CN116800105A - Bidirectional AC-DC-AC PWM converter control system based on RT-Lab - Google Patents
Bidirectional AC-DC-AC PWM converter control system based on RT-Lab Download PDFInfo
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Abstract
本发明公开了一种基于RT‑Lab的双向交‑直‑交PWM变流器控制系统，包括信号采集模块、驱动脉冲输出模块和在RT‑lab数字实时仿真机中实现的采样信号处理模块、控制逻辑切换模块、坐标变换模块、网侧变流器控制模块、机侧变流器控制模块、控制信号调制模块、控制脉冲输出模块，其中控制逻辑切换模块根据信号采样模块采集的直流侧电压进行判断，选用网侧变流器控制模块或机侧变流器控制模块进行控制，侧变流器控制模块或机侧变流器控制模块采用预设的控制策略计算指令空间电压矢量，并由控制信号调制模块、控制脉冲输出模块、驱动脉冲输出模块生成驱动脉冲，对网侧变流器或机侧变流器进行控制。本发明可以对双向交‑直‑交PWM变流器进行快速、有效的控制。
The invention discloses a bidirectional AC-AC-AC PWM converter control system based on RT-Lab, which includes a signal acquisition module, a driving pulse output module and a sampling signal processing module implemented in the RT-lab digital real-time simulation machine. 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. The control logic switching module performs operation based on the DC side voltage collected by the signal sampling module. Judgment, select the grid-side converter control module or the machine-side converter control module for control. The side converter control module or the machine-side converter control module uses the preset control strategy to calculate the command space voltage vector, and the control module The signal modulation module, control pulse output module, and driving pulse output module generate driving pulses to control the grid-side converter or the machine-side converter. The invention can quickly and effectively control the bidirectional AC-DC-AC PWM converter.
Description
Technical Field
The invention belongs to the technical field of converter control, and particularly relates to a bidirectional AC-DC-AC PWM converter control system based on an RT-Lab.
Background
The bidirectional ac-dc-ac converter is a core component in a modern power system, and has the main function of converting electric energy forms, and the main types of the bidirectional ac-dc-ac converter are two types of thyristor-based phase control converters and IGBT (Insulated Gate Bipolar Transistor ) -based PWM converters. Although the phase-controlled converter can bear high voltage and large current, the thyristor has a half-control characteristic that the thyristor can only be controlled to be turned on but not be controlled to be turned off actively, and meanwhile, the thyristor works in a low-speed switching state to cause the harmonic content of an output waveform to be very high, so that the phase-controlled converter is not suitable for high-frequency and high-precision power conversion application. Although the PWM converter has a lower power density than the phase-control converter, it can operate in a high-frequency switching state due to the adoption of a fully-controlled power semiconductor device. In an inertial system and under a proper control algorithm, extremely high control precision can be achieved. The PWM converter can output direct-current voltage with extremely low harmonic content and peak-to-peak value, can easily realize the sine of alternating-current side voltage and current, and has the capability of flexibly controlling the power factor of the alternating-current side, so that the alternating-current side of the PWM converter presents the characteristic of a controlled current source. Therefore, the PWM converter is widely applied to occasions with higher requirements on electric energy output quality, such as the fields of wind power generation, solar photovoltaic power generation, electric automobiles, uninterruptible power supplies, motor control and the like.
Fig. 1 is a block diagram of a bi-directional ac-dc-ac PWM converter. As shown in fig. 1, the bidirectional ac-dc-ac PWM converter comprises a grid-side converter and a machine-side converter, wherein the grid-side converter is used for inverting the dc bus voltage level into ac voltage which has stable amplitude and frequency and meets the grid-connected requirement; reasonably controlling energy exchange between the direct current bus and the power grid according to the requirement of the power grid, thereby improving the power factor of the access point of the power grid; and under the condition of ensuring the normal operation of the wind generating set, a certain capacity of reactive power support is provided for the power grid, so that the stability of the power grid access point is ensured. The main function of the machine side converter is to improve the operation efficiency and reliability of the generator through a proper control strategy.
The Control strategy of the network-side converter can be mainly divided into two major categories, namely Vector Control (VC) and direct power Control (Direct Power Control, DPC). The vector control strategy can be subdivided into a vector control based on grid Voltage orientation (Voltage OrientedControl, VOC) and a vector control based on virtual flux linkage orientation (Virtual Flux Oriented Control, VFOC), but both control strategies are relatively complex to implement. The DPC control strategy has the defects of larger active power and reactive power pulsation, unfixed switching frequency of the converter, higher current THD and the like.
For the control strategy of the machine side converter, two types of magnetic field directional control (filled OrientedControl, FOC) and direct torque control (Direct Torque Control, DTC) are most commonly used at present, but the system structure of the FOC control strategy is complex, and the DTC control strategy can cause the switching period of the PWM converter to be not fixed, so that flux linkage and torque fluctuation are large, and the control of the torque and flux linkage cannot be simultaneously achieved.
In addition, the research on the control algorithm of the bidirectional AC-DC-AC PWM converter is usually based on a digital simulation platform, and because the digital simulation ignores many details of a real physical system, the digital simulation can only carry out principle verification on the control algorithm and can not accurately restore the real physical control system, so the digital simulation control algorithm has very important significance on the comprehensive research on the hardware system of the bidirectional AC-DC-AC converter based on a rapid control prototype and related control algorithm, but the research in the field is less at present, and the industrial application can not be realized.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a bidirectional AC-DC-AC PWM converter control system based on an RT-Lab, which takes IGBT as a core controlled element, designs network-side converter control and machine-side converter control and rapidly and effectively controls the bidirectional AC-DC-AC PWM converter.
In order to achieve the aim of the invention, the control system of the bidirectional AC-DC-AC PWM converter based on the RT-Lab comprises a signal acquisition module, a sampling signal processing module, a control logic switching module, a coordinate conversion module, a network side converter control module, a machine side converter control module, a control signal modulation module, a control pulse output module and a driving pulse output module, wherein the sampling signal processing module, the control logic switching module, the coordinate conversion module, the network side converter control module, the machine side converter control module, the control signal modulation module and the control pulse output module are realized in an RT-Lab digital real-time simulator;
the signal acquisition module is used for acquiring signals of the bidirectional AC-DC-AC converter, wherein the required signals comprise a network side three-phase line voltage signal and a network side three-phase line current signal of the network side converter, a direct current side voltage signal and a machine side three-phase line current signal of the machine side converter and a rotor position signal of the permanent magnet synchronous motor, and all the acquired signals are sent to the sampling signal processing module;
the sampling signal processing module is used for resolving the received network side three-phase line voltage signal, network side three-phase line current signal, direct current side voltage signal, machine side three-phase line current signal and rotor position signal to obtain actual values of the signals, namely network side three-phase voltage, network side three-phase current, direct current side voltage, machine side three-phase current and rotor position angle, stator three-phase current is obtained according to conversion of the machine side three-phase current, then the direct current side voltage is sent to the control logic switching module and the network side converter control module, the network side three-phase voltage, the network side three-phase current and the stator three-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 method for the solution is as follows:
for the three-phase line voltage signal of the net side, the three-phase line current signal of the net side, the voltage signal of the direct current side and the three-phase line current signal of the machine side, an analog-digital converter in the real-time simulation machine of the RT-Lab is adopted to replace the digital signal, and then the actual values of the three-phase line voltage of the net side, the three-phase line current of the net side, the voltage of the direct current side and the three-phase line current of the machine side are obtained after amplitude conversion and phase conversion; according to the conversion of the side three-phase current, the stator three-phase current is obtained;
for the rotor position signal, resolving according to a rotor position signal acquisition method to obtain an actual value of a rotor position angle;
the control logic switching module is used for judging a currently required control mode according to the voltage of the direct current side, and the specific method comprises the following steps: if the direct-current side voltage is unstable, the control is not performed, if the direct-current side voltage is smaller than a preset given value and is in a stable state, an enabling signal is sent to the network side converter control module, and if the machine side three-phase voltage is stable at the given value, an enabling signal is sent to the machine side converter control module;
the coordinate transformation module is used for performing Clark transformation and Park transformation on the network side three-phase voltage, the network side three-phase current and the stator three-phase current to obtain network side voltage, network side current and stator current under a two-phase rotating coordinate system, then sending the network side voltage and the network side current to the network side converter control module, and sending the stator current to the machine side converter control module;
when receiving the enabling signal sent by the control logic switching module, the network side converter control module calculates a command space voltage vector of the network side according to the network side voltage, the network side current and the direct current side voltage and sends the command space voltage vector to the control signal modulation module;
when receiving the enabling signal sent by the control logic switching module, the machine side converter control module calculates a machine side command space voltage vector according to the rotor position angle and the stator current and sends the command space voltage vector to the control signal modulation module;
the control signal modulation module is used for modulating control signals received from the grid-side converter control module or the machine-side converter control module by adopting a preset modulation mode to obtain six paths of two-to-two complementary control pulse signals of each IGBT device in the grid-side converter or the machine-side converter;
the control pulse output module is used for receiving the six paths of control pulse signals output by the control signal modulation module, calculating the time stamp information of the rising edge and the falling edge of each path of control pulse signal in one sampling period, and then transmitting the six paths of control pulse signals of the grid-side converter or the machine-side converter to the driving pulse output module through the digital signal output module based on the time stamp in the RT-Lab digital real-time simulator;
the driving pulse output module is used for amplifying the power of the six paths of control pulse signals output by the control pulse output module, so that the voltage level and the current intensity of the six paths of control pulse signals are enough to stably drive the high-frequency switch of the IGBT in the hardware system of the bidirectional AC-DC-AC PWM converter, and then the amplified six paths of control pulse signals are output to the grid-side converter or the machine-side converter, so that the control of the bidirectional AC-DC-AC PWM converter is completed.
The invention discloses a control system of a bidirectional AC-DC-AC PWM converter based on an RT-Lab, which comprises a signal acquisition module, a driving pulse output module, a sampling signal processing module, a control logic switching module, a coordinate conversion module, a network side converter control module, a machine side converter control module, a control signal modulation module and a control pulse output module which are realized in an RT-Lab digital real-time simulator, wherein the control logic switching module judges according to the current DC side voltage of the bidirectional AC-DC-AC PWM converter acquired by the signal acquisition module, selects the network side converter control module or the machine side converter control module for control, calculates an instruction space voltage vector by adopting a preset control strategy, and generates driving pulses by the control signal modulation module, the control pulse output module and the driving pulse output module to control the network side converter or the machine side converter.
The invention takes IGBT as a core controlled element, designs a network side converter control strategy and a machine side converter control strategy, performs sectional control based on direct current side voltage, and rapidly and effectively controls the bidirectional AC-DC-AC PWM converter while simplifying the control strategy.
Drawings
Fig. 1 is a block diagram of a bi-directional ac-dc-ac PWM converter;
FIG. 2 is a block diagram of a specific embodiment of a RT-Lab based bi-directional AC-DC-AC PWM converter control system of the present invention;
fig. 3 is a schematic diagram of current inner loop control in the control module of the grid-side converter according to the embodiment;
fig. 4 is a schematic diagram of current inner loop control in the control module of the machine side converter of the present embodiment;
fig. 5 is a diagram showing waveforms of voltage and current on the network side when the bi-directional ac-dc-ac PWM converter control system of the present embodiment is operating in steady state;
fig. 6 is a waveform diagram of the dc side voltage of the bi-directional ac-dc-ac PWM converter control system according to the present embodiment when operating in a steady state;
fig. 7 is a waveform diagram of the rotational speed of the permanent magnet synchronous motor when the bi-directional ac-dc-ac PWM converter control system of the present embodiment is operating in a steady state;
fig. 8 is a waveform diagram of the stator side current of the permanent magnet synchronous motor when the bi-directional ac-dc-ac PWM converter control system of the present embodiment is operating in steady state.
Detailed Description
The following description of the embodiments of the invention is presented in conjunction with the accompanying drawings to provide a better understanding of the invention to those skilled in the art. It is to be expressly noted that in the description below, detailed descriptions of known functions and designs are omitted here as perhaps obscuring the present invention.
Examples
Fig. 2 is a block diagram of an embodiment of the control system of the bi-directional ac-dc-ac PWM converter based on RT-Lab of the present invention. As shown in fig. 2, the bidirectional ac-dc-ac PWM converter control system based on RT-Lab of the present 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 network 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 driving pulse output module 9, wherein the sampling signal processing module 2, the control logic switching module 3, the coordinate transformation module 4, the network side converter control module 5, the machine side converter control module 6, the control signal modulation module 7, and the control pulse output module 8 are implemented in an RT-Lab digital real-time simulator. The respective modules are described in detail below.
The signal acquisition module 1 is used for acquiring signals of the bidirectional AC-DC-AC converter, wherein the required signals comprise a network side three-phase line voltage signal and a network side three-phase line current signal of the network side converter, a direct current side voltage signal and a machine side three-phase line current signal of the machine side converter and a rotor position signal of the permanent magnet synchronous motor, and all the acquired signals are sent to the sampling signal processing module 2.
In the embodiment, the collection of the network side three-phase line voltage signal and the direct current side voltage signal in the signal collection module 1 adopts a closed-loop Hall voltage transformer, the collection of the network side three-phase line current signal and the machine side three-phase line current signal adopts a closed-loop Hall current transformer, the closed-loop Hall voltage transformer and the closed-loop Hall current transformer can carry out electromagnetic isolation and buck conversion on the voltage, current and power signals, and the characteristics of high linearity, low error, low temperature drift, quick response and the like ensure the non-phase difference high-precision sampling of the voltage and the current in the bidirectional alternating current-direct current-alternating current transformer.
The acquisition of the rotor position signal adopts an incremental ABZ phase photoelectric encoder, the AB phase output of the incremental ABZ phase photoelectric encoder is orthogonal and has 1024-line resolution, and four times of frequency of encoder angle pulse can be realized after time sequence analysis and processing are carried out on the AB phase signal. The incremental ABZ phase photoelectric encoder needs to be corrected before rotor position signal acquisition, and the correction method comprises the following steps: when the bidirectional AC-DC-AC current transformer control system is initialized, a specific low-speed control pulse is output to the permanent magnet synchronous motor, so that the permanent magnet synchronous motor drives the coaxial incremental ABZ phase encoder to rotate for a plurality of weeks at a low speed, and Z phase pulses are captured, thereby completing the correction of the absolute angle of the incremental ABZ phase encoder. Meanwhile, the synchronization of the zero point of the incremental ABZ phase encoder and the zero point of the rotor of the permanent magnet synchronous motor is completed, so that the rotor angle of the permanent magnet synchronous motor can be obtained through the calculation of the output signal of the incremental ABZ phase encoder. After correction is completed, the rotor angle in unit time is subjected to differential operation by utilizing the relation between the rotating speed and the angle, and the rotating speed of the rotor of the permanent magnet synchronous motor can be calculated; the relation between the rotating speed and the pole pair number of the rotor can be used for calculating the rotating speed of the rotor magnetic field of the permanent magnet synchronous motor.
In addition, in order to improve the safety of the control system, relay protection modules are further respectively arranged at sampling points of the signal acquisition module 1 at the network side and the machine side in the embodiment. In the embodiment, at the sampling points of the network side and the machine side, the relay protection module adopts the combined protection logic of the low-voltage circuit breaker, the fuse and the low-voltage contactor to prevent the faults of three-phase overcurrent, three-phase short circuit and the like of the access point of the power grid; at the side access point, the relay protection module adopts a low-voltage contactor and related control logic to realize the identification and treatment of overload, short circuit, phase failure and other faults at the permanent magnet synchronous motor access point; on the direct current side, the relay protection module adopts overvoltage cut-off logic to prevent overvoltage faults caused by direct current voltage overshoot from damaging the signal acquisition module 1.
The sampling signal processing module 2 is configured to calculate the received network side three-phase line voltage signal, network side three-phase line current signal, direct current side voltage signal, machine side three-phase line current signal, and rotor position signal, to obtain actual values of the respective signals, that is, network side three-phase voltage, network side three-phase current, direct current side voltage, machine side three-phase current, and rotor position angle, convert the machine side three-phase current to obtain stator three-phase current, and then send the direct current side voltage to the control logic switching module 3 and the network side converter control module 5, send the network side three-phase voltage, network side three-phase current, and stator three-phase current to the coordinate transformation module 4, and send the rotor position angle to the machine side converter control module 6. The specific method for the solution is as follows:
for the three-phase line voltage signal on the net side, the three-phase line current signal on the net side, the voltage signal on the direct current side and the three-phase line current signal on the machine side, an analog-digital converter in the real-time RT-Lab simulator is adopted to replace the digital signal, and then the actual values of the three-phase line voltage on the net side, the three-phase line current on the net side, the voltage on the direct current side and the three-phase line current on the machine side are obtained after amplitude conversion and phase conversion. And then the stator three-phase current is obtained according to the conversion of the machine side three-phase current.
And (3) for the rotor position signal, calculating according to a rotor position signal acquisition method to obtain an actual value of the rotor position angle. Because the rotor position signal is obtained by the incremental ABZ phase encoder coaxially connected with the motor, the output signals of the incremental encoder are mutually orthogonal square wave signals (AB phase) and monopulse signals (Z phase) with the duty ratio of 0.5; when the rotary shaft of the incremental encoder rotates for a complete circle, the AB phase signal outputs 1024 pulses, and the positive and negative of the AB phase difference are related to the rotation direction of the rotary shaft; when the rotary shaft of the incremental encoder rotates to a certain fixed position in a circle, the Z phase outputs a pulse signal once to represent 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, so that the RT-Lab digital real-time simulator can acquire the pulse number of each phase signal, and the actual value of the encoder angle is obtained through the data calculation of the sampling signal processing module 2.
The control logic switching module 3 is configured to determine a currently required control mode according to the dc side voltage, and specifically includes: if the direct-current side voltage is unstable, the control is not performed, if the direct-current side voltage is smaller than a preset given value and is in a stable state, an enabling signal is sent to the network-side converter control module, and if the machine-side three-phase voltage is stable at the given value, an enabling signal is sent to the machine-side converter control module. The control system of the bidirectional AC-DC-AC converter waits for the rising of the DC bus voltage, and in order to realize more accurate control, the invention is provided with two control modules which respectively control different stages.
The coordinate transformation module 4 is configured to perform Clark transformation and Park transformation on the network side three-phase voltage, the network side three-phase current and the stator three-phase current to obtain a network side voltage, a network side current and a stator current under a two-phase rotating coordinate system, and then send the network side voltage and the network side current to the network side converter control module and send the stator current to the machine side converter control module. The network side three-phase voltage, the network side three-phase current and the machine side three-phase current are three-phase sine time variables, and the direct use of the alternating current time variables to participate in the calculation of the control law can complicate the design and the realization of a control system, and the direct current signals need to be converted into direct current signals under a two-phase rotating coordinate system, so that the network side converter control module and the machine side converter control module can solve the system state conveniently.
When receiving the enabling signal sent by the control logic switching module 3, the network side converter control module 5 calculates a command voltage vector of the network side according to the network side voltage, the network side current and the direct current side voltage and sends the command voltage vector to the control signal modulation module 7.
In this embodiment, the grid-side converter control module 5 includes a voltage outer loop control module and a current inner loop control module, and adopts a voltage-current dual PI regulator closed loop control strategy, so that voltage and current can be controlled accurately respectively, where:
the voltage outer ring control module is used for keeping the voltage level of the direct current side stable, and obtaining the given value of the d-axis and q-axis components of the network side current after the difference between the given value and the actual value of the direct current side voltage passes through the voltage outer ring PI regulatorWill beAs a command signal for the inner loop of the current;
the current inner loop control module is used for controlling the current of the alternating current side by taking the rapidity as a main index, so that the controlled current can rapidly track the command signal, and the output of the command signal after passing through the current inner loop PI regulator is the command space voltage vector of the network sideThe calculation method of the command space voltage vector under the strategy comprises the following steps:
the mathematical model of the grid-side converter under the dq synchronous rotation coordinate system is recorded as follows:
wherein L represents a network side inductance, i g,d 、i g,q Respectively represent d-axis and q-axis components of the current on the net side, u dc Represents the DC side voltage, R represents the network side resistance, ω represents the network side voltage angular frequency, s d 、s q Respectively representing d-axis component and q-axis component of the switching function, R L Represents the direct current side load resistance, e d 、e q Respectively represent d-axis and q-axis components, e of the network side voltage L Represents the back electromotive force on the DC side, and if not present, e L ＝0。
The direct-current side voltage and the related switching function are equivalent to alternating-current side voltage V, and an alternating-current side mathematical model of the grid-side converter can be obtained:
where p represents the differential operator.
The method comprises the following steps of expanding the above method to obtain:
from the above, the d, q-axis current component i of the grid-side converter g,d 、i g,q Mutual coupling, which will affect the design of the current-loop PI-regulator, thus introducing i g,q ,i g,q Is coupled to the PI control. Fig. 3 is a schematic diagram of current inner loop control in the grid-side converter control module 5 according to the present embodiment. As shown in fig. 3, the control law of the current inner loop control module of the grid-side converter under the dq synchronous rotation coordinate system is as follows:
wherein ,respectively representing the given values of d-axis and q-axis components of the network side voltage, K iP Representing the scaling factor, K, of a network-side current loop PI regulator iI The integral coefficient of the current loop PI regulator at the network side is represented, s represents the switching function, i g,d 、i g,q Respectively representing d-axis and q-axis components of the network side current, ω represents the network side voltage angular frequency, L represents the network side inductance, e d 、e q The d-axis and q-axis components of the grid-side voltage are shown, respectively.
The instruction space voltage vector can be calculated according to the above method
When receiving the enable signal sent by the control logic switching module 3, the machine side converter control module 6 calculates a machine side command space voltage vector according to the rotor position angle and the stator current and sends the command space voltage vector to the control signal modulation module 7.
Due to the determination of the electromagnetic torque T of the three-phase permanent magnet synchronous motor e Is the q-axis component i of the stator current s,q And there is a linear relationship between the two，i s,q Also known as torque current. Thus by controlling the quadrature current i s,q The electromagnetic torque of the three-phase permanent magnet synchronous motor can be directly controlled, and the core of the electromagnetic torque control is the control of the amplitude of the stator current vector and the phase of the stator current vector relative to the rotor flux linkage vector. Based on the above principle, in this embodiment, the network-side converter control module 6 includes a rotation speed outer ring control module and a current inner ring control module, and adopts a rotation speed and current dual closed-loop control strategy, where:
the rotating speed outer ring control module is used for controlling the stability of the rotating speed of the three-phase permanent magnet synchronous motor by controlling the rotor position angle theta r Deriving time to obtain current rotational speed omega of rotor r Which is related to the rotation speed set valueAfter passing through the speed outer ring PI regulator, the given value of the d-axis and q-axis components of the stator current is obtained>Will give->As a command signal for the inner loop of the current.
The current inner loop control module is used for adjusting the stator current of the three-phase PMSM by taking the rapidity as a main index, so that the controlled current can rapidly track the command signal output by the voltage outer loop PI regulator, thereby achieving the control of the electromagnetic torque of the current inner loop PI regulator, and the output of the command signal after passing through the current inner loop PI regulator is the command space voltage vector of the machine sideThe calculation method of the command space voltage vector under the strategy comprises the following steps:
in the dq synchronous rotation coordinate system, the stator voltage equation of the three-phase permanent magnet synchronous motor can be expressed as:
wherein ,us,d 、u s,q Respectively representing d-axis and q-axis components, i of stator voltage s,d 、i s,q Respectively representing d-axis and q-axis components of stator current, R' represents equivalent resistance of three-phase stator winding, L d 、L q Respectively represent d-axis and q-axis components and n of three-phase stator winding equivalent inductance p Representing the pole pair number, ψ, of a permanent magnet synchronous motor f The maximum value of flux linkage generated when the permanent magnet magnetic field and the stator winding are linked when the rotor rotates.
From the above, the stator current i of the three-phase permanent magnet synchronous motor s,d 、i s,q Cross-coupled electromotive forces are generated in q-axis and d-axis directions, respectively, thus introducing i s,d 、i s,q Is coupled to the PI control. Fig. 4 is a schematic diagram of the current inner loop control in the current transformer control module 6 on the machine side of the present embodiment. As shown in fig. 4, the control law of the current inner loop PI controller of the three-phase permanent magnet synchronous motor under the dq synchronous rotation coordinate system is expressed as follows:
wherein ,respectively representing given values of d-axis and q-axis components of stator voltage, K i ′ P Representing the scaling factor, K, of the machine side current loop PI regulator i ′ I Representing the integral coefficient of the side current loop PI regulator, s representing the switching function, i s,d 、i s,q Respectively represent d-axis and q-axis components of stator current, L d 、L q Respectively represent d-axis and q-axis components and n of three-phase stator winding equivalent inductance p Representing the pole pair number, ψ, of a permanent magnet synchronous motor f The maximum value of flux linkage generated when the permanent magnet magnetic field and the stator winding are linked when the rotor rotates.
Thereby obtaining the command voltage vector of the machine side converter
The control signal modulation module 7 is configured to modulate the control signal received from the grid-side converter control module 5 or the machine-side converter control module 6 by a preset modulation method, so as to obtain six-path two-two complementary control pulse signals of each IGBT device in the grid-side converter or the machine-side converter.
The control pulse output module 8 is configured to receive the six paths of control pulse signals output by the control signal modulation module 7, calculate time stamp information of a rising edge and a falling edge of each path of control pulse signal in a sampling period, and then transmit the six paths of control pulse signals of the network side converter or the machine side converter to the driving pulse output module 9 through a digital signal output module based on the time stamp in the RT-Lab digital real-time simulator.
The driving pulse output module 9 is used for amplifying the power of the six paths of control pulse signals output by the control pulse output module 8, so that the voltage level and the current intensity of the six paths of control pulse signals are enough to stably drive the high-frequency switch of the IGBT in the hardware system of the bidirectional AC-DC-AC PWM converter, and then the amplified six paths of control pulse signals are output to the grid-side converter or the machine-side converter, so that the control of the bidirectional AC-DC-AC PWM converter is completed. In this embodiment, the driving pulse output subsystem also has a photoelectric isolation function of input and output, so as to prevent the fault that the high voltage and large current of the power conversion subsystem are coupled to the control side and damage the controller interface.
The bidirectional AC-DC-AC PWM converter control system of the invention has the following working processes:
(1) Firstly, initializing a system and electrifying a power part, wherein a network side converter control module and a machine side converter control module do not work but a direct current side voltage stabilizing capacitor of the power part is continuously charged; after the control system is initialized, continuously sampling and processing a network side three-phase line voltage signal, a network side three-phase line current signal, a direct current side voltage signal, a machine side three-phase line current signal and a rotor position signal of a motor of the bidirectional AC-DC-AC PWM converter to obtain network side three-phase voltage, network side three-phase current, direct current side voltage, machine side three-phase current and rotor position angles;
(2) When the control system detects that the direct-current side voltage is lower than a given value and is in a stable state, the direct-current side voltage stabilizing capacitor is basically charged, and the grid-side converter control module 5 is enabled to enter a working state; when the grid-side converter is in a working state, coordinate transformation is carried out on a grid-side voltage signal, a grid-side current signal and a direct-current voltage signal which are acquired by a hardware system, the coordinate transformation is used as feedback quantity of a control algorithm, and meanwhile, generation of a control signal of the grid-side converter is realized according to a double closed-loop control strategy; the switching control of six paths of IGBT devices in the grid-side converter is completed after passing through the control signal modulation module 7 and the control pulse output module 8;
(3) After the network side converter enters a working state, the control system can continuously detect whether the direct current side voltage is stabilized at a given value; when the voltage of the direct current side is stabilized at a given value, the machine side converter control module 6 is made to enter a working state; when the machine side converter is in a working state, the direct-current side voltage signal, the machine side current signal and the rotor angle signal of the permanent magnet synchronous motor which are acquired by the hardware system are subjected to coordinate transformation and then used as feedback quantity of a control algorithm, and meanwhile, the generation of the control signal of the machine side converter is realized according to a double closed-loop control strategy; and the switching control of six paths of IGBT devices in the machine side converter is completed after passing through the control signal modulation module 7 and the control pulse output module 8.
In order to better illustrate the technical effect of the invention, the invention is experimentally verified by adopting a specific example.
Fig. 5 is a diagram of waveforms of voltage and current on the network side when the bi-directional ac-dc-ac PWM converter control system of the present embodiment is operating in steady state. As shown in fig. 5, the grid-side converter can operate in a unity power factor state at a power factor of 0.987 with a grid-side current THD of 4.36% at steady state.
Fig. 6 is a graph of dc side voltage waveforms of the bi-directional ac-dc-ac PWM converter control system according to the present embodiment operating in steady state. As shown in fig. 6, the grid-side converter control module 5 can stabilize the dc-side voltage around a given value at the time of steady-state, and the voltage fluctuation range is 2.79V.
Fig. 7 is a waveform diagram of the rotational speed of the permanent magnet synchronous motor when the bi-directional ac-dc-ac PWM converter control system of the present embodiment is operating in a steady state. As shown in fig. 7, the steady-state time-machine-side converter control module 6 can control the rotational speed of the permanent magnet synchronous motor around a given value, at which time the fluctuation range of the motor rotational speed is 0.31r/min.
Fig. 8 is a waveform diagram of the stator side current of the permanent magnet synchronous motor when the bi-directional ac-dc-ac PWM converter control system of the present embodiment is operating in steady state. As shown in fig. 8, the steady-state time machine side converter can control the stator current of the permanent magnet synchronous motor to be a relatively stable sine wave while stabilizing the rotating speed of the permanent magnet synchronous motor, and the THD of the steady-state time machine side converter is 6.04%.
In summary, the control system of the bidirectional AC-DC-AC PWM converter can effectively and stably work, and can rapidly and effectively control the bidirectional AC-DC-AC PWM converter.
While the foregoing describes illustrative embodiments of the present invention to facilitate an understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the embodiments, but is to be construed as protected by the accompanying claims insofar as various changes are within the spirit and scope of the present invention as defined and defined by the appended claims.
Claims (6)
1. The control system is characterized by comprising a signal acquisition module, a sampling signal processing module, a control logic switching module, a coordinate conversion module, a network side converter control module, a machine side converter control module, a control signal modulation module, a control pulse output module and a driving pulse output module, wherein the sampling signal processing module, the control logic switching module, the coordinate conversion module, the network side converter control module, the machine side converter control module, the control signal modulation module and the control pulse output module are realized in an RT-Lab digital real-time simulator;
the signal acquisition module is used for acquiring signals of the bidirectional AC-DC-AC converter, wherein the required signals comprise a network side three-phase line voltage signal and a network side three-phase line current signal of the network side converter, a direct current side voltage signal and a machine side three-phase line current signal of the machine side converter and a rotor position signal of the permanent magnet synchronous motor, and all the acquired signals are sent to the sampling signal processing module;
the sampling signal processing module is used for resolving the received network side three-phase line voltage signal, network side three-phase line current signal, direct current side voltage signal, machine side three-phase line current signal and rotor position signal to obtain actual values of the signals, namely network side three-phase voltage, network side three-phase current, direct current side voltage, machine side three-phase current and rotor position angle, stator three-phase current is obtained according to conversion of the machine side three-phase current, then the direct current side voltage is sent to the control logic switching module and the network side converter control module, the network side three-phase voltage, the network side three-phase current and the stator three-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 method for the solution is as follows:
for the three-phase line voltage signal of the net side, the three-phase line current signal of the net side, the voltage signal of the direct current side and the three-phase line current signal of the machine side, an analog-digital converter in the real-time simulation machine of the RT-Lab is adopted to replace the digital signal, and then the actual values of the three-phase line voltage of the net side, the three-phase line current of the net side, the voltage of the direct current side and the three-phase line current of the machine side are obtained after amplitude conversion and phase conversion; according to the conversion of the side three-phase current, the stator three-phase current is obtained;
for the rotor position signal, resolving according to a rotor position signal acquisition method to obtain an actual value of a rotor position angle;
the control logic switching module is used for judging a currently required control mode according to the voltage of the direct current side, and the specific method comprises the following steps: if the direct-current side voltage is unstable, the control is not performed, if the direct-current side voltage is smaller than a preset given value and is in a stable state, an enabling signal is sent to the network side converter control module, and if the machine side three-phase voltage is stable at the given value, an enabling signal is sent to the machine side converter control module;
the coordinate transformation module is used for performing Clark transformation and Park transformation on the network side three-phase voltage, the network side three-phase current and the stator three-phase current to obtain network side voltage, network side current and stator current under a two-phase rotating coordinate system, then sending the network side voltage and the network side current to the network side converter control module, and sending the stator current to the machine side converter control module;
when receiving the enabling signal sent by the control logic switching module, the network side converter control module calculates a command space voltage vector of the network side according to the network side voltage, the network side current and the direct current side voltage and sends the command space voltage vector to the control signal modulation module;
when receiving the enabling signal sent by the control logic switching module, the machine side converter control module calculates a machine side command space voltage vector according to the rotor position angle and the stator current and sends the command space voltage vector to the control signal modulation module;
the control signal modulation module is used for modulating control signals received from the grid-side converter control module or the machine-side converter control module by adopting a preset modulation mode to obtain six paths of two-to-two complementary control pulse signals of each IGBT device in the grid-side converter or the machine-side converter;
the control pulse output module is used for receiving the six paths of control pulse signals output by the control signal modulation module, calculating the time stamp information of the rising edge and the falling edge of each path of control pulse signal in one sampling period, and then transmitting the six paths of control pulse signals of the grid-side converter or the machine-side converter to the driving pulse output module through the digital signal output module based on the time stamp in the RT-Lab digital real-time simulator;
the driving pulse output module is used for amplifying the power of the six paths of control pulse signals output by the control pulse output module, so that the voltage level and the current intensity of the six paths of control pulse signals are enough to stably drive the high-frequency switch of the IGBT in the hardware system of the bidirectional AC-DC-AC PWM converter, and then the amplified six paths of control pulse signals are output to the grid-side converter or the machine-side converter, so that the control of the bidirectional AC-DC-AC PWM converter is completed.
2. The bi-directional ac-dc-ac PWM converter control system according to claim 1, wherein the collection of the grid-side three-phase line voltage signal and the dc-side voltage signal uses a closed-loop hall voltage transformer, and the collection of the grid-side three-phase line current signal and the machine-side three-phase line current signal uses a closed-loop hall current transformer.
3. The bi-directional ac-dc-ac PWM converter control system according to claim 1, wherein the rotor position signal is collected using an incremental ABZ phase photoelectric encoder.
4. The bi-directional ac-dc-ac PWM converter control system according to claim 1, wherein relay protection modules are provided at sampling points of the signal sampling module at the network side and the machine side, respectively.
5. The bi-directional ac-dc-ac PWM converter control system of claim 1, wherein the grid-side converter control module comprises a voltage outer loop control module and a current inner loop control module, wherein:
the voltage outer ring control module is used for keeping the voltage level of the direct current side stable, and obtaining the given value of the d-axis and q-axis components of the network side current after the difference between the given value and the actual value of the direct current side voltage passes through the voltage outer ring PI regulatorWill->As a command signal for the inner loop of the current;
the electric current inner loop control module is used for controlling the alternating current side current by taking the rapidity as a main index, so that the controlled current can rapidly track the command signal, and the output of the command signal after passing through the current inner loop PI regulator is the command space voltage vector of the network sideInstruction space voltage vector>The calculation formula of (2) is as follows:
wherein ,respectively representing the given values of d-axis and q-axis components of the network side voltage, K iP Representing the scaling factor, K, of a network-side current loop PI regulator iI The integral coefficient of the current loop PI regulator at the network side is represented, s represents the switching function, i g,d 、i g,q Respectively representing d-axis and q-axis components of the network side current, ω represents the network side voltage angular frequency, L represents the network side inductance, e d 、e q The d-axis and q-axis components of the grid-side voltage are shown, respectively.
6. The bi-directional ac-dc-ac PWM converter control system of claim 1, wherein the grid-side converter control module comprises a speed outer loop control module and a current inner loop control module, wherein:
the rotating speed outer ring control module is used for controlling the stability of the rotating speed of the three-phase permanent magnet synchronous motor by controlling the rotor position angle theta r Deriving time to obtain current rotational speed omega of rotor r Which is related to the rotation speed set valueAfter passing through the speed outer ring PI regulator, the given value of the d-axis and q-axis components of the stator current is obtained>Will give->As a command signal for the inner loop of the current;
the current inner loop control module is used for adjusting the stator current of the three-phase PMSM by taking the rapidity as a main index, so that the controlled current can rapidly track the command signal output by the voltage outer loop PI regulator, thereby achieving the control of the electromagnetic torque of the current inner loop PI regulator, and the output of the command signal after passing through the current inner loop PI regulator is the command space voltage vector of the machine sideInstruction space voltage vector>The calculation formula of (2) is as follows:
wherein ,respectively representing given values of d-axis and q-axis components of stator voltage, K i ′ P Representing the scaling factor, K, of the machine side current loop PI regulator i ′ I Representing the integral coefficient of the side current loop PI regulator, s representing the switching function, i s,d 、i s,q Respectively represent d-axis and q-axis components of stator current, L d 、L q Respectively represent d-axis and q-axis components and n of three-phase stator winding equivalent inductance p Representing the pole pair number, ψ, of a permanent magnet synchronous motor f The maximum value of flux linkage generated when the permanent magnet magnetic field and the stator winding are linked when the rotor rotates.
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