Bidirectional ac-dc-ac pwm converter control system based on rt-lab

Abstract

The application discloses a bidirectional AC-DC-AC PWM converter control system based on RT-Lab, which comprises a signal acquisition module, a driving pulse output module and a sampling signal processing module, a control logic switching module, a coordinate transformation module, a grid-side converter control module, a machine-side converter control module, a control signal modulation module and a control pulse output module realized in an RT-lab digital real-time simulation machine; the control logic switching module judges according to a DC-side voltage collected by the signal acquisition module, selects the grid-side converter control module or the machine-side converter control module for control, the grid-side converter control module or the machine-side converter control module calculates an instruction space voltage vector by adopting a preset control strategy, and driving pulses are generated by the control signal modulation module, the control pulse output module and the driving pulse output module to control the grid-side converter or the machine-side converter. The application can quickly and effectively control the bidirectional AC-DC-AC PWM converter.

Description

Technical Field

[0001] This invention belongs to the field of converter control technology, and more specifically, relates to a bidirectional AC-DC-AC PWM converter control system based on RT-Lab. Background Technology

[0002] Bidirectional AC-DC-AC converters are core components of modern power systems, primarily functioning to convert electrical energy into its constituent forms. They are mainly categorized into two types: thyristor-based phase-controlled converters and IGBT (Insulated Gate Bipolar Transistor)-based PWM converters. While phase-controlled converters can handle high voltage and large current, the semi-controlled nature of thyristors (which can only control conduction, not active turn-off) and their low-speed switching operation result in very high harmonic content in the output waveform make them unsuitable for high-frequency, high-precision power conversion applications. In contrast, although PWM converters have lower power density, their use of fully controlled power semiconductor devices allows them to operate at high frequencies. With appropriate control algorithms and inertial systems, they can achieve extremely high control accuracy. PWM converters can output DC voltages with extremely low harmonic content and low peak-to-peak ripple. They can easily achieve sinusoidal AC voltage and current, and also have the ability to flexibly control the AC power factor, thus making the AC side exhibit the characteristics of a controlled current source. Therefore, PWM converters are widely used in applications with high requirements for power output quality, such as wind power generation, solar photovoltaic power generation, electric vehicles, uninterruptible power supplies, and motor control.

[0003] Figure 1 This is a structural diagram of a bidirectional AC-DC-AC PWM converter. (See diagram below.) Figure 1 As shown, the bidirectional AC-DC-AC PWM converter includes a grid-side converter and a generator-side converter. The grid-side converter's function is to invert the DC bus voltage to an AC voltage with stable amplitude and frequency that meets grid connection requirements, based on a stable DC bus voltage level; to rationally control the energy exchange between the DC bus and the grid according to grid demand, thereby improving the power factor at the grid connection point; and to provide a certain capacity of reactive power support to the grid while ensuring the normal operation of the wind turbine generator, thus ensuring the stability of the grid connection point. The main function of the generator-side converter is to improve the generator's operating efficiency and reliability through appropriate control strategies.

[0004] Control strategies for grid-side converters can be broadly categorized into two main types: Vector Control (VC) and Direct Power Control (DPC). Vector Control can be further subdivided into Voltage Oriented Control (VOC) and Virtual Flux Oriented Control (VFOC), both of which are complex to implement. DPC control strategies suffer from drawbacks such as large active and reactive power ripple, inconsistent converter switching frequency, and relatively high current THD.

[0005] Currently, the two most commonly used control strategies for machine-side converters are Field-Oriented Control (FOC) and Direct Torque Control (DTC). However, the FOC control strategy has a complex system structure, while the DTC control strategy results in an irregular switching cycle for the PWM converter, leading to large fluctuations in flux linkage and torque, and it is impossible to simultaneously control both torque and flux linkage.

[0006] Furthermore, current research on bidirectional AC-DC-AC PWM converter control algorithms is usually based entirely on digital simulation platforms. Since digital simulation ignores many details of the real physical system, it can only verify the principle of the control algorithm and cannot accurately reproduce the real physical control system. Therefore, comprehensive research on the hardware system and related control algorithms of bidirectional AC-DC-AC converters based on fast control prototypes is of great significance. However, there is still little research in this field, and industrial applications cannot be realized. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a bidirectional AC-DC-AC PWM converter control system based on RT-Lab. The system uses IGBT as the core controlled element and designs grid-side converter control and machine-side converter control to achieve fast and effective control of the bidirectional AC-DC-AC PWM converter.

[0008] To achieve the above-mentioned objectives, the present invention provides a bidirectional AC-DC-AC PWM converter control system based on RT-Lab, comprising a signal acquisition module, a sampling signal processing module, a control logic switching module, a coordinate transformation module, a grid-side converter control module, a machine-side converter control module, a control signal modulation module, a control pulse output module, and a drive pulse output module. The sampling signal processing module, control logic switching module, coordinate transformation module, grid-side converter control module, machine-side converter control module, control signal modulation module, and control pulse output module are implemented in the RT-Lab digital real-time simulator.

[0009] The signal acquisition module is used to acquire signals from the bidirectional AC-DC-AC converter. The required signals include the grid-side three-phase line voltage signal and grid-side three-phase line current signal of the grid-side converter, the DC-side voltage signal and machine-side three-phase line current signal of the machine-side converter, and the rotor position signal of the permanent magnet synchronous motor. The acquired signals are then sent to the sampling signal processing module.

[0010] The sampling signal processing module is used to process the received grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, machine-side three-phase line current signal, and rotor position signal to obtain the actual values ​​of each signal, namely, grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, machine-side three-phase phase current, and rotor position angle. The stator three-phase phase current is calculated based on the machine-side three-phase phase current. Then, the DC-side voltage is sent to the control logic switching module and the grid-side converter control module. The grid-side three-phase phase voltage, grid-side three-phase phase current, and stator three-phase phase current are sent to the coordinate transformation module, and the rotor position angle is sent to the machine-side converter control module. The specific processing method is as follows:

[0011] For the grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, and machine-side three-phase line current signal, the analog-to-digital converter inside the RT-Lab real-time simulator is used to convert them into digital signals. Then, after amplitude transformation and phase transformation, the actual values ​​of the grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, and machine-side three-phase phase current are obtained. The stator three-phase phase current is calculated based on the machine-side three-phase phase current.

[0012] For the rotor position signal, the actual value of the rotor position angle is obtained by solving the rotor position signal according to the acquisition method.

[0013] The control logic switching module is used to determine the current required control mode based on the DC side voltage. Specifically, if the DC side voltage is unstable, no control is performed; if the DC side voltage is less than the preset given value and is in a stable state, an enable signal is sent to the grid-side converter control module; if the DC side voltage is stable at the given value, an enable signal is sent to the machine-side converter control module.

[0014] The coordinate transformation module is used to perform Clark and Park transformations on the grid-side three-phase phase voltage, grid-side three-phase phase current, and stator three-phase phase current to obtain the grid-side voltage, grid-side current, and stator current in a two-phase rotating coordinate system. Then, the grid-side voltage and grid-side current are sent to the grid-side converter control module, and the stator current is sent to the machine-side converter control module.

[0015] When the grid-side converter control module receives the enable signal sent by the control logic switching module, it calculates the grid-side command space voltage vector based on the grid-side voltage, grid-side current and DC-side voltage and sends it to the control signal modulation module.

[0016] When the machine-side converter control module receives the enable signal sent by the control logic switching module, it calculates the machine-side command space voltage vector based on the rotor position angle and stator current and sends it to the control signal modulation module.

[0017] The control signal modulation module is used to modulate the control signals received from the grid-side converter control module or the machine-side converter control module using a preset modulation method to obtain six pairs of complementary control pulse signals for each IGBT device in the grid-side converter or the machine-side converter.

[0018] The control pulse output module is used to receive the six control pulse signals output by the control signal modulation module, calculate the timestamp information of the rising and falling edges of each control pulse signal within a sampling period, and then transmit the six control pulse signals of the grid-side converter or the machine-side converter to the drive pulse output module through the timestamp-based digital signal output module in the RT-Lab digital real-time simulator.

[0019] The drive pulse output module is used to amplify the power of the six control pulse signals output by the control pulse output module, so that the voltage level and current intensity are sufficient to stably drive the high-frequency switch of the IGBT in the bidirectional AC-DC-AC PWM converter hardware system. Then, the amplified six control pulse signals are output to the grid-side converter or the machine-side converter to complete the control of the bidirectional AC-DC-AC PWM converter.

[0020] This invention relates to a bidirectional AC-DC-AC PWM converter control system based on RT-Lab, comprising a signal acquisition module, a drive pulse output module, and sampling signal processing module, control logic switching module, coordinate transformation module, grid-side converter control module, machine-side converter control module, control signal modulation module, and control pulse output module implemented in the RT-Lab digital real-time simulator. The control logic switching module determines whether to use the grid-side converter control module or the machine-side converter control module based on the current DC-side voltage of the bidirectional AC-DC-AC PWM converter acquired by the signal sampling module. The grid-side converter control module or the machine-side converter control module calculates the command space voltage vector using a preset control strategy, and the control signal modulation module, control pulse output module, and drive pulse output module generate drive pulses to control the grid-side converter or the machine-side converter.

[0021] This invention uses IGBTs as the core controlled element and designs control strategies for grid-side converters and machine-side converters. It performs segmented control based on DC-side voltage, simplifying the control strategy while enabling fast and effective control of the bidirectional AC-DC-AC PWM converter. Attached Figure Description

[0022] Figure 1 This is a structural diagram of a bidirectional AC-DC-AC PWM converter;

[0023] Figure 2 This is a structural diagram of a specific implementation of the bidirectional AC-DC-AC PWM converter control system based on RT-Lab of the present invention;

[0024] Figure 3 This is a schematic diagram of the inner current loop control in the grid-side converter control module of this embodiment;

[0025] Figure 4 This is a schematic diagram of the inner current loop control in the machine-side converter control module of this embodiment;

[0026] Figure 5 This is a waveform diagram of the grid-side voltage and current when the bidirectional AC-DC-AC PWM converter control system in this embodiment is operating in steady state;

[0027] Figure 6 This is a DC-side voltage waveform diagram of the bidirectional AC-DC-AC PWM converter control system in this embodiment when it is operating in steady state;

[0028] Figure 7 This is a waveform diagram of the permanent magnet synchronous motor speed when the bidirectional AC-DC-AC PWM converter control system in this embodiment is operating in steady state;

[0029] Figure 8This is a waveform diagram of the stator current of the permanent magnet synchronous motor when the bidirectional AC-DC-AC PWM converter control system is operating in steady state in this embodiment. Detailed Implementation

[0030] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0031] Example

[0032] Figure 2 This is a structural diagram of a specific implementation of the bidirectional AC-DC-AC PWM converter control system based on RT-Lab of the present invention. Figure 2 As shown, the bidirectional AC-DC-AC PWM converter control system based on RT-Lab of this invention includes a signal acquisition module 1, a sampling signal processing module 2, a control logic switching module 3, a coordinate transformation module 4, a grid-side converter control module 5, a machine-side converter control module 6, a control signal modulation module 7, a control pulse output module 8, and a drive pulse output module 9. The sampling signal processing module 2, control logic switching module 3, coordinate transformation module 4, grid-side converter control module 5, machine-side converter control module 6, control signal modulation module 7, and control pulse output module 8 are implemented in the RT-Lab digital real-time simulator. The following provides a detailed description of each module.

[0033] Signal acquisition module 1 is used to acquire signals from the bidirectional AC-DC-AC converter. The required signals include the grid-side three-phase line voltage signal and grid-side three-phase line current signal of the grid-side converter, the DC-side voltage signal and the machine-side three-phase line current signal of the machine-side converter, and the rotor position signal of the permanent magnet synchronous motor. The acquired signals are then sent to the sampling signal processing module 2.

[0034] In this embodiment, the acquisition of grid-side three-phase line voltage signals and DC-side voltage signals in signal acquisition module 1 adopts a closed-loop Hall voltage transformer, and the acquisition of grid-side three-phase line current signals and machine-side three-phase line current signals adopts a closed-loop Hall current transformer. The closed-loop Hall voltage transformer and the closed-loop Hall current transformer can perform electromagnetic isolation and step-down conversion of voltage, current and power signals. Their high linearity, low error, low temperature drift and fast response characteristics ensure high-precision sampling of voltage and current in bidirectional AC-DC-AC converter without phase difference.

[0035] The rotor position signal is acquired using an incremental ABZ-phase photoelectric encoder. The AB phase outputs of the incremental ABZ-phase photoelectric encoder are orthogonal and have a resolution of 1024 lines. After timing analysis and processing of the AB phase signals, the encoder angle pulse can be quadrupled. Before acquiring the rotor position signal, the incremental ABZ-phase photoelectric encoder needs to be calibrated. The calibration method is as follows: During the initialization of the bidirectional AC-DC-AC converter control system, a specific low-speed control pulse is first output to the permanent magnet synchronous motor (PMSM). This causes the PMSM to drive the coaxial incremental ABZ-phase encoder to rotate at low speed for several revolutions, capturing the Z-phase pulse, thus completing the calibration of the absolute angle of the incremental ABZ-phase encoder. Simultaneously, the zero point of the incremental ABZ-phase encoder is synchronized with the zero point of the PMSM rotor. Therefore, the rotor angle of the PMSM can be obtained by calculating the output signal of the incremental ABZ-phase encoder. After calibration, the rotor speed of the permanent magnet synchronous motor can be calculated by performing differential calculations on the rotor angle per unit time using the relationship between rotational speed and angle; the rotational speed of the rotor magnetic field of the permanent magnet synchronous motor can also be calculated using the relationship between rotational speed and the number of rotor pole pairs.

[0036] Furthermore, to enhance the safety of the control system, this embodiment also includes relay protection modules at the sampling points on both the grid side and the generator side of the signal acquisition module 1. In this embodiment, at the grid side and generator side sampling points, the relay protection module employs a combination of low-voltage circuit breakers, fuses, and low-voltage contactors to prevent faults such as three-phase overcurrent and three-phase short circuits at the grid connection point. At the generator side connection point, the relay protection module uses low-voltage contactors and related control logic to identify and handle faults such as overload, short circuit, and phase loss at the permanent magnet synchronous motor connection point. On the DC side, the relay protection module employs overvoltage cutoff logic to prevent damage to the signal acquisition module 1 caused by DC voltage overshoot.

[0037] The sampling signal processing module 2 is used to process the received grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, machine-side three-phase line current signal, and rotor position signal to obtain the actual values ​​of each signal, namely, grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, machine-side three-phase phase current, and rotor position angle. The stator three-phase phase current is calculated based on the machine-side three-phase phase current. Then, the DC-side voltage is sent to the control logic switching module 3 and the grid-side converter control module 5. The grid-side three-phase phase voltage, grid-side three-phase phase current, and stator three-phase phase current are sent to the coordinate transformation module 4, and the rotor position angle is sent to the machine-side converter control module 6. The specific calculation method is as follows:

[0038] For the grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, and generator-side three-phase line current signal, the analog-to-digital converter inside the RT-Lab real-time simulator is used to convert them into digital signals. Then, after amplitude and phase transformation, the actual values ​​of the grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, and generator-side three-phase phase current are obtained. Finally, the stator three-phase phase current is calculated based on the generator-side three-phase phase current.

[0039] For the rotor position signal, the actual value of the rotor position angle is obtained by calculating according to the rotor position signal acquisition method. In this embodiment, the rotor position signal is obtained through an incremental ABZ phase encoder coaxially connected to the motor. The output signal of the incremental encoder is a square wave signal (AB phase) and a single pulse signal (Z phase) that are orthogonal to each other and have a duty cycle of 0.5. When the incremental encoder shaft completes one revolution, the AB phase signal outputs 1024 pulses, and the sign of the AB phase phase difference is related to the rotation direction of the shaft. When the incremental encoder shaft rotates to a fixed position within one revolution, the Z phase outputs a single pulse signal to indicate the absolute zero point of the incremental encoder. The output signal of the incremental ABZ phase encoder is directly connected to the encoder interface of the RT-Lab digital real-time simulator, allowing the RT-Lab to acquire the pulse count of each phase signal and obtain the actual value of the encoder angle through data calculation by the sampling signal processing module 2.

[0040] The control logic switching module 3 is used to determine the required control mode based on the DC-side voltage. Specifically, if the DC-side voltage is unstable, no control is performed; if the DC-side voltage is less than a preset given value and is stable, an enable signal is sent to the grid-side converter control module; and if the DC-side voltage is stable at the given value, an enable signal is sent to the machine-side converter control module. This is because the bidirectional AC-DC-AC converter has a DC-side energy storage capacitor, which prevents the DC-side voltage from quickly rising to the given value when the bidirectional AC-DC-AC converter system is powered on. At this time, the bidirectional AC-DC-AC converter control system will wait for the DC bus voltage to rise. To achieve more precise control, this invention sets up two control modules to control different stages respectively.

[0041] The coordinate transformation module 4 performs Clark and Park transformations on the grid-side three-phase phase voltage, grid-side three-phase phase current, and stator three-phase phase current to obtain the grid-side voltage, grid-side current, and stator current in a two-phase rotating coordinate system. Then, the grid-side voltage and current are sent to the grid-side converter control module, and the stator current is sent to the machine-side converter control module. This is because the grid-side three-phase phase voltage, grid-side three-phase phase current, and machine-side three-phase phase current are all three-phase sinusoidal time variables. Directly using these AC time variables in the control law calculation would make the design and implementation of the control system very complex. It is necessary to first convert them into DC signals in a two-phase rotating coordinate system, thus facilitating the grid-side converter control module and the machine-side converter control module to solve for the system state.

[0042] When the grid-side converter control module 5 receives the enable signal sent by the control logic switching module 3, it calculates the grid-side command voltage vector based on the grid-side voltage, grid-side current and DC-side voltage and sends it to the control signal modulation module 7.

[0043] In this embodiment, the grid-side converter control module 5 includes a voltage outer loop control module and a current inner loop control module, employing a closed-loop control strategy with dual PI regulators for both voltage and current. This allows for relatively precise control of both voltage and current, wherein:

[0044] The voltage outer loop control module is used to maintain a stable DC-side voltage level. The difference between the setpoint and the actual DC-side voltage is used to obtain the grid-side current after passing through the voltage outer loop PI regulator. axis, The given value of the axis component , ,Will , As a command signal for the inner current loop;

[0045] The current inner loop control module is used to control the AC side current with speed as the primary indicator, enabling the controlled current to quickly track the command signal. The output of the command signal after passing through the current inner loop PI regulator is the command space voltage vector on the grid side. Under this strategy, the command space voltage vector is calculated as follows:

[0046] The mathematical model of the grid-side converter in the d𝑞 synchronous rotating coordinate system is as follows:

[0047] ,

[0048] in, Indicates the grid-side inductance. , These represent the grid-side currents respectively. axis, Axial components, Indicates the DC side voltage. Indicates grid-side resistance. Indicates the angular frequency of the grid-side voltage. , These represent the d-axis and q-axis components of the switching function, respectively. Indicates the DC-side load resistance. , These represent the grid-side voltages respectively. axis, Axial components, This represents the back electromotive force on the DC side; if it does not exist, then... .

[0049] By equating the DC-side voltage and related switching functions to the AC-side voltage R, we can obtain the mathematical model of the AC side of the grid-side converter:

[0050] ,

[0051] in, This represents a differential operator.

[0052] Expanding the above equation, we get:

[0053] ,

[0054] From the above equation, we can see that the d-axis and q-axis current components of the grid-side converter... , The mutual coupling will affect the design of the inner current loop PI regulator, therefore, it introduces... , Feedforward decoupled PI control. Figure 3 This is a schematic diagram of the inner current loop control in the grid-side converter control module 5 of this embodiment. (See diagram below.) Figure 3 As shown, the control law of the current inner loop control module of the grid-side converter in the dq synchronous rotating coordinate system is as follows:

[0055] ,

[0056] in, These represent the grid-side voltages respectively. axis, The given value of the axis component, This represents the proportional gain of the grid-side current loop PI regulator. This represents the integral coefficient of the grid-side current loop PI regulator. Represents the switching function. , These represent the grid-side currents respectively. axis, Axial components, Indicates the angular frequency of the grid-side voltage. Indicates the grid-side inductance. , These represent the grid-side voltages respectively. axis, Axial components.

[0057] The command space voltage vector can be calculated using the above formula. .

[0058] When the machine-side converter control module 6 receives the enable signal sent by the control logic switching module 3, it calculates the machine-side command space voltage vector based on the rotor position angle and stator current and sends it to the control signal modulation module 7.

[0059] Due to the determination of the electromagnetic torque of the three-phase permanent magnet synchronous motor It is the q-axis component of the stator current. Furthermore, there is a linear relationship between the two. Also known as torque current. Therefore, by controlling the quadrature axis current... This allows direct control of the electromagnetic torque of the three-phase permanent magnet synchronous motor. The core of electromagnetic torque control is the control of the amplitude of the stator current vector and its phase relative to the rotor flux linkage vector. Based on the above principles, in this embodiment, the machine-side converter control module 6 includes a speed outer loop control module and a current inner loop control module, employing a dual closed-loop control strategy for speed and current.

[0060] The outer loop speed control module is used to control the stability of the speed of the three-phase permanent magnet synchronous motor by adjusting the rotor position angle. The current rotor speed is obtained by differentiating with respect to time. Its relationship with the given speed value The difference is used to obtain the stator current after passing through the outer loop PI regulator. axis, The given value of the axis component , , give value , As a command signal for the inner current loop.

[0061] The inner current control module regulates the stator current of the three-phase PMSM with speed as the primary performance indicator. This allows the controlled current to quickly track the command signal output by the outer speed PI regulator, thereby controlling its electromagnetic torque. The output of the command signal after passing through the inner current PI regulator is the machine-side command space voltage vector. Under this strategy, the command space voltage vector is calculated as follows:

[0062] In the di synchronous rotating coordinate system, the stator voltage equation of a three-phase permanent magnet synchronous motor can be expressed as:

[0063] ,

[0064] in, , These represent the stator voltages respectively. axis, Axial components, , These represent the stator currents respectively. axis, Axial components, This represents the equivalent resistance of the three-phase stator windings. , These represent the equivalent inductances of the three-phase stator windings. axis, Axial components, This indicates the number of pole pairs in a permanent magnet synchronous motor. This represents the maximum flux linkage generated when the magnetic field of the permanent magnet links with the stator windings during rotor rotation.

[0065] From the above formula, we can see that the stator current of a three-phase permanent magnet synchronous motor is... , Cross-coupled electromotive forces were generated in the d-axis and d-axis directions, respectively, therefore, a cross-coupled electromotive force was introduced. , Feedforward decoupled PI control. Figure 4 This is a schematic diagram of the inner current loop control in the machine-side converter control module 6 of this embodiment. (See diagram below.) Figure 4 As shown, the control law of the inner loop PI controller for the three-phase permanent magnet synchronous motor in the d𝑞 synchronous rotating coordinate system is as follows:

[0066] ,

[0067] in, These represent the stator voltages respectively. axis, The given value of the axis component, This represents the proportional coefficient of the PI regulator in the machine-side current loop. This represents the integral coefficient of the machine-side current loop PI regulator. Represents the switching function. , These represent the stator currents respectively. axis, Axial components, , These represent the equivalent inductances of the three-phase stator windings. axis, Axial components, This indicates the number of pole pairs in a permanent magnet synchronous motor. This represents the maximum flux linkage generated when the magnetic field of the permanent magnet links with the stator windings during rotor rotation.

[0068] This yields the command voltage vector of the machine-side converter. .

[0069] The control signal modulation module 7 is used to modulate the control signals received from the grid-side converter control module 5 or the machine-side converter control module 6 using a preset modulation method to obtain six complementary control pulse signals for each IGBT device in the grid-side converter or the machine-side converter.

[0070] The control pulse output module 8 is used to receive the six control pulse signals output by the control signal modulation module 7, calculate the timestamp information of the rising and falling edges of each control pulse signal within a sampling period, and then transmit the six control pulse signals of the grid-side converter or the machine-side converter to the drive pulse output module 9 through the timestamp-based digital signal output module in the RT-Lab digital real-time simulator.

[0071] The drive pulse output module 9 amplifies the six control pulse signals output by the control pulse output module 8, ensuring their voltage and current levels are sufficient to stably drive the high-frequency switches of the IGBTs in the bidirectional AC-DC-AC PWM converter hardware system. The amplified six control pulse signals are then output to the grid-side converter or the generator-side converter, completing the control of the bidirectional AC-DC-AC PWM converter. In this embodiment, the drive pulse output subsystem also features input and output opto-isolation, preventing high voltage and high current coupling from the power conversion subsystem to the control side and avoiding damage to the controller interface.

[0072] The working process of the bidirectional AC-DC-AC PWM converter control system of the present invention is as follows:

[0073] (1) First, the system is initialized and the power section is powered on. At this time, the grid-side converter control module and the machine-side converter control module are not working, but the DC-side stabilizing capacitor of the power section is continuously charging. After the control system is initialized, the grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, machine-side three-phase line current signal and the rotor position signal of the bidirectional AC-DC-AC PWM converter are continuously sampled and processed to obtain the grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, machine-side three-phase phase current and rotor position angle.

[0074] (2) When the control system detects that the DC side voltage is lower than the given value and is in a stable state, it indicates that the DC side voltage regulator capacitor is basically charged and the grid-side converter control module 5 enters the working state. When the grid-side converter is in the working state, it will perform coordinate transformation on the grid-side voltage signal, grid-side current signal and DC side voltage signal collected by the hardware system and use them as the feedback of the control algorithm. At the same time, according to the dual closed-loop control strategy, the grid-side converter control signal is generated. After passing through the control signal modulation module 7 and the control pulse output module 8, the switching control of the six IGBT devices in the grid-side converter is completed.

[0075] (3) After the grid-side converter enters the working state, the control system will continuously detect whether the DC side voltage is stable at the given value. When the DC side voltage is stable at the given value, the machine-side converter control module 6 will enter the working state. When the machine-side converter is in the working state, the coordinate transformation of the DC side voltage signal, machine side current signal and rotor angle signal of the permanent magnet synchronous motor collected by the hardware system will be used as the feedback of the control algorithm. At the same time, the machine-side converter control signal will be generated according to the dual closed-loop control strategy. After passing through the control signal modulation module 7 and the control pulse output module 8, the switching control of the six IGBT devices in the machine-side converter will be completed.

[0076] To better illustrate the technical effects of the present invention, specific examples are used to conduct experimental verification of the present invention.

[0077] Figure 5 This is a waveform diagram of the grid-side voltage and current when the bidirectional AC-DC-AC PWM converter control system in this embodiment is operating in steady state. Figure 5 As shown, the grid-side converter can operate at a unity power factor of 0.987 in steady state, while the grid-side current THD is 4.36%.

[0078] Figure 6 This is the DC-side voltage waveform diagram of the bidirectional AC-DC-AC PWM converter control system in this embodiment when it is operating in steady state. Figure 6 As shown, in steady state, the grid-side converter control module 5 can stabilize the DC-side voltage near a given value, at which point the voltage fluctuation range is 2.79V.

[0079] Figure 7 This is a waveform diagram of the permanent magnet synchronous motor speed when the bidirectional AC-DC-AC PWM converter control system in this embodiment is operating in steady state. Figure 7 As shown, in steady state, the side converter control module 6 can control the speed of the permanent magnet synchronous motor to be near a given value, at which time the fluctuation range of the motor speed is 0.31 r / min.

[0080] Figure 8This is a waveform diagram of the stator-side current of the permanent magnet synchronous motor when the bidirectional AC-DC-AC PWM converter control system in this embodiment is operating in steady state. Figure 8 As shown, in steady state, the time-side converter can control the stator current to be a relatively stable sine wave while stabilizing the speed of the permanent magnet synchronous motor, and its THD is 6.04%.

[0081] In summary, the bidirectional AC-DC-AC PWM converter control system of the present invention can work effectively and stably, and can quickly and effectively control the bidirectional AC-DC-AC PWM converter.

[0082] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A bidirectional AC-DC-AC converter control system based on RT-Lab, characterized in that... It includes a signal acquisition module, a sampling signal processing module, a control logic switching module, a coordinate transformation module, a grid-side converter control module, a machine-side converter control module, a control signal modulation module, a control pulse output module, and a drive pulse output module. Among them, the sampling signal processing module, the control logic switching module, the coordinate transformation module, the grid-side converter control module, the machine-side converter control module, the control signal modulation module, and the control pulse output module are implemented in the RT-lab digital real-time simulator. The signal acquisition module is used to acquire signals from the bidirectional AC-DC-AC converter. The required signals include the grid-side three-phase line voltage signal and grid-side three-phase line current signal of the grid-side converter, the DC-side voltage signal and machine-side three-phase line current signal of the machine-side converter, and the rotor position signal of the permanent magnet synchronous motor. The acquired signals are then sent to the sampling signal processing module. The sampling signal processing module is used to process the received grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, machine-side three-phase line current signal, and rotor position signal to obtain the actual values ​​of each signal, namely, grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, machine-side three-phase phase current, and rotor position angle. The stator three-phase phase current is calculated based on the machine-side three-phase phase current. Then, the DC-side voltage is sent to the control logic switching module and the grid-side converter control module. The grid-side three-phase phase voltage, grid-side three-phase phase current, and stator three-phase phase current are sent to the coordinate transformation module, and the rotor position angle is sent to the machine-side converter control module. The specific processing method is as follows: For the grid-side three-phase line voltage signal, grid-side three-phase line current signal, DC-side voltage signal, and machine-side three-phase line current signal, the analog-to-digital converter inside the RT-Lab real-time simulator is used to convert them into digital signals. Then, after amplitude transformation and phase transformation, the actual values ​​of the grid-side three-phase phase voltage, grid-side three-phase phase current, DC-side voltage, and machine-side three-phase phase current are obtained. The stator three-phase phase current is calculated based on the machine-side three-phase phase current. For the rotor position signal, the actual value of the rotor position angle is obtained by solving the rotor position signal according to the acquisition method. The control logic switching module is used to determine the current required control mode based on the DC side voltage. Specifically, if the DC side voltage is unstable, no control is performed; if the DC side voltage is less than the preset given value and is in a stable state, an enable signal is sent to the grid-side converter control module; if the DC side voltage is stable at the given value, an enable signal is sent to the machine-side converter control module. The coordinate transformation module is used to perform Clark and Park transformations on the grid-side three-phase phase voltage, grid-side three-phase phase current, and stator three-phase phase current to obtain the grid-side voltage, grid-side current, and stator current in a two-phase rotating coordinate system. Then, the grid-side voltage and grid-side current are sent to the grid-side converter control module, and the stator current is sent to the machine-side converter control module. When the grid-side converter control module receives the enable signal sent by the control logic switching module, it calculates the grid-side command space voltage vector based on the grid-side voltage, grid-side current and DC-side voltage and sends it to the control signal modulation module. When the machine-side converter control module receives the enable signal sent by the control logic switching module, it calculates the machine-side command space voltage vector based on the rotor position angle and stator current and sends it to the control signal modulation module. The control signal modulation module is used to modulate the control signals received from the grid-side converter control module or the machine-side converter control module using a preset modulation method to obtain six pairs of complementary control pulse signals for each IGBT device in the grid-side converter or the machine-side converter. The control pulse output module is used to receive the six control pulse signals output by the control signal modulation module, calculate the timestamp information of the rising and falling edges of each control pulse signal within a sampling period, and then transmit the six control pulse signals of the grid-side converter or the machine-side converter to the drive pulse output module through the timestamp-based digital signal output module in the RT-Lab digital real-time simulator. The drive pulse output module is used to amplify the power of the six control pulse signals output by the control pulse output module, so that the voltage level and current intensity are sufficient to stably drive the high-frequency switch of the IGBT in the bidirectional AC-DC-AC PWM converter hardware system. Then, the amplified six control pulse signals are output to the grid-side converter or the machine-side converter to complete the control of the bidirectional AC-DC-AC PWM converter.

2. The bidirectional AC-DC-AC PWM converter control system according to claim 1, characterized in that, The acquisition of the grid-side three-phase line voltage signal and the DC-side voltage signal is performed using a closed-loop Hall voltage transformer, while the acquisition of the grid-side three-phase line current signal and the machine-side three-phase line current signal is performed using a closed-loop Hall current transformer.

3. The bidirectional AC-DC-AC PWM converter control system according to claim 1, characterized in that, The rotor position signal is acquired using an incremental ABZ phase photoelectric encoder.

4. The bidirectional AC-DC-AC PWM converter control system according to claim 1, characterized in that, Relay protection modules were installed at the sampling points on both the grid side and the machine side of the signal sampling module.

5. The bidirectional AC-DC-AC PWM converter control system according to claim 1, characterized in that, The grid-side converter control module includes a voltage outer loop control module and a current inner loop control module, wherein: The voltage outer loop control module is used to maintain a stable DC-side voltage level. The difference between the setpoint and the actual DC-side voltage is used to obtain the grid-side current after passing through the voltage outer loop PI regulator. axis, The given value of the axis component , ,Will , As a command signal for the inner current loop; The current inner loop control module is used to control the AC side current with speed as the primary indicator, enabling the controlled current to quickly track the command signal. The output of the command signal after passing through the current inner loop PI regulator is the command space voltage vector on the grid side. Command space voltage vector The calculation formula is: ， in, These represent the grid-side voltages respectively. axis, The given value of the axis component, This represents the proportional gain of the grid-side current loop PI regulator. This represents the integral coefficient of the grid-side current loop PI regulator. Represents the switching function. , These represent the grid-side currents respectively. axis, Axial components, Indicates the angular frequency of the grid-side voltage. Indicates the grid-side inductance. , These represent the grid-side voltages respectively. axis, Axial components.

6. The bidirectional AC-DC-AC PWM converter control system according to claim 1, characterized in that, The machine-side converter control module includes a speed outer loop control module and a current inner loop control module, wherein: The outer loop speed control module is used to control the stability of the speed of the three-phase permanent magnet synchronous motor by adjusting the rotor position angle. The current rotor speed is obtained by differentiating with respect to time. Its relationship with the given speed value The difference is used to obtain the stator current after passing through the outer loop PI regulator. axis, The given value of the axis component , , give value , As a command signal for the inner current loop; The inner current control module regulates the stator current of the three-phase PMSM with speed as the primary performance indicator. This allows the controlled current to quickly track the command signal output by the outer speed PI regulator, thereby controlling its electromagnetic torque. The output of the command signal after passing through the inner current PI regulator is the machine-side command space voltage vector. Command space voltage vector The calculation formula is: ， in, These represent the stator voltages respectively. axis, The given value of the axis component, This represents the proportional coefficient of the PI regulator in the machine-side current loop. This represents the integral coefficient of the machine-side current loop PI regulator. Represents the switching function. , These represent the stator currents respectively. axis, Axial components, , These represent the equivalent inductances of the three-phase stator windings. axis, Axial components, This indicates the number of pole pairs in a permanent magnet synchronous motor. This represents the maximum flux linkage generated when the magnetic field of the permanent magnet links with the stator windings during rotor rotation.

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