A control method and system for a voltage-source type wind turbine generator set

Abstract

The present invention provides a control method and system for a voltage-source type wind turbine generator set, including: for the grid-side converter, calculating the amplitude of the virtual synchronous generator electromotive force based on the reference value and the measured value of the terminal voltage of the wind power virtual synchronous generator, adjusting the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtaining the electrical angle of the virtual synchronous generator, and connecting to the grid after double closed-loop control and pulse width modulation based on the amplitude of the virtual synchronous generator electromotive force and the electrical angle; for the machine-side converter, adopting an outer-loop DC bus voltage deviation control and an inner-loop current following control. The voltage-source type wind turbine generator set control strategy proposed in the present invention is suitable for a weak grid environment and plays a role in supporting the grid; by combining the wind power trend, the frequency change situation and dynamically adjusting the moment of inertia, it effectively suppresses the degree of frequency fluctuation, reduces the impact on the wind power itself, and at the same time ensures the safe operation of a high-proportion wind power power system.

Description

Technical Field

[0001] The present invention belongs to the field of new energy access and control Background Art

[0002] With the large-scale connection of wind power to the power grid, the speed-frequency decoupling characteristic of wind turbines causes them to lose the rapid response to the system frequency. Coupled with the decreasing proportion of traditional synchronous generator sets, the equivalent inertia of the power system is further reduced. Looking ahead to the development trend of energy transformation, renewable energy represented by wind power will become one of the main power sources of the system, and the scenario of 100% wind power penetration is more promising. Therefore, wind power should enhance its active support ability to improve the operation stability of the power system. As one of the key technologies to improve the access characteristics of wind power / photovoltaic, the virtual synchronous generator technology has received extensive attention in the academic community. The literature "Cheng Chong et al. Rotor Inertia Adaptive Control Method for Virtual Synchronous Generators [J], Automation of Electric Power Systems, 2015, 39(19)" proposed a rotor inertia adaptive method, but it focused more on microgrids and only analyzed the virtual synchronous control of inverters. The patents "CN201711203675 An Adaptive Virtual Inertia Control Method for Virtual Synchronous Generators" and "CN201810487249 An Adaptive Control Method for the Rotational Inertia of Virtual Synchronous Generators" also only analyzed the virtual synchronous control method based on inverters and did not involve the wind turbine side converter. The above results all equivalent the DC side to an infinite power source, which does not adapt to the randomness of wind power system power. The randomness and volatility of wind are relatively large. When wind turbines use their own inertia to participate in power grid frequency regulation, they are greatly affected by the input power source, i.e., wind power. When the wind power increases, the wind turbines have the ability to provide stronger support to the power grid. When the wind power decreases, the wind turbines can only provide less support while ensuring not to trip off the grid. After being affected, the wind turbines cannot ensure the stability of their state when connected to the power grid. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a control method and system for a voltage source type wind turbine. By combining the angular velocity, electrical angle and electromotive force of the grid-side synchronous generator, it realizes the rotor inertia adaptive regulation control and the machine-side current following control, solves the problem of large instability affected by wind power when connected to the power grid; in the wind power inertia support, the wind power factor correction is added to improve the active inertia support ability of wind power, which not only ensures the stability of the wind turbine itself, but also improves the grid-connected characteristics of wind power and can adapt to the weak grid environment; and by combining the predicted power trend and frequency change situation, the moment of inertia is dynamically adjusted to effectively suppress the frequency fluctuation degree.

[0004] The solution adopted to achieve the above object is as follows:

[0005] A control method for a voltage source type wind turbine, the improvement lies in that it includes:

[0006] For the grid-side converter: Calculate the amplitude of the virtual synchronous generator electromotive force based on the reference value and the measured value of the terminal voltage of the wind power virtual synchronous generator; Adjust the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtain the electrical angle of the virtual synchronous generator; Based on the amplitude of the virtual synchronous generator electromotive force and the electrical angle, it is incorporated into the power grid after double closed-loop control and pulse width modulation;

[0007] For the machine-side converter: Adopt outer-loop DC bus voltage deviation control and inner-loop current tracking control.

[0008] The first preferred technical solution provided by the present invention is improved in that it includes:

[0009] For the grid-side converter: Calculate the amplitude of the virtual synchronous generator electromotive force based on the reference value and the measured value of the terminal voltage of the wind power virtual synchronous generator; Adjust the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtain the electrical angle of the virtual synchronous generator; Based on the amplitude of the virtual synchronous generator electromotive force and the electrical angle, it is incorporated into the power grid after double closed-loop control and pulse width modulation;

[0010] For the machine-side converter: Adopt outer-loop DC bus voltage deviation control and inner-loop current tracking control.

[0011] The second preferred technical solution provided by the present invention is improved in that the calculation formula of the amplitude of the virtual synchronous generator electromotive force is as follows:

[0012]

[0013] In the formula, E is, k up , k ui are the proportional and integral coefficients of the PI regulator respectively, s is the Laplace operator, U ref is the reference value of the terminal voltage of the virtual synchronous generator, and U is the measured value of the terminal voltage;

[0014] Among them, the calculation formula of the reference value U ref of the terminal voltage of the virtual synchronous generator is as follows:

[0015] U ref =U0 + k q (Q ref -Q)

[0016] In the formula, U0 is the rated value of the terminal voltage of the virtual synchronous generator, k q is the proportional coefficient, Q is the actual value of the reactive power, and Q ref is the reactive power command value;

[0017] Among them, the actual value of the reactive power output by the virtual synchronous generator is calculated as follows:

[0018]

[0019] In the formula, u a 、u b 、u c and i a 、i b 、i c are the three-phase voltages and currents measured by the voltage transformer and current transformer in the virtual synchronous generator respectively.

[0020] The third preferred technical solution provided by the present invention is improved in that the

[0021] rotational inertia of the virtual synchronous generator is adjusted according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then the electrical angle of the virtual synchronous generator is obtained, including:

[0022] Calculate the power ratio coefficient according to the predicted wind power at the next moment and the current maximum available wind power;

[0023] Adjust the current rotational inertia of the virtual synchronous generator according to the power ratio coefficient combined with the angular velocity of the virtual synchronous generator and the angular velocity of the power grid;

[0024] Obtain the electrical angle of the virtual synchronous generator according to the current rotational inertia of the virtual synchronous generator, combined with the angular velocity of the virtual synchronous generator and the angular velocity of the power grid.

[0025] The fourth preferred technical solution provided by the present invention is improved in that the calculation formula of the power ratio coefficient is as follows:

[0026]

[0027] In the formula, k is, C1 and C2 are respectively the minimum and maximum values of the set power ratio coefficient, P max1 is the predicted power at the next moment, and P max0 is the current maximum available power.

[0028] The calculation formula of the rotational inertia of the virtual synchronous generator is as follows:

[0029]

[0030] In the formula, J is, J0 is the initial rotational inertia, which is determined by the inertia time constant set by the unit; m is the frequency change rate coefficient, which is used to correct the amplitude of the frequency change rate; ω D is the angular frequency dead zone; ω is the angular velocity of the virtual synchronous generator; ω0 is the synchronous electrical angular velocity of the power grid; k is the power ratio coefficient, which is determined by the predicted power P at the next momentmax1 is determined by the ratio with the current maximum available power P max0 .

[0031] The calculation formula for the electrical angle of the virtual synchronous generator is as follows:

[0032]

[0033] In the formula, J is the moment of inertia; ω0 is the grid synchronous electrical angular velocity; T m , T e are the mechanical torque and electromagnetic torque respectively; D is the damping coefficient; ω and θ are the angular velocity and electrical angle of the virtual synchronous generator respectively;

[0034] Among them, the electromagnetic torque of the virtual synchronous generator and the mechanical torque of the virtual synchronous generator are as shown in the following formula:

[0035]

[0036] In the formula, P is approximately equal to the active power of the virtual synchronous generator and the electromagnetic power Pe, P ref is the active power reference command; among them, the active power of the virtual synchronous generator and the active power reference command are calculated as follows:

[0037]

[0038] In the formula, ua, ub, uc and ia, ib, ic are the three-phase voltages and currents measured by the voltage transformer and current transformer in the virtual synchronous generator respectively, k p is the active-frequency droop coefficient, and P0 is the initial value of the active power;

[0039] Among them, the calculation formula for the initial value of the active power is as follows:

[0040]

[0041] In the formula, k opt is the optimal control coefficient of the wind turbine, ω w0 is the blade rotational angular velocity, d% is the active power reserve rate, P max0 is the power corresponding to the optimal power curve of the wind turbine, P n is the rated power of the wind turbine.

[0042] The fifth preferred technical solution provided by the present invention is improved in that the machine-side converter adopts an outer-loop DC bus voltage deviation control and an inner-loop current tracking control, and the specific steps are as follows:

[0043] Collect the actual value of the DC bus voltage;

[0044] After the deviation between the actual value and the reference value of the DC bus voltage is adjusted by a PI controller to achieve system decoupling control, the reference value of the active current of the machine-side converter is obtained;

[0045] When the actual active current value of the inner loop is collected and there is a deviation from the reference value of the active current of the machine-side converter, the outer loop will give a signal of varying magnitude to the inner loop;

[0046] After the inner loop receives the signal, it controls the current to achieve current tracking control.

[0047] The statement that when the actual active current value of the inner loop is collected and there is a deviation from the reference value of the active current of the machine-side converter, the outer loop will give a signal of varying magnitude to the inner loop includes:

[0048] After the difference between the reference value of the active current of the machine-side converter and the actual active current of the inner loop passes through a PI controller and is added with a voltage compensation value, the q-axis component of the stator voltage usq is obtained;

[0049] After the deviation between the reference value and the actual value of the reactive current passes through a PI controller and is added with voltage compensation, the d-axis component of the stator voltage usd is obtained;

[0050] The q-axis component of the stator voltage usq and the d-axis component of the stator voltage usd are input into the power grid after space vector pulse width modulation.

[0051] The dq-axis components of the stator voltage are obtained from the following control equations:

[0052]

[0053] In the formula, i sd and i sq are the d-axis and q-axis stator current components respectively; L sq and L sq are the d-axis and q-axis inductance components respectively; R s is the stator resistance of the generator; ω s is the electrical angular velocity of the generator rotor; Ψ f is the magnetic flux of the rotor permanent magnet.

[0054] Based on the same inventive concept, the present invention also provides a voltage source type wind turbine control system, which is improved in that it includes: a grid-side converter control module and a machine-side converter control module;

[0055] The grid-side converter control module is used for controlling the wind power virtual synchronous generator;

[0056] The machine-side converter control module is used for controlling the machine-side converter by using outer-loop DC bus voltage deviation control and inner-loop current tracking control.

[0057] Compared with the closest prior art, the beneficial effects of the present invention are as follows:

[0058] 1. A voltage-source type wind turbine control method and system provided by the present invention. For the grid-side converter: calculate the amplitude of the virtual synchronous generator electromotive force based on the reference value and the measured value of the terminal voltage of the wind power virtual synchronous generator; adjust the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtain the electrical angle of the virtual synchronous generator; based on the amplitude of the virtual synchronous generator electromotive force and the electrical angle, it is incorporated into the power grid after double closed-loop control and pulse width modulation; for the machine-side converter: adopt outer-loop DC bus voltage deviation control and inner-loop current tracking control. The rotor inertia self-adaptive method proposed in the present invention combines the angular velocity, electrical angle and electromotive force of the grid-side synchronous generator to realize rotor inertia self-adaptive regulation control and machine-side current tracking control, and solves the problem of large instability affected by wind power when incorporated into the power grid;

[0059] 2. A voltage-source type wind turbine control method and system proposed. In the wind power inertia support, add wind power factor correction to improve the active inertia support ability of wind power, which not only ensures the stability of the wind turbine itself, but also improves the grid-connected characteristics of wind power and can adapt to weak grid environments;

[0060] 3. A voltage-source type wind turbine control method and system proposed. Combine the predicted power trend and frequency change situation to dynamically adjust the moment of inertia, effectively suppressing the degree of frequency fluctuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 It is a flowchart of a voltage-source type wind turbine control method and system provided by the present invention;

[0062] Figure 2 It is the rotor oscillation angular frequency curve of the synchronous generator;

[0063] Figure 3 It is the grid-side converter control diagram of the wind turbine provided by the present invention;

[0064] Figure 4 It is the machine-side converter control diagram of the wind turbine provided by the present invention;

[0065] Figure 5 It is the overall system diagram provided by the present invention;

[0066] Figure 6 It is the basic structure schematic diagram provided by the present invention;

[0067] Figure 7 It is the detailed structure schematic diagram provided by the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0068] The following further elaborates on the specific embodiments of the present invention in conjunction with the drawings.

[0069] A voltage-source type wind turbine control method and system provided in this embodiment, taking a direct-drive permanent magnet wind turbine as an example, adopts a voltage-source type virtual synchronous rotor inertia adaptive control method. The grid-side converter controls the active and reactive power of the wind turbine, and the machine-side converter controls the bus voltage.

[0070] Example 1:

[0071] The flowchart of a voltage-source type wind turbine control method provided by the present invention is as shown in Figure 1 shown, and the overall system diagram is as shown in Figure 5 shown, including:

[0072] The specific control method is divided into two parts: grid-side converter control and machine-side converter control.

[0073] (1) Grid-side converter control

[0074] ① Virtual synchronous control

[0075] Referring to the two-order model of a traditional synchronous generator, the rotor motion equation is as shown in Equation (1).

[0076]

[0077] In the formula, J is the moment of inertia; ω0 is the grid synchronous electrical angular velocity; T m 、T e are the mechanical torque and electromagnetic torque respectively; D is the damping coefficient; ω and θ are the angular velocity and electrical angle of the virtual synchronous generator respectively.

[0078] The active power P output by the virtual synchronous generator is approximately equal to its electromagnetic power P e , and the relationship between the mechanical torque T m 、electromagnetic torque T e and the active power P output by the virtual synchronous generator, active power reference command P ref can be expressed as Equation (2).

[0079]

[0080] To simulate the speed regulation and voltage regulation processes of a synchronous generator, an equivalent mathematical model of a speed governor and an excitation controller is established: the initial active value P0 is superimposed with the angular frequency deviation as the active reference value P ref ; the reactive power deviation is superimposed with the rated machine terminal voltage U0 as the virtual synchronous generator machine terminal voltage reference value U ref , specifically as shown in Equation (3).

[0081]

[0082] In the formula, k pis the active - frequency droop coefficient, P0 is the initial value of active power, k q is the proportional coefficient, Q is the actual value of reactive power, Q ref is the reactive power command value, U0 is the rated value of the terminal voltage of the virtual synchronous generator, U ref is the reference value of the terminal voltage of the virtual synchronous generator.

[0083] U ref The difference between the reference value of the terminal voltage of the virtual synchronous generator and the measured value U of the terminal voltage is processed by a PI regulator to obtain the amplitude E of the electromotive force of the virtual synchronous generator, as shown in Equation (4), where k up and k ui are the proportional and integral coefficients of the PI regulator respectively, and s is the Laplace operator.

[0084]

[0085] The active power P and reactive power Q output by the virtual synchronous generator can be calculated by Equation (5):

[0086]

[0087] In the formula, u a and u b and u c and i a and i b and i c are the three - phase voltages and currents output by the virtual synchronous generator respectively.

[0088] In the wind power system, since the mechanical power input by the wind power is uncontrollable, in order to ensure that the wind turbine has the ability to maintain a certain time of power increase, that is, to respond to the primary frequency regulation process of the system, the wind power reserves d% of the rated power as standby, which can be specifically expressed as:

[0089]

[0090] In the formula, k opt is the optimal control coefficient of the wind turbine, ω w0 is the blade rotational angular velocity, d% is the active power standby rate, P max0 is the power corresponding to the optimal power curve of the wind turbine, P n is the rated power of the wind turbine.

[0091] ② Adaptive selection of rotor inertia

[0092] When the active power of the system drops to a certain value, the typical rotor angular frequency oscillation curve of a synchronous generator is as shown in the appendix Figure 2 shown.

[0093] Physically, during the time period from t1 to t2, the virtual rotor angular velocity of the virtual synchronous generator is less than the grid angular velocity (ω < ω0) and the deviation gradually increases. The angular velocity change rate dω / dt is less than 0 (dω / dt < 0). A larger moment of inertia is required to limit the increase in angular velocity and dω / dt. During the time period from t2 to t3, the virtual rotor angular velocity of the virtual synchronous generator is still less than the grid angular velocity (ω < ω0), but the deviation gradually decreases. The angular velocity change rate dω / dt > 0. At this time, a smaller moment of inertia is appropriate to enable the virtual rotor speed to quickly recover to the rated value. Similarly, t3 - t4 is the same as t1 - t2, and t4 - t5 is the same as t2 - t3, so they will not be elaborated here.

[0094] However, for a wind power system, due to the uncontrollability of the input mechanical power, the influence of wind power variation needs to be considered. When the predicted power P at the next moment max1 is less than the current maximum available power P max0 (P max1 < P max0 ), that is, the supporting ability of the wind turbine decreases, the rotor inertia should be appropriately reduced to avoid a large drop in the actual rotor speed of the wind turbine; when the predicted power P at the next moment max1 is greater than (or equal to) the current P max0 (P max1 ≥ P max0 ), that is, the supporting ability of the wind turbine increases, the rotor inertia should be appropriately increased to enhance the support for the system inertia.

[0095] According to the above analysis, the rotor inertia values in different situations can be obtained, as shown in Equation (7) specifically.

[0096]

[0097] In the formula, J0 is the initial moment of inertia, which is a constant as a given reference value and is determined by the inertia time constant set by the unit. It is set according to the existing standard (the recommended Tj = 4s - 12s in the Q / GDW 11826 - 2018 standard). According to the formula:

[0098]

[0099] J0 is calculated; m is the frequency change rate coefficient, which is used to correct the amplitude of the frequency change rate; ω D is the angular frequency dead zone; k is the power ratio coefficient, which is determined by the ratio of the predicted power P at the next moment max1 to the current maximum available power P max0 .

[0100] Here, J, angular velocity, and dω / dt affect each other. In low-frequency events, when the rate of change dω / dt is large, increasing J suppresses the change in dω / dt, reduces the amplitude of the angular velocity, and at the same time, the actual rotor speed of the wind turbine also decreases significantly (the process of releasing rotor kinetic energy); as dω / dt decreases, the wind turbine reduces J according to the decrease in dω / dt, reduces the support force of the unit, and avoids the unit speed from being too low (too low speed is likely to cause a deeper secondary frequency drop). This is an automatic correction process that ultimately reaches a balance.

[0101] Among them, dω / dt is jointly affected by a series of factors such as load, power grid, and the J of the wind turbine. Changing J is the optimization of the unit. J is automatically adjusted according to the frequency change and wind power. While ensuring the safety of the wind turbine itself, it also provides effective support for the power grid and optimizes the system frequency response characteristics, which is a contribution to the system.

[0102] Considering the large range of predicted power changes that gusts may cause, it is necessary to appropriately limit the amplitude of k, as shown in Equation (8).

[0103]

[0104] In the formula, C1 and C2 are the minimum and maximum values of the power ratio coefficients set respectively.

[0105] In summary, the active power k p (ω - ω0) plus the active power value P0 after reserving d%Pn is used as the active power reference value Pref. The difference between Pref and the actual active power P passes through the rotor motion equation composed of the time-varying moment of inertia J to obtain the electromotive force electrical angle θ; the difference between the reference reactive power Qref and the actual reactive power Q passes through the droop coefficient kq and is superimposed on the rated value U0 of the terminal voltage of the machine to obtain the voltage reference value Uref. The difference between Uref and the actual voltage value U passes through the PI controller to obtain the amplitude of the electromotive force; θ and E pass through double closed-loop control and PWM modulation to obtain the switching control signal of the grid-side converter; this process can be seen in the grid-side control block diagram of the wind turbine, as shown in the appendix Figure 3 shown, where U is the measured value of the terminal voltage of the virtual synchronous generator, E is the amplitude of the electromotive force of the virtual synchronous generator, s abc is the switching signal of the grid-side converter, and PWM modulation is Pulse Width Modulation (abbreviated as PWM).

[0106] (2) Machine-side converter control

[0107] According to the existing literature, the voltage control equation of the machine-side converter of the permanent magnet synchronous generator is as shown in Equation (9).

[0108]

[0109] In the formula, usd , u sq and sd , i sq are respectively the stator voltage components on the dq axes; i sq , L sq and s are respectively the inductance components on the dq axes; R s is the stator resistance of the generator; ω f is the electrical angular velocity of the generator rotor; Ψ

[0110] In this method, the machine-side converter of the wind turbine adopts double-loop control. The outer loop controls the DC bus voltage. After the deviation between the voltage reference value Udc* and the actual voltage Udc is adjusted by the PI controller to achieve system decoupling control, the reference value isq* of the active current of the machine-side converter is obtained. There is a deviation from the actual active current isq in the inner loop, giving a signal of different magnitudes to the inner loop. The inner loop controls the current to achieve current tracking control. Among them, after the difference between isq* and the actual active current isq passes through the PI controller, plus the voltage compensation value, the voltage component usq on the q axis is obtained; similarly, after the deviation between the reference value isd* of the reactive current and the actual value passes through the PI controller, plus the voltage compensation, the voltage component usd on the d axis is obtained; usq and usd are modulated by SVPWM (Space Vector Pulse Width Modulation) to obtain the control signal of the machine-side converter, where SVPWM is Space Vector Pulse Width Modulation. Combining the analysis, the control block diagram of the machine-side converter of the wind turbine can be obtained, as shown in the appendix Figure 4 shown.

[0111] Embodiment 2:

[0112] Based on the same inventive concept, the present invention also provides a voltage-source type wind turbine control system. Since the principles of these devices for solving technical problems are similar to those of a voltage-source type wind turbine control method, the repeated parts will not be elaborated here.

[0113] The schematic diagram of the basic structure of this system is as Figure 6 shown, including: a grid-side converter control module and a machine-side converter control module;

[0114] The grid-side converter control module is used for the control of the wind power virtual synchronous generator;

[0115] The machine-side converter control module is used for the machine-side converter to adopt outer-loop DC bus voltage deviation control and inner-loop current tracking control.

[0116] The grid-side converter control module includes: an electromotive force amplitude acquisition unit, an electrical angle acquisition unit, and a grid connection unit; The detailed structure schematic diagram of a voltage-source type wind turbine control system is as Figure 7 shown;

[0117] The electromotive force amplitude acquisition unit is configured to calculate the electromotive force amplitude of the virtual synchronous generator according to the reference value and the measured value of the terminal voltage of the wind power virtual synchronous generator;

[0118] The electrical angle acquisition unit is configured to adjust the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtain the electrical angle of the virtual synchronous generator;

[0119] The grid connection unit is configured to connect to the grid based on the electromotive force amplitude and the electrical angle of the virtual synchronous generator through double closed-loop control and pulse width modulation.

[0120] The machine side converter control module includes: a unit for collecting the actual voltage value, a voltage deviation adjustment unit, an output signal unit, a current tracking control unit, a stator voltage acquisition unit, and a grid connection unit;

[0121] The unit for collecting the actual voltage value is configured to collect the actual value of the DC bus voltage;

[0122] The voltage deviation adjustment unit is configured to adjust the deviation between the actual value and the reference value of the DC bus voltage through a PI controller to achieve system decoupling control, and then obtain the reference value of the active current of the machine side converter;

[0123] The output signal unit is configured to collect the actual active current value of the inner loop. When there is a deviation from the reference value of the active current of the machine side converter, the outer loop gives a signal of different magnitudes to the inner loop;

[0124] The current tracking control unit is configured to control the current after the inner loop obtains the signal to achieve current tracking control;

[0125] The stator voltage acquisition unit is configured to subtract the reference value of the active current of the machine side converter from the actual active current of the inner loop through a PI controller, and then add the voltage compensation value to obtain the q-axis component usq of the stator voltage; similarly, after the deviation between the reference value of the reactive current and the actual value passes through a PI controller and then adds the voltage compensation, the d-axis component usd of the stator voltage is obtained;

[0126] The grid connection unit is configured to input the two stator voltage components into the grid through space vector pulse width modulation.

[0127] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0128] The present application is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a device for implementing the functions specified in Figure 1 one or more of the processes or multiple processes and / or blocks Figure 1 one or more of the blocks or multiple blocks.

[0129] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer-readable memory generate a manufactured article including an instruction device, and the instruction device implements the functions specified in Figure 1 one or more of the processes or multiple processes and / or blocks Figure 1 one or more of the blocks or multiple blocks.

[0130] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one or more of the processes or multiple processes and / or blocks Figure 1 one or more of the blocks or multiple blocks.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application rather than to limit the scope of its protection. Although the present application has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that after reading the present application, various changes, modifications, or equivalent replacements can still be made to the specific implementation manners of the application. However, these changes, modifications, or equivalent replacements are all within the scope of the protection of the pending claims of the application.

Claims

1. A control method for a voltage source type wind turbine generator set, characterized in that, including: For the grid-side converter: Calculating the amplitude of the virtual synchronous generator electromotive force based on the reference value and the measured value of the terminal voltage of the wind power virtual synchronous generator; Adjusting the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtaining the electrical angle of the virtual synchronous generator; Connecting to the grid after double closed-loop control and pulse width modulation based on the amplitude of the virtual synchronous generator electromotive force and the electrical angle; Adopting outer-loop DC bus voltage deviation control and inner-loop current tracking control for the machine-side converter; The adjusting the moment of inertia of the virtual synchronous generator according to the change of the angular velocity of the virtual synchronous generator and the change of the wind power, and then obtaining the electrical angle of the virtual synchronous generator includes: Calculating the power ratio coefficient according to the predicted wind power at the next moment and the current available maximum wind power; Adjusting the moment of inertia of the current virtual synchronous generator according to the power ratio coefficient in combination with the angular velocity of the virtual synchronous generator and the angular velocity of the power grid; Obtaining the electrical angle of the virtual synchronous generator according to the moment of inertia of the current virtual synchronous generator in combination with the angular velocity of the virtual synchronous generator and the angular velocity of the power grid; The calculation formula of the moment of inertia of the virtual synchronous generator is as follows: Where J is, J 0 is the initial moment of inertia, which is determined by the inertia time constant set by the unit; m is the frequency change rate coefficient, which is used to correct the amplitude of the frequency change rate; ω D is the angular frequency dead zone; ω is the angular velocity of the virtual synchronous generator; ω 0 is the grid synchronous electrical angular velocity; k is the power ratio coefficient, which is determined by the predicted power at the next moment P max1 and the current maximum available power P max0 ratio.

2. The method according to claim 1, characterized in that, The calculation formula of the amplitude of the virtual synchronous generator electromotive force is as follows: Wherein, E is, k up and k ui are the proportional and integral coefficients of the PI regulator respectively, s is the Laplace operator, U ref is the reference value of the terminal voltage of the virtual synchronous generator, U is the measured value of the terminal voltage; Among them, the reference value of the terminal voltage of the virtual synchronous generator U ref is calculated as follows: Wherein, U 0 is the rated value of the terminal voltage of the virtual synchronous generator, is the proportionality coefficient, Q is the actual value of the reactive power, Q ref is the reactive power command value; where the actual value of the reactive power output by the virtual synchronous generator, the calculation formula is as follows: Wherein, u a , u b , u c and i a , i b , i c are respectively the three-phase voltages and currents measured by the voltage transformer and current transformer in the virtual synchronous generator.

3. The method according to claim 1, characterized in that, The calculation formula of the power ratio coefficient is as follows: where k is, C1 and C2 are respectively the minimum and maximum values of the set power ratio coefficient, P max1 is the predicted power at the next moment, P max0 is the current maximum available power.

4. The method according to claim 1, characterized in that, The calculation formula of the electrical angle of the virtual synchronous generator is as follows: In the formula, J is the moment of inertia; ω 0 is the grid synchronous electrical angular velocity; T m , T e are the mechanical torque and the electromagnetic torque respectively; D is the damping coefficient; ω , θ are the angular velocity and the electrical angle of the virtual synchronous generator respectively; where the electromagnetic torque of the virtual synchronous generator and the mechanical torque of the virtual synchronous generator are as shown in the following formula: Wherein, P is the active power and electromagnetic power of the virtual synchronous generator Pe is approximately equal to P ref is the active power reference command; wherein, the calculation formulas for the active power of the virtual synchronous generator and the active power reference command are as follows: where $u_a$, $u_b$, $u_c$ and $i_a$, $i_b$, $i_c$ are the three-phase voltages and currents measured by the voltage transformer and current transformer in the virtual synchronous generator respectively, is the active-frequency droop coefficient, and $P_0$ is the initial value of the active power; where the calculation formula of the initial value of the active power is as follows: In the formula, k opt is the optimal control coefficient of the wind turbine, ω w0 is the angular velocity of blade rotation ，d% is the active power reserve rate, P max0 is the power corresponding to the optimal power curve of the wind turbine, P n is the rated power of the wind turbine.

5. The method according to claim 1, characterized in that, The adopting outer-loop DC bus voltage deviation control and inner-loop current tracking control for the machine-side converter specifically includes the following steps: Collecting the actual value of the DC bus voltage; After the deviation between the actual value of the DC bus voltage and the reference value is adjusted by a PI controller to achieve system decoupling control, obtaining the reference value of the active current of the machine-side converter; Collecting the actual active current value of the inner loop, when there is a deviation from the reference value of the active current of the machine-side converter, the outer loop will give a signal of different magnitudes to the inner loop; After the inner loop receives the signal, controlling the current to achieve current tracking control.

6. The method according to claim 5, characterized in that, The collecting the actual active current value of the inner loop, when there is a deviation from the reference value of the active current of the machine-side converter, the outer loop will give a signal of different magnitudes to the inner loop includes: Subtracting the actual active current of the inner loop from the reference value of the active current of the machine-side converter, passing through a PI controller, and adding the voltage compensation value to obtain the q-axis component usq of the stator voltage; After the deviation between the reference value of the reactive current and the actual value passes through a PI controller and adding the voltage compensation, obtaining the d-axis component usd of the stator voltage; The q-axis component usq of the stator voltage and the d-axis component usd of the stator voltage are input into the power grid after space vector pulse width modulation.

7. The method according to claim 6, characterized in that, The dq-axis components of the stator voltage are obtained from the following control equations: where i sd and i sq are the d-axis and q-axis stator current components respectively; L sq and L sq are the d - and q - axis inductance components respectively; R s is the stator resistance of the generator; ω s is the electrical angular velocity of the generator rotor; Ψ f is the magnetic flux of the rotor permanent magnet.

8. A voltage source type wind turbine control system for implementing the method according to claim 1, characterized in that, including: A grid-side converter control module and a machine-side converter control module; The grid-side converter control module is used for controlling the wind power virtual synchronous generator; The machine-side converter control module is used for adopting outer-loop DC bus voltage deviation control and inner-loop current tracking control for the machine-side converter.

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