CN110957763A - Two-stage type photovoltaic grid-connected power generation system and control method thereof - Google Patents

Two-stage type photovoltaic grid-connected power generation system and control method thereof Download PDF

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CN110957763A
CN110957763A CN201911404557.0A CN201911404557A CN110957763A CN 110957763 A CN110957763 A CN 110957763A CN 201911404557 A CN201911404557 A CN 201911404557A CN 110957763 A CN110957763 A CN 110957763A
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circuit
voltage
grid
reference signal
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陈文献
王交通
张仪
杨洋
段鑫
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Ankang Power Supply Co Of State Grid Shaanxi Electric Power Co
State Grid Corp of China SGCC
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Ankang Power Supply Co Of State Grid Shaanxi Electric Power Co
State Grid Corp of China SGCC
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/56—Power conversion systems, e.g. maximum power point trackers

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Abstract

The invention discloses a two-stage photovoltaic grid-connected power generation system and a control method thereof, wherein the system comprises a photovoltaic component, a DC/DC circuit, a DC/AC circuit, an alternating current power grid, a DC/AC drive circuit and a DC/AC drive circuit; the photovoltaic component passes through a capacitor C1Is electrically connected with a DC/DC circuit which is electrically connected with the DC/DC circuit through a capacitor C2The DC/AC circuit is electrically connected with the power grid through the inductive filter; the DC/AC driving circuit drives the DC/DC circuit to boost the photovoltaic output voltage; the DC/AC driving circuit drives a DC/AC circuit; the DC/AC circuit is connected to the grid via an inductive filter. The invention uses a capacitor C2The dynamic process of (2) provides certain inertia support for the system under the condition of small interference, namely no energy storage equipment is additionally arranged, the system also has the capability of stable operation, and the utilization rate of system energy is favorably improved.

Description

Two-stage type photovoltaic grid-connected power generation system and control method thereof
Technical Field
The invention belongs to the technical field of new energy power generation, and particularly relates to a two-stage type photovoltaic grid-connected power generation system and a control method thereof.
Background
With the increasing global energy crisis and the environmental pollution problem, the vigorous development of clean energy has become a development consensus of countries in the world. The distributed photovoltaic power generation technology is a representative of a novel renewable energy power generation technology, and shows explosive growth by virtue of the advantages of abundant resources, no pollution and the like.
In a two-stage photovoltaic grid-connected power generation system, the physical characteristics of a grid-connected inverter are obviously different from those of a rotary synchronous generator. The grid-connected inverter as power electronic equipment does not have physical inertia, and is connected to a power grid in a large scale by the characteristics of low inertia and weak damping, so that the inertia in the system is reduced, and a serious challenge is brought to the safe and stable operation of the power grid. Meanwhile, the photovoltaic power generation has large fluctuation, strong randomness and obvious intermittence, and the adverse effect is brought to the stable operation of the power grid.
In order to solve the problem of low inertia of the photovoltaic system, some researchers have proposed control strategies such as Virtual inertia control and Virtual Synchronous Generator (VSG) control. The core idea of the VSG is to use the equations of motion of the RSG for dynamic behavior simulation. Since the VSG control strategy is implemented on a grid-connected inverter, the VSG control cannot ensure the stability of the dc-side capacitor voltage, and therefore is only applicable to a grid-connected inverter of a voltage source type dc power supply. In addition, the VSG needs to be provided with a certain amount of reserve, the economy is poor, and the huge potential of the primary energy source and the converter thereof in the aspect of inertia/damping characteristic simulation is not fully utilized. The virtual inertia control is usually performed on the primary energy supply side, and the grid-connected inverter still adopts the conventional double closed-loop control to ensure the stability of the direct-current side capacitor voltage.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a two-stage photovoltaic grid-connected power generation system and a control method thereof, and the control method is based on a double closed loop control strategy of a conventional capacitor voltage outer loop and a conventional capacitor voltage inner loop, and only by introducing frequency deviation to form direct current voltage droop, a certain inertia support can be provided when a power grid generates small disturbance, so that the stability of the power grid is improved.
In order to test the technical purpose, the invention adopts the following technical scheme:
a two-stage type photovoltaic grid-connected power generation system comprises a photovoltaic component, a DC/DC circuit, a DC/AC circuit, an alternating current power grid, a DC/AC drive circuit and a DC/AC drive circuit;
the photovoltaic component passes through a capacitor C1Is electrically connected with a DC/DC circuit which is electrically connected with the DC/DC circuit through a capacitor C2The DC/AC circuit is electrically connected with the power grid through the inductive filter;
the DC/AC driving circuit is controlled by adopting a voltage outer ring and a current inner ring double closed loop, is adjusted by a PI (proportional integral) regulator, generates a pulse signal for controlling the on-off of a switching device, and drives the DC/DC circuit to improve the photovoltaic output voltage;
the DC/AC driving circuit adopts double closed-loop control of a direct-current voltage outer loop and a current inner loop, is regulated by a PI regulator, and generates PWM waves after dq-abc coordinate transformation to drive the DC/AC circuit;
the DC/AC circuit is connected to the grid via an inductive filter.
The DC/DC circuit is a Boost converter.
The DC/AC driving circuit is characterized in that a voltage corresponding to the maximum power is obtained by photovoltaic output voltage and current through an MPPT algorithm and is used as a reference signal for outer ring voltage control, the voltage reference signal is compared with an actual voltage and is regulated by a voltage regulator to generate an inner ring current reference signal, then the inner ring current reference signal is compared with the actual current, and a pulse signal for controlling the on-off of a switching device is generated through a current controller to drive the DC/DC circuit.
The DC/AC circuit is a grid-tied inverter.
The DC/AC drive circuit is specifically designed to give a DC voltage reference value Udc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdComparing, and adjusting through a current regulator; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
A control method based on the two-stage photovoltaic grid-connected power generation system comprises the following steps:
1) voltage U output by photovoltaic module is collected in real timepvCurrent Ipv；
2) The photovoltaic module is output at the maximum power, a voltage outer ring and a current inner ring are adopted for controlling, a PI regulator is used for regulating, a pulse signal for controlling the on-off of a switch device is generated, and a DC/DC circuit is driven to improve the photovoltaic output voltage so as to meet the requirement of grid-connected inversion;
3) the DC/DC circuit passing through a capacitor C2Is electrically connected with the DC/AC circuit;
4) double closed-loop control of a direct-current voltage outer ring and a current inner ring is adopted, the regulation is carried out through a PI regulator, and then the dq-abc coordinate transformation is carried out to generate PWM waves to drive a DC/AC circuit;
5) the DC/AC circuit is connected to the AC power grid via an inductive filter.
Preferably, the specific method for driving the DC/DC circuit is:
the photovoltaic output voltage and current are subjected to MPPT algorithm to obtain voltage corresponding to the maximum power as a reference signal for outer ring voltage control, the voltage reference signal is compared with actual voltage and is regulated by a voltage regulator to generate an inner ring current reference signal, then the inner ring current reference signal is compared with the actual current, and a pulse signal for controlling the on-off of a switching device is generated by a current controller to drive a DC/DC circuit.
Preferably, the specific method of driving the DC/AC circuit is:
given DC voltage reference value Udc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdComparing, and adjusting through a current regulator; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
Preferably, the active current component IdAnd a reactive current IqThe acquisition steps are as follows:
1) system voltage and current detection module real-time acquisition system three-phase voltage UabcThree-phase current Iabc；
2) The detection module detects a three-phase voltage phase theta of a power grid and the real-time frequency of the power grid by using a single synchronous coordinate system software phase-locked loop, and the phase angle theta is used for all coordinate conversion;
3) three-phase current IabcConverting the current component I into a current component I under a dq coordinate system through an abc-dq coordinate conversion moduledAnd Iq。
Preferably, the DC voltage reference value Udc_refBy Udc0And Udc *The frequency deviation is introduced to form f-U when the power grid frequency has disturbancedcCorrecting DC voltage reference value U in compensation linkdc_ref。
The invention has the following advantages and beneficial effects:
the invention discloses a two-stage photovoltaic grid-connected power generation system which mainly comprises a photovoltaic component, a direct current converter (a boost chopper), a capacitor, a DC/AC circuit, a line, a load and an alternating current grid. Photovoltaic module passing capacitor C1Is electrically connected with a DC converter which is connected with the DC converter through a capacitor C2The DC/AC circuit is electrically connected with the DC/AC circuit, and the DC/AC circuit is electrically connected with the power grid through the inductive filter. The photovoltaic module outputs according to the maximum power; the DC/DC circuit is controlled by a voltage outer loop current inner loop double closed loop; the DC/AC introduces frequency deviation on the basis of the outer loop current inner loop of the conventional direct current voltage to form direct current voltage droop control. The invention uses a capacitor C2The dynamic process of (2) provides certain inertia support for the system under the condition of small interference, namely, no energy storage equipment is additionally arranged, and the system also has stable operationThe line capability is beneficial to improving the utilization rate of system energy.
The control method realizes that the direct-current voltage at the direct-current side of the inverter and the frequency of a rear-stage power grid generate a coupling relation by introducing a frequency deviation; by utilizing the dynamic process of the capacitor, the voltage can fluctuate within a certain range under the action of small interference, and certain inertia support is provided for the system by reducing the voltage and releasing energy, so that the stability of the system is improved; compared with the method of providing extra inertia for the system by the energy storage, the method is improved only from the aspect of control, simple in thought, few in utilized components and good in economical efficiency.
Drawings
Fig. 1 is a structural diagram of a two-stage photovoltaic grid-connected power generation system;
FIG. 2 is a control strategy diagram of the DC/DC converter;
FIG. 3 is a block diagram of voltage phase detection;
FIG. 4 is a block diagram of three-phase AC to two-phase DC;
FIG. 5 is a DC/AC converter control strategy diagram;
FIG. 6 is a diagram of a two-stage photovoltaic grid-connected power generation system based on DC voltage droop control;
FIG. 7 is a simplified single-phase circuit diagram of the inverter;
and fig. 8 is a grid-connected inverter vector diagram under the dq coordinate system.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a two-stage photovoltaic grid-connected power generation system, which comprises a photovoltaic component, a DC/DC circuit, a capacitor, a DC/AC circuit, a line, a load, an alternating current power grid, a DC/AC drive circuit and a DC/AC drive circuit, wherein the DC/DC circuit is connected with the capacitor;
the photovoltaic component passes through a capacitor C1Is electrically connected with a DC/DC circuit which is electrically connected with the DC/DC circuit through a capacitor C2The DC/AC circuit is electrically connected with the power grid through the inductive filter;
the DC/AC driving circuit is controlled by adopting a voltage outer ring and a current inner ring double closed loop, is adjusted by a PI (proportional integral) regulator, generates a pulse signal for controlling the on-off of a switching device, and drives the DC/DC circuit to improve the photovoltaic output voltage;
the DC/AC driving circuit adopts double closed-loop control of a direct-current voltage outer loop and a current inner loop, is regulated by a PI regulator, and generates PWM waves after dq-abc coordinate transformation to drive the DC/AC circuit;
the DC/AC circuit is connected to the grid via an inductive filter.
The DC/DC circuit is a Boost converter, and the DC/AC circuit is a grid-connected inverter.
The DC/AC driving circuit is characterized in that a voltage corresponding to the maximum power is obtained by photovoltaic output voltage and current through an MPPT algorithm and is used as a reference signal for outer ring voltage control, the voltage reference signal is compared with an actual voltage and is regulated by a voltage regulator to generate an inner ring current reference signal, then the inner ring current reference signal is compared with the actual current, and a pulse signal for controlling the on-off of a switching device is generated through a current controller to drive the DC/DC circuit.
The DC/AC drive circuit is specifically designed to give a DC voltage reference value Udc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdComparing, and adjusting through a current regulator; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
The working principle of the two-stage photovoltaic grid-connected power generation system is as follows:
(1) under the condition that the illumination intensity and the temperature are not changed, the photovoltaic module outputs stable voltage UpvCurrent Ipv；
(2) The photovoltaic is output at the maximum power, a direct-current voltage outer ring and a current inner ring are adopted for controlling, and a PI regulator is used for regulating to generate a pulse signal for controlling the on-off of a switching device so as to drive a DC/DC circuit;
(3) the DC/DC circuit is a Boost converter and is used for boosting the output voltage of the photovoltaic and ensuring that the direct-current voltage meets the requirement of grid connection;
(4) real-time acquisition system network side three-phase voltage UabcThree-phase current IabcDetecting a three-phase voltage phase angle theta by using a traditional SSRF-PLL (steady state RF-phase locked loop) for abc-dq coordinate conversion, and converting a three-phase current IabcConverting the current into active current I under dq coordinate systemdAnd a reactive current Iq；
(5) Utilizing the active current I of the step (4)dAnd a reactive current IqThe inverter adopts double closed-loop control of a direct-current voltage outer ring and a current inner ring, is regulated by a PI regulator, and generates PWM waves after dq-abc coordinate transformation to drive a DC/AC circuit;
(6) reasonable utilization of capacitor C2Providing inertia for the system;
(7) the DC/AC circuit is a grid-connected inverter that can output AC power synchronized with the frequency and phase of the grid, in addition to converting DC power to AC power.
The invention also provides a two-stage type photovoltaic grid-connected power generation system control method, which comprises the following steps:
1) voltage and current detection module collects voltage U output by photovoltaic module in real timepvCurrent Ipv；
2) The photovoltaic module outputs with the maximum power, and the DC/DC circuit is utilized to increase the photovoltaic output voltage so as to meet the requirement of grid-connected inversion;
3) a voltage outer ring and a current inner ring are adopted to control and drive a DC/DC circuit;
4) the DC/DC circuit passing through a capacitor C2Is electrically connected with the DC/AC circuit;
5) a DC/AC circuit is driven by adopting double closed loop control of a direct-current voltage outer loop and a current inner loop;
6) the DC/AC circuit is connected to the grid via an inductive filter.
Preferably, in the step 2), the photovoltaic maximum power algorithm includes a disturbance observation method, an increment conductance method and a current scanning method, any algorithm is selected in the invention, and the DC/DC circuit is a Boost converter.
Preferably, in step 3), the specific control strategy of the DC/DC circuit is that the photovoltaic output voltage and current obtain a voltage corresponding to the maximum power through an MPPT algorithm, the voltage is used as a reference signal for outer loop voltage control, the voltage reference signal is compared with an actual voltage, and is adjusted by a voltage regulator to generate an inner loop current reference signal, and then the inner loop current reference signal is compared with an actual current, and a pulse signal for controlling the on-off of the switching device is generated by a current controller to drive the DC/DC circuit.
Preferably, in step 5), a DC voltage reference value U is givendc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdComparing, and adjusting through a current regulator; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
The above-mentioned active current component IdAnd a reactive current IqThe acquisition steps are as follows:
1) system voltage and current detection module real-time acquisition system three-phase voltage UabcThree-phase current Iabc；
2) The detection module detects a three-Phase voltage Phase theta and a real-time frequency of a power grid by using a traditional Single synchronous coordinate system Software Phase-Locked Loop (SSRF-PLL), wherein the Phase angle theta is used for all coordinate conversion;
3) three-phase current IabcConverting the current component I into a current component I under a dq coordinate system through an abc-dq coordinate conversion moduledAnd Iq。
The above-mentioned DC voltage reference value Udc_refBy Udc0And Udc *The frequency deviation is introduced to form f-U when the power grid frequency has disturbancedcCorrecting DC voltage reference value U in compensation linkdc_ref。
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Examples
The invention discloses a control scheme for improving the stability of a two-stage photovoltaic grid-connected power generation system under the action of small interference. The basic principle of this will be explained first.
The structure of a two-stage photovoltaic grid-connected power generation system is shown in fig. 1, and the system mainly comprises photovoltaic components, a DC/DC circuit, a grid-connected inverter and other links.
Because the output voltage of the photovoltaic module can not meet the requirement of voltage required by grid connection, a DC/DC circuit is required to improve the output voltage of the photovoltaic module, and the output voltage is merged into a power grid through a grid-connected inverter. When the frequency of a power grid fluctuates, the photovoltaic grid-connected inverter needs to provide reasonable inertia support for the system, so that the system can be quickly restored to a balanced state. In fact, in the application context of photovoltaic access to a strong power grid, the maximum power output by photovoltaic is far less than the requirement of the power grid, so the photovoltaic is always output at the maximum power, and the DC/DC side adopts maximum power tracking control. The control block diagram of the DC/DC circuit is shown in fig. 2.
As shown in fig. 2, the DC/DC control circuit adopts voltage outer loop and current inner loop dual closed loop control, and the dynamic process of the current inner loop can be ignored under the time scale of the DC voltage, so the output current of the photovoltaic module can be expressed as:
Figure BDA0002348282720000091
the photovoltaic module is output with the maximum power, and under the condition that the specific illumination intensity and the temperature are not changed, the output power of the photovoltaic module and the DC/DC converter is not changed, so that the following can be obtained:
ΔPin＝0 (2)
the rear-stage grid-connected inverter adopts double closed-loop control of a direct-current voltage outer loop and a current inner loop to realize the stability of capacitance and voltage, but when small disturbance occurs, because the DC/DC side is output according to the maximum power and is in a decoupling relation with the grid-connected inverter and cannot respond to the change of the frequency of a power grid, frequency deviation is introduced on the basis of the double closed loops to form direct-current voltage droop control. The control block diagram of the DC/AC circuit is shown in fig. 5.
Neglecting the dynamic process of the current inner loop on the time scale of the dc voltage, the control process shown in fig. 3 can be described as:
Figure BDA0002348282720000092
the deviation amount of the dc voltage can be described as:
Figure BDA0002348282720000093
in summary, a structural block diagram of the two-stage photovoltaic grid-connected power generation system with dc voltage droop control according to the present invention is shown in fig. 6, and the specific improvement steps are as follows:
1) the photovoltaic is output at the maximum power, and the algorithm of the maximum power of the photovoltaic comprises a disturbance observation method, an increment conductance method and a current scanning method, wherein any algorithm can be selected in the invention.
2) The DC/DC circuit is a Boost converter and is used for boosting the output voltage of photovoltaic and ensuring that the direct-current voltage meets the requirement of grid connection, the voltage corresponding to the maximum power is obtained by the photovoltaic output voltage current through an MPPT algorithm and is used as a reference signal for outer ring voltage control, the voltage reference signal is compared with the actual voltage and is regulated by a voltage regulator to generate an inner ring current reference signal, then the inner ring current reference signal is compared with the actual current, and a pulse signal for controlling the on-off of a switching device is generated by a current controller to drive the DC/DC circuit.
3) Network side of real-time acquisition systemThree-phase voltage UabcThree-phase current IabcThe three-phase voltage phase angle θ is detected using a conventional SSRF-PLL, as shown in fig. 3, for abc-dq coordinate conversion. For example, fig. 4 shows three-phase current IabcConverting the current into active current I under dq coordinate systemdAnd a reactive current Iq。
4) Given DC voltage reference value Udc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdComparing, and adjusting through a current regulator; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
5) Using a capacitor C2The voltage can fluctuate within a certain range under the action of small interference, certain inertia support is provided for the system through voltage reduction and energy release, and the stability of the system is improved. On the basis of a double closed-loop control strategy of a conventional capacitor voltage outer loop and a conventional capacitor voltage inner loop, direct-current voltage droop is formed by artificially coupling direct-current voltage and power grid frequency only by introducing frequency deviation.
The above is a detailed description of the present invention with reference to specific preferred embodiments, and it should not be considered that the present invention is limited to the specific embodiments, but that the present invention can be easily derived or substituted by those skilled in the art without departing from the spirit of the present invention, and all of them should be considered as falling within the scope of the patent protection defined by the claims of the present invention.

Claims (10)

1. A two-stage type photovoltaic grid-connected power generation system is characterized by comprising a photovoltaic component, a DC/DC circuit, a DC/AC circuit, an alternating current power grid, a DC/AC drive circuit and a DC/AC drive circuit;
the photovoltaic component passes through a capacitor C1Is electrically connected with a DC/DC circuit which is electrically connected with the DC/DC circuit through a capacitor C2Is electrically connected with the DC/AC circuitThe DC/AC circuit is electrically connected with a power grid through an inductive filter;
the DC/AC driving circuit is controlled by adopting a voltage outer ring and a current inner ring double closed loop, is adjusted by a PI (proportional integral) regulator, generates a pulse signal for controlling the on-off of a switching device, and drives the DC/DC circuit to improve the photovoltaic output voltage;
the DC/AC driving circuit adopts double closed-loop control of a direct-current voltage outer loop and a current inner loop, is regulated by a PI regulator, and generates PWM waves after dq-abc coordinate transformation to drive the DC/AC circuit;
the DC/AC circuit is connected to the grid via an inductive filter.
2. The two-stage grid-connected photovoltaic power generation system of claim 1, wherein the DC/DC circuit is a Boost converter.
3. The two-stage grid-connected photovoltaic power generation system according to claim 1 or 2, wherein the DC/AC driving circuit obtains a voltage corresponding to the maximum power from the photovoltaic output voltage and current through MPPT algorithm, and the voltage is used as a reference signal for outer loop voltage control, the voltage reference signal is compared with the actual voltage and adjusted by a voltage regulator to generate an inner loop current reference signal, and then the inner loop current reference signal is compared with the actual current, and a pulse signal for controlling on/off of the switching device is generated by a current controller to drive the DC/DC circuit.
4. The two-stage grid-connected photovoltaic power generation system of claim 1, wherein the DC/AC circuit is a grid-connected inverter.
5. The two-stage grid-connected PV power generation system of claim 1 or 2, wherein the DC/AC drive circuit is in particular a given DC voltage reference Udc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdBy comparison, by current regulatorsAdjusting; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
6. The control method of the two-stage photovoltaic grid-connected power generation system according to any one of claims 1 to 5, characterized by comprising the following steps:
1) voltage U output by photovoltaic module is collected in real timepvCurrent Ipv；
2) The photovoltaic module is output at the maximum power, a voltage outer ring and a current inner ring are adopted for controlling, a PI regulator is used for regulating, a pulse signal for controlling the on-off of a switch device is generated, and a DC/DC circuit is driven to improve the photovoltaic output voltage so as to meet the requirement of grid-connected inversion;
3) the DC/DC circuit passing through a capacitor C2Is electrically connected with the DC/AC circuit;
4) double closed-loop control of a direct-current voltage outer ring and a current inner ring is adopted, the regulation is carried out through a PI regulator, and then the dq-abc coordinate transformation is carried out to generate PWM waves to drive a DC/AC circuit;
5) the DC/AC circuit is connected to the AC power grid via an inductive filter.
7. The control method of claim 6, wherein the specific method of driving the DC/DC circuit is:
the photovoltaic output voltage and current are subjected to MPPT algorithm to obtain voltage corresponding to the maximum power as a reference signal for outer ring voltage control, the voltage reference signal is compared with actual voltage and is regulated by a voltage regulator to generate an inner ring current reference signal, then the inner ring current reference signal is compared with the actual current, and a pulse signal for controlling the on-off of a switching device is generated by a current controller to drive a DC/DC circuit.
8. The control method of claim 6, wherein the specific method of driving the DC/AC circuit is:
given DC voltage reference valueUdc_refAnd the actual voltage UdcCompared with the reference signal, the reference signal is regulated by a voltage regulator to generate an inner loop active current reference signal Id *With the actual active current IdComparing, and adjusting through a current regulator; given reactive current reference signal Iq *And the actual reactive current IqAnd comparing, adjusting by a current regulator, and performing dq-abc coordinate transformation to generate PWM waves to drive the DC/AC circuit.
9. Control method according to claim 8, characterized in that the active current component IdAnd a reactive current IqThe acquisition steps are as follows:
1) system voltage and current detection module real-time acquisition system three-phase voltage UabcThree-phase current Iabc；
2) The detection module detects a three-phase voltage phase theta of a power grid and the real-time frequency of the power grid by using a single synchronous coordinate system software phase-locked loop, and the phase angle theta is used for all coordinate conversion;
3) three-phase current IabcConverting the current component I into a current component I under a dq coordinate system through an abc-dq coordinate conversion moduledAnd Iq。
10. Control method according to claim 8, characterized in that the direct voltage reference value Udc_refBy Udc0And Udc *The frequency deviation is introduced to form f-U when the power grid frequency has disturbancedcCorrecting DC voltage reference value U in compensation linkdc_ref。
CN201911404557.0A 2019-12-30 2019-12-30 Two-stage type photovoltaic grid-connected power generation system and control method thereof Pending CN110957763A (en)

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Cited By (6)

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