A micro-inverter circuit and a filter control method thereof

Abstract

The present application relates to a kind of micro inverter circuit and its filter control method, belong to circuit structure technical field.The micro inverter circuit includes sequentially connected input filter module, boost module and inverter unit, the number of input filter module and boost module is consistent with the number of DC power supply, each described input filter module includes common mode rejection unit and differential mode rejection unit, the common mode rejection unit is used to suppress common mode interference signal, the differential mode rejection unit is used to filter differential mode interference signal.EMI signal can be effectively suppressed by this, to ensure signal smooth, so that the EMC filter circuit and control method meet EMC requirements, can be widely applied to various micro inverter and other electronic products, ensure the safety of product, improve the service life of product.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit structure, in particular to the technical field of filter circuit, and more particularly to a micro inverter circuit and a filter control method thereof. BACKGROUND

[0002] EMC is electromagnetic compatibility, which means that an electronic device or network system has the ability to resist electromagnetic interference, and at the same time cannot produce excessive electromagnetic radiation. That is to say, the device or network system is required to work normally in a relatively harsh electromagnetic environment, while not radiating excessive electromagnetic waves to interfere with the normal work of other devices and networks around it.

[0003] In the field of micro inverter, when the power increases, the existing conventional filter device cannot meet the EMC requirement. In the process of direct current to alternating current conversion, the transistor works repeatedly in the cut-off and conduction state, which leads to the accumulation of di / dt and du / dt charges in the PN junction of the transistor. If these charges are not released in time, a loop and a space electromagnetic field wave will be formed, which will generate electromagnetic interference signals and affect the normal work of the entire inverter.

[0004] Therefore, how to provide an EMC filter circuit capable of effectively suppressing electromagnetic interference signals, releasing accumulated charges, and ensuring signal stability to meet the EMC requirement has become a problem to be solved in the field. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a micro inverter circuit and a filter control method thereof capable of effectively suppressing electromagnetic interference signals, releasing accumulated charges, and ensuring signal stability to meet the EMC requirement.

[0006] In order to achieve the above purpose, the micro inverter circuit of the present application has the following structure:

[0007] The micro inverter circuit comprises input filter modules, boost modules and inverter units connected in sequence, the input end of the input filter module is connected to a direct current power supply, and the output end of the inverter unit is connected to a power grid through a relay. The number of the input filter modules and the number of the boost modules are consistent with the number of the direct current power supply, each of the input filter modules comprises a common mode suppression unit and a differential mode suppression unit, the common mode suppression unit is used to suppress common mode interference signals, and the differential mode suppression unit is used to filter differential mode interference signals.

[0008] The common-mode suppression unit comprises a first common-mode inductor L1, a third capacitor C3, a fourth capacitor C4, and sixth to eleventh capacitors C6-C11. The primary side of the first common-mode inductor L1 is connected to the positive line, and the secondary side is connected to the negative line. The two coils of the first common-mode inductor L1 are co-directionally wound around the same winding and have the same number of turns. One end of the third capacitor C3 is connected to the positive line, and the other end is connected to the ground. One end of the fourth capacitor C4 is connected to the negative line, and the other end is connected to the ground. One end of each of the sixth to eleventh capacitors C6-C11 is connected to the positive line, and the other end is connected to the ground. The first common-mode inductor L1 is used to attenuate and suppress the common-mode interference signal, and the common-mode interference signal on the positive line and the negative line is discharged to the ground through the third capacitor C3, the fourth capacitor C4, and the sixth to eleventh capacitors C6-C11.

[0009] The differential-mode suppression unit comprises first, second, and fifth capacitors C1, C2, and C5, and the leakage inductance of the first common-mode inductor L1, which is used to form a low-pass filter with the leakage inductance and the fifth capacitor C5 to filter the differential-mode interference signal.

[0010] The present application also provides a filtering control method for the micro-inverter circuit, which comprises suppressing the common-mode interference signal using the common-mode suppression unit and filtering the differential-mode interference signal using the differential-mode suppression unit.

[0011] The micro-inverter circuit and the filtering control method thereof have a circuit comprising sequentially connected input filtering modules, boost modules, and inverter units. The number of input filtering modules and boost modules is consistent with the number of DC power sources. Each input filtering module comprises a common-mode suppression unit and a differential-mode suppression unit. The common-mode suppression unit is used to suppress the common-mode interference signal, and the differential-mode suppression unit is used to filter the differential-mode interference signal. This can effectively suppress electromagnetic interference signals, ensuring signal stability and meeting EMC requirements. The EMC filtering circuit and control method can be widely applied to various electronic products such as micro-inverters, ensuring product safety and improving product service life. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The structure block diagram of the micro-inverter circuit of the present application;

[0013] Figure 2 The circuit schematic diagram of the two-way input filtering module in the micro-inverter of the present application;

[0014] Figure 3a The signal schematic diagram of the micro-inverter without the input filtering module of the present application;

[0015] Figure 3b The signal diagram of the micro-inverter with the input filter module of the present application. DETAILED DESCRIPTION

[0016] In order to make the technical content of the present application more clearly understood, the following embodiments are described in detail.

[0017] The micro-inverter circuit comprises sequentially connected input filter module, boost module and inverter unit, the input end of the input filter module is connected with the DC power supply, the output end of the boost module is connected with the input end of the inverter unit through VH node, and the output end of the inverter unit is connected with the power grid through the protection device such as relay.

[0018] Please refer to Figure 1 The structural block diagram of the micro-inverter circuit of the present application.

[0019] The number of the input filter modules and the number of the boost modules are consistent with the number of the DC power supplies.

[0020] In an embodiment, as Figure 1 The micro-inverter circuit comprises two input filter modules and corresponding two boost modules. Each of the input filter modules comprises common mode rejection unit and differential mode rejection unit, the common mode rejection unit is used for rejecting common mode interference signal, and the differential mode rejection unit is used for filtering differential mode interference signal.

[0021] The present application also provides a filtering control method of the micro-inverter circuit, which comprises: rejecting common mode interference signal by using the common mode rejection unit; filtering differential mode interference signal by using the differential mode rejection unit.

[0022] In a preferred embodiment, taking the input filter module connected between PV1 node and the first boost module as an example. As Figure 2As shown, the common-mode rejection unit of the input filter module comprises a first common-mode inductor L1, a third capacitor C3, a fourth capacitor C4, a sixth to eleventh capacitor C6-C11. One side of the first common-mode inductor L1 is connected to the positive line, and the other side is connected to the negative line. The two coils of the first common-mode inductor L1 are co-directionally wound on the same winding and have the same number of turns. The inductance of each coil is about 100-470 μH. One end of the third capacitor C3 is connected to the positive line, and the other end is grounded. One end of the fourth capacitor C4 is connected to the negative line, and the other end is grounded. One end of the sixth to eleventh capacitor C6-C11 is connected to the positive line, and the other end is grounded. Since the transmission direction and size of the common-mode interference signal on the positive line and the negative line are the same, the magnetic fields generated by the two coils of the first common-mode inductor L1 on the positive line and the negative line are in the same direction, which shows a larger impedance, thereby attenuating and suppressing the common-mode interference signal on the positive line and the negative line, and discharging the common-mode interference signal on the positive line and the negative line to the ground through the third capacitor C3, the fourth capacitor C4, and the sixth to eleventh capacitor C6-C11.

[0023] The differential-mode rejection unit of the input filter module comprises a first, second, and fifth capacitor C1, C2, C5, and also comprises the leakage inductance of the first common-mode inductor L1, which is used to form a low-pass filter with the fifth capacitor C5 to filter the differential-mode interference signal.

[0024] In this embodiment, the structure of the input filter module connected between the PV2 node and the second boost module is the same as that connected to the PV1 node. Its common-mode rejection unit comprises a second common-mode inductor L2, a sixteenth capacitor C16, a seventeenth C17, and a nineteenth to twenty-fourth capacitor C19-C24. The two coils of the second common-mode inductor L2 are co-directionally wound on the same winding and have the same number of turns. The differential-mode rejection unit of the input filter module comprises a fourteenth, fifteenth, and eighteenth capacitor C14, C15, C18, and also comprises the leakage inductance of the second common-mode inductor L2. The specific connection mode and working mode of the input filter module connected to the PV2 node are the same as those connected to the PV1 node, and will not be described again.

[0025] In practical application, the first, second, fifth, fourteenth, fifteenth and eighteenth capacitors C1, C2, C5, C14, C15 and C18 are X capacitors; the capacitance of the first capacitor C1, the fifth capacitor C5, the fourteenth capacitor C14 and the eighteenth capacitor C18 is 0.1-0.22 mu F; the capacitance of the second capacitor C2 and the fifteenth capacitor C15 is 1-2.2 nF; the third, fourth, sixth to thirteenth, sixteenth, seventeenth and nineteenth to twenty-sixth capacitors C3, C4, C6-C13, C16, C17 and C19-C26 are Y capacitors, wherein the capacitance of the third capacitor C3, the fourth capacitor C4, the sixteenth capacitor C16 and the seventeenth capacitor C17 is 1-4.7 nF. Each of the first and second common mode inductors L1 and L2 is a manganese-zinc ferrite.

[0026] As shown in Figure 3a and 3b , respectively, are the signal diagrams of the micro-inverter without and with the input filter module of the application. In the case of increasing power of the photovoltaic inverter, the EMC is optimized. In the case of the same received signal, after the micro-inverter with the input filter module of the application, the output signal is more stable, and it can be seen that compared with the case without adding, the application can effectively suppress the influence of electromagnetic interference signals on the output signal, so as to meet the safety requirements and meet the electromagnetic compatibility of electronic products. The application can be widely applied to micro-inverters and other electronic products.

[0027] The micro-inverter circuit and its filtering control method adopt the application, the circuit includes sequentially connected input filter module, boost module and inverter unit, the number of input filter module and boost module is consistent with the number of DC power supply, each of the input filter module includes a common mode rejection unit and a differential mode rejection unit, the common mode rejection unit is used to suppress common mode interference signals, and the differential mode rejection unit is used to filter differential mode interference signals. Thus, electromagnetic interference signals can be effectively suppressed, thereby ensuring signal stability, so that the EMC filter circuit and control method meet the EMC requirements, and can be widely applied to various micro-inverters and other electronic products, ensuring the safety of the products and improving the service life of the products.

[0028] In this specification, the application has been described with reference to its specific embodiments. However, it is obvious that various modifications and changes can be made without departing from the spirit and scope of the application. Therefore, the specification and drawings should be considered as illustrative rather than limiting.

Claims

1. A micro inverter circuit, comprising an input filter module, a boost module, and an inverter unit connected in sequence, wherein the input terminal of the input filter module is connected to a DC power supply, and the output terminal of the inverter unit is connected to the power grid via a relay, characterized in that, The number of input filtering modules and the number of boost modules are consistent with the number of DC power supplies. Each input filtering module includes a common-mode rejection unit and a differential-mode rejection unit. The common-mode rejection unit is used to suppress common-mode interference signals, and the differential-mode rejection unit is used to filter differential-mode interference signals. The common-mode suppression unit includes a first common-mode inductor (L1), a third capacitor (C3), a fourth capacitor (C4), and sixth to eleventh capacitors (C6~C11). The primary winding of the first common-mode inductor (L1) is connected to the positive terminal, and its secondary winding is connected to the negative terminal. The two coils of the first common-mode inductor (L1) are wound in the same direction on the same winding and have the same number of turns; the inductance of each coil is 100~470μH. One end of the third capacitor (C3) is connected to the positive terminal, and the other end... Grounding; one end of the fourth capacitor (C4) is connected to the negative line, and the other end is grounded; one end of the sixth to eleventh capacitors (C6~C11) is connected to the positive line, and the other end is grounded; the first common-mode inductor (L1) is used to attenuate and suppress the common-mode interference signal, and discharges the common-mode interference signal on the positive and negative lines to the ground line through the third capacitor (C3), the fourth capacitor (C4), and the sixth to eleventh capacitors (C6~C11), respectively.

2. The micro inverter circuit according to claim 1, characterized in that, The differential mode suppression unit includes a first, a second, and a fifth capacitor (C1, C2, C5), and also includes the leakage inductance of the first common mode inductor (L1), which is used to form a low-pass filter with the fifth capacitor (C5) to filter the differential mode interference signal.

3. A filtering control method for a micro-inverter circuit, wherein the micro-inverter circuit comprises an input filter module, a boost module, and an inverter unit connected in sequence, the input terminal of the input filter module is connected to a DC power supply, and the output terminal of the inverter unit is connected to the power grid via a relay, characterized in that... The number of input filtering modules and the number of boost modules are consistent with the number of DC power supplies. Each input filtering module includes a common-mode rejection unit and a differential-mode rejection unit. The common-mode rejection unit includes a first common-mode inductor (L1), a third capacitor (C3), a fourth capacitor (C4), and sixth to eleventh capacitors (C6~C11). The primary side of the first common-mode inductor (L1) is connected to the positive line, and its secondary side is connected to the negative line. The two coils of the first common-mode inductor (L1) are wound in the same direction in the same winding and have the same number of turns. The inductance of each coil is 100~470μH. One end of the third capacitor (C3) is connected to the positive line, and the other end is grounded. One end of the fourth capacitor (C4) is connected to the negative line, and the other end is grounded. One end of the sixth to eleventh capacitors (C6~C11) is connected to the positive line, and their other ends are grounded. The method includes: The common-mode suppression unit is used to suppress the common-mode interference signal. The first common-mode inductor (L1) is used to attenuate and suppress the common-mode interference signal. The common-mode interference signal on the positive and negative lines is discharged to the ground line through the third capacitor (C3), the fourth capacitor (C4), and the sixth to eleventh capacitors (C6~C11), respectively. The differential mode suppression unit is used to filter the differential mode interference signal.

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