Power oscillation control method and system for energy storage and damping hybrid direct-drive wind farm

Abstract

The application discloses a kind of energy storage inhibits hybrid direct-drive wind farm power oscillation control method and system, mainly including energy storage device and improved energy storage device control method, for solving the power oscillation problem existing by the mixed type direct-drive wind farm of multiple different control types direct-drive wind turbine composition Access weak power grid. Energy storage device mainly includes energy storage battery pack and three-phase half-bridge circuit, and the control method of energy storage device is to increase the active damping control strategy of virtual synchronous machine control of band pass. The energy storage inhibits hybrid direct-drive wind farm power oscillation control method can effectively improve the stability of hybrid direct-drive wind farm access weak power grid, and enhance the adaptability of hybrid direct-drive wind farm to phase-locked loop bandwidth and output power change under weak power grid condition, and provides an effective solution for the power oscillation problem of hybrid direct-drive wind farm under weak power grid.

Description

Technical Field

[0001] This invention relates to the field of renewable energy power generation, and in particular to a method and system for controlling power oscillations in hybrid direct-drive wind farms by energy storage. Background Technology

[0002] Against the backdrop of addressing environmental pollution and the gradual depletion of resources, wind power has received widespread attention and rapid development worldwide due to its clean and sustainable advantages. Direct-drive wind power generation has also achieved large-scale installed applications due to its high efficiency, low maintenance costs, and small generator size. However, with the continuous increase in wind power installed capacity, the inherent intermittency and volatility of wind power generation pose challenges to the safe and stable operation of the power system. Power oscillation problems in direct-drive wind farms under weak power grids occur frequently, affecting the efficient utilization of wind power resources. Therefore, to ensure the safe and stable operation of the power system and improve the utilization rate of renewable energy, the power oscillation problem of direct-drive wind farms under weak power grids has received extensive attention from scholars. Currently, to suppress the adverse effects of wind speed fluctuations on the output power of direct-drive wind farms, most direct-drive wind farms are equipped with battery energy storage systems to ensure smooth power output, reduce wind curtailment, and provide auxiliary functions such as peak shaving and frequency regulation. Due to differences in direct-drive wind turbine manufacturers, hybrid direct-drive wind farms can exist, consisting of various types of uncontrolled direct-drive wind turbines. Furthermore, the control parameters of these turbines may be unknown, making it difficult to improve the stability of hybrid direct-drive wind farms under weak grid conditions by directly modifying the turbine control parameters or strategies. While some scholars have proposed reducing the output power of direct-drive wind farms to improve grid-connected system stability and suppress power oscillations, this approach fails to maximize the utilization of wind energy resources. Traditional battery energy storage systems, employing current-controlled inverters, also exhibit instability under varying grid strength, failing to effectively improve the stability of hybrid direct-drive wind farms. To enable battery energy storage systems to participate in oscillation suppression in hybrid direct-drive wind farms without adding additional oscillation suppression devices, their control strategies need improvement. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method and system for controlling power oscillations in hybrid direct-drive wind farms by energy storage, which addresses the shortcomings of the existing technology, solves the power oscillation problem of hybrid direct-drive wind farms under weak power grid conditions, improves the adaptability of hybrid direct-drive wind farms to changes in phase-locked loop bandwidth and output power under weak power grid conditions, and ensures the reliable and stable operation of renewable energy power generation systems.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for controlling power oscillation in a hybrid direct-drive wind farm using energy storage, wherein the hybrid direct-drive wind farm includes N current PI-controlled direct-drive wind turbine generators, M current QPR-controlled direct-drive wind turbine generators, L current-controlled VSG direct-drive wind turbine generators, and K energy storage devices. All direct-drive wind turbine generators and energy storage devices are connected to a first step-up transformer via an AC bus, and the first step-up transformer is connected to the power grid. The direct-drive wind turbine generators include DC capacitors, which are connected to a first three-phase half-bridge circuit. The first three-phase half-bridge circuit is connected to a second step-up transformer after passing through an LC filter circuit, and the second step-up transformer is connected to the AC bus. The method includes the following steps:

[0005] S1. Obtain the voltage u on the output side of the second three-phase half-bridge circuit. a u b u c and current i a i b i c The peak output voltage V is calculated. m Output active power P e Output reactive power Q e ;

[0006] S2, utilizing the peak output voltage V m Output active power P e Output reactive power Q e Obtain the output voltage amplitude E of the virtual synchronous machine m and phase angle θ;

[0007] S3, Utilizing the output voltage amplitude E of the virtual synchronizer m The PWM modulated wave signal c is obtained from the phase angle θ. a c b c c For PWM modulated wave signal c a c b c c Modulation is performed to obtain the duty cycle signal of the switching transistors in the second and third phase half-bridge circuits.

[0008] Output active power P e and output reactive power Q e The calculation formula is: u α and u β For voltage u a u b u cVoltage i in the αβ coordinate system α and i β For current i a i b i c Current in the αβ coordinate system.

[0009] Virtual synchronous machine output voltage amplitude E m The calculation formula is: Where K is the reactive power loop inertia coefficient; V n D is the rated phase voltage amplitude; q Q is the reactive power-voltage droop factor. set This is the reactive power command value; V m The peak value of the phase voltage is obtained through calculation.

[0010] The formula for calculating the phase angle θ of the output voltage of a virtual synchronous machine is as follows: Among them, D P ω is the active power loop damping coefficient; n Rated angular frequency; J is the moment of inertia; T e =P e / ω n For virtual electromagnetic torque; P set ω is the command value for active power; ω is the output angular frequency of the virtual synchronizer.

[0011] PWM modulated wave signal c a c b c c The expression is: Among them G f (s) represents a second-order band-stop filter, and its expression is: K min For stopband gain, ω v ξ is the stopband center angular frequency. c G is the damping coefficient of the band-stop filter; n (s) represents a bandpass active damped controller, and its expression is: R v For virtual resistance, ω k ξ is the center angular frequency of the bandpass active damping controller. n u is the damping coefficient of the bandpass active damping controller. α and u β For voltage u a u b u c Voltage i in the αβ coordinate system α and i β For current i a i b i cCurrent in the αβ coordinate system; H L This is the proportional gain of the current loop. K p K is the proportionality coefficient. r ω is the resonance coefficient. c ω is the resonant bandwidth frequency. g It is the resonant angular frequency.

[0012] A hybrid power oscillation suppression control system for direct-drive wind farms, comprising:

[0013] One or more processors;

[0014] A memory having stored one or more programs that, when executed by one or more processors, cause the one or more processors to implement the steps of the method described above.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention improves the control strategy of the traditional centralized energy storage control system and adopts a virtual synchronous machine control method based on bandpass active damping control, which effectively reduces the dynamic interaction between the hybrid direct-drive wind farm and the grid impedance under weak grid conditions, effectively solves the power oscillation problem of the hybrid direct-drive wind farm under weak grid conditions, and enhances the adaptability of the hybrid direct-drive wind farm under weak grid conditions to changes in phase-locked loop bandwidth and output power. Attached Figure Description

[0016] Figure 1 This is a topology diagram of a hybrid direct-drive wind farm according to an embodiment of the present invention;

[0017] Figure 2 This is a simplified circuit and control diagram of a current PI-controlled direct-drive wind turbine generator set according to an embodiment of the present invention;

[0018] Figure 3 This is a simplified circuit and control diagram of a current QPR-controlled direct-drive wind turbine generator set according to an embodiment of the present invention;

[0019] Figure 4 This is a simplified circuit and control diagram of a current-driven VSG direct-drive wind turbine generator set according to an embodiment of the present invention;

[0020] Figure 5 This is a simplified circuit and control diagram of an energy storage converter based on a bandpass active damped control virtual synchronous machine, as described in an embodiment of the present invention.

[0021] Figure 6 Experimental results of hybrid direct-drive wind farms under varying grid strength conditions

[0022] Figure 7 Experimental results of a hybrid direct-drive wind farm with varying phase-locked loop bandwidth.

[0023] Figure 8 The results are experimental findings for a hybrid direct-drive wind farm with varying output power. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In this document, the terms "first," "second," and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms "one," "a," and other similar words are not intended to indicate the existence of only one of the stated things, but rather that the description refers only to one of the stated things, which may have one or more. The terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0026] like Figures 1-5 As shown, Embodiment 1 of the present invention provides a method for controlling power oscillations in a hybrid direct-drive wind farm using energy storage. The method principle includes a hybrid direct-drive wind farm topology, a simplified circuit and control block diagram of the direct-drive wind turbine generator, and a simplified circuit and control block diagram of the energy storage converter. Figure 3 Each part. Figure 1 The diagram shows the topology of a hybrid direct-drive wind farm. The hybrid direct-drive wind farm includes N current-controlled PI direct-drive wind turbine generators, M current-controlled QPR direct-drive wind turbine generators, L current-controlled VSG direct-drive wind turbine generators, and K centralized energy storage control systems. The hybrid direct-drive wind farm is connected to the power grid via a first step-up transformer. Each direct-drive wind turbine generator includes a DC capacitor connected to a three-phase half-bridge circuit. The three-phase half-bridge circuit, after passing through an LC filter circuit, is connected to a second step-up transformer, which is connected to the AC bus. Figure 2 The diagram shown is a simplified circuit and control diagram of a current PI-controlled direct-drive wind turbine generator set. Figure 3The diagram shown is a simplified circuit and control diagram of a current-controlled QPR direct-drive wind turbine generator set. Figure 4 The diagram shows a simplified circuit and control diagram for a current-controlled VSG.

[0027] This invention's hybrid direct-drive wind farm includes N current PI-controlled direct-drive wind turbine generators, M current QPR-controlled direct-drive wind turbine generators, L current-controlled VSG direct-drive wind turbine generators, and K centralized energy storage control systems. The hybrid direct-drive wind farm is connected to the power grid via a first step-up transformer. Each direct-drive wind turbine generator includes a DC capacitor connected to a three-phase half-bridge circuit. The three-phase half-bridge circuit, after passing through an LC filter circuit, is connected to a second step-up transformer, which is connected to an AC bus. The method includes:

[0028] S1. Connect the energy storage battery pack in the energy storage device to the three-phase half-bridge circuit to form a centralized energy storage control system with the energy storage battery pack.

[0029] S2. By adding bandpass active damping control to the voltage and current inner loop of the traditional virtual synchronous machine, a centralized energy storage control system based on the bandpass active damping control virtual synchronous machine is obtained.

[0030] S3. The centralized energy storage control system based on the bandpass active damping control virtual synchronous machine is connected to the AC bus through the second step-up transformer;

[0031] S4. Obtain the voltage u on the output side of the three-phase half-bridge circuit in the centralized energy storage control system. a u b u c and current i a i b i c The peak output voltage V was calculated. m Output active power P e Output reactive power Q e ;

[0032] S5, utilizing the peak output voltage V m Output active power P e Output reactive power Q e Obtain the output voltage amplitude E of the virtual synchronous machine m and phase angle θ;

[0033] S6, Virtual Synchronizer Output Voltage Amplitude E m And the phase angle θ, the PWM modulation wave signal c is obtained according to the inner loop control algorithm based on the bandpass active damped control virtual synchronous machine. a c b c c This enables control of the centralized energy storage control system.

[0034] Figure 5 The diagram shows a simplified circuit and control diagram of an energy storage converter based on a band-pass active damped control virtual synchronous machine according to an embodiment of the present invention. The energy storage battery pack is connected to a three-phase half-bridge circuit to form a centralized energy storage control system with the energy storage battery pack. The voltage u on the output side of the three-phase half-bridge circuit in the centralized energy storage control system is obtained. a u b u c and current i a i b i c The peak output voltage V was calculated. m Output active power P e Output reactive power Q e Output active power P e and output reactive power Q e The calculation equation is shown below:

[0035]

[0036] The equation for calculating the peak output voltage is shown below:

[0037]

[0038] Using the peak output voltage V m Output active power P e Output reactive power Q e Obtain the output voltage amplitude E of the virtual synchronous machine m Phase angle θ; Virtual synchronous machine output voltage amplitude E m The calculation formula is Where K is the reactive power loop inertia coefficient; V n D is the rated phase voltage amplitude; q This is the reactive power-voltage droop coefficient.

[0039] The formula for calculating the phase angle θ of the output voltage of a virtual synchronous machine is as follows: Among them, D P ω is the active power loop damping coefficient; n Rated angular frequency; J is the moment of inertia; T e =P e / ω n This is the virtual electromagnetic torque.

[0040] Virtual synchronous machine output voltage amplitude E m And the phase angle θ, the PWM modulation wave signal c is obtained according to the inner loop control algorithm based on the bandpass active damped control virtual synchronous machine. a c b c c This enables control of the centralized energy storage control system.

[0041] The inner-loop control algorithm based on the bandpass active damped control virtual synchronous machine is as follows:

[0042] Among them G f (s) represents a second-order band-stop filter, and its expression is: K min For stopband gain, ω v ξ is the stopband center angular frequency. c G is the damping coefficient of the band-stop filter; n (s) represents a bandpass active damped controller, and its expression is: R v For virtual resistance, ω k ξ is the center angular frequency of the bandpass active damping controller. n This is the damping coefficient of the bandpass active damping controller.

[0043] In this invention, the PWM modulation wave signal c a c b c c The expression is:

[0044] Using PWM modulated wave signal c a c b c c The duty cycle information of the switching transistors in the three-phase half-bridge circuit is obtained through PWM modulation, and the control of the three-phase half-bridge circuit is realized by the drive circuit.

[0045] To verify the effectiveness of the energy storage-based power oscillation control method for hybrid direct-drive wind farms in enhancing stability under weak grid conditions, this embodiment of the invention provides a method for controlling power oscillations in hybrid direct-drive wind farms by suppressing power oscillations. Grid strength is represented by the short-circuit ratio (SCR). The change in the magnitude of the system's short-circuit ratio is mainly affected by the grid's equivalent impedance. Currently, it is generally believed that when SCR≤2, the grid is an extremely weak grid; when SCR≤6, it is a weak grid; and when SCR≥20, it is a strong grid.

[0046] Assuming N = M = L = K = 2, the output power of the hybrid direct-drive wind farm is P = 1.0 pu, and the phase-locked loop bandwidth is BW = 130 Hz, when the grid strength changes, Figure 6 (a) shows the experimental results of a traditional hybrid direct-drive wind farm using a battery energy storage system with a current-controlled inverter. Figure 6 (a) It can be seen that when the SCR is switched from 10 to 2, the current waveform of the hybrid direct-drive wind farm becomes unstable, and power oscillation problems will occur. Figure 6 (b) shows the experimental results of a hybrid direct-drive wind farm after applying the energy storage suppression power oscillation control method of the present invention embodiment. Figure 6 (b) It can be seen that when the SCR is switched from 10 to 2, the current waveform of the hybrid direct-drive wind farm is stable and the system can operate stably.

[0047] Assuming N = M = L = K = 2, the output power of the hybrid direct-drive wind farm is P = 1.0 pu, and SCR = 2. When the PLL bandwidth BW changes, Figure 7 (a) shows the experimental results of a traditional hybrid direct-drive wind farm using a battery energy storage system with a current-controlled inverter. Figure 7 (a) It can be seen that when the phase-locked loop bandwidth BW is switched from 90Hz to 160Hz, the current waveform of the hybrid direct-drive wind farm becomes unstable, and power oscillation problems will occur. Figure 7 (b) shows the experimental results of a hybrid direct-drive wind farm after applying the energy storage suppression power oscillation control method of the present invention embodiment. Figure 7 (b) It can be seen that when the phase-locked loop bandwidth BW is switched from 90Hz to 160Hz, the current waveform of the hybrid direct-drive wind farm is stable and the system can operate stably.

[0048] Assuming N = M = L = K = 2, the phase-locked loop bandwidth of the hybrid direct-drive wind farm is BW = 150Hz, and the SCR = 2, when the output power changes, Figure 8 (a) shows the experimental results of a traditional hybrid direct-drive wind farm using a battery energy storage system with a current-controlled inverter. Figure 8 (a) It can be seen that when the output power P is switched from 0.5pu to 1.0pu, the current waveform of the hybrid direct-drive wind farm becomes unstable, and power oscillation problem will occur. Figure 8 (b) shows the experimental results of a hybrid direct-drive wind farm after applying the energy storage suppression power oscillation control method of the present invention embodiment. Figure 8 (b) It can be seen that when the output power P is switched from 0.5pu to 1.0pu, the current waveform of the hybrid direct-drive wind farm is stable and the system can operate stably.

[0049] In summary, by adopting the energy storage-based power oscillation control method for hybrid direct-drive wind farms proposed in this invention, the stability of hybrid direct-drive wind farms under weak power grid conditions is improved, and the adaptability of hybrid direct-drive wind farms to changes in phase-locked loop bandwidth and output power under weak power grid conditions is enhanced.

[0050] Example 2

[0051] Embodiment 2 of the present invention provides a system corresponding to Embodiment 1 above, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method of Embodiment 1 above.

[0052] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0053] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0054] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0055] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A method for controlling power oscillations in a hybrid direct-drive wind farm using energy storage, wherein the hybrid direct-drive wind farm includes N current-PI controlled direct-drive wind turbine generators, M current-QPR controlled direct-drive wind turbine generators, L current-controlled VSG controlled direct-drive wind turbine generators, and K energy storage devices; all direct-drive wind turbine generators and energy storage devices are connected to a first step-up transformer via an AC bus, and the first step-up transformer is connected to the power grid; each direct-drive wind turbine generator includes a DC capacitor connected to a first three-phase half-bridge circuit, the first three-phase half-bridge circuit being connected to a second step-up transformer after passing through an LC filter circuit, and the second step-up transformer being connected to the AC bus; characterized in that... The energy storage device includes an energy storage battery pack, which is connected to a second three-phase half-bridge circuit. The second three-phase half-bridge circuit is connected to an AC bus via a third step-up transformer. The method includes the following steps: S1. Obtain the voltage on the output side of the second three-phase half-bridge circuit. u a , u b , u c and current i a , i b , i c The peak output voltage was calculated. V m Output active power P e Output reactive power Q e ; S2, Utilizing the peak output voltage V m Output active power P e Output reactive power Q e Obtain the output voltage amplitude of the virtual synchronizer E m and phase angle θ ; S3. Utilize the output voltage amplitude of a virtual synchronizer E m and phase angle θ Obtain PWM modulated wave signal c a , c b , c c For PWM modulated wave signals c a , c b , c c Modulation is performed to obtain the duty cycle signal of the switching transistors in the second and third phase half-bridge circuits; PWM modulated wave signal c a , c b , c c The expression is: ; ;in G f ( s () represents a second-order band-stop filter, and its expression is: , K min For stopband gain, ω v The stopband center angular frequency, ξ c The damping coefficient of the band-stop filter; G n ( s () represents a bandpass active damping controller, and its expression is: , R v For virtual resistance, ω k The center angular frequency of the bandpass active damping controller, ξ n The damping coefficient of the bandpass active damping controller, u α and u β For voltage u a , u b , u c exist αβ Voltage in coordinate system i α and i β For current i a , i b , i c exist αβ Current in a coordinate system; H L For current loop proportional gain, ，K p This is the proportionality coefficient. K r The resonance coefficient, ω c The resonant bandwidth frequency, ω g It is the resonant angular frequency.

2. The energy storage suppression hybrid direct-drive wind farm power oscillation control method according to claim 1, characterized in that, Output active power P e and output reactive power Q e The calculation formula is: , u α and u β For voltage u a , u b , u c exist αβ Voltage in coordinate system i α and i β For current i a , i b , i c exist αβ Current in a coordinate system.

3. The method for controlling power oscillations in a hybrid direct-drive wind farm with energy storage as described in claim 1, characterized in that, Virtual Synchronous Machine Output Voltage Amplitude E m The calculation formula is: ,in, K The inertia coefficient of the reactive power loop; V n This is the rated phase voltage amplitude; D q The reactive power-voltage droop factor; Q set This is the reactive power command value; V m This represents the peak value of the phase voltage.

4. The method for controlling power oscillation in a hybrid direct-drive wind farm with energy storage suppression according to claim 1, characterized in that, Virtual synchronous machine output voltage phase angle θ The calculation formula is: ,in, D P The active power loop damping coefficient; ω n This is the rated angular frequency; J It is the moment of inertia; T e = P e / ω n This is the virtual electromagnetic torque; P set This is the commanded value for active power; ω Output angular frequency for the virtual synchronizer.

5. A hybrid direct-drive wind farm power oscillation control system with energy storage suppression, characterized in that, include: One or more processors; A memory having stored one or more programs thereon, which, when executed by the one or more processors, cause the one or more processors to perform the steps of the method according to any one of claims 1 to 4.

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