CN101950983A - Two-stage photovoltaic grid-connected control system based on combination of pole allocation and repetitive control - Google Patents

Abstract

The invention relates to a two-stage photovoltaic grid-connected control system based on the combination of pole allocation and repetitive control, which can invert the direct current output by a photovoltaic cell into alternating current well and transmit the alternating current to a power system, so that the harmonic wave content is low, the power supply quality is good, the utilization ratio of a system is high, the stability of the system can be improved to a certain extent and the properties of the whole photovoltaic system are improved. The two-stage photovoltaic grid-connected control system based on the combination of pole allocation and repetitive control has the advantages that: (1) due to the adoption of numerical control, the antijamming capacity is high and the system can achieve high precision and stability; (2) the system has clear assignment, obvious control effect, reliability and high robustness, wherein a preceding-stage Boost converter can realize maximum power tracking; and a last-stage inverter achieves direct current side voltage stabilization and grid-connected inversion; and (3) a control algorithm is advanced, wherein a dead zone effect of the inverter and the harmonic wave caused by partial non-linear loads are avoided by a repetitive control technique; and precise control is realized through the state feedback-based pole allocation.

Description

A kind of based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines

[technical field]

The present invention is used for solar grid-connected photovoltaic generation industry, belongs to power electronic technology and control theory interleaving techniques field, particularly a kind of based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines.

[background technology]

The energy is the material base of human survival and development, concerns national security and international status, gets most of the attention all the time.Now, along with the anxiety of fossil energy and the aggravation of environmental pollution, the utilization of renewable resource gets most of the attention, and solar energy is general, abundant with it, cleaning becomes the focus that people utilize.At present mainly utilize the photovoltaic generation of one of mode to obtain fast development as solar energy.

Photovoltaic generating system mainly is made of solar battery array and necessary Technics of Power Electronic Conversion equipment two parts.Independently generating electricity, not only cost is high but also unstable, and power supply reliability is low continuously, and being incorporated into the power networks is inexorable trend in the future.In grid-connected photovoltaic power generation system, tracking Control to electrical network is directly connected to the quality of output electric energy and the operational efficiency of system, be the core and the key problem in technology of system, the performance of control system is determining the success or failure of being incorporated into the power networks to a great extent, and a kind of rational control strategy just seems very necessary.The various control methods of using respectively have self-defect now, can not take into account response speed, control index, system design and stability.For example: PID control dynamic response is fast, but the output waveform distortion is serious; Though dead-beat control method is control in real time, current response is fast, and the output voltage electric current does not contain specific subharmonic, and the switching frequency of power device is unfixing, can cause the current spectrum broad, may cause indirect Harmonic Interference, causes the filter circuit difficult design.Sliding-Mode Control Based shows the insensitivity of system parameter variations and load disturbance and robustness and has good dynamic characteristic.But Sliding-Mode Control Based exists desirable sliding formwork diverter surface to be difficult to choose, control the weakness such as influence that effect is subjected to sample frequency, it also exists in high dither phenomenon and the design need know the boundary of systematic uncertainty parameter and disturbance, and shake such as can't accurately locate at system.In view of this, employing has inhibiting repetition control technology to design net-connected controller to periodic disturbance, on the one hand it can eliminate the wave distortion that the dead time effect by inverter self causes, it also has certain inhibitory action to the harmonic wave that nonlinear-load causes simultaneously.So designing combining inverter based on the repetition control technology has certain prospect.

[summary of the invention]

The object of the present invention is to provide a kind of based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, it makes above-mentioned said employing have inhibiting repetition control technology to design net-connected controller to periodic disturbance and becomes a reality, the direct current that it not only can send photovoltaic cell is converted to alternating current, and can control frequency, voltage, electric current, phase place, meritorious and idle etc., having determined to send into the quality of power supply of electrical network and concerned the system capacity conversion efficiency, is a kind of new technology that is used for solar grid-connected photovoltaic generation industry.

Technical scheme of the present invention:

1 one kinds based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, it is characterized in that this system comprises: photovoltaic array, boost converter, three-phase inverter, three-phase LCL filter and control circuit are formed, concrete annexation between them is: photovoltaic array output inserts the boost converter, after boosting, send into three-phase inverter, the output of inverter is connected to the LCL filter, and electric energy inserts electrical network after filtering; Wherein, control circuit comprises input, conditioning loop and DSP data processor etc., and type of attachment is shown in figure one.

At first gather inverter direct-flow side voltage, electric current during work, line voltage, phase place and grid-connected current obtain the reference-input signal of grid-connected current under the effect of outer shroud PI controller according to energy conservation principle; By instrument transformer acquisition system state variable, after overvoltage formation, filter circuit conditioning, send into AD converter successively then, send into dsp controller at last, export six road pwm signals through the control law effect.The final realization becomes alternating current to send into electrical network the dc inverter of photovoltaic cell output, finishes the control of being incorporated into the power networks of solar energy power generating.

This wherein a kind ofly is embodied in the control law based on POLE PLACEMENT USING and the control method that repeats control technology.Be listed as the state space equation of writing the LCL filter by Fig. 3, derive grid-connected current I ₂With inverter bridge output U _kBetween transfer function, as follows

${\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">I</figure-callout>}}_2=\frac{1}{L_1{L}_2{C}_2{s}^3+(L_1{R}_2{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">C</figure-callout>}}_2+L_2{R}_1{C}_2){\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+(R_1{R}_2{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">C</figure-callout>}}_2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)s+(R_1+R_2)}{U}_k+$

$\frac{L_1{C}_2{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+R_1{C}_{2}s+1}{L_1{L}_2{C}_2{s}^3+(L_1{R}_2{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">C</figure-callout>}}_2+L_2{R}_1{C}_2){\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+(R_1{R}_2{\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">C</figure-callout>}}_2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)s+(R_1+R_2)}{U}_s$

This is three rank linear systems of the single output of a dual input, chooses filter inductance L1, and the inductance L that is incorporated into the power networks 2 electric currents and filter capacitor voltage U c are state variable, and Us is as the input of system, wherein with the disturbance input variable of Us as system.Because R1, R2 are the dead resistance of filter inductance, very little, though this will make whole limits of open cycle system all at the left half-plane in S territory, but it is very near from the imaginary axis, cause the LCL filter very big easily at resonance frequency place resonance peak, as not taking the braking measure meeting to increase content of high order harmonic in the grid-connected current, have a strong impact on the quality of grid-connected current.For this reason, need reconfigure the limit of system.

(1) based on the POLE PLACEMENT USING of state feedback

Equipping rules based on the closed loop dominant pole is generally as follows;

${\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">s</figure-callout>}}_{\mathrm{1,2}}\left(s\right)=-{\mathrm{\&xi;}}_r{\mathrm{\&omega;}}_r\&PlusMinus;j{\mathrm{\&omega;}}_r\sqrt{1-{\mathrm{\&xi;}}^2}$

s _3，4(s)＝-mξ _rω _r

m＝4～10，0.6＜ξ＜0.8

3000≤ω _r6000

Because the dynamic behaviour of the characterization system that the state energy is complete is so adopt state feedback to come assigned pole here.Configuration principle is shown in figure four.

(2) repetitive controller design

The internal structure of repetitive controller as shown in Figure 5, r is a sinusoidal reference signal among the figure, y is an inverter output voltage, e is periodic disturbance for error signal d, Z ^-NBe the cycle delay link, N is the sampling number of a primitive period, and C (z) is for repeating the compensator of control loop, and P (z) is a controlling object.

Find out that by a last joint inverter of crossing through POLE PLACEMENT USING has not had resonance peak, therefore, need not to design again notch filter during the design repetitive controller.Only need design second order filter and suitable differentiation element to get final product.When designing the filter of repetitive controller, the amplitude-frequency characteristic of filter preferably just produces significantly near the cut-off frequency of inverter and descends.The cut-off frequency of filter S (z) is chosen as 7600rad/s, and the damping ratio of second order filter is greater than 0.707, and the transfer function that can get the second order filter under the s territory is

$c_1\left(s\right)=\frac{{\mathrm{\&omega;}}_n^2}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+2\mathrm{\&xi;}{\mathrm{\&omega;}}_n+{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}$

The system of drawing open loop Bode diagram is according to the phase settings compensation tache Z that lags behind ⁿ

(3) outer shroud PI design of Controller

With the interior ring equivalent-simplification of above two steps design, use the root locus method and determine the PI controller parameter, obtain the reference signal amplitude of grid-connected current.Gather electric network voltage phase and grid-connected current.With the multiply each other reference signal of controlled input of the sine wave of the voltage-phase that obtains and standard 50Hz, it and the grid-connected current that is regarded as disturbing signal insert repetitive controller as input together.

With the realization of in CCS, programming of top set control law, among the burned DSP, finish data computing and processing.

Advantage of the present invention and beneficial effect

The design adopts state feedback configuration-system limit to make system have better dynamic performance and lower steady-state error, and utilization repeats control technology and eliminates the high order harmonic component that produces in the inversion process again, integrates two kinds of control method advantages.Building the emulation check that system model carries out at the design shows, application based on POLE PLACEMENT USING with repeat to control the two-stage type grid-connected photovoltaic power generation system that combines and improve a lot aspect the output waveform, the grid-connected current harmonic content is little, and total percent harmonic distortion is less than 1%, and does not contain flip-flop.From the effect that is incorporated into the power networks, inverter power factor height, power quality indexes meets the engineering requirement of being incorporated into the power networks.So, more than reasonable in design feasible, big than the conventional apparatus advantage, certain application prospect is arranged.

[description of drawings]

Fig. 1 is related a kind of based on POLE PLACEMENT USING and the integrated circuit structural representation that repeats to control the two-stage type grid-connected photovoltaic power generation system that combines for the present invention.

Fig. 2 for the present invention related a kind of based on POLE PLACEMENT USING with repeat to control the complete control structure schematic diagram that is incorporated into the power networks of photovoltaic generating system that combines.

Fig. 3 is the related a kind of LCL three rank filter model equivalent schematic of the present invention.

Fig. 4 is related a kind of based on the closed-loop system figure that forms after the state feedback for the present invention.

Fig. 5 is the related a kind of repetitive controller internal structure schematic diagram of the present invention.

Fig. 6 is the related a kind of input circuit theory block diagram of the present invention.

Fig. 7 is the related a kind of signal conditioning circuit figure of the present invention.

Input circuit theory figure in Fig. 8 control system.

[embodiment]

Embodiment

Specify as follows below with reference to the accompanying drawings:

Two-stage type photovoltaic generating system with Fig. 1 form is an example, this system comprises: photovoltaic array, boost converter, three-phase inverter, three-phase LCL filter and control circuit are formed, concrete annexation between them is: photovoltaic array output inserts the boost converter, after boosting, send into three-phase inverter, the output of inverter is connected to the LCL filter, and electric energy inserts electrical network after filtering; Wherein, control circuit comprises input, conditioning loop and DSP data processor etc., and type of attachment is shown in figure one.

At first gather inverter direct-flow side voltage, electric current during work, line voltage, phase place and grid-connected current obtain the reference-input signal of grid-connected current under the effect of outer shroud PI controller according to energy conservation principle; By instrument transformer acquisition system state variable, after overvoltage formation, filter circuit conditioning, send into AD converter successively then, send into dsp controller at last, export six road pwm signals through the control law effect.The final realization becomes alternating current to send into electrical network the dc inverter of photovoltaic cell output, finishes the control of being incorporated into the power networks of solar energy power generating.

A kind of control method based on POLE PLACEMENT USING and repetition control technology is embodied in the control law, is specially:

(1) based on state feedback configuration-system limit

Draw transfer function according to Fig. 4 based on the state feedback assigned pole

${\mathrm{<figure-callout\; id="2"\; label="I"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">I</figure-callout>}}_2=\frac{u_v-c_1{L}_1{u}_s{s}^2-c_1{R}_1{u}_{s}s-k_3{c}_1{u}_{s}s-({\mathrm{<figure-callout\; id="2"\; label="k"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">k</figure-callout>}}_2+1)u_s}{L_1{L}_2{c}_1{s}^3+(L_1{c}_1{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+L_2{c}_1{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+k_3{c}_1{L}_2){\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+(k_3{c}_1{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+k_2{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">L</figure-callout>}}_2+R_1{c}_1{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1+L_2)s+k_2{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">R</figure-callout>}}_2+{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">k</figure-callout>}}_1+k_3+{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000291977300012.png,HSA00000291977300013.png"\; state="\{\{state\}\}">R</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">R</figure-callout>}}_2}$

Limit $\begin{array}{c}{s}_{\mathrm{1,2}}\left(s\right)=-{\mathrm{\&xi;}}_r{\mathrm{\&omega;}}_r\&PlusMinus;j{\mathrm{\&omega;}}_r\sqrt{1-{\mathrm{\&xi;}}^2}\\ s_3\left(s\right)=-m{\mathrm{\&xi;}}_r{\mathrm{\&omega;}}_r\end{array}$

Get m=5, ξ=0.6 ω _r=6000

(s-S ₁)(s-S ₂)(s-S ₃)

＝S ³+25200S ²+1.656×10 ⁸s+6.48×10 ⁹

Bring numerical value into, get k3=12.8056, k2=0.7332, k1=-8.60055.

(2) repetitive controller design

Find out that by a last joint inverter of crossing through POLE PLACEMENT USING has not had resonance peak, therefore, need not to design again notch filter during the design repetitive controller.Only need design second order filter and suitable differentiation element to get final product.When designing the filter of repetitive controller, the amplitude-frequency characteristic of filter preferably just produces significantly near the cut-off frequency of inverter and descends.The cut-off frequency of filter S (z) is chosen as 7600rad/s, and the damping ratio of second order filter is greater than 0.707, and the transfer function that can get the second order filter under the s territory is

$c_1\left(s\right)=\frac{{\mathrm{\&omega;}}_n^2}{{\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">s</figure-callout>}}^2+2\mathrm{\&xi;}{\mathrm{\&omega;}}_n+{\mathrm{\&omega;}}_{\mathrm{<figure-callout\; id="2"\; label="n"\; filenames="HSA00000291977300022.png,HSA00000291977300041.png"\; state="\{\{state\}\}">n</figure-callout>}}^2}$

The system of drawing open loop Bode diagram is according to the phase settings compensation tache Z that lags behind ⁹

(3) outer shroud PI design of Controller

With the interior ring equivalent-simplification of above two steps design, use the root locus method and determine the PI controller parameter, obtain the reference signal amplitude of grid-connected current.Gather electric network voltage phase and grid-connected current.With the multiply each other reference signal of controlled input of the sine wave of the voltage-phase that obtains and standard 50Hz, it and the grid-connected current that is regarded as disturbing signal insert repetitive controller as input together.

(4) top set control law is programmed in CCS realization is among the burned DSP.Simultaneously, set the switching frequency f of inverter _cSampling number N=200 in=10KHz and the unit period, wherein, U _01mFor inverter output fundamental voltage amplitude is 311V, U _dBe inverter direct-flow side voltage 690V.

$U_{01m}\&ap;\frac{1}{2}m\&times;U_d$

$N=\frac{f_c}{50}$

(5) the PWM generator is sent in the output of dsp controller, the latter will produce six road IGBT drive signals and finish switching manipulation to inverter, the final realization becomes alternating current to send into electrical network the dc inverter of photovoltaic cell output, finishes the control of being incorporated into the power networks of solar energy power generating.

More than six ones finished based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, here photovoltaic array maximum power voltage U mppt=516V, maximum power electric current I mppt=193.8 open circuit voltage Uoc=682V, short circuit current Il=221A, output rating P=100kW.Boost converter switches pipe is selected IGBT for use, inductance L=1.36mH, capacitor C=690uF.LCL filter L1=0.53mH, L2=0.33mH, C=39uF.R1＝0.03Ω，R2＝0.01Ω。The AD conversion chip is selected AD73360 for use, and phase-locked loop is selected CD4046 for use, and dsp chip is selected the TMS320VC5402 chip for use.Concrete connected mode as shown in drawings.DC converter is finished maximal power tracing and output voltage adjustment among the figure, makes that inverter direct-flow side voltage is 690V.

Find by emulation: the grid-connected current harmonic content is little, and total percent harmonic distortion is less than 1%, and does not contain flip-flop.From the effect that is incorporated into the power networks, inverter power factor 97.9%, power quality indexes meets the engineering requirement of being incorporated into the power networks.

Claims (4)

1. One kind based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, it is characterized in that this system comprises:

   Circuit topological structure: the native system main structure is made up of photovoltaic array, boost converter, three-phase inverter, three-phase LCL filter and control circuit, concrete annexation between them is: photovoltaic array output inserts the boost converter, after boosting, send into three-phase inverter, the output of inverter is connected to the LCL filter, and electric energy inserts electrical network after filtering;

   Input, modulate circuit: by voltage transformer, the voltage of current transformer detection system, electric current; Voltage transformer is used for measuring line voltage and LCL filter capacitance voltage, current transformer is used to measure inverter output current and grid-connected current, the voltage of gained, electric current are sent into voltage and are formed the loop after the secondary no-load voltage ratio, send into central processing unit DSP again after the filtering;

   Central processing unit DSP: the output of central processing unit DSP connects the IGBT control end; Detect the data of coming at central processing unit DSP intermediate range ordered pair and handle and calculate, carry out the expectant control algorithm.
2. According to claim 1 said a kind of based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, it is characterized in that control system adopts POLE PLACEMENT USING and repeats control technology and control combining inverter jointly; Control circuit is sent into AD converter successively by instrument transformer acquisition system state variable after overvoltage formation, filter circuit conditioning, send into dsp controller at last, exports six road pwm signals through the control law effect; This control law wherein just is being based on POLE PLACEMENT USING and the design of repetition control technology.
3. According to claim 1 said a kind of based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, it is characterized in that and will mix use with repetitive control based on the POLE PLACEMENT USING of state feedback, used state variable is by signal deteching circuit; Its control law-based on the POLE PLACEMENT USING of state feedback and repetitive control is the carrier control that realizes being incorporated into the power networks with the dsp controller.
4. According to claim 1 said a kind of based on POLE PLACEMENT USING with repeat to control the grid-connected control system of the two-stage type that combines, it is characterized in that being applicable to two-stage type grid-connected photovoltaic system, the adjustment of maximal power tracing and voltage is realized that by the boost converter this control system is primarily aimed at inverter and launches.

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