CN106602600A - Single-loop control method for LC-type three-phase grid-connected inversion system - Google Patents

Abstract

The invention relates to a single-loop control method for an LC-type three-phase grid-connected inversion system. A PCI controller is suitable for a three-phase abc coordinate system, and can directly control an AC signal in the three-phase abc coordinate system. Repeated control is a control strategy based on the inner membrane principle, and can reduce the impact caused by a dead zone and power grid voltage periodic disturbance, and also can achieve the tracking of a system without static errors. The method with the combination of two sides can directly and effectively control an AC amount, and also combines with an LC-type filter for filtering, thereby enabling an inversion current to meet the grid-connection requirements of a power factor, and enabling the harmonic distortion rate to accord with the related standard. The method employs the single-loop control, is directly used for controlling the AC amount, does not need to carry out coordinate conversion, saves the cost for the whole cost, improves the grid-connected current waveform quality, tracking precision and power factor, and also can guarantee the safe and stable operation of the who control system.

Description

The monocyclic control method of LC type three-phase grid-connected inverting systems

Technical field

The present invention relates to a kind of power grid control technology, more particularly to a kind of based on ratio plural number integration PCI and repetition The monocyclic control method of LC type three-phase grid-connected inverting systems of complex controll in parallel.

Background technology

In recent years, be becoming tight the supply day of the non-renewable energy resources such as oil, coal and natural gas, develop wind energy and The new forms of energy such as solar energy are increasingly valued by the people.But during to new energy development and utilization, appropriate design is simultaneously Net inverse control system is particularly significant.Generally, for the control of combining inverter, mainly there are a two indices, one Controlled output current with line voltage with frequency homophase, two be the percent harmonic distortion (THD) of controlled output current meet it is related simultaneously Network mark is accurate.

The controlled output current of combining inverter has to pass through wave filter and can just filter higher hamonic wave, at present more conventional filter Ripple device mainly has three kinds of L-type, LC types and LCL type.Wherein for L-type wave filter, its structure is most simple, but filter effect It is poor；For LC mode filters, its be primarily adapted for use in it is double mode under, and when grid-connected filter capacitor C equivalent to local negative Carry, have no filter action；For LCL type wave filter, filter capacitor C plays a part of higher hamonic wave passage, can certain journey The Eliminate highter harmonic of degree, filter effect is optimum, but LCL type wave filter is third-order system, there is resonance peak, and in resonance frequency Gain is larger at rate, easily causes the unstable of system.When the present invention is using current source inverter, signal is adjusted by pulse width System (PWM) signal triggering modulation, while circuit output voltage can be produced compared with multiple-harmonic at switching frequency, it is necessary to which Rational choice is filtered Ripple device is with harmonic carcellation.Complicated compared to LCL type FILTER TO CONTROL strategy, the control of LC mode filters is simple, is conducive to grid-connected inverse Become the independent operating of device, among being usually used in engineering practice.At this stage for the research of combining inverter control strategy is mainly concentrated In two kinds of current-control type and voltage-controlled type.For current-control type, control mode mainly has in proportional plus integral control (PI), the ratio resonance control polytype such as (PR) and fuzzy control, every kind of control method respectively has pluses and minuses；For voltage control For type processed, control mode mainly has invariable power (PQ) control, constant pressure/constant frequency (V/F) control and sagging (Droop) control three Kind.Analysis of both more than comprehensive, research LC type filtering parallel network reverse control method have highly important theory significance and Practical significance.

The content of the invention

The present invention be directed to the problem that combining inverter control is present, it is proposed that a kind of LC types three-phase grid-connected inverting system list Ring control method, is capable of the method for direct effective control of ac, is filtered in combination with LC mode filters so that inversion electricity Stream meets the grid-connected requirement of power factor, and percent harmonic distortion meets relevant criterion.The method is monocyclic control, is directly used in control and hands over Flow variables, without the need for carrying out coordinate transform, save whole system cost, improve grid-connected current waveform quality, tracking accuracy and work( Rate factor, while being able to ensure that the safe and stable operation of whole control system.

The technical scheme is that：A kind of monocyclic control method of LC types three-phase grid-connected inverting system, LC type three-phase grids Inversion system includes DC input voitage source U_dc, based on pulse width modulation control three-phase inverter, LC wave filters, grid line Road equivalent resistance R_a、R_b、R_c, net side three-phase current detection transmitter, three be used for what current error signal was adjusted Ratio plural number integration pci controller and three repetitive controllers for being adjusted to current error signal, first in net side In the presence of three-phase current detection transmitter, actual grid-connected current i of three-phase is obtained_a、i_b、i_c, and the value is referred to corresponding three-phase Make electric current i_aref、i_bref、i_crefRelatively make the difference, obtain correspondence error signal；Then the error signal of each flows to corresponding one The controller of PCI compound compositions in parallel with Repetitive controller, repeated controller is controlled acquisition output signal and Jing PCI Controller is controlled acquisition output signal and is added, and obtains output signal total under complex controll, and total signal flows to PWM moulds Block, and trigger modulated signal；Jing PWM modules output switch drive signal after most, the signal controls grid-connected inverse Jing after drive circuit Become the on and off of device switching tube, and then control amplitude, phase place and the current quality of grid-connected inverting system output current.

The Mathematical Modeling of the pci controller is：

Closed loop transfer function, is when system correspondence PCI is controlled：

Wherein ω be mains frequency, ω₀It is PWM equivalent gains, I for given a-c cycle, K_refS () is specified current flow ginseng Consider, I₀S () is current output；

System closed loop passes the amplitude versus frequency characte and phase-frequency characteristic of letter when PCI is controlled, respectively

The Mathematical Modeling of the repetitive controller is：

Wherein Z^-NFor delay link, N values 200, Q (z) values 0.95, G_c(z) be compensator, G_c(z)=K_r·z^k·S (z), wherein K_rTo repeat controller gain, value is 0.7, z^kFor lead compensation link, S (z) is low pass filter, and S (z) =S₁(z)S₂(z), wherein S₁(z) be trapper, S₂Z () is second-order low-pass filter.

The beneficial effects of the present invention is：The monocyclic control method of LC types three-phase grid-connected inverting system of the present invention, is applied to three Mutually static abc coordinate systems, realize the directly optimal method to AC signal and control, while control accuracy is higher, power factor is more Height, tracking effect is more preferable and system reliability is higher, is suitable for the new-energy grid-connected of photovoltaic generation and wind-power electricity generation etc. System, while the control method range of application is wider, among other single-phase or three-phase converter methods can be extended to.

Description of the drawings

Fig. 1 is the overall structure block diagram of the monocyclic control strategy of LC types grid-connected inverting system of the present invention；

Fig. 2 is three-phase pci controller structured flowchart in the present invention；

Fig. 3 is repetitive controller structured flowchart in the present invention；

Fig. 4 be present invention show Repetitive controller effect under whole system Bode diagram；

Fig. 5 is present invention show three-phase abc grid-connected current figures；

Fig. 6 is the lower grid-connected current percent harmonic distortion figure of the inventive method control.

Specific embodiment

Accompanying drawing 1 is the monocyclic control of LC type grid-connected inverting systems based on PCI and repetition complex controll in parallel proposed by the present invention The overall structure block diagram of system strategy, wherein mainly including DC input voitage source U_dc, based on pulse width modulation control three-phase (inductance of connection inverter bridge side is L for inverter, LC wave filters_a、L_b、L_c, three filter capacitor C_a、C_b、C_c), power network line is equivalent Resistance R_a、R_b、R_c, net side three-phase current detection transmitter, three PCI for being used to be adjusted current error signal are controlled Device processed, three repetitive controllers for being adjusted to current error signal.Major control process is：First in net side three-phase In the presence of current detecting transmitter, actual grid-connected current i of three-phase is obtained_a、i_b、i_c, and the value and the instruction of corresponding three-phase is electric Stream i_aref、i_bref、i_crefRelatively make the difference, obtain correspondence error signal e_ix(x=a, b, c)；Then error signal flows to PCI with weight Multiple control is in parallel to be combined the controller for constituting, and on the one hand repeated controller is controlled acquisition output signal, another aspect Jing Pci controller is controlled acquisition output signal, and both are added and obtain output signal total under Compound Control Strategy, while this is total Signal flow to PWM module, and trigger modulated signal；Jing PWM modules output switch drive signal after most, signal Jing drives electricity The on and off of combining inverter switching tube is controlled behind road, and then controls amplitude, the phase place of grid-connected inverting system output current And current quality.

During the entire process of here invention is proposed, actual imitating mainly is carried out to a LC types three-phase grid-connected inverting system True checking, the correctness and feasibility of the present invention are illustrated with this.Wherein specific simulation parameter is：Direct voltage source voltage 500V, line voltage virtual value 220V, line voltage frequency 50Hz, PWM switching frequency 10KHz, filter inductance L are 2.52mH, Filter capacitor C is 20 μ F, and mains-power circuit equivalent resistance R is 0.5 Ω.A phase reference current 30sin (100 π t) A, b phase reference currents 30sin (100 π t-2 π/3) A, c phase reference current 30sin (100 π t+2 π/3) A.

PCI (ratio plural number integration) controllers and repetitive controller structural frames that accompanying drawing 2 and accompanying drawing 3 are applied for the present invention Figure, wherein pci controller are applied to three-phase abc coordinate systems, can directly control the AC signal under three-phase abc coordinate systems, and Pci controller parameter k_p=0.5, k_i=25.Repetitive controller is a kind of control strategy based on inner membrance principle, it is possible to reduce such as The impact of the generation such as dead band and line voltage periodic disturbance, while the DAZ gene of system can be realized.

Accompanying drawing 2 shows the system structure model of three-phase pci controller, and the Mathematical Modeling of ratio plural number integration control is

Closed loop transfer function, is when system correspondence PCI is controlled

Wherein ω be mains frequency, ω₀It is PWM equivalent gains, I for given a-c cycle, K_refS () is specified current flow ginseng Consider, I₀S () is current output.

System closed loop passes the amplitude versus frequency characte and phase-frequency characteristic of letter when PCI is controlled, respectively

Fig. 3 shows the structural model of repetitive controller, and the Mathematical Modeling of repeated controlling system is

Wherein Z^-NFor delay link, N values 200, Q (z) values 0.95, G_cZ () is compensator, and typically G_c(z)=K_r· z^kS (z), wherein K_rTo repeat controller gain, value is 0.7, z^kFor lead compensation link, S (z) is low pass filter, and S (z)=S₁(z)S₂(z), wherein S₁(z) be trapper, S₂Z () is second-order low-pass filter.By system parameters L=2.52mH, C =20 μ F, R=0.5 Ω obtain LC types controlled device biography letter after bringing into

Discretization has

Choose comb filter to replace trapper, its transmission function is

Take z=e^jθ, can obtain

Work as S₁(θ) when=0, a=2, S₁Z the decay of () to CF is most strong, and have

2cos (q θ)+2=0

TakeQ=9 is obtained, therefore

Wherein α be constant, θ be discrete phase angle, ω_cFor system natural frequencies, while parameter q can affect comb filter Trap frequency.

The present invention chooses second-order low-pass filter to suppress high frequency componentses, and cut-off frequency is 5000rad/s, and damped coefficient is 0.707, then

Discretization has

Fig. 4 shows the Bode diagram of the whole system under Repetitive controller effect, it is seen that the resonance peak of controlled device P curve With trapper S₁Curve maximum attenuation value is corresponding, so can preferably compensate resonance peak, but the high frequency attenuation of trapper Characteristic is poor, and after second-order low-pass filter is chosen, high band disturbance is suppressed the present invention, the resonance peak and phase of controlled device Position is all preferably compensated.

Fig. 5 shows three-phase abc grid-connected current situations, it is seen that the new controller of Jing PCI and repetition compound composition in parallel Afterwards, three-phase abc grid-connected currents and its respective corresponding line voltage almost homophase, can realize the grid-connected requirement of unity power factor, And then show that Novel Control proposed by the present invention has preferable followability.

Lower grid-connected current percent harmonic distortion figure is controlled as shown in Figure 6, and table 1 shows grid-connected electricity under another three kinds of Different Strategies control The corresponding THD values of the situation of stream percent harmonic distortion (THD), wherein conventional PI control are maximum, are 4.85%, after adding Repetitive controller It is promoted to 2.44%；The corresponding THD values of improvement PCI controls are compared conventional PI control and have been reduced, and are 3.32%, add and repeat to control System constitutes NEW TYPE OF COMPOSITE controller control effect optimum proposed by the present invention, and THD values are minimum, reach 1.70.

Table 1

Claims (3)

1. a kind of monocyclic control method of LC types three-phase grid-connected inverting system, it is characterised in that LC type three-phase grid-connected inverting system bags Include DC input voitage source U_dc, based on pulse width modulation control three-phase inverter, LC wave filters, power network line equivalent resistance R_a、R_b、R_c, net side three-phase current detection transmitter, three ratio plural numbers for being used to be adjusted current error signal are long-pending Divide pci controller and three repetitive controllers for being adjusted to current error signal, examine in net side three-phase current first In the presence of surveying transmitter, actual grid-connected current i of three-phase is obtained_a、i_b、i_c, and by the value and corresponding three-phase instruction current i_aref、i_bref、i_crefRelatively make the difference, obtain correspondence error signal；Then the error signal of each flow to a corresponding PCI with One Repetitive controller parallel connection is combined the controller of composition, and repeated controller is controlled acquisition output signal and Jing PCI controls Device is controlled acquisition output signal and is added, and obtains output signal total under complex controll, and total signal flows to PWM module, And trigger modulated signal；Jing PWM modules output switch drive signal after most, the signal controls combining inverter Jing after drive circuit The on and off of switching tube, and then control amplitude, phase place and the current quality of grid-connected inverting system output current.

2. the monocyclic control method of LC types three-phase grid-connected inverting system according to claim 1, it is characterised in that the PCI controls The Mathematical Modeling of device processed is：

$G_{PCI}=K_p+\frac{K_i}{s-{\mathrm{j\ω}}_0}$

Closed loop transfer function, is when system correspondence PCI is controlled：

$T\left(s\right)=\frac{I_0\left(s\right)}{I_{ref}\left(s\right)}=\frac{a_{1}s+a_0}{b_3{s}^3+b_2{s}^2+b_{1}s+b_0}$

$\left\{\begin{array}{c}{a}_1=-{\mathrm{Kk}}_p\\ a_2=-{\mathrm{Kk}}_i-{\mathrm{j\ω}}_0-{\mathrm{Kk}}_p\\ b_3=LC\\ b_2=RC-{\mathrm{j\ω}}_{0}LC\\ b_1=-{\mathrm{Kk}}_p+1+{\mathrm{j\ω}}_{0}RC\\ b_0=-{\mathrm{Kk}}_i-{\mathrm{j\ω}}_0(1+{\mathrm{Kk}}_p)\end{array}\right.$

Wherein ω be mains frequency, ω₀It is PWM equivalent gains, I for given a-c cycle, K_ref(s) be specified current flow reference quantity, I₀S () is current output；

System closed loop passes the amplitude versus frequency characte and phase-frequency characteristic of letter when PCI is controlled, respectively

$\left|T\left(s\right)\right|=\frac{K\sqrt{{k_i}^2+{k_p}^2{(\mathrm{\ω}-{\mathrm{\ω}}_0)}^2}}{\sqrt{m^2+n^2{(\mathrm{\ω}-{\mathrm{\ω}}_0)}^2}}$

$\left\{\begin{array}{c}m={\mathrm{Kk}}_i+{\mathrm{RC\ω\ω}}_0-{\mathrm{RC\ω}}^2\\ n={\mathrm{LC\ω}}^2-{\mathrm{Kk}}_p-1\end{array}\right.$

$\∠T\left(s\right)=\arctan \left(\frac{k_p(\mathrm{\ω}-{\mathrm{\ω}}_0)}{k_i}\right)-\arctan \left(\frac{({\mathrm{LC\ω}}^2-{\mathrm{Kk}}_p-1)(\mathrm{\ω}-{\mathrm{\ω}}_0)}{{\mathrm{Kk}}_i+{\mathrm{RC\ω\ω}}_0-{\mathrm{RC\ω}}^2}\right).$

3. the monocyclic control method of LC types three-phase grid-connected inverting system according to claim 1, it is characterised in that described to repeat to control The Mathematical Modeling of device processed is

Wherein Z^-NFor delay link, N values 200, Q (z) values 0.95, G_c(z) be compensator, G_c(z)=K_r·z^kS (z), Wherein K_rTo repeat controller gain, value is 0.7, z^kFor lead compensation link, S (z) is low pass filter, and S (z)=S₁ (z)S₂(z), wherein S₁(z) be trapper, S₂Z () is second-order low-pass filter.