SUMMERY OF THE UTILITY MODEL
In order to overcome the shortcoming and the deficiency that prior art exists, the utility model provides a grid-connected inverter current loop control device based on linear active disturbance rejection control.
The utility model adopts the following technical scheme:
a grid-connected inverter current loop control device based on linear active disturbance rejection control comprises an inversion module, a signal detection and adjustment module, a linear active disturbance rejection controller module and a PWM signal output module;
the input end of the inversion module is connected with a direct current load, and the output end of the inversion module is connected with an alternating current power grid;
the signal detection and adjustment module samples the voltage and current of the alternating current power grid and outputs d-axis current igdAnd q-axis current igq;
The input end of the linear active disturbance rejection controller module receives d-axis current igdAnd q-axis current igqAnd corresponding set value igd *、igq *The output end of the PWM signal output module is connected with the input end of the PWM signal output module, and the output end of the PWM signal output module is connected with the inversion module.
The inversion module comprises an LCL filter and a three-phase full-bridge inverter which are sequentially connected.
The signal detection and adjustment module comprises a power grid voltage and current sampling and holding unit, a phase-locked loop and a coordinate transformation unit which are sequentially connected.
The PWM signal output module is composed of a coordinate inverse transformation unit and an SVPWM generator which are connected in sequence.
The linear active disturbance rejection controller module comprises a linear extended state observer, a first adder-subtractor, a first scale coefficient module, a second adder-subtractor, a second scale coefficient module, a third adder-subtractor, a third scale coefficient module, a fourth adder-subtractor, a fifth adder-subtractor, a first compensation factor, a second compensation factor, a first low-pass filtering unit, a second low-pass filtering unit and a feedforward decoupling term;
the connection mode is as follows:
the input end of the linear extended state observer is connected with the output signal of the second low-pass filtering unit and the output signal of the first compensation factor, the linear extended state observer outputs four observed state variables, the four observed state variables are respectively connected with the subtraction input end of the first adder-subtractor, the input end of the second proportionality coefficient module, the input end of the third proportionality coefficient module and the subtraction input end of the fourth adder-subtractor, and the addition input end of the first adder-subtractor inputs a d-axis current given value
The output end of the first scaling coefficient module is connected with the input end of the first adder-subtractor;
the subtraction input end of the second adder-subtractor is connected with the output end of the second proportionality coefficient module, the output end of the second adder-subtractor is connected with the addition input end of the third adder-subtractor, the subtraction input end of the third adder-subtractor is connected with the output end of the third proportionality coefficient module, the output end of the third adder-subtractor is connected with the addition input end of the fourth adder-subtractor, the output end of the fourth adder-subtractor is connected with the input end of the second compensation factor, the output end of the second compensation factor is connected with the addition input end of the fifth adder-subtractor, the subtraction input end of the fifth adder-subtractor is connected with the output end of the feedforward decoupling term, andsdthe first output end of the fifth subtractor is connected with the input end of the first low-pass filtering unit, and the second output end of the fifth subtractor outputs a voltage signal uidTo the PWM signal output module; the output end of the first low-pass filtering unit is connected with the input end of the first compensation factor, and the input end of the second low-pass filtering unit inputs d-axis real-time current igdThe input end of the feedforward decoupling term inputs q-axis real-time current igq。
The linear extended state observer comprises five adders and subtractors, four integrators, four observer coefficient modules and a proportional coefficient module.
The full-bridge inverter comprises six IGBT switching tubes.
The linear active disturbance rejection controller module is of fourth order.
The linear extended state observer is used for observing and compensating total disturbance sum in real time, and the whole device is simplified into a third-order system after compensation.
The utility model has the advantages that:
(1) the utility model discloses based on linear auto-disturbance controller control, can observe in real time and compensate as disturbing in the system through the expansion state observer with the coupling, do not rely on the accurate mathematical model of object, have very strong robustness. Meanwhile, aiming at the problems that the traditional active disturbance rejection control parameter selection is complex, the system analysis is complex due to nonlinear control and the like, the design and analysis difficulty of the controller can be greatly simplified by adopting linear active disturbance rejection control to replace nonlinear active disturbance rejection control;
(2) the utility model observes the state variable through the linear state observer LESO, and does not need to add an additional sensor in the capacitance branch, thereby reducing the volume and the weight of the device and lowering the cost;
(3) the problem of parameter configuration of the linear active disturbance rejection controller can be simplified to omegaoAnd ωcThe design of the method effectively solves the problem of parameter design complexity caused by the increase of the order of the traditional active disturbance rejection controller;
(4) at the output u of the pair controlleriAfter the(s) and the feedback input y(s) enter the low-pass filter and the main coupling amount is adopted for feedforward decoupling, the coupling problem and the current spike problem of the system are well solved, and when the load of the system is changed, the current on the network side can track the current set value without overshoot, so that the system has stronger robustness;
(5) the device is suitable for inversion occasions with high requirements on cost, size and grid-connected current quality, and is particularly suitable for distributed grid-connected inversion occasions which are easy to generate a large number of high-frequency harmonics and have high requirements on system stability in the current conversion process.
Examples
A grid-connected inverter current loop control device based on linear active disturbance rejection control mainly aims at the fact that an LCL type grid-connected inverter has the characteristics of nonlinearity, strong coupling, strong parameter change disturbance and the like, and the double-loop PI control in the prior art cannot achieve a satisfactory control effect. The utility model discloses a on the basis that traditional PID controller was replaced to linear auto-disturbance-rejection controller, to controller output uiAnd(s) and the feedback input y(s) are subjected to low-pass filtering and feedforward decoupling on the main coupling quantity, so that the coupling problem and the current spike problem of the system are well solved, high-quality network measurement current can be obtained, and the system has stronger robustness. The device can solve the resonance and coupling problems of the LCL filter, and does not need to increase extra hardware cost.
The utility model comprises an inversion module, a signal detection and adjustment module, a linear active disturbance rejection controller module and a PWM signal output module;
the inversion module is composed of an LCL filter and a three-phase full-bridge inverter which are sequentially connected, the input end of the inversion module is connected with a direct-current load through a direct-current bus capacitor, and the output end of the inversion module is connected with an alternating-current power grid.
In this embodiment, the LCL filter includes three parallel branches, each of which is formed by connecting two inductors Lg and Li and two resistors Rg and Ri in series, one end of each of the three capacitors is connected to the three branches, and the other ends of the three capacitors are connected to each other.
The signal detection and adjustment module comprises a power grid current sampling and holding unit, a phase-locked loop and a coordinate transformation unit which are sequentially connected, and is used for sampling voltage and current signals of an alternating current power grid through a Hall voltage and current sensor, outputting d-axis current and q-axis current real-time values obtained through transformation and sending the d-axis current and q-axis current real-time values to the linear active disturbance rejection controller module;
the input end of the linear active disturbance rejection control module inputs a real-time d-axis current value and a real-time q-axis current value i from the signal regulation detection modulegd、igqAnd its corresponding set value igd *、igq *The output end of the linear active disturbance rejection control module outputs the control quantity u of the d-axis current value and the q-axis current valueidAnd uiqSending the signal to a PWM signal output module;
the input of the PWM signal output module is uidAnd uiqAnd theta derived from the phase-locked loop. And finally, 6 paths of PWM signals are output to six IGBT switching tubes of a full-bridge inverter in the inversion module, so that the inversion module is controlled.
The PWM signal output module is composed of a coordinate inverse transformation unit and an SVPWM generator which are connected in sequence. The coordinate inverse transformation unit is connected with the output end of the linear active disturbance rejection control module, and the SVPWM generator is connected with the full-bridge inverter.
The linear active disturbance rejection controller module in fig. 1 includes two parts, the two parts have the same structure, and one part is used for controlling igdPart for controlling igqThe control process is the same.
The Linear Active Disturbance Rejection Controller (LADRC) comprises a Linear Extended State Observer (LESO), a first adder-subtractor, and a first scale coefficient module kpA second adder-subtractor and a second proportionality coefficient module kd1A third adder-subtractor and a third proportionality coefficient module kd2A fourth adder-subtractor, a fifth adder-subtractor and a first compensation factorb0A second compensation factor 1/b0The feed-forward decoupling module comprises a first low-pass filtering unit, a second low-pass filtering unit and a feed-forward decoupling term.
In the present embodiment, H(s) denotes a low-pass filter unit.
The utility model discloses utilize linear extended state observer to survey state variable and to total disturbance with survey in real time and compensate, system after the compensation can be simplified into a third-order system, and then can simplify linear parameter configuration problem for observer bandwidth omegaoAnd controller bandwidth ωcThe design of (3) realizes the design of more conveniently realizing the Linear Error Feedback control rate LSEF (Linear State Error Feedback).
Active current i
gdAnd a reactive current i
gqThe control process of the controller is the same, and the only difference is that in order to ensure the unit power factor operation of the inverter, the given value of the reactive current is generally set
Is set to 0.
Another given value igd *Is calculated through the voltage outer loop and is given, because the utility model discloses mainly focus on the electric current inner loop, do not focus on the voltage outer loop, therefore do not do the repeated description here. The main purpose of this statement is to emphasize igqController and igdThe design of the controller is the same, the only difference is the given value, igq *Is set to 0, igd *It is varied according to the output of the voltage loop.
The specific connection mode of the linear active disturbance rejection controller module is as follows:
the input end of the linear extended state observer is connected with the output signal i 'of the second low-pass filtering unit'
gdOutput signal u 'of the first compensation factor'
id*b
0Said linear extended state observer outputting four observed state variables
ωLg、
Four observed state variables are respectively connected with the subtraction input end of the first adder-subtractor and the second proportionality coefficient module k
d1Input end of, third scale factor module k
d2The addition input end of the first adder-subtractor inputs the d-axis current given value
The output end of the first scaling factor module k
pThe output end of the first scale coefficient module is connected with the addition input end of the second adder-subtractor;
the subtraction input end of the second adder-subtractor is connected with the output end of the second proportionality coefficient module, the output end of the second adder-subtractor is connected with the addition input end of the third adder-subtractor, the subtraction input end of the third adder-subtractor is connected with the output end of the third proportionality coefficient module, the output end of the third adder-subtractor is connected with the addition input end of the fourth adder-subtractor, the output end of the fourth adder-subtractor is connected with the input end of the second compensation factor, the output end of the second compensation factor is connected with the addition input end of the fifth adder-subtractor, the subtraction input end of the fifth adder-subtractor is connected with the output end of the feedforward decoupling term, andsdthe first output end of the fifth subtractor is connected with the input end of the first low-pass filtering unit, and the second output end of the fifth subtractor outputs a voltage signal uidTo the PWM signal output module; the output end of the first low-pass filtering unit is connected with the input end of the first compensation factor, and the input end of the second low-pass filtering unit inputs d-axis real-time current igdThe input end of the feedforward decoupling term omega Lg inputs a q-axis real-time current igq。
The linear extended state observer comprises five adders and subtractors, four integrators and a first scale coefficient module
first observer coefficient module β
1a second observer coefficient module β
2and a third observer coefficient block beta
3Fourth observer coefficient modelblock beta
4And a first scale factor module
The parameters of each part of the grid-connected inverter current loop control device in the embodiment are shown in table 1:
TABLE 1
The control process of this embodiment is as follows:
from the mathematical model of the LCL inverter, the inverter-side inductance L is known to take into account the change in the system parameters
i′=L
i+ΔL
iNet side inductance value L
g′=L
g+ΔL
gValue of filter capacitance C
f′=C
f+ΔC
fAt a resonant frequency of
The state space expression is as follows:
inverter side voltage U at this timeiCurrent I to network sidegThe transfer function of (a) is:
for the resonant frequency, along with the fluctuation of the filter parameters, the resonant frequency can also shift, which can cause the inaccuracy of modeling, further affect the control effect and even bring the stability problem.
The dynamic characteristics of the current in the rotating coordinate system can be represented by a third-order differential equation shown in equation (3):
wherein the parameters
f
dAnd f
qThe total disturbance of active components and reactive components is expressed by the difference, including external disturbance and internal disturbance of the system, the external disturbance mainly comprises grid voltage fluctuation and the like, and the internal disturbance comprises system parameter change, mutual coupling between dq axes and the like. Adding to the expanded state, the d-axis differential equation in equation (3) can be written as follows:
wherein h isdAs a total disturbance fdWith respect to the reciprocal of time, igd=x1d,dx1d/dt=x2d,dx2d/dt=x3d,fd=x4dThe remaining parameters are given in the following formula:
according to equation (4), a fourth-order linear extended state observer of equation (6) below can be established, the structure of which is shown in fig. 3.
Wherein
Values of state variables, L, observed by an observer
d=[β
1β
2β
3β
4]
TFor the coefficient matrix of the state observer, by selecting a suitable coefficient matrix of the state observer, the LESO can realize real-time tracking of each state variable in the formula (6), that is
The system is compensated by the LESO and then becomes an integral series type structure, and can be controlled by a proportional-derivative controller (PD).
According to the pole allocation method of the reconstructed state observation feedback control system, in order to realize the fast overshoot-free tracking of the system on the reference signal, the parameters of the linear extended state observer LESO and the linear error feedback control rate LSEF can be respectively set as follows:
thus, the LADRC control parameter configuration problem can be simplified to ωoAnd ωcThe design of (2) effectively solves the problem of parameter design complexity caused by the improvement of the order of the controller.
Discretizing the data by adopting a backward difference mode with stronger stability. For u is pairedi(s) and y(s) are added to low pass filtering
After discretization, the transfer function of the discretized domain is shown as the formula (9):
wherein, ω isLIs the cut-off frequency, T, of the low-pass filtersFor the system control period, ui(k-1) is the value of the last time instant of the filter output. Bandwidth omega of low-pass filterLMust be larger than the bandwidth ω of the linear extended state observero. Taking comprehensive consideration, selecting the cut-off frequency omega of the low-pass filterL=1.6ωo。
When the main feedforward quantity decoupling is carried out, the selected feedforward decoupling terms are as follows:
the structure diagram of the d-axis control is shown in fig. 2, and since the q-axis related control is similar to the d-axis, it is not repeated here.
The present embodiment was designed by using the above-mentioned scheme, and tests were performed when the inductance and capacitance values of the LCL were disturbed, and the obtained results are shown in fig. 4(a), 4(b), 4(c), and 4(d)
In fig. 1, SPLL represents a phase-locked loop, Linear ESO represents a Linear extended state observer, and a Controller is a general name of a first adder-subtractor, a first proportional coefficient module, a second adder-subtractor, a second proportional coefficient module, a third adder-subtractor, a third proportional coefficient module, a fourth adder-subtractor, a fifth adder-subtractor, a first compensation factor, a second compensation factor, a first low-pass filtering unit, a second low-pass filtering unit, and a feedforward decoupling term.
The LCL grid-connected inverter current loop control based on the linear active disturbance rejection control can observe and compensate coupling as system internal disturbance in real time through an extended state observer, and the method does not depend on an accurate mathematical model of an object and has very strong robustness. Meanwhile, aiming at the problems that the traditional active disturbance rejection control parameter selection is complex, the system analysis is complex due to nonlinear control and the like, the design and analysis difficulty of the controller can be greatly simplified by replacing the nonlinear active disturbance rejection control with the linear active disturbance rejection control.
When the LADRC controller is switched in, the grid side output current is easy to generate spike pulses (before the IGBT is in a turn-off state), although the pulses have no influence on the steady-state performance, overcurrent alarm of the grid-connected inverter can be caused, and even the grid-connected inverter can be damaged. In order to prevent the phenomenon, the coupling value with a larger quantity can be decoupled in a feedforward decoupling mode, and the other coupling values with a smaller quantity are still decoupled through an extended state observer, so that the observation load of the observer is reduced, and the stability of a signal cut-in instant control system is improved.
The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be equivalent replacement modes, and all are included in the scope of the present invention.