A wind farm modeling method, system, device and storage medium containing a doubly-fed wind turbine and a direct-drive wind turbine with adjustable proportion

Abstract

This invention discloses a wind farm modeling method, system, equipment, and storage medium with adjustable ratios of doubly-fed induction generators (DFIGs) and direct-drive turbines. It establishes AC grid-connected models of a single DFIG via a voltage source converter and a single direct-drive turbine via an AC grid connection, constructing a PSCAD / EMTDC simulation platform containing multiple DFIGs and multiple direct-drive turbines. Using a dynamic equivalent method, the wind farm with multiple DFIGs and multiple direct-drive turbines is equivalent to a single-turbine wind farm. An electromagnetic transient model of the wind farm's DC grid-connected system is established. By adjusting the ratio of DFIGs to direct-drive turbines, wind farm models with different turbine groups are constructed, and the effectiveness of the wind farm models is verified. This invention simultaneously includes DFIGs and direct-drive turbines in the same wind farm and adjusts the ratio of the two types of turbines through equivalent parameters. Short-circuit fault simulations are performed at the wind farm ports of the electromagnetic transient models with different turbine ratios, and fault characteristics are analyzed to verify the model's effectiveness.

Description

Technical Field

[0001] This invention relates to the field of wind farm equivalent modeling, specifically to a wind farm modeling method, system, equipment, and storage medium that includes doubly fed wind turbines and direct-drive wind turbines with adjustable ratios. Background Technology

[0002] Doubly fed induction generators (DFIGs) and direct-drive wind turbines are common types of wind turbines. DFIGs use a doubly fed frequency converter to regulate the generator speed, thereby controlling the generator torque and wind power. Direct-drive wind turbines (PMSGs) connect the generator directly to the wind turbine, eliminating the need for a gearbox and feeder mechanism. They use permanent magnets instead of the excitation coils in traditional generators, thus reducing mechanical losses and the complexity of the power generation system.

[0003] The main advantage of the DFIG system is its adaptability, allowing it to operate under various grid conditions. However, it requires additional power electronics and control systems, resulting in higher costs. The PMSG system, on the other hand, offers greater grid adaptability and responsiveness, better handling grid faults and voltage fluctuations.

[0004] In general, doubly-fed wind turbines and direct-drive wind turbines are the two main technical routes in the current wind power field. With the continuous development and maturity of the technology, real-world engineering practices are increasingly inclined to rationally configure different wind turbine units according to their respective advantages in order to form a hybrid wind farm cluster. This trend has become one of the main ways to renovate and expand old wind farms and build large-capacity new wind farms. Summary of the Invention

[0005] The purpose of this invention is to provide a wind farm modeling method, system, device, and storage medium that includes a doubly-fed fan and a direct-drive fan with an adjustable ratio, in order to address the above-mentioned situation.

[0006] This invention is based on a single AC grid-connected model and uses a dynamic equivalent method to convert a wind farm consisting of multiple wind turbines into a single wind turbine, reducing system complexity. The interaction mechanism of the system becomes more complex when two different types of wind turbines are connected to the wind farm; therefore, it is necessary to perform equivalent modeling on mixed wind farms containing both doubly-fed induction generators (DFIGs) and direct-drive turbines to provide a simulation basis for practical engineering.

[0007] This invention is achieved through the following technical solution:

[0008] A wind field modeling method with adjustable ratio of doubly-fed induction generators and direct-drive fans includes the following steps:

[0009] Step 1: Based on the topology of the doubly-fed induction generator (DFIG) and its voltage source converter system, establish a single DFIG AC grid-connected model via a voltage source converter. Based on the topology of the direct-drive fan and its voltage source converter system, establish a single direct-drive fan AC grid-connected model via a voltage source converter. This forms a PSCAD / EMTDC simulation platform containing multiple DFIGs and multiple direct-drive fans.

[0010] Step 2: Use the dynamic equivalent method to convert the wind farm with multiple doubly fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a wind farm with a single wind turbine.

[0011] Step 3: Establish an electromagnetic transient model of the wind farm's DC grid-connected system on the PSCAD / EMTDC simulation platform;

[0012] Step 4: Adjust the ratio of doubly fed wind turbines to direct-drive wind turbines in the PSCAD / EMTDC simulation platform, construct wind field models with different ratios of wind turbine groups, and verify the effectiveness of the wind field models.

[0013] To optimize the above technical solution, the specific measures / limitations also include:

[0014] In step 1, the specific method for establishing a single doubly-fed induction generator (DFIG) AC grid-connected model via a voltage source converter based on the system topology of the DFIG and its voltage source converter is as follows:

[0015] When the rotor side of the doubly-fed induction generator (DFIG) uses active power / reactive power control, and the stator output power is set to:

[0016]

[0017] In the formula, P s Q represents the active power output of the doubly-fed induction generator stator. s u represents the reactive power output of the doubly-fed induction generator stator. sd For the stator d-axis voltage, u sq For the stator q-axis voltage, i sd For the stator d-axis voltage, i sq U is the stator q-axis voltage. s L is the magnitude of the stator voltage vector. m For the equivalent mutual inductance of the stator and rotor windings in a synchronous rotating coordinate system, L s For the equivalent self-inductance of the stator winding in a synchronous rotating coordinate system, i rd i is the d-axis component of the rotor current. rq ω1 is the q-axis component of the rotor current, and ω1 is the synchronous angular velocity.

[0018] The active and reactive power output from the stator to the grid are decoupled and regulated by the d-axis and q-axis components of the rotor current, respectively. Using feedforward compensation and a PI regulator control method, the control equation for the doubly-fed induction generator (DFIG) rotor voltage is expressed as follows:

[0019]

[0020] In the formula, L r For the equivalent self-inductance of the rotor winding in a synchronous rotating coordinate system, k p k i These are the proportional and integral regulation coefficients of the rotor current inner loop, u rd The voltage across the rotor's d-axis, u rq Let i be the rotor q-axis voltage. rd * i rq * ω2 represents the reference values ​​for the d-axis and q-axis components of the rotor current, and ω2 represents the slip angular velocity; S is the numerator of the standard formula after Laplace transform in PI control.

[0021] The grid side uses DC voltage / grid side current q-axis component control. The control equations for the outer loop of the grid side converter are expressed as follows:

[0022]

[0023] In the formula, k p0 k i0 These are the proportional and integral adjustment coefficients of the rotor-side control outer loop, respectively.

[0024] To enable voltage source converters to operate with only the capacity limitations of the converter station in mind, frequency control is implemented based on the active power imbalance, employing a constant AC voltage-frequency control strategy for U. ac / f control, with the following control equations:

[0025]

[0026] In the formula, K p K i These are the proportional and integral coefficients in a PI controller, respectively. d v q These are the d-axis and q-axis components of the converter voltage, respectively. ac U is the AC bus voltage. ac * represents the reference value for AC bus voltage, and M is an intermediate variable.

[0027] In step 1, the specific method for establishing a single direct-drive wind turbine connected to the AC grid via a voltage source converter based on the system topology of the direct-drive wind turbine and its voltage source converter is as follows:

[0028] The wind turbine side adopts a vector control strategy based on rotor flux orientation, with an outer speed loop and an inner current loop. The outer speed loop control equation is as follows:

[0029]

[0030] In the formula, k p1 k i1 These are the proportional and integral coefficients of the outer loop PI controller, respectively. These are reference values ​​for the active power output from the fan side and the fan speed, respectively. These are the reference values ​​for the d-axis and q-axis components of the output current on the fan side, respectively.

[0031] The inner current control equation is:

[0032]

[0033] In the formula, k p2 k i2 These are the proportional and integral coefficients of the current inner-loop PI controller, respectively; R s The equivalent impedance of the wind turbine-side converter; u sd u sq These are the d-axis and q-axis components of the wind turbine-side voltage, respectively; i ds i qs These are the d-axis and q-axis components of the wind turbine-side current, respectively; ψ f The magnetic flux generated by the permanent magnet;

[0034] The grid-side converter uses DC voltage / reactive power control, and its outer-loop voltage control equation is as follows:

[0035]

[0036] In the formula, k P3 k i3 These are the proportional and integral coefficients of the outer loop PI controller, respectively; U dc *、Q g *These are reference values ​​for DC voltage and reactive power output to the grid, respectively. These are the reference values ​​for the d-axis and q-axis components of the grid-side output current, respectively. The inner-loop control equation for the grid-side converter current is:

[0037]

[0038] In the formula, k P4 k i4 These are the proportional and integral coefficients of the current inner-loop PI controller, respectively; R g i is the equivalent impedance of the grid-side converter; dg i qg These are the d-axis and q-axis components of the grid-side output current, u.dg u qg These are the d-axis and q-axis components of the grid-side voltage, respectively; ω g This refers to the angular velocity on the power grid side.

[0039] In step 2, the method of using dynamic equivalence to convert the wind farm with multiple doubly-fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a single-turbine wind farm is as follows:

[0040] A weighted aggregation algorithm with dynamically updated weighted coefficients is used to approximate wind farms, where:

[0041] The expression for the weighting coefficients is as follows:

[0042]

[0043] In the formula, n is the number of wind turbines, and S i Let σ be the actual power output of the i-th wind turbine. i Let be the weighting coefficient for the i-th wind turbine;

[0044] The following formula is used to determine whether the weighting coefficients need to be updated:

[0045]

[0046] In the formula, ΔS i Let S be the change in power output of the i-th wind turbine. m ΔS is the sum of the power output of all the wind turbines. m The change in the sum of the power output of all wind turbines is represented by C, which serves as the criterion. When C is greater than 1, the weighting coefficient is updated based on the current power output.

[0047] According to the weighted aggregation algorithm, the expression for the stator resistance and reactance of the wind turbine is as follows:

[0048]

[0049] In the formula, R seq X is the equivalent stator resistance. seq R is the equivalent stator reactance. si Let X be the stator resistance of the i-th wind turbine. si The stator reactance of the i-th wind turbine;

[0050] Similarly, the expression for the rotor resistance and reactance of the fan is obtained:

[0051]

[0052] In the formula, R req X is the equivalent rotor resistance. req R is the equivalent rotor reactance. ri Let X be the rotor resistance of the i-th fan.ri Let i be the rotor reactance of the i-th fan.

[0053] The expression for the magnetizing reactance is:

[0054]

[0055] In the formula, X meq X is the equivalent excitation reactance. mi Let be the excitation reactance of the i-th wind turbine.

[0056] In step 3, the specific method for establishing the electromagnetic transient model of the wind farm DC grid-connected system on the PSCAD / EMTDC simulation platform is as follows:

[0057] The rectifier side employs a constant AC voltage-frequency control strategy for U. ac / f control;

[0058] Inverter control connected to the AC grid employs a strategy of controlling DC voltage stability and reactive power exchanged with the grid.

[0059] In step 4, after adjusting the ratio of doubly-fed induction generators (DFIGs) to direct-drive turbines in the PSCAD / EMTDC simulation platform and constructing wind field models containing turbine groups of different ratios, the specific method for verifying the effectiveness of the wind field model is as follows:

[0060] Electromagnetic transient models of wind turbine groups with varying turbine ratios were used to simulate short-circuit faults at wind farm ports. Fault characteristics were analyzed to verify the model's effectiveness. The turbine-side current was denoted as I. m The impedance on the fan side is denoted as Z. m The grid-side current is denoted as I. g The impedance on the fan side is denoted as Z. g Let n be the number of equivalent wind turbines required. The design of equivalent components should satisfy the following formula:

[0061]

[0062] The ratio of doubly-fed fans to direct-drive fans can be adjusted by changing the number of equivalent fans in the equivalent elements at the outlet of the fan group, and the fault characteristics of the same fault point can be compared and analyzed.

[0063] This invention also protects a wind field modeling system comprising a doubly-fed induction generator (DFIG) and a direct-drive fan with an adjustable ratio, comprising:

[0064] The simulation platform construction module is used to establish an AC grid-connected model of a single doubly-fed wind turbine via a voltage source converter based on the topology of the doubly-fed wind turbine and its voltage source converter system, and to establish an AC grid-connected model of a single direct-drive wind turbine via a voltage source converter based on the topology of the direct-drive wind turbine and its voltage source converter system, thus forming a PSCAD / EMTDC simulation platform containing multiple doubly-fed wind turbines and multiple direct-drive wind turbines.

[0065] The equivalent calculation module is used to use the dynamic equivalent method to convert the wind farm with multiple doubly fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a wind farm with a single wind turbine.

[0066] The electromagnetic transient model building module is used to build electromagnetic transient models of wind farm DC grid-connected systems on the PSCAD / EMTDC simulation platform.

[0067] The wind field model construction and verification module is used to adjust the ratio of doubly fed wind turbines to direct-drive wind turbines in the PSCAD / EMTDC simulation platform, construct wind field models containing wind turbine groups with different ratios, and verify the effectiveness of the wind field models.

[0068] The present invention also protects an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the wind field modeling method described above, which includes doubly fed wind turbines and direct-drive wind turbines in an adjustable ratio.

[0069] The present invention also protects a computer-readable storage medium storing a computer program that causes a computer to execute the wind field modeling method described above, which includes doubly-fed and direct-drive wind turbines in an adjustable ratio.

[0070] Compared with the prior art, the beneficial effects of the present invention are:

[0071] The method and system of this invention add dynamic updating of weighting coefficients to the original weighted aggregation algorithm. The weighting coefficients are updated according to the actual power of the wind field, so that the equivalent wind field is closer to the reality.

[0072] This invention establishes a hybrid wind farm model that includes both doubly-fed induction generators (DFIGs) and direct-drive wind turbines in an adjustable ratio. This model is more in line with the actual engineering development trend and allows the wind turbine ratio in the simulation model to be adjusted according to the actual wind turbine ratio in the project. This provides a convenient simulation model for hybrid wind farms in actual projects. Attached Figure Description

[0073] Figure 1 This is a flowchart of the overall process for a wind field modeling method of the present invention, which includes a doubly fed fan and a direct-drive fan with an adjustable ratio.

[0074] Figure 2This is a topology diagram of a doubly-fed wind turbine connected to a DC grid.

[0075] Figure 3 This is a control block diagram of the rotor-side converter of a doubly fed wind turbine.

[0076] Figure 4 This is a block diagram of the control of the stator-side converter of a doubly-fed wind turbine.

[0077] Figure 5 This is a control block diagram for a voltage source converter.

[0078] Figure 6 This is a topology diagram of a direct-drive wind turbine connected to a DC grid system.

[0079] Figure 7 This is a control block diagram of the converter on the fan side of a direct-drive fan.

[0080] Figure 8 This is a control block diagram of the grid-side converter for a direct-drive wind turbine.

[0081] Figure 9 This is a topology diagram of a hybrid wind farm DC grid-connected system;

[0082] Figure 10 The figures show the simulation results of the electromagnetic transient model of the DC grid-connected system of a hybrid wind farm with different wind turbine ratios. Detailed Implementation

[0083] The present invention will be further described in detail below through embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0084] In the description of this invention, it should also be noted that:

[0085] In this invention, the d-axis and q-axis refer to the axis of the center of the magnetic field generated by the magnetic poles of the motor as the direct axis (d-axis), and the position that leads the direct axis by 90° electrical angle is defined as the quadrature axis (q-axis).

[0086] The "decoupling of active and reactive power output from the stator to the power grid" in this invention uses Taylor expansion and ignores higher orders, so its decoupling is an approximate decoupling.

[0087] In this invention, a converter station refers to an electrical station containing a large number of electrical devices, including converters.

[0088] In one embodiment, the present invention proposes a wind field modeling method with adjustable ratio of doubly-fed induction generators and direct-drive fans, comprising the following steps:

[0089] Step 1: Based on the topology of the doubly-fed induction generator (DFIG) and its voltage source converter system, establish a single DFIG AC grid-connected model via a voltage source converter. Based on the topology of the direct-drive fan and its voltage source converter system, establish a single direct-drive fan AC grid-connected model via a voltage source converter. This forms a PSCAD / EMTDC simulation platform containing multiple DFIGs and multiple direct-drive fans.

[0090] In step 1, the specific method for establishing a single doubly-fed induction generator (DFIG) AC grid-connected model via a voltage source converter based on the system topology of the DFIG and its voltage source converter is as follows:

[0091] When the rotor side of the doubly-fed induction generator (DFIG) uses active power / reactive power control, and the stator output power is set to:

[0092]

[0093] In the formula, P s Q represents the active power output of the doubly-fed induction generator stator. s u represents the reactive power output of the doubly-fed induction generator stator. sd For the stator d-axis voltage, u sq For the stator q-axis voltage, i sd For the stator d-axis voltage, i sq U is the stator q-axis voltage. s L is the magnitude of the stator voltage vector. m For the equivalent mutual inductance of the stator and rotor windings in a synchronous rotating coordinate system, L s For the equivalent self-inductance of the stator winding in a synchronous rotating coordinate system, i rd i is the d-axis component of the rotor current. rq ω1 is the q-axis component of the rotor current, and ω1 is the synchronous angular velocity.

[0094] The active and reactive power output from the stator to the grid are decoupled and regulated by the d-axis and q-axis components of the rotor current, respectively. Using feedforward compensation and a PI regulator control method, the control equation for the doubly-fed induction generator (DFIG) rotor voltage is expressed as follows:

[0095]

[0096] In the formula, L r For the equivalent self-inductance of the rotor winding in a synchronous rotating coordinate system, k p k i These are the proportional and integral regulation coefficients of the rotor current inner loop, u rd The voltage across the rotor's d-axis, u rq Let i be the rotor q-axis voltage. rd * i rq* ω2 represents the reference values ​​for the d-axis and q-axis components of the rotor current, and ω2 represents the slip angular velocity; S is the numerator of the standard formula after Laplace transform in PI control.

[0097] The grid side uses DC voltage / grid side current q-axis component control. The control equations for the outer loop of the grid side converter are expressed as follows:

[0098]

[0099] In the formula, k p0 k i0 These are the proportional and integral adjustment coefficients of the rotor-side control outer loop, respectively.

[0100] To enable voltage source converters to operate with only the capacity limitations of the converter station in mind, frequency control is implemented based on the active power imbalance, employing a constant AC voltage-frequency control strategy for U. ac / f control, with the following control equations:

[0101]

[0102] In the formula, K p K i These are the proportional and integral coefficients in a PI controller, respectively. d v q These are the d-axis and q-axis components of the converter voltage, respectively. ac U is the AC bus voltage. ac * represents the reference value for AC bus voltage, and M is an intermediate variable.

[0103] In step 1, the specific method for establishing a single direct-drive wind turbine connected to the AC grid via a voltage source converter based on the system topology of the direct-drive wind turbine and its voltage source converter is as follows:

[0104] The wind turbine side adopts a vector control strategy based on rotor flux orientation, with an outer speed loop and an inner current loop. The outer speed loop control equation is as follows:

[0105]

[0106] In the formula, k p1 k i1 These are the proportional and integral coefficients of the outer loop PI controller, respectively. These are reference values ​​for the active power output from the fan side and the fan speed, respectively. These are the reference values ​​for the d-axis and q-axis components of the output current on the fan side, respectively.

[0107] The inner current control equation is:

[0108]

[0109] In the formula, k p2 k i2 These are the proportional and integral coefficients of the current inner-loop PI controller, respectively; R s The equivalent impedance of the wind turbine-side converter; u sd u sq These are the d-axis and q-axis components of the wind turbine-side voltage, respectively; i ds i qs These are the d-axis and q-axis components of the wind turbine-side current, respectively; ψ f The magnetic flux generated by the permanent magnet;

[0110] The grid-side converter uses DC voltage / reactive power control, and its outer-loop voltage control equation is as follows:

[0111]

[0112] In the formula, k P3 k i3 These are the proportional and integral coefficients of the outer loop PI controller, respectively; U dc *、Q g *These are reference values ​​for DC voltage and reactive power output to the grid, respectively. These are the reference values ​​for the d-axis and q-axis components of the grid-side output current, respectively.

[0113] The inner-loop control equation for the grid-side converter current is:

[0114]

[0115] In the formula, k P4 k i4 These are the proportional and integral coefficients of the current inner-loop PI controller, respectively; R g i is the equivalent impedance of the grid-side converter; dg i qg These are the d-axis and q-axis components of the grid-side output current, u. dg u qg These are the d-axis and q-axis components of the grid-side voltage, respectively; ω g This refers to the angular velocity on the power grid side.

[0116] The overall flowchart of the wind field modeling method of the present invention, which includes doubly-fed induction generators and direct-drive fans with adjustable ratios, is as follows: Figure 1 As shown.

[0117] Figure 2The diagram shows the topology of a doubly-fed induction generator (DFIG) wind farm DC grid-connected system. This system includes a DFIG induction generator, a rotor-side converter, a grid-side converter, a step-up transformer, a voltage source converter, and a DC regulated power supply. The rotor-side converter uses constant active and reactive power control, the grid-side converter uses constant DC voltage and q-axis current control, and the voltage source converter uses constant AC voltage and frequency control. An electromagnetic transient model of the DC grid-connected system is established on the PSCAD / EMTDC simulation platform. The control block diagram of the rotor-side converter is shown below. Figure 3 As shown, the control block diagram of the wind turbine grid-side converter is as follows: Figure 4 As shown, the control block diagram of the voltage source converter is as follows: Figure 5 As shown.

[0118] Figure 2 The diagram shows the topology of a direct-drive wind farm DC grid-connected system. This system includes a direct-drive generator, a turbine-side converter, a grid-side converter, a turbine step-up transformer, a voltage source converter, and a DC regulated power supply. The turbine-side converter uses constant active and reactive power control, the grid-side converter uses constant DC voltage and reactive power control, and the voltage source converter uses constant AC voltage and frequency control. An electromagnetic transient model of the wind farm DC grid-connected system is established on the PSCAD / EMTDC simulation platform. The control block diagram of the turbine-side converter is shown below. Figure 7 As shown, the grid-side converter control block diagram is as follows: Figure 8 As shown, the control block diagram of the voltage source converter is as follows: Figure 5 As shown.

[0119] Step 2: Use the dynamic equivalent method to convert the wind farm with multiple doubly fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a wind farm with a single wind turbine, thereby reducing the complexity of the system.

[0120] In step 2, a capacity-weighted aggregation algorithm is often used when equivalencing the internal circuits of multiple wind turbines. However, the power output of wind turbines is easily affected by the environment, and there is a deviation between the actual power and the capacity. Therefore, this invention uses a weighted aggregation algorithm with dynamically updated weighting coefficients to equivalence the internal circuits of wind turbines. The specific method is as follows:

[0121] A weighted aggregation algorithm with dynamically updated weighted coefficients is used to approximate wind farms, where:

[0122] The expression for the weighting coefficients is as follows:

[0123]

[0124] In the formula, n is the number of wind turbines, and S i Let σ be the actual power output of the i-th wind turbine. iLet be the weighting coefficient for the i-th wind turbine;

[0125] Considering the excessive computational burden of real-time monitoring of the actual power of each wind turbine and updating the weighting coefficients based on the actual power, the following formula is used to determine whether the weighting coefficients need to be updated:

[0126]

[0127] In the formula, ΔS i Let S be the change in power output of the i-th wind turbine. m ΔS is the sum of the power output of all the wind turbines. m The change in the sum of the power output of all wind turbines is represented by C, which serves as the criterion. When C is greater than 1, the weighting coefficient is updated based on the current power output.

[0128] According to the weighted aggregation algorithm, the expression for the stator resistance and reactance of the wind turbine is as follows:

[0129]

[0130] In the formula, R seq X is the equivalent stator resistance. seq R is the equivalent stator reactance. si Let X be the stator resistance of the i-th wind turbine. si The stator reactance of the i-th wind turbine;

[0131] Similarly, the expression for the rotor resistance and reactance of the fan is obtained:

[0132]

[0133] In the formula, R req X is the equivalent rotor resistance. req R is the equivalent rotor reactance. ri Let X be the rotor resistance of the i-th fan. ri Let i be the rotor reactance of the i-th fan.

[0134] The expression for the magnetizing reactance is:

[0135]

[0136] In the formula, X meq X is the equivalent excitation reactance. mi Let be the excitation reactance of the i-th wind turbine.

[0137] Step 3: Establish an electromagnetic transient model of the wind farm's DC grid-connected system on the PSCAD / EMTDC simulation platform;

[0138] In step 3, the specific method for establishing the electromagnetic transient model of the wind farm DC grid-connected system on the PSCAD / EMTDC simulation platform is as follows:

[0139] The rectifier side employs a constant AC voltage-frequency control strategy for U. ac / f control;

[0140] Inverter control connected to the AC grid employs a strategy of controlling DC voltage stability and reactive power exchanged with the grid.

[0141] Step 4: Adjust the ratio of doubly fed wind turbines to direct-drive wind turbines in the PSCAD / EMTDC simulation platform, construct wind field models with different ratios of wind turbine groups, and verify the effectiveness of the wind field models.

[0142] In step 4, after adjusting the ratio of doubly-fed induction generators (DFIGs) to direct-drive turbines in the PSCAD / EMTDC simulation platform and constructing wind field models containing turbine groups of different ratios, the specific method for verifying the effectiveness of the wind field model is as follows:

[0143] Short-circuit fault simulations were performed at the wind farm ports of an electromagnetic transient model that adjusts wind turbine groups with different turbine ratios. The fault characteristics were analyzed to verify the effectiveness of the model.

[0144] based on Figure 9 The diagram shows the topology of a hybrid wind farm DC grid-connected system. This system includes a doubly-fed induction generator, a wind turbine rotor-side converter, a wind turbine grid-side converter, a direct-drive generator, a wind turbine-side converter, a grid-side converter, a wind turbine step-up transformer, an offshore split-type transformer, an AC bus, a flexible DC-DC turbine-side step-up transformer, a flexible DC-DC turbine-side converter, a flexible DC-DC grid-side converter, a flexible DC-DC grid-side step-down transformer, and a 525kV AC power supply. The flexible DC-DC turbine-side converter uses constant AC voltage and frequency control, while the flexible DC-DC grid-side converter uses constant active and reactive power control. An electromagnetic transient model of a DC grid-connected wind farm system is established on the PSCAD / EMTDC simulation platform. Each wind turbine group can select a type of wind turbine. There is an equivalent element at the outlet of the wind turbine. Its input parameters are reference voltage, reference frequency, reference capacity, number of equivalent wind turbines, per-unit stator reactance, per-unit stator resistance, per-unit rotor reactance, per-unit rotor resistance, and per-unit magnetizing reactance. The essence of this equivalent element is a controlled current source.

[0145] Let the current on the fan side be denoted as I. m The impedance on the fan side is denoted as Z. m The grid-side current is denoted as I. g The impedance on the fan side is denoted as Z. g Let n be the number of equivalent wind turbines required. The design of equivalent components should satisfy the following formula:

[0146]

[0147] The ratio of doubly-fed fans to direct-drive fans can be adjusted by changing the number of equivalent fans in the equivalent elements at the outlet of the fan group, and the fault characteristics of the same fault point can be compared and analyzed.

[0148] Taking each wind turbine group with 25 wind turbines as an example, when the wind turbine groups 1, 2, 3, and 4 have 100 direct-drive wind turbines, 75 direct-drive wind turbines, 25 doubly-fed wind turbines, 50 direct-drive wind turbines, 50 doubly-fed wind turbines, and 100 doubly-fed wind turbines respectively, the ratio of direct-drive wind turbines to doubly-fed wind turbines is 1:0, 3:1, 1:3, and 0:1, respectively, thus achieving adjustable ratios of different wind turbines.

[0149] Short-circuit fault simulations were performed at the wind farm ports of electromagnetic transient models with different wind turbine ratios, and the fault characteristics were analyzed to verify the effectiveness of the model.

[0150] To verify the effectiveness of the model, Figure 9 A three-phase short-circuit fault is set at point f1. The fault occurrence time is 10 seconds, and the fault duration is 4 seconds. Figure 10 The simulation results of a three-phase short-circuit fault at point f1 in the electromagnetic transient model of a hybrid wind farm DC grid-connected system with different turbine ratios are shown. P is the abbreviation for PMSG direct-drive wind turbine, and D is the abbreviation for DFIG doubly-fed induction generator (DFIG). The simulation compares the effective values ​​of the fault current near the wind farm side when the ratio of direct-drive and DFIG wind turbines is 1:0, 1:3, 1:1, and 0:1. Observing the simulation results, it is easy to see that as the ratio of DFIG wind turbines increases, the peak value of the effective short-circuit current continuously decreases, and the decay rate of the effective short-circuit current continuously accelerates. This is because the grid connection structures of direct-drive and DFIG wind turbines are different. The direct-drive wind farm is connected to the inverter... After conversion and grid connection, a P / Q control strategy is typically adopted to decouple the output active and reactive power. Direct-drive wind turbine generators are isolated from the grid. In the event of a three-phase short-circuit fault, the direct-drive turbine can be equivalent to a constant current source, continuously outputting a stable current. However, the doubly-fed induction generator (DFIG) is directly connected to the grid, exhibiting the characteristics of an asynchronous generator. When a fault occurs, the voltage at the wind farm outlet drops, and the voltage drop during a three-phase short-circuit fault is severe, making it impossible to maintain the normal grid-connected operation of the DFIG. This causes the circuit current supplied by the wind farm to gradually and rapidly decrease. The simulation results are consistent with the theoretical analysis, verifying the correctness and feasibility of this modeling method.

[0151] In another embodiment, the present invention proposes a wind field modeling system with an adjustable ratio of doubly-fed wind turbines and direct-drive wind turbines, comprising:

[0152] The simulation platform construction module is used to establish an AC grid-connected model of a single doubly-fed wind turbine via a voltage source converter based on the topology of the doubly-fed wind turbine and its voltage source converter system, and to establish an AC grid-connected model of a single direct-drive wind turbine via a voltage source converter based on the topology of the direct-drive wind turbine and its voltage source converter system, thus forming a PSCAD / EMTDC simulation platform containing multiple doubly-fed wind turbines and multiple direct-drive wind turbines.

[0153] The equivalent calculation module is used to use the dynamic equivalent method to convert the wind farm with multiple doubly fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a wind farm with a single wind turbine.

[0154] The electromagnetic transient model building module is used to build electromagnetic transient models of wind farm DC grid-connected systems on the PSCAD / EMTDC simulation platform.

[0155] The wind field model construction and verification module is used to adjust the ratio of doubly fed wind turbines to direct-drive wind turbines in the PSCAD / EMTDC simulation platform, construct wind field models containing wind turbine groups with different ratios, and verify the effectiveness of the wind field models.

[0156] In another embodiment, the present invention proposes an electronic device comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, it implements the wind field modeling method described above, which includes doubly fed wind turbines and direct-drive wind turbines with adjustable ratios.

[0157] In another embodiment, the present invention provides a computer-readable storage medium storing a computer program that causes a computer to execute the wind field modeling method described above, which includes doubly-fed and direct-drive wind turbines in an adjustable ratio.

[0158] In the embodiments disclosed in this application, a computer storage medium may be a tangible medium that may contain or store programs for use by or in conjunction with an instruction execution system, apparatus, or device. The computer storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, apparatus, or devices, or any suitable combination of the foregoing. More specific examples of computer storage media include electrical connections based on one or more wires, portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, or any suitable combination of the foregoing.

[0159] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A wind field modeling method comprising doubly-fed induction generators and direct-drive fans with adjustable ratios, characterized in that, Includes the following steps: Step 1: Based on the topology of the doubly-fed induction generator (DFIG) and its voltage source converter system, establish a single DFIG AC grid-connected model via a voltage source converter. Based on the topology of the direct-drive fan and its voltage source converter system, establish a single direct-drive fan AC grid-connected model via a voltage source converter. This forms a PSCAD / EMTDC simulation platform containing multiple DFIGs and multiple direct-drive fans. Step 2: Use the dynamic equivalent method to convert the wind farm with multiple doubly fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a wind farm with a single wind turbine. Step 3: Establish an electromagnetic transient model of the wind farm's DC grid-connected system on the PSCAD / EMTDC simulation platform; Step 4: Adjust the ratio of doubly fed wind turbines to direct-drive wind turbines in the PSCAD / EMTDC simulation platform, construct wind field models with different ratios of wind turbine groups, and verify the effectiveness of the wind field models; In step 1, the specific method for establishing a single doubly-fed induction generator (DFIG) AC grid-connected model via a voltage source converter based on the system topology of the DFIG and its voltage source converter is as follows: When the rotor side of the doubly-fed induction generator (DFIG) uses active power / reactive power control, and the stator output power is set to stator voltage directional control, the DFIG stator output power is: In the formula, P s This refers to the active power output of the stator of the doubly-fed wind turbine. Q s This refers to the reactive power output of the stator of the doubly-fed wind turbine. u sd For stator d shaft voltage, u sq For stator q shaft voltage, i sd For stator d shaft voltage, i sq For stator q shaft voltage, U s The magnitude of the stator voltage vector. L m The equivalent mutual inductance of the stator and rotor windings in a synchronous rotating coordinate system, L s The equivalent self-inductance of the stator winding in a synchronous rotating coordinate system, i rd For rotor current d Axial components, i rq For rotor current q Axial components, ω 1 represents the synchronous angular velocity; The active and reactive power output from the stator to the grid are decoupled and regulated by the d-axis and q-axis components of the rotor current, respectively. Using feedforward compensation and a PI regulator control method, the control equation for the doubly-fed induction generator (DFIG) rotor voltage is expressed as follows: In the formula, , L r The equivalent self-inductance of the rotor winding in a synchronous rotating coordinate system, k p , k i These are the proportional and integral regulation coefficients of the rotor current inner loop, respectively. The voltage across the rotor's d-axis. This is the rotor q-axis voltage. , Rotor current d , q Reference values ​​for axis components. It is the slip angular velocity; S It is the numerator of the standard formula after the Laplace transform in PI control; The grid side uses DC voltage / grid side current q-axis component control. The control equations for the outer loop of the grid side converter are expressed as follows: In the formula, , These are the proportional and integral adjustment coefficients of the rotor-side control outer loop, respectively. To enable voltage source converters to operate with only the capacity limitations of the converter station in mind, frequency control is implemented based on the active power imbalance, employing a constant AC voltage-frequency control strategy for U. ac / f control, with the following control equations: In the formula, K p , K i These are the proportional and integral coefficients in a PI controller, respectively. v d , v q These are the converter voltages. d Axial components, q Axial components, U ac AC bus voltage, U ac This is the reference value for AC bus voltage. M As an intermediate variable; In step 1, the specific method for establishing a single direct-drive wind turbine connected to the AC grid via a voltage source converter based on the system topology of the direct-drive wind turbine and its voltage source converter is as follows: The wind turbine side adopts a vector control strategy based on rotor flux orientation, with an outer speed loop and an inner current loop. The outer speed loop control equation is as follows: In the formula, , These are the proportional and integral coefficients of the outer loop PI controller, respectively. , These are reference values ​​for the active power output from the fan side and the fan speed, respectively. , The output current of the wind turbine side are respectively d , q Reference values ​​for axis components; The inner loop control equation for the current is: In the formula, , These are the proportional and integral coefficients of the current inner-loop PI controller, respectively. R s The equivalent impedance of the wind turbine-side converter; u sd , u sq These are the voltages on the wind turbine side. d , q Axial components; , These are the currents on the wind turbine side. d , q Axial components; ψ f The magnetic flux generated by the permanent magnet; The grid-side converter uses DC voltage / reactive power control, and its outer-loop voltage control equation is as follows: In the formula, , These are the proportional and integral coefficients of the outer loop PI controller, respectively. U dc , Q g These are reference values ​​for DC voltage and reactive power output to the power grid, respectively. , The output current on the grid side are respectively d , q Reference values ​​for axis components; The inner-loop control equation for the grid-side converter current is: In the formula, , These are the proportional and integral coefficients of the current inner-loop PI controller, respectively. R g This is the equivalent impedance of the grid-side converter. , These are the d-axis and q-axis components of the grid-side output current, respectively. , These are the grid-side voltages. d , q Axial components; ω g This refers to the angular velocity on the power grid side.

2. The wind field modeling method with adjustable ratio of doubly-fed induction generators and direct-drive fans according to claim 1, characterized in that: In step 2, the method of using dynamic equivalence to convert the wind farm with multiple doubly-fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a single-turbine wind farm is as follows: A weighted aggregation algorithm with dynamically updated weighted coefficients is used to approximate wind farms, where: The expression for the weighting coefficients is as follows: In the formula, n is the number of wind turbines. S i For the first i The actual power output of the typhoon generator σ i For the first i Weighting coefficients for typhoon generators; The following formula is used to determine whether the weighting coefficients need to be updated: In the formula, Δ S i For the first i The change in the power output of the typhoon generator. S m Δ is the sum of the power output of all the wind turbines. S m This represents the change in the sum of the power output of all the wind turbines. C As a basis for judgment, when C When the value is greater than 1, the weighting coefficients are updated based on the current power output. According to the weighted aggregation algorithm, the expression for the stator resistance and reactance of the wind turbine is as follows: In the formula, R seq For the equivalent stator resistance, X seq For equivalent stator reactance, R si For the first i Typhoon stator resistance X si For the first i Typhoon generator stator reactor; Similarly, the expression for the rotor resistance and reactance of the fan is obtained: In the formula, R req This is the equivalent rotor resistance. X req For equivalent rotor reactance, R ri For the first i Typhoon rotor resistance X ri For the first i Typhoon rotor reactance; The expression for the magnetizing reactance is: In the formula, X meq For equivalent excitation reactance, X mi For the first i Typhoon generator excitation reactance.

3. The wind field modeling method with adjustable ratio of doubly-fed induction generators and direct-drive fans as described in claim 1, characterized in that: In step 3, the specific method for establishing the electromagnetic transient model of the wind farm DC grid-connected system on the PSCAD / EMTDC simulation platform is as follows: The rectifier side employs a constant AC voltage-frequency control strategy for U. ac / f control; Inverter control connected to the AC grid employs a strategy of controlling DC voltage stability and reactive power exchanged with the grid.

4. The wind field modeling method with adjustable ratio of doubly-fed induction generators and direct-drive fans as described in claim 1, characterized in that: In step 4, after adjusting the ratio of doubly-fed induction generators (DFIGs) to direct-drive turbines in the PSCAD / EMTDC simulation platform and constructing wind farm models containing turbine groups of different ratios, the specific method for verifying the effectiveness of the wind farm model is as follows: Electromagnetic transient models of wind turbine groups with varying turbine ratios were used to simulate short-circuit faults at wind farm ports. Fault characteristics were analyzed to verify the model's effectiveness. The turbine-side current was denoted as... I m The impedance on the fan side is denoted as Z m Grid-side current record For I g The impedance on the fan side is denoted as Z g Record the number of wind turbines required to be equivalent. n The equivalent element design satisfies the following formula: The ratio of doubly-fed fans to direct-drive fans can be adjusted by changing the number of equivalent fans in the equivalent elements at the outlet of the fan group, and the fault characteristics of the same fault point can be compared and analyzed.

5. A wind field modeling system comprising doubly-fed induction generators (DFIGs) and direct-drive fans with adjustable ratios, used to execute the wind field modeling method comprising DFIGs and direct-drive fans with adjustable ratios as described in any one of claims 1-4, characterized in that, include: The simulation platform construction module is used to establish an AC grid-connected model of a single doubly-fed wind turbine via a voltage source converter based on the topology of the doubly-fed wind turbine and its voltage source converter system, and to establish an AC grid-connected model of a single direct-drive wind turbine via a voltage source converter based on the topology of the direct-drive wind turbine and its voltage source converter system, thus forming a PSCAD / EMTDC simulation platform containing multiple doubly-fed wind turbines and multiple direct-drive wind turbines. The equivalent calculation module is used to use the dynamic equivalent method to convert the wind farm with multiple doubly fed wind turbines and multiple direct-drive wind turbines in the PSCAD / EMTDC simulation platform into a wind farm with a single wind turbine. The electromagnetic transient model building module is used to build electromagnetic transient models of wind farm DC grid-connected systems on the PSCAD / EMTDC simulation platform. The wind field model construction and verification module is used to adjust the ratio of doubly fed wind turbines to direct-drive wind turbines in the PSCAD / EMTDC simulation platform, construct wind field models containing wind turbine groups with different ratios, and verify the effectiveness of the wind field models.

6. An electronic device, characterized in that, include: The system includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the wind field modeling method with adjustable ratio of doubly fed wind turbines and direct-drive wind turbines as described in any one of claims 1-4.

7. A computer-readable storage medium storing a computer program that causes a computer to execute the wind field modeling method according to any one of claims 1-4, which includes doubly-fed and direct-drive wind turbines with adjustable ratios.

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