Control method and device of photovoltaic hybrid energy storage system

Abstract

The invention provides a control method and device for a photovoltaic hybrid energy storage system, and belongs to the field of power systems. The method comprises the following steps: respectively obtaining a frequency variation and a frequency change rate of an alternating current side of the photovoltaic hybrid energy storage system; determining an expected battery power variation of the energy storage battery unit based on the frequency variation and the dynamic inertia coefficient, and controlling the energy storage battery unit to operate according to the expected battery power variation, so that the energy storage battery unit absorbs a low-frequency power variation caused by the frequency variation; the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change quantity; and based on the frequency change rate, determining an expected capacitance power variable quantity of the super-capacitor unit, and controlling the super-capacitor unit to operate according to the expected capacitance power variable quantity, so that the super-capacitor unit consumes a high-frequency power variable quantity caused by the frequency change rate. The stability of the power grid system can be effectively guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of power systems, and in particular to a control method and device for a photovoltaic hybrid energy storage system. Background Art

[0002] Distributed photovoltaic power generation equipment can be connected to the power grid system through the AC busbar via the grid-connected inverter to provide power to the power grid system. However, since distributed photovoltaic power generation equipment is a static component and does not have the rotation characteristics similar to synchronous generators, after the distributed photovoltaic power generation equipment is connected to the power grid, it will lose its rotation function, reduce energy reserves, and threaten the stability of the power grid system.

[0003] In order to overcome the above problems, a virtual synchronous generator (VSG) is usually introduced to simulate the rotation characteristics of the synchronous generator, so that the power electronic interface of the distributed photovoltaic power generation equipment has better damping and inertia, thereby providing better stability for the power grid system.

[0004] VSG essentially uses virtual inertia and damping coefficients to give traditional grid-connected inverters a control strategy with generator rotation characteristics. However, since distributed photovoltaic power generation equipment has uncertain characteristics and cannot generate inertia and damping similar to generators, it is necessary to equip the DC side with energy storage units and set the corresponding inertia coefficients to provide virtual inertia and damping coefficients.

[0005] In the related technology, a single energy storage device is usually set on the DC side of the photovoltaic power generation equipment, and a fixed inertia coefficient is set to absorb the power change on the AC bus to maintain the stability of the power grid system. However, the power change on the AC bus has the characteristics of real-time random changes, and the real-time performance and flexibility of a single energy storage device and a fixed inertia coefficient are poor, which cannot meet the characteristics of real-time random changes, and thus cannot effectively ensure the stability of the power grid system. Summary of the invention

[0006] The embodiments of the present invention provide a control method and device for a photovoltaic hybrid energy storage system to solve the problem that the control method in the related art cannot effectively ensure the stability of the power grid system.

[0007] In a first aspect, an embodiment of the present invention provides a control method for a photovoltaic hybrid energy storage system, which is applied to a photovoltaic hybrid energy storage system, wherein the photovoltaic hybrid energy storage system includes an energy storage battery unit and a supercapacitor unit; the method includes:

[0008] The frequency change amount and frequency change rate of the AC side of the photovoltaic hybrid energy storage system are obtained respectively;

[0009] Based on the frequency change and the dynamic inertia coefficient, the expected battery power change of the energy storage battery unit is determined, and the operation of the energy storage battery unit is controlled according to the expected battery power change, so that the energy storage battery unit can absorb the low-frequency power change caused by the frequency change; the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change;

[0010] Based on the frequency change rate, an expected capacitance power change of the super capacitor unit is determined, and the operation of the super capacitor unit is controlled according to the expected capacitance power change, so that the super capacitor unit absorbs the high frequency power change caused by the frequency change rate.

[0011] In a possible implementation, the process of determining the value of the dynamic inertia coefficient includes:

[0012] Determine the angular velocity change rate according to the frequency change rate, and determine the angular velocity change amount according to the frequency change amount;

[0013] according to Determining the value of the dynamic inertia coefficient;

[0014] Where k represents the dynamic inertia coefficient, k0 represents the preset inertia coefficient value, and k ω1 and k ω2 represents the inertia adjustment coefficient, represents the rate of change of angular velocity, Δω represents the amount of change of angular velocity, T ω Indicates the preset threshold.

[0015] In a possible implementation, the process of determining the preset inertia coefficient value includes:

[0016] Obtaining a value of the damping ratio of the energy storage battery unit;

[0017] according to Determining the preset inertia coefficient value;

[0018] Where ξ represents the value of the damping ratio, D represents the virtual damping coefficient, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, and X f Represents the equivalent reactance of the AC line, ω G represents the synchronous angular velocity of the virtual synchronous generator, k0 represents the preset inertia coefficient value, W bat It represents the energy stored in the energy storage battery unit, E represents the three-phase reference voltage amplitude of the excitation output of the virtual synchronous generator, and U represents the actual value of the grid side voltage.

[0019] In a possible implementation, determining the expected battery power change of the energy storage battery unit based on the frequency change and the dynamic inertia coefficient includes:

[0020] Determining an angular velocity change according to the frequency change;

[0021] according to Determining the expected battery power change;

[0022] Where ΔP bat represents the expected battery power change, k represents the dynamic inertia coefficient, W bat represents the energy stored in the energy storage battery unit, ω G represents the synchronous angular velocity of the virtual synchronous generator, and Δω represents the change in angular velocity.

[0023] In a possible implementation, determining the expected capacitance power change of the supercapacitor unit based on the frequency change rate includes:

[0024] according to Determining an expected capacitance power change of the supercapacitor unit;

[0025] Where ΔP sc represents the expected capacitance power change, J represents the virtual moment of inertia, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, Indicates the rate of change of angular velocity The transient change value of .

[0026] In a possible implementation, controlling the operation of the supercapacitor unit according to the expected capacitance power change includes:

[0027] Determining a voltage deviation value on a DC side of the photovoltaic hybrid energy storage system according to the expected capacitance power change;

[0028] Obtaining a DC bus voltage on the DC side of the photovoltaic hybrid energy storage system, and performing proportional-integral control based on the DC bus voltage and the voltage deviation value to obtain a desired output current of the supercapacitor unit;

[0029] The actual output current of the supercapacitor unit is obtained, and proportional-integral control is performed based on the expected output current and the actual output current to obtain a capacitance control signal; the capacitance control signal is used to control the supercapacitor unit to operate according to the expected capacitance power change.

[0030] In a possible implementation, determining the voltage deviation value of the DC side of the photovoltaic hybrid energy storage system according to the expected capacitance power change includes:

[0031] according to Determine the voltage deviation value on the DC side of the photovoltaic hybrid energy storage system;

[0032] Wherein, Δu represents the voltage deviation value, ΔPsc represents the expected capacitance power change, U dc represents the DC bus voltage, c represents the capacitance value of the supercapacitor unit, Indicates the rate of change of angular velocity Δω represents the transient change value of angular velocity.

[0033] In a possible implementation, controlling the energy storage battery unit to operate according to the expected battery power change includes:

[0034] Acquire the voltage of the energy storage battery cell, and determine the expected current of the energy storage battery cell according to the expected battery power change and the voltage of the energy storage battery cell;

[0035] The actual current of the energy storage battery unit is obtained, and proportional integral control is performed based on the actual current and the expected current to obtain a battery control signal; the battery control signal is used to control the energy storage battery unit to operate according to the expected battery power change.

[0036] In a second aspect, an embodiment of the present invention provides a control device for a photovoltaic hybrid energy storage system, which is applied to a photovoltaic hybrid energy storage system, wherein the photovoltaic hybrid energy storage system includes an energy storage battery unit and a supercapacitor unit; the device includes:

[0037] An acquisition module, used to respectively acquire a frequency change amount and a frequency change rate on an AC side of a photovoltaic hybrid energy storage system;

[0038] A battery control module, configured to determine an expected battery power change of an energy storage battery unit based on the frequency change and the dynamic inertia coefficient, and control the operation of the energy storage battery unit according to the expected battery power change, so that the energy storage battery unit can absorb the low-frequency power change caused by the frequency change; the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change;

[0039] The capacitance control module is used to determine the expected capacitance power change of the supercapacitor unit based on the frequency change rate, and control the operation of the supercapacitor unit according to the expected capacitance power change, so that the supercapacitor unit can absorb the high-frequency power change caused by the frequency change rate.

[0040] In a possible implementation, the battery control module is specifically used to:

[0041] Determine the angular velocity change rate according to the frequency change rate, and determine the angular velocity change amount according to the frequency change amount;

[0042] according to Determining the value of the dynamic inertia coefficient;

[0043] Where k represents the dynamic inertia coefficient, k0 represents the preset inertia coefficient value, and k ω1 and k ω2 represents the inertia adjustment coefficient, represents the rate of change of angular velocity, Δω represents the amount of change of angular velocity, T ω Indicates the preset threshold.

[0044] The embodiment of the present invention provides a photovoltaic hybrid energy storage system method and device. By using the energy storage battery unit to absorb the low-frequency power change caused by the frequency change, and using the supercapacitor unit to absorb the high-frequency power change caused by the frequency change rate, the characteristics of the energy storage battery unit with high energy density and the supercapacitor unit with high power density can be fully utilized, so that the energy storage battery unit and the supercapacitor unit can share the overall power change on the AC side, thereby quickly absorbing the system power change to maintain system stability. In addition, the energy storage battery unit dynamically adjusts the value of the dynamic inertia coefficient based on the frequency change amount and the frequency change rate, so that the energy storage battery unit can provide inertia support more flexibly, thereby reducing the damage caused by power fluctuations, thereby further improving system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 is a schematic structural diagram of a photovoltaic hybrid energy storage system provided by an embodiment of the present invention;

[0047] Figure 2 is a flow chart of an implementation method of a photovoltaic hybrid energy storage system control method provided by an embodiment of the present invention;

[0048] Figure 3 is a VSG control structure diagram of a photovoltaic hybrid energy storage system provided by an embodiment of the present invention;

[0049] Figure 4 is a control structure diagram of an energy storage battery unit provided by an embodiment of the present invention;

[0050] Figure 5 is a schematic diagram of angular velocity change provided by an embodiment of the present invention;

[0051] Figure 6 is a control structure diagram of a supercapacitor unit provided by an embodiment of the present invention;

[0052] Figure 7(a) is a frequency comparison diagram under different control strategies under the load sudden increase condition;

[0053] FIG7( b ) is a comparison diagram of the output of the energy storage battery unit under different control strategies under the load sudden increase condition;

[0054] FIG8( a ) is a comparison diagram of DC bus voltage under different control strategies under load sudden increase conditions;

[0055] FIG8( b ) is a schematic diagram of the output of the supercapacitor unit under a sudden load increase condition;

[0056] Figure 9(a) is a frequency comparison diagram under different control strategies under the condition of continuous load change;

[0057] FIG9( b ) is a comparison diagram of the output of the energy storage battery unit under different control strategies under the condition of continuous load change;

[0058] Figure 10(a) is a comparison diagram of DC bus voltage under different control strategies under load sudden increase conditions;

[0059] FIG10( b ) is a schematic diagram of the output of the supercapacitor unit under a sudden load increase condition;

[0060] FIG11( a ) is a schematic diagram showing the change of the dynamic inertia coefficient under the load sudden increase condition;

[0061] FIG11( b ) is a schematic diagram showing the change of the dynamic inertia coefficient under the condition of continuous load change;

[0062] Fig.12 It is a schematic diagram of the structure of a control device for a photovoltaic hybrid energy storage system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0063] In the following description, specific details such as specific system structures, technologies, etc. are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present invention. However, it should be clear to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present invention.

[0064] Photovoltaic power generation equipment is connected to the grid-connected inverter via the DC bus to convert DC power into AC power. The grid-connected inverter is connected to the power grid system and daily loads via the AC bus to provide AC power to the power grid system and support daily loads. However, considering that the output of photovoltaic power generation equipment is uncertain, and the power grid system and daily loads also have the characteristics of random changes, it is easy for the input power and output power on the AC bus to not match, that is, power fluctuations occur, threatening the stability of the power grid system.

[0065] Since photovoltaic power generation equipment is a static component, it cannot generate inertia and damping, which leads to the photovoltaic power generation equipment itself being unable to adjust the input power on the AC bus. In other words, photovoltaic power generation equipment cannot solve the problem of power fluctuation. To solve this problem, VSG technology is usually used to make the AC bus have better damping and inertia, thereby solving the problem of power fluctuation. When applying VSG technology, it is necessary to equip the DC bus with an energy storage unit and set the corresponding inertia coefficient to provide virtual inertia and damping coefficient.

[0066] In the related art, a single energy storage device is usually set on the DC bus, and a fixed inertia coefficient is set to absorb the power variation on the AC bus to maintain the stability of the power grid system. However, the power variation on the AC bus has the characteristics of real-time random changes, and the real-time performance and flexibility of a single energy storage device and a fixed inertia coefficient are poor, which cannot meet the characteristics of real-time random changes, and thus cannot effectively ensure the stability of the power grid system.

[0067] In order to effectively ensure the stability of the power grid system, in the implementation of the present application, the energy storage battery unit is used to absorb the low-frequency power change caused by the frequency change, and the supercapacitor unit is used to absorb the high-frequency power change caused by the frequency change rate. The characteristics of the energy storage battery unit with high energy density and the supercapacitor unit with high power density can be fully utilized, so that the energy storage battery unit and the supercapacitor unit can share the overall power change on the AC side, thereby quickly absorbing the system power change, meeting the real-time requirements, and maintaining system stability. In addition, the energy storage battery unit dynamically adjusts the value of the dynamic inertia coefficient based on the frequency change and the frequency change rate, which can enable the energy storage battery unit to provide inertia support more flexibly, thereby reducing the damage caused by random power fluctuations, thereby further improving system stability.

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0069] First, the photovoltaic hybrid energy storage system is introduced. Figure 1 , Figure 1 The schematic diagram of the structure of the photovoltaic hybrid energy storage system provided by the embodiment of the present invention is as follows. Figure 1As shown, the photovoltaic hybrid energy storage system of the embodiment of the present invention mainly includes: photovoltaic power generation equipment, hybrid energy storage unit, grid-connected inverter, AC main grid and daily load. Among them, the photovoltaic power generation equipment and the hybrid energy storage unit are connected to the grid-connected inverter via a DC bus. The grid-connected inverter is connected to the AC main grid and the daily load via the AC bus. The photovoltaic power generation equipment mainly includes a photovoltaic array and a DC-DC converter, which works in the maximum power point tracking mode (Maximum power point tracking, MPPT), which is used to provide photovoltaic output P pv The grid-connected inverter is controlled by VSG technology to provide better damping and inertia. The hybrid energy storage unit mainly includes energy storage battery unit and supercapacitor unit. Among them, the energy storage battery unit is used to input or output battery energy storage power P bat The supercapacitor unit is used to input or output the capacitor energy storage power P sc The energy storage battery unit and the supercapacitor unit jointly absorb the power changes on the AC bus to maintain the stability of the power grid. The energy storage battery unit includes an energy storage battery and a DC-DC converter connected thereto. The supercapacitor unit includes a supercapacitor and a DC-DC converter connected thereto.

[0070] Here, the power change of the photovoltaic hybrid energy storage system can be expressed as:

[0071] ΔP bat '+ΔP sc '=ΔP l '-ΔP g '-ΔP pv '

[0072] Where ΔP bat ' represents the power change of the energy storage battery unit, ΔP sc ' represents the power change of the supercapacitor unit, ΔP l ' represents the load power change, ΔP g ' represents the power change of the virtual synchronous machine, ΔP pv 'Indicates the power change of photovoltaic power generation equipment.

[0073] In the embodiment of the present invention, the operation of the energy storage battery unit is controlled according to the inertia control strategy based on the dynamic inertia coefficient, so as to provide inertial support more flexibly. In the embodiment of the present invention, the operation of the supercapacitor is controlled according to the voltage deviation control strategy, so as to achieve the purpose of making the supercapacitor unit share the power variation on the AC bus by adjusting the DC bus voltage, which can not only suppress the power fluctuation of the AC bus, but also suppress the voltage fluctuation of the DC bus.

[0074] Based on the above photovoltaic hybrid energy storage system, an embodiment of the present invention provides a control method for the photovoltaic hybrid energy storage system. Figure 2 The implementation flow chart of the control method of the photovoltaic hybrid energy storage system provided by the embodiment of the present invention is detailed as follows:

[0075] Step 201, respectively obtain the frequency change amount and frequency change rate of the AC side of the photovoltaic hybrid energy storage system.

[0076] Here, the AC side of the photovoltaic hybrid energy storage system is Figure 1 The AC busbar connects the AC main grid and the daily load. The frequency change and frequency change rate on the AC busbar are the frequency change and frequency change rate of the AC main grid.

[0077] The frequency change amount and frequency change rate of the AC main power grid will cause power fluctuations on the AC bus. The embodiment of the present invention can determine the power change amount on the AC bus through the frequency change amount and frequency change rate, and then control the energy storage battery unit and the supercapacitor unit to jointly absorb the power change amount to suppress the power fluctuations on the AC bus, thereby maintaining the stability of the frequency of the AC main power grid.

[0078] Step 202, based on the frequency change and the dynamic inertia coefficient, determine the expected battery power change of the energy storage battery unit, and control the operation of the energy storage battery unit according to the expected battery power change, so that the energy storage battery unit can absorb the low-frequency power change caused by the frequency change. Here, the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change.

[0079] The applicant has found that the power variation caused by the frequency variation is a low-frequency power component, which changes slowly. The energy storage battery unit has the characteristic of high energy density, which is convenient for slowly absorbing a large amount of power variation. Therefore, the embodiment of the present invention uses the energy storage battery unit to absorb the low-frequency power variation caused by the frequency variation.

[0080] In the embodiment of the present invention, an inertia control strategy may be used when controlling the operation of the energy storage battery unit. When using the inertia control strategy to control the operation of the energy storage battery, the expected battery power change of the energy storage battery unit may be determined based on the frequency change and the dynamic inertia coefficient, and then proportional integral control may be performed based on the expected battery power change to obtain a battery control signal. The battery control signal is used to control the energy storage battery unit to operate according to the expected battery power change.

[0081] In addition, different from the fixed inertia coefficient in the related art, the embodiment of the present invention adopts a dynamically changing dynamic inertia coefficient, and the value of the dynamic inertia coefficient changes accordingly with the frequency change rate and the frequency change amount, so that the energy storage battery unit can more flexibly provide inertia support of different sizes to adapt to the characteristics of random changes in power changes.

[0082] Step 203, based on the frequency change rate, determine the expected capacitance power change of the super capacitor unit, and control the operation of the super capacitor unit according to the expected capacitance power change, so that the super capacitor unit absorbs the high frequency power change caused by the frequency change rate.

[0083] The applicant has found that the power variation caused by the frequency variation rate is a high-frequency power component, which changes rapidly. The supercapacitor unit has the characteristic of high power density, which is convenient for quickly absorbing the power variation. Therefore, the embodiment of the present invention uses the supercapacitor unit to absorb the high-frequency power variation caused by the frequency variation rate.

[0084] In the embodiment of the present invention, a voltage deviation control strategy is adopted to control the supercapacitor unit to operate according to the expected capacitance power change, so that the supercapacitor can absorb the high-frequency power change caused by the frequency change rate by adjusting the DC bus voltage. This can not only suppress the power fluctuation on the AC bus, but also suppress the voltage fluctuation on the DC bus, thereby maintaining the DC side voltage stability.

[0085] In some embodiments, when a voltage deviation control strategy is used to control a supercapacitor unit to operate according to an expected capacitance power change, the voltage deviation value on the DC side of the photovoltaic hybrid energy storage system can be determined based on the expected capacitance power change; then, proportional-integral control is performed based on the voltage deviation value to obtain an expected output current of the supercapacitor unit; then, proportional-integral control is performed again based on the expected output current to obtain a capacitance control signal; the capacitance control signal is used to control the supercapacitor unit to operate according to the expected capacitance power change.

[0086] Compared with the prior art, the present application utilizes the energy storage battery unit to absorb the low-frequency power change caused by the frequency change, and utilizes the supercapacitor unit to absorb the high-frequency power change caused by the frequency change rate, which can fully utilize the characteristics of the energy storage battery unit with high energy density and the supercapacitor unit with high power density, so that the energy storage battery unit and the supercapacitor unit can share the overall power change on the AC side, thereby quickly absorbing the system power change, meeting the real-time requirements, and maintaining the stability of the system. In addition, the energy storage battery unit dynamically adjusts the value of the dynamic inertia coefficient based on the frequency change and the frequency change rate, which can enable the energy storage battery unit to provide inertia support more flexibly, thereby reducing the damage caused by random power fluctuations, thereby further improving the stability of the system.

[0087] In some embodiments, the angular velocity change can be determined based on the frequency change, and then Determine the expected battery power change.

[0088] Where ΔP bat represents the expected battery power change, k represents the dynamic inertia coefficient, W batRepresents the energy stored in the energy storage battery unit, ω G represents the synchronous angular velocity of the virtual synchronous generator, and Δω represents the change in angular velocity.

[0089] In some embodiments, the Determining an expected capacitance power change of the supercapacitor unit;

[0090] Where ΔP sc represents the expected capacitance power change, J represents the virtual moment of inertia, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, Indicates the rate of change of angular velocity The transient change value of .

[0091] The following is an introduction to the derivation process of the formulas for the expected battery power change and the expected capacitor power change.

[0092] Figure 3 The VSG control structure diagram of the photovoltaic hybrid energy storage system. Figure 3 , PV is a photovoltaic array, the grid-connected inverter adopts MPPT control, C dc is the photovoltaic DC side capacitance; L f , R f and C f They represent filter inductance, filter resistance and filter capacitance respectively; Lg and Rg represent line reactance and line resistance respectively; u a 、u b and u c Respectively represent the three-phase output voltage of VSG; i a 、i b and i c Respectively represent the three-phase output current on the grid side; P ref Represents the reference value of active power output / absorption of photovoltaic hybrid energy storage VSG, P e Indicates the actual output / absorption value of photovoltaic hybrid energy storage VSG; Q ref Represents the reference value of reactive power output / absorption of photovoltaic hybrid energy storage VSG, Q e Indicates the actual value of reactive power output / absorption of photovoltaic hybrid energy storage VSG; U ref represents the grid-side voltage reference value, U represents the grid-side voltage actual value; ω represents the VSG virtual electrical angular velocity, δ represents the VSG power angle; E represents the VSG excitation output three-phase reference voltage amplitude; E a 、E b and E c Indicates the VSG output three-phase reference voltage amplitude.

[0093] According to the above Figure 3 , the following motion equation can be established to reflect the inertia and damping characteristics of VSG, namely:

[0094] Where, J represents the virtual moment of inertia; ω0 represents the virtual rated electrical angular velocity of VSG, ω0=2πf0, f0 is the rated frequency 50Hz. m represents the VSG input power; D is the virtual damping coefficient.

[0095] Since VSG participates in grid frequency regulation by changing the input active power, its input active power can be divided into two parts: one is the active power reference value P ref , the second is the power deviation value caused by frequency change,

[0096] That is: P m =P ref +ΔP=P ref +D p (ω0-ω)(2)

[0097] Where D p is the active power-frequency droop coefficient.

[0098] By adjusting the excitation output three-phase reference voltage amplitude E in the VSG, the output reference voltage and reactive power are changed, and the reactive power-voltage droop characteristic is presented to the outside, that is:

[0099] E=E0+D q (Q ref -Q e )+D v (U ref -U)(3)

[0100] Where, E0 is the rated value of the VSG voltage amplitude; D q is the reactive power-voltage droop coefficient; D v is the pressure difference proportional coefficient.

[0101] According to formula (1), the model of VSG in transient process can be obtained, namely:

[0102]

[0103] In the formula, is the power change of VSG caused by frequency, which is related to the rate of change of frequency, ΔP m Indicates the change in VSG input power, ΔP e It represents the change in the actual value of the photovoltaic hybrid energy storage VSG output / absorption, and Δω=ω0-ω represents the change in angular velocity.

[0104] From formula (2), we can see that ΔP m =ΔP=D p (ω0-ω)=D p Δω, that is, ΔP mRelated to the frequency change and the steady-state value is D p Δω; ΔP e is the output change of the DC side; DΔω is the damping torque change caused by the frequency change. It can be seen that ΔP e and DΔω is expressed as the power demand, With ΔP m It is expressed as the change of VSG output. From this, we can get the following formulas:

[0105]

[0106] ΔP bat =ΔP m =D p Δω(6)

[0107]

[0108] According to the above, With ΔP m It is expressed as the VSG output change, that is, the power change that needs to be shared by the energy storage battery unit and the supercapacitor unit. m It is related to the frequency change. It is related to the frequency change rate. Therefore, in the embodiment of the present invention, ΔP m Assigned to the energy storage battery unit, Assigned to the supercapacitor unit.

[0109] For the energy storage battery unit, the charge of the energy storage battery unit at time t is:

[0110]

[0111] In the formula, γ SOC (t) is the charge of the energy storage battery unit at time t; Q N is the rated capacity of the energy storage battery unit; i bat is the current of the energy storage battery unit at time t; Q bat is the remaining power of the energy storage battery unit at time t.

[0112] The energy stored in the energy storage battery unit W can be obtained by formula (8): bat :

[0113] W bat =∫u bat i bat dt=∫u bat dQ N (1-γ SOC (t)) = u bat Q N (1-γ SOC (t)) = ubat Q N γ SOC (0) (9)

[0115] In the formula, ubat represents the voltage of the energy storage battery unit, γ SOC (0) represents the initial charge of the energy storage battery unit.

[0116] According to the above formula (9), we can get:

[0117]

[0118] In the formula, γ SOC Indicates the charge of the energy storage battery unit, J bat Represents the virtual moment of inertia of the energy storage battery unit.

[0119] From formula (10), we get:

[0120] The virtual moment of inertia of the energy storage battery is related to its rated voltage, rated capacity, state of charge and system frequency. Substituting formula (9) into formula (11), we can get:

[0121]

[0122] Where k is the dynamic inertia coefficient, which is the ratio of the rate of change of the energy storage battery charge to the rate of change of the synchronous machine speed.

[0123] According to formula (10),

[0124]

[0125] According to formula (14), we can get:

[0126]

[0127] According to formula (15), we can get:

[0128]

[0129] Therefore, the embodiments of the present invention are based on Determine the expected battery power change.

[0130] After determining the expected battery power variation of the energy storage battery unit, the embodiment of the present invention adopts an inertia control strategy to control the energy storage battery unit to operate according to the expected battery power variation, so that the energy storage battery unit shares the low-frequency power variation caused by the frequency variation.

[0131] See Figure 4, when the inertia control strategy is adopted to control the energy storage battery unit, the frequency change is first determined according to the actual frequency value f and the rated frequency f0, and then the angular velocity change Δω is determined according to the frequency change. Then, the angular velocity change and the dynamic inertia coefficient are substituted into the above formula (15) to obtain the expected battery power change ΔP bat Then, the energy storage battery cell voltage u is obtained bat , according to the expected battery power change ΔP bat and the energy storage battery unit voltage u bat , determine the expected current of the energy storage battery unit; obtain the actual current i of the energy storage battery unit bat , a proportional integral control is performed based on the actual current and the expected current to obtain a battery control signal. The battery control signal can be a PWM signal, which is used to control the energy storage battery unit to operate according to the expected battery power change.

[0132] In the related art, the dynamic inertia coefficient k is usually set as a constant to characterize the ratio of the rate of change of the charge of the energy storage battery to the rate of change of the synchronous machine speed. However, when the dynamic inertia coefficient k is a constant, it is impossible to accurately provide the corresponding inertia according to the system inertia requirements. If k is too small, it will affect the system frequency reduction process, and if k is too large, it will be detrimental to the system frequency recovery process.

[0133] To solve the above problems, an embodiment of the present invention dynamically adjusts the value of the dynamic inertia coefficient according to the frequency change amount and the frequency change rate, so that the dynamic inertia coefficient can change dynamically according to the frequency, thereby achieving the purpose of accurately providing corresponding inertia according to the system inertia requirement.

[0134] In some embodiments, when determining the value of the dynamic inertia coefficient, the angular velocity change rate can be determined according to the frequency change rate, and the angular velocity change amount can be determined according to the frequency change amount; then, according to Determine the value of the dynamic inertia coefficient.

[0135] Where k represents the dynamic inertia coefficient, k0 represents the preset inertia coefficient value, and k ω1 and k ω2 represents the inertia adjustment coefficient, represents the rate of change of angular velocity, Δω represents the amount of change of angular velocity, T ω Here, the preset inertia coefficient value is the inertia coefficient when the system is in a stable state.

[0136] See also Figure 5 The reason for this design is that the inventor found that during the sudden increase of load, the change process of angular velocity can be divided into four intervals: I: t1-t2, which is the angular velocity decrease interval, that is, the frequency decrease interval, the VSG virtual electrical angular velocity is less than the rated electrical angular velocity of the grid, and the angular velocity change rate It increases first and then decreases to 0, so k should be increased in this interval to prevent the frequency from dropping deeply; II: t2-t3 is the angular velocity recovery interval, that is, the frequency recovery interval, the VSG virtual electrical angular velocity is still less than the rated electrical angular velocity of the grid, but the VSG virtual electrical angular velocity gradually increases, and the angular velocity change rate In this interval, k should be reduced to quickly restore the frequency to the rated frequency. III: t3-t4, the frequency overshoot interval, that is, the angular velocity overshoot interval, similar to interval I, k can be increased. IV: t4-t5, the frequency stability interval, similar to interval II, k can be reduced.

[0137] The values ​​of the dynamic inertia coefficient k can be found in Table 1:

[0138] Interval dω / dt Δω Δω(dω / dt) The value of k Ⅰ <0 <0 >0 Increase, then decrease Ⅱ >0 <0 <0 Decrease, then increase Ⅲ >0 >0 >0 Appropriate increase Ⅳ <0 >0 <0 Appropriate reduction

[0139] From Table 1, we can see that when When , the value of the dynamic inertia coefficient can be reduced. , the value of the dynamic inertia coefficient can be increased. Determine the value of the dynamic inertia coefficient.

[0140] The value of the preset inertia coefficient can be determined according to the value of the damping ratio of the energy storage battery unit. In order to make the energy storage battery VSG have a faster response speed in the system frequency modulation, and at the same time not let the output damping produce active frequency oscillation, the active loop can be placed in an underdamped loop state, that is, 0<ξ<1.

[0141] The damping ratio and the inertia coefficient when the system is in a stable state, that is, the preset inertia coefficient value, have the following mathematical relationship:

[0142] Where ξ represents the value of the damping ratio, D represents the virtual damping coefficient, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, and X f Represents the equivalent reactance of the AC line, ω G represents the synchronous angular velocity of the virtual synchronous generator, k0 represents the preset inertia coefficient value, W bat It represents the energy stored in the energy storage battery unit, E represents the three-phase reference voltage amplitude of the excitation output of the virtual synchronous generator, and U represents the actual value of the grid side voltage.

[0143] Therefore, the embodiment of the present invention can first determine the value of the damping ratio, and then determine the value of the inertia coefficient when the system is in a stable state, that is, the preset inertia coefficient value, based on the value of the damping ratio and the above mathematical relationship.

[0144] For the supercapacitor unit, in order to maintain the stability of the DC bus voltage and absorb the high-frequency power changes on the AC bus, the embodiment of the present invention adopts a voltage deviation control strategy to control the operation of the supercapacitor unit, that is, the voltage change on the DC bus is determined by the frequency fluctuation on the AC bus, and then the output signal of the supercapacitor is added to the DC bus to maintain the stability of the DC bus. At the same time, it can also absorb the high-frequency power changes on the AC bus.

[0145] When describing the mathematical relationship between the frequency change on the AC bus and the voltage change on the DC bus, the frequency change can be first converted into the angular velocity change, and then the mathematical relationship between the angular velocity change on the AC bus and the voltage change on the DC bus can be determined: Δu = k v Δω(17)

[0146] In the formula, Δu represents the voltage change, k v represents the voltage coefficient, and Δω represents the change in angular velocity. Here, k v Is an unknown parameter.

[0147] According to formula (17), the voltage on the DC bus changes with the AC main grid. If the frequency of the AC main grid decreases, the angular velocity decreases, Δu decreases accordingly, the voltage on the DC bus decreases, and the supercapacitor unit outputs power; if the frequency of the AC main grid increases, the angular velocity increases, Δu increases accordingly, the voltage on the DC bus increases, and the supercapacitor unit absorbs power. As the AC bus power is gradually adjusted, the DC bus voltage tends to be stable, the supercapacitor unit absorbs / outputs power gradually decreases and tends to 0, and finally the energy storage battery unit provides the required power.

[0148] In the process of DC bus voltage change, the expected capacitance power change of the supercapacitor unit can also be expressed as:

[0149]

[0150] In the formula, Δu dc Indicates the voltage change of the DC bus, Δi sc Indicates the output current change of the supercapacitor unit, u dc represents the DC bus voltage, c represents the capacitance value of the supercapacitor unit, Indicates the rate of change of voltage.

[0151] According to the above formula (17) and formula (18), we can get:

[0152]

[0153] Combining equation (7) and equation (19), we can get:

[0154]

[0155] Substituting formula (20) into formula (7), we can obtain:

[0156]

[0157] Therefore, the embodiments of the present invention are based on Determine the voltage deviation value on the DC side of the photovoltaic hybrid energy storage system;

[0158] Among them, Δu represents the voltage deviation value, ΔP sc Indicates the expected capacitance power change, U dc represents the DC bus voltage, c represents the capacitance value of the supercapacitor unit, Indicates the rate of change of angular velocity Δω represents the transient change value of angular velocity.

[0159] See also Figure 6 When the voltage deviation control strategy is used to control the operation of the supercapacitor, the voltage deviation value Δu can be determined according to the above formula (21), and then the DC bus voltage u on the DC side of the photovoltaic hybrid energy storage system can be obtained. dc , and based on the DC bus voltage u dc The proportional-integral control is performed with the voltage deviation value Δu to obtain the expected output current i of the supercapacitor unit. ref ; Next, obtain the actual output current i of the supercapacitor unit sc , and based on the expected output current i ref and the actual output current i sc Proportional integral control is performed to obtain a capacitor control signal, which is a PWM signal used to control the supercapacitor unit to operate according to the desired capacitance power change, while also smoothing the voltage fluctuation on the DC bus.

[0160] In order to verify the effectiveness of the photovoltaic energy storage system control method provided by the embodiment of the present invention in providing inertia support for the power grid system and reducing the DC bus voltage fluctuation, a Matlab / Simulink platform is built as follows: Figure 1 The microgrid simulation model shown in Figure 2 shows that the photovoltaic system works in the maximum power tracking mode with a rated output of 20 kW. The hybrid energy storage unit is connected to the DC bus, and there is a virtual synchronous generator on the AC side with a rated power of 20 kW. The specific parameters in the simulation are shown in Table 2.

[0161] Table 2 Simulation parameters

[0162] Simulation parameters Numeric <![CDATA[Q N / kV×A]]> 100 <![CDATA[γ SOC (0)]]> 80％ <![CDATA[k0]]> <![CDATA[1×10 4 ]]> <![CDATA[k ω1 ]]> <![CDATA[0.85×10 4 ]]> <![CDATA[k ω2 ]]> <![CDATA[0.9×10 4 ]]> <![CDATA[T ω ]]> 0.2 c / F 1 <![CDATA[u dc / V]]> 750

[0163] Scenario 1: Load Sudden Increase Simulation Analysis

[0164] In this embodiment, the load sudden increase simulation condition is set as follows: the simulation duration is 6s, the initial load is 25kW, and the load suddenly increases by 15kW at 3s. When the energy storage battery unit is used to share the low-frequency power variation, the traditional inertia control strategy with a fixed inertia coefficient and the inertia control strategy based on a dynamic inertia coefficient proposed in the embodiment of the present invention are used for simulation comparison. The comparison results are shown in Figures 7(a) and 7(b).

[0165] As shown in Figure 7(a), when the load on the AC side of the system suddenly increases, the frequency drops rapidly. When the dynamic inertia coefficient control is introduced, the energy storage battery unit can flexibly respond to the frequency fluctuation caused by the sudden increase in load, and provide a larger inertia in the frequency reduction stage. The lowest frequency point increases from 49.813Hz to 49.841Hz. Reducing the inertia in the frequency recovery stage is more conducive to frequency recovery. It can be seen that compared with traditional inertia control, the introduction of dynamic inertia coefficient control in the energy storage battery unit can effectively provide inertia support when the system frequency fluctuates, thereby reducing the maximum frequency deviation. As shown in Figure 7(b), when the energy storage battery unit introduces dynamic inertia coefficient control, it can provide more inertia for the system. When the load suddenly increases, the active output can be quickly increased to 31kW, which is about 3kW more than the traditional inertia control output, and finally stabilized at around 15kW, thereby virtualizing the inertia response and providing power support for the system.

[0166] When the supercapacitor unit is used to share the high-frequency power variation, a traditional inertia control strategy and a voltage deviation control strategy proposed in an embodiment of the present invention are used for simulation comparison. The comparison results are shown in FIG8( a ).

[0167] As shown in Figure 8(a), a sudden increase in load will cause the DC bus voltage to drop. When the supercapacitor unit introduces voltage deviation control, it will delay the bus voltage fluctuation and reduce the voltage drop amplitude. However, traditional inertial control cannot alleviate the large voltage fluctuation. In severe cases, it may cause the system to shut down due to low voltage.

[0168] FIG8(b) is the output waveform of the supercapacitor under voltage deviation control. Since the supercapacitor unit is set in this embodiment to bear the high-frequency component and smooth the voltage fluctuation, the output is only when the load increases suddenly, and the output is 0 at other times. The situation of sudden load reduction is similar and will not be described in detail here.

[0169] Scenario 2: Simulation analysis of continuous load changes

[0170] The simulation conditions are set as follows: simulation duration is 8s, initial load is 20kW, and random active power fluctuation of ±40kW is set during the simulation period. When the energy storage battery unit is used to share the low-frequency power variation, the traditional inertia control strategy with a fixed inertia coefficient and the inertia control strategy based on a dynamic inertia coefficient proposed in the embodiment of the present invention are used for simulation comparison. The comparison results are shown in Figures 9(a) and 9(b).

[0171] As shown in Figure 9(a), an increase in load will cause the system frequency to decrease, and a decrease in load will cause the system frequency to increase. The frequency fluctuation range under dynamic coefficient control is smaller than that under traditional inertia control. Under both control modes, the highest frequency point decreases from 50.153Hz to 50.138Hz, and the lowest frequency point increases from 49.812Hz to 49.836Hz. It can be seen that the introduction of dynamic coefficient control in energy storage batteries can flexibly provide inertia support for the system. As shown in Figure 9(b), under continuous load fluctuations, dynamic coefficient control can more effectively provide active output for the system and alleviate load fluctuations compared to traditional control.

[0172] When the supercapacitor unit is used to share the high-frequency power variation, a traditional inertia control strategy and a voltage deviation control strategy proposed in an embodiment of the present invention are used for simulation comparison. The comparison results are shown in FIG10( a ).

[0173] As shown in Figure 10(a), an increase or decrease in load will cause the DC bus voltage to drop or rise. Compared with traditional inertial control, voltage deviation control can more effectively reduce bus voltage fluctuations. The highest voltage point drops from 758.4V to 756.2V, and the lowest voltage point rises from 733.6V to 738.4V, alleviating the voltage fluctuation amplitude. The output of the supercapacitor is shown in Figure 10(b). The supercapacitor can use its power density to smooth the high-frequency component of the load and provide power support.

[0174] Figures 11(a) and 11(b) show the changes in the dynamic inertia coefficient k under the above two simulation conditions. It can be seen from the figure that k changes with the change of the system angular velocity, which plays an important role in the energy storage battery unit providing inertia support for the power grid system in a short time. The spikes in the change of k are caused by the sudden change of dω / dt at the inflection point of the angular velocity.

[0175] In summary, the control method of the photovoltaic hybrid energy storage system provided in this embodiment can enable the energy storage battery unit to flexibly control the active output according to the frequency change, and enable the supercapacitor to smooth the bus voltage fluctuation, thereby reducing the damage caused by the frequency fluctuation, and reasonably using the advantages of the energy storage battery unit and the supercapacitor unit, the stability of the system is optimized to a certain extent.

[0176] It should be understood that the order of execution of the steps in the above embodiment does not necessarily mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0177] The following is an embodiment of the device of the present invention. For details not described in detail therein, reference may be made to the corresponding method embodiment described above.

[0178] Fig.12 The schematic diagram of the structure of the control device of the photovoltaic hybrid energy storage system provided by the embodiment of the present invention is shown. For the convenience of explanation, only the part related to the embodiment of the present invention is shown, which is described in detail as follows:

[0179] like Fig.12 As shown, the control device 12 of the photovoltaic hybrid energy storage system includes: an acquisition module 121 , a battery control module 122 and a capacitor control module 123 .

[0180] An acquisition module 121 is used to respectively acquire a frequency change amount and a frequency change rate of an AC side of a photovoltaic hybrid energy storage system;

[0181] The battery control module 122 is used to determine the expected battery power change of the energy storage battery unit based on the frequency change and the dynamic inertia coefficient, and control the operation of the energy storage battery unit according to the expected battery power change, so that the energy storage battery unit can absorb the low-frequency power change caused by the frequency change; the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change;

[0182] The capacitance control module 123 is used to determine the expected capacitance power change of the super capacitor unit based on the frequency change rate, and control the operation of the super capacitor unit according to the expected capacitance power change, so that the super capacitor unit absorbs the high frequency power change caused by the frequency change rate.

[0183] In a possible implementation, the battery control module 122 is specifically configured to:

[0184] Determine the angular velocity change rate according to the frequency change rate, and determine the angular velocity change amount according to the frequency change amount;

[0185] according to Determine the value of the dynamic inertia coefficient;

[0186] Where k represents the dynamic inertia coefficient, k0 represents the preset inertia coefficient value, and k ω1 and k ω2 represents the inertia adjustment coefficient, represents the rate of change of angular velocity, Δω represents the amount of change of angular velocity, T ω Indicates the preset threshold.

[0187] In a possible implementation, the battery control module 122 is specifically used to: obtain a value of a damping ratio of an energy storage battery unit;

[0188] according to Determine the preset inertia coefficient value;

[0189] Where ξ represents the value of the damping ratio, D represents the virtual damping coefficient, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, and X frepresents the equivalent reactance of the AC line, ω G represents the synchronous angular velocity of the virtual synchronous generator, k0 represents the preset inertia coefficient value, W bat It represents the energy stored in the energy storage battery unit, E represents the three-phase reference voltage amplitude of the excitation output of the virtual synchronous generator, and U represents the actual value of the grid side voltage.

[0190] In a possible implementation, the battery control module 122 is specifically configured to:

[0191] According to the frequency change, determine the angular velocity change;

[0192] according to determining an expected battery power change;

[0193] Where ΔP bat represents the expected battery power change, k represents the dynamic inertia coefficient, W bat Represents the energy stored in the energy storage battery unit, ω G represents the synchronous angular velocity of the virtual synchronous generator, and Δω represents the change in angular velocity.

[0194] In a possible implementation, the capacitance control module 123 is specifically configured to:

[0195] according to Determining an expected capacitance power change of the supercapacitor unit;

[0196] Where ΔP sc represents the expected capacitance power change, J represents the virtual moment of inertia, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, Indicates the rate of change of angular velocity The transient change value of .

[0197] In a possible implementation, the capacitance control module 123 is specifically configured to:

[0198] Determine the voltage deviation value of the DC side of the photovoltaic hybrid energy storage system according to the expected capacitance power change;

[0199] The DC bus voltage on the DC side of the photovoltaic hybrid energy storage system is obtained, and proportional-integral control is performed based on the DC bus voltage and the voltage deviation value to obtain the expected output current of the supercapacitor unit;

[0200] The actual output current of the supercapacitor unit is obtained, and proportional-integral control is performed based on the expected output current and the actual output current to obtain a capacitance control signal; the capacitance control signal is used to control the supercapacitor unit to operate according to the expected capacitance power change.

[0201] In a possible implementation, the capacitance control module 123 is specifically configured to:

[0202] according to Determine the voltage deviation value on the DC side of the photovoltaic hybrid energy storage system;

[0203] Among them, Δu represents the voltage deviation value, ΔP sc Indicates the expected capacitance power change, U dc represents the DC bus voltage, c represents the capacitance value of the supercapacitor unit, Indicates the rate of change of angular velocity Δω represents the transient change value of angular velocity.

[0204] In a possible implementation, the battery control module 122 is specifically configured to:

[0205] Obtaining the voltage of the energy storage battery cell, and determining the expected current of the energy storage battery cell according to the expected battery power change and the voltage of the energy storage battery cell;

[0206] The actual current of the energy storage battery unit is obtained, and proportional integral control is performed based on the actual current and the expected current to obtain a battery control signal; the battery control signal is used to control the energy storage battery unit to operate according to the expected battery power change.

[0207] This device embodiment can be used to implement the control method of the photovoltaic hybrid energy storage system provided in the above method embodiment. Its technical principle and implementation effect are the same as those of the above method embodiment, and will not be repeated here.

[0208] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0209] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium. When the computer program is executed by the processor, it can implement the steps of the above-mentioned control method embodiments of each photovoltaic hybrid energy storage system. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0210] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A control method for a photovoltaic hybrid energy storage system, characterized in that: Applied to a photovoltaic hybrid energy storage system, the photovoltaic hybrid energy storage system includes an energy storage battery unit and a supercapacitor unit; the method includes: The frequency change amount and frequency change rate of the AC side of the photovoltaic hybrid energy storage system are obtained respectively; Based on the frequency change and the dynamic inertia coefficient, the expected battery power change of the energy storage battery unit is determined, and the operation of the energy storage battery unit is controlled according to the expected battery power change, so that the energy storage battery unit can absorb the low-frequency power change caused by the frequency change; the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change; Based on the frequency change rate, an expected capacitance power change of the super capacitor unit is determined, and the operation of the super capacitor unit is controlled according to the expected capacitance power change, so that the super capacitor unit absorbs the high frequency power change caused by the frequency change rate.

2. The control method of the photovoltaic hybrid energy storage system according to claim 1, characterized in that: The process of determining the value of the dynamic inertia coefficient includes: Determine the angular velocity change rate according to the frequency change rate, and determine the angular velocity change amount according to the frequency change amount; according to Determining the value of the dynamic inertia coefficient; Where k represents the dynamic inertia coefficient, k0 represents the preset inertia coefficient value, and k ω1 and k ω2 represents the inertia adjustment coefficient, represents the rate of change of angular velocity, Δω represents the amount of change of angular velocity, T ω Indicates the preset threshold.

3. The control method of the photovoltaic hybrid energy storage system according to claim 2, characterized in that: The process of determining the preset inertia coefficient value includes: Obtaining a value of the damping ratio of the energy storage battery unit; according to Determining the preset inertia coefficient value; Where ξ represents the value of the damping ratio, D represents the virtual damping coefficient, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, and X f represents the equivalent reactance of the AC line, ω G represents the synchronous angular velocity of the virtual synchronous generator, k0 represents the preset inertia coefficient value, W bat It represents the energy stored in the energy storage battery unit, E represents the three-phase reference voltage amplitude of the excitation output of the virtual synchronous generator, and U represents the actual value of the grid side voltage.

4. The control method of the photovoltaic hybrid energy storage system according to any one of claims 1 to 3, characterized in that: Based on the frequency change and the dynamic inertia coefficient, determining the expected battery power change of the energy storage battery unit includes: Determining an angular velocity change according to the frequency change; according to Determining the expected battery power change; Among them, ΔP bat represents the expected battery power change, k represents the dynamic inertia coefficient, W bat represents the energy stored in the energy storage battery unit, ω G represents the synchronous angular velocity of the virtual synchronous generator, and Δω represents the change in angular velocity.

5. The control method of the photovoltaic hybrid energy storage system according to any one of claims 1 to 3, characterized in that: Determining an expected capacitance power change of the supercapacitor unit based on the frequency change rate includes: according to Determining an expected capacitance power change of the supercapacitor unit; Among them, ΔP sc represents the expected capacitance power change, J represents the virtual moment of inertia, ω0 represents the rated electrical angular velocity of the virtual synchronous generator, Indicates the rate of change of angular velocity The transient change value of .

6. The control method of the photovoltaic hybrid energy storage system according to any one of claims 1 to 3, characterized in that: Controlling the operation of the supercapacitor unit according to the expected capacitance power change includes: Determining a voltage deviation value on a DC side of the photovoltaic hybrid energy storage system according to the expected capacitance power change; Obtaining a DC bus voltage on the DC side of the photovoltaic hybrid energy storage system, and performing proportional-integral control based on the DC bus voltage and the voltage deviation value to obtain a desired output current of the supercapacitor unit; The actual output current of the supercapacitor unit is obtained, and proportional-integral control is performed based on the expected output current and the actual output current to obtain a capacitance control signal; the capacitance control signal is used to control the supercapacitor unit to operate according to the expected capacitance power change.

7. The control method of the photovoltaic hybrid energy storage system according to claim 6, characterized in that: Determining the voltage deviation value of the DC side of the photovoltaic hybrid energy storage system according to the expected capacitance power change includes: according to Determine the voltage deviation value on the DC side of the photovoltaic hybrid energy storage system; Wherein, Δu represents the voltage deviation value, ΔP sc represents the expected capacitance power change, U dc represents the DC bus voltage, c represents the capacitance value of the supercapacitor unit, Indicates the rate of change of angular velocity Δω represents the transient change value of angular velocity.

8. The control method of the photovoltaic hybrid energy storage system according to any one of claims 1 to 3, characterized in that: Controlling the operation of the energy storage battery unit according to the expected battery power change includes: Acquire the voltage of the energy storage battery cell, and determine the expected current of the energy storage battery cell according to the expected battery power change and the voltage of the energy storage battery cell; The actual current of the energy storage battery unit is obtained, and proportional integral control is performed based on the actual current and the expected current to obtain a battery control signal; the battery control signal is used to control the energy storage battery unit to operate according to the expected battery power change.

9. A control device for a photovoltaic hybrid energy storage system, characterized in that: Applied to a photovoltaic hybrid energy storage system, the photovoltaic hybrid energy storage system includes an energy storage battery unit and a supercapacitor unit; the device includes: An acquisition module, used to respectively acquire a frequency change amount and a frequency change rate on an AC side of a photovoltaic hybrid energy storage system; A battery control module, configured to determine an expected battery power change of an energy storage battery unit based on the frequency change and the dynamic inertia coefficient, and control the operation of the energy storage battery unit according to the expected battery power change, so that the energy storage battery unit can absorb the low-frequency power change caused by the frequency change; the value of the dynamic inertia coefficient is determined by the frequency change rate and the frequency change; The capacitance control module is used to determine the expected capacitance power change of the supercapacitor unit based on the frequency change rate, and control the operation of the supercapacitor unit according to the expected capacitance power change, so that the supercapacitor unit can absorb the high-frequency power change caused by the frequency change rate.

10. The control device of the photovoltaic hybrid energy storage system according to claim 9, characterized in that: The battery control module is specifically used for: Determine the angular velocity change rate according to the frequency change rate, and determine the angular velocity change amount according to the frequency change amount; according to Determining the value of the dynamic inertia coefficient; Where k represents the dynamic inertia coefficient, k0 represents the preset inertia coefficient value, and k ω1 and k ω2 represents the inertia adjustment coefficient, represents the rate of change of angular velocity, Δω represents the amount of change of angular velocity, T ω Indicates the preset threshold.

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