, reducing the virtual inertia in the frequency recovery stage, and accelerating the frequency recovery; According to the establishment of a new type of virtual inertia is expressed as: Where: H c0 is the initial virtual inertia; Δω is the virtual frequency adjustment; α and β are the frequency deviation threshold and frequency change rate threshold, respectively. The values ​​of α and β are determined according to the characteristics of the converter; k H is the virtual inertia adjustment coefficient; The DC voltage-frequency virtual inertia control is equivalent to a typical second-order transfer function, and the control system damping ratio ζ is: Where: D is virtual damping; X is the equivalent reactance of the AC line; U s is the AC line voltage; U0 is the AC side voltage of the DC / AC converter of the new energy storage microgrid; δ0 is the initial value of the voltage power angle, which is approximately 0, then cosδ0≈1; When the power system frequency is regulated, the damping ratio ζ is required to be within [0.1-0.8], so the initial virtual inertia H c0 The value range is: According to the new virtual inertia formula, the virtual inertia adjustment coefficient k H satisfy: Where: H cmax is the maximum virtual inertia of supercapacitor energy storage. When the frequency regulation of the new virtual inertia control system transitions to steady state, the angular frequency deviation can be expressed as: Where: ΔU dc is the DC bus voltage regulation value; Substituting equation (11) into equation (12), we can get the virtual inertia adjustment coefficient k H The expression is: According to the supercapacitor energy storage voltage variation range and the maximum virtual inertia, the supercapacitor energy storage capacity solution is configured, and the DC bus adjustment range is: In formula (14): Δω min , Δω max are the minimum and maximum virtual frequency respectively; according to formula (12), the optimal configuration formula of supercapacitor energy storage capacitance value can be obtained as follows: In formula (15):

4. The method according to claim 3, characterized in that The simulated rotating synchronous motor inertia control method comprises: Definition of the rotating synchronous motor rotor rotational kinetic energy E k It is expressed as: Where, p is the number of motor pole pairs; J sg ,ω sg are the motor moment of inertia and mechanical angular velocity respectively; The inertia H of a rotating synchronous motor is expressed as: Among them, ω n , N They are the rated mechanical angular speed and rated capacity of the motor respectively; Rotational kinetic energy E k Taking the derivative with respect to time and introducing the inertia H, the motion equation of the rotor of the rotating synchronous motor is obtained as follows: Among them, P, P m , P e are the output power, mechanical power and electromagnetic power of the rotating synchronous motor respectively; ω0 and ω are the initial mechanical angular velocity and the current mechanical angular velocity respectively; A supercapacitor is configured in the DC microgrid to provide the kinetic energy required for simulating inertia. The supercapacitor releases / absorbs electrical energy through voltage transformation. Its charging and discharging power P c It is expressed as: Among them, C, S c 、u c are respectively the energy storage capacitance value, rated capacity, and output voltage of the supercapacitor; The supercapacitor energy storage release / absorption of electric energy is used to simulate the motion equation of the rotating synchronous motor rotor, and the supercapacitor inertia support equation is obtained as follows: Among them, H c is the virtual inertia of supercapacitor energy storage; ω c0 ,ω c They are the initial virtual angular frequency and current virtual angular frequency of supercapacitor energy storage respectively.

5. The method according to claim 3, characterized in that: Also includes: The frequency changes of the new energy storage microgrid are restored by detecting the DC voltage.

6. The method according to claim 5, characterized in that The method of restoring the frequency change of the new energy storage microgrid by detecting the DC voltage includes: The DC voltage-frequency virtual inertia control scheme is adopted in the DC / AC converter of the new energy storage microgrid, which is expressed as: U dc =K dc (ω-ω0)+U dc0 , Among them, U dc , U dc0 are the current value and initial value of the DC bus voltage respectively; ω and ω0 are the current angular frequency and initial angular frequency of the AC side power grid respectively, K dc is the DC inertia gain; According to the supercapacitor inertia support equation and the DC voltage-frequency virtual inertia control scheme, the DC virtual inertia gain is obtained, which is expressed as:

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