Method and system for smoothing fluctuating power of medium voltage wind power system based on energy router

Abstract

The present invention discloses a method and system for smoothing power fluctuations in a medium-voltage wind power system based on an energy router, which relates to the field of new energy control technology, and solves the problem that when a low-voltage energy storage system is connected to a medium-voltage wind power generation system, the power fluctuation of the power grid is large, resulting in poor power grid operation stability. The key points of the technical solution are: through frequency fluctuation control, the frequency effect speed of the system can be improved. Through the first output power and the second output power, the purpose of simultaneously processing the DC bus fluctuation and the AC side power fluctuation is achieved, optimizing the operation of the wind turbine and enhancing the active support capability of the power grid.

Description

Technical Field

[0001] The present invention relates to the field of new energy control technology, and more specifically, to a method and system for smoothing power fluctuations in a medium-voltage wind power system based on an energy router. Background Art

[0002] The application of Multi Port Energy Router (MPER) enables AC / DC hybrid system to have the characteristics of flexible networking, diverse operation modes, and rich control objects. Combined with the flexible control and fast response of energy storage system, it has the ability to manage energy time, forming a wind-storage joint system, which can enhance the active support capability of wind turbines to the power grid. At present, the research and application of wind-storage joint operation mode are limited to low-voltage wind turbines. By configuring energy storage system on the AC side of wind turbine converter or wind farm booster station, using voltage-type energy storage converter (Power Conversion System, PCS) and energy storage battery to absorb and release wind turbine fluctuation power, the operation of wind turbine is optimized. Low-voltage wind power converter generally adopts two-level H-bridge back-to-back converter topology, and its DC bus voltage generally does not exceed 1200V, and the AC side is generally 690V. The energy storage converter adopts two-level H-bridge PWM converter, and its voltage level also belongs to the low-voltage range.

[0003] As the total capacity and single-unit power of medium-voltage wind power generation systems connected to the grid continue to increase, the randomness of wind energy has brought increasingly severe challenges to wind power generation system power control and grid stability. Compared with traditional low-voltage wind power generation, medium-voltage wind power generation system control and medium-voltage converter operation and fault handling are more complicated. These problems make it difficult to deliver large-scale wind power generation energy and are not conducive to the safe and stable operation of the power grid. Summary of the invention

[0004] The purpose of the present invention is to provide a method and system for smoothing fluctuating power of a medium-voltage wind power system based on an energy router, which can ensure that the power grid is not affected by fluctuating power and improve the safety and stability of the power grid operation by absorbing and releasing the fluctuating power in the medium-voltage wind power system.

[0005] The above technical objectives of the present invention are achieved through the following technical solutions:

[0006] A method for smoothing power fluctuations in a medium-voltage wind power system based on an energy router comprises the following steps: obtaining the output active power of a wind turbine and the current voltage of a battery;

[0007] Performing power distribution on the active power output by the wind turbine to obtain a first active power and a second active power;

[0008] The first active power is the active power that the energy storage converter should provide to the AC bus; the second active power is the active power that the multi-port energy router should provide to the AC bus;

[0009] After receiving the first active power, the energy storage converter provides the first power to the AC bus according to the current voltage of the battery to smooth the power fluctuation;

[0010] After receiving the second active power, the modular multilevel converter provides the second power to the AC bus to smooth power fluctuations.

[0011] Furthermore, the wind turbine output active power acquisition process specifically includes: acquiring a wind turbine speed set value, a wind turbine speed feedback value, a grid connection point frequency rated value, and a grid connection point frequency feedback value;

[0012] The speed difference between the fan speed given value and the fan speed feedback value is compared, and the speed difference is adjusted by the PI controller to obtain the fan maximum power output given value;

[0013] The frequency deviation value is obtained by comparing the grid connection point frequency rated value and the grid connection point frequency feedback value. After the frequency deviation value is adjusted by the frequency-power controller, the power given value corresponding to the frequency disturbance is obtained.

[0014] The maximum power output given value of the fan and the power given value corresponding to the frequency disturbance are first-order filtered to obtain the fan output active power.

[0015] Furthermore, the method for obtaining the fan speed set value is specifically as follows: obtaining the fan speed-power curve, tracking the maximum power of the fan based on the fan speed-power curve, and obtaining the fan speed set value.

[0016] Furthermore, the method for obtaining the fan speed feedback value is specifically as follows: using an optimal tip speed ratio control algorithm to obtain the fan speed feedback value.

[0017] Furthermore, before the first-order filtering of the wind turbine maximum power output given value and the frequency disturbance corresponding power given value, the method further includes: using a variable time constant control algorithm to determine the filter filtering time.

[0018] Furthermore, the specific method for determining the current voltage state of the battery is: determining a power threshold, a maximum battery voltage, and a minimum battery voltage for avoiding frequent operation of the energy storage converter;

[0019] Determining the magnitude between the first active power and a power threshold;

[0020] When the first active power is less than the power threshold, if the current battery voltage is less than the maximum battery voltage, the energy storage converter rectifies and absorbs the first power from the AC bus side, and the battery is in a charging state; if the current battery voltage is not less than the maximum battery voltage, the energy storage converter waits;

[0021] When the first active power is equal to the power threshold, the energy storage converter waits;

[0022] When the first active power is greater than the power threshold, if the current battery voltage is greater than the minimum battery voltage, the energy storage converter inverts and releases the first power to the AC bus side, and the battery is in a discharging state; if the current battery voltage is not greater than the minimum battery voltage, the energy storage converter waits.

[0023] A medium-voltage wind power system based on an energy router is used to implement the above-mentioned medium-voltage wind power system fluctuation power smoothing method based on an energy router, including: an information acquisition module, used to obtain the active power output by the wind turbine and the current voltage of the battery; an energy storage main controller, used to distribute the active power output by the wind turbine to obtain the first active power and the second active power; wherein the first active power is the active power that the energy storage converter should provide to the AC bus; the second active power is the active power that the multi-port energy router should provide to the AC bus; the energy storage system controller is used to, after receiving the first active power, enable the energy storage converter to provide the first power to the AC bus according to the current voltage of the battery to smooth power fluctuations; the multi-port energy router is used to, after receiving the second active power, enable the modular multi-level converter to provide the second power to the AC bus to smooth power fluctuations.

[0024] Furthermore, the medium-voltage wind power system based on the energy router also includes a wind power converter; the multi-port router includes a DAB high-voltage module, a DAB low-voltage module and a modular multi-level converter; the DAB high-voltage module is connected to the DC bus of the wind power converter to control the stability of the DC bus voltage of the wind power converter; the DAB low-voltage module is connected to the battery and the DAB high-voltage module to store the power surge of the DC bus of the wind power converter module in the battery through the DAB low-voltage module.

[0025] Furthermore, the wind power converter includes a machine-side converter and a grid-side converter connected to the machine-side converter via a DC bus, wherein the machine-side converter is connected to a wind turbine, and the grid-side converter is connected to the AC bus.

[0026] Furthermore, the wind turbine is connected to a wind storage controller for obtaining a given value of wind turbine speed, a feedback value of wind turbine speed, a rated value of grid connection point frequency and a feedback value of grid connection point frequency to obtain the output active power of the wind turbine.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. Through frequency fluctuation control, the system frequency response speed can be improved.

[0029] 2. Through the first power and the second power, the DC bus fluctuation and AC side power fluctuation can be processed simultaneously, the operation of the wind turbine can be optimized, and the active support capability for the power grid can be enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the drawings:

[0031] Figure 1 It is a topological diagram of a medium voltage wind power system based on an energy router of the present invention;

[0032] Figure 2 This is a schematic diagram of the MPER topology;

[0033] Figure 3 It is a schematic diagram of energy storage converter;

[0034] Figure 4 This is the block diagram of the wind-storage system power fluctuation smoothing control;

[0035] Figure 5 A coordinated control method for wind-storage systems for frequency response;

[0036] Figure 6 This is the control block diagram of the grid-side converter during low voltage ride-through;

[0037] Figure 7 This is the control block diagram of the grid-side converter during high voltage ride-through;

[0038] Figure 8 This is the control block diagram of the machine-side converter. DETAILED DESCRIPTION

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0040] Embodiment: A method and system for smoothing power fluctuations in a medium voltage wind power system based on an energy router.

[0041] 1. Topology Introduction

[0042] The topology of medium voltage wind power system based on energy router is as follows: Figure 1As shown in the figure, the system consists of a wind power system, an MPER and an energy storage system. The converter topology adopts the mainstream I-type three-level structure, with two back-to-back full-power converters in parallel, and the switching device is IGCT. The MPER is connected to the AC high-voltage side through a modular multilevel converter (MMC), the high-voltage port of the dual active bridge (DAB) is connected to the DC bus of the wind power converter, the low-voltage port of the DAB is connected to the battery of the energy storage system, and the energy storage system converter is connected to the high-voltage AC side through a transformer. The entire system can realize multi-directional controllable flow of energy, and AC and DC isolation.

[0043] Figure 2 The internal topology of MPER is shown in the figure. The AC high voltage side is an H-bridge cascaded MMC circuit. There are two high voltage DC ports and one low voltage DC port, all of which use the DAB modular series circuit as shown in the figure. Figure 1 and Figure 2 , the high-voltage DC port of MPER can absorb and release the fluctuating power input by the wind turbine by controlling the DC bus voltage of the wind power converter. Affected by the battery process, the number of series and parallel connections and the cost, the voltage of the energy storage battery is generally a low voltage below 800V. The DAB circuit solves the problem of matching the battery voltage and the medium voltage of the energy storage system. The energy storage converter adopts a bidirectional PWM converter to stabilize the AC side power through inversion and rectification. When the wind power system is normally connected to the grid, the control objectives of the two DAB high-voltage circuits are to stabilize the DC bus voltage of the wind turbine converter, the outer loop control voltage setting is equal to the DC bus operating voltage, the wind turbine works in the maximum power tracking mode, and the energy storage converter suppresses the AC bus power fluctuation according to the power setting issued by the main controller. When operating in an isolated grid, the wind turbine and MPER adopt V / F or droop control methods, and the energy storage system releases or absorbs energy according to the battery and load conditions. The three systems adopt peer or master-slave operation mode, and the voltage and frequency setting values ​​are given by the master control. When a grid fault occurs, each system executes the corresponding fault handling procedure. The MPER high-voltage circuit absorbs the surge power of the wind turbine DC bus and stores it in the energy storage battery through the low-voltage DAB. The energy storage inverter absorbs or releases power according to the type of fault to maintain the bus voltage stable.

[0044] The energy storage converter adopts Figure 3 The three-phase PWM converter topology shown in the figure. The energy storage converter can operate in four quadrants, charging the battery during rectification operation, rectifying AC power into DC power to charge the battery, discharging the battery during inverter operation, and inverting DC power into AC power to supply the grid or load.

[0045] Compared with traditional wind storage systems, this medium-voltage wind power generation system based on energy router can solve the problems of traditional low-voltage energy storage and medium-voltage wind power access. Moreover, with the help of MPER and energy storage system, it can simultaneously handle the DC bus fluctuations of the wind turbine converter and the AC side power fluctuations, optimize the operation of the wind turbine and enhance the active support capability for the power grid.

[0046] 2. Control Methods

[0047] 2.1 Control methods for smoothing fluctuating power

[0048] like Figure 4 As shown, the energy storage converter and MPER power control strategy are: wind energy P wind After first-order filtering, a smoother active power P' is obtained. wind , P' wind After power distribution, the active power P* that the energy storage system should provide to the AC bus is obtained e , and the active power P provided by MPER to the AC bus * p , P * e and P * p A positive value indicates that active power is output to the AC bus, and a negative value indicates that active power is absorbed from the AC bus. * e and P * p The communication bus transmits the active power to the energy storage system and MPER. The energy storage converter and MMC module absorb or release active power on the AC bus side to smooth out power fluctuations.

[0049] P' wind In the power distribution link, P * e and P * p The value of is determined by the following formula:

[0050]

[0051] Where m is the ratio of the rated capacity of the energy storage converter and the MMC.

[0052] The energy storage system controller determines the operating state of the energy storage converter based on the current battery voltage. When the battery voltage meets the operating conditions, the energy storage converter outputs or absorbs power to smooth the output power fluctuations of the wind turbine generator. d The threshold value set to avoid frequent operation of the energy storage converter, U b is the battery voltage, U bmax and U bmin The maximum and minimum voltage values ​​are set to protect the battery.

[0053] The selection of filtering time T has a great influence on the control effect of the energy storage system. If T is too small, it may lead to an increase in the high-frequency components in the output power of the energy storage converter. If T is too large, the power fluctuation suppression effect is poor. It is necessary to debug and select according to the output characteristics of the fluctuating power supply. Generally, the estimated value is selected according to the characteristics of the fan, and then the variable time constant control algorithm is added to reduce the power fluctuation rate.

[0054] 2.2 Frequency response coordinated control method of wind-storage system

[0055] Figure 5 The wind storage system coordinated control method for frequency response. At the power distribution layer, the wind storage controller implements maximum power tracking according to the wind speed-power curve and obtains the given value of wind turbine speed ω * r , at this time the fan speed set value ω * r And the fan speed feedback value ω r After comparison and passing through the PI controller, the given value P1 reflecting the maximum power output of the fan can be obtained.

[0056] In order to achieve maximum wind power capture (MPPT), the impeller of the wind power generation system needs to run at the optimal tip speed ratio. According to the optimal tip speed ratio control algorithm, the optimal speed value of the generator rotor at a certain wind speed can be obtained, that is, the wind turbine speed feedback value ω r , where the fan speed given value ω * r According to the rotor power control, the given value of the machine-side converter output current i* is obtained d and i* q .

[0057] The frequency response layer obtains the power reference value P2 corresponding to the frequency disturbance according to the grid-connected point voltage frequency rating and feedback value deviation, and frequency-power control (using proportional integral controller). P1 and P2 are added to obtain P wind , P wind The fluctuating power is included, and after filtering and power distribution, the power setpoints of the DAB module and energy storage converter of the MPER are obtained.

[0058] For the frequency response layer, the frequency response speed of the system can be improved by controlling frequency fluctuations. Different operating conditions of the wind turbine need to be considered in the control, and the maximum power output and frequency regulation performance constraints need to be designed.

[0059] 2.3 Sampling and Coordinate Transformation

[0060] The sampling and coordinate transformation principles of the grid-side converter and the machine-side converter are the same. Three AC line voltages, three stator currents and DC bus voltage are sampled. In order to reduce the number of controlled variables, the three stator voltage AC quantities and three current AC quantities sampled in the abc stationary coordinate system are first transformed into two AC variables in the αβ coordinate system, that is, a 3s / 2s transformation is performed, and equal power transformation is adopted to obtain the voltage and current signals in the two-phase stationary coordinate system.

[0061] The coordinate transformation formula from three-phase stationary to two-phase stationary is as shown in formula (1). The transformation matrix is:

[0062]

[0063] Then the AC quantity in the αβ coordinate system is transformed into the DC quantity in the dq rotating coordinate system, and the transformation matrix is:

[0064]

[0065] 2.4 Grid-side converter control

[0066] Figure 6 This is the grid-side control block diagram of the wind turbine converter. The control adopts the grid-oriented control method. For the grid-side converter, the occurrence of low voltage ride through (LVRT) and high voltage ride through (HVRT) must be considered.

[0067] For LVRT, the method of adjusting the pitch angle and combining the fault control strategy is first adopted to maintain the DC bus voltage stability. The control method of the wind turbine side converter is changed from maximum torque control to bus voltage control or given active power control. The grid-side converter outputs power to the grid to reduce the energy accumulation of the DC bus. The MPER AC power and DC voltage are given considering the fault type and ride-through standard.

[0068] For the negative sequence component caused by asymmetric low voltage ride-through, a dual synchronous coordinate system decoupled phase-locked loop (Decoupled Double Synchronous Reference Frame-PLL, DDSRF-PLL) is used to extract the negative sequence component of the converter grid-connected current, set the negative sequence current to zero, and eliminate the power fluctuation caused by the negative sequence voltage and negative sequence current. During the converter LVRT process, the DC bus voltage is also a target that needs to be controlled. Considering the voltage drop imbalance and protection value constraints, according to the requirements of relevant national standards, the active current and reactive current operating equations of the wind power converter are designed. The wind power converter and the MPER AC side output power help the grid voltage recovery.

[0069] Two PI control loops are used, the outer loop is the DC bus voltage loop, and its output is the given value of the inner current loop. * 0 is:

[0070]

[0071] In the formula, k up is the proportional gain of the DC voltage PI controller, k ui is the integral gain, u* dc 、u dc are the given value and feedback value of DC bus voltage respectively. After adding voltage feedforward control, the current inner loop control equation when an unbalanced fault occurs in the power grid is:

[0072]

[0073] In the formula, is the given value of the d-axis and q-axis components of the positive sequence voltage in the dq coordinate system; k ip , k ii They are the proportional coefficient and integral coefficient of the current loop PI controller respectively; is the given value of positive sequence current; is the positive sequence current feedback value; is the positive sequence component of the grid voltage; is the cross-coupling term. Because the inductance L and resistance R of the converter are very small, in order to simplify the calculation, the cross-coupling term can generally be ignored, which will not affect the control effect. Considering that the LVRT standard requires the converter to output reactive power as much as possible to help the grid restore voltage, and in order to protect the safety of the equipment, the output current of the converter must be limited. Therefore, the active and reactive components of the converter output current during the LVRT period are constrained by the following formula:

[0074]

[0075] Where σ (0≤σ≤1) is the grid voltage drop depth. When σ is equal to 0, the grid voltage is zero, that is, zero voltage crossing. When the grid voltage drops deeply, the converter needs to generate reactive power to support the grid voltage. Therefore, the reactive power setting is related to the grid voltage drop depth. As The purpose of setting is to smooth the output current waveform and reduce impact and oscillation. max is the maximum value of the converter output current. Here, the drop depth of 0.45 is selected as the judgment value of the constraint condition, which can be set according to the specific situation in practice. In order to separate the positive and negative sequence components, this paper adopts DDSRF-PLL, and one of the two coordinate systems is synchronized with the positive sequence component and the other is synchronized with the negative sequence component.

[0076] Figure 7This is the control block diagram of the grid-side converter when HVRT occurs. Because the main goal during the fault is to limit the DC bus overvoltage, the DC bus voltage set value is increased according to the fault degree and protection value constraints to improve the voltage and current output capacity of the wind power converter and MPER. During the high voltage ride-through period, the converter needs to absorb reactive power to reduce the grid voltage and help the grid return to normal. In addition, because the voltage increase range in the high voltage ride-through standard is up to 1.3pu, the impact of the asymmetric component generated is also small, and ignoring the negative sequence current has little effect on the control accuracy, and can simplify the calculation and increase the current output capacity, so the negative sequence component is not considered in HVRT.

[0077] Although increasing the DC bus voltage can improve the current output capacity of the grid-side converter, it is also necessary to avoid causing DC bus overvoltage faults. When HVRT occurs, the DC bus voltage reference value is designed to be:

[0078]

[0079] In the formula is the given value of DC bus voltage under normal working condition; σ is the degree of grid voltage increase, which is 0 to 0.3 according to existing standards; k is the adjustment coefficient; u is the DC bus voltage given value when HVRT occurs, which is also the DC voltage given value of the energy router DAB module; dc_max is the maximum value of DC bus voltage.

[0080] The output power factor of the converter is 1 under normal working conditions, and the DC bus voltage is given as When HVRT occurs, the DC bus voltage setting value is This increases the DC bus voltage and enhances the output capacity of the grid-side converter. To avoid overvoltage faults, the DC bus voltage setting value must be less than its overvoltage protection value. During the HVRT period, the converter's reactive current setting value is negative, and the converter absorbs reactive power to reduce the grid voltage. In addition, the asymmetry of HVRT is smaller than that of LVRT, and the impact of the asymmetric components generated is also smaller. In order to simplify the calculation and increase the current output capacity, negative sequence component control is not added.

[0081] 2.5 Machine-side converter control

[0082] In a full-power converter, the grid-side converter controls the DC bus voltage to balance the active power output on the generator side; the generator-side converter controls the electromagnetic torque of the generator to achieve a specific control target. The control block diagram is shown in Figure 8 As shown in the figure, given speed ω * rThe speed difference Δω is obtained by comparing the actual speed ω obtained by feedback, and then the given value i of the active current is obtained through the PI controller. q *, in order to output the maximum torque, let the excitation current, that is, the reactive current given value i d * is 0.

[0083] The rotor power control is realized by the machine-side PWM converter. The machine-side converter control adopts the rotor flux orientation. In the dq axis coordinate system with rotor flux orientation, the control method with d axis current as 0 is adopted. Since the q axis current is proportional to the torque of the generator, the torque (or speed) decoupling control can be realized.

[0084] Specifically, the stator current synthesis vector is first oriented to the q-axis in the dq coordinate system of the permanent magnet synchronous generator, and the d-axis excitation current i d =0, the stator current is all used to generate electromagnetic torque, so that not only the excitation current component and the torque current are decoupled, but also the torque control of the generator is easy to achieve. The following formula is the torque equation of the generator:

[0085] T e =1.5pψ f i q

[0086] T e is the torque, p is the number of pole pairs, ψ f For magnetic link.

[0087] The rotor speed of the generator is obtained by the speed encoder. According to the detected rotor rotation speed, the rotor magnetic field position angle θ is integrated. According to this position angle θ, the detected generator stator current is transformed from the three-phase stationary coordinate system to the two-phase synchronous rotating coordinate system to obtain the torque current component i q and the excitation current component i d , these two quantities serve as feedback quantities for current closed-loop control.

[0088] After obtaining the given and feedback of the excitation current / torque current, the reference given value u′ of the torque voltage / excitation voltage can be obtained through the current regulator. d and u′ q , plus the decoupling term u dc and u qc , we get the control voltage given by u * d and u * q According to the rotor magnetic field position angle θ, u * d and u * q Transform the two-phase synchronous rotating coordinate system to the two-phase stationary coordinate system to obtain u* α and u * β , which is used as the input of the SVPWM module, and its output is the three-phase voltage given u of the machine-side converter * a 、u * b 、u * c .

[0089] 2.6 The main process of controlling sampling transformation is:

[0090] 1. For wind power converter grid-connected converter: sample 3 grid-connected AC line voltages, 3 output AC line currents, 2 DC bus voltage-dividing capacitor voltages, DC bus voltage and generator rotor speed.

[0091] 2. For the machine-side converter of the wind turbine converter: sample three generator stator AC line voltages, three AC line currents and generator rotor speed.

[0092] 3. Transform the AC voltage and AC current from the three-phase stationary abc coordinate system to the two-phase stationary αβ coordinate system to obtain the AC quantity in the two-phase stationary coordinate system. The three-phase stationary to two-phase stationary coordinate transformation formula is shown in formula (1). Transform the variables of the αβ coordinate system to the two-phase dq rotating coordinate system, and the transformation formula is shown in formula (2).

[0093] 4. Current PI regulator design:

[0094] The positive and negative sequence voltages of the grid-side converter and the active and reactive currents of the machine-side converter of the wind power converter are PI regulated respectively, and the integration period is the same as the sampling period of 500 microseconds.

[0095] 5. Modulation algorithm and duty cycle calculation:

[0096] will u * α and u * β The control voltage is converted to a three-phase stationary coordinate system to obtain a three-phase control voltage, and the modulation method adopts a three-level SVPWM.

[0097] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for smoothing power fluctuations in a medium voltage wind power system based on an energy router, characterized in that: The following steps are involved: Obtain the wind turbine output active power and the current battery voltage; Performing power distribution on the active power output by the wind turbine to obtain a first active power and a second active power; The first active power is the active power provided by the energy storage converter to the AC bus; the second active power is the active power provided by the multi-port energy router to the AC bus; After receiving the first active power, the energy storage converter provides the first power to the AC bus according to the current voltage of the battery to smooth the power fluctuation; After receiving the second active power, the modular multilevel converter provides the second power to the AC bus to smooth the power fluctuation; Among them, the medium voltage wind power system based on the energy router includes: energy storage system, multi-port energy router and wind power converter; The energy storage system includes an energy storage converter and a battery, the battery is connected to the energy storage converter, and the energy storage converter is connected to the AC bus through a transformer; The multi-port energy router includes a modular multi-level converter, a DAB low-voltage module and two DAB high-voltage modules, the DAB low-voltage module is connected to the battery, and the modular multi-level converter is connected to the AC bus; The wind power converter includes two back-to-back full-power converters, each of which includes a grid-side converter and a machine-side converter. The grid-side converter and the machine-side converter are connected through a DC bus, each grid-side converter is connected to the AC bus, each machine-side converter is connected to the motor, and two DAB high-voltage modules are respectively connected to the DC buses in the two back-to-back full-power converters.

2. The method for smoothing power fluctuations in a medium voltage wind power system based on an energy router according to claim 1 is characterized in that: The process of obtaining the wind turbine output active power is specifically as follows: Obtain the fan speed set value, fan speed feedback value, grid connection point frequency rated value and grid connection point frequency feedback value; The speed difference between the fan speed given value and the fan speed feedback value is compared, and the speed difference is adjusted by the PI controller to obtain the fan maximum power output given value; The frequency deviation value is obtained by comparing the grid connection point frequency rated value and the grid connection point frequency feedback value. After the frequency deviation value is adjusted by the frequency-power controller, the power given value corresponding to the frequency disturbance is obtained. The maximum power output given value of the fan and the power given value corresponding to the frequency disturbance are first-order filtered to obtain the fan output active power.

3. The method for smoothing power fluctuations in a medium voltage wind power system based on an energy router according to claim 2 is characterized in that: The method for obtaining the fan speed given value is specifically as follows: Obtain the wind speed-power curve of the fan, track the maximum power of the fan based on the wind speed-power curve, and obtain the given value of the fan speed.

4. The method for smoothing power fluctuations in a medium voltage wind power system based on an energy router according to claim 2 is characterized in that: The fan speed feedback value obtaining method is specifically as follows: The optimal tip speed ratio control algorithm is used to obtain the feedback value of the fan speed.

5. The method for smoothing power fluctuations in a medium voltage wind power system based on an energy router according to claim 2 is characterized in that: Before the first-order filtering of the maximum power output given value of the fan and the power given value corresponding to the frequency disturbance, the following steps are also included: The filter filtering time is determined by using a variable time constant control algorithm.

6. The method for smoothing power fluctuations in a medium voltage wind power system based on an energy router according to claim 1 is characterized in that: The specific method for judging the current voltage status of the battery is as follows: Determine the power threshold, maximum battery voltage and minimum battery voltage to avoid frequent operation of the energy storage converter; Determining the magnitude between the first active power and a power threshold; When the first active power is less than the power threshold, if the current battery voltage is less than the maximum battery voltage, the energy storage converter rectifies and absorbs the first power from the AC bus side, and the battery is in a charging state; if the current battery voltage is not less than the maximum battery voltage, the energy storage converter waits; When the first active power is equal to the power threshold, the energy storage converter waits; When the first active power is greater than the power threshold, if the current battery voltage is greater than the minimum battery voltage, the energy storage converter inverts and releases the first power to the AC bus side, and the battery is in a discharging state; if the current battery voltage is not greater than the minimum battery voltage, the energy storage converter waits.

7. A medium voltage wind power system based on an energy router, used to implement a method for smoothing power fluctuations of a medium voltage wind power system based on an energy router as claimed in any one of claims 1 to 6, characterized in that: include: An information acquisition module is used to obtain the wind turbine output active power and the current battery voltage; The energy storage main controller is used to distribute the active power output by the wind turbine to obtain a first active power and a second active power; wherein the first active power is the active power that the energy storage converter should provide to the AC bus; and the second active power is the active power that the multi-port energy router should provide to the AC bus; The energy storage system controller is used to, after receiving the first active power, enable the energy storage converter to provide the first power to the AC bus according to the current voltage of the battery to smooth the power fluctuation; The multi-port energy router is used to receive the second active power, and the modular multi-level converter provides the second power to the AC bus to smooth the power fluctuation.

8. The medium voltage wind power system based on the energy router according to claim 7 is characterized in that: The medium voltage wind power system based on the energy router also includes a wind power converter; The multi-port router includes a DAB high voltage module, a DAB low voltage module and a modular multi-level converter; The DAB high-voltage module is connected to the DC bus of the wind power converter and is used to control the DC bus voltage stability of the wind power converter; The DAB low-voltage module is connected to the battery and the DAB high-voltage module, and is used for absorbing the surge power of the DC bus of the wind power converter module and storing it in the battery through the DAB low-voltage module.

9. The medium voltage wind power system based on the energy router according to claim 8, characterized in that: The wind power converter comprises a machine-side converter and a grid-side converter connected to the machine-side converter via a DC bus, wherein the machine-side converter is connected to a wind turbine, and the grid-side converter is connected to the AC bus.

10. The medium voltage wind power system based on the energy router according to claim 9, characterized in that: The fan is connected to a wind storage controller for obtaining a given value of the fan speed, a feedback value of the fan speed, a rated value of the grid connection point frequency and a feedback value of the grid connection point frequency to obtain the output active power of the fan.

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