DC component detection circuit and inverter

Abstract

The utility model relates to a direct current component detection circuit and an inverter. The direct-current component detection circuit comprises a filtering module which is used for carrying out at least one attenuation filtering on a first alternating-current voltage signal in input voltage signals and outputting a second alternating-current voltage signal after differential attenuation and a first direct-current voltage component; wherein the input voltage signal comprises the first alternating-current voltage signal and a first direct-current voltage component superposed on the first alternating-current voltage signal, and the second alternating-current voltage signal is a millivolt-level sine wave. According to the invention, the direct-current component detection of the alternating-current signal can be realized, the direct-current voltage component is not attenuated, and the high precision of the direct-current component is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of inverters, in particular to a direct current component detection circuit and an inverter. BACKGROUND

[0002] The direct current component detection of an inverter is an important design parameter for the inverter, especially for a photovoltaic energy storage inverter, which needs to be a parallel operation device and the like.

[0003] In order to improve the performance level and enhance the stability of the power grid, reduce the parallel operation circulating current, the photovoltaic inverter device on the market generally needs to use a direct current component detection circuit to collect data and feed back to a DSP for loop control. Common direct current component detection of an inverter includes an RC passive low-pass filter, a multi-stage low-pass filter composed of an operational amplifier and an FIR digital filter.

[0004] The existing direct current component detection of an inverter has low suppression on a 50Hz alternating current signal, which is easy to cause the detected direct current component to contain alternating current signal noise. CONTENT OF THE INVENTION

[0005] Therefore, it is necessary to provide a direct current component detection circuit and an inverter which has strong attenuation and suppression ability on a 50Hz alternating current signal, has no attenuation on a direct current component, and can maintain high precision and high linearity under positive and negative 10mV and positive and negative 2V direct current components.

[0006] In a first aspect, a direct current component detection circuit is provided, which comprises:

[0007] A filtering module is configured to perform at least one attenuation filtering on a first alternating current voltage signal in an input voltage signal, and output a second alternating current voltage signal after differential attenuation and a first direct current voltage component in the input voltage signal; wherein the input voltage signal comprises the first alternating current voltage signal and the first direct current voltage component superimposed on the first alternating current voltage signal, and the second alternating current voltage signal is a millivolt-level sinusoidal wave.

[0008] In one of the embodiments, the filtering module comprises a capacitor C1 and a first-stage filtering module.

[0009] The capacitor C1 has one end connected to an input end of the first-stage filtering module and the other end connected to an output end of the first-stage filtering module, and is configured to isolate and output the first direct current voltage component in the input voltage signal; and input the first alternating current voltage signal into the first-stage filtering module.

[0010] The first-stage filtering module is configured to perform at least one attenuation filtering on the first alternating current voltage signal, and output the second alternating current voltage signal after differential attenuation.

[0011] In one of the embodiments, the first filtering module comprises an operational amplifier U1, a resistor R2 and a capacitor C2.

[0012] The inverting input terminal of the operational amplifier U1 is connected to one end of the capacitor C1, the non-inverting input terminal of the operational amplifier U1 is connected to a bias voltage, the output terminal of the operational amplifier U1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the other end of the capacitor C1.

[0013] In one of the embodiments, the filtering module further comprises a resistor R1 connected in series with the capacitor C1, for attenuating filtering the first alternating voltage signal, and outputting a third alternating voltage signal after attenuating filtering.

[0014] In one of the embodiments, the first filtering module is further configured to perform at least one attenuating filtering on the third alternating voltage signal, and output a fourth alternating voltage signal after differential attenuating filtering; the fourth alternating voltage signal is a millivolt-level sinusoidal wave.

[0015] In one of the embodiments, the direct current component detection circuit further comprises:

[0016] The sampling module is connected to the input terminal of the filtering module, for sampling and noise filtering an original voltage signal, and outputting an input voltage signal; the original voltage signal comprises an original alternating voltage signal, an original direct current voltage component superimposed on the original alternating voltage signal, and a high-frequency noise signal; the input voltage signal comprises a differential attenuated first alternating voltage signal and a first direct current voltage component.

[0017] In one of the embodiments, the sampling module comprises an operational amplifier U2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C3 and a capacitor C5.

[0018] The inverting input terminal of the operational amplifier U2 is connected to one end of the resistor R3, and the non-inverting input terminal of the operational amplifier U2 is connected to one end of the resistor R4; the other end of the resistor R3 is connected to a negative voltage of the original voltage signal; the other end of the resistor R4 is connected to a positive voltage of the original voltage signal; one end of the resistor R6 is connected to the non-inverting input terminal of the operational amplifier U2, and the other end of the resistor R6 is connected to a bias voltage; one end of the resistor R5 is connected to the inverting input terminal of the operational amplifier U2, and the other end of the resistor R5 is connected to the output terminal of the operational amplifier U2.

[0019] One end of the capacitor C3 is connected to one end of the resistor R4, and the other end of the capacitor C3 is connected to the bias voltage; one end of the capacitor C5 is connected to one end of the resistor R3, and the other end of the capacitor C5 is connected to the other end of the resistor R5.

[0020] In one embodiment, the sampling module further comprises a capacitor C4.

[0021] One end of the capacitor C4 is connected to the other end of the capacitor C3, and the other end of the capacitor C4 is connected to a common ground.

[0022] In one embodiment, the other end of the resistor R6 is connected to a bias voltage, and the positive input terminal of the operational amplifier U1 is connected to a bias voltage with the same magnitude.

[0023] In a second aspect, an inverter is provided, and the inverter comprises the direct current component detection circuit according to the first aspect.

[0024] In the direct current component detection circuit and the inverter, the first alternating current signal in the input voltage signal is attenuated at least once, and the second attenuated alternating current signal and the first direct current component in the input voltage signal are output; wherein the input voltage signal comprises the first alternating current signal and the first direct current component superimposed on the first alternating current signal, and the second alternating current signal is a millivolt-level sine wave, which realizes the direct current component detection function of the alternating current signal and does not attenuate the direct current component, thereby ensuring the high precision of the direct current component. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0026] Figure 1 The structural block diagram of the filtering module in one embodiment;

[0027] Figure 2 The circuit structural diagram of the filtering module in one embodiment;

[0028] Figure 3 Another circuit structural diagram of the filtering module in one embodiment;

[0029] Figure 4 The structural block diagram of the direct current component detection circuit in another embodiment;

[0030] Figure 5 The circuit structural diagram of the sampling module in one embodiment;

[0031] Figure 6 The circuit structural diagram of the sampling module in another embodiment. DETAILED DESCRIPTION

[0032] For the purpose of promoting an understanding of the application, the application will now be described in greater detail with reference to the relevant drawings. Embodiments of the application are illustrated in the drawings. However, the application can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Embodiments of the application are illustrated in the drawings, and described in detail below.

[0033] As described in the background, when detecting the direct current component of the inverter in the prior art, there is a problem that the attenuation of the alternating current signal is not high enough. The inventors have also found that the suppression of the alternating current signal by the existing inverter direct current component detection circuit is generally between -10 dB and 25 dB; the RC passive low-pass filter suppresses the 50 Hz low-frequency signal, often requiring a resistance of several hundred kilohms and a capacitance of several hundred microfarads, and the settling time is very slow. The multi-stage filter composed of operational amplifiers attenuates the alternating current and the direct current together, increasing the detection error of the direct current component. If the 50 Hz needs to be suppressed by more than 80 dB by the FIR filter provided by the DSP, it needs to be filtered by more than one hundred orders, which is easy to cause resource shortage.

[0034] Based on this, in an embodiment, a direct current component detection circuit is provided, which comprises a filtering module. The filtering module is configured to attenuate filter the first alternating voltage signal in the input voltage signal V OUT at least once, and output the second attenuated alternating voltage signal and the first direct current component DC_OUT in the input voltage signal.

[0035] The input voltage signal V OUT includes the first alternating voltage signal and the first direct current component superimposed on the first alternating voltage signal, and the second alternating voltage signal is a millivolt-level sinusoidal wave.

[0036] As shown in Figure 1 , the filtering module 10 comprises a capacitor C1 and a first-stage filtering module.

[0037] The capacitor C1 has one end connected to the input end of the first-stage filtering module and the other end connected to the output end of the first-stage filtering module, and is configured to isolate and output the first direct current component in the input voltage signal; and input the first alternating voltage signal into the first-stage filtering module.

[0038] The first-stage filtering module is configured to attenuate filter the first alternating voltage signal at least once, and output the second attenuated alternating voltage signal.

[0039] As shown in Figure 2As shown, the first filtering module includes an operational amplifier U1, a resistor R2 and a capacitor C2. The inverting input terminal of the operational amplifier U1 is connected to one end of the capacitor C1, the non-inverting input terminal of the operational amplifier U1 is connected to a bias voltage, and the output terminal of the operational amplifier U1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the other end of the capacitor C1.

[0040] In detail, when the input voltage signal V OUT When passing through the capacitor C1, only the first alternating voltage signal is allowed to pass, and the first direct current voltage component is isolated and output to the output terminal of the first filtering module. After the first alternating voltage signal passes through the capacitor C1, it enters the first filtering module, and the operational amplifier U1 and the resistor R2 form a negative feedback circuit to attenuate the first alternating voltage signal at least once. In addition, the attenuated first alternating voltage signal takes the bias voltage as the reference potential, and then passes through the capacitor C2 to feedback to the input terminal of the capacitor C1 for filtering again, and finally outputs a millivolt-level second alternating voltage signal through the capacitor C2.

[0041] It should be noted that the direct current signal of the operational amplifier U1 itself cannot flow out through the capacitor C2, and therefore the final isolated output first direct current voltage component is completely determined by the input voltage signal.

[0042] In this embodiment, the first alternating voltage signal passes through the capacitor C1, the resistor R2 and the capacitor C2 for once coupling and attenuation filtering, and is feedback controlled by the operational amplifier U1. The R2 and C2 capacitors serve as a feedback loop, and the direct current voltage component cannot pass through the capacitor, thereby realizing the direct current component detection function of the alternating signal and having no attenuation to the direct current.

[0043] In one of the embodiments, as Figure 3 shown, the filtering module further includes a resistor R1 connected in series with the capacitor C1, for attenuating and filtering the first alternating voltage signal to output a third alternating voltage signal after attenuation and filtering.

[0044] The first filtering module is further configured to attenuate and filter the third alternating voltage signal at least once to output a fourth alternating voltage signal after differential attenuation; and the fourth alternating voltage signal is a millivolt-level sinusoidal wave.

[0045] In detail, the first alternating voltage signal of the input voltage signal V OUT is attenuated and filtered once by the resistor R1 and the capacitor C1, and the filtering frequency , obtain a third alternating voltage signal after low-pass filtering. The capacitor C1 inputs the third alternating voltage signal into the first filtering module 10, and the first filtering module 10 performs attenuation filtering on the third alternating voltage signal again to output a fourth alternating voltage signal after differential attenuation; the fourth alternating voltage signal is a millivolt-level sinusoidal wave.

[0046] In the embodiment, the first alternating voltage signal is coupled and attenuated twice through the resistor R1, the capacitor C1, the resistor R2 and the capacitor C2, which has a strong attenuation and inhibition capability for 50Hz alternating current and no attenuation for direct current. Moreover, high precision and high linearity can be maintained under positive and negative 10mV and positive and negative 2V direct current components.

[0047] As shown in Figure 4 In one of the embodiments, the direct current component detection circuit further comprises a sampling module 20. The sampling module is connected with the input end of the filtering module, and is configured to sample and filter noise of an original voltage signal to output an input voltage signal; the original voltage signal comprises an original alternating voltage signal, an original direct current voltage component superimposed on the original alternating voltage signal and a high-frequency noise signal; and the input voltage signal comprises a first alternating voltage signal after differential attenuation and a first direct current voltage component.

[0048] As shown in Figure 5 The sampling module 20 comprises an operational amplifier U2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C3 and a capacitor C5.

[0049] One end of the resistor R3 is connected with the inverting input end of the operational amplifier U2, and one end of the resistor R4 is connected with the non-inverting input end of the operational amplifier U2; the other end of the resistor R3 is connected with the negative voltage V- of the original voltage signal, and the other end of the resistor R4 is connected with the positive voltage V+ of the original voltage signal; one end of the resistor R6 is connected with the non-inverting input end of the operational amplifier U2, and the other end of the resistor R6 is connected with a bias voltage Vref; one end of the resistor R5 is connected with the inverting input end of the operational amplifier U2, and the other end of the resistor R5 is connected with the output end of the operational amplifier U2. One end of the capacitor C3 is connected with one end of the resistor R4, and the other end of the capacitor C3 is connected with the bias voltage Vref; one end of the capacitor C5 is connected with one end of the resistor R3, and the other end of the capacitor C5 is connected with the other end of the resistor R5.

[0050] In detail, the input voltage signal is obtained after sampling of an external original voltage signal. The original voltage signal comprises an original alternating voltage signal, an original direct current voltage component superimposed on the original alternating voltage signal and a high-frequency noise signal, so that attenuation sampling and noise filtering of the original voltage signal are required.

[0051] The original voltage signal from outside is provided by an external power supply, and a differential attenuation circuit of a sampling module 20 composed of resistors R3, R4, R5, R6 and an operational amplifier U2, wherein R3=R4, R5=R6. When there is no signal input, the output of the operational amplifier U2 is a bias voltage amplitude, and when the original voltage signal is input, the output is the input voltage signal V OUT is:

[0052]

[0053] wherein Vref is the bias voltage.

[0054] And the high-frequency noise signal is filtered out after passing through a noise filtering loop composed of resistor R5, capacitor C5 and resistor R6, capacitor C3, wherein C3=C5, and the noise filtering cutoff frequency is .

[0055] In one embodiment, as shown in Figure 6 the sampling module further comprises a capacitor C4. One end of the capacitor C4 is connected to the other end of the capacitor C3, and the other end of the capacitor C4 is connected to the common ground. The size of the capacitor C4 is 0.1uf, which is used to filter the bias voltage.

[0056] In one embodiment, a kind of inverter is provided, and the direct current component detection circuit described in the above embodiments is included in the inverter.

[0057] In the description of the specification, the description of the terms "some embodiments", "other embodiments" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In the description of the specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terms used in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0059] It can be understood that the terms "first", "second" and the like used in the present application can be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element. For example, without departing from the scope of the present application, the first resistor can be called the second resistor, and similarly, the second resistor can be called the first resistor. The first resistor and the second resistor are both resistors, but they are not the same resistor. ​

[0060] It can be understood that the "connection" in the above embodiments should be understood as "electrical connection", "communication connection" and the like if the circuits, modules, units and the like connected have transmission of electrical signals or data between each other.

[0061] It can be understood that "at least one" means one or more, and "multiple" means two or more. "At least part of the element" means part or all of the element.

[0062] As used herein, the singular forms "a", "an" and "the" include plural referents unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", or "has" and / or "having", as used herein, specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof.

[0063] The technical features of the above-described embodiments can be combined in any manner. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not contradict each other, they should be considered within the scope of the present disclosure.

[0064] The above-described embodiments only express several implementation manners of the present application, and the description is specific and detailed, but it should not be understood as a limitation on the scope of the present application. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A direct current component detection circuit, characterized by comprising: The direct current component detection circuit comprises: The filter module is configured to perform at least one attenuation filtering on the first alternating current voltage signal in the input voltage signal, and output a second alternating current voltage signal after differential attenuation and a first direct current voltage component; wherein the input voltage signal comprises the first alternating current voltage signal and the first direct current voltage component superimposed on the first alternating current voltage signal, and the second alternating current voltage signal is a millivolt-level sinusoidal wave.

2. The direct current component detection circuit according to claim 1, characterized in that The filter module comprises a capacitor C1 and a first-level filter module. One end of the capacitor C1 is connected to an input end of the first-level filter module, and the other end of the capacitor C1 is connected to an output end of the first-level filter module, so as to isolate and output the first direct current voltage component in the input voltage signal; and the first alternating current voltage signal is input into the first-level filter module. The first-level filter module is configured to perform at least one attenuation filtering on the first alternating current voltage signal, and output a second alternating current voltage signal after differential attenuation.

3. The direct current component detection circuit according to claim 2, characterized in that The first-level filter module comprises an operational amplifier U1, a resistor R2 and a capacitor C2. An inverting input end of the operational amplifier U1 is connected to one end of the capacitor C1, a non-inverting input end of the operational amplifier U1 is connected to a bias voltage, an output end of the operational amplifier U1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is connected to the other end of the capacitor C1.

4. The direct current component detection circuit according to claim 3, characterized in that The filter module further comprises a resistor R1 connected in series with the capacitor C1, configured to perform attenuation filtering on the first alternating current voltage signal, and output a third alternating current voltage signal after attenuation filtering.

5. The direct current component detection circuit according to claim 4, characterized in that The first-level filter module is further configured to perform at least one attenuation filtering on the third alternating current voltage signal, and output a fourth alternating current voltage signal after differential attenuation; and the fourth alternating current voltage signal is a millivolt-level sinusoidal wave.

6. The direct current component detection circuit according to claim 5, characterized in that The direct current component detection circuit further comprises: A sampling module connected to an input end of the filter module, configured to sample and noise-filter an original voltage signal, and output the input voltage signal; wherein the original voltage signal comprises an original alternating current voltage signal, an original direct current voltage component superimposed on the original alternating current voltage signal and a high-frequency noise signal; and the input voltage signal comprises the first alternating current voltage signal after differential attenuation and the first direct current voltage component.

7. The direct current component detection circuit according to claim 6, characterized in that The sampling module comprises an operational amplifier U2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a capacitor C3 and a capacitor C5. An inverting input end of the operational amplifier U2 is connected to one end of the resistor R3, and a non-inverting input end of the operational amplifier U2 is connected to one end of the resistor R4; the other end of the resistor R3 is connected to a negative voltage of the original voltage signal; the other end of the resistor R4 is connected to a positive voltage of the original voltage signal; one end of the resistor R6 is connected to the non-inverting input end of the operational amplifier U2, and the other end of the resistor R6 is connected to a bias voltage; one end of the resistor R5 is connected to the inverting input end of the operational amplifier U2, and the other end of the resistor R5 is connected to an output end of the operational amplifier U2. One end of the capacitor C3 is connected to one end of the resistor R4, and the other end of the capacitor C3 is connected to the bias voltage; one end of the capacitor C5 is connected to one end of the resistor R3, and the other end of the capacitor C5 is connected to the other end of the resistor R5.

8. The direct current component detection circuit according to claim 7, characterized in that The sampling module further comprises a capacitor C4. One end of the capacitor C4 is connected to the other end of the capacitor C3, and the other end of the capacitor C4 is connected to the common ground.

9. The direct current component detection circuit of claim 7, wherein, The other end of the resistor R6 is connected to the bias voltage, and the non-inverting input terminal of the operational amplifier U1 is connected to the bias voltage with the same magnitude.

10. An inverter, characterized by comprising: The direct current component detection circuit comprises the direct current component detection circuit according to any one of claims 1-9.

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