Start compensation device for string type photovoltaic inverter

Abstract

The utility model provides a start compensation device used for a string type photovoltaic inverter, the start compensation device is arranged between a photovoltaic assembly and a photovoltaic inverter, the start compensation device comprises a controller and a boost circuit, the input end of the boost circuit is connected in parallel with the two ends of the first photovoltaic assembly, one output end of the boost circuit is connected with the photovoltaic inverter, and the other output end of the boost circuit is connected with the controller. The other output end of the booster circuit is connected to the input end of the second photovoltaic string, the input end of the controller is connected with the first photovoltaic module, and the output end of the controller is connected with the booster circuit. According to the utility model, the output voltage of the photovoltaic group string is adjusted, so that the normal working state of the photovoltaic inverter can be prolonged, and the illumination utilization efficiency of a photovoltaic power generation system can be improved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to photovoltaic power generation technical field, concretely relates to a kind of starting compensation device for string photovoltaic inverter. BACKGROUND

[0002] In photovoltaic power generation system, photovoltaic module is packaged by multiple photovoltaic cells. Directly convert solar light into DC power to realize power generation output. After connecting several photovoltaic modules in series, the circuit unit with certain DC output is formed, called photovoltaic string. By connecting a string photovoltaic inverter in parallel into power grid, small and medium-sized distributed photovoltaic power generation system is formed. Photovoltaic module is connected in series according to the rated input voltage requirement of photovoltaic inverter, so that the output voltage of each string is high, but the current is relatively small.

[0003] In normal power generation process, the number of modules connected by each string of string photovoltaic inverter is fixed, and the output voltage of photovoltaic module under different light intensity is different. When light intensity reaches a certain intensity, the output voltage of string can meet the minimum operating voltage of inverter, and the inverter will start working and send power to power grid. According to national standard, the voltage range of photovoltaic inverter string is 550V~1000V, if the voltage is lower than 550V or higher than 1000V, the inverter will not work normally. In this case, in the morning and evening or other low light intensity, the inverter cannot reach the working voltage condition, so it cannot generate electricity, which causes low utilization rate of solar light of photovoltaic power generation system and cannot realize higher economic benefit. CONTENT OF UTILITY MODEL

[0004] In view of the above shortcomings of prior art, the utility model provides a kind of starting compensation device for string photovoltaic inverter to solve the above technical problems.

[0005] The utility model provides a kind of starting compensation device for string photovoltaic inverter, the starting compensation device is arranged between photovoltaic module and photovoltaic inverter, including controller and boost circuit, wherein, the input end of boost circuit is connected in parallel between the two ends of first photovoltaic module, one output end of boost circuit is connected into photovoltaic inverter, and the input end of second photovoltaic string is connected into another output end of boost circuit, the input end of controller is connected first photovoltaic module, and the output end of controller is connected with boost circuit.

[0006] Further, the boost circuit is a BOOST circuit, comprising: an inductor L, a switch tube Q, a diode D, a capacitor C and a load R, one end of the inductor L and a source electrode of the switch tube Q serving as an input end of the boost circuit, the other end of the inductor L being connected to a drain electrode of the switch tube Q and an anode of the diode D, a cathode of the diode D and the source electrode of the switch tube Q serving as an output end of the boost circuit, the output capacitor C and the load R being connected in parallel across the output end of the boost circuit.

[0007] The starting compensation device for the string type photovoltaic inverter can adjust the voltage of the photovoltaic module at any time, so that the photovoltaic string voltage can meet the minimum working voltage of the inverter as much as possible, the power generation time and power generation capacity of the photovoltaic inverter are improved, the economic benefit of the photovoltaic power generation system is improved, and the product competitiveness is improved.

[0008] In addition, the utility model discloses a design principle is reliable, simple structure, the reconstruction construction is convenient and has low cost, has very extensive application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to make the technical personnel of the present technical field better understand the technical scheme in the present utility model, the following will be in conjunction with the attached drawings in the embodiment of the present utility model, the technical scheme in the embodiment of the present utility model is clearly and completely described, obviously, the described embodiment is only a part of the embodiment of the present utility model, not all the embodiment.

[0010] Figure 1 It is the circuit structure schematic diagram of the device of an embodiment of the application.

[0011] Figure 2 It is the circuit structure schematic diagram of the BOOST circuit of an embodiment of the application. DETAILED DESCRIPTION

[0012] In order to make the technical personnel of the present technical field better understand the technical scheme in the present utility model, the following will be in conjunction with the attached drawings in the embodiment of the present utility model, the technical scheme in the embodiment of the present utility model is clearly and completely described, obviously, the described embodiment is only a part of the embodiment of the present utility model, not all the embodiment.

[0013] It should be noted that the embodiments in the present utility model and the features in the embodiments can be combined with each other without conflict.

[0014] In the description of the utility model, it is necessary to explain that the terms "connected" and "connection" are understood as "electrical connection"; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication between two elements inside. For ordinary skilled persons in the art, the specific meaning of the above terms in the utility model can be understood according to specific circumstances.

[0015] The utility model will be described in detail below with reference to the drawings and in combination with embodiments.

[0016] As Figure 1 Indicated, the utility model provides a kind of starting compensation device for string type photovoltaic inverter, the starting compensation device is arranged between photovoltaic module and photovoltaic inverter, including controller and boost circuit, wherein, the input end of boost circuit is connected in parallel at the two ends of first photovoltaic module, one output end of boost circuit is connected into photovoltaic inverter, another output end of boost circuit is connected into the input end of second photovoltaic string, the input end of controller is connected first photovoltaic module, and the output end of controller is connected with boost circuit.

[0017] In an embodiment, the boost circuit is BOOST loop, as Figure 2 Indicated, including: inductance L, switch tube Q, diode D, capacitor C and load R, one end of inductance L and the source electrode of switch tube Q as the input end of boost circuit, the other end of inductance L is connected the drain electrode of switch tube Q and the anode of diode D, the cathode of diode D and the source electrode of switch tube Q as the output end of boost circuit, output capacitor C and load R are connected in parallel at the output end of boost circuit.

[0018] The present application is aimed at the case that photovoltaic string output voltage is low and insufficient to start photovoltaic inverter in the morning, evening or other low sunlight intensity. For this case, the output voltage of photovoltaic string is adjusted to enable photovoltaic inverter to start in advance when sunlight is low, or to enable photovoltaic inverter to delay shutdown in the evening to extend the power generation time of photovoltaic power generation system and improve the utilization efficiency of sunlight. When sunlight intensity is sufficient, the original output voltage of photovoltaic string is sufficient to start photovoltaic inverter, so boost regulation is not needed for string voltage.

[0019] The working process of the controller is as follows: firstly, the output voltage of the group string is detected. The controller is connected to the photovoltaic module 1. Generally, the working voltage of the photovoltaic group string is the same, so the voltage of the photovoltaic group string can be measured according to the voltage of the photovoltaic module 1 multiplied by the number of photovoltaic modules in the group string. The minimum working voltage of the inverter is stored in the controller. The output voltage of the group string and the minimum working voltage are compared. Only when the output voltage of the group string is greater than or equal to the minimum working voltage of the photovoltaic inverter, the inverter will work normally and generate power to the power grid. If the output voltage of the group string is less than the minimum working voltage, the boost circuit will increase the output voltage of the module to the minimum working voltage, so that the photovoltaic inverter will start to generate power to the power grid. If the original output voltage of the group string reaches the minimum working voltage of the photovoltaic inverter during the boost process, the boost circuit will stop adjusting the voltage of the module, and the photovoltaic inverter will work through the original output voltage of the group string.

[0020] It should be noted that when the light intensity is low in the morning or evening, if the voltage is too low and the module is forced to boost, the output power cannot meet the power requirement of the inverter. Therefore, when the boost compensation is started, the output voltage of the group string should be less than the minimum working voltage, but greater than or equal to the voltage compensation threshold. When the output voltage of the group string reaches the voltage compensation threshold, the boost compensation is started. The voltage compensation threshold is set according to the power requirement of the inverter or the change of light intensity, so that the photovoltaic inverter can start earlier or stop later for about half an hour. Because in the design stage of the device, according to the minimum working voltage and the voltage compensation threshold, the voltage difference to be compensated is determined. If the voltage compensation threshold is too low, the voltage difference to be compensated is too large. When the original output voltage of the group string is close to the minimum working voltage, the compensated voltage may exceed the maximum voltage of the photovoltaic inverter, so the value of the voltage compensation threshold should also meet this requirement.

[0021] In the application, the controller can select a programmable microcontroller such as STM32F4 / F7, the built-in ADC module supports multi-channel sampling, the photovoltaic module voltage monitoring function of the application can be realized, and the PWM output can be provided to directly drive the switch tube in the boost circuit of the application. The controller involves voltage sampling function, voltage comparison function, minimum working voltage setting function, voltage compensation threshold setting function and output boost control function, the voltage sampling function is used to collect the output voltage of the first photovoltaic module, the minimum working voltage setting function is used to input the minimum working voltage of the photovoltaic inverter to start working into the controller, and the voltage compensation threshold setting function is used to input the voltage compensation threshold of the photovoltaic inverter to start working into the controller; the voltage comparison function is used to calculate the string voltage, and the string voltage, the minimum working voltage and the voltage compensation threshold are compared, the switch tube Q of the BOOST loop is turned on when the string voltage reaches the voltage compensation threshold, the switch tube Q of the BOOST loop is continuously turned on when the string voltage is greater than the voltage compensation threshold and the minimum working voltage, and the switch tube Q of the BOOST loop is turned off when the string voltage reaches the minimum working voltage. In the device design stage, according to the minimum working voltage and the voltage compensation threshold, the voltage difference value that needs to be compensated is determined, and the parameters of each element of BOOST are further determined.

[0022] The voltage regulating device of the embodiment is connected to the first photovoltaic module, and adjusts the output voltage of the first photovoltaic module. In actual application, the boost circuit can be connected to multiple photovoltaic modules, which can have more obvious voltage boost. However, because the purpose of the application is to appropriately prolong the working time of the inverter under the condition that the light can ensure normal power generation, the voltage boost range is small, and the connection to one photovoltaic module is sufficient to meet the demand.

[0023] Although the utility model has been described in detail with reference to the drawings and in combination with the preferred embodiments, the utility model is not limited thereto. Without departing from the spirit and essence of the utility model, those skilled in the art can make various equivalent modifications or replacements to the embodiments of the utility model, and these modifications or replacements should be within the scope of the utility model. Any person skilled in the art within the technical range disclosed by the utility model can easily think of changes or replacements, which should be covered within the protection scope of the utility model. Therefore, the protection scope of the utility model should be subject to the protection scope of the claims.

Claims

1. A start-up compensation device for a string inverter, characterized by, The starting compensation device is arranged between the photovoltaic module and the photovoltaic inverter, and comprises a controller and a boost circuit, wherein the input end of the boost circuit is connected in parallel across the first photovoltaic module, one output end of the boost circuit is connected to the photovoltaic inverter, and the other output end of the boost circuit is connected to the input end of the second photovoltaic module, the input end of the controller is connected to the first photovoltaic module, and the output end of the controller is connected to the boost circuit.

2. The apparatus of claim 1, wherein, The boost circuit is a BOOST circuit, comprising an inductor L, a switch tube Q, a diode D, a capacitor C and a load R, one end of the inductor L and the source of the switch tube Q serving as the input end of the boost circuit, the other end of the inductor L being connected to the drain of the switch tube Q and the anode of the diode D, the cathode of the diode D and the source of the switch tube Q serving as the output end of the boost circuit, and the output capacitor C and the load R being connected in parallel across the output end of the boost circuit.

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