Multi-stage configuration and robust control strategy system based on power regulation of wind driven generator

Abstract

The invention discloses a multi-stage configuration and robust control strategy system based on power regulation of a wind driven generator. The multi-stage configuration and robust control strategy system comprises a first-stage configuration module, a second-stage configuration module and a direct-current bus connected between the first-stage configuration module and the second-stage configuration module. According to the multi-stage configuration and robust control strategy system based on wind driven generator power regulation disclosed by the invention, the control target of the first stage is to realize the maximum power point operation of a vertical axis wind driven generator and stabilize the voltage of a direct current bus; the control target of the second stage is to reduce the influence of fundamental waves and higher harmonics and adjust the level of the output split-phase voltage at the same time.

Description

Technical Field

[0001] This invention belongs to the technical field of vertical axis wind turbine power regulation systems, specifically relating to a multi-level configuration and robust control strategy system based on wind turbine power regulation. Background Art

[0002] Currently, various renewable energy sources (RES) such as solar energy, energy storage batteries, and wind turbines are common renewable energy sources and are integrated into AC / DC microgrid systems. In wind energy development, the most commonly used renewable energy source is the horizontal axis wind turbine (HWT), and power regulation systems used in AC / DC microgrid systems are mostly based on horizontal axis wind turbines.

[0003] Currently, the commonly used grid-side inverter topology is the three-phase voltage source inverter, while single-phase voltage source inverters employ full-bridge inverters. In low-voltage residential applications such as North America, split-phase voltage is more ideal. Other common inverter topologies include HERIC and full-bridge inverters, but these are primarily used for single-phase voltage levels. The adoption of split-phase inverter topologies and their control mechanisms to meet the needs of split-phase residential users is receiving increasing attention.

[0004] When wind turbines transfer energy from renewable energy sources to phased loads in AC distribution systems, multiple AC / DC and DC / AC phases are involved. Properly selecting the DC / DC converter and DC / AC inverter topologies and their control strategies for each phase is crucial for smoothly transferring power from the source to the load under any transient or source / load disturbances. Achieving maximum power point tracking (MPPT) for vertical-axis wind turbines is also an important and critical control objective. Summary of the Invention

[0005] The main objective of this invention is to provide a multi-level configuration and robust control strategy system based on wind turbine power regulation. It offers a complete topology including a robust control strategy for efficiently transferring energy from the source to the load, applicable to power regulation systems of vertical axis wind turbines and split-phase inverters. This process is referred to as the Vertical Axis Wind Power Regulation System (VAWT-PCS). The control strategy ultimately regulates different voltage levels and reduces total harmonic distortion.

[0006] Another objective of this invention is to provide a multi-level configuration and robust control strategy system based on wind turbine power regulation. The control objective of the first stage is to achieve maximum power point operation of the vertical axis wind turbine and stabilize the DC bus voltage. The control objective of the second stage is to reduce the influence of fundamental and higher harmonics, while adjusting the level of the output phase voltage.

[0007] To achieve the above objectives, this invention provides a multi-level configuration and robust control strategy system based on wind turbine power regulation, including a first-stage configuration module, a second-stage configuration module, and a DC bus (DC electrical bus) connected between the first-stage configuration module and the second-stage configuration module, wherein:

[0008] The first-stage configuration module includes a vertical axis wind turbine, a permanent magnet synchronous generator (PMSG), an (AC / DC) rectifier, an input (LC) filter, a first-stage (DC / DC) boost converter, a battery, and a second-stage (DC / DC) boost converter, connected in sequence. The control objective of the first-stage configuration module is to achieve maximum power point operation of the vertical axis wind turbine and stabilize the voltage of the DC bus.

[0009] The second-stage configuration module includes a DC balancing capacitor, a split-phase inverter, and an output filter. The control objective of the second-stage configuration module is to reduce the influence of the fundamental frequency and higher harmonics, while adjusting the level of the output split-phase voltage (adjusting the split-phase AC output voltage and suppressing the total harmonic distortion on the AC grid side).

[0010] As a further preferred technical solution to the above technical solution, for the first-stage configuration module:

[0011] The output of the vertical axis wind turbine is connected to the input of a permanent magnet synchronous generator (PMSG), which is used to convert mechanical power into electrical energy.

[0012] The output of the permanent magnet synchronous generator is a three-phase alternating current (AC) signal, which is connected to the anode and cathode terminals of the rectifier with six pulse uncontrolled AC / DC diodes. The rectifier is used to convert the AC signal into a DC signal. The six diodes are arranged in an upper and lower arm configuration, with each arm containing three horizontal diodes. The diodes in the upper arm conduct during the positive half-cycle of the PMSG input voltage, and the diodes in the lower arm conduct during the negative half-cycle of the PMSG input voltage.

[0013] The output of the rectifier is connected to the input of the input filter, which is a low-pass filter used to attenuate frequency components from the rectifier line side (to suppress high-frequency components and provide a smooth DC signal). The cathode of the upper arm of the rectifier is connected to the input of the inductor L1 of the input filter. Inductor L1 limits high-frequency current fluctuations. The output of inductor L1 is connected to the positive terminal of capacitor C1. Capacitor C1 provides a low-impedance path to filter out high-frequency voltage components. The negative terminal of capacitor C1 is connected to the cathode of the lower arm of the rectifier.

[0014] The output of the input filter is connected to the first-stage boost converter to provide maximum power point tracking (MPPT) for the vertical axis wind turbine. By sensing voltage and current from the output of the input filter (through a current sensor and a voltage sensor), the sensed voltage and current are applied to the MPPT algorithm to generate a reference duty cycle. The switching time of the switching device S1 in the first-stage boost converter is controlled by a pulse width modulator, thereby achieving the maximum power output of the vertical axis wind turbine.

[0015] The output of the first-stage boost converter is connected between the positive and negative terminals of the battery via capacitor C2.

[0016] The battery serves as an intermediate point between the first and second stage boost converters, providing stability and improving the power quality of the entire system.

[0017] The battery's output is connected to the input of the second-stage boost converter. The positive terminal of the battery is connected to the boost input inductor L3 of the second-stage boost converter, and the negative terminal of the battery is connected to the switch S2 of the second-stage boost converter. The output of the second-stage boost converter is connected to the DC bus and used to regulate the DC bus voltage. The control objective of the second-stage boost converter is to stabilize the DC bus voltage. The sensed DC bus output voltage is compared with the DC bus reference voltage. Based on the error between the two, the switching duration of the switching device S2 in the second-stage boost converter is controlled by a pulse width modulator. The DC bus used as the DC microgrid is the midpoint between the first-stage configuration module and the second-stage configuration module.

[0018] As a further preferred technical solution to the above technical solution, the positive terminal of the DC bus is connected to the cathode of the diode in the upper arm of the rectifier, the positive terminals of inductors L1, L2, L3, capacitors C1, C2, C3, diodes D1, D2, the positive terminal of the battery, and the upper terminals of control switches S1 and S2, respectively. The negative terminal of the DC bus is connected to the anode of the diode in the lower arm of the rectifier, the negative terminals of capacitors C1, C2, C3, the negative terminal of the battery, and the lower terminals of control switches S1 and S2, respectively.

[0019] As a further preferred technical solution to the above technical solution, for the second-stage configuration module:

[0020] The DC balancing capacitor is connected between the positive and negative terminals of the DC bus voltage and between the DC bus and the split-phase inverter. The midpoint of the DC balancing capacitor is connected to the AC neutral point on the grid side to provide a zero neutral point.

[0021] The split-phase inverter adopts a dual half-bridge configuration. Switches S3 and S4 are used to regulate the positive split-phase voltage, and switches S5 and S6 are used to regulate the negative split-phase voltage. (The dual half-bridge split-phase inverter circuit 302 converts direct current (DC) into high-frequency pulses, which are then passed through the filter inductor L...) sp and capacitor C sp Filtering converts it into a pure sine wave alternating current (AC) output.

[0022] The output of the split-phase inverter has a low-pass output filter. The midpoints of the dual half-bridge switches S3 and S4, and the midpoints of switches S5 and S6 are each connected to a filter inductor L. sp One end, filter inductor L sp The output terminal is connected to the filter capacitor C. sp The input terminal is used to attenuate high-frequency components, and the output terminal of the output filter generates a voltage level V. sp1 V sp2 and V sp3 (304);

[0023] The phase voltage and current are sensed at the output of the output filter. The sensed phase voltage and current are fed back and sent to the corresponding controller (including pulse width modulator) to control the switching duration of switches S3 and S4 to adjust the phase voltage of the first line. At the same time, the phase voltage of the second line is adjusted by switches S5 and S6 (these four switches are connected in an H-type configuration to form a dual half-bridge inverter).

[0024] As a further preferred technical solution to the above technical solution, the maximum power point operation of the vertical axis wind turbine is achieved through a first-stage boost converter, specifically implemented as follows:

[0025] The maximum electrical power of the hill-climbing algorithm directly affects the mechanical power through the following mathematical expression:

[0026] P m =ω m .T m ;

[0027] Among them, P m It is mechanical power, ω m It is angular velocity (radians per second, rad / s), T m It is mechanical torque (Newton-meter, N·m). N is the rotational speed, measured in revolutions per minute (RPM), and T is the rotational speed. m It is mechanical torque, and its expression is:

[0028]

[0029] Where: ρ is the air density (kilograms per cubic meter, kg / m³) 3 A is the swept area of ​​the wind turbine (πr). 2 square meters, m 2 ), C p is the power factor (wind turbine efficiency, typically 20%-30% for vertical axis wind turbines), and v is the wind speed (meters per second, m / s);

[0030] Ultimately, the mechanical torque transmitted to the generator shaft is converted into electrical power through the generator's electromechanical conversion, and the relationship is as follows:

[0031] P e =ηP m ;

[0032] Among them, P e =P wt It is the electrical power output (watts, W), P wt For sensing current I wt and voltage V wt The product of η and η is the efficiency of the permanent magnet synchronous generator (PMSG) (typically 90%-98%).

[0033] As a further preferred technical solution to the above technical solution, the voltage stability of the DC bus is achieved through a second-stage boost converter, specifically implemented as follows:

[0034] Open-loop control To output transfer function G vd Given by the following expression:

[0035]

[0036] in: s is the complex variable in the Laplace transform; VBA represents the battery voltage, which serves as the input voltage of the second-stage boost converter; VDCbus is the output DC bus voltage regulated by the control transfer function Gvd of the second-stage boost converter.

[0037] ω o It is a bipolar frequency.

[0038] Q is the quality factor.

[0039] d′=1-d is the on-duty cycle of switch S2, and d′=1-d is the off-duty cycle of switch S2, used for pulse width modulation. T ON It is the conduction time of the pulse, and T is the total period of the pulse;

[0040] ω ZIt is the ESR zero point;

[0041] ω RHP-zero It is the zero point of the right half-plane.

[0042] R L It is the load resistor;

[0043] In the above formula, G vd The open-loop transfer function represents the second-stage boost converter, and the second-order function Δ(s) shown in the denominator contains positive parameters;

[0044] Open-loop transfer function G vd By using a compensator to close the loop, where:

[0045] The mathematical expression for the compensator is:

[0046]

[0047] A 3-pole 2-zero compensator Hv(s) is used to optimize the robust dynamic performance and stability of the second-stage boost converter to regulate the output side of the second boost converter connected to the DC bus;

[0048] An integrator ωI is placed at the origin to provide zero steady-state error; the pole ωp1 of the compensator is used to cancel G. vd The first zero, ωp2, is used to provide additional switching ripple attenuation; the two zeros, ωz1 and ωz2, are placed close to G. vd ω o Positioning is crucial for maximizing gain and system stability.

[0049] As a further preferred technical solution to the above technical solution, the second-stage configuration module is specifically implemented as follows:

[0050] A split-phase inverter divides the output AC signal into two paths, which are delayed and reversed by 180 degrees relative to each other, thereby generating V. sp1 、V sp2 V, and the combination of the two sp3 In the split-phase inverter circuit, the switches S3, S4 and S5, S6 of the two bridge arms switch according to a specific timing sequence to achieve voltage reversal and output. At the same time, the output waveform is controlled and optimized by adjusting the duty cycle and switching frequency of switches S3, S4 and S5, S6.

[0051] The split-phase inverter uses a proportional-integral repetitive controller for processing. In the proportional-integral repetitive controller, the inner loop current control F... i,sp Used to suppress harmonics on the grid side, outer loop voltage control F v,sp Used to regulate phase voltage, wherein:

[0052] The transfer function of the repetitive controller in the discrete domain is expressed as:

[0053]

[0054] Among them, K r z m S(z) is a compensator used for amplitude and phase compensation, K r It is the gain of the repetitive controller; z m is a leading element used to compensate for phase delay; S(z) is a low-pass filter used to filter out high-frequency interference components; Q(z) is a filter constant used to overcome inaccuracies in the object model and enhance the robustness of the system; N is an integer defined as f s / f g f s It is the sampling frequency, f g It represents the fundamental frequency of the power grid; z represents the z-domain variable, which is the complex frequency variable used in the Z-transform; z -N This indicates a signal delay of N sampling points;

[0055] The mathematical formula for proportional-integral control is expressed as:

[0056]

[0057] Among them, K p and K i These are the proportional and integral gains, G. pi The discretization of (s) is obtained by the Euler method and is expressed as G. pi (z);

[0058] The proportional-integral and repetitive control of the inner-loop parallel structure is defined as follows:

[0059]

[0060] Among them, z -1 The processing and pulse width modulation delay are represented by F(z); F(z) is the phase filter inductance L of the output filter. sp The transfer function is discretized using a bilinear transform, as shown below:

[0061]

[0062] in, It is the sampling period, f s It is the sampling frequency;

[0063] The control objective of the internal current loop is to suppress grid harmonics through proportional-integral and repetitive control in a parallel structure.

[0064] Proportional-integral control is used as the outer loop voltage circuit to achieve phase voltage stability. The formula is as follows:

[0065]

[0066] Among them, V sp It is the phase voltage, V sp * This is a reference value for the phase voltage;

[0067] Among them, C sp It is a filter capacitor, connected to the filter inductor L. sp One end, K P and K I These are proportional gain and integral gain;

[0068] The overall closed-loop discrete transfer function after closing the outer loop voltage loop and the inner current loop is expressed as:

[0069]

[0070] Among them, G pv It is a proportional-integral controller for the outer loop voltage circuit, used to regulate the phase voltage V. sp1 and V sp2 Defined as:

[0071]

[0072] in, It is the output-side phase-splitting filter capacitor C. sp The transfer function is defined as:

[0073]

[0074] Among them, C sp is the filter capacitor, and s is the complex variable in the Laplace transform;

[0075] Inner loop current control F i,sp and outer loop voltage control F v,sp In the closed loop, the signal is compared with the pulse width modulation technique to generate a reference duty cycle signal to turn the half-bridge phase switches S3, S4, S5, and S6 on / off. This suppresses total harmonic distortion and regulates the phase voltage by using the internal current controller, which is also the goal of the external voltage loop control.

[0076] Phase voltage V sp1 The voltage is regulated by the first inverter half-bridge arm switches S3 and S4 through a closed-loop voltage control strategy.

[0077] Phase voltage V sp2 The voltage is regulated by the second inverter half-bridge arm switches S5 and S6 through a closed-loop voltage control strategy.

[0078] V sp1 and V sp2 The combination generates phase-separated AC voltage levels V sp3 . Attached Figure Description

[0079] Figure 1a This is a block diagram of the complete Vertical Axis Wind Turbine Power Regulation System (VAWT-PCS);

[0080] Figure 1b It is a schematic diagram of a vertical axis wind turbine power regulation system, including detailed views of sub-components, topology and other components in each configuration;

[0081] Figure 2a This is the control block diagram of the first-stage DC / DC boost converter, used to achieve maximum power point tracking of the vertical axis wind turbine.

[0082] Figure 2b This is a flowchart of the maximum power point tracking algorithm for vertical axis wind turbines during ramp climbing;

[0083] Figure 3 This is a block diagram of the second-stage DC / DC boost converter, which includes different feedforward-hysteresis compensation control components for regulating the DC bus voltage;

[0084] Figure 4a The block diagram of the proportional-integral-repetitive controller (PI-RC) for a phase-to-phase DC / AC inverter is shown.

[0085] Figure 4b An internal view of the PI-RC controller parameters is shown, which is used to suppress total harmonic distortion on the line side and acts on the inner loop current loop;

[0086] Figure 4c The internal view of the proportional-integral controller is shown, used for regulating the phase voltage in the outer loop voltage circuit. Detailed Implementation

[0087] The following description is intended to disclose the present invention so that those skilled in the art can implement the present invention. The preferred embodiments described below are for illustrative purposes only, and those skilled in the art will readily appreciate other obvious variations. The basic principles of the present invention defined in the following description may be applied to other embodiments, variations, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the present invention.

[0088] In the preferred embodiments of the present invention, those skilled in the art should note that the wind turbines and the like involved in the present invention can be considered as prior art.

[0089] Preferred embodiment.

[0090] This invention discloses a multi-level configuration and robust control strategy system based on wind turbine power regulation, including a first-stage configuration module 100, a second-stage configuration module 300, and a DC bus 200 (DC electrical bus) connected between the first-stage configuration module 100 and the second-stage configuration module 300, wherein:

[0091] The first-stage configuration module 100 includes a vertical-axis wind turbine generator 101 (i.e., a wind turbine), a permanent magnet synchronous generator (PMSG) 102, an AC / DC rectifier 103, an input (LC) filter 104, a first-stage (DC / DC) boost converter 105, a battery 106, and a second-stage (DC / DC) boost converter 107 connected in sequence. The control objective of the first-stage configuration module 100 is to achieve maximum power point operation of the vertical-axis wind turbine generator and stabilize the voltage of the DC bus.

[0092] The second-stage configuration module 300 includes a DC balancing capacitor 301, a phase-splitting inverter 302, and an output filter 303. The control objective of the second-stage configuration module 300 is to reduce the influence of the fundamental frequency and higher harmonics, while adjusting the level of the output phase-splitting voltage (adjusting the phase-splitting AC output voltage and suppressing the total harmonic distortion on the AC grid side).

[0093] Specifically, for the first-stage configuration module 100:

[0094] The output of the vertical axis wind turbine 101 is connected to the input of a permanent magnet synchronous generator (PMSG), which is used to convert mechanical power into electrical energy.

[0095] The output of the permanent magnet synchronous generator 102 is a three-phase alternating current (AC) signal, which is connected to the anode and cathode terminals of the rectifier 103, which consists of six pulsed uncontrolled AC / DC diodes. The rectifier 103 is used to convert the AC signal into a DC signal. The six diodes are arranged in an upper and lower arm configuration, with each arm containing three horizontal diodes. The diodes in the upper arm conduct during the positive half-cycle of the PMSG input voltage, and the diodes in the lower arm conduct during the negative half-cycle of the PMSG input voltage.

[0096] The output of rectifier 103 is connected to the input of input filter 104, which is a low-pass filter used to attenuate frequency components from the path side of rectifier line 103 (to suppress high-frequency components and provide a smooth DC signal). The cathode of the upper arm of rectifier 103 is connected to the input of inductor L1 of input filter 104. Inductor L1 limits high-frequency current fluctuations. The output of inductor L1 is connected to the positive terminal of capacitor C1, which provides a low-impedance path to filter out high-frequency voltage components. The negative terminal of capacitor C1 is connected to the cathode of the lower arm of rectifier.

[0097] The output of the input filter 104 is connected to the first-stage boost converter 105, as follows: Figure 2a As shown, 400 represents the entire process used to provide maximum power point tracking (MPPT) for the vertical axis wind turbine 101; by sensing voltage and current from the output of the input filter 104 (through a current sensor and a voltage sensor), the sensed voltage and current are applied to the maximum power point tracking (MPPT) algorithm 402 to generate a reference duty cycle, and the switching time of the switching device S1 in the first-stage boost converter 105 is controlled by the pulse width modulator 403, thereby achieving the maximum power output of the vertical axis wind turbine 101;

[0098] The output of the first-stage boost converter 105 is connected between the positive and negative terminals of the battery 106 via capacitor C2;

[0099] Battery 106 is the midpoint between the first-stage and second-stage boost converters. Battery 106 provides stability and improves the power quality of the entire system.

[0100] The output terminal of battery 106 is connected to the input terminal of the second-stage boost converter 107. The positive terminal of battery 106 is connected to the boost input inductor L3 of the second-stage boost converter 107, and the negative terminal of battery 106 is connected to the switch S2 of the second-stage boost converter 107. The output terminal of the second-stage boost converter 107 is connected to the DC bus 200 and used to regulate the DC bus voltage. The control objective of the second-stage boost converter 107 is to stabilize the DC bus voltage. The sensed DC bus output voltage is compared with the DC bus reference voltage. Based on the error between the two, the switching duration of the switching device S2 in the second-stage boost converter is controlled by a pulse width modulator. The DC bus used as a DC microgrid is the midpoint between the first-stage configuration module and the second-stage configuration module.

[0101] More specifically, the positive terminal of the DC bus 200 is connected to the cathode of the diode in the upper arm of the rectifier, the positive terminals of inductors L1, L2, L3, capacitors C1, C2, C3, diodes D1, D2, the positive terminal of the battery, and the upper terminals of control switches S1 and S2, respectively. The negative terminal of the DC bus is connected to the anode of the diode in the lower arm of the rectifier, the negative terminals of capacitors C1, C2, C3, the negative terminal of the battery, and the lower terminals of control switches S1 and S2, respectively.

[0102] Furthermore, regarding the second-stage configuration module 300:

[0103] The DC balancing capacitor 301 is connected between the positive and negative terminals of the DC bus voltage and between the DC bus and the split-phase inverter 302. The midpoint of the DC balancing capacitor 301 is connected to the AC neutral point on the grid side to provide a zero neutral point.

[0104] The split-phase inverter 302 adopts a dual half-bridge configuration. Switches S3 and S4 of the split-phase inverter 302 are used to regulate the positive split-phase voltage, and switches S5 and S6 are used to regulate the negative split-phase voltage. (The dual half-bridge configuration of the split-phase inverter circuit 302 converts direct current (DC) into high-frequency pulses, which are then passed through the filter inductor L.) sp and capacitor C sp Filtering converts it into a pure sine wave alternating current (AC) output.

[0105] The output of the split-phase inverter 302 has a low-pass output filter 303. The midpoints of the dual half-bridge arm switches S3 and S4, and the midpoints of the switches S5 and S6 are each connected to a filter inductor L. sp One end, filter inductor L sp The output terminal is connected to the filter capacitor C. sp The input terminal is used to attenuate high-frequency components, and the output terminal of the output filter generates a voltage level V. sp1 、V sp2 and V sp3 (304);

[0106] The phase voltage and current are sensed at the output terminal of the 303 output filter. The sensed phase voltage and current are fed back and sent to the corresponding controller (including pulse width modulator) to control the switching duration of switches S3 and S4 to adjust the phase voltage of the first line. At the same time, the phase voltage of the second line is adjusted by switches S5 and S6 (these four switches are connected in an H-type configuration to form a dual half-bridge inverter).

[0107] Output filter 303 is connected between the midpoint switching arms of the split-phase (dual half-bridge) inverter (DBI) to generate multiphase AC output voltage. The first phase half-bridge arm switching pair is connected to the output filter to generate a smooth positive AC output voltage level; the second phase half-bridge arm switching pair is connected to its respective output filter to generate a smooth negative AC output voltage level, which is actually 180 degrees out of phase with the first phase output voltage level of the dual half-bridge inverter; the combination of the output lines of the split-phase filters generates a third AC voltage level, which is the superposition of the first and second phase voltage levels. The combination of Vsp1 and Vsp2 generates split-phase AC voltage level 3, Vsp3.

[0108] The control strategy of the dual half-bridge split-phase inverter 302 is to regulate the AC split-phase voltage and reduce the total harmonic distortion on the grid side. Proportional-integral (PI) and repetitive control (RIC) are used to implement the second configuration of the vertical-axis wind turbine power regulation system. The parallel-structure PIC / RIC exhibits strong performance in both transient and steady-state conditions. The output of the parallel-structure control network is used to modulate the pulse-width modulation (PWM) signal and send it to the corresponding half-bridge switch of the split-phase inverter. The output filter outputs the split-phase current i on the output side. sp1 / i sp2 The current is sensed and compared with a reference grid current. The first loop is the inner loop current, used to suppress total harmonic distortion. The phase voltage V sp1 / V sp2 The corresponding half-bridge LC filter is sensed and compared with the reference grid voltage value. The proportional-integral (PI) controller is used as a second control strategy to regulate multiple phase voltage levels. The output of the PI controller includes pulse width modulation signals, which are used to regulate the corresponding half-bridge inverter arm switches S3 and S4 to regulate the positive phase voltage, and S5 and S6 for the negative phase voltage. This constitutes the control objective and control strategy of the second configuration of the vertical axis wind turbine power regulation system.

[0109] Furthermore, such as Figure 2a As shown, the input current I wt and voltage V wt Sensing is performed by sensor device 401, and the maximum power point operation of the vertical axis wind turbine is achieved through the first-stage boost converter 105. Specifically, the implementation is as follows:

[0110] The maximum electrical power of the hill-climbing algorithm (i.e., MPPT algorithm 402) directly affects the mechanical power through the following mathematical expression:

[0111] P m =ω m .T m ;

[0112] Among them, Pm It is mechanical power, ω m It is angular velocity (radians per second, rad / s), T m It is mechanical torque (Newton-meter, N·m). N is the rotational speed, measured in revolutions per minute (RPM), and T is the rotational speed. m It is mechanical torque, and its expression is:

[0113]

[0114] Where: ρ is the air density (kilograms per cubic meter, kg / m³) 3 A is the swept area of ​​the wind turbine (πr). 2 square meters, m 2 ), C p is the power factor (wind turbine efficiency, typically 20%-30% for vertical axis wind turbines), and v is the wind speed (meters per second, m / s);

[0115] Ultimately, the mechanical torque transmitted to the generator shaft is converted into electrical power through the generator's electromechanical conversion, and the relationship is as follows:

[0116] P e =ηP m ;

[0117] Among them, P e =P wt It is the electrical power output (watts, W), P wt For sensing current I wt and voltage V wt The product of η and η is the efficiency of the permanent magnet synchronous generator (PMSG) (typically 90%-98%).

[0118] Finally, the electric power (Pe) at the maximum power point is obtained through a ramp-up algorithm, such as... Figure 2b As shown. With the help of parameters such as Δp and ΔI, the reference duty cycle is generated by the pulse width modulator (PWM). The PWM signal is finally sent to switch S1 of the first-stage converter to achieve the maximum electrical power (Pe).

[0119] Pe and P m The conversion relationship between them:

[0120] This is the relationship between mechanical power and electrical power, because the maximum power obtained through the first-stage boost converter is electrical power (watts, W). Figure 2b The flowchart shown is the maximum power point algorithm for electrical power.

[0121] Preferably, the control objective of the second-stage boost converter 107 is to stabilize the DC bus voltage. The sensed DC bus output voltage is compared with the DC bus reference voltage. Based on the error between the two, the system may further include a pulse width modulator for controlling the on / off duration of the switching device S2 in the second-stage DC / DC boost converter. (See also...) Figure 3 The control block diagram is a closed-loop control system, including different control elements of the second-stage boost converter 107. Compared with the traditional proportional-integral control method, lag-feedforward compensation control is a robust control strategy because it can accurately control system dynamics and meet transient and steady-state requirements. The control transfer function G... vd A pulse width modulation signal will be generated to control the switch S2 of the second-stage boost converter. The closed-loop hysteresis-feedforward compensation control strategy 500 is applicable to the DC electrical bus, which also serves as a DC microgrid to ensure system stability under any transient or step load changes. The voltage stabilization of the DC bus is achieved through the second-stage boost converter, specifically implemented as follows:

[0122] Open-loop control To output transfer function G vd 501 is given by the following expression:

[0123]

[0124] in: s = σ + jω, where s is the complex variable in the Laplace transform (the symbol '^' represents the perturbation value used in small-signal analysis); VBA represents the battery voltage, which serves as the input voltage of the second-stage boost converter; VDCbus is the output DC bus voltage regulated by the control transfer function Gvd of the second-stage boost converter.

[0125] ω o It is a bipolar frequency.

[0126] Q is the quality factor.

[0127] d′ = 1 - d is the on-duty cycle of switch S2, and d′ = 1 - d is the off-duty cycle of switch S2, used for pulse width modulation (PWM). T ON It is the conduction time of the pulse, and T is the total period of the pulse;

[0128] ω Z It is the ESR zero (which can be ignored because its frequency is much higher than the bipolar frequency and the right half-plane zero (RHP-zero)). Z =r c / C3,r c (Represents the parasitic resistance of the capacitor);

[0129] ω RHP-zero It is the zero point of the right half-plane (RHP).

[0130] R L It is the load resistance (in this case, the DC bus 200);

[0131] In the above formula, G vd The open-loop transfer function represents the second-stage boost converter. The second-order function Δ(s) shown in the denominator contains positive parameters (meaning that the open-loop poles of the system can be real or complex and are always located in the left half-plane (LHP). The poles in the LHP ensure the stability of the system).

[0132] Open-loop transfer function G vd By using a (hysteresis-leading or zero-pole) compensator to close the loop (to regulate the DC bus), where:

[0133] The mathematical expression for the (zero-pole) compensator (502) is as follows:

[0134]

[0135] A 3-pole 2-zero compensator Hv(s) is used to optimize the robust dynamic performance and stability of the second-stage boost converter to regulate the output side of the second boost converter connected to the DC bus;

[0136] An integrator ωI is placed at the origin to provide zero steady-state error; the pole ωp1 of the compensator is used to cancel G. vd The first zero, ωp2, is used to provide additional switching ripple attenuation; the two zeros, ωz1 and ωz2, are placed close to G. vd ω o Positioning to achieve maximum gain and system stability (see [reference]). Figure 3 The diagram shows the small-signal block diagram of system 500, where the voltage loop is closed 504. The mathematical expression for the closed-loop voltage loop 504 is: Tvo = -FmHvGvd, where Fm is the sensing gain 503.

[0137] Preferably, the second-stage configuration module is specifically implemented as follows:

[0138] A split-phase inverter divides the output AC signal into two paths, which are delayed and reversed by 180 degrees relative to each other, thereby generating V. sp1 、V sp2 V, and the combination of the two sp3In the split-phase inverter circuit, the switches S3, S4 and S5, S6 of the two bridge arms switch according to a specific timing sequence to achieve voltage reversal and output. At the same time, the output waveform is controlled and optimized by adjusting the duty cycle and switching frequency of switches S3, S4 and S5, S6.

[0139] (See also) Figure 4a This demonstrates the complete control strategy of a split-phase dual half-bridge inverter. The control design goal is to reduce total harmonic distortion and stabilize the output voltage under any disturbance. The split-phase inverter uses a proportional-integral repetitive controller for processing. (The repetitive controller is based on an internal model principle. The mathematical model of this controller includes the external input signal, which can achieve high-precision output and eliminate steady-state error. Theoretically, it can track the input signal without static error. The repetitive control employs...) As an internal model, it can simultaneously contain fundamental and all harmonic models, with the characteristic equation being 1-e -Ts =0, the characteristic roots are 0, ±ω, ±2ω, ±3ω......., these roots are all distributed on the imaginary axis, the internal model has infinite gain at each harmonic frequency, therefore, theoretically it is possible to achieve perfect steady-state control performance of the split-phase DC / AC inverter system 302), in the proportional-integral repetitive controller, the inner loop current control F i,sp 600 is used to suppress harmonics on the grid side, and the outer loop voltage control F v,sp 700 is used to regulate the phase voltage, where:

[0140] The transfer function of the repetitive controller in the discrete domain is expressed as:

[0141]

[0142] Among them, K r z m S(z) is a compensator used for amplitude and phase compensation, K r It is the gain of the repetitive controller; z m is a leading element used to compensate for phase delay; S(z) is a low-pass filter used to filter out high-frequency interference components; Q(z) is a filter constant used to overcome inaccuracies in the object model and enhance the robustness of the system; N is an integer defined as f s / f g f s It is the sampling frequency, f g It represents the fundamental frequency of the power grid; z represents the z-domain variable, which is the complex frequency variable used in the Z-transform; z -N This indicates a signal delay of N sampling points;

[0143] The mathematical formula for proportional-integral control is expressed as:

[0144]

[0145] Among them, K p and K i These are the proportional and integral gains, G. pi The discretization of (s) is obtained by the Euler method and is expressed as G. pi (z);

[0146] (like Figure 4b (As shown) The proportional-integral and repetitive control definitions for the inner closed-loop parallel structure (i.e., the inner loop current control F) i,sp )for:

[0147]

[0148] Among them, z -1 The processing and pulse width modulation delay are represented by F(z); F(z) is the phase filter inductance L of the output filter. sp The transfer function is discretized using a bilinear transform, as shown below:

[0149]

[0150] in, It is the sampling period, f s It is the sampling frequency;

[0151] The control objective of the internal current loop is to suppress grid harmonics (phase current i) through a parallel proportional-integral (PI) control and repetitive control 800. sp1 and i sp2 (The phase difference is 180 degrees, and the internal current loop needs to be processed according to this condition);

[0152] A proportional-integral (PI) control 90° is used as the outer loop voltage circuit to achieve phase voltage stabilization. The formula is as follows:

[0153]

[0154] Among them, V sp It is the phase voltage, V sp * This is a reference value for the phase voltage;

[0155] Among them, C sp It is a filter capacitor, connected to the filter inductor L. sp One end, K P and K I These are proportional gain and integral gain;

[0156] (by ignoring i) L The overall closed-loop discrete transfer function after closing the outer loop voltage loop and the inner current loop is expressed as:

[0157]

[0158] Among them, G pv It is a proportional-integral controller for the outer loop voltage circuit, used to regulate the phase voltage V. sp1 and V sp2 Defined as:

[0159]

[0160] in, It is the output-side phase-splitting filter capacitor C. sp The transfer function is defined as:

[0161]

[0162] Among them, C sp is the filter capacitor, and s is the complex variable in the Laplace transform;

[0163] Inner loop current control F i,sp 600 and outer loop voltage control F v,sp The 700 loop is closed, and the signal is compared with the pulse width modulation (PWM) technique to generate a reference duty cycle signal to turn the half-bridge phase switches S3, S4, S5, and S6 on / off. This suppresses total harmonic distortion (THD) and regulates the phase voltage by using the internal current controller, which is also the goal of the external voltage loop control.

[0164] Phase voltage V sp1 The voltage is regulated by the first inverter half-bridge arm switches S3 and S4 through the closed-loop voltage control strategy 900.

[0165] Phase voltage V sp2 The voltage is regulated by the second inverter half-bridge arm switches S5 and S6 through the closed-loop voltage control strategy 900.

[0166] V sp1 and V sp2 The combination generates phase-separated AC voltage levels V sp3 .

[0167] It is worth mentioning that the technical features of wind turbines and other technologies involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0168] For those skilled in the art, it is still possible to modify the technical solutions described in the aforementioned embodiments, or to make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-level configuration and robust control strategy system based on wind turbine power regulation, characterized in that: The system comprises a first-stage configuration module, a second-stage configuration module, and a DC bus connected between the first-stage configuration module and the second-stage configuration module, wherein: The first-stage configuration module includes a vertical axis wind turbine, a permanent magnet synchronous generator, a rectifier, an input filter, a first-stage boost converter, a battery, and a second-stage boost converter connected in sequence, and the control objective of the first-stage configuration module is to achieve maximum power point operation of the vertical axis wind turbine and stabilize the voltage of the DC bus; The second stage configuration module includes a DC balancing capacitor, a phase-splitting inverter and an output filter. The control target of the second stage configuration module is to reduce the influence of fundamental waves and higher harmonics, and adjust the level of the output phase-splitting voltage.

2. A multi-level configuration and robust control strategy system based on wind turbine power regulation according to claim 1, characterized in that: For the first stage configuration module: The output of the vertical axis wind turbine is connected to the input of a permanent magnet synchronous generator, which is used to convert mechanical power into electrical energy; The output end of the permanent magnet synchronous generator is a three-phase AC signal, which is connected to the anode and cathode ends of the rectifier of the six-pulse uncontrolled AC / DC diodes, and the rectifier is used to convert the AC signal into a DC signal. The six diodes are divided into upper and lower arm configurations, and each arm contains three horizontal diodes, wherein the diodes of the upper arm are turned on in the positive half cycle of the PMSG input voltage, and the diodes of the lower arm are turned on in the negative half cycle of the PMSG input voltage; The output end of the rectifier is connected to the input end of the input filter. The input filter is a low-pass filter used to attenuate the frequency components from the line side of the rectifier. The cathode end of the upper arm of the rectifier is connected to the input end of the inductor L1 of the input filter. The inductor L1 limits high-frequency current fluctuations. The output end of the inductor L1 is connected to the positive end of the capacitor C1. The capacitor C1 provides a low-impedance path to filter out high-frequency voltage components. The negative end of the capacitor C1 is connected to the cathode end of the lower arm of the rectifier. The output of the input filter is connected to a first-stage boost converter for providing maximum power point tracking for the vertical axis wind turbine; By sensing the voltage and current from the output terminal of the input filter, applying the sensed voltage and current to a maximum power point tracking algorithm, generating a reference duty cycle, and controlling the switching time of the switching device S1 in the first-stage boost converter through a pulse width modulator, thereby achieving the maximum power output of the vertical axis wind turbine; The output of the first-stage boost converter is connected between the positive and negative terminals of the battery through capacitor C2; The battery is the midpoint between the first and second stage boost converters, providing stability and improving the power quality of the entire system; The output end of the battery is connected to the input end of the second-stage boost converter, the positive end of the battery is connected to the boost input inductor L3 of the second-stage boost converter, the negative end of the battery is connected to the switch S2 of the second-stage boost converter, the output end of the second-stage boost converter is connected to the DC bus and is used to adjust the DC bus voltage. The control goal of the second-stage boost converter is to stabilize the DC bus voltage. The sensed DC bus output voltage is compared with the DC bus reference voltage. According to the error between the two, the switching time of the switch device S2 in the second-stage boost converter is controlled by the pulse width modulator; the DC bus used as a DC microgrid is the midpoint between the first-stage configuration module and the second-stage configuration module.

3. The multi-level configuration and robust control strategy system based on wind turbine power regulation according to claim 2 is characterized in that: The positive end of the DC bus is respectively connected to the cathode end of the diode of the upper arm of the rectifier, the positive end of the inductors L1, L2, L3, the positive end of the capacitors C1, C2, C3, the diodes D1, D2, the positive end of the battery, and the upper ends of the control switches S1 and S2, and the negative end of the DC bus is respectively connected to the anode end of the diode of the lower arm of the rectifier, the negative end of the capacitors C1, C2, C3, the negative end of the battery, and the lower ends of the control switches S1 and S2.

4. The multi-level configuration and robust control strategy system based on wind turbine power regulation according to claim 3 is characterized in that: For the second stage configuration module: A DC balancing capacitor is connected between the positive end and the negative end of the DC bus voltage and between the DC bus and the split-phase inverter, and a midpoint of the DC balancing capacitor is connected to an AC neutral point on the grid side for providing a zero neutral point; The split-phase inverter adopts a dual half-bridge configuration. The switches S3 and S4 of the split-phase inverter are used to adjust the positive split-phase voltage, and the switches S5 and S6 are used to adjust the negative split-phase voltage; The output end of the split-phase inverter has a low-pass output filter. The midpoint of the dual half-bridge arm switches S3 and S4, and the midpoint of switches S5 and S6 are each connected to a filter inductor L. sp One end of the filter inductor L sp The output terminal is connected to the filter capacitor C sp The input of the filter is used to attenuate high frequency components, and the output of the filter generates a voltage level V sp1 、V sp2 and V sp3 ; The split-phase voltage and current are sensed at the output end of the output filter, and the sensed split-phase voltage and current are fed back and signals are sent to the corresponding controller to control the switching duration of switches S3 and S4 to adjust the split-phase voltage of the first line; at the same time, the split-phase voltage of the second line is adjusted through switches S5 and S6.

5. A multi-level configuration and robust control strategy system based on wind turbine power regulation according to claim 4, characterized in that: The maximum power point operation of the vertical axis wind turbine is achieved through the first stage boost converter, which is specifically implemented as follows: The maximum electrical power of the hill climbing algorithm directly affects the mechanical power through the following mathematical expression: P m =ω m .T m ; Among them, P m is the mechanical power, ω m is the angular velocity, T m is the mechanical torque, N is the rotation speed in revolutions per minute, T m is the mechanical torque, which is expressed as: Where: ρ is the air density, A is the swept area of ​​the wind wheel, C p is the power coefficient, v is the wind speed; Finally, the mechanical torque transmitted to the generator shaft is converted into electrical power through the electromechanical conversion of the generator, and the relationship is: P e =ηP m ; Among them, P e =P wt is the electrical power output, P wt is the sensing current I wt and voltage V wt The product of, η is the efficiency of the permanent magnet synchronous generator.

6. A multi-level configuration and robust control strategy system based on wind turbine power regulation according to claim 5, characterized in that: The voltage stabilization of the DC bus is achieved by the second stage boost converter, which is implemented as follows: Open loop control To output The transfer function G vd It is given by the following expression: in: s=σ+jω, s is a complex variable in Laplace transform; VBA represents the battery voltage, which is the input voltage of the second-stage boost converter; VDCbus is the output DC bus voltage regulated by the control transfer function Gvd of the second-stage boost converter; ω o is the bipolar frequency, Q is the quality factor, is the on-duty cycle of switch S2, d′=1-d is the off-duty cycle of switch S2, used for pulse width modulation, T ON is the on-time of the pulse, T is the total period of the pulse; ω Z is the ESR zero point; ω RHP-zero is the right half plane zero, R L is the load resistance; In the above formula, G vd represents the open-loop transfer function of the second-stage boost converter. The second-order function Δ(s) shown in the denominator contains positive parameters; Open loop transfer function G vd The loop is closed by using a compensator where: The mathematical expression of the compensator is expressed as: A 3-pole 2-zero compensator Hv(s) is used to optimize the robust dynamic performance and stability of the second stage boost converter to regulate the output side of the second boost converter connected to the DC bus; An integrator ωI is placed at the origin to provide zero steady-state error; the compensator pole ωp1 is used to cancel G vd The first zero, ωp2, is used to provide additional switching ripple attenuation; the two zeros, ωz1 and ωz2, are placed close to G vd Omega o position for maximum gain and system stability.

7. The multi-level configuration and robust control strategy system based on wind turbine power regulation according to claim 4 is characterized in that: The second stage configuration module is specifically implemented as follows: The split-phase inverter splits the output AC signal into two paths that are delayed and reversed 180 degrees relative to each other, generating V sp1 、V sp2 And the combination of the two V sp3 ; In the split-phase inverter circuit, the switches S3, S4 and S5, S6 of the two bridge arms are switched according to a specific timing to achieve voltage reversal and output, and the output waveform is controlled and optimized by adjusting the duty cycle and switching frequency of the switches S3, S4 and S5, S6; The split-phase inverter is processed by a proportional-integral repetitive controller. In the proportional-integral repetitive controller, the inner loop current control F i,sp Used to suppress harmonics on the grid side, external loop voltage control F v,sp Used to adjust the phase voltage, where: The transfer function of the repetitive controller in the discrete domain is expressed as: Among them, K r z m S(z) is the compensator for amplitude and phase compensation, K r is the gain of the repetitive controller; z m is a leading element used to compensate for the phase delay; S(z) is a low-pass filter used to filter out high-frequency interference components; Q(z) is a filter constant used to overcome the inaccuracy of the object model and enhance the robustness of the system; N is an integer, defined as f s / f g , f s is the sampling frequency, f g is the grid base frequency; z represents the z-domain variable, which is the complex frequency variable used in the Z-transform; z -N Indicates that the signal is delayed by N sampling points; The mathematical formula of proportional integral control is expressed as: Among them, K p and K i are proportional and integral gains, G pi The discretization of (s) is obtained by Euler method and is represented as G pi (z); The proportional-integral and repetitive control of the inner closed-loop parallel structure is defined as: Among them, z -1 represents the processing and pulse width modulation delay; F(z) is the phase filter inductance L of the output filter sp The transfer function is discretized by bilinear transformation as follows: in, is the sampling period, f s is the sampling frequency; The control objective of the inner current loop is to suppress grid harmonics through proportional-integral and repetitive control of the parallel structure; Proportional integral control is used as the outer loop voltage circuit to achieve phase voltage stability. The formula is: Among them, V sp is the phase voltage, V sp * It is the reference value of the phase voltage; Among them, C sp is the filter capacitor, connected to the filter inductor L sp One end, K P and K I They are proportional gain and integral gain respectively; The overall closed-loop discrete transfer function after the outer voltage loop and the inner current loop are closed is expressed as: Among them, G pv It is a proportional-integral controller of the outer voltage loop, used to adjust the phase voltage V sp1 and V sp2 , defined as: in, is the output side phase filter capacitor C sp The transfer function is defined as: Among them, C sp is the filter capacitor, s is the complex variable in Laplace transform; Inner loop current control F i,sp and the outer loop voltage control F v,sp Being closed loop, the signal will be compared with the pulse width modulation technique to generate a reference duty cycle signal to turn on / off the half-bridge split-phase switches S3, S4, S5, S6, thereby suppressing the total harmonic distortion by using the inner current controller and regulating the split-phase voltage, which is also the goal of the outer voltage loop control; Phase voltage V sp1 It is regulated by the first inverter half-bridge arm switches S3 and S4 through a closed-loop voltage control strategy; Phase voltage V sp2 It is regulated by the second inverter half-bridge arm switches S5 and S6 through a closed-loop voltage control strategy; V sp1 and V sp2 The combination generates a split-phase AC voltage level V sp3 .

Images