CN201813171U - A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control - Google Patents

Abstract

The utility model provides a two-stage photovoltaic grid-connected control device based on pole assignment and repetitive control combination. The device can invert direct current output by a photovoltaic cell into alternating current, and transmit the alternating current into the power grid to ensure less content of harmonic wave, high power supply quality and high system utilization efficiency, and the system stability can be improved to a certain extent, thereby improving the performance of the whole photovoltaic system. The two-stage photovoltaic grid-connected device has the advantages:(1) digital control is adopted, the interference resistance is strong, and the system can obtain excellent accuracy and stability; (2) the system has clear division, and the control effect is remarkable: a forward Boost converter realizes maximum power tracking, and a backward converter completes direct current side voltage stability and grid-connected inversion; and the system is reliable, and the robustness is good; and (3) the control algorithm is advanced: the dead-time effect of the converter and harmonic wave caused by nonpolar load can be overcome by using the repetitive control technology; and accurate control is realized by applying the pole assignment based on state feedback.

Description

A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control

【Technical field】

The utility model is used in the solar grid-connected photovoltaic power generation industry, belongs to the interdisciplinary technical field of power electronics technology and control theory, in particular a two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control.

【Background technique】

Energy is the material basis for human survival and development, which is related to national security and international status, and has always attracted attention. Today, with the shortage of fossil energy and the aggravation of environmental pollution, the utilization of renewable resources has attracted much attention, and solar energy has become the focus of people's utilization because of its universality, abundance and cleanliness. Photovoltaic power generation, one of the main utilization methods of solar energy, has developed rapidly.

Photovoltaic power generation system is mainly composed of two parts: solar cell array and necessary power electronic conversion equipment. Independent power generation is not only costly but also unstable, and the reliability of continuous power supply is low. Grid connection is an inevitable trend in the future. In the grid-connected photovoltaic power generation system, the tracking control of the grid is directly related to the quality of the output power and the operating efficiency of the system. It is the core and technical key of the system. The performance of the control system determines the success or failure of the grid connection to a large extent. A reasonable control strategy is very necessary. The various control methods currently used have their own defects, and cannot take into account the response speed, control index, system design and stability. For example: the dynamic response of PID control is fast, but the output waveform distortion is serious; although the deadbeat control method is real-time control, the current response is fast, and the output voltage and current do not contain specific sub-harmonics, but the switching frequency of the power device is not fixed, which will cause current The wide frequency spectrum may cause indirect harmonic interference, making it difficult to design filter circuits. Sliding mode control exhibits insensitivity and robustness to system parameter changes and load disturbances and has good dynamic characteristics. However, the sliding mode control has the disadvantages that the ideal sliding mode switching surface is difficult to select, and the control effect is affected by the sampling frequency. It also has high-frequency jitter phenomenon, and the design needs to know the system uncertainty parameters and the limit of disturbance. The jitter makes the system unable to be accurate. positioning etc. In view of this, the grid-connected controller is designed with the repetitive control technology that can inhibit the periodic disturbance. On the one hand, it can eliminate the waveform distortion caused by the dead zone effect of the inverter itself, and at the same time it can eliminate the waveform distortion caused by the nonlinear load. Harmonics also have a certain inhibitory effect. Therefore, the design of grid-connected inverters based on repetitive control technology has certain prospects.

【Content of utility model】

The purpose of this utility model is to provide a two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control, which enables the above-mentioned repetitive control technology that can inhibit periodic disturbances to design grid-connected control It can not only convert the direct current generated by photovoltaic cells into alternating current, but also control the frequency, voltage, current, phase, active and reactive power, etc., which determines the quality of power sent to the grid and is related to system energy conversion. Efficiency, is a new technology for solar grid-connected photovoltaic power generation industry.

Technical scheme of the utility model:

1 A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control, characterized in that the device includes: a photovoltaic array, a boost converter, a three-phase inverter, a three-phase LCL filter and a control circuit , the specific connection relationship between them is: the output of the photovoltaic array is connected to the boost converter, and then sent to the three-phase inverter after boosting, the output of the inverter is connected to the LCL filter, and the electric energy is connected to the grid after filtering; , the control circuit includes signal detection, conditioning loop and DSP data processor, etc., the connection form is shown in Figure 1.

When working, first collect the DC side voltage and current of the inverter, the grid voltage, phase and grid-connected current, and obtain the reference input signal of the grid-connected current under the action of the outer loop PI controller according to the principle of energy conservation; collect the system status through the transformer The variable is then sent to the AD converter after voltage formation and filter circuit conditioning, and finally sent to the DSP controller, which outputs six PWM signals through the control law. Finally, the direct current output by the photovoltaic cell is converted into alternating current and sent to the grid, and the grid-connected control of solar photovoltaic power generation is completed.

Among them, a control method based on pole placement and repetitive control techniques is embodied in the control law. Write the state space equation of the LCL filter from Figure 3, and derive the transfer function between the grid-connected current I ₂ and the output U _k of the inverter bridge, as shown below

${\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="I"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">I</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; k</span>}}<span\; class="notranslate">\; +</span>$

$\frac{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="C"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">C</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}$

This is a three-order linear system with double input and single output. Filter inductor L1, grid-connected inductor L2 current and filter capacitor voltage Uc are selected as state variables, Us is used as the input of the system, and Us is used as a disturbance input of the system. Since R1 and R2 are the parasitic resistance of the filter inductor, which is very small, this will make all the poles of the open-loop system in the left half plane of the S domain, but they are very close to the imaginary axis, which will easily cause the LCL filter to be at the resonance frequency. The resonance peak value is very large, if no suppression measures are taken, the content of higher harmonics in the grid-connected current will be increased, which will seriously affect the quality of the grid-connected current. To do this, the poles of the system need to be reconfigured.

(1) Pole configuration based on state feedback

The configuration principle based on the closed-loop dominant pole is generally as follows;

${\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="1"\; label="s"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">s</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1,2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; \&PlusMinus;</span>{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

s _3,4 (s)=-mξ _r ω _r

m=4～10, 0.6<ξ<0.8

_{3000≤ωr6000}

Since the state can completely characterize the dynamic behavior of the system, the state feedback is used to configure the poles here. The configuration principle is shown in Figure 4.

(2) Repeat controller design

The internal structure of the repeating controller is shown in Figure 5, where r is the sinusoidal reference signal, y is the inverter output voltage, e is the error signal and d is the periodic disturbance, Z ^-N is the periodic delay link, and N is a The sampling times of the fundamental cycle, C(z) is the compensator of the repeated control loop, and P(z) is the control object.

It can be seen from the previous section that the inverter with the pole configuration has no resonance peak, so there is no need to design a wave-limiting filter when designing a repetitive controller. It is only necessary to design a second-order filter and an appropriate leading link. When designing a filter for a repetitive controller, the amplitude-frequency characteristics of the filter should preferably not drop significantly until near the cut-off frequency of the inverter. The cut-off frequency of the filter S(z) is selected as 7600rad/s, and the damping ratio of the second-order filter is greater than 0.707. The transfer function of the second-order filter in the s domain can be obtained as

${\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="no"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">no</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="no"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">no</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Draw the open-loop Bode diagram of the system, and set the compensation link Z ⁿ according to the lagging phase

(3) Outer loop PI controller design

The inner loop of the above two-step design is equivalently simplified, the root locus method is used to determine the PI controller parameters, and the reference signal amplitude of the grid-connected current is obtained. Collect grid voltage phase and grid-connected current. Multiply the obtained voltage phase with the standard 50Hz sine wave to get the reference signal of the control input, which is connected to the repetitive controller together with the grid-connected current regarded as the disturbance signal as the input.

Program the control law set above in CCS, burn it into DSP, and complete the calculation and processing of data.

Advantages and beneficial effects of the utility model

This design uses state feedback to configure the poles of the system to make the system have better dynamic performance and lower steady-state error, and then uses repetitive control technology to eliminate high-order harmonics generated during the inverter process, integrating the advantages of the two control methods. The simulation test of the system model built for this design shows that the application of the two-stage grid-connected photovoltaic power generation system based on the combination of pole configuration and repetitive control has greatly improved the output waveform, the harmonic content of the grid-connected current is small, and the total harmonic Wave distortion rate is less than 1%, and does not contain DC components. From the perspective of grid connection effect, the power factor of the inverter is high, and the indicators of power quality meet the engineering technical requirements of grid connection. Therefore, the above design is reasonable and feasible, has greater advantages than traditional devices, and has certain application prospects.

【Description of drawings】

Fig. 1 is a schematic diagram of the overall circuit structure of a two-stage grid-connected photovoltaic power generation system based on the combination of pole configuration and repetitive control according to the present invention.

Fig. 2 is a schematic diagram of a complete grid-connected control structure of a photovoltaic power generation system based on a combination of pole configuration and repetitive control according to the present invention.

Fig. 3 is an equivalent schematic diagram of an LCL third-order filter model involved in the present invention.

Fig. 4 is a diagram of a closed-loop system based on state feedback according to the present invention.

Fig. 5 is a schematic diagram of the internal structure of a repetitive controller involved in the present invention.

Fig. 6 is a schematic block diagram of a signal detection circuit involved in the present invention.

Fig. 7 is a signal conditioning circuit diagram involved in the present invention.

Figure 8 is a schematic diagram of the signal detection circuit in the control device.

【Detailed ways】

Example

The specific description is as follows according to the accompanying drawings:

Taking the two-stage photovoltaic power generation system in the form of Figure 1 as an example, the device includes: photovoltaic array, boost converter, three-phase inverter, three-phase LCL filter and control circuit. The specific connection relationship between them is: photovoltaic The output of the array is connected to the boost converter, which is boosted and sent to the three-phase inverter. The output of the inverter is connected to the LCL filter, and the electric energy is connected to the power grid after filtering. Among them, the control circuit includes signal detection, conditioning loop and DSP data processor, etc., the connection form is shown in Figure 1.

When working, first collect the DC side voltage and current of the inverter, the grid voltage, phase and grid-connected current, and obtain the reference input signal of the grid-connected current under the action of the outer loop PI controller according to the principle of energy conservation; collect the system status through the transformer The variable is then sent to the AD converter after voltage formation and filter circuit conditioning, and finally sent to the DSP controller, which outputs six PWM signals through the control law. Finally, the direct current output by the photovoltaic cell is converted into alternating current and sent to the grid, and the grid-connected control of solar photovoltaic power generation is completed.

A control method based on pole placement and repetitive control techniques is embodied in the control law, specifically:

(1) Configure system poles based on state feedback

According to Figure 4, the transfer function based on the state feedback configuration pole is obtained

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; v</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="k"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="c"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">c</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; the\; s</span>}}^{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="L"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="L"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">L</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; L</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="k"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">k</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="R"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="R"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">R</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

${\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="1"\; label="s"\; filenames="HSA00000291979600012.png,HSA00000291979600013.png"\; state="\{\{state\}\}">s</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 1,2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}<span\; class="notranslate">\; \&PlusMinus;</span>{\mathrm{<span\; class="notranslate">\; j\&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; r</span>}}\sqrt{\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&xi;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

pole

s ₃ (s)=-mξ _r ω _r

Take m=5, ξ=0.6ω _r =6000

(sS ₁ )(sS ₂ )(sS ₃ )

＝S ³ +25200S ² +1.656×10 ⁸ s+6.48×10 ⁹

Putting in the values, we get k3=12.8056, k2=0.7332, k1=-8.60055.

(2) Repeat controller design

It can be seen from the previous section that the inverter with the pole configuration has no resonance peak, so there is no need to design a wave-limiting filter when designing a repetitive controller. It is only necessary to design a second-order filter and an appropriate leading link. When designing a filter for a repetitive controller, the amplitude-frequency characteristics of the filter should preferably not drop significantly until near the cut-off frequency of the inverter. The cut-off frequency of the filter S(z) is selected as 7600rad/s, and the damping ratio of the second-order filter is greater than 0.707. The transfer function of the second-order filter in the s domain can be obtained as

${\mathrm{<span\; class="notranslate">\; c</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; the\; s</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; the\; <figure-callout\; id="2"\; label="s"\; filenames="HSA00000291979600013.png,HSA00000291979600041.png"\; state="\{\{state\}\}">s</figure-callout></span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&xi;</span>}{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

Draw the open-loop Bode diagram of the system, and set the compensation link Z according to the lagged phase ⁹

(3) Outer loop PI controller design

The inner loop of the above two-step design is equivalently simplified, the root locus method is used to determine the PI controller parameters, and the reference signal amplitude of the grid-connected current is obtained. Collect grid voltage phase and grid-connected current. The obtained voltage phase is multiplied by the standard 50Hz sine wave to obtain the reference signal of the control input, which is connected to the repetitive controller together with the grid-connected current regarded as the disturbance signal as the input.

(4) Program the control law set above in CCS and burn it into DSP. At the same time, set the switching frequency of the inverter _fc = 10KHz and the number of sampling in a unit cycle N = 200, where U _01m is the amplitude of the fundamental wave voltage output by the inverter and U _d is the DC side voltage of the inverter 690V.

${\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 01</span>}\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; \&ap;</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}$

$\mathrm{<span\; class="notranslate">\; N</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="50"\; label="f\; c"\; filenames="HSA00000291979600041.png"\; state="\{\{state\}\}">f</figure-callout></span><figure-callout\; id="50"\; label="f\; c"\; filenames="HSA00000291979600041.png"\; state="\{\{state\}\}">\; </figure-callout>}}_{\mathrm{<span\; class="notranslate">\; </span>}}}{\mathrm{<span\; class="notranslate">\; 50</span>}}$

(5) Send the output of the DSP controller to the PWM generator, which will generate six IGBT drive signals to complete the switching operation of the inverter, and finally realize the conversion of the direct current output by the photovoltaic cell into alternating current and send it to the grid to complete the solar energy. Grid-connected control of photovoltaic power generation.

The above six parts have completed the two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control. Here, the maximum power voltage of the photovoltaic array Umppt=516V, the maximum power current Imppt=193.8, the open circuit voltage Uoc=682V, and the short-circuit current I1=221A, Output rate P=100kW. The switch tube of the Boost converter uses IGBT, the inductance L=1.36mH, and the capacitance C=690uF. LCL filter L1=0.53mH, L2=0.33mH, C=39uF. R1=0.03Ω, R2=0.01Ω. The AD conversion chip is AD73360, the phase-locked loop is CD4046, and the DSP chip is TMS320VC5402. The specific connection method is shown in the accompanying drawing. In the figure, the DC converter completes the maximum power tracking and output voltage adjustment, so that the DC side voltage of the inverter is 690V.

Through simulation, it is found that the harmonic content of grid-connected current is small, the total harmonic distortion rate is less than 1%, and it does not contain DC components. From the perspective of grid connection effect, the power factor of the inverter is 97.9%, and all indicators of power quality meet the engineering technical requirements of grid connection.

Claims (4)

1. A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control, characterized in that the device includes: Circuit topology: the main structure of this device is composed of photovoltaic array, boost converter, three-phase inverter, three-phase LCL filter and control circuit. After boosting, it is sent to the three-phase inverter, and the output of the inverter is connected to the LCL filter, and the electric energy is connected to the grid after filtering; Signal detection and conditioning circuit: detect the voltage and current of the system through voltage transformers and current transformers; voltage transformers are used to measure grid voltage and capacitor voltage in LCL filters, and current transformers are used to measure inverter output current and grid-connected current , the obtained voltage and current are sent to the voltage to form a loop after the secondary transformation ratio, and then sent to the central processing unit DSP after filtering; the conditioning circuit Central processing unit DSP: The output terminal of the central processing unit DSP is connected to the IGBT control terminal; the program in the central processing unit DSP processes and calculates the detected data and executes a predetermined control algorithm. 2. A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control according to claim 1, characterized in that the control device uses pole configuration and repetitive control technology to control the grid-connected inverter; The control circuit collects the state variables of the system through the transformer, and sends them to the AD converter after voltage formation and filter circuit conditioning, and finally to the DSP controller, and outputs six PWM signals through the control law; the control law is based on the pole Configuration and design of repetitive control technology. 3. A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control according to claim 1, characterized in that the pole configuration based on state feedback and the repetitive control method are used in combination, and the state variables used It is derived from the signal detection circuit; its control law - the pole configuration and repetitive control method based on state feedback uses the DSP controller as the carrier to realize grid-connected control. 4. A two-stage photovoltaic grid-connected control device based on the combination of pole configuration and repetitive control according to claim 1, which is characterized in that it is suitable for two-stage grid-connected photovoltaic systems, and the maximum power tracking and voltage adjustment are controlled by The boost converter is implemented, and the control device is mainly developed for the inverter.

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