An inverter circuit structure

Abstract

The utility model relates to the technical field of photovoltaic power supply discloses an inverter circuit structure for photovoltaic power supply, including voltage sampling branch, boost branch, zero offset calibration branch, bus capacitor branch and inverter body that are set gradually in photovoltaic module and power grid between, voltage sampling branch, zero offset calibration branch all are linked with the controller of inverter self, voltage sampling branch is used for detecting the voltage information of photovoltaic module output end, zero offset calibration branch is used for discharging the capacitor in bus capacitor branch until 0V.

Description

Technical Field

[0001] This utility model belongs to the technical field of photovoltaic power supply, specifically relating to an inverter circuit structure. Background Technology

[0002] In practical applications of photovoltaic inverters, voltage sampling circuits are often installed inside the inverters to sample the DC voltage at the inverter input terminal. The obtained sampled values ​​are used for system control and metering display.

[0003] Inverter bus voltage sampling includes positive bus voltage sampling and negative bus voltage sampling. The sampling accuracy is crucial, as the error directly affects the DC component of the subsequent output voltage, leading to abnormal load conditions in downstream stages. Existing voltage sampling schemes mostly employ high-impedance differential sampling. The errors in this method include manufacturing errors in the resistors themselves, operational amplifier deviations, and DSP detection deviations, among others. These errors are closely related to temperature and lifespan, and the largest contributing factor is the zero-bias error. Therefore, a practical solution to eliminate zero-bias error is urgently needed to meet the requirements of real-world applications. Utility Model Content

[0004] To address the aforementioned technical problems, this utility model provides an inverter circuit structure that solves the technical issues of inaccurate subsequent sampling caused by the large zero-bias error in existing bus voltage sampling.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An inverter circuit structure for photovoltaic power supply includes a voltage sampling branch, a boost branch, a zero-bias calibration branch, a bus capacitor branch, and an inverter body, which are sequentially connected in parallel between the photovoltaic module and the power grid. The voltage sampling branch and the zero-bias calibration branch are both connected to the inverter's own controller. The voltage sampling branch is used to detect the voltage information at the output terminal of the photovoltaic module, and the zero-bias calibration branch is used to discharge the capacitor in the bus capacitor branch until it reaches 0V.

[0006] Furthermore, the zero-bias calibration branch includes a controllable switch body and a resistor connected in series. The control terminal of the controllable switch is connected to a controller, and the controller is also connected to the output terminal of a first comparator. The negative terminal of the first comparator is connected to a voltage sampling circuit, and the positive terminal is connected to a reference voltage.

[0007] Furthermore, the voltage sampling branch includes a second comparator, the output terminal of the second comparator is connected to the negative input terminal of the first comparator, and its positive input terminal and negative input terminal are respectively connected to the positive and negative terminals of the photovoltaic module through their respective sampling resistors. A feedback resistor is connected between the output terminal and the negative input terminal of the second comparator.

[0008] Furthermore, a calibration enable terminal is provided, and the calibration enable terminal and the output terminal of the first comparator are connected to the controller via an AND gate.

[0009] Furthermore, the boost branch adopts a BOOST boost branch, and when the zero bias calibration branch is in working state, the IGBT in the boost branch is in the conducting state.

[0010] Furthermore, the bus capacitor branch includes one bus capacitor or multiple bus capacitors connected in series.

[0011] Compared with the prior art, the beneficial effects of this utility model are: (1) The inverter’s own controller obtains the voltage information of the output terminal of the photovoltaic module according to the voltage sampling branch, and controls the zero bias calibration branch to discharge the capacitor in the bus capacitor branch, so as to safely reduce the bus voltage to 0V, realize the zero bias calibration of the bus voltage sampling, ensure the accuracy of subsequent bus voltage sampling, provide accurate data basis for subsequent grid voltage distribution, effectively avoid load power supply abnormalities, and is highly practical and easy to promote and apply.

[0012] (2) By cleverly using a controllable switch to control the connection or disconnection of the resistor, the capacitor in the bus capacitor branch is discharged until 0V, thereby achieving zero bias calibration of the bus voltage sampling. Its circuit structure is simple, reliable and highly operable. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the circuit structure of this utility model. Figure 1 One bus capacitor is provided. Figure 2 This is a schematic diagram of the circuit structure of this utility model. Figure 2 Two bus capacitors are provided. Figure 3 This is a schematic diagram of the circuit structure of the zero-bias calibration branch of this utility model. Detailed Implementation To make the technical means, creative features, objectives and effects of this utility model easier to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the inverter circuit structure of this utility model. It should be noted that the description of these embodiments is for the purpose of helping to understand this utility model, but does not constitute a limitation on this utility model.

[0014] like Figures 1-3As shown, this utility model provides an inverter circuit structure for photovoltaic power supply, including a voltage sampling branch, a boost branch, a zero-bias calibration branch, a bus capacitor branch, and the inverter body, which are sequentially connected in parallel between the photovoltaic module and the power grid. The voltage sampling branch and the zero-bias calibration branch are both connected to the inverter's own controller. The voltage sampling branch is used to detect the voltage information at the output terminal of the photovoltaic module, and the zero-bias calibration branch is used to discharge the capacitors in the bus capacitor branch until they reach 0V. In this way, the inverter's own controller, based on the voltage information obtained from the photovoltaic module's output terminal through the voltage sampling branch, controls the zero-bias calibration branch to discharge the capacitors in the bus capacitor branch, thereby safely reducing the bus voltage to 0V, achieving zero-bias calibration of the bus voltage sampling, ensuring the accuracy of subsequent bus voltage sampling, providing an accurate data basis for subsequent grid voltage distribution, effectively avoiding abnormal load power supply, and demonstrating strong practicality and ease of widespread application.

[0015] Specifically as follows: A voltage sampling branch, a boost branch, a zero-bias calibration branch, a bus capacitor branch, and an inverter body are connected in parallel between the photovoltaic module and the grid. The inverter body, composed of bridge arms, performs the inversion operation. The zero-bias calibration branch discharges the capacitors in the bus capacitor branch to 0V and includes a controllable switch body and a resistor connected in series. The control terminal of the controllable switch is connected to a controller, which is also connected to the output of a first comparator. The negative terminal of the first comparator is connected to the voltage sampling circuit, and the positive terminal is connected to the reference voltage. Of course, the controllable switch can be an electromagnetic switch or a semiconductor switch, such as a MOSFET or IGBT. The voltage sampling branch is used to detect the voltage information at both ends of the photovoltaic module. It includes a second comparator, the output of which is connected to the negative input of the first comparator. Its positive and negative inputs are respectively connected to the positive and negative terminals of the photovoltaic module through their respective sampling resistors. A feedback resistor is connected between the output of the second comparator and the negative input.

[0016] In addition, the bus capacitor branch includes a bus capacitor or multiple bus capacitors connected in series. The BOOST boost branch includes an inductor L1, a diode D1 connected in series, and an IGBTS1 connected in parallel. Of course, IGBTS1 can also be replaced by other controllable switches, such as MOSEFT.

[0017] The voltage information detected by the voltage sampling branch is compared with the reference voltage. If it is lower than the reference voltage, the output of the first comparator is at a high level. The controller receives the high-level signal and controls the controllable switch K1 to conduct through the control terminal of the controllable switch K1, thereby connecting the resistor to the circuit and forming a closed loop with the bus capacitor branch. This allows the capacitor in the bus capacitor branch to discharge through the resistor until it reaches 0V, achieving zero bias calibration and ensuring the accuracy of subsequent voltage sampling. If the voltage is higher than the reference voltage, the output terminal of the first comparison is at a low level. The controller receives the low-level signal and will not send a conduction signal to the control terminal of the controllable switch K1. Therefore, the controllable switch K1 is always in the open state and will not discharge the capacitor in the bus capacitor branch.

[0018] To ensure rapid discharge processing, during zero-bias calibration, the controller can first send a control signal to the BOOST boost branch to turn on IGBTS1, short-circuiting the photovoltaic module and cutting off the power supply path from the photovoltaic module to the bus capacitor branch, preventing the capacitor voltage from rising. This allows the capacitor to discharge rapidly through the zero-bias calibration branch, which helps to perform zero-bias calibration of the photovoltaic module voltage sampling.

[0019] To standardize the inverter's workflow, a calibration mode and a normal operation mode can be set. At the same time, a calibration enable terminal is constructed. The output signals of the first comparator and the calibration enable terminal of the controller need to be ANDed to generate the final control signal, which is used to control the conduction and disconnection of the controllable switch K1. That is, when the controller is in calibration mode, the calibration enable terminal is set to a high level. Therefore, only when the output signal of the first comparator is high will the final control signal be high, which can control the controllable switch K1 to conduct. When the controller is in normal operation, the calibration enable terminal is set to low level. This means that regardless of whether the output signal of the first comparator is high level, the final control signal is always low level, and the controllable switch K1 cannot be turned on. This effectively avoids false triggering and ensures the normal operation of the inverter.

[0020] The calibration enable terminal can be constructed using a power supply and a manual switch. When the controller is in calibration mode, the switch is closed, and the voltage of the power supply is used as the high level of the calibration enable terminal. When the controller is in normal operation mode, the switch is opened, grounding the calibration enable terminal to a low level. Of course, the calibration enable terminal can also be connected to the controller, which detects the level of the port to complete subsequent control.

[0021] It is important to note that the schemes and arrangements of this application shown in the exemplary embodiments are merely exemplary. Although only a few embodiments are described in detail in this disclosure, those who consult this disclosure will readily understand that many modifications are possible (e.g., variations in various parameter values ​​(temperature, power, humidity, etc.), installation arrangements, names, colors, logical orders, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in this application. Therefore, all such modifications are also included within the scope of the invention, and the order or sequence of any process or method steps may be changed or rearranged according to alternative embodiments. In the claims, any "apparatus plus function" clause is intended to cover the structure described herein for performing the function, and not only structurally equivalent but also equivalent in structure. Other substitutions, modifications, alterations, and omissions may be made in the design, operation, and arrangement of the exemplary embodiments without departing from the scope of the invention. Therefore, the invention is not limited to the particular embodiments but extends to a variety of modifications that still fall within the scope of the appended claims.

[0022] Furthermore, in order to provide a concise description of exemplary embodiments, not all features of actual embodiments (i.e., those features that are not relevant to the best mode of carrying out the invention as currently considered, or those features that are not relevant to implementing the invention) may be omitted.

[0023] It should be understood that numerous specific implementation decisions can be made during the development of any practical implementation, such as in any engineering or design project. Such development efforts may be complex and time-consuming, but for those skilled in the art who benefit from this disclosure, the development effort will be a routine work of design, manufacturing, and production without requiring much experimentation.

[0024] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An inverter circuit structure, characterized in that: For photovoltaic power supply, it includes a voltage sampling branch, a boost branch, a zero-bias calibration branch, a bus capacitor branch, and an inverter body arranged in parallel between the photovoltaic module and the grid. The voltage sampling branch and the zero-bias calibration branch are both connected to the inverter's own controller. The voltage sampling branch is used to detect the voltage information at the output terminal of the photovoltaic module, and the zero-bias calibration branch is used to discharge the capacitor in the bus capacitor branch until 0V.

2. The inverter circuit structure according to claim 1, characterized in that: The zero-bias calibration branch includes a controllable switch body and a resistor connected in series. The control terminal of the controllable switch is connected to a controller. The controller is also connected to the output terminal of a first comparator. The negative terminal of the first comparator is connected to a voltage sampling circuit, and the positive terminal is connected to a reference voltage.

3. The inverter circuit structure according to claim 2, characterized in that: The voltage sampling branch includes a second comparator. The output terminal of the second comparator is connected to the negative terminal of the first comparator. Its positive and negative terminals are respectively connected to the positive and negative terminals of the photovoltaic module through their respective sampling resistors. A feedback resistor is connected between the output terminal and the negative terminal of the second comparator.

4. The inverter circuit structure according to claim 2, characterized in that: A calibration enable terminal is provided, and the calibration enable terminal and the output terminal of the first comparator are connected to the controller via an AND gate.

5. The inverter circuit structure according to claim 1, characterized in that: The boost branch adopts the BOOST boost branch. When the zero bias calibration branch is in working state, the IGBT in the boost branch is in the conducting state.

6. The inverter circuit structure according to claim 1, characterized in that: The bus capacitor branch includes one bus capacitor or multiple bus capacitors connected in series.

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