Phase modifier and wind generating set cooperative control method and system based on active support technology

Abstract

The invention provides a phase modifier and wind generating set cooperative control method and system based on an active support technology, and relates to the field of power system control. According to the invention, a cooperative control method is adopted, so that the fan set can utilize the virtual inertia of the rotor and the virtual inertia of the direct-current capacitor at the same time in a full-wind-speed state, and is combined with the synchronous phase modifier at the grid-connected point. When the system breaks down, inertia support can be provided for the system, active power can be output, reactive power can also be output, and the power grid voltage can be stabilized, so that the new energy grid-connected stability is further enhanced, the new energy grid-connected system can better face various sudden accidents, and new energy grid-off accidents are restrained.

Description

Technical Field

[0001] The present invention relates to the field of power system control, and in particular to a method and system for coordinated control of a phase regulator and a wind turbine generator set based on active support technology. Background Art

[0002] In recent years, the development of new power systems with new energy as the main body has become a research direction for various countries. However, when wind turbines are connected to the large power grid through power electronic converters, there is a lack of coupling between the generator speed and the system frequency, which leads to a significant reduction in the total inertia of the system after large-scale wind power is connected to the grid, thus seriously affecting the frequency stability of the system.

[0003] To solve this problem, active support technology for wind turbines to the power system has emerged. Active support technology mainly focuses on three aspects: virtual inertia control, power limit control, and adding energy storage equipment. Among them, virtual inertia control uses the kinetic energy stored in the rotor of the wind turbine to support the grid frequency by drawing on the rotor inertia support capability of the synchronous generator. However, there are problems such as secondary frequency drop in rotor virtual inertia control. In addition, when a system failure occurs, the voltage at the wind farm grid connection point will drop instantly, which will cause shocks to equipment such as generators and transformers, which may cause equipment failure or damage in the long term. Therefore, it is necessary to configure reactive power compensation equipment at the new energy station.

[0004] Therefore, there is still room for improvement in current technology. Summary of the invention

[0005] Purpose of the invention: A phase regulator and wind turbine coordinated control method based on active support technology is proposed, and a system capable of executing the control method is further proposed, which is intended to provide active inertia support to the grid in a timely manner and suppress frequency fluctuations when the grid frequency fluctuates. In addition, in the case of unstable grid voltage when a fault occurs, the grid voltage can be supported to improve the stability of the system.

[0006] In a first aspect of the present invention, a method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology is proposed, and the steps are as follows:

[0007] Combine the rotor virtual inertia control of the direct-drive permanent magnet synchronous wind turbine generator and the DC bus capacitor virtual inertia control to control the change in active power output by the direct-drive permanent magnet synchronous wind turbine generator set when participating in grid frequency support;

[0008] Synchronous phase condensers are installed at the high-voltage grid connection point. When a fault occurs in the power grid system, the synchronous phase condensers provide inertia support to the power grid system and output reactive power to stabilize the voltage of the power grid system.

[0009] In a further embodiment of the first aspect, the direct-drive permanent magnet synchronous wind turbine converts kinetic energy into mechanical energy through the blades of the hub. From aerodynamics, it can be known that the output power P wind It is expressed as:

[0010]

[0011] Where ρ is the air density; R is the fan blade radius; V w is the wind speed; C p is the wind energy utilization rate; λ is the tip speed ratio; β is the pitch angle.

[0012] In a further embodiment of the first aspect, the direct-drive permanent magnet synchronous wind turbine generator adopts maximum power point tracking control (MPPT). When the wind speed is a fixed value, the amount of wind energy captured by the wind turbine is only related to the wind energy utilization coefficient C p When the pitch angle β remains unchanged, the wind energy utilization coefficient C p It is only related to the blade tip speed ratio λ. Therefore, by setting the optimal blade tip speed ratio, the wind energy captured by the wind turbine reaches the maximum value P opt .

[0013] In a further embodiment of the first aspect, when the direct-drive permanent magnet synchronous wind turbine generator is running at maximum power, there is a lack of coupling relationship between the generator speed and the system frequency, resulting in a significant reduction in the total inertia of the system after large-scale wind power is connected to the grid. Therefore, rotor virtual inertia control is introduced in the MPPT state. At this time, the electromagnetic power reference value P ref The expression is as follows:

[0014] P ref =P opt +P vir

[0015] Where P opt Indicates the maximum wind energy captured by the wind turbine; P vir Indicates the additional power provided by virtual inertia control.

[0016] In a further embodiment of the first aspect, the rotor virtual inertia control includes an inertia controller and a droop controller, and the active power reference value of the machine-side converter is changed by adding the rotor virtual inertia power. When the frequency changes, the kinetic energy of the rotor is released to achieve flexible changes in active power and improve the stability of the system. At this time, the additional power P provided by the virtual inertia control is vir The expression is as follows:

[0017]

[0018] In the formula, k p is the inertia control coefficient; k d is the droop control coefficient; Δf is the frequency deviation.

[0019] In a further embodiment of the first aspect, based on the characteristic that the rotor of the synchronous generator has a certain inertia and can store mechanical kinetic energy, the DC capacitor can simulate the synchronous generator to provide virtual inertia to the system.

[0020] In order to establish a connection between the storage power of the DC capacitor and the storage power of the synchronous generator, the coupling relationship between frequency and DC voltage is found by establishing an equation. The specific formula is as follows:

[0021]

[0022] In the formula, H dc is the virtual inertia time constant of the DC capacitor; f N is the rated frequency; C dc is the DC capacitance value; S w is the rated capacity of the fan; V dc is a DC voltage.

[0023] The virtual inertia time constant of DC capacitor is H dc The calculation formula is as follows:

[0024]

[0025] DC voltage reference value The calculation formula is as follows:

[0026]

[0027] Where Δf is the frequency deviation; ΔV max is the maximum voltage deviation; f 1 is the frequency of the disturbance; f 0 is the frequency before the disturbance.

[0028] In a further embodiment of the first aspect, if the wind turbine generator set only includes active support for frequency by virtual inertia control of the rotor and DC capacitor, when a large voltage disturbance occurs at the wind farm grid connection point, the wind turbine generator set cannot stabilize the grid voltage in time. Therefore, by combining the synchronous phase regulator with the virtual inertia control for coordinated control, both active power and reactive power can be output to the grid system, thereby reducing the amplitude of grid voltage fluctuation.

[0029] In a further embodiment of the first aspect, the self-parallel excited static excitation system adopted by the synchronous phase regulator generally includes a slow reactive loop and a fast voltage loop to realize rapid regulation of the terminal voltage of the machine. The fast voltage loop realizes the stability of the terminal voltage by adjusting the excitation voltage, and the slow reactive loop adjusts the stator voltage in time according to the instructions of the excitation system.

[0030] A second aspect of the present invention provides a coordinated control system, which includes at least one execution unit, a memory connected to the execution unit for communication, and a synchronous phase regulator installed at a high-voltage grid connection point.

[0031] The execution unit combines the rotor virtual inertia control of the direct-drive permanent magnet synchronous wind turbine generator and the DC bus capacitor virtual inertia control to control the change in active power output by the direct-drive permanent magnet synchronous wind turbine generator set when participating in the grid frequency support;

[0032] When a fault occurs in the power grid system, the synchronous condenser provides inertia support to the power grid system and outputs reactive power to stabilize the voltage of the power grid system;

[0033] The memory stores instructions that can be executed by the execution unit, and the instructions are used to be executed by the execution unit to implement the phase regulator and wind turbine generator set coordinated control method based on active support technology disclosed in the first aspect.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The present invention utilizes the coordinated control of rotor and DC capacitor virtual inertia to more effectively provide active inertia support to the power grid and suppress frequency fluctuations. Synchronous condensers have good application prospects in wind power systems. Therefore, when used together with virtual inertia control, they can improve the frequency response level of wind turbines and stabilize the grid-side voltage, making wind farms more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a block diagram of rotor virtual inertia control of the present invention.

[0037] Figure 2 It is a block diagram of the DC capacitor virtual inertia control of the present invention.

[0038] Figure 3 This is the synchronous phase condenser excitation system control model of the present invention.

[0039] Figure 4 It is the frequency change diagram after disturbance of the present invention.

[0040] Figure 5 This is a diagram of the rotor speed change after disturbance according to the present invention.

[0041] Figure 6 This is a diagram of the DC voltage change after disturbance of the present invention.

[0042] Figure 7 It is a diagram of the change of active power output after disturbance of the present invention.

[0043] Figure 8 This is the grid-connected model of the synchronous phase condenser of the present invention.

[0044] Fig. 9 It is the reactive power output diagram of the post-disturbance phase regulator of the present invention.

[0045] Fig.10 This is a diagram of the grid voltage change after the disturbance of the present invention. DETAILED DESCRIPTION

[0046] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features known in the art are not described.

[0047] When the currently widely used direct-drive permanent magnet synchronous wind turbines and doubly-fed asynchronous motors are connected to the large power grid through power electronic converters, there is a lack of coupling relationship between the generator speed and the system frequency. They usually adopt maximum power point tracking control and therefore cannot participate in grid frequency support.

[0048] The fan converts kinetic energy into mechanical energy through the blades of the hub. From aerodynamics, we know that its output power P wind It is expressed as:

[0049]

[0050] Where ρ is the air density; R is the fan blade radius; V w is the wind speed; C p is the wind energy utilization rate; λ is the tip speed ratio; β is the pitch angle.

[0051] like Figure 1 As shown in the figure, the direct-drive permanent magnet synchronous wind turbine adopts maximum power point tracking control (MPPT). When the wind speed is a fixed value, the wind energy captured by the wind turbine is only proportional to the wind energy utilization coefficient C. p When the pitch angle β remains unchanged, C p It is only related to the blade tip speed ratio λ, so by setting the optimal blade tip speed ratio, the wind energy captured by the wind turbine can reach the maximum value.

[0052] P opt It is expressed as:

[0053]

[0054] In the formula, C pmax is the maximum wind energy utilization rate; k max It is the coefficient that makes the wind turbine output power reach the maximum value.

[0055] like Figure 1As shown in the figure, the rotor virtual inertia control includes an inertia controller and a droop controller. The active power reference value of the machine-side converter is changed by adding the rotor virtual inertia power. When the frequency changes, the kinetic energy of the rotor is released to achieve flexible changes in active power and improve the stability of the system. The additional power P provided by the virtual inertia control vir It is expressed as:

[0056]

[0057] In the formula, k p is the inertia control coefficient; k d is the droop control coefficient; Δf is the frequency deviation.

[0058] like Figure 1 As shown in Figure 2, when the virtual inertia control of the rotor is added, the active power reference value of the wind turbine includes the active power reference value P of the MPPT control. ref It is expressed as:

[0059] P ref =P opt +P vir (4)

[0060] like Figure 1 As shown, the q-axis reference current can be obtained and will The additional rotor virtual inertia control on the machine side is introduced, where The expression is:

[0061]

[0062] Where n p is the number of generator pole pairs; ψ f is the generator flux; ω e is the synchronous angular velocity of the generator.

[0063] Specifically, the frequency change rate is introduced into the virtual inertia control of the rotor, so there may be differential measurement noise, which is not conducive to the rapidity and stability of frequency recovery. Secondly, since the rotor needs to absorb power from the system to restore the speed when the frequency is restored, it will cause a secondary drop in frequency. In order to establish a connection between the storage power of the DC capacitor and the storage power of the synchronous generator, the charging and discharging power of the DC capacitor is expressed as:

[0064]

[0065] Specifically, in order to establish a connection between the storage power of the DC capacitor and the storage power of the synchronous generator, the coupling relationship between frequency and DC voltage is found by establishing an equation. The specific formula is as follows:

[0066]

[0067] In the formula, H dc is the virtual inertia time constant of the DC capacitor; f N is the rated frequency; C dc is the DC capacitance value; S w is the rated capacity of the fan; V dc is a DC voltage.

[0068] Integrate both sides of the equation:

[0069]

[0070] like Figure 2 As shown, we can finally get H dc and DC voltage reference The specific formula is:

[0071]

[0072] Where Δf is the frequency deviation; ΔV max is the maximum voltage deviation; f 1 is the frequency of the disturbance, f 0 is the frequency before the disturbance.

[0073] like Figure 2 As shown, by measuring the frequency deviation, the deviation value is substituted into the formula for calculation, and then Add them together and then take the square root to get the DC voltage reference value, and finally bring the DC voltage reference value into the virtual inertia control of the additional DC capacitor of the grid-side converter, so as to realize the inertia support of the system by the DC capacitor voltage.

[0074] like Figure 3 As shown, the self-parallel excited static excitation system used by the synchronous phase condenser usually includes a slow reactive loop and a fast voltage loop to achieve rapid regulation of the terminal voltage.

[0075] The fast voltage loop stabilizes the terminal voltage by adjusting the excitation voltage. When a system fault occurs, the actual terminal voltage value U t The excitation voltage will change, and the voltage inner loop will quickly adjust the excitation voltage, thereby changing the stator current and reactive power of the synchronous phase regulator and stabilizing the grid voltage.

[0076] The slow reactive loop adjusts the stator voltage in time according to the excitation system instructions, thereby achieving closed-loop control of reactive power. The excitation increase or decrease signal of the excitation system controls the reactive power Q ref The value is compared with the actual measured value Q eThe power is compared and then acts on the voltage inner loop after passing through the integrator. When the system is in steady state operation, the reactive outer loop provides reactive reserve for the system; when a system failure occurs, the reactive power reference value becomes zero, and the synchronous condenser provides reactive compensation to the system.

[0077] like Figure 3 As shown, T A and k A are the time constant and amplification factor of the power amplifier link; T z and k z are the time constant and amplification factor of the excitation winding transfer function; T Q and k Q are the time constant and amplification factor of the outer loop reactive power measurement link; T R is the time constant of the inner loop voltage measurement link; U t and U ref They are the machine terminal voltage and the excitation system reference voltage; Q e and Q ref They are reactive power output and reference value respectively.

[0078] Specifically, in order to verify the feasibility of virtual inertia control of the rotor and DC capacitor, the wind speed is maintained at 12m / s in the MPPT state. The initial active load of the system is 0.5MW. In order to disturb the frequency, the active load is increased by 2MW at 2s. The total simulation time of the system is set to 3s.

[0079] like Figure 4 As shown, when there is no virtual inertia control, only the rotor virtual inertia control is used, and the rotor and DC capacitor virtual inertia control are used at the same time, the controlled wind speed remains unchanged, and the frequency drops under the load disturbance 2MW condition, and the lowest points of the system frequency are 49.897, 49.903, and 49.906Hz respectively. It can be seen that compared with no virtual inertia control, the other two controls have improved the lowest value of the frequency, and when the rotor and DC capacitor virtual inertia control are used at the same time, the improvement effect on the lowest value of the system frequency is the best, and the frequency drop time is also the shortest, which can prove the superiority of the control strategy proposed in the present invention in frequency modulation.

[0080] like Figure 5 As shown in the figure, under constant wind speed, the rotor speed is kept at 3.13 rad / s due to MPPT control, and only the rotor virtual inertia control will reduce the rotor speed during the disturbance, releasing a large amount of rotor rotational kinetic energy and increasing active power output. At this time, the rotor speed drops to 3.05 rad / s, but it can be found that there is a secondary drop in the process of speed recovery, just because the rotor absorbs too much power from the system, causing the frequency to drop again, so it needs to be coordinated with the DC capacitor for control.

[0081] like Figure 6 As shown in the figure, under constant wind speed, the DC voltage is kept at 1800V due to the control of the grid-side converter, and only the DC voltage virtual inertia control makes the DC voltage decrease as the frequency decreases during the disturbance. At this time, the DC voltage drops to 1774V, which indicates that the energy stored in the capacitor is recovering at the supporting frequency.

[0082] like Figure 7 As shown, the active power output by the fan when there is no virtual inertia control, only the rotor virtual inertia control, only the DC capacitor virtual inertia control, and when both the rotor and DC capacitor virtual inertia control are used. Before the load disturbance occurs, the power output by the fan remains consistent. Under the load disturbance of 2MW, it can be seen that when the rotor or DC capacitor virtual inertia control is used respectively, the output of active power increases compared to the case without inertia support, increasing to 0.862pu and 0.867pu respectively. When the two controls are used at the same time, the active power increases to 0.878pu, which has better active output than the other three cases, indicating that the control proposed by the present invention has a better effect on stabilizing the system frequency and providing inertial response.

[0083] like Figure 8 As shown, on the basis of the above control strategy, in order to verify the accuracy of the coordinated control of the phase regulator and the wind turbine generator set based on active support technology, the simulation model in the figure is built in Matlab / Simulink.

[0084] like Fig. 9 As shown in the figure, the system has an initial active load of 2MW. When it is running stably for 1.6s, the active load suddenly increases by 10MW. The synchronous phase regulator changes the magnitude and direction of the excitation current, and the reactive power output is the maximum at 1.65s, providing 0.195pu of reactive power compensation to the system, which then gradually decreases and tends to 0.

[0085] like Fig.10 As shown, it is found that when the load suddenly increases, the remote bus voltage drops sharply. When the synchronous condenser is installed, the bus voltage reduction is significantly smaller than the case where the synchronous condenser is not installed, and the bus voltage recovers faster, which effectively improves the stability and reliability of the wind turbine.

[0086] The phase regulator and wind turbine coordinated control method based on active support technology disclosed in the above embodiments can be implemented in whole or in part by software, hardware, firmware or any other combination. When implemented by software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs.

[0087] When the computer instruction or computer program is loaded or executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable devices. The computer instruction can be stored in a computer-readable storage medium, or transmitted from a computer-readable storage medium to another computer-readable storage medium. For example, the computer instruction can be transmitted from a website site, a computer, a server, or a data center to another website site, a computer, a server, or a data center by a wired (e.g., infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server, a data center, etc. that contains one or more available media sets. The available medium can be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state hard disk.

[0088] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to it in form and detail without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

1. A method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology, characterized in that: Combine the rotor virtual inertia control of the direct-drive permanent magnet synchronous wind turbine generator and the DC bus capacitor virtual inertia control to control the change in active power output by the direct-drive permanent magnet synchronous wind turbine generator set when participating in grid frequency support; Synchronous phase condensers are installed at the high-voltage grid connection point. When a fault occurs in the power grid system, the synchronous phase condensers provide inertia support to the power grid system and output reactive power to stabilize the voltage of the power grid system.

2. The method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology according to claim 1 is characterized in that: The synchronous condenser comprises a slow reactive loop and a fast voltage loop to achieve fast regulation of the terminal voltage, wherein the fast voltage loop achieves terminal voltage stability by regulating the excitation voltage, and the slow reactive loop timely regulates the stator voltage according to the excitation system instruction.

3. The method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology according to claim 1 is characterized in that: The output power P of the direct-drive permanent magnet synchronous wind turbine generator is wind It is expressed as: Where ρ is the air density; R is the fan blade radius; V w is the wind speed; C p is the wind energy utilization rate; λ is the tip speed ratio; β is the pitch angle; The direct-drive permanent magnet synchronous wind turbine generator adopts maximum power point tracking control. When the wind speed is a fixed value, the wind energy captured by the wind turbine is proportional to the wind energy utilization coefficient C. p When the pitch angle β remains unchanged, the wind energy utilization coefficient C p It is related to the blade tip speed ratio λ; by setting the optimal blade tip speed ratio, the wind energy captured by the wind turbine reaches the maximum value P opt .

4. The method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology according to claim 3 is characterized in that: When the direct-drive permanent magnet synchronous wind turbine generator is running at maximum power, the rotor virtual inertia control is introduced in the maximum power point tracking control state. At this time, the electromagnetic power reference value P ref The expression is as follows: P ref =P opt +P vir Where P opt Indicates the maximum wind energy captured by the wind turbine; P vir Indicates the additional power provided by virtual inertia control.

5. The method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology according to claim 4 is characterized in that: The rotor virtual inertia control includes an inertia controller and a droop controller. The active power reference value of the machine-side converter is changed by adding the rotor virtual inertia power. When the frequency changes, the kinetic energy of the rotor is released. At this time, the additional power P provided by the virtual inertia control is vir The expression is as follows: In the formula, k p is the inertia control coefficient; k d is the droop control coefficient; Δf is the frequency deviation.

6. The method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology according to claim 1, characterized in that: The rotor of the direct-drive permanent magnet synchronous wind turbine generator has inertia to store mechanical kinetic energy, so that the DC capacitor can imitate the direct-drive permanent magnet synchronous wind turbine generator to provide virtual inertia to the power grid system; The storage power of the DC capacitor is linked to the storage power of the direct-drive permanent magnet synchronous wind turbine generator, and the equation is established to find the coupling relationship between frequency and DC voltage as follows: In the formula, H dc is the virtual inertia time constant of the DC capacitor; f N is the rated frequency; C dc is the DC capacitance value; S w is the rated capacity of the fan; V dc is a DC voltage.

7. The method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology according to claim 6 is characterized in that: The virtual inertia time constant of DC capacitor is H dc The calculation formula is as follows: DC voltage reference value The calculation formula is as follows: Where Δf is the frequency deviation; ΔV max is the maximum voltage deviation; f1 is the frequency during disturbance; f0 is the frequency before disturbance.

8. A collaborative control system, characterized in that: include: At least one execution unit; the execution unit combines the rotor virtual inertia control of the direct-drive permanent magnet synchronous wind turbine generator and the DC bus capacitor virtual inertia control to control the change in active power output by the direct-drive permanent magnet synchronous wind turbine generator set when participating in grid frequency support; Synchronous condensers are installed at high-voltage grid connection points. When a fault occurs in the power grid system, the synchronous condensers provide inertia support to the power grid system and output reactive power to stabilize the voltage of the power grid system. A memory communicatively connected to at least one of the execution units; the memory stores instructions executable by the execution unit, the instructions being used to be executed by the execution unit to implement the method for coordinated control of a phase regulator and a wind turbine generator set based on active support technology as described in any one of claims 1 to 7.

9. A computer-readable storage medium, characterized in that: The storage medium stores at least one executable instruction. When the executable instruction is executed on the electronic device, the electronic device executes the method for coordinated control of the phase regulator and the wind turbine generator set based on active support technology as described in any one of claims 1 to 7.

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