New energy grid-connected system AGC method and device considering power frequency characteristics

Abstract

The invention provides a new energy grid-connected system AGC method and device considering power frequency characteristics, and belongs to the technical field of grid-connected system control. The method comprises the steps of determining an angular frequency change rate dynamic response characteristic of a target device based on a virtual synchronous control equation and an active-frequency droop control equation of the target device in the new energy grid-connected system; wherein the target device comprises a new energy power generation device, a flexible controllable load and an energy storage device; determining a feed-forward compensation value of the target device based on the angular frequency change rate dynamic response characteristic; determining a PI control value of the target device based on the proportionality coefficient and the integral coefficient; wherein the proportionality coefficient is determined based on the AGC characteristic of the target device under the non-rated condition, and the integral coefficient is determined based on the AGC characteristic of the target device under the rated condition; an AGC power value is determined based on the feed-forward compensation value and the PI control value, and AGC is performed on the target device based on the AGC power value. According to the invention, the AGC response speed can be improved, and the dynamic process frequency fluctuation is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-connected system control, and in particular to an AGC method and device for a new energy grid-connected system taking power-frequency characteristics into account. Background Art

[0002] The global installed capacity of renewable energy maintains a rapid growth trend and plays an important role in building a clean and sustainable energy supply system. However, the large-scale access of distributed energy to the grid, its intermittent and volatile nature, leads to a decrease in the inertial support and primary frequency regulation capabilities of the grid, thereby reducing the frequency stability of the grid. As the penetration rate of distributed power sources continues to increase, the stability problem of the grid has become increasingly serious. The active-frequency control loop of the traditional virtual synchronous generator (VSG) technology can only perform primary frequency regulation with differential regulation. When the load or power supply of the new energy grid-connected system fluctuates greatly, the frequency will exceed the limit or even cross the boundary, which is not conducive to the stable operation of the new energy grid-connected system. Automatic Generation Control (AGC) is required to maintain frequency stability.

[0003] AGC can be divided into centralized and decentralized control schemes based on communication, as well as distributed control schemes that do not require communication. The control scheme based on communication relies on communication for control, which has problems such as heavy communication burden and weak scalability. Communication failure may cause system instability or even collapse. When the existing distributed control scheme performs AGC due to load fluctuation at rated frequency, PI control is performed through the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity. Although the PI control output value can reasonably distribute the load according to its own rated capacity, it cannot guarantee the response speed of AGC, and it is difficult to achieve AGC control effect at non-rated frequency. Summary of the invention

[0004] The embodiments of the present invention provide an AGC method and device for a new energy grid-connected system taking into account power-frequency characteristics, so as to solve the problem of slow response speed of a distributed AGC control method.

[0005] In a first aspect, an embodiment of the present invention provides an AGC method for a new energy grid-connected system taking into account power-frequency characteristics, including:

[0006] Based on the virtual synchronization control equation and active power-frequency droop control equation of the target device in the renewable energy grid-connected system, the dynamic response characteristics of the angular frequency change rate of the target device are determined; wherein the target device includes a renewable energy power generation device, a flexible controllable load and an energy storage device;

[0007] determining a feedforward compensation value of the target device based on a dynamic response characteristic of an angular frequency change rate;

[0008] Determine a PI control value of the target device based on a proportional coefficient and an integral coefficient; wherein the proportional coefficient is determined based on an AGC characteristic of the target device under non-rated conditions, and the integral coefficient is determined based on an AGC characteristic of the target device under rated conditions;

[0009] An AGC power value is determined based on the feedforward compensation value and the PI control value, and AGC is performed on the target device based on the AGC power value.

[0010] In one possible implementation, the virtual synchronous control equations include rotor motion equations;

[0011] Based on the virtual synchronization control equation and active power-frequency droop control equation of the target device in the renewable energy grid-connected system, the dynamic response characteristics of the angular frequency change rate of the target device are determined, including:

[0012] Solve the differential equations for the rotor motion equation and the active power-frequency droop control equation to obtain the active power-frequency dynamic response characteristics of the target device;

[0013] The active power-frequency dynamic response characteristic is differentiated to obtain the angular frequency change rate dynamic response characteristic of the target device.

[0014] In one possible implementation, the rotor motion equation is:

[0015]

[0016] Where J is the virtual moment of inertia, Δω is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity, t is the time, P m is the virtual mechanical power of the generator, ω0 is the reference angular velocity, P e is the virtual electromagnetic power of the generator, D is the virtual damping coefficient;

[0017] The active power-frequency droop control equation is:

[0018] P ref -P=K ω (ω-ω0)

[0019] Among them, P ref is the reference active power, P is the real-time output power of the inverter, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, ω is the actual angular velocity of the synchronous generator rotor, and ω0 is the reference angular velocity;

[0020] The active power-frequency dynamic response characteristics are:

[0021]

[0022] Wherein, Δω is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity, δω is the change in the actual angular velocity of the synchronous generator rotor, ω1 is the actual angular velocity of the synchronous generator rotor in the previous state, ω2 is the actual angular velocity of the synchronous generator rotor in the next state, and P′ e is the output active power in the previous state, P e is the output active power in the latter state, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant;

[0023] The dynamic response characteristics of the angular frequency change rate are:

[0024]

[0025] Among them, ω is the actual angular velocity of the synchronous generator rotor, ΔP is the change in output active power, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant.

[0026] In one possible implementation, the feedforward compensation value is:

[0027]

[0028] Among them, P 21 is the feedforward compensation value, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and ω is the actual angular velocity of the synchronous generator rotor.

[0029] In one possible implementation, the scaling factor is:

[0030] K P2 =0.5K ω

[0031] Among them, K P2 is the proportionality coefficient, K ω It is the primary frequency modulation coefficient of the virtual synchronous machine.

[0032] In one possible implementation, the integration coefficient is:

[0033]

[0034] Among them, K i2 is the integral coefficient, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, H is the inertia time constant, J is the virtual moment of inertia, t is the time, and e is the natural constant.

[0035] In a possible implementation, the new energy grid-connected system includes multiple target devices, the droop coefficient setting value of each target device is proportional to the inverse of the capacity, the ratio of the virtual inertia to the virtual damping is equal, and the virtual inertia is proportional to its rated power.

[0036] In a possible implementation manner, after the AGC power value is determined based on the feedforward compensation value and the PI control value, the method further includes:

[0037] Based on the real-time output voltage and real-time output current of the inverter, the output power and voltage angular velocity of the inverter are calculated;

[0038] Through the stator motion equation and the rotor motion equation, the output power and voltage angular velocity are synthesized into the inverter output reference voltage, and the voltage and current dual closed-loop control of the inverter of the target device is performed based on the AGC power value and the inverter output reference voltage.

[0039] In a second aspect, an embodiment of the present invention provides an AGC device for a new energy grid-connected system taking into account power-frequency characteristics, including:

[0040] A characteristic determination module, for determining the dynamic response characteristics of the angular frequency change rate of the target device based on the virtual synchronization control equation and the active power-frequency droop control equation of the target device in the new energy grid-connected system; wherein the target device includes a new energy power generation device, a flexible controllable load and an energy storage device;

[0041] A feedforward compensation module, used to determine a feedforward compensation value of a target device based on a dynamic response characteristic of an angular frequency change rate;

[0042] A PI control module, used to determine a PI control value of a target device based on a proportional coefficient and an integral coefficient; wherein the proportional coefficient is determined based on an AGC characteristic of the target device under non-rated conditions, and the integral coefficient is determined based on an AGC characteristic of the target device under rated conditions;

[0043] The AGC control module is used to determine an AGC power value based on a feedforward compensation value and a PI control value, and perform AGC on a target device based on the AGC power value.

[0044] The embodiments of the present invention provide an AGC method and device for a new energy grid-connected system taking into account power-frequency characteristics, and realize AGC through the dynamic response characteristics of the angular frequency change rate of the grid-connected device. On the basis of realizing that multiple devices evenly bear the load active power according to their own capacity ratio, actively eliminating the frequency deviation of the new energy grid-connected system, and maintaining the frequency stability of the new energy grid-connected system, AGC is performed through feedforward compensation combined with PI control to improve the AGC response speed, reduce the frequency fluctuation of the dynamic process, and can be applied to frequency regulation at non-rated frequency, with a wider range of applicable scenarios. 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 This is an application scenario diagram of the AGC method for a new energy grid-connected system taking into account power-frequency characteristics provided by an embodiment of the present invention;

[0047] Figure 2 is a flow chart of an implementation method of an AGC method for a new energy grid-connected system taking into account power-frequency characteristics provided by an embodiment of the present invention;

[0048] Figure 3 It is a functional block diagram of an AGC method for a new energy grid-connected system taking into account power-frequency characteristics provided by an embodiment of the present invention;

[0049] Figure 4 It is a structural schematic diagram of an AGC device of a new energy grid-connected system taking into account power-frequency characteristics provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] 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.

[0051] 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.

[0052] Figure 1 This is an application scenario diagram of the AGC method for a new energy grid-connected system taking into account power-frequency characteristics provided by an embodiment of the present invention. Figure 1 As shown in the figure, the new energy grid-connected system includes three types of devices: "source, load and storage". The new energy power generation representing the "source" and the flexible controllable load representing the "load" exist in the form of distributed photovoltaic storage system and electric vehicle charging pile respectively, and the "storage" exists in the form of energy storage device. DC system, inverter module, filter module, sampling module, virtual synchronous control module, AGC module, voltage and current dual closed-loop control module, PWM drive module.

[0053] The DC systems of the three types of "source, load and storage" devices have different structures. The DC system of the distributed photovoltaic storage system consists of a photovoltaic array and an energy storage device and the corresponding Boost booster and buck-boost device, the DC system of the energy storage device consists of an energy storage system and the corresponding buck-boost device, and the DC system of the electric vehicle charging pile consists of a power battery and the corresponding buck-boost device, while the AC side circuits and control methods of the three types of devices are the same. The output end of the DC system is connected to the input end of the inverter module, the output end of the inverter module is connected to the input end of the filter module, and the output end of the filter is connected to the input end of the sampling module, so as to sample the output parameters of the inverter and use them as the input parameters of the control loop.

[0054] Figure 2 The implementation flow chart of the AGC method for the new energy grid-connected system taking into account the power-frequency characteristics provided by the embodiment of the present invention is described in detail as follows:

[0055] Step 201, based on the virtual synchronization control equation and active-frequency droop control equation of the target device in the renewable energy grid-connected system, determine the dynamic response characteristics of the angular frequency change rate of the target device; wherein the target device includes a renewable energy power generation device, a flexible controllable load and an energy storage device.

[0056] In this embodiment, the applied new energy grid-connected system includes three types of devices: "source, load and storage", where the new energy power generation representing the "source" and the flexible controllable load representing the "load" exist in the form of distributed photovoltaic storage system and electric vehicle charging pile respectively, and the "storage" exists in the form of energy storage device. This embodiment performs AGC on each device in the new energy grid-connected system to realize distributed AGC without communication.

[0057] like Figure 3 As shown, an AGC module is added in front of the virtual synchronous control module of the target device. When AGC is performed, the AGC power value is determined by feedforward compensation combined with PI control, the inverter output reference voltage signal is formed by the virtual synchronous control module, and the per-unit reference voltage signal is formed by the voltage and current dual closed-loop control module, which is then driven by the PWM drive module to operate.

[0058] The sampling module input is connected to the virtual synchronization control module input and the AGC module input, the AGC module output is connected to the virtual synchronization control module input, the virtual synchronization control module input is connected to the voltage and current dual closed-loop control module input, the voltage and current dual closed-loop control module output is connected to the PWM drive module input, and the PWM drive module output is connected to the inverter module input.

[0059] The sampling module includes a voltage sampling module and a current sampling module. The voltage sampling module and the current sampling module are respectively connected to the output end of the inverter module to collect the output voltage and output current of the inverter in real time and send them to the virtual synchronous control module and the AGC module.

[0060] There is a corresponding relationship between the active power and frequency of the devices in the renewable energy grid-connected system. When the active load of the renewable energy grid-connected system changes, its frequency will also change, thus affecting the AGC. Therefore, the power-frequency characteristics of the target device can be specifically analyzed to determine the dynamic response characteristics of the angular frequency change rate, which can be used to optimize the AGC process.

[0061] Step 202: determining a feedforward compensation value of the target device based on the dynamic response characteristic of the angular frequency change rate.

[0062] In this embodiment, after analysis, the angular frequency change rate of the device in the new energy grid-connected system conforms to the exponential function characteristics and increases suddenly at the initial response moment of the AGC. It can be made to perform feedforward compensation and PI control in conjunction with AGC to improve the response speed of the AGC.

[0063] Step 203 , determining a PI control value of the target device based on a proportional coefficient and an integral coefficient; wherein the proportional coefficient is determined based on an AGC characteristic of the target device under non-rated conditions, and the integral coefficient is determined based on an AGC characteristic of the target device under rated conditions.

[0064] In this embodiment, the PI control output value P 22 It is: P22=Kp2*Δω+Ki2*Δω / s

[0065] The proportional coefficient in PI control determines the controller's immediate response strength to the error, and the integral coefficient gradually adjusts the controller output by accumulating past errors until the steady-state error is eliminated. When AGC is performed under non-rated conditions, the AGC power at the initial moment is only related to the proportional coefficient, so the proportional coefficient can be determined based on the AGC characteristics under non-rated conditions. Under rated conditions, the AGC power is only determined by the integral value of the PI control, so the integral coefficient can be determined based on the AGC characteristics under rated conditions.

[0066] Step 204: determine an AGC power value based on the feedforward compensation value and the PI control value, and perform AGC on the target device based on the AGC power value.

[0067] In this embodiment, the AGC power value output by the AGC module is determined by feedforward compensation combined with PI control, and the AGC power value P2 is the feedforward compensation value P 21 And PI control output value P 22 The sum of P2 = P 21 +P 22 .

[0068] The embodiment of the present invention realizes AGC through the dynamic response characteristics of the angular frequency change rate of the grid-connected device. On the basis of realizing that multiple devices evenly bear the load active power according to their own capacity ratio, actively eliminating the frequency deviation of the renewable energy grid-connected system, and maintaining the frequency stability of the renewable energy grid-connected system, AGC is performed through feedforward compensation combined with PI control to improve the AGC response speed, reduce the frequency fluctuation of the dynamic process, and can be applied to frequency regulation at non-rated frequency, with a wider range of applicable scenarios.

[0069] In one possible implementation, the virtual synchronous control equations include rotor motion equations;

[0070] Based on the virtual synchronization control equation and active power-frequency droop control equation of the target device in the renewable energy grid-connected system, the dynamic response characteristics of the angular frequency change rate of the target device are determined, including:

[0071] Solve the differential equations for the rotor motion equation and the active power-frequency droop control equation to obtain the active power-frequency dynamic response characteristics of the target device;

[0072] The active power-frequency dynamic response characteristic is differentiated to obtain the angular frequency change rate dynamic response characteristic of the target device.

[0073] In this embodiment, under normal circumstances, the relationship between active power P and torque T is P=Tω, where ω is the angular velocity Therefore, the active power can be substituted into the rotor motion equation. Then the output active power in droop control is substituted into the electromagnetic torque T e As a function of frequency deviation, the relationship between frequency and electromagnetic torque T can be obtained: e By rearranging this expression, we can get a first-order nonlinear differential equation about the frequency ff.

[0074] By using the conversion relationship between frequency and angular frequency to solve the above equation, the dynamic response characteristics of the angular frequency change rate can be obtained.

[0075] In one possible implementation, the rotor motion equation is:

[0076]

[0077] Where J is the virtual moment of inertia, Δω is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity, t is the time, P m is the virtual mechanical power of the generator, ω0 is the reference angular velocity, P e is the virtual electromagnetic power of the generator, D is the virtual damping coefficient;

[0078] The active power-frequency droop control equation is:

[0079] P ref -P=K ω (ω-ω0)

[0080] Among them, P ref is the reference active power, P is the real-time output power of the inverter, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, ω is the actual angular velocity of the synchronous generator rotor, and ω0 is the reference angular velocity;

[0081] The active power-frequency dynamic response characteristics are:

[0082]

[0083] Among them, δω is the change of the actual angular velocity of the synchronous generator rotor, ω1 is the actual angular velocity of the synchronous generator rotor in the previous state, ω2 is the actual angular velocity of the synchronous generator rotor in the next state, and P′ e is the output active power in the previous state, P e is the output active power in the latter state, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant;

[0084] The dynamic response characteristics of the angular frequency change rate are:

[0085]

[0086] Among them, ω is the actual angular velocity of the synchronous generator rotor, ΔP is the change in output active power, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant.

[0087] In this embodiment, the virtual synchronous control aims to make the inverter behave like a traditional synchronous generator by introducing the moment of inertia J and the damping coefficient D, so that the inverter can respond to frequency changes, provide inertial support, and help stabilize the power grid.

[0088] Droop control is a control strategy for distributed generation units. It sets a droop characteristic curve of active power-frequency or reactive power-voltage so that each generation unit automatically adjusts the frequency or voltage according to its own power output.

[0089] Combining these two control methods can achieve more flexible and reliable power supply in renewable energy grid-connected systems.

[0090] The stator motion equation of the virtual synchronous control module is E=U+I(R a +jX a ), the rotor motion equation is

[0091] Δω=ω-ω0 is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity; P m is the virtual mechanical power of the generator; P e is the virtual electromagnetic power of the generator; J is the virtual moment of inertia; D is the virtual damping coefficient; E is the generator excitation terminal voltage; U is the generator armature terminal voltage; I is the generator armature current; R a is the stator armature resistance of the synchronous generator; θ is the output phase angle of the virtual synchronous generator; X a is the stator synchronous reactance.

[0092] Active power-frequency droop control of virtual synchronous machine control satisfies: P ref -P=K ω (ω-ω0), K ω It is the primary frequency modulation coefficient of the virtual synchronous machine.

[0093] In one possible implementation, the feedforward compensation value is:

[0094]

[0095] Among them, P 21 is the feedforward compensation value, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and ω is the actual angular velocity of the synchronous generator rotor.

[0096] In this embodiment, the feedforward compensation value is determined according to the angular frequency change rate of the active power-frequency characteristic of the new energy grid-connected system. The angular frequency change rate dynamic response characteristic is transformed to obtain:

[0097] At any time during the AGC process, the following conditions are met:

[0098]

[0099] The AGC power value can be determined by the angular frequency change rate, so that the feedforward compensation value

[0100] In one possible implementation, the scaling factor is:

[0101] K P2 =0.5K ω

[0102] Among them, K P2 is the proportionality coefficient, K ω It is the primary frequency modulation coefficient of the virtual synchronous machine.

[0103] In this embodiment, the input value of the PI control is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity Δω=ω-ω0, and the output value of the PI control P 22 It includes two parts: proportional control term and integral control term, and the relationship is: P22 = K p2 *Δω+K i2 *∫Δωdt,K p2 is the PI control proportional coefficient, K i2 is the PI control integral coefficient, and ∫Δωdt is the integral value of Δω.

[0104] When AGC is performed under non-rated conditions, the feedforward compensation value of the AGC power output value at the initial moment is the same as the proportional control output value of the PI control, and the integral control output value of the PI control is 0. The AGC power value P2 should be the product of the primary frequency modulation coefficient and the difference Δω between the rated angular frequency and the actual angular frequency, that is:

[0105] P2=AP=KωΔω

[0106] Since the AGC power output value at the initial moment of the AGC is the integral control output value K of the PI control i2 *∫Δωdt=0, then the feedforward compensation value and the proportional control output value of the PI control satisfy:

[0107] K P2 *Δω=AP′

[0108]

[0109] Therefore, the AGC power output value is:

[0110] P2=P 21 +P 22 =AP=K ωΔω =AP'+K P2 *Δω=2K P2 *Δω;

[0111] Then the proportional coefficient of the PI output value is:

[0112] K P2 =0.5K ω .

[0113] In one possible implementation, the integration coefficient is:

[0114]

[0115] Among them, K i2 is the integral coefficient, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, H is the inertia time constant, J is the virtual moment of inertia, t is the time, and e is the natural constant.

[0116] In this embodiment, after the AGC is completed, the new energy grid-connected system is at the rated frequency. At this time, the new energy grid-connected system satisfies:

[0117] Δω=0

[0118] dω / dt=0

[0119] Then the ACG output power value satisfies:

[0120]

[0121] K P2 *Δω=0

[0122] That is, the feedforward compensation value of the AGC power output value and the proportional control output value of the PI control are zero, the AGC output power value is only determined by the integral value of the PI control, and the feedforward compensation value of the AGC power output value and the proportional control output value of the PI control are zero, which can be obtained:

[0123] P2=P 21 +P 22 =K i2 *∫Δωdt

[0124] PI control integral coefficient K i2 From the AGC characteristics of the new energy grid-connected system:

[0125]

[0126] Where H = Jω n 2 / (2S n ) is the inertia time constant, S n is the rated capacity of the virtual synchronous generator.

[0127] Solving the equation can get the PI control integral coefficient:

[0128]

[0129] Then the AGC power value

[0130] In a possible implementation, the new energy grid-connected system includes multiple target devices, the droop coefficient setting value of each target device is proportional to the inverse of the capacity, the ratio of the virtual inertia to the virtual damping is equal, and the virtual inertia is proportional to its rated power.

[0131] In this embodiment, the droop coefficient setting value of the n devices in the new energy grid-connected system is proportional to the inverse of the capacity, that is, it satisfies:

[0132] kω1 P e1 =k ω2 P e2 =…=k ωn P en

[0133] The ratio of virtual inertia to virtual damping is equal, that is, it satisfies:

[0134]

[0135] The virtual inertia is proportional to its rated power, that is, it satisfies:

[0136]

[0137] Through this setting, each device can evenly bear the load active power according to its own capacity ratio.

[0138] In a possible implementation manner, after the AGC power value is determined based on the feedforward compensation value and the PI control value, the method further includes:

[0139] Based on the real-time output voltage and real-time output current of the inverter, the output power and voltage angular velocity of the inverter are calculated;

[0140] Through the stator motion equation and the rotor motion equation, the output power and voltage angular velocity are synthesized into the inverter output reference voltage, and the voltage and current dual closed-loop control of the inverter of the target device is performed based on the AGC power value and the inverter output reference voltage.

[0141] In this embodiment, the control logic of the virtual synchronous control module is: sampling the output voltage Uok and output current Iok of the inverter module, calculating the current inverter output power P and voltage angular velocity ω, and using the classical second-order model of the synchronous generator, that is, the stator equation and the rotor motion equation, to synthesize the inverter output reference voltage.

[0142] In this embodiment, AGC is added before the virtual synchronous control, and the two together control the inverter of the target device.

[0143] 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.

[0144] 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.

[0145] Figure 4The structural diagram of the AGC device of the new energy grid-connected system taking into account the power-frequency characteristics 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:

[0146] like Figure 4 As shown, the AGC device 4 of the new energy grid-connected system taking into account the power-frequency characteristics includes:

[0147] The characteristic determination module 41 is used to determine the dynamic response characteristic of the angular frequency change rate of the target device based on the virtual synchronization control equation and the active power-frequency droop control equation of the target device in the new energy grid-connected system; wherein the target device includes a new energy power generation device, a flexible controllable load and an energy storage device;

[0148] A feedforward compensation module 42, configured to determine a feedforward compensation value of a target device based on a dynamic response characteristic of an angular frequency change rate;

[0149] A PI control module 43, configured to determine a PI control value of a target device based on a proportional coefficient and an integral coefficient; wherein the proportional coefficient is determined based on an AGC characteristic of the target device under non-rated conditions, and the integral coefficient is determined based on an AGC characteristic of the target device under rated conditions;

[0150] The AGC control module 44 is used to determine an AGC power value based on the feedforward compensation value and the PI control value, and perform AGC on the target device based on the AGC power value.

[0151] In one possible implementation, the virtual synchronous control equations include rotor motion equations;

[0152] The characteristic determination module 41 is specifically used for:

[0153] Solve the differential equations for the rotor motion equation and the active power-frequency droop control equation to obtain the active power-frequency dynamic response characteristics of the target device;

[0154] The active power-frequency dynamic response characteristic is differentiated to obtain the angular frequency change rate dynamic response characteristic of the target device.

[0155] In one possible implementation, the rotor motion equation is:

[0156]

[0157] Where J is the virtual moment of inertia, Δω is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity, t is the time, P m is the virtual mechanical power of the generator, ω0 is the reference angular velocity, P e is the virtual electromagnetic power of the generator, D is the virtual damping coefficient;

[0158] The active power-frequency droop control equation is:

[0159] P ref -P=K ω (ω-ω0)

[0160] Among them, P ref is the reference active power, P is the real-time output power of the inverter, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, ω is the actual angular velocity of the synchronous generator rotor, and ω0 is the reference angular velocity;

[0161] The active power-frequency dynamic response characteristics are:

[0162]

[0163] Among them, δω is the change of the actual angular velocity of the synchronous generator rotor, ω1 is the actual angular velocity of the synchronous generator rotor in the previous state, ω2 is the actual angular velocity of the synchronous generator rotor in the next state, and P′ e is the output active power in the previous state, P e is the output active power in the latter state, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant;

[0164] The dynamic response characteristic of the angular frequency change rate is:

[0165]

[0166] Among them, ω is the actual angular velocity of the synchronous generator rotor, ΔP is the change in output active power, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant.

[0167] In one possible implementation, the feedforward compensation value is:

[0168]

[0169] Among them, P 21 is the feedforward compensation value, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and ω is the actual angular velocity of the synchronous generator rotor.

[0170] In one possible implementation, the scaling factor is:

[0171] K P2 =0.5K ω

[0172] Among them, K P2is the proportionality coefficient, K ω It is the primary frequency modulation coefficient of the virtual synchronous machine.

[0173] In one possible implementation, the integration coefficient is:

[0174]

[0175] Among them, K i2 is the integral coefficient, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, H is the inertia time constant, J is the virtual moment of inertia, t is the time, and e is the natural constant.

[0176] In a possible implementation, the new energy grid-connected system includes multiple target devices, the droop coefficient setting value of each target device is proportional to the inverse of the capacity, the ratio of the virtual inertia to the virtual damping is equal, and the virtual inertia is proportional to its rated power.

[0177] In a possible implementation, the AGC control module 44 is further configured to:

[0178] After determining the AGC power value based on the feedforward compensation value and the PI control value, the output power and voltage angular velocity of the inverter are calculated based on the real-time output voltage and the real-time output current of the inverter;

[0179] Through the stator motion equation and the rotor motion equation, the output power and voltage angular velocity are synthesized into the inverter output reference voltage, and the voltage and current dual closed-loop control of the inverter of the target device is performed based on the AGC power value and the inverter output reference voltage.

[0180] The embodiment of the present invention realizes AGC through the dynamic response characteristics of the angular frequency change rate of the grid-connected device. On the basis of realizing that multiple devices evenly bear the load active power according to their own capacity ratio, actively eliminating the frequency deviation of the renewable energy grid-connected system, and maintaining the frequency stability of the renewable energy grid-connected system, AGC is performed through feedforward compensation combined with PI control to improve the AGC response speed, reduce the frequency fluctuation of the dynamic process, and can be applied to frequency regulation at non-rated frequency, with a wider range of applicable scenarios.

[0181] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0182] 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.

[0183] 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 embodiments of the AGC method of the new energy grid-connected system taking into account the power-frequency characteristics. 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.

[0184] 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. An AGC method for a new energy grid-connected system taking into account power-frequency characteristics, characterized in that: include: Based on the virtual synchronization control equation and the active power-frequency droop control equation of the target device in the new energy grid-connected system, the dynamic response characteristics of the angular frequency change rate of the target device are determined; wherein the target device includes a new energy power generation device, a flexible controllable load and an energy storage device; determining a feedforward compensation value of the target device based on the angular frequency change rate dynamic response characteristic; Determine the PI control value of the target device based on a proportional coefficient and an integral coefficient; wherein the proportional coefficient is determined based on the AGC characteristic of the target device under non-rated conditions, and the integral coefficient is determined based on the AGC characteristic of the target device under rated conditions; An AGC power value is determined based on the feedforward compensation value and the PI control value, and AGC is performed on the target device based on the AGC power value.

2. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 1, characterized in that: The virtual synchronous control equations include rotor motion equations; The virtual synchronization control equation and the active power-frequency droop control equation of the target device in the new energy grid-connected system are used to determine the dynamic response characteristics of the angular frequency change rate of the target device, including: Solving the rotor motion equation and the active power-frequency droop control equation by differential equation to obtain the active power-frequency dynamic response characteristic of the target device; The active power-frequency dynamic response characteristic is differentiated to obtain the angular frequency change rate dynamic response characteristic of the target device.

3. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 2, characterized in that: The rotor motion equation is: Where J is the virtual moment of inertia, Δω is the difference between the actual angular velocity of the synchronous generator rotor and the reference angular velocity, t is the time, P m is the virtual mechanical power of the generator, ω0 is the reference angular velocity, P e is the virtual electromagnetic power of the generator, D is the virtual damping coefficient; The active power-frequency droop control equation is: P ref -P=K ω (oh-oh0) Among them, P ref is the reference active power, P is the real-time output power of the inverter, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, ω is the actual angular velocity of the synchronous generator rotor, and ω0 is the reference angular velocity; The active power-frequency dynamic response characteristic is: Among them, δω is the change of the actual angular velocity of the synchronous generator rotor, ω1 is the actual angular velocity of the synchronous generator rotor in the previous state, ω2 is the actual angular velocity of the synchronous generator rotor in the next state, and P′ e is the output active power in the previous state, P e is the output active power in the latter state, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant; The dynamic response characteristic of the angular frequency change rate is: Among them, ω is the actual angular velocity of the synchronous generator rotor, ΔP is the change in output active power, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and e is the natural constant.

4. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 1, characterized in that: The feedforward compensation value is: Among them, P 21 is the feedforward compensation value, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, J is the virtual moment of inertia, t is the time, and ω is the actual angular velocity of the synchronous generator rotor.

5. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 1, characterized in that: The proportionality factor is: K P2 =0.5K ω Among them, K P2 is the proportionality coefficient, K ω It is the primary frequency modulation coefficient of the virtual synchronous machine.

6. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 1, characterized in that: The integral coefficient is: Among them, K i2 is the integral coefficient, D is the virtual damping coefficient, K ω is the primary frequency modulation coefficient of the virtual synchronous machine, H is the inertia time constant, J is the virtual moment of inertia, t is the time, and e is the natural constant.

7. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 1, characterized in that: The new energy grid-connected system includes multiple target devices, the droop coefficient setting value of each target device is proportional to the inverse of the capacity, the ratio of the virtual inertia to the virtual damping is equal, and the virtual inertia is proportional to its rated power.

8. The AGC method for a new energy grid-connected system taking into account power-frequency characteristics according to claim 1, characterized in that: After determining the AGC power value based on the feedforward compensation value and the PI control value, the method further includes: Based on the real-time output voltage and real-time output current of the inverter, the output power and voltage angular velocity of the inverter are calculated; The output power and the voltage angular velocity are synthesized into an inverter output reference voltage through the stator motion equation and the rotor motion equation, and the voltage and current dual closed-loop control of the inverter of the target device is performed based on the AGC power value and the inverter output reference voltage.

9. An AGC device for a new energy grid-connected system taking into account power-frequency characteristics, characterized in that: include: A characteristic determination module, for determining the dynamic response characteristic of the angular frequency change rate of the target device based on the virtual synchronization control equation and the active power-frequency droop control equation of the target device in the new energy grid-connected system; wherein the target device includes a new energy power generation device, a flexible controllable load and an energy storage device; A feedforward compensation module, configured to determine a feedforward compensation value of the target device based on the dynamic response characteristic of the angular frequency change rate; A PI control module, configured to determine a PI control value of the target device based on a proportional coefficient and an integral coefficient; wherein the proportional coefficient is determined based on an AGC characteristic of the target device under non-rated conditions, and the integral coefficient is determined based on an AGC characteristic of the target device under rated conditions; The AGC control module is configured to determine an AGC power value based on the feedforward compensation value and the PI control value, and perform AGC on the target device based on the AGC power value.

10. The AGC device for the new energy grid-connected system taking into account the power-frequency characteristics according to claim 9, characterized in that: The virtual synchronous control equations include rotor motion equations; The characteristic determination module is specifically used for: Solving the rotor motion equation and the active power-frequency droop control equation by differential equation to obtain the active power-frequency dynamic response characteristic of the target device; The active power-frequency dynamic response characteristic is differentiated to obtain the angular frequency change rate dynamic response characteristic of the target device.

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