A wind-solar complementary stable power generation and intelligent grid-connected system and control method

Abstract

The application relates to the technical field of smart power grids, and discloses a wind-solar power complementary stable power generation and intelligent grid-connection system and a control method, which comprises a photovoltaic power generation unit, an energy storage power station unit, a wind turbine generator set, an intelligent control hub and a solid-state transformer; the intelligent control hub comprises a wind speed change prediction module which acquires a real-time wind speed and determines the operation mode of the wind turbine generator set; an active drive control module controls the energy storage power station unit to supply power to the wind turbine generator set when the real-time wind speed is smaller than a cut-in wind speed threshold value; a disturbance-free switching module stops the energy storage power station unit from supplying power to the wind turbine generator set when the real-time wind speed is greater than or equal to the cut-in wind speed threshold value and the wind energy self-sustaining condition is met; an active damping and support module controls the solid-state transformer to carry out grid-connection power regulation based on the power balance result of a direct-current bus; and a surplus power control module feeds surplus power into an alternating-current power grid. The application prolongs the service life of the unit and improves the grid-connection stability.

Description

Technical Field

[0001] This invention relates to the field of smart grid technology, and more specifically, to a wind-solar hybrid stable power generation and smart grid connection system and control method. Background Technology

[0002] With the accelerated construction of integrated wind, solar, and energy storage clean energy bases, how to mitigate the intermittency and volatility of wind and solar power generation, and improve grid-connected power quality and system stability, has become a core issue of concern for the industry. Traditional wind-solar hybrid systems rely heavily on the simple superposition of natural resources. When the wind speed is lower than the cut-in wind speed of the wind turbine, the turbine shuts down, causing power generation interruptions; and the random fluctuations in power generation put significant pressure on the grid's peak shaving.

[0003] While existing technologies offer solutions for smoothing wind power fluctuations through energy storage systems, these typically manage energy storage as an independent unit for charging and discharging, failing to achieve proactive "feedback" from energy storage to wind turbine start-up and shutdown. Furthermore, traditional power frequency transformers suffer from slow response times and limited functionality in voltage regulation, reactive power compensation, and grid-friendliness. In multi-source microgrid parallel operation, the coupling between the inverter and grid impedance can easily trigger high-frequency or subharmonic oscillations, further reducing system reliability.

[0004] Therefore, it is necessary to design a wind-solar complementary stable power generation and intelligent grid connection system and control method to solve the problems existing in the current technology. Summary of the Invention

[0005] In view of this, the present invention proposes a wind-solar complementary stable power generation and intelligent grid connection system and control method, aiming to solve the above-mentioned problems.

[0006] In one aspect, the present invention proposes a wind-solar complementary stable power generation and intelligent grid connection system, comprising: a photovoltaic power generation unit, an energy storage power station unit, a wind turbine generator set, an intelligent control center, and a solid-state transformer; the intelligent control center includes a wind speed change prediction module, an active drive control module, a disturbance-free switching module, an active damping and support module, and a surplus power control module; The wind speed change prediction module is used to acquire the real-time wind speed of the wind turbine generator set, compare the real-time wind speed with the cut-in wind speed threshold, and determine the operating mode of the wind turbine generator set; the operating mode includes energy storage drive mode and wind power generation mode. The active drive control module is used to determine the energy storage drive mode when the real-time wind speed is less than the cut-in wind speed threshold, and control the energy storage power station unit to supply power to the wind turbine generator set to drive the wind turbine generator set to rotate. The disturbance-free switching module is used to determine whether the wind turbine generator meets the wind energy self-sufficiency condition based on the wind speed change rate and blade rotation speed when the real-time wind speed is greater than or equal to the cut-in wind speed threshold; when the wind energy self-sufficiency condition is met, it is determined to be the wind power generation mode and the energy storage power station unit stops supplying power to the wind turbine generator. The active damping and support module is used to acquire the power status of the photovoltaic power generation unit, wind turbine generator set and energy storage power station unit, and control the solid-state transformer to perform grid-connected power regulation based on the power balance result of the DC bus. The surplus power control module is used to feed surplus power into the AC grid when the total power generation exceeds the load demand.

[0007] Furthermore, when the active drive control module controls the energy storage power station unit to supply power to the wind turbine generator set and drives the wind turbine generator set to rotate, it includes: When the energy storage drive mode is determined, the active drive control module controls the energy storage power station unit to supply power to the variable frequency drive motor mechanically coupled to the wind turbine generator set through a bidirectional DC / AC converter, driving the blades of the wind turbine generator set to rotate at the standby speed; the standby speed is greater than zero and less than the rated grid-connected speed of the wind turbine generator set; The active drive control module obtains real-time speed feedback through the encoder on the variable frequency drive motor and uses a PID closed-loop control algorithm to maintain the speed of the wind turbine generator set.

[0008] Furthermore, when the disturbance-free switching module determines the wind power generation mode and stops the energy storage station unit from supplying power to the wind turbine generator, it includes: The disturbance-free switching module reduces the current output from the energy storage power station unit to the variable frequency drive motor through the bidirectional DC / AC converter, and the variable frequency drive motor exits the drive state; synchronously adjusts the output of the AC / DC converter on the stator side of the wind turbine generator set, and the wind turbine generator set smoothly switches from the energy storage drive mode to the wind power generation mode.

[0009] Furthermore, the solid-state transformer adopts an ISOP topology with series input and parallel output, including: The input stage consists of multiple cascaded H-bridge rectifier modules connected to the DC bus. The isolation stage employs a DAB converter or an LLC resonant converter for high-frequency electrical isolation and voltage transformation. The output stage, consisting of an inverter module, is connected to the AC power grid.

[0010] Furthermore, when the active damping and support module controls the solid-state transformer to perform grid-connected power regulation based on the power balance result of the DC bus, it includes: The active damping and support module embeds a virtual inertia algorithm and a virtual damping algorithm into the inverter stage control of the solid-state transformer to simulate the rotor motion of a synchronous generator. When a subharmonic oscillation caused by multi-source parallel connection is detected, the damping current corresponding to the subharmonic oscillation is injected through the impedance reconstruction capability of the solid-state transformer to suppress the oscillation.

[0011] Furthermore, when the active damping and support module controls the solid-state transformer to perform grid-connected power regulation based on the power balance result of the DC bus, it also includes: When a voltage drop is detected on the grid-connected side, the active damping and support module adjusts the amplitude, frequency, and phase of the output voltage of the solid-state transformer through pre-synchronous closed-loop control to maintain the grid connection; and injects reactive current into the AC grid according to the voltage drop depth to support the recovery of the grid-connected side voltage.

[0012] Furthermore, when the surplus power control module feeds surplus power into the AC power grid, it includes: The residual current control module adjusts the output power factor and output voltage amplitude of the solid-state transformer according to the power balance state of the DC bus, and constrains the harmonic content of the grid-connected current.

[0013] Furthermore, the wind turbine generator set is a direct-drive permanent magnet synchronous wind turbine generator set, and its stator side is connected to the DC bus through an AC / DC converter; the energy storage power station unit is connected to the DC bus and is used to store the surplus power of the photovoltaic power generation unit or the off-peak power of the grid; the energy storage power station unit is connected to the variable frequency drive motor through the bidirectional DC / AC converter.

[0014] Furthermore, the intelligent control center also includes: The state of charge (SOC) of the energy storage power station unit is monitored. When the SOC is less than the lower limit threshold, the energy storage power station unit is prohibited from supplying power to the variable frequency drive motor, and the photovoltaic power generation unit is controlled to charge the energy storage power station unit. When the SOC is greater than the upper limit threshold, the energy storage power station unit is controlled to discharge to the AC grid through the solid-state transformer.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: It overcomes the "start-up dead zone" by actively driving the wind turbine through energy storage, increasing the effective power generation time; maintaining "inertial rotation" avoids mechanical fatigue caused by frequent start-ups and shutdowns of the wind turbine, extending the unit's lifespan; it utilizes the high-frequency control characteristics of solid-state transformers to achieve active damping, solving the subharmonic oscillation problem of multi-source microgrids; and it possesses virtual inertia and low-voltage ride-through capabilities, improving grid connection stability in weak grid environments. Combining photovoltaic, controllable energy storage drive, and natural wind power generation, the total power fluctuation amplitude fed into the solid-state transformer is far lower than that of traditional purely natural wind farms, reducing the impact on the power grid.

[0016] On the other hand, this application also provides a control method for a wind-solar hybrid stable power generation and smart grid-connected system, applied to the aforementioned wind-solar hybrid stable power generation and smart grid-connected system, comprising: The real-time wind speed of the wind turbine generator is obtained, and the real-time wind speed is compared with the cut-in wind speed threshold to determine the operating mode of the wind turbine generator; the operating mode includes energy storage drive mode and wind power generation mode. When the real-time wind speed is less than the cut-in wind speed threshold, the system is determined to be in the energy storage drive mode, and the energy storage power station unit is controlled to supply power to the wind turbine generator set to drive the wind turbine generator set to rotate. When the real-time wind speed is greater than or equal to the cut-in wind speed threshold, the wind turbine generator set is judged to meet the wind energy self-sufficiency condition based on the wind speed change rate and blade rotation speed; when the wind energy self-sufficiency condition is met, the wind power generation mode is determined, and the energy storage power station unit stops supplying power to the wind turbine generator set. The power status of the photovoltaic power generation unit, wind turbine generator set and energy storage power station unit is obtained, and the solid-state transformer is controlled to perform grid-connected power regulation based on the power balance result of the DC bus. When the total power generation exceeds the load demand, the surplus power will be fed into the AC power grid.

[0017] It is understandable that the aforementioned wind-solar hybrid stable power generation and intelligent grid connection system and control method have the same beneficial effects, and will not be elaborated further here. Attached Figure Description

[0018] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a structural block diagram of a wind-solar hybrid stable power generation and intelligent grid connection system provided in an embodiment of the present invention; Figure 2A flowchart of the energy storage-driven wind turbine control logic provided in an embodiment of the present invention; Figure 3 A flowchart illustrating the control method for a wind-solar hybrid stable power generation and intelligent grid-connected system provided in an embodiment of the present invention. Detailed Implementation

[0019] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] In some embodiments of this application, see Figure 1-2 As shown, a wind-solar complementary stable power generation and intelligent grid connection system is proposed, including: a photovoltaic power generation unit, an energy storage power station unit, a wind turbine generator set, an intelligent control center, and a solid-state transformer; the intelligent control center includes a wind speed change prediction module, an active drive control module, a disturbance-free switching module, an active damping and support module, and a surplus power control module. The wind speed change prediction module is used to obtain the real-time wind speed of the wind turbine generator set, compare the real-time wind speed with the cut-in wind speed threshold, and determine the operating mode of the wind turbine generator set; the operating modes include energy storage drive mode and wind power generation mode. The active drive control module is used to determine the energy storage drive mode when the real-time wind speed is less than the cut-in wind speed threshold, and control the energy storage power station unit to supply power to the wind turbine generator set to drive the wind turbine generator set to rotate. The seamless switching module is used to determine whether the wind turbine meets the wind energy self-sufficiency condition based on the wind speed change rate and blade rotation speed when the real-time wind speed is greater than or equal to the cut-in wind speed threshold. When the wind energy self-sufficiency condition is met, the wind power generation mode is determined and the energy storage station unit stops supplying power to the wind turbine. The active damping and support module is used to acquire the power status of photovoltaic power generation units, wind turbine generator sets and energy storage power station units, and control the solid-state transformer to regulate grid-connected power based on the power balance results of the DC bus. The surplus power control module is used to feed surplus power into the AC grid when the total power generation exceeds the load demand.

[0021] This embodiment provides a wind-solar hybrid stable power generation and intelligent grid connection system. The system includes a photovoltaic power generation unit, an energy storage power station unit, a wind turbine generator set, an intelligent control center, and a solid-state transformer. The photovoltaic power generation unit, the energy storage power station unit, and the wind turbine generator set are each connected to a DC bus. The input side of the solid-state transformer is connected to the DC bus, and the output side is connected to the AC power grid. The intelligent control center is communicatively connected to the control interfaces of the photovoltaic power generation unit, the energy storage power station unit, the wind turbine generator set, and the solid-state transformer, respectively, to obtain the operating status of each power generation unit and converter device, and to generate corresponding control commands based on wind speed, wind turbine speed, power generation, load power, energy storage status, and grid-connected electrical parameters.

[0022] The photovoltaic (PV) power generation unit includes a PV array and a DC / DC converter connected to the PV array. The PV array converts solar energy into DC power, and the DC / DC converter regulates the DC voltage output by the PV array to match the voltage level of the DC bus. The intelligent control center acquires the output voltage, output current, and output power of the PV array and controls the output of the DC / DC converter according to the power demand of the DC bus. When the PV power generation exceeds the current load and grid connection requirements, the excess PV power can be transmitted to the energy storage unit for storage. When the energy storage unit is in a charging-allowed state and there is still surplus PV power, the DC / DC converter maintains the DC bus voltage within a set range while simultaneously providing charging power to the energy storage unit.

[0023] An energy storage power station unit includes an energy storage battery pack, a battery management device, and a bidirectional power conversion device. The energy storage battery pack stores surplus electrical energy generated by the photovoltaic power generation unit, and can also store electrical energy input during off-peak hours, provided grid connection conditions are met. The battery management device acquires the state of charge, terminal voltage, current, and operating status of the energy storage battery pack, and transmits the acquired energy storage status to the intelligent control center. One side of the bidirectional power conversion device is connected to the DC bus, and the other side is connected to the energy storage battery pack, enabling the energy storage power station unit to switch between charging and discharging states according to control commands.

[0024] The wind turbine generator set adopts a direct-drive permanent magnet synchronous wind turbine generator set, which includes wind turbine blades, hub, permanent magnet synchronous generator, and stator-side AC / DC converter. The wind turbine blades are mechanically connected to the rotor of the permanent magnet synchronous generator, so that the rotation of the blades directly drives the rotation of the permanent magnet synchronous generator rotor. Due to the direct-drive structure, there is no traditional gearbox between the wind turbine blades and the generator rotor, thereby reducing the mechanical losses caused by gear transmission and the mechanical resistance during low wind speed operation.

[0025] The stator side of the permanent magnet synchronous generator is connected to an AC / DC converter, and the DC side of the AC / DC converter is connected to the DC bus. When the wind turbine is in wind power generation mode, the turbine blades rotate under the action of natural wind and drive the permanent magnet synchronous generator to generate AC power. The AC / DC converter converts the generated AC power into DC power and adjusts the output current according to the voltage status of the DC bus, thereby transmitting the power generated by the wind turbine to the DC bus.

[0026] To maintain the rotation of the wind turbine generator set at low wind speeds, this embodiment incorporates a variable frequency drive motor coupled to its mechanical transmission structure. The variable frequency drive motor can be connected to the wind turbine hub, the generator shaft, or a mechanically coaxial component with the generator rotor, allowing the mechanical torque output by the motor to be transmitted to the rotating components of the wind turbine generator set. The variable frequency drive motor is connected to an energy storage power station unit via a bidirectional DC / AC converter, with the energy storage power station unit providing the necessary electrical energy for operation.

[0027] The intelligent control center includes a wind speed change prediction module, an active drive control module, a disturbance-free switching module, an active damping and support module, and a residual power control module. The wind speed change prediction module acquires real-time wind speed data from wind speed sensors located near the wind turbine. This real-time wind speed data is acquired continuously according to a preset sampling period, forming a continuous wind speed data sequence. The intelligent control center performs temporal correlation processing on the continuous wind speed data to obtain the current wind speed and its trend. It then compares the current wind speed with a preset cut-in wind speed threshold to determine whether the wind turbine has entered the natural wind-driven power generation condition.

[0028] Specifically, when the real-time wind speed is less than the cut-in wind speed threshold, the wind speed change prediction module determines the wind turbine generator set to energy storage drive mode. In this mode, the mechanical energy provided by natural wind is insufficient to maintain the stable power generation speed of the wind turbine generator set. Therefore, the intelligent control center sends a drive command to the energy storage power station unit. After receiving the drive command, the energy storage power station unit converts the DC power energy in the energy storage battery pack into AC power energy suitable for the variable frequency drive motor via a bidirectional DC / AC converter. By adjusting the power supply frequency and output current of the variable frequency drive motor, the variable frequency drive motor generates drive torque.

[0029] In energy storage drive mode, the active drive control module does not directly drive the wind turbine to its rated operating speed, but rather controls it within a preset standby speed range. The standby speed is greater than zero and lower than the wind turbine's rated grid-connected speed; its specific value is determined based on the wind turbine's mechanical structure, starting torque, and rated speed. In this state, the turbine blades remain continuously rotating, keeping the rotating components in a dynamic operating state. This avoids the need to overcome large static friction torques and the initial inertia of the rotating components when restarting the turbine after a long period of inactivity.

[0030] To improve the stability of standby speed control, an encoder is installed on the variable frequency drive motor. The encoder is used to detect the rotor position and speed of the variable frequency drive motor in real time and sends the detection results to the active drive control module. The active drive control module compares the actual speed fed back by the encoder with the preset standby speed, and adjusts the current output from the bidirectional DC / AC converter to the variable frequency drive motor based on the speed deviation between the two, so that the output torque of the variable frequency drive motor is adjusted according to the actual operating state of the fan.

[0031] For example, when the real-time wind speed further decreases, reducing the natural wind driving force on the turbine blades, the turbine speed tends to decrease. The encoder detects that the actual speed is lower than the standby speed. At this time, the active drive control module increases the drive current of the variable frequency drive motor, increasing the drive torque to compensate for the speed decrease caused by the reduced wind speed. Conversely, when the real-time wind speed increases, causing the turbine speed to tend to rise, the output current of the variable frequency drive motor is reduced to decrease the auxiliary drive force, thereby maintaining the turbine speed within the set standby range. Through this closed-loop control, the wind turbine generator set in energy storage drive mode maintains continuous rotation.

[0032] When the wind speed gradually increases and reaches the cut-in wind speed threshold, the wind speed change prediction module does not immediately stop the variable frequency drive motor. Instead, it further combines the wind speed change rate and blade speed to determine whether the natural wind can independently sustain the rotation of the wind turbine generator. Specifically, the intelligent control center determines the wind speed change rate based on continuously acquired wind speed data and simultaneously acquires the blade speed fed back by the encoder or the generator rotor speed corresponding to the blade speed. When the wind speed reaches the cut-in wind speed threshold and the wind speed change trend can meet the requirements for continuous turbine rotation, and the actual turbine speed reaches the preset wind power generation speed range, it is determined that the wind turbine generator meets the wind energy self-sufficiency condition.

[0033] The wind energy self-sufficiency condition is used to prevent the variable frequency drive motor from immediately disengaging due to a sudden increase in wind speed reaching the cut-off wind speed threshold, which would cause the wind turbine speed to drop rapidly and re-enter the energy storage drive mode. In other words, the system does not switch operating modes based solely on a single wind speed threshold, but rather correlates and judges the wind speed, the trend of wind speed change, and the actual wind turbine speed. Only after confirming that the natural wind can continuously provide the mechanical power required to maintain the wind turbine's rotation will the drive power disengagement process be executed.

[0034] When the wind energy self-sufficiency condition is met, the seamless switching module initiates the switch from energy storage drive mode to wind power generation mode. Specifically, the seamless switching module first controls the bidirectional DC / AC converter to gradually reduce the output current supplied to the variable frequency drive motor, thereby gradually reducing the drive torque of the variable frequency drive motor, rather than directly cutting off the power supply to the variable frequency drive motor. At the same time, the seamless switching module adjusts the operating state of the AC / DC converter on the stator side of the wind turbine generator set according to the current speed of the wind turbine generator set and the generator output status, so that the electrical energy generated by the wind turbine generator set gradually takes over the power output on the DC bus.

[0035] During the aforementioned switching process, the output torque of the variable frequency drive motor gradually decreases, and the mechanical driving force of the wind turbine generator gradually transitions from energy storage to natural wind. When the output current of the variable frequency drive motor drops to the preset exit condition, the bidirectional DC / AC converter stops supplying drive current to the variable frequency drive motor, and the variable frequency drive motor exits the drive state. At this time, the AC / DC converter on the stator side of the wind turbine generator enters the normal power generation control state, enabling the wind turbine generator to be driven entirely by natural wind and to transmit electrical energy to the DC bus.

[0036] To avoid significant power fluctuations on the DC bus during switching, the disturbance-free switching module reduces the drive power of the inverter drive motor while simultaneously acquiring the DC bus voltage and the output power of the wind turbine generator. It also synchronously adjusts the output current of the AC / DC converter on the stator side of the wind turbine generator based on changes in DC bus power. As the energy storage drive power gradually decreases, the wind power output increases accordingly, keeping the input power of the DC bus within the allowable range and thus reducing the impact on the DC bus voltage during mode switching.

[0037] The solid-state transformer employs an ISOP topology with series input and parallel output, comprising an input stage, an isolation stage, and an output stage. The input stage consists of multiple cascaded H-bridge rectifier modules, each responsible for DC-side power conversion, forming a conversion structure that meets the input voltage requirements of the solid-state transformer. The input stage is connected to the DC bus to receive DC power from photovoltaic power generation units, wind turbine generators, and energy storage power station units.

[0038] An isolation stage is positioned between the input and output stages to achieve high-frequency power conversion and electrical isolation between the input and output sides. This isolation stage can employ a dual active bridge DAB converter or an LLC resonant converter. When using a DAB converter, the energy transfer direction and power are adjusted by controlling the phase shift relationship of the switching devices on both sides of the converter; when using an LLC resonant converter, the power transfer is changed by adjusting the switching frequency. The appropriate isolation converter structure can be selected based on the actual power rating and isolation voltage level of the system.

[0039] The output stage consists of multiple inverter modules. The DC side of each inverter module is connected to the isolation stage, and the AC side is connected to the AC power grid. The output stage converts the DC power output from the isolation stage into AC power that matches the voltage amplitude, frequency, and phase of the AC power grid. It also adjusts the output active and reactive power according to the grid-connected power commands sent by the intelligent control center.

[0040] During normal system operation, the intelligent control center continuously acquires the output power of the photovoltaic power generation units, wind turbine generators, and energy storage power station units, as well as the load-side power and DC bus voltage. Based on this power data, the intelligent control center determines the current power surplus or deficit of the DC bus. When the sum of photovoltaic and wind power generation is less than the load demand, the energy storage power station units can provide supplementary power based on their own state of charge to reduce the DC bus power deficit. When the renewable energy generation exceeds the load demand, the surplus power is prioritized for charging the energy storage power station units. After the energy storage power station units meet the charging requirements, the remaining power is fed into the AC grid through a solid-state transformer.

[0041] In energy storage drive mode, the discharge power of the energy storage power station unit is simultaneously constrained by the energy storage state of charge (SBC). When the SBC of the energy storage power station unit is within the allowable discharge range, the active drive control module allows the energy storage power station unit to provide drive power to the variable frequency drive motor; when the SBC drops to the preset lower discharge limit, the intelligent control center restricts or prohibits the energy storage power station unit from continuing to supply power to the variable frequency drive motor, and determines whether to continue to maintain standby rotation based on the current wind speed and the operating status of the wind turbine generator. By setting the energy storage discharge boundary, excessive consumption of energy storage power can be avoided in order to maintain the rotation of the wind turbine.

[0042] When photovoltaic power generation is high and wind turbines are in wind power generation mode, both photovoltaic and wind power enter the DC bus. When the total input power on the DC bus exceeds the load power, the intelligent control center first determines whether there is energy storage space based on the state of charge of the energy storage station unit. When the state of charge of the energy storage station unit is lower than the preset charging limit, some surplus energy is allocated to the energy storage station unit for charging; when the energy storage station unit reaches the charging limit or the charging power reaches the allowable value, the remaining surplus energy is allocated to the solid-state transformer, which then outputs it to the AC grid.

[0043] During the surplus power grid connection process, the output stage of the solid-state transformer establishes a grid connection control reference based on the voltage and frequency of the AC grid, and determines the active power output command based on the remaining power of the DC bus. The output stage inverter module adjusts the active component of the grid connection current according to the active power command, and simultaneously adjusts the reactive current component according to the voltage status on the grid connection side, so that the surplus power is delivered to the AC grid in the form of a stable AC current.

[0044] To improve the stability of multiple power electronic converters operating together, the active damping and support module continuously monitors the operating status of both the DC bus side and the AC grid-connected side. When periodic fluctuations in the DC bus voltage or abnormal oscillations in the grid-connected current are detected, the intelligent control center determines the corresponding damping control quantity based on the oscillation signal and sends a damping control command to the output stage of the solid-state transformer. The output stage then adjusts the inverter module's output current according to this control command, generating a damping component in the inverter's output current that is opposite to the target oscillation, thereby reducing the interactive oscillations between the photovoltaic converter, wind power converter, energy storage converter, and solid-state transformer.

[0045] The inverter stage of the solid-state transformer employs a grid-based control method, using virtual inertia and virtual damping control to achieve voltage support characteristics at the output end similar to a synchronous generator. When power disturbances occur in the AC grid, the control system adjusts the active and reactive power output of the inverter based on output voltage, output frequency, and power changes to maintain stable voltage and frequency at the grid connection point. Compared to control methods that only track current based on grid voltage, this control method can actively participate in grid support by utilizing the power conversion capability of the solid-state transformer.

[0046] When a voltage dip occurs in the AC grid, the active damping and support module first acquires the amplitude change of the grid connection point voltage and determines whether the current voltage meets the low-voltage support trigger condition. If the trigger condition is met, the control system maintains the grid connection between the solid-state transformer and the AC grid and increases the reactive current output according to the degree of voltage dip, providing reactive power support to the grid connection point. Simultaneously, it limits the active power output based on the available power of the DC bus to prevent further fluctuations in the DC bus voltage due to excessive active power output during grid voltage dips.

[0047] After the AC grid returns to its normal voltage range, the active damping and support module gradually reduces the reactive power support current based on the voltage recovery status on the grid-connected side, and restores the solid-state transformer's operating state to normal grid-connected power control. By gradually restoring rather than instantaneously disengaging reactive power support, the secondary power surge generated during grid recovery can be reduced.

[0048] In this embodiment, the intelligent control center can also perform unified time-series data acquisition of wind speed, wind turbine speed, wind turbine output power, photovoltaic output power, energy storage state of charge, DC bus voltage, load power, and grid-connected voltage and current. Data collected by different sensors are synchronized before entering the control decision process and form corresponding state data groups according to the same control cycle, enabling wind speed changes to be correlated and judged with wind turbine speed changes, energy storage drive status, and wind turbine power generation status on the same time scale.

[0049] For example, within a control cycle, if the real-time wind speed is lower than the cut-in wind speed threshold, the system first checks whether the energy storage power station unit meets the discharge conditions. If it does, it enters the energy storage drive mode and controls the wind turbine generator to maintain the standby speed. If the real-time wind speed subsequently reaches the cut-in wind speed threshold, it further acquires continuous wind speed data and blade speed data. After confirming that the wind speed has a tendency to maintain the rotation of the wind turbine and that the blade speed is within the allowable power generation range, it gradually reduces the drive current of the variable frequency drive motor and increases the energy output of the AC / DC converter on the stator side of the wind turbine generator, thus completing a smooth switch from energy storage drive to wind power generation.

[0050] If the wind speed decreases again during the switching process, causing the wind turbine to no longer meet the wind energy self-sufficiency requirements, the disturbance-free switching module will re-control the variable frequency drive motor to enter the drive state and restore the auxiliary drive according to the actual wind turbine speed, thereby avoiding frequent start-stop of the wind turbine due to short-term wind speed fluctuations. Thus, the system can determine the operating mode by combining wind speed change trends and wind turbine speed, rather than simply controlling start-stop based on a single wind speed threshold.

[0051] Through the above control process, this embodiment utilizes the energy storage power station unit to provide low-wind-speed auxiliary drive for the wind turbine generator set, enabling the wind turbine generator set to maintain rotation when natural wind is insufficient for direct startup. After natural wind recovers, a smooth transition between energy storage drive and natural wind power generation is achieved by gradually reducing the drive power of the variable frequency drive motor and synchronously establishing the power generation of the wind turbine generator set. Simultaneously, through power coordination among the photovoltaic power generation unit, energy storage power station unit, wind turbine generator set, and solid-state transformer, the electrical energy generated by wind, solar, and energy storage can be distributed according to load demand, energy storage status, and grid connection conditions. Furthermore, the power regulation and grid connection support capabilities of the solid-state transformer are utilized to improve the stable grid connection capability of the multi-source new energy system.

[0052] It should be noted that the cut-in wind speed threshold, standby speed, upper and lower limits of energy storage state of charge, and control cycles of each converter in this embodiment can all be set according to the rated parameters of the specific wind turbine generator set, energy storage battery pack, photovoltaic array, and AC grid, and are not limited to a certain fixed value. PID control, virtual inertia control, virtual damping control, and converter current closed-loop control can all be implemented using existing power electronic control technology. The focus of this embodiment is to combine the continuous rotation of the energy storage-assisted wind turbine, wind energy self-sustaining judgment, gradual switching of drive power, and wind-solar-storage coordinated grid connection control, so that each function works collaboratively under a unified operating status judgment mechanism.

[0053] In this embodiment, the intelligent control center further includes an active damping and support module, a surplus power control module, and an energy storage status management function. The active damping and support module is mainly used to coordinate the power transfer relationship between the photovoltaic power generation unit, the wind turbine generator set, the energy storage power station unit, and the solid-state transformer, and to determine the grid-connected power of the solid-state transformer based on the real-time power balance state of the DC bus. The surplus power control module is used to distribute and grid-connect the surplus power when the renewable energy generation power exceeds the load demand. The energy storage status management function is used to limit the charging and discharging behavior of the energy storage power station unit according to its state of charge, thereby preventing the energy storage power station unit from participating in wind turbine auxiliary drive or surplus power grid connection under overcharged or over-discharged conditions.

[0054] Specifically, the active damping and support modules acquire the output power of the photovoltaic power generation unit, the output power of the wind turbine generator set, the charging and discharging power of the energy storage power station unit, the load-side power, and the DC bus voltage and current, respectively. The output power of the photovoltaic power generation unit can be determined by the input voltage and current of its DC / DC converter; the output power of the wind turbine generator set can be determined by the DC-side voltage and current of its stator-side AC / DC converter; the charging and discharging power of the energy storage power station unit can be determined by the voltage and current on both sides of the bidirectional converter; and the load power is determined by the load-side voltage and current. These data are synchronized in a unified time frame to form the power state data corresponding to the current control cycle.

[0055] After obtaining the aforementioned power state data, the active damping and support module determines the current power balance state of the DC bus. When the sum of photovoltaic power generation and wind power generation is greater than the load power, the DC bus is determined to be in a power surplus state; when the sum of photovoltaic power generation and wind power generation is less than the load power, the DC bus is determined to be in a power deficit state. After determining the power surplus or power deficit, the state of charge of the energy storage station units is further considered to determine whether the energy storage station units participate in power balancing. When the energy storage station units are allowed to charge, a portion of the power surplus is preferentially used for energy storage charging; when the energy storage station units are allowed to discharge, a portion of the power deficit is provided by the energy storage station units; after the energy storage station units reach the charge / discharge boundary, the solid-state transformer regulates the power exchange with the AC grid.

[0056] The solid-state transformer (SSE) employs an ISOP topology with series input and parallel output. Its input stage is connected to the DC bus, and its output stage is connected to the AC grid. After the active damping and support module sends a grid-connected power command to the SSE, the SSE adjusts the active current component of its output stage inverter module according to the command, enabling power changes on the DC bus to be compensated for through power exchange on the AC grid side. When the DC bus experiences a sustained power surplus and the energy storage station unit can no longer absorb the remaining energy, the SSE increases the active power supplied to the AC grid. Conversely, when the DC bus experiences a power deficit and the AC grid allows power to be supplied to the system, the SSE reduces the reverse power supply or absorbs corresponding power from the AC grid to maintain DC bus power balance.

[0057] To improve grid-connected stability when multiple converters operate simultaneously, this embodiment incorporates a virtual inertia control loop and a virtual damping control loop in the inverter stage control of the solid-state transformer. The virtual inertia control loop generates a simulated inertial response based on the solid-state transformer's output power and the frequency changes on the grid side. This prevents the solid-state transformer from immediately generating a sudden power surge of the same amplitude when the grid-connected power changes rapidly; instead, it gradually adjusts the output power according to preset dynamic response characteristics. The virtual damping control loop generates a damping adjustment amount based on the grid-connected frequency deviation, power change trend, or output current change, and superimposes this damping adjustment amount into the voltage or current control command of the inverter stage, thereby reducing the propagation of power oscillations between the multiple converters.

[0058] In practical implementation, the active damping and support module continuously acquires the grid connection point voltage, grid connection current, and DC bus voltage and current, and performs time series analysis on the continuously sampled data. When a periodic change is detected in the grid connection current or DC bus voltage, and the frequency of the periodic change is within the preset subharmonic oscillation detection range, this state is determined to be a subharmonic oscillation state caused by multi-source parallel interaction. The subharmonic oscillation detection range can be set according to the AC grid base frequency and the control bandwidth of each converter in the system, thereby distinguishing it from normal load power fluctuations and grid base frequency changes.

[0059] Upon detecting subharmonic oscillations, the active damping and support module acquires the oscillation amplitude, frequency, and phase corresponding to the subharmonic oscillation, and generates a damping current control quantity based on the oscillation state. This damping current control quantity is used to change the equivalent output impedance of the solid-state transformer's output stage, causing the solid-state transformer to exhibit damping impedance characteristics within the subharmonic oscillation frequency range. Therefore, the solid-state transformer no longer passively transmits power to the DC bus, but actively alters the voltage-current relationship at the grid connection interface using its rapid power electronic control capabilities.

[0060] Specifically, the active damping and support module incorporates a damping component with the opposite phase to the detected oscillation into the inverter stage current control command. When a sustained increase in the grid-connected current at a certain frequency is detected, the control system increases the damping current component at the corresponding frequency, causing this damping current to cancel out the original oscillation current. Once the oscillation amplitude decreases to a preset exit condition, the damping current control quantity is gradually reduced, allowing the solid-state transformer to return to normal grid-connected control. Through this method, low-frequency or subharmonic oscillations caused by the interaction of control components between the photovoltaic power generation unit, wind turbine generator, energy storage power station unit, and solid-state transformer can be reduced.

[0061] When a voltage dip occurs in the AC grid, the active damping and support module acquires the three-phase voltage on the AC output side of the solid-state transformer and determines the deviation between the current grid-connected voltage amplitude and the normal operating voltage. When the grid-connected voltage is detected to be lower than a preset voltage support threshold, it enters the voltage dip support state. In this state, the active damping and support module maintains the grid connection between the solid-state transformer output stage and the AC grid, and determines grid-connected operation reference quantities based on the amplitude, frequency, and phase of the current grid-connected voltage.

[0062] During voltage dip support, pre-synchronization closed-loop control is used to keep the phase and frequency of the solid-state transformer's output voltage consistent with the AC grid. Specifically, the control system acquires the phase angle and frequency of the grid connection point voltage and compares them with the phase angle and frequency of the solid-state transformer's current output voltage. Based on the comparison result, it adjusts the inverter stage switching control signal, causing the solid-state transformer's output voltage to gradually follow the changes in the grid connection point voltage. Therefore, when voltage disturbances occur in the grid, the solid-state transformer can still maintain synchronization with the AC grid, avoiding sudden changes in the grid-connected current due to excessive phase deviation.

[0063] Meanwhile, the active damping and support module determines the reactive power support requirement based on the voltage sag depth. When the grid-connected voltage sag increases, the reactive current command is increased; when the grid-connected voltage gradually recovers, the reactive current command is decreased. The reactive current command is converted into a corresponding reactive current output via the inverter-level current control loop, enabling the solid-state transformer to provide reactive power support to the AC grid. During reactive power support, the control system simultaneously monitors the DC bus voltage to prevent DC bus voltage anomalies caused by limitations in power transmission within the converter during reactive power support.

[0064] Once the AC grid voltage returns to the preset normal operating range, the active damping and support module does not immediately stop reactive power support. Instead, it gradually reduces the reactive current command according to the voltage recovery process, allowing the solid-state transformer to gradually return from the voltage support state to the normal grid-connected state. By setting the above-mentioned entry, maintenance, and exit processes, secondary disturbances caused by rapid changes in reactive power during grid voltage recovery can be reduced.

[0065] Regarding surplus power control, the surplus power control module acquires the output power of the photovoltaic power generation unit, the output power of the wind turbine generator set, the charging and discharging power of the energy storage station unit, and the load power, and determines whether there is surplus power available for grid connection based on the above power status. When the sum of the photovoltaic power generation and the wind power generation exceeds the load demand, and the energy storage station unit has reached its allowable charging state or its acceptable charging power is insufficient to absorb all the surplus power, the surplus power control module determines the surplus power as the grid-connected power.

[0066] After determining the grid-connected power, the surplus power control module sends a grid-connected power command to the output stage of the solid-state transformer. The solid-state transformer adjusts the output current of the inverter module according to the grid-connected power command, converting the surplus electrical energy on the DC bus into AC electrical energy and feeding it into the AC grid. During this process, the grid-connected power is not loaded onto the AC grid all at once, but is gradually adjusted according to changes in the DC bus voltage and the power on the grid-connected side, keeping the rate of change of the grid-connected power within a preset range, thereby reducing the impact of instantaneous changes in wind and solar power generation on the grid-connected power.

[0067] The surplus power control module further adjusts the output power factor of the solid-state transformer based on the DC bus power balance. When surplus active power increases, the active current output is first determined based on the grid-connected voltage status, and then the reactive current output is determined based on reactive power demand, ensuring coordination between the active and reactive components of the grid-connected current. If the grid connection point voltage is within the normal range, surplus active power is output according to the set power factor; if there is a voltage deviation at the grid connection point, the reactive current is adjusted according to the reactive power support command generated by the active damping and support module, thus balancing surplus power feeding and grid voltage support.

[0068] Regarding output voltage amplitude regulation, the residual power control module acquires the real-time voltage amplitude of the AC grid and compares it with the preset grid-connected voltage range. When the AC grid voltage is within the normal range, the output voltage amplitude of the solid-state transformer is kept matched to the grid connection requirements. When the AC grid voltage deviates, the voltage reference value of the output stage inverter module is adjusted according to the voltage deviation to keep the output voltage within the allowable range. Output voltage regulation and grid-connected power regulation work together to avoid significant fluctuations in the grid-connected voltage due to increased residual power.

[0069] To limit harmonic components in the grid-connected current, the residual current control module further acquires real-time sampling data of the grid-connected current and performs frequency component analysis to obtain the harmonic content. When a specific harmonic component is detected to exceed a preset allowable range, the solid-state transformer inverter stage adjusts the current control amount for the corresponding frequency component to make the grid-connected current waveform more sinusoidal. Once the harmonic content returns to the allowable range, the corresponding harmonic compensation control amount is gradually reduced to avoid overcompensation.

[0070] In this embodiment, the operation of the energy storage power station unit is also constrained by its state of charge (SOC). The intelligent control center obtains the real-time SOC of the energy storage power station unit through the battery management device and compares the SOC with preset lower and upper SOC thresholds. The lower SOC threshold is used to limit the energy storage power station unit from continuing to discharge, and the upper SOC threshold is used to limit the energy storage power station unit from continuing to charge, thereby forming a safe operating range for the energy storage power station unit.

[0071] When the state of charge (SBC) of an energy storage unit falls below the minimum SBC threshold, the intelligent control center determines that the energy storage unit is in a prohibited discharge state. In this state, the active drive control module ceases to send discharge commands to the energy storage unit to drive the variable frequency drive motor, and simultaneously restricts the energy storage unit from outputting power to the variable frequency drive motor via the bidirectional DC / AC converter. If the wind turbine is still operating at low wind speeds, the system determines whether to maintain its current rotation state based on the current wind speed and the wind turbine's operating status. If standby rotation cannot be maintained, the wind turbine is allowed to enter a shutdown state to prevent excessive discharge of the energy storage unit due to insufficient stored energy.

[0072] When the energy storage power station unit is in a prohibited discharge state and the photovoltaic power generation unit has available surplus electrical energy, the intelligent control center controls the DC / DC converter of the photovoltaic power generation unit to provide charging power to the energy storage power station unit. The DC power output from the photovoltaic power generation unit enters the energy storage power station unit through the DC bus. The energy storage power station unit adjusts the charging current through a bidirectional power conversion device, allowing the energy storage battery pack to gradually recover its state of charge. During the charging process, the intelligent control center continuously acquires the energy storage state of charge. When the state of charge recovers to the operating range that allows discharge, the prohibited discharge state is lifted, enabling the energy storage power station unit to regain its auxiliary drive and power compensation capabilities.

[0073] When the state of charge (SOC) of an energy storage unit exceeds the upper limit threshold, the intelligent control center determines the energy storage unit to be in a restricted charging state, stopping or reducing the charging power from the photovoltaic power generation unit to the energy storage unit. If the photovoltaic power generation unit and wind turbine generator continue to generate surplus energy at this time, the intelligent control center prioritizes feeding the surplus energy that can no longer be stored into the AC grid through a solid-state transformer.

[0074] When the state of charge (SOC) of the energy storage power station unit exceeds the upper limit threshold and the system has surplus power that allows grid connection, the intelligent control center controls the energy storage power station unit to enter a discharge state through a bidirectional converter, transmitting the stored energy to the DC bus, and then converting it into AC power by a solid-state transformer to feed into the AC grid. This discharge process is not solely based on the SOC, but is simultaneously constrained by the AC grid operating status, the DC bus power status, and the grid-connected power limit. When the AC grid lacks additional power receiving capacity or the grid-connected power reaches the set upper limit, the discharge power of the energy storage power station unit is limited.

[0075] For example, under conditions of strong sunlight and high wind speeds during the day, both photovoltaic power generation units and wind turbine generators supply power to the DC bus simultaneously. When the load power is low and the energy storage station unit has not yet reached its state of charge limit, the system uses some of the surplus energy for energy storage charging. Once the energy storage station unit reaches its state of charge limit, the system stops increasing the energy storage charging power and feeds the remaining surplus energy into the AC grid through a solid-state transformer. At this time, the surplus power control module adjusts the grid-connected power according to the DC bus power changes, ensuring that the renewable energy generation power can be smoothly transmitted to the AC grid.

[0076] For example, at night or in situations with weak sunlight and wind speeds below the cut-in wind speed, photovoltaic power generation is low, and the wind turbine needs to enter energy storage drive mode. If the state of charge (SBC) of the energy storage unit is higher than the lower threshold, the energy storage unit is allowed to drive the inverter motor through a bidirectional DC / AC converter, keeping the wind turbine rotating in standby mode. If the SBC has dropped to the lower threshold, driving the inverter motor is prohibited, and the energy storage unit enters a charging standby state. This control method prevents the energy storage unit from entering an over-discharge state to maintain continuous wind turbine rotation.

[0077] For example, when a wind turbine is in wind power generation mode, a photovoltaic power generation unit is continuously outputting electricity, and the load power suddenly decreases, the power surplus on the DC bus increases. The active damping and support module first detects the change in the DC bus power balance and determines whether the energy storage can absorb the increased power based on the state of charge of the energy storage unit. If the energy storage unit has charging space, the energy storage charging power is increased; if the energy storage unit has reached its state of charge limit, the surplus power control module increases the grid-connected active power of the solid-state transformer, allowing the surplus electricity to be output to the AC grid. During the increase in grid-connected power, the solid-state transformer simultaneously adjusts reactive power support and harmonic compensation according to the grid-connected voltage and current state, thereby avoiding significant grid-connection disturbances caused by surplus electricity being fed into the grid.

[0078] When photovoltaic or wind power generation declines rapidly, the DC bus power may shift from a surplus to a deficit. In this situation, the active damping and support module determines the power deficit based on DC bus voltage changes and controls the energy storage unit to increase its discharge power when the unit's state of charge meets discharge conditions, thus supplementing the DC bus power deficit. If the energy storage unit cannot provide sufficient power, a solid-state transformer obtains supplementary power from the AC grid side based on grid-connected operating conditions to reduce the impact of rapid changes in renewable energy output on load power supply stability.

[0079] During the aforementioned operational processes, the intelligent control center coordinates the wind turbine operating mode, energy storage operating status, DC bus power status, and solid-state transformer grid connection status. Specifically, the wind speed change prediction module is responsible for determining whether the wind turbine generator has the conditions for natural wind drive; the active drive control module is responsible for controlling the energy storage to drive the wind turbine to maintain rotation under low wind speed conditions; the disturbance-free switching module is responsible for reducing the auxiliary drive power and completing the wind power generation mode switch after the natural wind recovers; the active damping and support module is responsible for controlling the solid-state transformer to perform power balancing, oscillation suppression, and voltage support based on the DC bus power status and AC side disturbance conditions; the surplus power control module is responsible for grid-connecting and outputting surplus power that cannot be absorbed by the load and energy storage; and the energy storage status management function constrains the charging and discharging boundaries of the energy storage power station units.

[0080] Through the above implementation methods, photovoltaic power generation units, wind turbine generators, and energy storage power station units can collect energy under a unified DC bus, and utilize solid-state transformers to achieve bidirectional energy regulation between the DC side and the AC grid. Under low wind speed conditions, the energy storage power station unit can drive the wind turbine generator to maintain low-speed rotation. After wind speed recovers, it switches to wind power generation mode by judging wind energy self-sufficiency conditions and gradually reducing the drive current. In multi-source parallel operation, grid-connected oscillation suppression is achieved through the virtual inertia, virtual damping, and impedance regulation of the solid-state transformer. When grid voltage drops, grid-connected operation is maintained through reactive current support. When the power generation of new energy exceeds the load demand, the surplus energy is coordinated and distributed between the energy storage and the AC grid based on the energy storage state of charge and the DC bus power balance results, thereby improving the continuous operation capability, power regulation capability, and grid-connected stability of the wind-solar hybrid power generation system.

[0081] Based on another preferred embodiment described above, see [link to preferred embodiment]. Figure 3 As shown, this embodiment provides a control method for a wind-solar hybrid stable power generation and smart grid-connected system, applied to the aforementioned wind-solar hybrid stable power generation and smart grid-connected system, including: The real-time wind speed of the wind turbine is obtained and compared with the cut-in wind speed threshold to determine the operating mode of the wind turbine. The operating modes include energy storage drive mode and wind power generation mode. When the real-time wind speed is less than the cut-in wind speed threshold, the system is set to energy storage drive mode, which controls the energy storage power station unit to supply power to the wind turbine generator set and drive the wind turbine generator set to rotate. When the real-time wind speed is greater than or equal to the cut-in wind speed threshold, the wind turbine generator set is judged to meet the wind energy self-sufficiency condition based on the wind speed change rate and blade speed. When the wind energy self-sufficiency condition is met, the wind power generation mode is determined and the energy storage station unit stops supplying power to the wind turbine generator set. The system acquires the power status of photovoltaic power generation units, wind turbine generator sets, and energy storage power station units, and controls the solid-state transformer to regulate grid-connected power based on the power balance results of the DC bus. When the total power generation exceeds the load demand, the surplus power is fed into the AC grid.

[0082] In summary, actively driving wind turbines with energy storage overcomes the "start-up dead zone," increasing the effective power generation time; maintaining "inertial rotation" avoids mechanical fatigue caused by frequent turbine start-ups and shutdowns, extending unit lifespan. Utilizing the high-frequency control characteristics of solid-state transformers achieves active damping, solving the subharmonic oscillation problem in multi-source microgrids; possessing virtual inertia and low-voltage ride-through capabilities improves grid connection stability in weak grid environments. Combining controllable photovoltaic and energy storage-driven power generation with natural wind power results in a significantly lower total power fluctuation amplitude fed into the solid-state transformer compared to traditional purely natural wind farms, reducing the impact on the power grid.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention.

Claims

1. A wind-solar hybrid stable power generation and intelligent grid connection system, characterized in that, include: The system includes a photovoltaic power generation unit, an energy storage power station unit, a wind turbine generator set, an intelligent control center, and a solid-state transformer; the intelligent control center includes a wind speed change prediction module, an active drive control module, a disturbance-free switching module, an active damping and support module, and a residual power control module. The wind speed change prediction module is used to acquire the real-time wind speed of the wind turbine generator set, compare the real-time wind speed with the cut-in wind speed threshold, and determine the operating mode of the wind turbine generator set; the operating mode includes energy storage drive mode and wind power generation mode. The active drive control module is used to determine the energy storage drive mode when the real-time wind speed is less than the cut-in wind speed threshold, and control the energy storage power station unit to supply power to the wind turbine generator set to drive the wind turbine generator set to rotate. The disturbance-free switching module is used to determine whether the wind turbine generator meets the wind energy self-sufficiency condition based on the wind speed change rate and blade rotation speed when the real-time wind speed is greater than or equal to the cut-in wind speed threshold; when the wind energy self-sufficiency condition is met, it is determined to be the wind power generation mode and the energy storage power station unit stops supplying power to the wind turbine generator. The active damping and support module is used to acquire the power status of the photovoltaic power generation unit, wind turbine generator set and energy storage power station unit, and control the solid-state transformer to perform grid-connected power regulation based on the power balance result of the DC bus. The surplus power control module is used to feed surplus power into the AC grid when the total power generation exceeds the load demand.

2. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 1, characterized in that, When the active drive control module controls the energy storage power station unit to supply power to the wind turbine generator set and drives the wind turbine generator set to rotate, it includes: When the energy storage drive mode is determined, the active drive control module controls the energy storage power station unit to supply power to the variable frequency drive motor mechanically coupled to the wind turbine generator set through a bidirectional DC / AC converter, driving the blades of the wind turbine generator set to rotate at the standby speed; the standby speed is greater than zero and less than the rated grid-connected speed of the wind turbine generator set; The active drive control module obtains real-time speed feedback through the encoder on the variable frequency drive motor and uses a PID closed-loop control algorithm to maintain the speed of the wind turbine generator set.

3. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 2, characterized in that, When the disturbance-free switching module determines the wind power generation mode and stops the energy storage station unit from supplying power to the wind turbine generator, it includes: The disturbance-free switching module reduces the current output from the energy storage power station unit to the variable frequency drive motor through the bidirectional DC / AC converter, and the variable frequency drive motor exits the drive state; synchronously adjusts the output of the AC / DC converter on the stator side of the wind turbine generator set, and the wind turbine generator set smoothly switches from the energy storage drive mode to the wind power generation mode.

4. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 3, characterized in that, The solid-state transformer adopts an ISOP topology with series input and parallel output, including: The input stage consists of multiple cascaded H-bridge rectifier modules connected to the DC bus. The isolation stage employs a DAB converter or an LLC resonant converter for high-frequency electrical isolation and voltage transformation. The output stage, consisting of an inverter module, is connected to the AC power grid.

5. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 4, characterized in that, When the active damping and support module controls the solid-state transformer to perform grid-connected power regulation based on the power balance result of the DC bus, it includes: The active damping and support module embeds a virtual inertia algorithm and a virtual damping algorithm into the inverter stage control of the solid-state transformer to simulate the rotor motion of a synchronous generator. When a subharmonic oscillation caused by multi-source parallel connection is detected, the damping current corresponding to the subharmonic oscillation is injected through the impedance reconstruction capability of the solid-state transformer to suppress the oscillation.

6. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 5, characterized in that, When the active damping and support module controls the solid-state transformer to perform grid-connected power regulation based on the power balance result of the DC bus, it also includes: When a voltage drop is detected on the grid-connected side, the active damping and support module adjusts the amplitude, frequency, and phase of the output voltage of the solid-state transformer through pre-synchronous closed-loop control to maintain the grid connection; and injects reactive current into the AC grid according to the voltage drop depth to support the recovery of the grid-connected side voltage.

7. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 6, characterized in that, When the surplus power control module feeds excess power into the AC power grid, it includes: The residual current control module adjusts the output power factor and output voltage amplitude of the solid-state transformer according to the power balance state of the DC bus, and constrains the harmonic content of the grid-connected current.

8. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 7, characterized in that, The wind turbine generator set is a direct-drive permanent magnet synchronous wind turbine generator set, and its stator side is connected to the DC bus through an AC / DC converter; the energy storage power station unit is connected to the DC bus and is used to store the surplus power of the photovoltaic power generation unit or the off-peak power of the grid; the energy storage power station unit is connected to the variable frequency drive motor through the bidirectional DC / AC converter.

9. The wind-solar complementary stable power generation and intelligent grid connection system according to claim 8, characterized in that, The intelligent control center also includes: The state of charge (SOC) of the energy storage power station unit is monitored. When the SOC is less than the lower limit threshold, the energy storage power station unit is prohibited from supplying power to the variable frequency drive motor, and the photovoltaic power generation unit is controlled to charge the energy storage power station unit. When the SOC is greater than the upper limit threshold, the energy storage power station unit is controlled to discharge to the AC grid through the solid-state transformer.

10. A control method for a wind-solar hybrid stable power generation and intelligent grid-connected system, applied to the wind-solar hybrid stable power generation and intelligent grid-connected system as described in any one of claims 1-9, characterized in that, include: The real-time wind speed of the wind turbine generator is obtained, and the real-time wind speed is compared with the cut-in wind speed threshold to determine the operating mode of the wind turbine generator; the operating mode includes energy storage drive mode and wind power generation mode. When the real-time wind speed is less than the cut-in wind speed threshold, the system is determined to be in the energy storage drive mode, and the energy storage power station unit is controlled to supply power to the wind turbine generator set to drive the wind turbine generator set to rotate. When the real-time wind speed is greater than or equal to the cut-in wind speed threshold, the wind turbine generator set is judged to meet the wind energy self-sufficiency condition based on the wind speed change rate and blade rotation speed; when the wind energy self-sufficiency condition is met, the wind power generation mode is determined, and the energy storage power station unit stops supplying power to the wind turbine generator set. The power status of the photovoltaic power generation unit, wind turbine generator set and energy storage power station unit is obtained, and the solid-state transformer is controlled to perform grid-connected power regulation based on the power balance result of the DC bus. When the total power generation exceeds the load demand, the surplus power will be fed into the AC power grid.

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