Wind storage joint black-start method and system fusing coupling item and improved virtual synchronization

Abstract

The invention discloses a wind storage joint black-start method and system fusing coupling terms and improved virtual synchronization, and belongs to the technical field of black-start power supply control. A control signal is determined by introducing a V / F control strategy of a coupling term and is output to a battery energy storage unit, and the battery energy storage unit is used for providing excitation for the doubly-fed asynchronous wind generating set to realize self-starting of the doubly-fed asynchronous wind generating set; an improved virtual synchronous control strategy is adopted to control a rotor side converter, the doubly-fed asynchronous wind generating set is connected into a power grid, and the doubly-fed asynchronous wind generating set which is successfully connected with the power grid is utilized to start remaining wind power plant units; and switching the V / F control strategy introduced with the coupling item into the P / Q control strategy introduced with the coupling item, and starting the thermal power generating unit. Through coupling item control, cooperation and flexible switching of a virtual synchronization strategy are improved, wind storage combined black start is efficiently achieved, stable grid connection and efficient power grid recovery are guaranteed, and the method adapts to a new energy scene.

Description

Technical Field

[0001] This invention relates to the field of black-start power supply control technology, and in particular to a wind-storage combined black-start method and system that integrates coupling terms and improved virtual synchronization. Background Technology

[0002] Black start is a key technology for restoring power supply through a self-contained starting power source when there is no external power source after a major power grid outage. Its core requirement is that the starting power source can stably provide power, establish and maintain grid voltage and frequency, and lay the foundation for the subsequent start-up of generating units.

[0003] With the high proportion of new energy sources being integrated, wind-storage combined systems are gradually becoming an important choice for black-start power sources due to their cleanliness and efficiency. They are expected to solve the problem of wind power volatility by relying on energy storage, and can also achieve stable power supply through coordinated control, which meets the development needs of new power systems.

[0004] However, existing wind-storage combined black-start solutions still have significant technical shortcomings: wind power itself has strong volatility and uncertainty, and traditional doubly-fed asynchronous wind turbines cannot start on their own, requiring energy storage devices to provide excitation and DC voltage support. However, existing research mainly focuses on wind-storage combination to suppress power fluctuations, without optimizing for the high-precision voltage and frequency control requirements of black-start scenarios. At the same time, traditional doubly-fed wind turbines use vector control strategies, exhibiting current source characteristics, which are difficult to bear the voltage and frequency support required for black-start. In addition, traditional V / F control has cross-coupling effects in the dq rotating coordinate system, resulting in insufficient dynamic response and control accuracy. Virtual synchronous control, due to the lack of a current inner loop, cannot suppress transient inrush currents, which can easily lead to equipment safety issues, seriously restricting the black-start reliability of wind-storage combined systems. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a wind-storage combined black start method and system that integrates coupling terms and improved virtual synchronization. At different stages of black start, the battery energy storage unit and the doubly-fed asynchronous wind turbine should adopt different control strategies according to the actual situation to maintain the frequency and voltage stability of the system, efficiently realize the wind-storage combined black start, ensure smooth grid connection and efficient grid recovery, and adapt to new energy scenarios.

[0006] In a first aspect, the present invention provides a wind-storage joint black start method that integrates coupling terms and improved virtual synchronization, comprising: The control signal is determined by introducing a V / F control strategy with coupling terms and output to the battery energy storage unit. The battery energy storage unit is then used to provide excitation for the doubly-fed asynchronous wind turbine generator to achieve its self-starting. An improved virtual synchronous control strategy is adopted to control the rotor-side converter, and the doubly-fed asynchronous wind turbine generators are connected to the grid. The remaining wind farm units are started using the successfully connected doubly-fed asynchronous wind turbine generators. Switch the V / F control strategy that introduces coupling terms to the P / Q control strategy that introduces coupling terms, and start the thermal power unit; Among them, the improved virtual synchronous control strategy combines the flux linkage equation and the voltage equation to construct the voltage control equation, and introduces virtual impedance to make up for the gap in the current control inner loop.

[0007] In some embodiments, the improved virtual synchronous control strategy for controlling the rotor-side converter further includes frequency control of the rotor-side converter based on the virtual rotation equation, damping equation, and slip angular frequency of the doubly-fed asynchronous wind turbine. The specific process is as follows: Based on the deviation between the actual angular frequency and the rated frequency, and the active power reference value, the slip angular frequency reference value is calculated using the virtual rotation equation. Based on the damping equation and the damping coefficient, the magnitude of the damping power is determined to suppress frequency oscillations; The slip angular frequency reference value and damping power are fed back to the control system of the rotor-side converter. The control system adjusts the output of the rotor-side converter in real time according to the parameters to achieve frequency control of the doubly-fed asynchronous wind turbine.

[0008] In some implementations, the P / Q control strategy that introduces coupling terms includes: The power reference signal and active power of the battery energy storage unit are acquired and PI control is performed to generate... dq Shaft current reference signal; Obtain the actual current value, for dq The shaft current reference signal and the actual current value are used for PI control. A coupling term is introduced to generate a voltage signal and perform PWM modulation to obtain the converter control signal.

[0009] In some implementations, the V / F control strategy that introduces coupling terms includes: The d-axis voltage reference value, d-axis voltage value, q-axis voltage reference value, and q-axis actual value output by the battery energy storage unit are obtained and PI control is performed. Combined with the first coupling term, the current control signal is determined. The d-axis and q-axis current values ​​output by the battery energy storage unit are obtained, and PI control is performed in conjunction with the current control signal. A second coupling term is introduced to determine the voltage control signal, which is then modulated by PWM to generate the control signal.

[0010] In some implementations, the construction of the voltage control equation by combining the flux linkage equation and the voltage equation specifically involves: utilizing a doubly-fed asynchronous wind turbine... dq The flux linkage equation and voltage equation in the coordinate system are used to obtain the control relationship between the stator voltage and the rotor voltage, and the control equation of the rotor voltage after processing by the PI controller is determined.

[0011] In some implementations, the governing equations are expressed as: ; ; In the formula, Indicates the stator voltage reference value. This represents the actual measured value. This represents the proportionality coefficient. Indicates the integral coefficient; For the self-sensing of the stator, For rotor self-inductance, For mutual inductance between stator and rotor, This term reflects the degree of magnetic flux coupling between the stator and rotor. This item reflects stator current disturbances in real time. Let ω be the slip angular velocity, and j be the imaginary part.

[0012] In some implementations, the introduction of virtual impedance to compensate for the gap in the current control inner loop specifically refers to: ; in, This represents the actual value of the output excitation voltage of the rotor-side converter. This represents the actual value of the output excitation voltage of the rotor-side converter. This indicates the output current value of the rotor-side converter. This represents virtual impedance.

[0013] Secondly, this invention provides a wind-storage joint black-start system that integrates coupling terms and improved virtual synchronization, comprising: Doubly fed asynchronous wind turbine generator sets are connected to the grid side through rotor-side converters and grid-side converters, and are used to supply power to the grid and start other units after grid connection; The battery energy storage unit, whose AC side is connected to the outlet of the doubly fed asynchronous wind turbine generator set or the grid bus via a three-phase inverter, is used to establish grid voltage and frequency in the early stage of black start, thereby providing excitation conditions for the doubly fed asynchronous wind turbine generator set and providing support for the grid in the subsequent stage. It also includes a first controller and a second controller; the first controller is configured to execute a V / F control strategy and a P / Q control strategy that introduce coupling terms, and its output is connected to the three-phase inverter. It is used to establish and maintain a stable bus voltage and frequency through V / F control in the initial stage of startup, and to switch to P / Q control in the subsequent stage to adjust the grid-connected power; the second controller is built into the rotor-side converter and is configured to execute an improved virtual synchronous machine control strategy. The strategy combines the flux linkage equation and the voltage equation to construct a voltage control equation and introduces a virtual impedance loop. It is used to control the smooth connection of the doubly-fed asynchronous wind turbine generator to the grid after the voltage is established, and to start the other wind turbine generators.

[0014] In some implementations, a reactive power compensator is also included, which is connected to the connection bus between the battery energy storage unit and the power grid to perform reactive power compensation on the electrical energy output by the wind turbine generator, improve the power quality of the wind power output, and reduce voltage fluctuations caused by the volatility of wind power generation.

[0015] Thirdly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the wind-storage joint black-start method for fusion coupling terms and improved virtual synchronization described in the first aspect.

[0016] Compared with the prior art, the beneficial effects of the present invention are: (1) In the initial stage of black start, the battery energy storage unit adopts a V / F control strategy to help establish and maintain the output voltage and frequency to assist the start-up of the doubly-fed asynchronous wind turbine. Subsequently, the doubly-fed asynchronous wind turbine, which adopts an improved virtual synchronous control strategy, begins to undertake the task of maintaining voltage and frequency stability. After the remaining units and loads in the wind farm have started up, the battery energy storage unit switches to a P / Q control strategy, and its task becomes to respond promptly to the power changes when subsequent thermal power units and loads are connected, and to effectively prevent overcharging and discharging of the energy storage system. During the switching of control strategies in the energy storage system, since the doubly-fed asynchronous wind turbine adopts virtual synchronous control, the frequency and voltage fluctuations are limited to a small range and then quickly return to stability. This cooperative control strategy limits the frequency and voltage fluctuations during the black start power supply startup process, as well as the power fluctuations after the units and loads have recovered.

[0017] (2) The present invention charges the grid bus through an external battery energy storage unit. In the early stage of black start, it provides excitation for the doubly fed asynchronous wind turbine that acts as the black start power source, helps to establish the DC bus voltage of the wind turbine, assists the doubly fed asynchronous wind turbine to complete grid connection, and participates in the subsequent black start process.

[0018] (3) The present invention introduces a coupling compensation term in the V / F control strategy to offset the cross-coupling effect caused by the dq rotating coordinate system, making the dynamic response of the control system faster and more accurate. The V / F control strategy is suitable for use in the early stage of black start. When the black start power supply has not yet completed self-starting, the energy storage system can effectively support the system voltage and frequency, providing a stable environment for the subsequent grid connection of the black start power supply and load start-up.

[0019] (4) In view of the problem that traditional new energy generator sets are not strong enough to support the grid frequency and voltage, the present invention modifies the rotor-side converter of the doubly fed asynchronous wind turbine based on the improved virtual synchronous machine technology; by introducing frequency control, voltage control and current limiting links, the grid voltage and frequency are stabilized within the range specified by the project during the black start process, so that it has stronger frequency and voltage support capabilities.

[0020] (5) The present invention connects the battery energy storage unit to the grid bus, realizing functions such as fast response and flexible power configuration. In the later stage of black start, it can maintain the grid power balance, avoid overcharging and discharging, and flexibly adapt to the power changes after the load is restored. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 The main flowchart of a wind-storage joint black start method with fusion coupling terms and improved virtual synchronization provided in an embodiment of the present invention is shown below. Figure 2 A control block diagram of a V / F control strategy with introduced coupling terms provided in an embodiment of the present invention; Figure 3 A control block diagram of an improved virtual synchronization control strategy provided in an embodiment of the present invention; Figure 4 A control block diagram of a P / Q control strategy with introduced coupling terms provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of a wind-storage combined black-start system that integrates coupling terms and improved virtual synchronization, provided as an embodiment of the present invention. Detailed Implementation

[0023] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0024] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0025] Example 1 This embodiment discloses a wind-storage joint black-start method that integrates coupling terms and improved virtual synchronization, such as... Figure 1 As shown, different control strategies are adopted for the battery energy storage unit and the doubly fed asynchronous wind turbine in different stages of black start, in order to maintain the frequency and voltage stability of the system.

[0026] The black-start power supply control method based on the wind-storage integrated system includes the following steps: S1. The control signal is determined by introducing a V / F control strategy with coupling terms and output to the battery energy storage unit. The battery energy storage unit is used to provide excitation for the doubly fed asynchronous wind turbine generator set to achieve its self-starting.

[0027] This step corresponds to the first stage of black-starting the power supply, utilizing the battery energy storage unit to provide excitation for the doubly-fed asynchronous wind turbine generator. During this stage, a V / F control strategy is employed to control the battery energy storage unit, maintaining its output voltage and frequency within a defined range.

[0028] The corresponding structure of the V / F control strategy is shown in the appendix. Figure 2 As shown, the control structure is based on dq The system consists of two cascaded control loops along the coordinate axis, with the outer loop being a voltage control loop and the inner loop being a current control loop. The voltage control loop is configured by... dq The shaft voltage reference value is compared with the actual inverter voltage value and then fed into the PI controller to generate a current control signal. The inner current control loop receives the current control signal and generates a voltage control signal using a similar principle. This voltage control signal is then generated after passing through a PWM modulation stage to produce the converter's control signal. Simultaneously, a frequency reference value is set. To maintain the stability of the system output frequency.

[0029] The specific control process is as follows: 1. Voltage outer loop: Set the d-axis voltage reference value and q-axis voltage reference value The actual output voltage of the inverter , By comparison, the voltage error signal is obtained. and : ; Input the error signal into the PI controller, and output the current reference signal: ; in, U dThis represents the actual value of the d-axis voltage. U q This is the actual value of the q-axis voltage. ΔU d For d-axis voltage error, ΔU q This represents the q-axis voltage error. k p1 This is the voltage loop proportionality coefficient. k i1 The voltage loop integral coefficient, I dref This is the reference value for the d-axis current. I qref This is the reference value for the q-axis current.

[0030] Based on this, the first coupling term is introduced. ωC Coupling compensation is applied to the current reference signal to improve the dynamic response accuracy.

[0031] Specifically, in the voltage outer loop, the first coupling term ωC Used for current reference signal I dref and I qref Perform cross compensation: ωC Multiply by the actual voltage on the q-axis U q Then, with current disturbance I od The current reference signal is superimposed on the d-axis current. I dref In the middle; at the same time, will ωC Multiply by the actual voltage on the d-axis U d Then, with current disturbance I oq They are superimposed on the q-axis current reference signal. I qref This enables dynamic decoupling and compensation of the dq-axis current command, improving the dynamic response accuracy of the voltage loop.

[0032] In the dq rotating coordinate system, the voltages of the d-axis and q-axis are coupled to each other through capacitor C. This causes a voltage change on one axis to interfere with the current command on the other axis, slowing down the voltage loop response. This embodiment introduces a first coupling term. ωC By calculating the cross-coupling amount in real time and injecting it directly into the current reference value as feedforward compensation, the coupling effect is actively counteracted during the command generation stage. In this way, the voltage loop PI controller does not need to handle coupling errors separately, and can adjust the voltage more quickly and accurately, improve dynamic response accuracy, and reduce overshoot and oscillation.

[0033] 2. Inner current loop: The above current reference signal... Idref , I qref With actual output current I d , I q By comparison, the current error signal is obtained. ΔI d and ΔI q : ; After passing through the PI controller, the output modulated voltage signal is: ; in, I d This represents the actual value of the d-axis current. I q This is the actual value of the q-axis current. ΔI d For d-axis current error, ΔI q For q-axis current error, k p2 This is the proportionality coefficient of the current loop. k i2 The integral coefficient of the current loop is... U md The voltage is modulated along the d-axis. U mq This is the q-axis modulation voltage.

[0034] Based on this, a second coupling term is introduced. ωL This further counteracts the coupling effect between the d and q axes, improving control accuracy.

[0035] Specifically, in the inner current loop, the second coupling term ωL Further analysis of the modulated voltage signal U md and U mq Perform decoupling: ωL Multiply by the actual voltage on the q-axis I q Then, with voltage disturbance amount U od The current reference signal is superimposed on the d-axis current. U md In the middle; at the same time, will ωL Multiply by the actual voltage on the d-axis I d Then, with voltage disturbance amount U oq They are superimposed on the q-axis current reference signal. U mqIn order to counteract the coupling effect between the d and q axes, the accuracy of current tracking and system stability are enhanced.

[0036] In the inner current loop, the inductor L causes the dq-axis currents to couple. A change in the current on one axis will induce a voltage on the other axis, interfering with current tracking. This embodiment introduces a second coupling term. ωL By calculating the coupling voltage and feeding it forward into the modulation voltage, the inductive coupling effect is directly canceled out. This allows the current loop to track the decoupled current command more accurately, reducing dynamic tracking error and mitigating the risk of oscillation caused by coupling, thereby enhancing system stability and control accuracy.

[0037] 3. PWM modulation stage: modulates the voltage signal. U md , U mq The signal is converted to a stationary coordinate system via Park inverse transform, and then modulated using SPWM or SVPWM to generate the switching signal for the converter, controlling the output voltage and frequency of the battery energy storage unit. Specifically, the PWM modulation generates a converter control signal, which is directly output to the inverter module of the power conversion system (PCS) within the battery energy storage unit. This signal controls the on / off switching of IGBTs and other switching devices, adjusting the amplitude, frequency, and phase of the AC voltage output by the energy storage system. The battery energy storage unit outputs a stable three-phase AC voltage through the PCS, which is then stepped up by a transformer and connected to the grid bus at the wind turbine's output. This voltage provides excitation current to the stator windings of the doubly-fed asynchronous wind turbine, helping to establish the air gap magnetic field, which in turn induces a voltage in the turbine's rotor windings, completing the wind turbine's self-starting process.

[0038] This control strategy introduces a coupling compensation term based on traditional V / F control. ωL and ωC Effectively offset dq The cross-coupling effect in the rotating coordinate system improves the system's dynamic response speed and control accuracy, making it particularly suitable for the high-precision voltage and frequency support requirements during the initial black start phase. This control strategy is applicable during the initial black start phase when the power supply has not yet completed self-starting, providing support for voltage and frequency.

[0039] S2. An improved virtual synchronous control strategy is adopted to control the rotor-side converter, connecting the doubly-fed asynchronous wind turbine generator set to the grid, and using the successfully connected doubly-fed asynchronous wind turbine generator set to start the remaining wind farm units. For example... Figure 3 As shown, it specifically includes: S201. Frequency control of the rotor-side converter is performed based on the virtual rotation equation, damping equation, and slip angular frequency of the doubly fed asynchronous wind turbine.

[0040] The main function of frequency control in this step is to maintain frequency stability.

[0041] The virtual rotation equation is expressed as: ; The damping equation is expressed as: ; The slip angular frequency is expressed as: ; In the formula, Indicates the slip angular frequency. , ω Indicates the angular frequency of the internal potential. ω r Indicates the reference angular frequency; Indicates the actual angular frequency. ω N Indicates the rated frequency. m This represents the droop coefficient, which reflects the effect of frequency droop adjustment. P ref It is a reference value for active power. P m For virtual mechanical power, P D For damping power, D The damping coefficient is... This is the virtual inertia coefficient.

[0042] Furthermore, S201 specifically refers to: 1. Input the actual angular frequency measured by the system in real time. ω System rated operating angular frequency ω N , set active power reference value P ref and droop coefficient m .

[0043] 2. Process the input: Calculate the frequency deviation. Based on the virtual rotation equation and parameters such as frequency deviation and active power reference value, the slip angular frequency reference value is obtained; the damping power required to suppress frequency oscillation is calculated using the damping coefficient and slip angular frequency.

[0044] 3. Output: Output slip angular frequency reference value for subsequent control circuit; output damping power signal for adjusting system damping characteristics.

[0045] S202. Combining the flux linkage equation and voltage equation of the doubly fed asynchronous wind turbine, a voltage control equation is constructed for voltage control.

[0046] The voltage control equation proposed in this embodiment does not adopt the conventional PI outer loop regulation structure. Instead, it is based on the internal electromagnetic dynamics of the doubly fed asynchronous wind turbine, combining the flux linkage equation with the voltage equation to construct a voltage control model with clear physical meaning.

[0047] This model, based on traditional PI voltage error regulation, introduces a compensation term reflecting stator-rotor magnetic flux coupling, enabling real-time response to stator current disturbances and slip dynamic changes. This provides faster voltage tracking and stronger anti-interference capabilities during transient processes. This design enables doubly-fed asynchronous wind turbines to possess the equivalent voltage source characteristics for actively establishing and stabilizing grid voltage in passive networks. It is particularly suitable for the initial black start conditions where the system lacks external grid support, providing a crucial voltage foundation for subsequent unit startup and load restoration.

[0048] Specifically, using doubly-fed asynchronous wind turbines in dq The flux linkage equation and voltage equation in the coordinate system are used to obtain the control relationship between the stator voltage and the rotor voltage, and the control equation of the rotor voltage after processing by the PI controller is determined.

[0049] Doubly fed asynchronous wind turbines in dq The flux linkage equation in the coordinate system is expressed as: ; The voltage equation is expressed as: ; In the formula, 、 These represent the stator voltage and rotor voltage, respectively. 、 These represent the stator current and the rotor current, respectively. , These represent the stator flux linkage and the rotor flux linkage, respectively. 、 These represent the stator resistance and the rotor resistance, respectively. 、 These represent the self-inductance of the stator and the self-inductance of the rotor, respectively. This represents the mutual inductance between the stator and rotor, with j being the imaginary part.

[0050] Combining the flux linkage equation and the voltage equation, and neglecting the change in stator flux linkage and the stator and rotor resistances, we can obtain: ; In this formula, In Eliminating these variables yields the rotor voltage expression in terms of stator voltage, and the control relationship between them is shown in the following equation: ; The control equation for the rotor voltage after passing through the PI controller is derived from the above equation and is expressed as follows: ; .

[0051] in, This constitutes voltage tracking error. This is the stator voltage reference value. This is the actual measured value; the difference is processed by the PI controller. Generate basic control inputs; proportional gain of the PI controller k p The integral coefficient determines the system response speed. k i It is responsible for eliminating steady-state errors.

[0052] In The term reflects the degree of magnetic flux coupling between the stator and rotor; when the two are mutually inducted... When an appropriate value is selected, the voltage deviation caused by magnetic flux coupling will be eliminated. The device reflects stator current disturbances in real time, through (Slip angular velocity) Dynamically adjust compensation amount.

[0053] Furthermore, S202 specifically refers to: 1. Input: Stator voltage reference value Actual value of stator voltage Stator current and slip frequency .

[0054] 2. Input processing: Calculate voltage error The input is then fed into the PI controller; based on the flux linkage equation and the voltage equation, the rotor flux linkage is eliminated to obtain the rotor voltage control equation; the voltage error is substituted into the rotor voltage control equation to obtain the rotor voltage.

[0055] 3. Output: The output of the rotor voltage control equation is used to control the rotor-side converter.

[0056] Here, S201 and S202 can be executed in parallel.

[0057] S203, Introduce a virtual impedance This is to fill the gap in the inner loop of current control and to limit transient current.

[0058] ; in, This represents the actual value of the output excitation voltage of the rotor-side converter. This represents the actual value of the output excitation voltage of the rotor-side converter. This indicates the output current value of the rotor-side converter.

[0059] Here, the grid-side converter still uses the traditional voltage vector control strategy to control the DC bus voltage.

[0060] In summary, the improved virtual synchronous control strategy can simulate the inertia and mechanical characteristics of a traditional synchronous generator and establish virtual rotational equations. Doubly fed asynchronous wind turbines using this control strategy exhibit equivalent voltage source characteristics, meeting the requirements of black-start power supplies. During the subsequent black-start recovery process, when faced with load and generator power changes, unbalanced power can be quickly eliminated by adjusting the speed, thereby maintaining frequency stability.

[0061] S204. Using the wind turbines that have been started, establish voltage (e.g., 0.69kV) and frequency on the bus inside the wind farm, and then start the remaining turbines and loads inside the wind farm.

[0062] S3. Switch the V / F control strategy that introduces coupling terms to the P / Q control strategy that introduces coupling terms, and start the thermal power unit.

[0063] After all wind farm units and loads have started up and connected to the grid, the control strategy of the energy storage system is switched from V / F control to P / Q control. Since the doubly-fed asynchronous wind turbines employ a virtual synchronous control strategy at this time, simulating the characteristics of a traditional synchronous generator, frequency and voltage fluctuations are minimal during the switching process, and stability can be quickly restored. After the energy storage system completes the control strategy switch, the doubly-fed asynchronous wind turbines are responsible for maintaining the electrical quantities of the grid within a stable range, subsequently enabling the startup of the thermal power units.

[0064] Specifically, the P / Q control strategy consists of a power control outer loop and a current control inner loop. The power control outer loop comprises active power control and reactive power control. The active power controller is responsible for controlling the output active power, thereby maintaining frequency stability; the reactive power controller is responsible for controlling reactive power, thereby maintaining voltage stability. (See attached...) Figure 4 As shown in the P / Q control loop, the power control outer loop generates a dq-axis current reference signal, compares it with the actual current value, and then generates a voltage signal through a PI controller. This voltage signal is then converted into a converter control signal through PWM modulation. 、 These represent the dq-axis components of the output current of the energy storage system, respectively. , These refer to the dq-axis components of the energy storage system's output voltage. This control structure also introduces a coupling compensation term to eliminate coupling effects. This strategy is suitable for black-start power supplies after self-starting, adapting to power fluctuations caused by subsequent load connections, achieving rapid response to power changes, and preventing overcharging and discharging of the energy storage system.

[0065] As one implementation method, S3 specifically includes: 1. Power control outer loop: (1) Obtain the power signal of the battery energy storage unit: active power reference value Reactive power reference value 、 Actual value of active power P、 Actual value of reactive power Q .

[0066] (2) Processing: Calculate the active power and reactive power errors, and use the PI controller to generate dq-axis current reference signals respectively. , .

[0067] (3) Output: Output the dq axis current reference signal and transmit it to the current control inner loop.

[0068] 2. Current control inner loop: (1) Input: Receive the dq-axis current reference signal from the power control outer loop; obtain the actual value of the dq-axis current. 、 .

[0069] (2) Processing: Calculate the dq axis current error, introduce the coupling term ωL, combine the current error with PI control, and generate a voltage signal.

[0070] (3) Output: Output voltage signal, which enters the PWM modulation stage.

[0071] 3. PWM modulation stage: (1) Input: Voltage signal processed by the inner current loop.

[0072] (2) Processing: Based on the polarity and amplitude of the signal, the input voltage signal is PWM modulated to generate a PWM control signal.

[0073] (3) Output: Output control signal to regulate the switching action of the inverter and ensure that the output power of the energy storage system is maintained at the set value.

[0074] The descriptions of each embodiment in the above embodiments have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0075] This specific embodiment improves the underlying electromagnetic transient control strategy of the converter. Specifically, in the virtual synchronization control stage, this invention constructs an integrated virtual impedance (… The rotor-side voltage control architecture of the doubly-fed wind turbine overcomes the technical deficiency of traditional voltage source type virtual synchronous control, which cannot suppress transient inrush current due to the lack of a current inner loop. It optimizes the voltage source characteristics of the doubly-fed wind turbine in the early stage of black start to resist load changes and solves the transient safety problem of the equipment itself. Simultaneously, this invention introduces a dq-axis cross-coupling compensation term into the control loop of the battery energy storage unit. ωL and ωC By precisely offsetting the cross-coupling effect in the rotating coordinate system, the dynamic response speed and steady-state accuracy of voltage construction under weak grid conditions are significantly improved, ensuring the stability of the black-start power supply from the underlying control mechanism.

[0076] Example 2 Currently, new energy units relying on wind power, such as doubly-fed asynchronous wind turbines, generally suffer from a lack of self-starting capability and large fluctuations in output power. In view of this, this embodiment proposes a wind-storage combined black-start system that integrates coupling terms and improved virtual synchronization, directly connecting the battery energy storage unit to the grid bus.

[0077] like Figure 5 As shown, this embodiment provides a wind-storage joint black-start system that integrates coupling terms and improved virtual synchronization, including: Doubly fed asynchronous wind turbine generator sets are connected to the grid side through rotor-side converters and grid-side converters, and are used to supply power to the grid and start other units after grid connection; The battery energy storage unit, whose AC side is connected to the outlet of the doubly fed asynchronous wind turbine generator or the grid bus via a three-phase inverter, is used to establish grid voltage and frequency in the early stage of black start, thereby providing excitation conditions for the doubly fed asynchronous wind turbine generator and providing support for the grid in the subsequent stage.

[0078] Specifically, the black start system includes a doubly fed asynchronous wind turbine generator set and a battery energy storage unit. The doubly fed asynchronous wind turbine generator set is connected to the power grid through a back-to-back PWM converter, and the battery energy storage unit is connected in parallel to the DC bus on the grid side of the wind farm.

[0079] In this type of double-fed asynchronous wind turbine generator, the stator winding is directly connected to the power grid through a transformer, and the rotor-side converter of the rotor winding is connected to the DC bus, and then connected to the power grid through the grid-side converter and transformer. The frequency, voltage, amplitude and phase of the rotor winding power supply are automatically adjusted by the converter according to the operating requirements.

[0080] Traditional energy storage systems are mostly independently connected to the grid, or used as DC-side, AC-side, or load-side energy storage in photovoltaic systems. In contrast, the output of the battery energy storage unit used in this invention is connected to the outlet of a doubly-fed asynchronous wind turbine and then to the grid bus via a transformer. As part of a wind-storage integrated system, it provides excitation support for the doubly-fed asynchronous wind turbine, enabling the turbine to start automatically.

[0081] Furthermore, the battery energy storage unit includes a battery pack, a power conversion system (PCS), and its control system. The battery pack is directly connected to the DC side of the PCS via a DC bus. The DC output of the battery pack is filtered and regulated before being converted into AC power by the inverter module of the PCS. The DC side of the PCS is equipped with filter capacitors to smooth DC voltage fluctuations and uses IGBT switching devices to achieve DC / AC conversion. The AC side of the PCS is connected to the AC grid or load through filter inductors, capacitors, and transformers. The filter circuit is used to eliminate harmonics and ensure the quality of the output power.

[0082] Furthermore, it also includes a first controller and a second controller; the first controller is configured to execute a V / F control strategy and a P / Q control strategy that introduce coupling terms, and its output is connected to the three-phase inverter. It is used to establish the excitation voltage for the doubly-fed asynchronous wind turbine generator set through V / F control in the initial stage of startup, and to switch to P / Q control in the subsequent stage to adjust the grid-connected power; the second controller is built into the rotor-side converter and is configured to execute an improved virtual synchronous machine control strategy. The strategy combines the flux linkage equation and the voltage equation to construct a voltage control equation and introduces a virtual impedance loop. It is used to control the smooth connection of the doubly-fed asynchronous wind turbine generator set to the grid after the voltage is established, and to start the remaining wind turbine generator sets.

[0083] Furthermore, it also includes reactive power compensators, such as capacitor banks, static var compensators (SVCs), and static synchronous compensators (STATCOMs) that are equipped within the wind-storage integrated system.

[0084] Reactive power compensators are installed in energy storage units, wind turbines, loads, etc., to improve the power factor, reduce transmission line losses, improve power quality, and avoid three-phase imbalance.

[0085] Specifically, in the subsystem where the energy storage device is located, the reactive power compensator is connected to the connection bus between the energy storage device and the power grid to assist the energy storage system in regulating reactive power and improving the reactive power support capability and power quality of the entire system.

[0086] This specific embodiment rapidly establishes a stable voltage frequency based on V / F control with coupling terms during the initial stage of black start, providing reliable excitation for the doubly-fed induction generator (DFIG) wind turbine. The improved virtual synchronous machine control integrates flux linkage and voltage equations, coupled with a virtual impedance loop, ensuring smooth grid connection of the wind turbine without impact. Subsequent switching of P / Q control precisely adjusts power, with energy storage and the wind turbine working together to provide continuous support to the grid. This effectively solves the problems of traditional black start relying on a single power source and high grid connection difficulty, improving the success rate of black start and grid recovery stability, and is suitable for scenarios with a high proportion of renewable energy integration.

[0087] Example 3 This embodiment provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps in the wind-storage joint black-start method for fusion coupling terms and improved virtual synchronization as described in Embodiment 1 above.

[0088] The steps or modules involved in Embodiments 2 and 3 above correspond to those in Embodiment 1. For specific implementation details, please refer to the relevant description section of Embodiment 1. The term "computer-readable storage medium" should be understood as a single medium or multiple media including one or more instruction sets; it should also be understood as including any medium capable of storing, encoding, or carrying an instruction set for execution by a processor and enabling the processor to perform any of the methods in this invention.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wind-storage joint black start method integrating coupling terms and improved virtual synchronization, characterized in that, include: The control signal is determined by introducing a V / F control strategy with coupling terms and output to the battery energy storage unit. The battery energy storage unit is then used to provide excitation for the doubly-fed asynchronous wind turbine generator to achieve its self-starting. An improved virtual synchronous control strategy is adopted to control the rotor-side converter, and the doubly-fed asynchronous wind turbine generators are connected to the grid. The remaining wind farm units are started using the successfully connected doubly-fed asynchronous wind turbine generators. Switch the V / F control strategy that introduces coupling terms to the P / Q control strategy that introduces coupling terms, and start the thermal power unit; Among them, the improved virtual synchronous control strategy combines the flux linkage equation and the voltage equation to construct the voltage control equation, and introduces virtual impedance to make up for the gap in the current control inner loop.

2. The wind-storage joint black start method with fusion coupling terms and improved virtual synchronization as described in claim 1, characterized in that, The improved virtual synchronous control strategy for controlling the rotor-side converter also includes frequency control of the rotor-side converter based on the virtual rotation equation, damping equation, and slip angular frequency of the doubly-fed asynchronous wind turbine. The specific process is as follows: Based on the deviation between the actual angular frequency and the rated frequency, and the active power reference value, the slip angular frequency reference value is calculated using the virtual rotation equation. Based on the damping equation and the damping coefficient, the magnitude of the damping power is determined to suppress frequency oscillations; The slip angular frequency reference value and damping power are fed back to the control system of the rotor-side converter. The control system adjusts the output of the rotor-side converter in real time according to the parameters to achieve frequency control of the doubly-fed asynchronous wind turbine.

3. The wind-storage joint black start method with fusion coupling terms and improved virtual synchronization as described in claim 1, characterized in that, The P / Q control strategy that introduces coupling terms includes: The power reference signal and active power of the battery energy storage unit are acquired and PI control is performed to generate... dq Shaft current reference signal; Obtain the actual current value, for dq The shaft current reference signal and the actual current value are used for PI control. A coupling term is introduced to generate a voltage signal and perform PWM modulation to obtain the converter control signal.

4. The wind-storage joint black start method with fusion coupling terms and improved virtual synchronization as described in claim 1, characterized in that, The V / F control strategy that introduces coupling terms includes: The d-axis voltage reference value, d-axis voltage value, q-axis voltage reference value, and q-axis actual value output by the battery energy storage unit are obtained and PI control is performed. Combined with the first coupling term, the current control signal is determined. The d-axis and q-axis current values ​​output by the battery energy storage unit are obtained, and PI control is performed in conjunction with the current control signal. A second coupling term is introduced to determine the voltage control signal, which is then modulated by PWM to generate the control signal.

5. The wind-storage joint black start method with fusion coupling terms and improved virtual synchronization as described in claim 1, characterized in that, The specific method for constructing the voltage control equation by combining the flux linkage equation and the voltage equation is as follows: Utilizing a doubly-fed asynchronous wind turbine... dq The flux linkage equation and voltage equation in the coordinate system are used to obtain the control relationship between the stator voltage and the rotor voltage, and the control equation of the rotor voltage after processing by the PI controller is determined.

6. The wind-storage joint black start method with fusion coupling terms and improved virtual synchronization as described in claim 5, characterized in that, The governing equation is expressed as follows: ； ； In the formula, Indicates the stator voltage reference value. This represents the actual measured value. This represents the proportionality coefficient. Indicates the integral coefficient; For the self-sensing of the stator, For rotor self-inductance, For mutual inductance between stator and rotor, This term reflects the degree of magnetic flux coupling between the stator and rotor. This item reflects stator current disturbances in real time. Let ω be the slip angular velocity, and j be the imaginary part.

7. The wind-storage joint black start method with fusion coupling terms and improved virtual synchronization as described in claim 1, characterized in that, The specific steps for introducing virtual impedance to compensate for the gap in the current control inner loop are as follows: ； in, This represents the actual value of the output excitation voltage of the rotor-side converter. This represents the actual value of the output excitation voltage of the rotor-side converter. This indicates the output current value of the rotor-side converter. This represents virtual impedance.

8. A wind-storage combined black-start system integrating coupling terms and improved virtual synchronization, characterized in that, include: Doubly fed asynchronous wind turbine generator sets are connected to the grid side through rotor-side converters and grid-side converters, and are used to supply power to the grid and start other units after grid connection; The battery energy storage unit, whose AC side is connected to the outlet of the doubly fed asynchronous wind turbine generator set or the grid bus via a three-phase inverter, is used to establish grid voltage and frequency in the early stage of black start, thereby providing excitation conditions for the doubly fed asynchronous wind turbine generator set and providing support for the grid in the subsequent stage. It also includes a first controller and a second controller; the first controller is configured to execute a V / F control strategy and a P / Q control strategy that introduce coupling terms, and its output is connected to the three-phase inverter. It is used to establish and maintain a stable bus voltage and frequency through V / F control in the initial stage of startup, and to switch to P / Q control in the subsequent stage to adjust the grid-connected power; the second controller is built into the rotor-side converter and is configured to execute an improved virtual synchronous machine control strategy. The strategy combines the flux linkage equation and the voltage equation to construct a voltage control equation and introduces a virtual impedance loop. It is used to control the smooth connection of the doubly-fed asynchronous wind turbine generator to the grid after the voltage is established, and to start the other wind turbine generators.

9. The wind-storage combined black-start system with fusion coupling terms and improved virtual synchronization as described in claim 8, characterized in that, It also includes a reactive power compensator, which is connected to the bus between the battery energy storage unit and the power grid to compensate for the reactive power output of the wind turbine generator, improve the power quality of the wind power output, and reduce voltage fluctuations caused by the volatility of wind power generation.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the wind-storage joint black start method of fusion coupling item and improved virtual synchronization as described in any one of claims 1-7.

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