Photovoltaic power generation grid-connected inverter system

Abstract

The invention provides a photovoltaic power generation grid-connected inverter system, and relates to the technical field of power electronics. The photovoltaic array module is electrically connected with the MPPT module and the Boost circuit module, the MPPT module receives electric energy of a photovoltaic array and outputs adjusted electric energy to the Boost circuit module, the Boost circuit module is electrically connected with the grid-connected inverter circuit module, the grid-connected inverter circuit module receives boosted direct current and outputs the boosted direct current to the grid-connected inverter circuit module, and the grid-connected inverter circuit module outputs the boosted direct current to the photovoltaic array module. One end of the inverter circuit module is electrically connected with the power grid, the other end of the inverter circuit module is electrically connected with the power grid and the repetitive control module, the inverter circuit module outputs inverted alternating current, and the repetitive control module is electrically connected with the grid-connected inverter circuit module, receives the inverted alternating current and outputs high-quality alternating current after harmonic suppression and waveform correction. According to the invention, based on the construction of a Simulink simulation platform, parameter adjustment and optimization design are carried out by simulating the operation condition of an actual photovoltaic power generation grid-connected inverter system, and an efficient, stable and low-harmonic distortion photovoltaic power generation grid-connected inverter function is realized through the cooperative work of a plurality of modules.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a photovoltaic power generation grid-connected inverter system. Background Art

[0002] Contemporary new energy sources come in various forms, but fundamentally, their power sources mostly come from clean energy such as solar energy. Among them, solar energy, with its huge reserves, environmental friendliness, and convenience of energy conversion, has demonstrated advantages that other new energy sources cannot match. Among the technological developments and various application forms of solar energy, photovoltaic power generation has become the focus of research in various countries. With the deepening of research, photovoltaic power generation technology has made significant progress, from the early self-sufficient model to today's grid-connected power generation, and its application forms are becoming increasingly diversified.

[0003] Grid-connected power generation has become a hot topic in scientific research in various countries, but there are still some key challenges to be solved. How to improve utilization efficiency through innovative control technology, ensure efficient conversion when the external environment changes, and respond quickly to these changes. When a photovoltaic system is connected to a public power grid, it must meet various grid operation standards, such as harmonic restrictions, to ensure the safe and stable operation of the power grid. However, high-order harmonics are often generated during the DC-AC inversion process. Therefore, studying photovoltaic grid-connected technology, improving the utilization efficiency of photovoltaic power generation, and optimizing the inverter control strategy to suppress high-order harmonics have become important topics to promote the sustainable development of photovoltaic power generation. Summary of the invention

[0004] The main purpose of the present invention is to provide a photovoltaic power generation grid-connected inverter system to solve the technical problems in the prior art of how to improve the utilization efficiency of photovoltaic power generation and reduce the distortion rate.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a photovoltaic power generation grid-connected inverter system, a grid-connected inverter simulation model is constructed based on the Simulink simulation platform, including a photovoltaic array module, an MPPT module, a Boost boost circuit module, a grid-connected inverter circuit module and a repetitive control module; Among them, the photovoltaic array module is electrically connected to the MPPT module and the Boost boost circuit module, the MPPT module is connected to the Boost boost circuit module, the other end of the Boost boost circuit module is electrically connected to the grid-connected inverter circuit module, and the other end of the grid-connected inverter circuit module is electrically connected to the repetitive control module, thereby reducing the harmonic distortion rate of the photovoltaic power generation grid-connected inverter system.

[0006] In the preferred embodiment, the MPPT module includes a measurement table for the output power, output current and output voltage of the photovoltaic array, a PWM wave generator and a maximum power algorithm module; wherein the measurement table for the output power, output current and output voltage of the photovoltaic array is connected to the front-end photovoltaic array module, the front end of the maximum power algorithm module is connected to the output end of the photovoltaic array module, and the back end of the maximum power algorithm module is connected to the input end of the PWM wave generator.

[0007] In a preferred embodiment, the photovoltaic array module is connected to the MPPT module and is used to transmit the output voltage and output current data of the photovoltaic array to the MPPT module.

[0008] In the preferred embodiment, the MPPT module includes a measurement table for the output power, output current and output voltage of the photovoltaic array, a PWM wave generator and a maximum power algorithm module; wherein the measurement table for the output power, output current and output voltage of the photovoltaic array is connected to the front-end photovoltaic array module, the front end of the maximum power algorithm module is connected to the output end of the photovoltaic array module, and the back end of the maximum power algorithm module is connected to the input end of the PWM wave generator.

[0009] In the preferred embodiment, the Boost circuit module comprises a resistor and a capacitor RC, an inductor L, an insulated gate bipolar transistor IGBT, a diode D1 and a voltmeter V1; Among them, the resistor, capacitor RC and inductor L are used to combine into a filter element; the insulated gate bipolar transistor IGBT is used to raise the lower voltage applied to its left side and output it on its right side; the diode D1 is used to filter the harmonics in the DC current; the voltmeter V1 is used to measure the output voltage at the rightmost end of the Boost circuit module.

[0010] In a preferred embodiment, the MPPT module is connected to the Boost circuit module, so that the MPPT module can control the Boost circuit module.

[0011] In a preferred embodiment, the front end of the insulated gate bipolar transistor in the Boost circuit module is connected in series with the inductor L and then in parallel with the resistor and capacitor RC, and the rear end is connected in series with the diode D1 and then in parallel with the voltmeter V1.

[0012] In a preferred embodiment, the grid-connected inverter circuit module includes a resistor-capacitor filter element RC1, an inverter bridge B1, a resistor-inductor element RL1, an ammeter A, and a voltmeter V.

[0013] In the preferred solution, the front end of the inverter bridge B1 in the grid-connected inverter circuit module is connected in parallel with the resistor-capacitor filter element RC1, and the rear end is connected in series with the resistor-inductor element RL1 and the ammeter A, and then connected in parallel with the voltmeter V2.

[0014] In the preferred embodiment, the ambient temperature of the photovoltaic array module is set to 25°C and the light intensity is 1000W / m 2 , add a step response to the light intensity, and the light intensity will increase by 900W / m after 1s 2 , the parameters of a single photovoltaic cell are selected as follows: open circuit voltage U oc =36.3V, short-circuit current I sc =7.84A, maximum power point voltage U m =29V, maximum power point current I m =7.35A, and 8 photovoltaic cells are connected in series, and then 3 groups are connected in parallel.

[0015] The present invention provides a photovoltaic power generation grid-connected inverter system, including a photovoltaic array module electrically connected to an MPPT module and a Boost boost circuit module to provide initial electric energy; the MPPT module is a maximum power tracking control module, which receives the electric energy of the photovoltaic array and outputs the adjusted electric energy to the Boost boost circuit module, and the Boost boost circuit module receives the adjusted electric energy; the other end is electrically connected to the grid-connected inverter circuit module, and outputs the boosted direct current; the grid-connected inverter circuit module receives the boosted direct current, and the other end is electrically connected to the power grid and the repetitive control module, and outputs the inverted alternating current, and the repetitive control module is electrically connected to the grid-connected inverter circuit module, receives the inverted alternating current, and outputs high-quality alternating current after harmonic suppression and waveform correction. This embodiment is constructed based on the Simulink simulation platform, and by simulating the operation of the actual photovoltaic power generation grid-connected inverter system, parameter adjustment and optimization design are performed, and through the collaborative work of multiple modules, an efficient, stable, and low harmonic distortion photovoltaic power generation grid-connected inverter function is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: Figure 1 The present invention is a connection diagram of a photovoltaic power generation grid-connected inverter system Figure 2 It is a simulation model diagram constructed by the present invention; Figure 3 This is a circuit path diagram of the RL charging of the present invention; Figure 4 This is a circuit path diagram of the RL discharge of the present invention; Figure 5 It is a grid-connected inverter voltage waveform diagram without using a repeated control module in the prior art of the present invention; Figure 6 This is a grid-connected inverter voltage waveform diagram using a repeated control module in the present invention. DETAILED DESCRIPTION

[0017] Example 1 like Figure 1-2 As shown, a photovoltaic power generation grid-connected inverter system is constructed based on the Simulink simulation platform to build a grid-connected inverter simulation model, including a photovoltaic array module, an MPPT module, a Boost boost circuit module, a grid-connected inverter circuit module and a repetitive control module; Among them, the photovoltaic array module is electrically connected to the MPPT module and the Boost boost circuit module, the MPPT module is connected to the Boost boost circuit module, the other end of the Boost boost circuit module is electrically connected to the grid-connected inverter circuit module, and the other end of the grid-connected inverter circuit module is electrically connected to the repetitive control module, thereby reducing the harmonic distortion rate of the photovoltaic power generation grid-connected inverter system.

[0018] In this embodiment, the MPPT module is a maximum power point tracking control module.

[0019] In this embodiment, the photovoltaic array module is electrically connected to the MPPT module and the Boost circuit module to provide initial electric energy. The MPPT module receives the electric energy of the photovoltaic array and outputs the adjusted electric energy to the Boost circuit module. The Boost circuit module receives the adjusted electric energy. The other end is electrically connected to the grid-connected inverter circuit module to output the boosted DC power. The grid-connected inverter circuit module receives the boosted DC power, and the other end is electrically connected to the power grid and the repetitive control module to output the inverted AC power. The repetitive control module is electrically connected to the grid-connected inverter circuit module to receive the inverted AC power and output high-quality AC power after harmonic suppression and waveform correction. This embodiment is constructed based on the Simulink simulation platform. By simulating the operation of the actual photovoltaic power generation grid-connected inverter system, parameter adjustment and optimization design are performed. Through the collaborative work of multiple modules, a photovoltaic power generation grid-connected inverter function with high efficiency, stability and low harmonic distortion is realized.

[0020] In this embodiment, under given environmental conditions and photovoltaic cell parameters, the photovoltaic array module will generate a large amount of electrical energy. When the light intensity changes stepwise, the system needs to have a fast-response power regulation capability to maintain the stability of the power grid. At the same time, considering the influence of temperature effects and photovoltaic cell connection methods, multiple factors are comprehensively considered to ensure efficient and stable operation.

[0021] In a preferred embodiment, the photovoltaic array module is connected to the MPPT module to transmit the output voltage and output current data of the photovoltaic array to the MPPT module.

[0022] In the preferred embodiment, the MPPT module includes a measurement meter for the output power, output current and output voltage of the photovoltaic array, a PWM wave generator and a maximum power algorithm module; wherein the measurement meter for the output power, output current and output voltage of the photovoltaic array is connected to the front-end photovoltaic array module, the front end of the maximum power algorithm module is connected to the output end of the photovoltaic array module, and the back end of the maximum power algorithm module is connected to the input end of the PWM wave generator.

[0023] In this embodiment, the MPPT module monitors the output power, output current and output voltage of the photovoltaic array in real time through a measuring meter, and uses a specific algorithm to calculate the maximum power point under the current conditions. According to the optimal operating point information calculated by the algorithm, the PWM wave generator generates a corresponding PWM signal, and then uses the PWM signal to control the switching elements (such as MOSFET, IGBT, etc.) in the power regulation circuit, thereby adjusting the output voltage and current of the photovoltaic array so that it operates near the maximum power point.

[0024] In this embodiment, the resistor and capacitor RC are a resistor R and a capacitor C connected in series, and the following components: the resistor and capacitor filter element RC1, the resistor and inductor element RL1, and the resistor and inductor element RL are all connected in series.

[0025] In the preferred embodiment, the Boost circuit module includes a resistor and a capacitor RC, an inductor L, an insulated gate bipolar transistor IGBT, a diode D1 and a voltmeter V1; Among them, the resistor, capacitor RC and inductor L are used to combine into a filter element; the insulated gate bipolar transistor IGBT is used to raise the lower voltage applied to its left side and output it on its right side; the diode D1 is used to filter the harmonics in the DC current; the voltmeter V1 is used to measure the output voltage at the rightmost end of the Boost circuit module.

[0026] In this embodiment, in the Boost boost circuit, the resistor and capacitor RC are combined into a low-pass filter to smooth the output voltage and reduce ripple. The inductor L stores electrical energy from the input power supply. IGBT is a switching element in the Boost boost circuit, which is used to control the on and off of the circuit. When the IGBT is turned on, the input power supply supplies power to the load through the inductor L; when the IGBT is turned off, the inductor L releases energy and continues to flow through the diode D1 to achieve the boost function. The diode D1 is used as a freewheeling diode in the Boost boost circuit. When the switching element IGBT is turned off, the electrical energy released by the inductor L is allowed to continue to flow through the load circuit, thereby maintaining the stability of the output voltage. At the same time, the diode D1 can also prevent the current from flowing in the opposite direction and protect other components in the circuit.

[0027] In this embodiment, the working principle of the Boost circuit is specifically as follows: When the IGBT is turned on, the input power supplies power to the load through the inductor L, and the inductor L starts to store electrical energy. At this time, the diode D1 is in the cut-off state; When the IGBT is turned off, the inductor L releases the stored electrical energy and continues to flow through the diode D1. Since the current in the inductor L cannot be suddenly interrupted at this time, it will continue to flow and pass through the load circuit, while increasing the output voltage; After filtering by resistor and capacitor RC, the output voltage becomes smoother and the ripple is reduced; By repeating the above steps, the Boost circuit can increase the input voltage to the required output voltage.

[0028] In a preferred solution, the MPPT module is connected to the Boost circuit module, so that the MPPT module controls the Boost circuit module.

[0029] In this embodiment, the output of the MPPT control module is connected to the input of the Boost circuit module. During the process of real-time tracking of the maximum power point, the MPPT control module will continuously compare the difference between the current operating point and the maximum power point, and adjust the control signal according to the difference so that the operating point gradually approaches the maximum power point. At the same time, the Boost circuit module will also dynamically adjust the on-off time of the switching element according to the control signal of the MPPT control module to achieve precise voltage regulation and output, which significantly improves the energy conversion efficiency and output performance of the photovoltaic system.

[0030] In the preferred solution, the front end of the insulated gate bipolar transistor in the Boost circuit module is connected in series with the inductor L and then in parallel with the resistor and capacitor RC, and the rear end is connected in series with the diode D1 and then in parallel with the voltmeter V1.

[0031] like Figure 2 As shown, the inductor L is connected in series with the IGBT, which is the core part of the Boost circuit, and then connected in parallel with the series resistor and capacitor RC; the diode D1 is connected in series with the rear end of the IGBT to form a freewheeling loop, and the voltmeter V1 is connected in parallel at the output end to measure the output voltage after the boost.

[0032] In the preferred embodiment, the grid-connected inverter circuit module includes a resistor-capacitor filter element RC1, an inverter bridge B1, a resistor-inductor element RL1, an ammeter A, and a voltmeter V.

[0033] In this embodiment, the resistor and capacitor RC are connected in series to form a low-pass filter to filter out high-frequency noise and interference. The inverter bridge B1 is the core part of the grid-connected inverter circuit, which converts DC power into AC power. The inductor L can store electrical energy and release it when needed, which helps to smooth the fluctuations of output current and voltage. The ammeter A and voltmeter V are used to monitor current and voltage respectively. The various components in the grid-connected inverter circuit module work together to convert DC power into high-quality AC power and safely and stably connect it to the power grid.

[0034] In this embodiment, Figure 3 As shown in the figure, when RL is charged, the circuit path situation, the direction of current flowing through the resistor RL is shown by the red arrow in the figure.

[0035] Similarly, if Figure 4 As shown, when RL is discharged, the direction of current flowing through the resistor RL is shown by the red arrow in the figure; When RL is charging, if the anode (positive terminal) of diode D is connected to a higher potential (i.e., U') and the cathode (negative terminal) is connected to a lower potential (i.e., the negative terminal of capacitor C or ground), then diode D will be in the on state, allowing current to flow.

[0036] In the preferred solution, the front end of the inverter bridge B1 in the grid-connected inverter circuit module is connected in parallel with the resistor-capacitor filter element RC1, and the rear end is connected in series with the resistor-inductor element RL1 and the ammeter A, and then connected in parallel with the voltmeter V2.

[0037] The function of the resistor and capacitor filter element RC1 is the same as that of the resistor and capacitor RC; the resistor and inductor element RL1 is connected in series with the output end of the inverter bridge B1 and is located before the ammeter A. It plays the role of current limiting, filtering and energy storage in the circuit, which helps to smooth the fluctuations of the output current and voltage.

[0038] When the DC power supply is input to the grid-connected inverter circuit, it is first filtered by RC1 to obtain a stable DC voltage.

[0039] The stable DC voltage is fed into the inverter bridge B1, and the DC power is converted into AC power by controlling the switching state of the power electronic devices in the inverter bridge.

[0040] After being filtered and current limited by RL1, the AC power is output to the grid or load.

[0041] The ammeter A and the voltmeter V2 monitor the output current and output voltage in real time, provide real-time information about the circuit load and efficiency, and ensure the synchronization and matching of the output voltage with the grid voltage.

[0042] In summary, the grid-connected inverter circuit module realizes the function of efficiently and stably converting DC power into AC power and safely connecting it to the power grid through reasonable component configuration and connection method.

[0043] In the preferred embodiment, Figure 2 As shown, the parameters in this embodiment are preferably set as follows: 1) Build a grid-connected inverter simulation model based on the Simulink simulation platform.

[0044] 2) Changes in environmental conditions and light intensity: The ambient temperature of the photovoltaic array module is set to 25°C, the light intensity is 1000W / m2, and a step response is added to the light intensity. After 1s, the light intensity will increase by 900W / m2.

[0045] 3) Photovoltaic cell parameters and connection methods: The parameters of a single photovoltaic cell are selected as follows: Open circuit voltage Uoc = 36.3V, the maximum voltage that can be generated across the photovoltaic cell when there is no load; Short-circuit current Isc=7.84A, which means the maximum current flowing when the two ends of the photovoltaic cell are short-circuited; Maximum power point voltage Um=29V, maximum power point current Im=7.35A, the point where the photovoltaic cell can convert light energy into electrical energy with the highest efficiency; 4) Connect 8 photovoltaic cells in series and then connect 3 groups in parallel. Connecting 8 photovoltaic cells in series will increase the voltage, while connecting 3 groups in parallel will increase the current. Therefore, the total voltage after series connection is 8×29V=232V (at the maximum power point), and the total current after parallel connection is 3×7.35A=22.05A (at the maximum power point).

[0046] However, it is important to note that under open-circuit and short-circuit conditions, the voltage and current will also increase accordingly.

[0047] By running the grid-connected inverter simulation model, the operating parameters of the grid-connected inverter are simulated and tested, including: Step 1: Given the light intensity and ambient temperature input values ​​of the photovoltaic array module, the PU curve of the photovoltaic array can be drawn according to the mathematical model. Under constant light intensity and temperature conditions, the output power of the photovoltaic cell is not constant, but presents a specific curve with the change of output voltage. This curve has a characteristic that its power value first increases with the increase of voltage, reaches a peak value, and then gradually decreases.

[0048] Step 2: The maximum power point tracking control module collects the output voltage, output current and output power of the output side of the photovoltaic array module.

[0049] Step 3: The resistor and capacitor parallel and inductor series structures of the Boost module will filter the output current of the photovoltaic array. The output voltage of the photovoltaic array is applied to both ends of the insulated gate bipolar transistor, and the output current of the insulated gate bipolar transistor is filtered by the diode.

[0050] Step 4: The PWM wave generator of the maximum power point tracking control module outputs a PWM wave and transmits it to the signal control port of the insulated gate bipolar diode of the Boost module.

[0051] Step 5: The output voltage of the Boost module is applied to both ends of the inverter bridge.

[0052] Step 6: The output voltage of the Boost module measured by the voltmeter is collected and transmitted to the repetitive control module.

[0053] Step 7, the PWM generator of the repeat control module outputs a PWM wave and transmits it to the signal control end of the inverter bridge in the grid-connected inverter circuit module.

[0054] Step 8: An ammeter is connected in series to the output end of the inverter bridge, and is connected in parallel to a voltmeter and an AC voltage source. The voltmeter and the ammeter are connected to an oscilloscope.

[0055] In this embodiment, by repeating the function of the control module, the distortion rate of photovoltaic power generation is significantly reduced, thereby improving the utilization efficiency. Figure 5 As shown in the figure, the grid-connected inverter voltage waveform without the repeated control module shows a certain lag with the reference grid voltage. Figure 6 As shown, by adopting the technical solution of this embodiment, that is, using the repeated control module, it can be seen from the grid-connected inverter voltage waveform that the lag with the reference grid voltage is eliminated, thereby reducing the distortion rate of photovoltaic power generation.

[0056] The above embodiments are only preferred technical solutions of the present invention and should not be regarded as limiting the present invention. The protection scope of the present invention shall be the technical solutions recorded in the claims, including equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. A photovoltaic power generation grid-connected inverter system, which builds a grid-connected inverter simulation model based on the Simulink simulation platform, characterized in that: It includes photovoltaic array module, MPPT module, Boost circuit module, grid-connected inverter circuit module and repetitive control module; Among them, the photovoltaic array module is electrically connected to the MPPT module and the Boost boost circuit module, the MPPT module is connected to the Boost boost circuit module, the other end of the Boost boost circuit module is electrically connected to the grid-connected inverter circuit module, and the other end of the grid-connected inverter circuit module is electrically connected to the repetitive control module, thereby reducing the harmonic distortion rate of the photovoltaic power generation grid-connected inverter system.

2. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: The photovoltaic array module is connected to the MPPT module and is used to transmit the output voltage and output current data of the photovoltaic array to the MPPT module.

3. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: The MPPT module includes a measurement meter for the output power, output current and output voltage of the photovoltaic array, a PWM wave generator and a maximum power algorithm module; wherein the measurement meter for the output power, output current and output voltage of the photovoltaic array is connected to the front-end photovoltaic array module, the front end of the maximum power algorithm module is connected to the output end of the photovoltaic array module, and the back end of the maximum power algorithm module is connected to the input end of the PWM wave generator.

4. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: The Boost circuit module includes a resistor and a capacitor RC, an inductor L, an insulated gate bipolar transistor IGBT, a diode D1 and a voltmeter V1; Among them, the resistor, capacitor RC and inductor L are used to combine into a filter element; the insulated gate bipolar transistor IGBT is used to raise the lower voltage applied to its left side and output it on its right side; the diode D1 is used to filter the harmonics in the DC current; the voltmeter V1 is used to measure the output voltage at the rightmost end of the Boost circuit module.

5. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: The MPPT module is connected to the Boost circuit module, and is used to enable the MPPT module to control the Boost circuit module.

6. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: In the Boost circuit module, the front end of the insulated gate bipolar transistor is connected in series with the inductor L and then in parallel with the resistor and capacitor RC, and the rear end is connected in series with the diode D1 and then in parallel with the voltmeter V1.

7. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: The grid-connected inverter circuit module includes a resistor-capacitor filter element RC1, an inverter bridge B1, a resistor-inductor element RL1, an ammeter A, and a voltmeter V.

8. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: In the grid-connected inverter circuit module, the front end of the inverter bridge B1 is connected in parallel with the resistor-capacitor filter element RC1, and the rear end is connected in series with the resistor-inductor element RL1 and the ammeter A, and then connected in parallel with the voltmeter V2.

9. The photovoltaic power generation grid-connected inverter system according to claim 1, characterized in that: The ambient temperature of the photovoltaic array module is set to 25°C and the light intensity is 1000W / m 2 , add a step response to the light intensity, and the light intensity will increase by 900W / m after 1s 2 , the parameters of a single photovoltaic cell are selected as follows: open circuit voltage U oc =36.3V, short-circuit current I sc =7.84A, maximum power point voltage U m =29V, maximum power point current I m =7.35A, and 8 photovoltaic cells are connected in series, and then 3 groups are connected in parallel.

Images