A direct current wind farm boosting and collecting simulation method and simulation platform

Abstract

The application discloses a DC wind power plant boosting and collecting simulation method and a simulation platform, and relates to the field of electromechanical simulation.The method comprises the following steps: constructing a main circuit topology model of a DC wind power system, and determining control strategies of unit-level boosting, power balancing and field-level boosting; the main circuit topology model comprises multiple DC wind turbines, unit-level boosting units, power balancing units, field-level boosting units and a DC power grid; the unit-level boosting units are used for boosting voltage and current signals output by the DC wind turbines at the unit level; the field-level boosting units are used for boosting voltage and current signals output by the DC wind power plant at the field level; the power balancing units are used for balancing power among the multiple DC wind turbines; and the two-stage boosting and multi-machine collecting links of the DC wind power system are simulated in real time based on the main circuit topology model and the control strategies.The application can simulate and control the two-stage boosting and multi-machine collecting links of the DC wind power system, and can keep the stability of the DC link bus voltage.

Description

Technical Field

[0001] This invention relates to the field of electromechanical simulation, and in particular to a simulation method and platform for DC wind farm boost-integration. Background Technology

[0002] In order to actively develop marine resources, offshore wind turbines are gradually seeking technological advancements towards larger capacity and deeper waters. The selection of wind turbines is also gradually moving towards larger rotors and greater inertia, and large-capacity permanent magnet direct-drive generators are being selected for the generators.

[0003] Due to the significant distance between offshore areas and load terminals, offshore wind power resources are primarily transmitted via High-Voltage Direct Current (HVDC). In this context, DC wind turbines and DC wind farms have emerged. These involve omitting the inverter section of a full-power converter and networking the turbines through the DC link of the turbine-side rectifier. This transforms the wind farm network from a traditional AC aggregation network to a series-parallel DC aggregation network, distributing the power conversion tasks of the wind farm-side converters. This effectively addresses the challenges of constructing high-capacity converter platforms and large-scale converter station requirements in offshore areas, while also reducing the cost of transmitting offshore wind power. However, because DC-networked wind farms lack a farm-level converter link, the voltage level of the farm's collection bus is determined by the operating status of each turbine and the network topology between them, leading to instability in the DC link bus voltage. Summary of the Invention

[0004] The purpose of this invention is to provide a simulation method and platform for DC wind farm boosting and aggregation, which can simulate and control the secondary boosting and multi-machine aggregation links of DC wind power systems, and maintain the stability of the DC link bus voltage.

[0005] To achieve the above objectives, the present invention provides the following solution:

[0006] A simulation method for DC wind farm boost-and-collection includes:

[0007] A main circuit topology model of a DC wind power system is constructed. This model includes multiple DC wind turbines, a turbine-level boost unit, a power balancing unit, a field-level boost unit, and a DC grid. The turbine-level boost unit boosts the voltage and current signals output by each DC wind turbine. After being boosted at the turbine level, the voltage and current signals from multiple DC wind turbines are cascaded with independent inputs and series outputs to form a DC wind farm. The field-level boost unit boosts the voltage and current signals output by the DC wind farm and transmits them to the DC grid. The power balancing unit is located between the turbine-level and field-level boost units and performs power balancing among the multiple DC wind turbines.

[0008] The following strategies are defined: a unit-level boost control strategy, a power balancing control strategy, and a field-level boost control strategy. The unit-level boost control strategy uses a constant boost ratio to control the operating state of the unit-level boost unit. The power balancing control strategy controls the operating state of the power balancing unit based on the voltage signal output by the unit-level boost unit. The field-level boost control strategy uses a control shift ratio to control the operating state of the field-level boost unit.

[0009] Based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy, the two-stage boost and multi-unit aggregation stages of the DC wind power system are simulated in real time.

[0010] To achieve the above objectives, the present invention also provides the following solution:

[0011] A DC wind farm boost-and-convergence simulation platform is applied to the above-mentioned DC wind farm boost-and-convergence simulation method. The DC wind farm boost-and-convergence simulation platform includes: a desktop workstation, a digital signal processor, and a real-time simulator.

[0012] The real-time simulator includes a field-programmable gate array (FPGA) board and a central processing unit (CPU).

[0013] The desktop workstation is used to download the main circuit topology model to the field programmable gate array board of the real-time simulator, download the unit-level boost control strategy and power balancing control strategy to the central processing unit of the real-time simulator, and download the field-level boost control strategy to the digital signal processor.

[0014] The field-programmable gate array board, the central processing unit, and the digital signal processor perform real-time simulation of the secondary boost and multi-machine aggregation stages of the DC wind power system based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy.

[0015] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0016] This invention achieves unit-level voltage boosting through a unit-level boosting unit and a unit-level boosting control strategy, and achieves field-level voltage boosting through a field-level boosting unit and a field-level boosting control strategy, thus realizing two-stage voltage boosting of the DC wind power system and control of the multi-unit convergence link. At the same time, it can maintain the stability of the DC link bus voltage by performing power balancing among multiple DC wind turbines through a power balancing unit and a power balancing control strategy. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart of the DC wind farm boost-and-collection simulation method provided by the present invention;

[0019] Figure 2 A schematic diagram of a DC wind farm boost-and-collection simulation platform;

[0020] Figure 3 A schematic diagram of the main circuit component model;

[0021] Figure 4 This is a schematic diagram of a DC fan;

[0022] Figure 5 This is a schematic diagram of a Boost converter circuit.

[0023] Figure 6 A schematic diagram of the unit-level boost control strategy;

[0024] Figure 7 This is a schematic diagram of a power equalization circuit;

[0025] Figure 8 This is a schematic diagram of a power equalization control strategy;

[0026] Figure 9 This is a schematic diagram of a dual active bridge converter;

[0027] Figure 10 This is a schematic diagram of the field-level boost control strategy.

[0028] Symbol explanation: 1-Desktop workstation, 2-Digital signal processor, 3-Real-time emulator, 4-Central processing unit, 5-Field programmable gate array board, 6-Wind turbine, 7-Permanent magnet synchronous generator, 8-Rectifier, 9-Unit-level boost unit, 10-Power balancing unit, 11-Field-level boost unit, 12-DC grid. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The purpose of this invention is to provide a simulation method and platform for DC wind farm boosting and aggregation. By using a real-time simulator and a digital signal processor (DSP), the method can perform analysis, modeling and control of the secondary boosting and multi-unit aggregation of the DC wind power system, and realize functions such as secondary boosting test, multi-unit voltage and current sharing test, DC bus voltage stability test, control logic algorithm verification and fault voltage ride-through test.

[0031] This invention focuses on the wind turbine generator and boost converter stage, establishing a DC / DC converter object including high-frequency switches and a DC wind turbine. By formulating corresponding control strategies, it ensures that the physical characteristics of the circuit can meet the requirements of power transmission, secondary boost, and DC bus voltage stability of the wind turbine. The invention studies the boost and convergence characteristics of the wind turbine under all operating conditions rather than a single operating condition, supporting the research on the voltage and current characteristics of the boost and convergence stage under power over-generation and fault drop conditions of the wind turbine.

[0032] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] like Figure 1 As shown, the DC wind farm boost-and-convergence simulation method provided by this invention includes:

[0034] Step 0: Set up the simulation environment.

[0035] Specifically, such as Figure 2 As shown, the host computer software of the real-time emulator 3 and the digital signal processor 2 is tested and run on the desktop workstation 1, and it is ensured that the digital signal processor 2 and the real-time emulator 3 are connected.

[0036] Step 1: Construct the main circuit topology model of the DC wind power system. This invention builds the main circuit topology model of the DC wind power system based on a configuration software platform. The main circuit topology model is downloaded to the Field Programmable Gate Array (FPGA) board of the real-time simulator 3.

[0037] like Figure 3 As shown, the main circuit topology model includes multiple DC wind turbines, a unit-level boost unit 9, a power balancing unit 10, a field-level boost unit 11, and a DC power grid 12.

[0038] like Figure 4 As shown, each DC wind turbine includes a wind turbine 6, a permanent magnet synchronous generator 7, and a rectifier 8 connected in sequence. The output terminal of the rectifier 8 is connected to the input terminal of the unit-level boost unit 9.

[0039] The DC fan is modeled as follows:

[0040]

[0041] Among them, P m The output power of the DC fan is given by ρ, air density is given by R, and blade radius is given by C. P λ is the wind energy utilization coefficient, β is the tip speed ratio, β is the pitch angle, V is the horizontal inflow wind speed, and U is the pitch angle. in U is the DC voltage at the rectifier output. PMSG For the three-phase AC source phase voltage, I PMSG It represents the source phase current of a three-phase AC circuit.

[0042] The wind energy utilization coefficient is calculated using a lookup table. The input parameters of the lookup table are the tip speed ratio λ and the pitch angle β, and the output parameter is the wind energy utilization coefficient C. p Then, the power captured by wind turbine 6 is calculated. The permanent magnet synchronous generator 7 and the fully controlled rectifier can be equivalent to a three-phase power source plus an uncontrolled rectifier. From the above formula, it can be seen that the power of wind turbine 6, as a command value input to the power source, can cause it to output the corresponding three-phase AC voltage and current. After rectification by the uncontrolled rectifier, the corresponding DC voltage and current are output. The above DC wind turbine model is built in the configuration software and downloaded to the central processing unit (CPU) 4 of the real-time simulator 3. The three-phase power source and the uncontrolled rectifier are downloaded as part of the main circuitry to the FPGA board.

[0043] Step 2: Determine the unit-level boost control strategy, power balancing control strategy, and field-level boost control strategy. In this invention, the control logic corresponding to the main circuit topology model is built in the configuration software and then downloaded to the real-time simulator 3 and the digital signal processor 2, respectively.

[0044] The following sections describe the unit-level booster unit 9, the power balancing unit 10, the field-level booster unit 11, and the control strategies for each unit.

[0045] (1) The unit-level boosting unit 9 is used to boost the voltage and current signals output by each DC wind turbine. After the voltage and current signals output by multiple DC wind turbines are boosted at the unit level, they are cascaded in an input-independent output-series (IIOS) structure to form a DC wind farm.

[0046] The unit-level boost unit 9 includes multiple boost circuits. Each boost circuit is connected to a DC wind turbine to perform unit-level boosting of the voltage and current signals output by the DC wind turbine. Figure 5 As shown, the Boost circuit includes a first inductor, an input capacitor, an output capacitor, and an IGBT transistor.

[0047] This invention uses a configuration software environment to build a Boost boost circuit. The medium-voltage DC / DC converter uses a Boost boost circuit to complete the first-stage boost (unit-level boost). The inductance and capacitance values ​​of the Boost boost circuit are designed based on the power level of the wind turbine, the input and output voltages, and the switching frequency of the IGBT.

[0048] The first inductor value, input capacitor value, and output capacitor value of the i-th Boost converter are respectively:

[0049]

[0050] Among them, L i Let C be the first inductance value of the i-th Boost converter circuit. ini Let C be the input capacitor value of the i-th Boost converter circuit. oi Let D be the output capacitor value of the i-th Boost converter circuit. i U represents the duty cycle of the switching modulation signal of the i-th Boost converter circuit. ini U represents the input voltage of the i-th Boost converter circuit, and U represents the output voltage of the DC fan connected to the i-th Boost converter circuit. oi Let I be the output voltage of the i-th Boost converter. oi f is the output current of the i-th Boost converter. i P is the switching frequency of the IGBT transistor in the i-th Boost converter circuit. i Let ΔU be the input power of the i-th Boost converter. ini Let ΔU be the ripple of the input voltage of the i-th Boost circuit.oi This represents the ripple of the output voltage of the i-th Boost converter.

[0051] The unit-level boost control strategy is used to control the operating state of the unit-level boost unit 9 using a constant boost ratio strategy.

[0052] like Figure 6 As shown, the process of controlling the operating state of the unit-level boost unit 9 using a constant boost ratio strategy (i.e., maintaining the circuit boost ratio at a set value) specifically includes:

[0053] For any Boost converter circuit, the boost ratio is set. The product of the input voltage and the boost ratio is calculated to obtain the input voltage. The deviation between the input voltage and the output voltage is calculated, and a first PI controller is used to determine the reference value of the inductor current. The deviation between the reference value and the inductor current is calculated, and a second PI controller is used to determine the duty cycle of the switching modulation signal to control the on / off state of the IGBT in the Boost converter circuit.

[0054] Specifically, the outer loop voltage control strategy is first established: the gain module in the configuration software is used to set the given boost ratio K, the controller is selected as a PI controller, and the input of the first PI controller is K times the input voltage U. ini With output voltage U oi The deviation is output as the inductor current reference value I. Li，ref .

[0055] Then, an inner-loop current control strategy is established: the inductor current reference value I is obtained in the outer loop. Li，ref Under the premise that the inner loop also selects a PI controller, the input of the second PI controller is the inductor current reference value I. Li，ref With inductor current I Li The deviation is output as the duty cycle D of the switch modulation signal. i Then, a square wave generator is used to obtain the switching modulation signal K. i It controls the on / off state of the IGBT transistor to maintain a constant boost ratio in the boost circuit.

[0056] (2) The power balancing unit 10 is disposed between the unit-level boost unit 9 and the field-level boost unit 11. The power balancing unit 10 is used to balance the power between multiple DC wind turbines.

[0057] Multiple DC fans are connected in series, and the sum of the output voltages of the DC fans is the DC bus voltage. However, when the output power of the DC fans in the IIOS structure changes, their output voltage will also fluctuate, causing voltage oscillation, which in turn affects the stability of the DC bus voltage and damages the medium-voltage DC / DC converter. In order to ensure that the output voltage can be maintained at the set value when the power of the DC fans fluctuates, a power balancing circuit is established.

[0058] The power balancing unit 10 includes multiple power balancing circuits. Each power balancing circuit is connected to two adjacent Boost converter circuits to perform power balancing between two adjacent DC wind turbines. Figure 7 As shown, each power balancing circuit includes an energy storage inductor L and two second IGBT transistors Q1 and Q2. One end of the energy storage inductor is connected to the output capacitor C of the two boost converter circuits. i and C i+1 Between them, the other end of the energy storage inductor is connected between the two second IGBT tubes.

[0059] The energy storage inductance value of the i-th power balancing circuit is:

[0060]

[0061] Among them, L K Let U be the energy storage inductance value of the i-th power balancing circuit. o U is the DC bus voltage. o =U o1 +U o2 +...+U oi U oi Let ε be the output voltage of the i-th Boost converter. i Let n be the peak-to-peak ripple ratio of the energy storage inductor current in the i-th power balancing circuit, typically taken as 25%. f f represents the number of DC fans. b P is the switching frequency of the second IGBT in the power equalization circuit (all IGBTs in the power equalization circuit have the same switching frequency). b This represents the total output power of the DC fan.

[0062] The power balancing control strategy is used to control the operating state of the power balancing unit 10 based on the voltage signal output by the unit-level boost unit 9.

[0063] like Figure 8 As shown, the process by which the power balancing control strategy controls the operating state of the power balancing unit 10 based on the voltage signal output by the unit-level boost unit 9 specifically includes:

[0064] For any power balancing circuit, calculate the difference in output voltage between the two Boost converters connected to the power balancing circuit, and use a third PI controller to determine the reference value of the energy storage inductor current of the power balancing circuit. Calculate the reference value of the energy storage inductor current and the energy storage inductor current value I. L The deviation is determined, and a fourth PI controller is used to generate a PWM modulation wave signal for the power equalization circuit to control the on / off state of the two second IGBT transistors of the power equalization circuit.

[0065] Specifically, the input to the fourth PI controller is the reference value of the energy storage inductor current and the energy storage inductor current value I of the power balancing circuit. L The deviation is output as the duty cycle d of the PWM modulated wave, which is then used by a square wave generator to generate the PWM modulated wave signal.

[0066] Depending on the output power of the DC fans, the power balancing unit 10 can operate in two modes, each containing two operating states, distinguished by the switching state of Q1 or Q2. When the output power of DC fan 1 is greater than that of DC fan 2, Q2 is off: 1) Q1 is on, with a current loop of C1-Q1-L-C1, and power is stored in the energy storage inductor L; 2) Q1 is off, and the power stored in the energy storage inductor L is released, with a current loop of L-Q2 bypass thyristor-C2-L. When the output power of DC fan 1 is less than that of DC fan 2, Q1 is off: 1) Q2 is on, with a current loop of C2-L-Q2-C2, and power is stored in the energy storage inductor L; 2) Q2 is off, and the power stored in the energy storage inductor L is released, with a current loop of L-Q1 bypass thyristor-C1-L.

[0067] The two operating states can be selected by the sign of the operating status signal S, thereby achieving balanced power control and stabilizing the DC bus voltage and the fan output voltage.

[0068] (3) The field-level boost unit 11 is used to boost the voltage and current signals output by the DC wind farm and transmit them to the DC grid 12.

[0069] The field-stage boost unit 11 is a dual active bridge (DAB) converter. For example... Figure 9 As shown, the dual active bridge converter includes a second inductor, an input voltage regulator capacitor, an output voltage regulator capacitor, a low-voltage side IGBT bridge, and a secondary side IGBT bridge.

[0070] This invention uses a configuration software environment to build a DAB converter and complete a two-stage boost (field-level boost). The inductor and capacitor values ​​of the DAB converter are designed based on parameters such as the required power level, output voltage, input voltage, and IGBT switching frequency.

[0071] The second inductance value, input voltage regulator capacitor value, and output voltage regulator capacitor value of the dual active bridge converter are as follows:

[0072]

[0073]

[0074] Among them, L s C is the second inductance value of the dual active bridge converter. inn C is the input voltage regulator capacitor value of the dual active bridge converter. out U is the output voltage regulator capacitor value of the dual active bridge converter, D2 is the phase shift duty cycle of the dual active bridge converter, and U is the phase shift duty cycle of the dual active bridge converter. inn U represents the input voltage of the dual active bridge converter and the output voltage of the DC wind farm. out f is the output voltage of the dual active bridge converter, representing the voltage delivered to the DC power grid 12. s P represents the switching frequency of the IGBTs in a dual active bridge converter (in a dual active bridge converter, the switching frequency of each IGBT is the same). max ΔU is the maximum input power of the dual active bridge converter, n is the transformer turns ratio, and ΔU is the maximum input power of the dual active bridge converter. inn The input voltage ripple of the dual active bridge converter, ΔU out P represents the output voltage ripple of the dual active bridge converter. in This represents the input power of the dual active bridge converter.

[0075] The field-level boost control strategy is used to control the operating state of the field-level boost unit 11 using a control shift ratio strategy.

[0076] like Figure 10 As shown, the process of controlling the operating state of the field-level boost unit 11 using a control shift ratio strategy specifically includes:

[0077] The deviation between the input voltage and the input voltage reference value of the dual active bridge converter is calculated, and a fifth PI controller is used to determine the output current reference value. The deviation between the output voltage and the output voltage reference value of the dual active bridge converter is calculated, and a sixth PI controller is used to determine the current command compensation value. The output current reference value and the current command compensation value are summed to obtain the output current command correction value. The deviation between the output current command correction value and the output current of the dual active bridge converter is calculated, and a seventh PI controller is used to determine the phase shift duty cycle of the dual active bridge converter. Based on the phase shift duty cycle and the switching frequency of the IGBTs of the dual active bridge converter, the signal hysteresis time is determined. Based on the signal hysteresis time and the square wave signal, the switching signal of the IGBT bridge is generated to control the on / off state of the low-voltage side IGBT bridge and the secondary side IGBT bridge of the dual active bridge converter.

[0078] Specifically, the boost ratio of the DAB converter can be controlled by adjusting the phase difference between the IGBT switching signals on the low-voltage and high-voltage sides. The field-level boost control strategy is constructed in Matlab using the DSP configuration software driver library, employing a phase shift control strategy to achieve input and output voltage stability and DC boost.

[0079] First, a voltage outer-loop control strategy is established, including input and output voltage regulation stages. A PI controller is selected as the controller. The input of the fifth PI controller is the input voltage U of the dual active bridge converter. inn With input voltage reference value U inn,ref The deviation is output as the reference value I of the output current. out，ref The input to the sixth PI controller is the output voltage U of the dual active bridge converter. out With output voltage reference value U out,ref The deviation is output as the current command compensation value ΔI. out I out，ref and ΔI out The summation yields the output current command correction value I. * out .

[0080] Then, the current inner-loop control strategy is built: a PI controller is selected, and the input of the seventh PI controller is I. * out With the output current I of the dual active bridge converter out The deviation is output as the phase shift duty cycle D2 of the dual active bridge converter. The phase shift duty cycle is then processed by the gain module 1 / 2f. s The signal hysteresis time D2 / 2f on the high-voltage side relative to the low-voltage side is obtained. sA square wave signal with a duty cycle of 0.5 is processed by a non-modulator to obtain a pair of complementary switching signals G1 and G2 to control the on / off state of the low-voltage side IGBT bridge. The square wave signal is delayed by D2 / 2f. s After a certain time, the secondary side IGBT bridge switching signals G3 and G4 are obtained through the non-module, thereby controlling the on / off state of the secondary side IGBT bridge and realizing DC boost.

[0081] In this invention, the Boost converter and the unit-level boost control strategy serve as a medium-voltage DC / DC converter to complete the unit-level boost, while the DAB converter and the field-level boost control strategy serve as a high-voltage DC / DC converter to complete the field-level boost of the wind farm.

[0082] Step 3: Based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy, perform real-time simulation of the two-stage boost and multi-unit aggregation stages of the DC wind power system.

[0083] Specifically, a discretized simulation step size is set. Based on the discretized simulation step size, the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy, real-time simulation is performed on the two-stage boost and multi-unit aggregation stages of the DC wind power system.

[0084] This invention can serve as a hardware-in-the-loop control system for developing control strategies during the boost and aggregation process of DC wind power systems. It can also provide model support for the development of power electronic components in DC / DC converters. This invention will effectively support the rapid development of control technologies and the verification of control algorithms for DC boost and aggregation processes, thereby saving on technology development cycles and costs.

[0085] like Figure 2 As shown, the present invention also provides a DC wind farm boost-induction simulation platform, comprising: a desktop workstation 1, a digital signal processor 2, and a real-time simulator 3. The desktop workstation 1, the digital signal processor 2, and the real-time simulator 3 jointly construct a HIL co-simulation platform for the characteristics of the DC wind power system boost-induction process.

[0086] The real-time simulator 3 includes a field-programmable gate array board 5 and a central processing unit 4.

[0087] The DSP and FPGA boards are connected via hardwire, directly connected through a connector and wires to complete the communication connection; the FPGA board and CPU are connected via a hardware interface, with the board having a PCIe communication interface directly inserted into the PCIe slot of the real-time emulator 3 to complete the communication connection between the two; the DSP, real-time emulator 3 and desktop workstation 1 are connected via network cable to complete the data transmission.

[0088] The desktop workstation 1 is used to download the main circuit topology model to the field programmable gate array board 5 of the real-time simulator 3, download the unit-level boost control strategy and power balancing control strategy to the central processing unit 4 of the real-time simulator 3, and download the field-level boost control strategy to the digital signal processor 2.

[0089] Since the real-time simulator 3 cannot perform the square wave phase shifting function, a DSP-controlled dual active bridge converter is selected.

[0090] The field-programmable gate array board 5, the central processing unit 4, and the digital signal processor 2 perform real-time simulation of the secondary boost and multi-machine aggregation stages of the DC wind power system based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy.

[0091] Since the hardware industrial controller uses discretization calculation, the control discretization calculation step size is set to 200 microseconds, the simulation step size of the wind turbine mechanical part is 1 second, and the simulation step size of the main circuit topology is 1 microsecond. The backward Euler equation is used to discretize the continuous system, and the step size type is set to fixed step size in the configuration software.

[0092] Specifically, the input and output signals of the FPGA board, CPU, and main circuit topology module are connected via signal mapping between I / O modules in the configuration software to achieve segmentation between different simulation step sizes. Specifically, the simulation step size for the horizontal inflow wind speed and pitch angle of the wind turbine mechanical part in the CPU, as well as the power signal captured by the wind turbine, is 1 second. This power signal is converted into a 1-microsecond step signal through signal mapping between I / O modules and input to the three-phase power source module of the FPGA board. The electrical quantity (voltage, current) signals output from the main circuit topology model in the FPGA board are simulated with a 1-microsecond step size. These electrical quantity signals are converted into a 200-microsecond step signal through signal mapping between I / O modules and input to the field-level boost control strategy in the CPU and DSP. The switching signals output by the field-level boost control strategy are simulated with a 200-microsecond step size. These switching signals are then converted back into a 1-microsecond step signal through signal mapping between I / O modules and input to the main circuit topology model of the FPGA board.

[0093] The I / O module in the configuration software enables input and output between the electrical signals of the main circuit topology model and various control strategies.

[0094] Input / output signals between the FPGA board and the CPU of the real-time emulator 3: Input / output voltage (U) of the FPGA board's output Boost circuit. ini / U oi), the first inductor current (I) of the Boost converter circuit Li ), the energy storage inductor current (I) of the power balancing circuit P L These signals are fed to the CPU of the real-time simulator 3, serving as inputs to the unit-level boost control strategy and power balancing control strategy. Finally, the switching modulation signals of the power balancing circuit and the boost circuit are output to the FPGA board. Additionally, the wind turbine model in the CPU outputs power signals to the FPGA board.

[0095] Input / output signals between the FPGA board and the DSP: Input / output voltage of the FPGA board's DAB circuit (U) inn / U out ) and the DAB circuit output current (I out The signals are fed to the DSP, which serves as the input to the field-level boost control strategy. Finally, the DAB converter switching modulation signals are output to the FPGA board.

[0096] In Real-Time Simulator 3, switches are modeled using the LC method (modeled as a small inductor when closed and a small capacitor when open). Therefore, there is energy loss when the switch state changes: when the switch changes from closed to open, the energy previously stored in the inductor disappears. When the switch changes from open to closed, the energy previously stored in the capacitor disappears.

[0097]

[0098]

[0099] Among them, E loss For the switching losses of real-time simulator 3, E L and E C G is the energy stored in the inductor and capacitor when the switching state changes. i I is the conductance of the switch, Δt is the simulation step size of the real-time simulator 3, and I i V is the input current of the switch. i Let C be the voltage across the switch, C be the equivalent capacitance when the switch is open, and L be the equivalent inductance when the switch is closed.

[0100] According to the above formula, the switching loss in LC modeling is directly proportional to the simulation step size and the switching frequency. Therefore, the simulator parameters can be set according to the following steps: 1. Select a small simulation step size. As can be seen from the loss formula, the simulation step size and switching loss are directly proportional. Therefore, a small simulation step size helps reduce the switching loss caused by the modeling method. 2. Set a reasonable G... iValue. From the formulas for energy storage in inductors and capacitors, it can be seen that a larger switching conductance reduces losses due to inductance, while a smaller conductance reduces losses due to capacitance. 3. Set an appropriate initial value for the turn-off voltage. Setting an appropriate initial voltage for the switch in the off state reduces the energy required to charge the capacitor simulating the off state.

[0101] In this invention, the switching frequency of the medium-voltage DC / DC converter, the high-voltage DC / DC converter, and the power balancing unit is set to 10000Hz, the simulation step size of the electrical part is 1 microsecond, the simulation step size of the control part is 200 microseconds, and the simulation step size of the wind turbine part is 1 second.

[0102] To address the conflicting time scales among the electrical, electromechanical, and control components, this invention integrates a real-time simulator 3 and a DSP to build a hardware-in-the-loop simulation platform. By dividing the simulation step size, the consistency of the platform's overall operation is achieved. Furthermore, by combining different hardware deployments, the boost-and-collection control architecture of a DC wind turbine is reproduced, providing a solution for the state analysis of the entire power generation process of a DC wind turbine and the research on boost-and-collection structure control strategies.

[0103] Furthermore, the overall construction, operation, and control process of the simulation platform of the present invention is as follows:

[0104] (1) DC wind turbine boosting and collection simulation object operation: Download the main circuit topology model and corresponding control strategy built in the workstation configuration software environment to the DSP and real-time simulator 3 to ensure normal communication between the three.

[0105] (2) Overall platform operation sequence: First, start the real-time simulator 3 to establish a communication slave station; then start the DSP to calculate the switching modulation signals of the Boost circuit and the DAB converter according to the initial operating conditions, thereby realizing the DC wind turbine boost and convergence simulation model. The functions of the desktop workstation 1 are to set the parameters of the modulation wave and the main circuit, download the control program and the main circuit, and monitor the status of the simulation platform. The function of the DSP is to run the field-level boost control strategy and output the switching signals of the DAB converter. The function of the real-time simulator 3 is to run the main circuit topology model in the FPGA board, run the unit-level boost control strategy and power equalization control strategy in the CPU, and output the corresponding switching signals.

[0106] In summary, this invention constructs a HIL co-simulation platform for simulating the characteristics of the DC wind farm boost-integration process. The platform's hardware deployment is based on high-performance workstations, a real-time simulator (3), and an industrial rapid prototyping controller. Combined with simulation software (Matlab) and the dynamic characteristic analysis functions provided by power electronics real-time simulation equipment, a simulation platform for the characteristics of the DC wind power system boost-integration process is constructed. A megawatt-level variable-pitch, variable-speed wind turbine model and a DC wind power system boost-integration model are built on the corresponding platforms. Based on this, an HIL simulation platform encompassing the real-time simulator (3), rapid prototyping controller, and high-performance workstation is constructed using the Ethernet communication protocol. By collecting the real-time operating status of the motor and circuit-side objects and combining design control parameters such as unit output power and main circuit parameters, the main control logic under a wide range of operating conditions is constructed. A two-way communication path between devices enables strategy distribution and closed-loop feedback of object operating status. Through unit-level boost control strategies, power balancing control strategies, and farm-level boost control strategies, the control of the DC wind power system's secondary boost and multi-machine integration stages is completed, maintaining the stability of the DC link bus voltage.

[0107] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0108] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A simulation method for DC wind farm boost-and-collection, characterized in that, The DC wind farm boost-and-convergence simulation method includes: A main circuit topology model of a DC wind power system is constructed. This model includes multiple DC wind turbines, a turbine-level boost unit, a power balancing unit, a field-level boost unit, and a DC grid. The turbine-level boost unit boosts the voltage and current signals output by each DC wind turbine. After being boosted at the turbine level, the voltage and current signals from multiple DC wind turbines are cascaded with independent inputs and series outputs to form a DC wind farm. The field-level boost unit boosts the voltage and current signals output by the DC wind farm and transmits them to the DC grid. The power balancing unit is located between the turbine-level and field-level boost units and performs power balancing among the multiple DC wind turbines. The following strategies are defined: a unit-level boost control strategy, a power balancing control strategy, and a field-level boost control strategy. The unit-level boost control strategy uses a constant boost ratio to control the operating state of the unit-level boost unit. The power balancing control strategy controls the operating state of the power balancing unit based on the voltage signal output by the unit-level boost unit. The field-level boost control strategy uses a control shift ratio to control the operating state of the field-level boost unit. Based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy, the two-stage boost and multi-unit aggregation stages of the DC wind power system are simulated in real time.

2. The DC wind farm boost-and-collection simulation method according to claim 1, characterized in that, Each DC wind turbine includes a wind turbine, a permanent magnet synchronous generator, and a rectifier connected in sequence; the output terminal of the rectifier is connected to the input terminal of the unit-level boost unit.

3. The DC wind farm boost-and-collection simulation method according to claim 1, characterized in that, The unit-level boost unit includes multiple boost circuits; each boost circuit is connected to a DC fan to boost the voltage and current signals output by the DC fan at the unit level; the boost circuit includes a first inductor, an input capacitor, an output capacitor, and an IGBT transistor. The first inductor value, input capacitor value, and output capacitor value of the i-th Boost converter are respectively: Among them, L i Let C be the first inductance value of the i-th Boost converter circuit. ini Let C be the input capacitor value of the i-th Boost converter circuit. oi Let D be the output capacitor value of the i-th Boost converter circuit. i U represents the duty cycle of the switching modulation signal of the i-th Boost converter circuit. ini U represents the input voltage of the i-th Boost converter circuit, and U represents the output voltage of the DC fan connected to the i-th Boost converter circuit. oi Let I be the output voltage of the i-th Boost converter. oi f is the output current of the i-th Boost converter. i P is the switching frequency of the IGBT transistor in the i-th Boost converter circuit. i Let ΔU be the input power of the i-th Boost converter. ini Let ΔU be the ripple of the input voltage of the i-th Boost circuit. oi This represents the ripple of the output voltage of the i-th Boost converter.

4. The DC wind farm boost-and-collection simulation method according to claim 3, characterized in that, The process of controlling the operating state of the unit-level boost control unit using a constant boost ratio strategy specifically includes: For any Boost converter circuit, set the boost ratio of the Boost converter circuit; Calculate the product of the input voltage of the Boost converter circuit and the boost ratio to obtain the input voltage of the boost ratio; The deviation between the input voltage of the transformer ratio and the output voltage of the Boost circuit is calculated, and a first PI controller is used to determine the reference value of the inductor current of the Boost circuit. The deviation between the reference value of the inductor current of the Boost boost circuit and the inductor current of the Boost boost circuit is calculated, and a second PI controller is used to determine the duty cycle of the switching modulation signal in order to control the on / off state of the IGBT transistor of the Boost boost circuit.

5. The DC wind farm boost-and-collection simulation method according to claim 3, characterized in that, The power balancing unit includes multiple power balancing circuits; each power balancing circuit is connected to two adjacent Boost circuits to perform power balancing between two adjacent DC fans; each power balancing circuit includes an energy storage inductor and two second IGBTs, one end of the energy storage inductor is connected between the output capacitors of the two Boost circuits, and the other end of the energy storage inductor is connected between the two second IGBTs. The energy storage inductance value of the i-th power balancing circuit is: Among them, L K Let U be the energy storage inductance value of the i-th power balancing circuit. o U is the DC bus voltage. o =U o1 +U o2 +...+U oi U oi Let ε be the output voltage of the i-th Boost converter. i Let n be the peak-to-peak ripple ratio of the energy storage inductor current in the i-th power balancing circuit. f f represents the number of DC fans. b P is the switching frequency of the second IGBT in the power equalization circuit. b This represents the total output power of the DC fan.

6. The DC wind farm boost-and-collection simulation method according to claim 5, characterized in that, The power balancing control strategy controls the operating state of the power balancing unit based on the voltage signal output by the unit-level boost unit. The specific process includes: For any power balancing circuit, calculate the difference in output voltage between the two Boost circuits connected to the power balancing circuit, and use a third PI controller to determine the reference value of the energy storage inductor current of the power balancing circuit. The deviation between the reference value and the value of the energy storage inductor current of the power equalization circuit is calculated, and a fourth PI controller is used to generate a PWM modulation wave signal for the power equalization circuit to control the on / off state of the two second IGBT transistors of the power equalization circuit.

7. The DC wind farm boost-and-collection simulation method according to claim 1, characterized in that, The field-stage boost unit is a dual active bridge converter; the dual active bridge converter includes a second inductor, an input voltage regulator capacitor, an output voltage regulator capacitor, a low-voltage side IGBT bridge, and a secondary side IGBT bridge; The second inductance value, input voltage regulator capacitor value, and output voltage regulator capacitor value of the dual active bridge converter are as follows: Among them, L s C is the second inductance value of the dual active bridge converter. inn C is the input voltage regulator capacitor value of the dual active bridge converter. out U is the output voltage regulator capacitor value of the dual active bridge converter, D2 is the phase shift duty cycle of the dual active bridge converter, and U is the phase shift duty cycle of the dual active bridge converter. inn U represents the input voltage of the dual active bridge converter and the output voltage of the DC wind farm. out f is the output voltage of the dual active bridge converter, representing the voltage delivered to the DC grid. s P is the switching frequency of the IGBT transistors in the dual active bridge converter. max ΔU is the maximum input power of the dual active bridge converter, n is the transformer turns ratio, and ΔU is the maximum input power of the dual active bridge converter. inn The input voltage ripple of the dual active bridge converter, ΔU out This represents the ripple of the output voltage of the dual active bridge converter.

8. The DC wind farm boost-and-collection simulation method according to claim 7, characterized in that, The process of controlling the operating state of the field-level boost unit using a control shift ratio strategy specifically includes: The deviation between the input voltage and the input voltage reference value of the dual active bridge converter is calculated, and the output current reference value is determined using a fifth PI controller. The deviation between the output voltage of the dual active bridge converter and the output voltage reference value is calculated, and the current command compensation value is determined using the sixth PI controller. The output current reference value and the current command compensation value are summed to obtain the output current command correction value; The deviation between the output current command correction value and the output current of the dual active bridge converter is calculated, and the phase shift duty cycle of the dual active bridge converter is determined using a seventh PI controller. The signal hysteresis time is determined based on the phase shift duty cycle of the dual active bridge converter and the switching frequency of the IGBT transistors in the dual active bridge converter. Based on the signal hysteresis time and the square wave signal, a switching signal for the IGBT bridge is generated to control the on / off state of the low-voltage side IGBT bridge and the secondary side IGBT bridge of the dual active bridge converter.

9. The DC wind farm boost-and-collection simulation method according to claim 1, characterized in that, Based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy, real-time simulation is performed on the two-stage boost and multi-unit aggregation stages of the DC wind power system, specifically including: Set the simulation step size for discretization; Based on the discretized simulation step size, the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy, the two-stage boost and multi-unit aggregation stages of the DC wind power system are simulated in real time.

10. A DC wind farm boost-and-collection simulation platform, applied to the DC wind farm boost-and-collection simulation method according to any one of claims 1 to 9, characterized in that, The DC wind farm boost-and-convergence simulation platform includes: a desktop workstation, a digital signal processor, and a real-time simulator; The real-time simulator includes a field-programmable gate array (FPGA) board and a central processing unit (CPU). The desktop workstation is used to download the main circuit topology model to the field programmable gate array board of the real-time simulator, download the unit-level boost control strategy and power balancing control strategy to the central processing unit of the real-time simulator, and download the field-level boost control strategy to the digital signal processor. The field-programmable gate array board, the central processing unit, and the digital signal processor perform real-time simulation of the secondary boost and multi-machine aggregation stages of the DC wind power system based on the main circuit topology model, the unit-level boost control strategy, the power balancing control strategy, and the field-level boost control strategy.

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