CN212969069U

CN212969069U - Photovoltaic inverter

Info

Publication number: CN212969069U
Application number: CN202021551808.6U
Authority: CN
Inventors: 居林; 金海燕; 卢盈; 吴生闻
Original assignee: Aishiwei New Energy Technology Yangzhong Co ltd
Current assignee: Aishiwei New Energy Technology Yangzhong Co ltd
Priority date: 2020-07-30
Filing date: 2020-07-30
Publication date: 2021-04-13
Anticipated expiration: 2030-07-30

Abstract

The utility model discloses a photovoltaic inverter, it can supply the use of back level power device after converting higher photovoltaic open circuit voltage. The photovoltaic inverter comprises a BOOST circuit and an inverter circuit which are connected in series, the photovoltaic inverter is provided with an input end positive electrode PV + and an input end negative electrode PV-which are used for connecting a photovoltaic panel, the photovoltaic inverter also comprises a first divider resistor, a second divider resistor, a first switch and a second switch, the first divider resistor and the second divider resistor are connected between the input end positive electrode PV + and the input end negative electrode PV-, the first switch is connected in parallel with two ends of the first divider resistor, and the second switch is connected between the second divider resistor and the input end negative electrode PV-; the positive electrode of the input end of the BOOST circuit is connected to the middle point of the first voltage-dividing resistor and the second voltage-dividing resistor, and the negative electrode of the input end of the BOOST circuit is connected to the negative electrode PV-of the input end.

Description

Photovoltaic inverter

Technical Field

The utility model belongs to the photovoltaic power generation field, concretely relates to photovoltaic inverter.

Background

The photovoltaic inverter is a core device for converting direct current provided by a Solar module into alternating current for civil use or industrial use, and the position of the photovoltaic inverter in the field of new energy is more and more important. The MPPT input voltage range of the photovoltaic inverter is designed well at present. However, under the working condition that the maximum output open-circuit voltage of the photovoltaic panel connected by a user is higher and the MPPT working voltage is lower under some special conditions, if the current photovoltaic inverter is used, when the open-circuit voltage is higher and the inverter is not working, the voltage is higher, exceeds the input voltage range of the inverter, and the inverter may be permanently damaged. For example, currently, limited by the voltage levels of power devices such as capacitors and IGBTs, the maximum MPPT input voltage of the single-camera photovoltaic inverter is 600V, but the maximum output open-circuit voltage of a photovoltaic panel connected by a user in some special cases is higher, such as 800V. If current photovoltaic inverters are used, the inverter may be permanently damaged beyond the inverter input voltage range at higher open circuit voltages. If the voltage level of the capacitor and the IGBT is raised, the cost of the whole system is greatly increased, and the voltage margin of the power device is too large due to the fact that the actually used voltage and the raised voltage of the power device have a certain distance, so that design waste is caused.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, the utility model provides a photovoltaic inverter, it can supply the use of back level power device after converting higher photovoltaic open circuit voltage.

The utility model provides a photovoltaic inverter, including BOOST BOOST circuit and the inverter circuit who concatenates each other, photovoltaic inverter has the positive PV + of input and the negative PV-of input that are used for connecting photovoltaic panel, photovoltaic inverter still includes first divider resistance, second divider resistance, first switch and second switch, first divider resistance with the second divider resistance concatenates between positive PV + of input and the negative PV-of input, first switch connect in parallel in first divider resistance both ends, the second switch concatenates between the second divider resistance and the negative PV-of input; the positive electrode of the input end of the BOOST circuit is connected to the middle point of the first voltage-dividing resistor and the second voltage-dividing resistor, and the negative electrode of the input end of the BOOST circuit is connected to the negative electrode PV-of the input end.

Preferably, the photovoltaic inverter has a first operating mode and a second operating mode, the first switch is closed and the second switch is open when the photovoltaic inverter is in the first operating mode; when the photovoltaic inverter is in a second operating mode, the first switch is open and the second switch is closed.

Preferably, the photovoltaic inverter further includes a sampling circuit for detecting a voltage input from the photovoltaic panel, and a controller connected to the sampling circuit and controlling the first switch and the second switch.

More preferably, the controller is electrically connected to the first switch and the second switch respectively, and when the voltage value is smaller than or equal to the set threshold, the controller outputs a high-level driving signal to drive the first switch and the second switch; when the voltage value is larger than the set threshold value, the controller outputs a low-level driving signal to drive the first switch and the second switch.

Further, the first switch is a normally open relay, and the second switch is a normally closed relay.

More preferably, the sampling circuit includes an operational amplifier and two sampling resistors, one ends of the two sampling resistors are respectively connected to the positive input terminal PV + and the negative input terminal PV-, the other ends of the two sampling resistors are respectively connected to the two input terminals of the operational amplifier, and the output terminal of the operational amplifier is connected to the controller.

More preferably, the controller is a DSP chip.

The utility model adopts the above scheme, compare prior art and have following advantage:

the utility model discloses a photovoltaic inverter can supply the back level power device to use after reducing higher photovoltaic output voltage of opening a way earlier, and back level power device work back, panel output voltage descends, and preceding stage circuit can not continue to reduce the low pressure of panel output, but uses panel output voltage to supply the work of back level power device. Therefore, the photovoltaic inverter can adapt to higher open-circuit voltage, the difference between the efficiency and the efficiency of a common inverter is the same, the cost cannot be greatly increased, and the power device is the same as the common inverter and does not need to be replaced. The photovoltaic inverter has few devices and low cost, and is particularly suitable for photovoltaic power generation scenes with higher open-circuit voltage of a photovoltaic panel and lower applicable voltage range of a normal photovoltaic inverter.

Drawings

In order to more clearly illustrate the technical solution of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is a schematic diagram of a photovoltaic power generation system employing a photovoltaic inverter according to an embodiment of the present invention.

Wherein:

1. a photovoltaic panel; 2. a photovoltaic inverter; 3. a power grid;

21. a BOOST voltage BOOST circuit; 22. an INV inverter circuit; 23. a first voltage dividing resistor; 24. a second voltage dividing resistor; 25. a first switch; 26. a second switch; 27. sampling a resistor; 28. carrying out operational amplification; 29. and a controller.

Detailed Description

The following detailed description of the preferred embodiments of the invention, taken in conjunction with the accompanying drawings, enables the advantages and features of the invention to be more readily understood by those skilled in the art. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.

The present embodiments provide a photovoltaic inverter that uses lower voltage power devices to accommodate higher photovoltaic panel open circuit voltages. Fig. 1 shows a photovoltaic power generation system employing the photovoltaic inverter. Referring to fig. 1, the photovoltaic power generation system mainly comprises a photovoltaic panel 1, a photovoltaic inverter 2 and a power grid 3 which are connected in sequence, wherein the photovoltaic panel 1 is used for converting the energy of sunlight into electric energy and outputting direct current, and the electric energy is supplied to the photovoltaic inverter 2 to be converted into alternating current and then fed to the power grid 3.

The photovoltaic inverter 2 specifically includes a BOOST circuit 21 and an inverter circuit 22 connected in series, and sequentially performs DC-DC BOOST conversion and DC-AC conversion on the current. The photovoltaic inverter 2 has an input positive terminal PV + and an input negative terminal PV "for connecting the photovoltaic panel 1, and an output positive terminal and an output negative terminal for connecting the inverter circuit 22 and the grid 3. The photovoltaic inverter 2 further includes a first voltage dividing resistor 23, a second voltage dividing resistor 24, a first switch 25 and a second switch 26. The first voltage-dividing resistor 23 and the second voltage-dividing resistor 24 are connected in series between the input terminal positive electrode PV + and the input terminal negative electrode PV-, the input terminal positive electrode of the BOOST voltage-boosting circuit 21 is connected to the middle point of the first voltage-dividing resistor 23 and the second voltage-dividing resistor 24, and the input terminal negative electrode of the BOOST voltage-boosting circuit 21 is connected to the input terminal negative electrode PV-. The first switch 25 is connected in parallel to two ends of the first divider resistor 23, and can form a short circuit to the first divider resistor 23; a second switch 26 is connected in series between the second voltage-dividing resistor 24 and the negative terminal PV-of the input terminal, and is capable of disconnecting the second voltage-dividing resistor 24. The photovoltaic inverter 2 has a first operating mode and a second operating mode, when the photovoltaic inverter 2 is in the first operating mode, the first switch 25 is closed and the second switch 26 is open; when the photovoltaic inverter 2 is in the second operating mode, the first switch 25 is open and the second switch 26 is closed.

The photovoltaic inverter 2 further includes a sampling circuit for detecting a voltage input from the photovoltaic panel 1, and a controller 29 connected to the sampling circuit. And a controller 29 for receiving the voltage value detected by the sampling circuit, determining whether the first switch 25 and the second switch 26 need to be closed or opened, and making the first switch 25 closed and the second switch 26 open when the voltage value is less than or equal to a set threshold, and making the first switch 25 open and the second switch 26 closed when the voltage value is greater than the set threshold. Specifically, the first switch 25 is a normally open relay, and the second switch 26 is a normally closed relay. The controller 29 is electrically connected to the first switch 25 (specifically, the normally open contact of the normally open relay) and the second switch 26 (specifically, the normally closed contact of the normally closed relay), respectively.

When the voltage value is less than or equal to the set threshold (lower than the input voltage of the power part of the subsequent stage), the controller 29 outputs a high-level driving signal to drive the first switch 25 and the second switch 26, so that the normally open contact of the first switch 25 is closed to short the first voltage dividing resistor 23, the normally closed contact of the second switch 26 is opened to open the second voltage dividing resistor 24, and the low voltage output by the photovoltaic panel 1 is directly supplied to the BOOST circuit 21 and the INV inverter circuit 22 of the subsequent stage for use without voltage reduction processing. When the voltage value is greater than the set threshold (higher than the input voltage of the power part of the subsequent stage), the controller 29 outputs a low-level driving signal to drive the first switch 25 and the second switch 26, the normally open contact of the first switch 25 is opened, the normally closed contact of the second switch 26 is closed, the first voltage dividing resistor 23 and the second voltage dividing resistor 24 form a loop, the voltage input by the photovoltaic panel 1 is divided, and the higher open-circuit voltage is subjected to voltage reduction processing and then is supplied to the BOOST circuit 21 and the INV inverter circuit 22 of the subsequent stage for use.

The sampling circuit detects the voltage input by the photovoltaic panel 1 in real time and sends it to the controller 29. Once the detected voltage value is lower than the set threshold, the controller 29 outputs a high-level driving signal to switch the photovoltaic inverter 2 back to the first operation mode, to operate normally as a conventional inverter, and to reduce the loss of the first and second

voltage dividing resistors

23 and 24.

Further, the sampling circuit comprises an operational amplifier 28 and two sampling resistors 27, one ends of the two sampling resistors 27 are respectively connected to the positive electrode PV + of the input terminal and the negative electrode PV of the input terminal, the other ends of the two sampling resistors 27 are respectively connected to the two input terminals of the operational amplifier 28, and the output terminal of the operational amplifier 28 is connected to the controller 29. The controller 29 is embodied as a DSP chip.

For example, the MPPT input voltage of the conventional single-camera photovoltaic inverter is 600V at most, and the photovoltaic panel 1 outputs 800V as the maximum open-circuit voltage in some cases. If the photovoltaic inverter 2 using the maximum input voltage of 600V is directly connected to the photovoltaic panel 1 having the maximum open circuit voltage of 800V, the photovoltaic inverter 2 is likely to have a permanent damage failure. The photovoltaic inverter 2 of the present embodiment can solve the problem well, and the specific operation principle is described as follows.

Assume that the withstand voltage of the IGBT and BUS of the inverter rear stage is 600V, and the maximum open circuit voltage of the photovoltaic panel 1 is 800V.

When the open-circuit voltage of the photovoltaic panel 1 is between 0V and 600V, the controller 29 detects that the voltage of the photovoltaic panel 1 is less than 600V through the sampling resistor 27 and the operational amplifier 28, and provides a high-level driving signal to drive the first switch 25 and the second switch 26, so that the normally open contact of the relay is closed, the normally closed contact of the relay is opened, the first divider resistor 23 is short-circuited, the second divider resistor 24 is disconnected from the loop, and the voltage of the photovoltaic panel 1 directly supplies power to the rear-stage power conversion circuit, and the photovoltaic panel 1 normally works like a conventional inverter.

When the open-circuit voltage of the photovoltaic panel 1 is 600V-800V, the controller 29 detects that the voltage of the photovoltaic panel 1 detected by the sampling resistor 27 and the operational amplifier 28 is greater than 600V, a low-level driving signal is given to drive the first switch 25 and the second switch 26, so that the normally open contact of the relay is opened, the normally closed contact of the relay is closed, the first voltage dividing resistor 23 and the second voltage dividing resistor 24 divide the voltage, the voltage of the rear-stage power part is lower than 600V after the voltage division, and the voltage level requirement of the rear-stage power device is met. After the inverter is operated, the MPPT voltage decreases. When the voltage of the photovoltaic panel 1 drops below 600V, the controller 29 detects that the voltage of the photovoltaic panel 1 is less than 600V again, and provides a high-level driving signal to drive the first switch 25 and the second switch 26, so that the normally open contact of the relay is closed, the normally closed contact of the relay is opened, the first voltage dividing resistor 23 is short-circuited again, the second voltage dividing resistor 24 is disconnected from the loop, and the hiccup voltage of the photovoltaic panel 1 directly supplies power to a rear-stage power conversion circuit, and the photovoltaic panel 1 normally works like a traditional inverter.

A control method of the photovoltaic inverter 2 includes the following steps: when the voltage input by the photovoltaic panel 1 is lower than or equal to the set threshold, the first switch 25 is closed, the second switch 26 is opened; when the voltage input by the photovoltaic panel 1 is higher than the set threshold, the first switch 25 is opened and the second switch 26 is closed. Specifically, the controller 29 drives the contacts of the first switch 25 and the second switch 26 to operate, and when the voltage input by the photovoltaic panel 1 is lower than or equal to a set threshold, the controller 29 outputs a high-level driving signal to drive the normally open contact of the first switch 25 to be closed and the normally closed contact of the second switch 26 to be opened; when the voltage input by the photovoltaic panel 1 is higher than the set threshold, the controller 29 outputs a low-level driving signal to drive the normally open contact of the first switch 25 to be opened and the normally closed contact of the second switch 26 to be closed.

The control method further includes the step of detecting the voltage input from the photovoltaic panel 1 in real time by the sampling circuit and transmitting the detected voltage to the controller 29. Once the detected voltage value is lower than the set threshold, the controller 29 outputs a high-level driving signal to switch the photovoltaic inverter 2 back to the first operating mode.

The embodiment is a photovoltaic inverter which can reduce the higher photovoltaic open-circuit output voltage and then be used by a rear-stage power device; after the rear-stage power device works, the output voltage of the panel is reduced, the low voltage output by the panel is not continuously reduced by the front-stage circuit, and the output voltage of the panel is used for the rear-stage power device to work. Therefore, the photovoltaic inverter can adapt to higher open-circuit voltage, the difference between the efficiency and the efficiency of a common inverter is the same, the cost cannot be greatly increased, and the power device is the same as the common inverter and does not need to be replaced. The photovoltaic inverter has few devices and low cost, and is particularly suitable for photovoltaic power generation scenes with higher open-circuit voltage of a photovoltaic panel and lower applicable voltage range of a normal photovoltaic inverter.

The above embodiments are only for illustrating the technical concept and features of the present invention, and are preferred embodiments, which are intended to enable persons skilled in the art to understand the contents of the present invention and to implement the present invention, and thus, the protection scope of the present invention cannot be limited thereby. All equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A photovoltaic inverter, comprising a BOOST BOOST circuit and an inverter circuit connected in series, the photovoltaic inverter having an input positive PV + and an input negative PV-for connecting a photovoltaic panel, characterized in that: the photovoltaic inverter further comprises a first voltage-dividing resistor, a second voltage-dividing resistor, a first switch and a second switch, wherein the first voltage-dividing resistor and the second voltage-dividing resistor are connected in series between the input end positive electrode PV + and the input end negative electrode PV-; the positive electrode of the input end of the BOOST circuit is connected to the middle point of the first voltage-dividing resistor and the second voltage-dividing resistor, and the negative electrode of the input end of the BOOST circuit is connected to the negative electrode PV-of the input end.

2. The photovoltaic inverter of claim 1, wherein: the photovoltaic inverter further comprises a sampling circuit for detecting the voltage input by the photovoltaic panel and a controller connected with the sampling circuit and controlling the first switch and the second switch.

3. The photovoltaic inverter of claim 2, wherein: the controller is electrically connected with the first switch and the second switch respectively.

4. The photovoltaic inverter of claim 3, wherein: the first switch is a normally open relay, and the second switch is a normally closed relay.

5. The photovoltaic inverter of claim 2, wherein: the sampling circuit includes that fortune is put and two sampling resistor, two sampling resistor's one end connect respectively in the anodal PV + of input reaches input negative pole PV-, two sampling resistor's the other end connect respectively in two inputs that fortune was put, the output that fortune was put with the controller is connected.

6. The photovoltaic inverter of claim 2, wherein: the controller is a DSP chip.