Energy storage enhanced wind turbine generator system with network construction capability

Abstract

The invention relates to the technical field of wind power generation and power electronic control, and discloses an energy storage enhanced wind turbine generator system with network construction capability, which comprises a wind energy capturing and converting unit, a direct current bus transmission unit, a network construction type energy storage subsystem and a network construction cooperative control unit, the direct-current bus serves as an energy hub to be connected with the machine-side and grid-side converters, and the energy storage subsystem is connected to the direct-current bus in parallel; a state sensing module, a heat surplus management module and a frequency domain energy distribution module are arranged in the control unit to cooperatively control the converters. According to the invention, the high-frequency instruction is distributed to the energy storage unit through frequency domain energy distribution, and mechanical response hysteresis is solved; a carrier frequency is reconstructed in a transient state by using a dual-mode modulation strategy and an algorithm is switched, so that loss is reduced and thermal runaway is prevented; the active damping and ripple suppression algorithm is combined, transmission chain torsional vibration and direct current voltage ripples are effectively suppressed, the networking stability of the wind turbine generator is improved, and the service life of the wind turbine generator is prolonged.

Description

Technical Field

[0001] This invention relates to the field of wind power generation and power electronic control technology, specifically to an energy storage-enhanced wind turbine system with grid-connected capability. Background Technology

[0002] With the advancement of energy transition and dual-carbon goals, the penetration rate of new energy sources, represented by wind power, in the power system is continuously increasing, gradually replacing traditional synchronous generator units. However, traditional wind turbine units typically employ grid-following control strategies, which cannot provide the inertia and voltage support similar to synchronous generators, leading to a decrease in frequency and voltage stability of the power system when facing disturbances. Therefore, grid-following control technology, which can simulate the characteristics of synchronous generators, has become a key direction for solving this problem.

[0003] While grid-based control technology can improve grid stability, its practical application in wind turbines still faces challenges. Wind turbines rely on randomly fluctuating wind energy. Although their core components, the rotor and generator rotor, possess significant physical inertia, their power response time constants are typically on the order of seconds or even longer due to the mechanical characteristics of the pitch system and drivetrain. This makes it difficult to match the grid's primary frequency regulation and the millisecond-level power support requirements of inertial response. This mismatch in electromechanical timescales leads to hysteresis in the response of wind turbines when relying solely on rotor kinetic energy for rapid frequency response. Furthermore, it easily triggers severe torsional vibration in the drivetrain, exacerbating fatigue wear of mechanical components and shortening equipment lifespan.

[0004] Furthermore, in grid-connected operation mode, when a grid fault or sudden load change occurs, the converter needs to instantly provide a huge amount of active or reactive current to maintain voltage and frequency stability. Existing wind power converters typically employ fixed switching frequencies and a single pulse width modulation strategy. Under high load or transient impact conditions, power devices (such as IGBTs) face significant switching losses and temperature rise pressure, easily leading to thermal runaway risks, causing converter protection tripping or even damage, thus losing grid-connected support capabilities. Simultaneously, frequent power exchange and switching actions within the wind turbine introduce high-frequency ripple voltage into the DC bus. Without effective suppression measures, this will accelerate the aging of the DC bus capacitors, further reducing the operational reliability of the entire unit system. Existing technologies struggle to simultaneously address the aforementioned multi-physics coupling problems, such as mechanical hysteresis, electrical thermal overload, and electromechanical coupled vibration, within a single control framework. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides an energy storage-enhanced wind turbine system with grid-connection capabilities. This system solves the problems faced by existing wind turbines during grid-connection operation, such as insufficient power support due to mechanical response lag, the risk of converter thermal runaway under transient high-power impacts, and torsional vibration of the transmission chain and DC bus voltage fluctuations caused by electromechanical coupling.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides an energy storage-enhanced wind turbine system with grid-connection capability, comprising: The system comprises a wind energy capture and conversion unit, a DC bus transmission unit, a grid-based energy storage subsystem, and a grid-based collaborative control unit. The wind energy capture and conversion unit converts wind energy into electrical energy and feeds it into the power grid. This unit consists of a wind turbine, a generator, a generator-side converter, and a grid-side converter. The wind turbine is mechanically connected to the generator rotor, and the generator stator windings are electrically connected to the AC side of the generator-side converter.

[0007] The generator-side converter controls the generator's torque and flux, converting the alternating current (AC) generated by the generator into direct current (DC). The AC side of the grid-side converter is connected to the power grid. The DC bus transmission unit connects the DC sides of the generator-side converter and the grid-side converter, serving as a hub for energy exchange within the system. Its positive and negative terminals are connected to the DC ports of the generator-side converter and the grid-side converter, respectively.

[0008] The grid-based energy storage subsystem includes energy storage battery units and energy storage converters. One end of the energy storage converter is connected to the energy storage battery unit, and the other end is connected in parallel to the positive and negative terminals of the DC bus transmission unit. The grid-based collaborative control unit establishes communication connections with the machine-side converter, the grid-side converter, and the energy storage converter through signal transmission lines.

[0009] The control unit is equipped with a voltage acquisition module and a frequency acquisition module, which are used to send torque control commands to the generator-side converter, reactive power control commands to the grid-side converter, and carrier frequency commands, modulation mode commands, and current reference commands to the energy storage converter, thereby achieving coordinated power output.

[0010] In the above system, the DC bus transmission unit may include a thin-film capacitor bank. The thin-film capacitor bank consists of multiple metallized thin-film capacitors connected between the positive and negative terminals of the DC bus transmission unit to support the DC bus voltage and absorb high-frequency switching ripple.

[0011] The network-based collaborative control unit is further divided into a state awareness and mode discrimination module, a thermal surplus management and dual-mode modulation module, and a frequency domain energy collaborative allocation module. The state awareness and mode discrimination module assesses the operating environment and outputs a mode flag signal. The thermal surplus management and dual-mode modulation module receives this mode flag signal and generates the carrier frequency command and modulation mode command for the energy storage converter accordingly. The frequency domain energy collaborative allocation module decomposes the network power reference value into the instantaneous power command for the energy storage converter and the torque control command for the generator-side converter.

[0012] Specifically, the state perception and mode discrimination module includes a differentiation unit and a comparison unit. The differentiation unit receives the DC bus voltage signal and calculates the rate of change of the DC bus voltage over time. The comparison unit compares the absolute value of this rate of change with a preset voltage dynamic threshold and compares the grid frequency signal with a preset frequency stability range. When the absolute value of the rate of change is less than the voltage dynamic threshold and the grid frequency is within the frequency stability range, the state perception and mode discrimination module outputs a steady-state filtering mode flag; when the absolute value of the rate of change is greater than or equal to the voltage dynamic threshold, or the grid frequency exceeds the frequency stability range, it outputs a grid transient mode flag.

[0013] The thermal redundancy management and dual-mode modulation module includes a switching frequency dynamic reconstruction unit and a modulation strategy switching unit. The switching frequency dynamic reconstruction unit has a frequency lookup table storing high-frequency and low-frequency values. When a steady-state filtering mode flag is received, a high-frequency value is selected as the carrier frequency command; when a network transient mode flag is received, a low-frequency value is selected as the carrier frequency command. The modulation strategy switching unit is used to switch between the space vector pulse width modulation (SVM) algorithm and the discontinuous pulse width modulation (DPWM) algorithm. In steady-state filtering mode, the SVM algorithm is activated; in network transient mode, the DPWM algorithm is activated.

[0014] To ensure the reliability of the switching process, the thermal surplus management and dual-mode modulation modules are equipped with synchronous switching logic. This logic preloads the new carrier frequency command and modulation mode parameters into the shadow register of the energy storage converter, and simultaneously updates the parameters through atomic operations when the current pulse width modulation period counter returns to zero.

[0015] The frequency domain energy collaborative allocation module is equipped with a digital filter bank and a ramp function generator. The digital filter bank is used to decompose the grid power reference value into high-frequency and low-frequency components. The high-frequency component is directly used as the instantaneous power command of the energy storage converter to take advantage of the fast response characteristics of energy storage; the low-frequency component is converted into the torque control command of the turbine-side converter through the ramp function generator to adapt to the mechanical characteristics of the wind turbine.

[0016] Furthermore, the frequency domain energy collaborative allocation module also integrates active damping control logic. This logic analyzes the spectrum of the generator speed signal and extracts the torsional vibration frequency component of the transmission chain, calculates the damping power signal with the same frequency but opposite phase as the torsional vibration frequency, and superimposes this damping power signal onto the high-frequency component of the energy storage converter. Before superposition, the damping power signal passes through an energy neutralization processing unit, which ensures that the average value of the damping power signal is zero over a complete oscillation cycle, thus not affecting the average energy balance of the system.

[0017] In steady-state filtering mode, the network-coordinated control unit also activates an active ripple suppression algorithm. This algorithm extracts the ripple component from the measured value of the DC bus voltage, calculates the inverted compensation current reference value, and superimposes this compensation current reference value into the total current command of the energy storage converter, controlling the output compensation current of the energy storage converter to suppress the DC bus voltage ripple.

[0018] This invention provides an energy storage-enhanced wind turbine system with grid-connection capability. It offers the following advantages: 1. This invention integrates a grid-type energy storage subsystem through a DC bus transmission unit and uses a frequency domain energy collaborative distribution module to decompose the grid power reference value into high-frequency and low-frequency components. The high-frequency power command is handled by the fast-responding energy storage converter, while the low-frequency power command is handled by the turbine-side converter. This frequency division control strategy leverages the millisecond-level response advantage of the energy storage battery, enabling it to quickly provide inertial support and primary frequency regulation energy. At the same time, it avoids the wind turbine mechanical components from frequently experiencing high-frequency power fluctuations, thereby enhancing the grid-type capability of the system while ensuring mechanical safety.

[0019] 2. This invention incorporates a thermal surplus management and dual-mode modulation module, which can automatically switch between steady-state filtering mode and grid transient mode based on the DC bus voltage change rate and grid frequency status. Under transient high-power output conditions, the system automatically reduces the carrier frequency and adopts a discontinuous pulse width modulation algorithm, thereby reducing the switching losses and temperature rise of the power devices in the energy storage converter, preventing overheating of the devices, and improving the survivability and operational reliability of the equipment under extreme conditions such as grid faults or load changes.

[0020] 3. This invention integrates active damping control logic and active ripple suppression algorithm. It utilizes the energy storage converter to generate damping power that is opposite to the torsional vibration of the transmission chain, thereby suppressing the shaft torsional vibration of the wind turbine and reducing mechanical wear and fatigue damage. At the same time, during steady-state operation, it actively outputs compensation current to suppress DC bus voltage ripple, reducing the heating and voltage stress of the thin film capacitor bank, thus synergistically extending the service life of the unit's mechanical components and key electrical components. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the system structure of the present invention; Figure 2 This is a schematic diagram of the internal functional module structure of the network collaborative control unit of the present invention; Figure 3 This is a flowchart illustrating the dual-mode modulation control method based on thermal surplus redistribution of the present invention. Figure 4 This is a schematic flowchart of the rotor kinetic energy coordination and active damping protection method of the present invention; Figure 5This is a flowchart illustrating the quantitative configuration method of the energy storage system of the present invention.

[0022] Among them, 100 is the wind energy capture and conversion unit; 101 is the wind turbine; 102 is the generator; 103 is the generator-side converter; 104 is the grid-side converter; 200 is the DC bus transmission unit; 201 is the thin-film capacitor bank; 300 is the grid-type energy storage subsystem; 301 is the energy storage battery unit; 302 is the energy storage converter; 400 is the grid-based collaborative control unit; 401 is the state perception and mode discrimination module; 402 is the thermal surplus management and dual-mode modulation module; 402a is the switching frequency dynamic reconstruction unit; 402b is the modulation strategy switching unit; 403 is the frequency domain energy collaborative distribution module; and 500 is the power grid. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] See attached document Figure 1 The present invention provides an energy storage enhanced wind turbine system with grid-building capability, comprising: a wind energy capture and conversion unit 100, a DC bus transmission unit 200, a grid-building energy storage subsystem 300, and a grid-building collaborative control unit 400.

[0025] The wind energy capture and conversion unit 100 is used to convert wind energy into electrical energy and feed it into the power grid. The wind energy capture and conversion unit 100 includes a wind turbine 101, a generator 102, a generator-side converter 103, and a grid-side converter 104. The wind turbine 101 is mechanically connected to the rotor of the generator 102 via a mechanical drive shaft, and the stator winding of the generator 102 is electrically connected to the AC side of the generator-side converter 103. The generator-side converter 103 controls the torque and flux of the generator 102 and converts the AC power generated by the generator 102 into DC power. The AC side of the grid-side converter 104 is connected to the power grid 500 to convert the DC power into AC power that meets grid connection standards. The DC side of the generator-side converter 103 and the DC side of the grid-side converter 104 are connected via a DC bus transmission unit 200.

[0026] The DC bus transmission unit 200 serves as the hub node for energy exchange within the system, with its positive and negative terminals connected to the DC ports of the machine-side converter 103 and the grid-side converter 104, respectively. The DC bus transmission unit 200 includes a film capacitor bank 201. The film capacitor bank 201 is composed of multiple metallized film capacitors connected in parallel or series, replacing electrolytic capacitors. The film capacitor bank 201 is connected across the positive and negative terminals of the DC bus to support the instantaneous value of the DC bus voltage. It also absorbs high-frequency switching ripple.

[0027] Due to the use of the thin-film capacitor bank 201, the DC bus transmission unit 200 has a lower equivalent capacitance value. The dynamic characteristics of the system's DC voltage follow the power balance equation, which describes the physical relationship between the rate of change of the DC bus voltage and the power flow in each branch: ; In this formula, This represents the equivalent capacitance value of the thin-film capacitor bank 201; This represents the instantaneous value of the DC bus voltage; This represents the rate of change of DC bus voltage over time. This indicates the active power injected into the DC bus by the machine-side converter 103; This indicates the active power output from the DC bus to the grid 500 by the grid-side converter 104; This represents the active power absorbed by the grid-type energy storage subsystem 300 from the DC bus (energy absorbed from the DC bus is defined as positive). When the grid-type energy storage subsystem 300 releases energy to the DC bus... It is a negative value.

[0028] The grid-type energy storage subsystem 300 includes energy storage battery units 301 and energy storage converters 302. The energy storage battery units 301 are composed of several electrochemical battery cells connected in series and parallel, serving as the system's energy buffer. The energy storage converter 302 is a bidirectional DC / DC converter, with one end connected to the energy storage battery units 301 and the other end directly connected in parallel to the positive and negative terminals of the DC bus transmission unit 200. The energy storage converter 302 includes power semiconductor switching devices and energy storage inductors. By controlling the on and off states of the power semiconductor switching devices, bidirectional energy flow between the energy storage battery units 301 and the DC bus transmission unit 200 is achieved. The selection of the power semiconductor switching devices in the energy storage converter 302 must meet preset high-frequency switching operation requirements to support operation at different modulation frequencies.

[0029] The grid-connected control unit 400 establishes communication connections with the generator-side converter 103, the grid-side converter 104, and the energy storage converter 302 via signal transmission lines. The grid-connected control unit 400 is equipped with a voltage acquisition module for real-time acquisition of the instantaneous voltage values ​​across the DC bus transmission unit 200. The grid coordination control unit 400 is also equipped with a frequency acquisition module for acquiring frequency signals from the power grid 500. Based on the acquired status signals, the grid coordination control unit 400 sends torque control commands to the generator-side converter 103, reactive power control commands to the grid-side converter 104, and carrier frequency commands, modulation mode commands, and current reference commands to the energy storage converter 302 to coordinate the power output of each component.

[0030] See attached document Figure 2 The network construction and coordination control unit 400 is the central coordination unit of this invention, used to achieve stable operation of the system and network construction support under different working conditions.

[0031] The hardware carrier of the grid-based collaborative control unit 400 can be a digital signal processor, a field-programmable gate array (FPGA), or a combination thereof. The grid-based collaborative control unit 400 receives measurement signals from external sensors through multiple input ports and sends control commands to the converters within the wind energy capture and conversion unit 100 and the grid-based energy storage subsystem 300 through multiple output ports. The signals received at the input ports include the instantaneous voltage values ​​across the DC bus transmission unit 200. The voltage and current waveforms of the power grid 500, and the generator speed signal fed back by the generator-side converter 103.

[0032] The network collaborative control unit 400 is logically divided into multiple collaborative functional modules to perform specific control tasks. These functional modules include: a state perception and mode discrimination module 401, a thermal surplus management and dual-mode modulation module 402, and a frequency domain energy collaborative allocation module 403.

[0033] The state awareness and mode discrimination module 401 is used to assess the system's operating environment in real time and decide the operating mode the system should enter. Internally, the state awareness and mode discrimination module 401 includes a differential operation unit and a comparison unit. The differential operation unit receives continuously acquired DC bus voltage data. The signal is analyzed, and its rate of change over time is calculated. .

[0034] The comparator unit will calculate the absolute value of the voltage change rate. With a preset voltage dynamic threshold The comparison unit also compares the received power grid frequency signal with a preset frequency stability range.

[0035] when Less than Furthermore, when the grid frequency is within a stable range, the state perception and mode discrimination module 401 outputs a steady-state filtering mode flag; conversely, when... Greater than or equal to When the grid frequency exceeds the stable range, the state perception and mode discrimination module 401 outputs a network transient mode flag. This mode flag signal is transmitted to the thermal surplus management and dual-mode modulation module 402.

[0036] The thermal surplus management and dual-mode modulation module 402 is the core control module of this invention, used to directly generate the underlying drive signals of the energy storage converter 302. The thermal surplus management and dual-mode modulation module 402 receives the mode flag signal from the state perception and mode discrimination module 401, and adjusts the switching frequency and modulation strategy of the energy storage converter 302 accordingly.

[0037] The thermal surplus management and dual-mode modulation module 402 is further divided into a switching frequency dynamic reconstruction unit 402a and a modulation strategy switching unit 402b. The switching frequency dynamic reconstruction unit 402a is equipped with a frequency lookup table that stores at least two switching frequency values: one high-frequency value... and a low frequency value When the steady-state filtering mode flag is received, the switching frequency dynamic reconstruction unit 402a selects from the lookup table. The carrier frequency command is used as the energy storage converter 302; when the network transient mode flag is received, the following is selected: .

[0038] The modulation strategy switching unit 402b switches between the space vector pulse width modulation (SVM) algorithm and the discontinuous pulse width modulation (DPWM) algorithm based on the mode flag signal. When in steady-state filtering mode, this unit activates the SVM algorithm; when in network transient mode, it activates the DPWM algorithm. The thermal surplus management and dual-mode modulation module 402 packages the generated carrier frequency command with the relevant parameters required for the selected modulation algorithm and sends it to the underlying drive controller of the energy storage converter 302.

[0039] To ensure a smooth and uninterrupted mode switching process, the thermal surplus management and dual-mode modulation module 402 is also equipped with synchronous switching logic. This logic ensures that the change in switching frequency and the switching of modulation strategy are executed synchronously at the boundary of a pulse width modulation cycle. Specifically, the new carrier frequency value and modulation mode parameters are pre-loaded into the shadow register of the underlying drive controller of the energy storage converter 302, and are simultaneously updated through an atomic operation when the current pulse width modulation cycle counter returns to zero, thereby avoiding incomplete pulse width modulation pulses or temporary control logic conflicts at the moment of switching.

[0040] The frequency domain energy collaborative allocation module 403 is used to decompose the top-level grid power demand into specific power commands based on the response characteristics of different energy sources. The frequency domain energy collaborative allocation module 403 receives the total grid power reference value of the system and is configured with a digital filter bank that decomposes the power reference value into high-frequency and low-frequency components. The high-frequency component is directly used as the instantaneous power command of the energy storage converter 302 to utilize its fast electrical response capability.

[0041] The low-frequency components are smoothly converted into torque commands for the generator-side converter 103 via a ramp function generator to mobilize the rotational kinetic energy of the wind turbine 101. Furthermore, the frequency domain energy collaborative distribution module 403 integrates active damping control logic. This logic analyzes the spectrum of the generator speed signal, extracts the torsional vibration frequency component of the transmission chain, and calculates a damping power signal that is in the same frequency but out of phase with the torsional vibration frequency. This damping power signal is superimposed on the high-frequency power command of the energy storage converter 302, indirectly achieving electrical suppression of mechanical torsional vibration by generating controlled power fluctuations on the DC bus.

[0042] See attached document Figure 3 This embodiment details how the network collaborative control unit 400 switches between steady-state filtering and transient network construction modes by dynamically adjusting the underlying drive logic of the energy storage converter 302, so as to achieve the optimal configuration of system performance.

[0043] This method is managed by a state machine that defines two core operating states: steady-state filtering mode and grid construction transient mode. The state machine transitions states based on the mode flag signal output by the state perception and mode discrimination module 401. After system initialization or after a grid disturbance, the state machine defaults to steady-state filtering mode. When the mode flag signal switches from steady state to transient state, the state machine transitions to grid construction transient mode; when the mode flag signal recovers from transient state to steady state, the state machine reverts to steady-state filtering mode.

[0044] In steady-state filtering mode, the primary task of the energy storage converter 302 is to act as an active power filter, actively suppressing the DC bus voltage ripple caused by the use of the thin-film capacitor bank 201. In this mode, the thermal surplus management and dual-mode modulation module 402 performs the following specific operations: First, the switching frequency dynamic reconstruction unit 402a sends high-frequency values ​​to the energy storage converter 302. Secondly, the modulation strategy switching unit 402b activates the space vector pulse width modulation algorithm.

[0045] Simultaneously, an active ripple suppression algorithm is activated, which uses a bandpass filter to detect the instantaneous value of the DC bus voltage. The algorithm extracts a ripple component of a specific frequency from the measured values, which is typically twice the fundamental frequency of the power grid. Based on the extracted ripple voltage amplitude and phase, the algorithm calculates an inverse compensation current reference value. This compensation current reference value is then superimposed on the total current command of the energy storage converter 302.

[0046] Under high-frequency space vector pulse width modulation, the energy storage converter 302 follows the composite current command, injecting or absorbing small, high-frequency compensation currents into or from the DC bus to offset voltage ripple and maintain DC bus voltage stability. Furthermore, this active ripple suppression algorithm also includes an adaptive gain adjustment stage. This stage adjusts the gain based on the instantaneous value of the DC bus voltage. The control gain of the compensation current is adjusted to appropriately reduce when the bus voltage rises. This is to prevent the ripple suppression function from consuming unnecessary energy storage due to overcompensation when the wind turbine is operating at high power and the bus voltage rises naturally, thereby optimizing the overall energy management efficiency of the system while ensuring the basic filtering effect.

[0047] When the state machine transitions to the grid-supported transient mode, the system's control objective shifts from maintaining voltage quality to maximizing the grid-supported power output. At this time, the thermal surplus management and dual-mode modulation module 402 executes a series of resource reallocation operations to unlock the potential capabilities of the power semiconductor devices. The specific operation steps are as follows: The first step is to reduce switching losses. The switching frequency dynamic reconfiguration unit 402a immediately changes the switching frequency command of the energy storage converter 302 from... Switch to low switching frequency Since the switching losses of power semiconductor devices are approximately proportional to the switching frequency, this operation reduces the heat generated by the device, thereby creating a thermal surplus that can be used to conduct larger fundamental currents within the safe junction temperature limit of the device.

[0048] The second step is to reconstruct the modulation strategy to reuse the dead time. The modulation strategy switching unit 402b switches the modulation algorithm from space vector pulse width modulation to discontinuous pulse width modulation. In the discontinuous pulse width modulation algorithm, by injecting a specially calculated zero-sequence component into the three-phase sinusoidal modulation wave, it is possible to clamp one phase of the modulation wave onto the envelope of the positive or negative DC bus voltage within each one-third cycle (120 degrees) of the three-phase modulation wave.

[0049] The power semiconductor devices on the clamped bridge arm will remain in a constant on or off state, without performing high-frequency switching operations. Therefore, the switching losses of this phase are completely eliminated, further increasing thermal margin. Simultaneously, since there is no switching on this phase, there is no need to set a dead time for it. This reused dead time increases the effective duration of the voltage output, improving DC voltage utilization.

[0050] The third step is to release overload current. The frequency domain energy collaborative allocation module 403 converts the instantaneous grid support power command required by the system into the fundamental current reference value of the energy storage converter 302. Since the first two steps have created sufficient thermal margin for the power devices, the energy storage converter 302 can safely conduct a fundamental current much larger than its rated value, thereby achieving short-term overload operation and providing strong active or reactive power support to the grid. During this period, the original active ripple suppression algorithm is temporarily disabled or its control gain is significantly reduced, allowing the DC bus voltage to have a certain ripple fluctuation within a safe range, to ensure that all control resources are concentrated on the grid support task.

[0051] See attached document Figure 4 This embodiment details how the grid-connected collaborative control unit 400 schedules the rotating components in the wind energy capture and conversion unit 100 to coordinate with the grid-connected energy storage subsystem 300 in order to achieve efficient and safe grid-connected power support.

[0052] The core of this method lies in the time-scale decomposition of the total grid-connected power reference command through the frequency-domain energy collaborative allocation module 403. In the initial stage of the grid connection event, i.e., within a millisecond timescale, the instantaneous power support required by the grid (i.e., virtual inertia response) is entirely provided by the grid-connected energy storage subsystem 300. This is because the energy storage converter 302, as a pure power electronic device, possesses extremely fast electrical response speed and can instantly respond to the high-frequency power command issued by the frequency-domain energy collaborative allocation module 403.

[0053] As time progresses and the timescale reaches the second level, the system needs to provide continuous power support to stabilize the grid frequency (i.e., primary frequency regulation response). At this point, the frequency domain energy collaborative allocation module 403 activates the rotor kinetic energy collaborative mechanism. This module smoothly converts the low-frequency component in the grid power reference command into an electromagnetic torque increment command for the generator-side converter 103 through a ramp function processor. Upon receiving this command, the generator-side converter 103 increases the electromagnetic torque of the generator.

[0054] According to the rotational form of Newton's second law, when the electromagnetic torque exceeds the mechanical torque of the wind turbine 101, the rotational speeds of the generator 102 and the wind turbine 101 will decrease. This decrease in speed causes the entire rotating component (including the wind turbine blades and the generator rotor) to release its stored rotational kinetic energy. This released kinetic energy is converted into electrical energy by the generator 102 and the machine-side converter 103, and injected into the DC bus transmission unit 200, thus replacing the energy storage system as the primary power source for primary frequency regulation.

[0055] By using this relay method of storing energy first and then rotating it, both the speed of energy storage and the huge kinetic energy reserve of the wind turbine are utilized, avoiding the rapid depletion of the energy storage system due to long-term high-power discharge.

[0056] During the aforementioned rotor kinetic energy release process, the step change in electromagnetic torque excites torsional vibration in the transmission chain between the wind turbine 101 and the generator 102. To suppress this harmful oscillation, the active damping control logic integrated within the frequency domain energy collaborative distribution module 403 is activated. This logic first identifies the dominant frequency of the transmission chain torsional vibration online by performing a fast Fourier transform on the generator speed signal or using a bandpass filter. Subsequently, the logic generates a damping power reference signal with the same torsional vibration frequency but with its phase precisely adjusted (typically out of phase or 90 degrees ahead).

[0057] The unique feature of this damped power reference signal is that it is superimposed on the high-frequency power command of the grid-type energy storage subsystem 300, rather than acting directly on the generator-side converter 103. Based on the superimposed command, the energy storage converter 302 generates a controlled, small power fluctuation at the same frequency as the torsional vibration on the DC bus transmission unit 200. Because the generator-side converter 103, the DC bus transmission unit 200, and the grid-side converter 104 are electrically tightly coupled, the power fluctuation on the DC side instantaneously affects the power balance of the generator-side converter 103, thereby generating an electromagnetic torque pulsation in the air gap of the generator 102 that is opposite to the torsional vibration.

[0058] The electrically generated damping torque effectively counteracts mechanical torsional vibrations, providing active, non-contact protection for the transmission chain and ensuring the mechanical safety of the system during grid construction. To prevent conflicts between active damping control and primary frequency regulation power commands, the damping power reference signal passes through an energy neutralization unit before injection. This unit ensures that the average value of the injected damping power signal is zero over one or more complete oscillation cycles. This means that active damping control only performs high-frequency energy throughput exchange on the DC bus without generating additional net power injection or absorption, thus ensuring that the protection function does not interfere with the macroscopic power regulation tasks performed by the system in response to the grid frequency.

[0059] See attached document Figure 5 This embodiment provides a systematic design method for determining the key parameters of the grid-type energy storage subsystem 300, namely the rated power and rated capacity, to ensure that the subsystem can effectively perform its grid-building and collaborative support functions under all preset operating conditions.

[0060] This configuration method begins with the power dimension. The rated power of the energy storage converter 302... It is necessary to meet the maximum instantaneous imbalance between the wind turbine's own power and the grid's power demand under the most severe operating conditions. This maximum imbalance occurs in various scenarios, such as a sudden drop in wind speed causing a sharp decrease in turbine output while the grid requires additional power support due to load input. Therefore, the first step in power configuration is to analyze the available power curves of the wind turbine under different wind speeds. Maximum power request from the power grid The rated power of energy storage converter 302 The configuration should be greater than or equal to the historical maximum or design extreme value of the absolute value of the difference between the two. This design principle ensures that the energy storage system is capable of filling or absorbing the largest power gap at any time, serving as the first line of defense for system power balance.

[0061] After determining the rated power, this configuration method moves on to the capacity dimension design. The rated capacity of energy storage battery cell 301... The configuration depends primarily on the time required to independently support network construction tasks. This support time This is a key design parameter, defined as the time window from the start of the grid connection event until the rotational kinetic energy of the wind turbine rotor can be effectively mobilized and completely replace the output power of the energy storage system. The length of this time window is determined by the mechanical inertia of the wind turbine, the response delay of the control system, and the ramp rate of the primary frequency regulation.

[0062] The rated power was determined. and support time Then, the net energy output required by the energy storage battery unit 301 can be obtained by multiplying the two. However, in practical configurations, losses during the energy conversion process and operational constraints set to extend battery life must be considered. Therefore, the rated capacity... The calculation requires incorporating the round-trip efficiency of the energy storage system. and the battery's maximum permissible depth of discharge Round-trip efficiency This represents the energy loss throughout the entire process of energy being released from the battery, converted by the energy storage converter 302, and then delivered to the DC bus. Maximum permissible depth of discharge. It is a percentage value used to limit the discharge range of the battery and avoid irreversible damage to the battery life due to over-discharge.

[0063] Taking all the above factors into account, the rated capacity of energy storage battery unit 301 is... The calculation is performed using the following logic: First, calculate the total energy required during the support time, which is the product of the rated power and the support time; then, divide this energy value by the round-trip efficiency. This is done to compensate for conversion losses; finally, the result is divided by the maximum permissible depth of discharge. This ensures that even after completing a full support task, the battery's state of charge remains within a healthy and safe range. Energy storage systems configured in this way meet the power and energy requirements of grid construction while also ensuring system economy and long-term operational reliability.

Claims

1. A wind turbine system with grid-connected capability and enhanced energy storage, characterized in that, include: A wind energy capture and conversion unit is configured to convert wind energy into electrical energy and feed it into the power grid, and includes a wind turbine, a generator, a machine-side converter, and a grid-side converter; The wind turbine is mechanically connected to the rotor of the generator, and the stator winding of the generator is electrically connected to the AC side of the generator-side converter. The generator-side converter is used to control the torque and magnetic flux of the generator, and to convert the alternating current generated by the generator into direct current. The AC side of the grid-side converter is connected to the power grid. A DC bus transmission unit is connected between the DC side of the turbine-side converter and the DC side of the grid-side converter, serving as a hub node for energy exchange within the energy storage-enhanced wind turbine system with grid-connected capability. The positive and negative terminals of the DC bus transmission unit are respectively connected to the DC ports of the turbine-side converter and the grid-side converter. A grid-type energy storage subsystem includes energy storage battery units and energy storage converters; One end of the energy storage converter is connected to the energy storage battery unit, and the other end of the energy storage converter is connected in parallel to the positive and negative terminals of the DC bus transmission unit. The grid-connected control unit establishes communication connections with the machine-side converter, the grid-side converter, and the energy storage converter respectively through signal transmission lines; The grid-connected control unit is equipped with a voltage acquisition module and a frequency acquisition module, configured to send torque control commands to the generator-side converter, reactive power control commands to the grid-side converter, and carrier frequency commands, modulation mode commands, and current reference commands to the energy storage converter, thereby achieving coordinated power output.

2. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 1, characterized in that, The DC bus transmission unit includes a thin-film capacitor bank, which consists of multiple metallized thin-film capacitors. The thin-film capacitor bank is connected between the positive and negative terminals of the DC bus transmission unit and is configured to support the DC bus voltage and absorb high-frequency switching ripple.

3. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 1, characterized in that, The network collaborative control unit is internally divided into a state perception and mode discrimination module, a thermal surplus management and dual-mode modulation module, and a frequency domain energy collaborative allocation module. The state perception and pattern discrimination module is configured to evaluate the operating environment and output a pattern flag signal; The thermal surplus management and dual-mode modulation module is configured to receive the mode flag signal and generate the carrier frequency command and the modulation mode command of the energy storage converter. The frequency domain energy collaborative allocation module is configured to decompose the grid power reference value into the instantaneous power command of the energy storage converter and the torque control command of the machine-side converter.

4. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 3, characterized in that, The state perception and pattern discrimination module includes a differential operation unit and a comparison unit; The differential operation unit is configured to receive the DC bus voltage signal and calculate the rate of change of the DC bus voltage over time; The comparison unit is configured to compare the absolute value of the rate of change with a preset voltage dynamic threshold and to compare the power grid frequency signal with a preset frequency stability range. When the absolute value of the rate of change is less than the voltage dynamic threshold and the power grid frequency is within the frequency stability range, the state perception and mode discrimination module outputs a steady-state filtering mode flag. When the absolute value of the rate of change is greater than or equal to the voltage dynamic threshold, or when the grid frequency exceeds the frequency stability range, the state perception and mode discrimination module outputs a grid transient mode flag.

5. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 4, characterized in that, The thermal surplus management and dual-mode modulation module includes a switching frequency dynamic reconstruction unit and a modulation strategy switching unit; The switching frequency dynamic reconstruction unit is configured with a frequency lookup table, which stores high-frequency values ​​and low-frequency values. Upon receiving the steady-state filtering mode flag, the switching frequency dynamic reconstruction unit selects the high-frequency value as the carrier frequency command; Upon receiving the network transient mode flag, the switching frequency dynamic reconstruction unit selects the low-frequency value as the carrier frequency command; The modulation strategy switching unit is configured to switch between a space vector pulse width modulation algorithm and a discontinuous pulse width modulation algorithm; When in the steady-state filtering mode, the modulation strategy switching unit activates the space vector pulse width modulation algorithm; When in the network transient mode, the modulation strategy switching unit activates the discontinuous pulse width modulation algorithm.

6. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 5, characterized in that, The thermal surplus management and dual-mode modulation module is configured with synchronous switching logic. The synchronous switching logic is configured to preload the new carrier frequency command and modulation mode parameters into the shadow register of the energy storage converter, and update them simultaneously through atomic operations when the current pulse width modulation period counter returns to zero.

7. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 3, characterized in that, The frequency domain energy collaborative allocation module is equipped with a digital filter bank and a ramp function generator; The digital filter bank is configured to decompose the network power reference value into high-frequency components and low-frequency components; The high-frequency component serves as the instantaneous power command of the energy storage converter; The low-frequency component is converted into the torque control command of the machine-side converter by the ramp function generator.

8. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 7, characterized in that, The frequency domain energy collaborative allocation module integrates active damping control logic; The active damping control logic is configured to analyze the spectrum of the generator speed signal and extract the torsional vibration frequency component of the transmission chain, and calculate the damping power signal that is in the same frequency but opposite in phase with the torsional vibration frequency. The damping power signal is superimposed on the high-frequency component of the energy storage converter.

9. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 8, characterized in that, The damping power signal passes through an energy neutralization processing unit before being superimposed. The energy neutralization processing unit is configured to ensure that the average value of the damping power signal is zero over a complete oscillation cycle.

10. The energy storage-enhanced wind turbine system with grid-connection capability according to claim 5, characterized in that, In the steady-state filtering mode, the network collaborative control unit activates the active ripple suppression algorithm; The active ripple suppression algorithm is configured to extract the ripple component from the measured value of the DC bus voltage, calculate the inverse compensation current reference value, and superimpose the compensation current reference value into the total current command of the energy storage converter, so that the energy storage converter outputs compensation current and suppresses the DC bus voltage ripple.

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