DC component detection circuit and photovoltaic inverter system

Abstract

The utility model discloses a DC component detection circuit and a photovoltaic inverter system. The DC component detection circuit comprises a differential filtering amplification module and a bias module. The differential filtering and amplifying module comprises a main operational amplifier, and the inverted input end of the main operational amplifier corresponds to the first power line. The input end of the bias module is connected with the first power line, the bias module comprises an inverted output end, and the inverted output end of the bias module is electrically connected with the inverted input end of the main operational amplifier. And the bias module is used for performing low-pass filtering and inverse-phase amplification on the signal on the first power line and then outputting the signal through an inverse-phase output end of the bias module. According to the utility model, the influence of common-mode voltage on the operational amplifier is reduced, and the sampling precision is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaic inverters, in particular to a direct current component detection circuit and a photovoltaic inverter system. Background Art

[0002] When the photovoltaic storage inverter works in the inverter off-grid mode, the output DC component needs to be controlled within a certain value to meet the needs of parallel operation or transformer load. When the existing technology controls the DC component, it generally uses a high-impedance differential circuit to reduce the output AC power by multiples and then directly uses an RC filter circuit to filter out the DC component. The DC component filtered out by this setting is small, and the detection of the DC component is difficult, resulting in large test errors. If the DC signal is amplified directly, although a large DC value can be retained, a large common-mode voltage will be generated, which has high requirements on the common-mode rejection ratio and supply voltage amplitude of the operational amplifier, and has a greater impact on the operational amplifier. Utility Model Content

[0003] The utility model provides a direct current component detection circuit and a photovoltaic inverter system, so as to reduce the influence of common mode voltage on an operational amplifier and improve sampling accuracy.

[0004] According to one aspect of the utility model, a DC component detection circuit is provided, the DC component detection circuit comprising:

[0005] Differential filter amplifier module and bias module;

[0006] The differential filter amplification module comprises a main operational amplifier, and an inverting input terminal of the main operational amplifier is electrically connected to the first power line;

[0007] The input end of the bias module is connected to the first power line, the bias module includes an inverting output end, the inverting output end of the bias module is electrically connected to the inverting input end of the main operational amplifier, the bias module is used to low-pass filter and invert the signal on the first power line and then output it from the inverting output end of the bias module, and the bias module is used to reduce the common mode voltage input to the main operational amplifier.

[0008] Optionally, the differential filter amplification module includes a first low-pass filter unit, which is connected between the first power line and the inverting input terminal of the main operational amplifier; the bias module includes a second low-pass filter unit, which has the same time constant as the first low-pass filter unit.

[0009] Optionally, the bias module includes a first resistor, a second resistor, a first capacitor and a bias operational amplifier;

[0010] The first resistor is connected between the input end of the bias module and the inverting input end of the bias operational amplifier, and the second resistor and the first capacitor are connected in parallel and then connected between the inverting input end of the bias operational amplifier and the output end of the bias operational amplifier;

[0011] The first capacitor and the first resistor constitute the second low-pass filtering unit.

[0012] Optionally, the differential filtering and amplifying module includes: a third resistor, a fourth resistor, a fifth resistor and a second capacitor;

[0013] The third resistor and the fourth resistor are connected in series between the inverting input terminal of the main operational amplifier and the first power line;

[0014] The fifth resistor is connected in series between the inverting output terminal of the bias module and the inverting input terminal of the main operational amplifier;

[0015] The third resistor and the second capacitor constitute the first low-pass filter unit, and the first low-pass filter unit is used to filter out the AC signal input to the inverting input terminal of the main operational amplifier.

[0016] Optionally, the amplification factor of the bias module is: A×K1,

[0017] in, A∈[-1,0), R5 is the resistance value of the fifth resistor, R3 is the resistance value of the third resistor, and R4 is the resistance value of the fourth resistor.

[0018] Optionally, the differential filtering and amplifying module further includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a third capacitor, a fourth capacitor and a fifth capacitor; the sixth resistor and the seventh resistor are connected in series between the non-inverting input terminal of the main operational amplifier and the second power line;

[0019] The eighth resistor is connected in series between the inverting output terminal of the bias module and the non-inverting input terminal of the main operational amplifier;

[0020] One end of the tenth resistor and the fifth capacitor is connected to the non-inverting input terminal of the main operational amplifier, and the other end is grounded; one end of the ninth resistor and the fourth capacitor is connected to the inverting input terminal of the main operational amplifier, and the other end is connected to the output terminal of the main operational amplifier.

[0021] Optionally, the differential filtering and amplifying module also includes a first follower unit, and the fifth resistor is connected to the inverting input terminal of the main operational amplifier through the first follower unit, and the first follower unit is used to ensure the integrity of the signal input to the inverting input terminal of the main operational amplifier.

[0022] Optionally, the differential filtering and amplifying module also includes a second follower unit, and the eighth resistor is connected to the non-inverting input terminal of the main operational amplifier through the second follower unit, and the second follower unit is used to ensure the integrity of the signal input to the non-inverting input terminal of the main operational amplifier.

[0023] Optionally, the bias module includes a common-direction amplification unit and a reverse-direction amplification unit; a non-phase input terminal of the common-direction amplification unit is connected to the first power line, and an output terminal of the common-direction amplification unit is connected to an inverting input terminal of the reverse-direction amplification unit;

[0024] The differential filtering and amplifying module further includes an adder; the output end of the main operational amplifier is connected to the inverting input end of the adder, and the output end of the in-phase amplifying unit is connected to the inverting input end of the adder.

[0025] According to another aspect of the utility model, a photovoltaic inverter system is provided, comprising a photovoltaic inverter and a DC component detection circuit as described in any of the above embodiments; the output end of the photovoltaic inverter is connected to the first power line.

[0026] The DC component detection circuit provided by the embodiment of the utility model is provided with a differential filter amplifier module and a bias module, so that the bias module can generate a bias voltage to offset the common-mode voltage through the common-mode voltage generated by the differential filter amplifier module, thereby reducing the influence of the common-mode voltage on the main operational amplifier and the error in the DC component data collection, thereby being able to more accurately collect DC component data and improving sampling accuracy.

[0027] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present utility model, nor are they intended to limit the scope of the present utility model. Other features of the present utility model will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0029] Figure 1 A DC component detection circuit is provided according to an embodiment of the utility model;

[0030] Figure 2 Another DC component detection circuit provided according to an embodiment of the utility model;

[0031] Figure 3 It is another DC component detection circuit provided according to an embodiment of the utility model;

[0032] Figure 4 Another DC component detection circuit is provided according to an embodiment of the utility model. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the solution of the utility model, the technical solution in the embodiment of the utility model will be clearly and completely described below in conjunction with the drawings in the embodiment of the utility model. Obviously, the described embodiment is only a part of the embodiment of the utility model, not all of the embodiments. Based on the embodiment of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the utility model.

[0034] It should be noted that the terms "first", "second", etc. in the specification and claims of the utility model and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the utility model described here can be implemented in an order other than those illustrated or described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] The utility model embodiment provides a DC component detection circuit, Figure 1 A circuit diagram of a DC component detection circuit provided by an embodiment of the utility model. Figure 1 , the circuit includes: a differential filter amplifier module 2 and a bias module 1. The differential filter amplifier module 2 includes a main operational amplifier 21, and the inverting input terminal of the main operational amplifier 21 is electrically connected to the first power line N. The input terminal of the bias module 1 is connected to the first power line N, and the bias module 1 includes an inverting output terminal A, and the inverting output terminal A is electrically connected to the inverting input terminal B of the main operational amplifier 21. The bias module 1 is used to low-pass filter and invert the signal on the first power line N and then output it from the inverting output terminal A of the bias module 1. The bias module 1 is used to reduce the common mode voltage input to the main operational amplifier 21.

[0036] Specifically, the differential filter amplifier module 2 can receive the electrical signal input from the first power line N, retain the DC component and input the DC component to the inverting input terminal of the main operational amplifier 21, and output it from the output terminal D of the main operational amplifier 21. In this process, the differential filter amplifier module 2 will generate a common-mode voltage. The main operational amplifier 21 has a certain tolerance value for the common-mode voltage. When the common-mode voltage is too large, it will exceed the tolerance range of the main operational amplifier 21, resulting in inaccurate test data and even damage to the main operational amplifier 21. By setting the bias module 1, the bias module 1 can generate an inverted bias voltage to offset the common-mode voltage generated by the differential filter amplifier module 2. After the bias module 1 filters the AC signal, the bias voltage is output to the differential filter amplifier module 2 through the inverting output terminal A of the bias module 1, thereby offsetting the common-mode voltage and making the DC signal input to the inverting input terminal of the main operational amplifier 21 purer.

[0037] The DC component detection circuit provided by the embodiment of the utility model is provided with a differential filter amplifier module 2 and a bias module 1, so that the bias module 1 can generate a bias voltage to offset the common-mode voltage through the common-mode voltage generated by the differential filter amplifier module 2, thereby reducing the influence of the common-mode voltage on the main operational amplifier 21 and the error in the DC component data collection, thereby being able to more accurately collect DC component data and improving sampling accuracy.

[0038] Figure 2 A circuit diagram of another DC component detection circuit provided by an embodiment of the utility model, referring to Figure 2 On the basis of the above embodiments, optionally, the differential filter amplification module 2 includes a first low-pass filter unit 22, and the first low-pass filter unit 22 is connected between the first power line N and the inverting input terminal B of the main operational amplifier 21; the bias module 1 includes a second low-pass filter unit 11, and the time constant of the second low-pass filter unit 11 is the same as that of the first low-pass filter unit 22.

[0039] Specifically, the first low-pass filter unit 22 is used to filter out the AC signal of the inverting input terminal B of the main operational amplifier 21 input by the first power line N in the differential filter amplification module 2, and the second low-pass filter unit 11 is used to filter out the AC component in the bias module 1. By setting the time constant of the second low-pass filter unit 11 and the first low-pass filter unit 22 to the same value, the second low-pass filter unit 11 and the first low-pass filter unit 22 can filter out high-frequency components of the same amplitude, so that the second low-pass filter unit 11 and the first low-pass filter unit 22 can both provide DC signals of the same quality, thereby ensuring the consistency of the signal input to the inverting input terminal B of the main operational amplifier 21.

[0040] Continue to refer Figure 2On the basis of the above embodiments, optionally, the bias module 1 includes a first resistor R1, a second resistor R2, a first capacitor C1 and a bias operational amplifier 12. The first resistor R1 is connected between the input end of the bias module 1 and the inverting input end of the bias operational amplifier 12, and the second resistor R2 and the first capacitor C1 are connected in parallel between the inverting input end of the bias operational amplifier 12 and the output end of the bias operational amplifier 12. The first capacitor C1 and the first resistor R1 constitute a second low-pass filter unit 11.

[0041] Specifically, the AC signal in the bias module 1 can be filtered out by the second low-pass filter unit 11, and the bias operational amplifier 12 can be adaptively adjusted according to the common-mode voltage generated by the differential filter amplifier module 2 to control the bias voltage output by the bias module 1 to achieve the offset of the common-mode voltage. When the common-mode voltage is large, the bias operational amplifier 12 has greater power and outputs a larger bias voltage; when the common-mode voltage is small, the bias operational amplifier 12 has less power and outputs a smaller bias voltage.

[0042] Continue to refer Figure 2 On the basis of the above embodiments, optionally, the differential filter amplifier module 2 includes: a third resistor R3, a fourth resistor R4, a fifth resistor R5 and a second capacitor C2. The third resistor R3 and the fourth resistor R4 are connected in series between the inverting input terminal B of the main operational amplifier 21 and the first power line N. The fifth resistor R5 is connected in series between the inverting output terminal A of the bias module 1 and the inverting input terminal B of the main operational amplifier 21. The third resistor R3 and the second capacitor C2 constitute a first low-pass filter unit 22, which is used to filter out the AC signal input to the inverting input terminal B of the main operational amplifier 21.

[0043] Specifically, the fifth resistor R5 is connected in series between the inverting output terminal A of the bias module 1 and the inverting input terminal B of the main operational amplifier 21. The voltage induced by the fifth resistor R5 is the voltage input to the inverting input terminal B of the main operational amplifier 21. After the first low-pass filter unit 22 filters out the AC signal input to the inverting input terminal B of the main operational amplifier 21, the DC signal induces a DC component in the fifth resistor R5 and is input to the inverting input terminal B of the main operational amplifier. When the resistance value of the fifth resistor R5 is larger, the induced DC component is also larger, so that the differential filter amplifier module 2 outputs a larger DC component.

[0044] Based on the above embodiments, optionally, the amplification factor of the bias module 1 is: A×K1, where: A∈[-1,0), R5 is the resistance value of the fifth resistor, R3 is the resistance value of the third resistor, and R4 is the resistance value of the fourth resistor.

[0045] Specifically,

[0046] Among them, U D is the output voltage of the output terminal D of the main operational amplifier 21, x2 is the DC component input to the inverting input terminal B of the main operational amplifier 21, R3 is the resistance value of the third resistor, R4 is the resistance value of the third resistor, and R9 is the resistance value of the ninth resistor.

[0047] According to the virtual disconnection principle of the ideal operational amplifier, we can get:

[0048]

[0049] Among them, U N is the common mode voltage in the first power line N, U A is the output voltage of the inverting output terminal A of bias module 1, U B is the input voltage of the inverting input terminal B of the main operational amplifier 21, and R5 is the resistance value of the fifth resistor.

[0050] When the amplification factor of bias module 1 is K2,

[0051] Wherein, R1 is the resistance value of the first resistor, and R2 is the resistance value of the second resistor.

[0052] When A=-1,

[0053]

[0054] at this time,

[0055] It can be seen that when K2=-K1, the common-mode voltage in the first power line N is completely eliminated, and only the DC component of the inverting input terminal B of the input main operational amplifier is retained. At this time, the DC component of the inverting input terminal B of the input main operational amplifier is the purest, without the interference of the common-mode voltage. At this time, the resistance value of the fifth resistor can theoretically be infinite, so a very large voltage will be generated on the fifth resistor. In the actual circuit, if all common-mode voltages are to be eliminated, the inverting output terminal A of the bias module needs to output a very large bias voltage. Because the power of the bias module 1 is limited, this adjustment method may not be satisfied, and the bias module 1 is in high-power operation for a long time, which is not conducive to the stable operation of the DC component detection circuit.

[0056] When A=-0.5,

[0057]

[0058] at this time,

[0059] It can be seen that when K2=-0.5K1, half of the common-mode voltage in the first power line N is eliminated, and at this time, the DC component input to the inverting input terminal B of the main operational amplifier includes half of the common-mode voltage in the first power line N. The main operational amplifier 21 has a certain common-mode voltage tolerance, so in this case, it can ensure that the power of the bias module 1 meets the output of the bias voltage, and the common-mode voltage input to the main operational amplifier 21 can also meet the tolerance range of the main operational amplifier 21.

[0060] If A=0,

[0061] U A =0,

[0062] at this time,

[0063] It can be seen that the bias module 1 at this time cannot play a role. This solution is equivalent to the regulation solution of the prior art. The common mode voltage in the first power line N is completely retained, and the regulation effect is poor.

[0064] In summary, when A is -1, the common-mode voltage is completely filtered out and the DC signal is purest. As A gradually increases, the common-mode voltage also increases. When A approaches 0, the common-mode voltage is completely retained and the bias module 1 does not work. In the actual circuit, the specific value of A can also be freely set according to the common-mode voltage tolerance of the main operational amplifier 21.

[0065] Table 1 is a test data of the output voltage of a differential filter amplifier module 2 provided according to an embodiment of the utility model. Referring to Table 1, optionally, the table is measured under the conditions of A=-0.5, the common mode voltage is adjusted to 50V, and the operational amplifier power supply voltage is ±5V:

[0066]

[0067] Specifically, it can be seen from Table 1 that, compared with the test value of the bias-free module 1 in the prior art, the test data of the present solution is closer to the actual voltage value and has a smaller error.

[0068] Continue to refer Figure 2On the basis of the above embodiments, optionally, the differential filter amplifier module 2 further includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a tenth resistor R10, a third capacitor C3, a fourth capacitor C4 and a fifth capacitor C5; the sixth resistor R6 and the seventh resistor R7 are connected in series between the non-inverting input terminal C of the main operational amplifier and the second power line L. The eighth resistor R8 is connected in series between the inverting output terminal A of the bias module 1 and the non-inverting input terminal C of the main operational amplifier 21. One end of the tenth resistor R10 and the fifth capacitor C5 are connected to the non-inverting input terminal C of the main operational amplifier 21, and the other end is grounded; one end of the ninth resistor R9 and the fourth capacitor C4 are connected to the inverting input terminal B of the main operational amplifier 21, and the other end is connected to the output terminal D of the main operational amplifier 21.

[0069] Specifically, the third capacitor C3 and the sixth resistor R6 can constitute a filter circuit in the second power line L, which is used to filter out the high-frequency signal input from the second power line L to the non-phase input terminal C of the main operational amplifier 21. The second power line L is the live line, the first power line N is the neutral line, and the second power line L and the first power line N together form a power supply circuit. In the related art, the first power line N is used as a reference point. Due to the setting of the differential filter amplifier module 2, when the voltage division of the fifth resistor R5 is not equal to the voltage on the first power line N, a common mode voltage is generated between the first power line N and the ground terminal GND. The eighth resistor R8 is connected in series between the inverting output terminal A of the bias module 1 and the non-phase input terminal C of the main operational amplifier 21. The DC signal induced by the eighth resistor R8 is the DC signal input to the non-phase input terminal C of the main operational amplifier 21.

[0070] In order to ensure the symmetry of the input signal of the inverting input terminal B of the main operational amplifier 21 and the input signal of the non-inverting input terminal C of the main operational amplifier 21, the various resistors can be symmetrically set. For example, the resistance values ​​of the ninth resistor R9 and the tenth resistor R10 are equal, the resistance values ​​of the fifth resistor R5 and the eighth resistor R8 are equal, and the sum of the resistance values ​​of the third resistor R3 and the fourth resistor R4 is equal to the sum of the resistance values ​​of the sixth resistor R6 and the seventh resistor R7. Through this setting, the input voltage of the inverting input terminal B of the main operational amplifier 21 can be equal to the input voltage of the non-inverting input terminal C of the main operational amplifier 21, so that the adjustment method of the bias module 1 is faster and there is no need to repeatedly calculate the bias voltage.

[0071] Figure 3 A circuit diagram of another DC component detection circuit provided by an embodiment of the utility model, referring to Figure 3 On the basis of the above embodiments, optionally, the differential filtering and amplifying module 2 also includes a first follower unit 23, and the fifth resistor R5 is connected to the inverting input terminal B of the main operational amplifier 21 through the first follower unit 23, and the first follower unit 23 is used to ensure the integrity of the signal input to the inverting input terminal B of the main operational amplifier 21.

[0072] Specifically, the fifth resistor R5 is connected to the inverting input terminal B of the main operational amplifier through the first follower unit 23. The voltage induced by the fifth resistor R5 is the voltage of the inverting input terminal B of the main operational amplifier 21. After the first low-pass filter unit 22 filters the AC signal input to the first follower unit 23, the fourth resistor R4 and the sixth capacitor R6 can filter again. The DC signal induces a DC component in the fifth resistor R5 and inputs it to the first follower unit 23. The first follower unit 23 inputs the DC component to the inverting input terminal B of the main operational amplifier 21 through the eleventh resistor R11. The first follower unit 23 can be a voltage follower. The voltage follower has a high input impedance, a low output impedance, and a voltage gain of approximately 1. It is generally used on the input and output stages of a multi-stage amplifier circuit, and can also be used to connect two circuits, which can reduce the impact of direct connection between circuits and play a buffering role. In general, the voltage follower plays the role of buffering, isolation, and improving load capacity.

[0073] Continue to refer Figure 3 On the basis of the above embodiments, optionally, the differential filtering and amplifying module 2 also includes a second follower unit 24, and the eighth resistor R8 is connected to the non-inverting input terminal C of the main operational amplifier 21 through the second follower unit 24, and the second follower unit 23 is used to ensure the integrity of the signal input to the non-inverting input terminal C of the main operational amplifier 21.

[0074] Specifically, the eighth resistor R8 is connected to the non-inverting input terminal C of the main operational amplifier 21 through the second follower unit 24. The voltage induced by the eighth resistor R8 is the voltage input to the non-inverting input terminal C of the main operational amplifier 21. The sixth resistor R6 and the third capacitor C3 can constitute a filtering circuit. The seventh resistor R7 and the seventh capacitor C7 can filter again. The DC signal induces a DC component in the eighth resistor R8 and is input into the second follower unit 24. The second follower unit 24 inputs the DC component into the non-inverting input terminal C of the main operational amplifier 21 through the twelfth resistor R12.

[0075] Figure 4 A circuit diagram of another DC component detection circuit provided by an embodiment of the utility model, referring to Figure 4On the basis of the above embodiments, the bias module 1 optionally includes a common direction amplification unit 14 and a reverse direction amplification unit 15; the positive input terminal of the common direction amplification unit 14 is connected to the first power line N, and the output terminal of the common direction amplification unit 14 is connected to the reverse input terminal of the reverse direction amplification unit 15. The differential filter amplification module 2 includes a first low-pass filter unit 22, a main operational amplifier 21 and an adder 25; the first low-pass filter unit 22 is connected between the first power line N and the reverse input terminal of the main operational amplifier 21; the output terminal of the main operational amplifier 21 is connected to the reverse input terminal of the adder 25, and the output terminal of the common direction amplification unit 14 is also connected to the reverse input terminal of the adder 25.

[0076] Specifically, the same-direction amplification unit 14 includes a tenth capacitor C10, an eighth capacitor C8, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18 and a same-direction amplifier 141. The sixteenth resistor R16 and the eighth capacitor C8 constitute a low-pass filter unit for filtering out the AC component of the first power line N input to the bias module 1. The same-direction amplification unit 14 can amplify the filtered DC signal and input it into the reverse amplification unit 15 and the adder 25. The reverse amplifier unit 15 includes a first resistor R1, a second resistor R2 and a reverse amplifier 151. The reverse input terminal of the reverse amplifier 151 receives the DC signal output by the non-inverting amplifier 141, inverts the DC signal, and then inputs it to the reverse input terminal of the main operational amplifier 21 through the fifth resistor R5. The eleventh capacitor C11 and the thirteenth resistor R13 are connected in parallel between the reverse input terminal and the output terminal of the main operational amplifier 21. The sixth capacitor C6, the eighth resistor R8 and the fourteenth resistor R14 are connected in parallel, one end of which is connected to the non-inverting input terminal of the main operational amplifier 21, and the other end is grounded. The sixth resistor R6 and the third capacitor C3, the seventh resistor R7 and the sixth capacitor C6 are used to filter out the AC component input from the second power line L to the non-inverting input terminal of the main operational amplifier 21. At this time, because the signals input to the non-inverting input terminal and the reverse input terminal of the main operational amplifier 21 are asymmetric, the DC signal output from the output terminal of the main operational amplifier 21 still has a bias voltage. The main operational amplifier 21 inputs the DC signal at this time into the adder 25 through the twelfth resistor R12. The nineteenth resistor R19 and the ninth capacitor C9 are connected in parallel between the inverting input terminal and the output terminal of the adder 25, and the non-inverting input terminal of the adder 25 is directly grounded. The adder 25 superimposes the DC signal output by the same-direction amplification unit 14 and the DC signal output by the main operational amplifier 21 and outputs them. The DC signal input into the adder 25 through the same-direction amplification unit 14 can offset the bias voltage of the DC signal output by the output terminal of the main operational amplifier 21, and only retains the DC signal value, thereby improving the sampling accuracy of the DC component.

[0077] The embodiment of the utility model provides a photovoltaic inverter system, including a photovoltaic inverter and a DC component detection circuit as described in any of the above embodiments. The output end of the photovoltaic inverter is connected to the first power line N, and is used to provide power to the first power line N and other modules in the photovoltaic inverter system. The photovoltaic inverter system has the corresponding beneficial effects of the DC component detection circuit, which will not be described in detail.

[0078] It should be understood that the various forms of processes shown above can be used to reorder, add or delete steps. For example, the steps described in the present invention can be performed in parallel, sequentially or in different orders, as long as the desired results of the technical solution of the present invention can be achieved, and this document does not limit this.

[0079] The above specific implementations do not constitute a limitation on the protection scope of the present utility model. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present utility model shall be included in the protection scope of the present utility model.

Claims

1. A DC component detection circuit, characterized in that: The DC component detection circuit comprises: Differential filter amplifier module and bias module; The differential filter amplification module comprises a main operational amplifier, and an inverting input terminal of the main operational amplifier is electrically connected to the first power line; The input end of the bias module is connected to the first power line, the bias module includes an inverting output end, the inverting output end of the bias module is electrically connected to the inverting input end of the main operational amplifier, the bias module is used to low-pass filter and invert the signal on the first power line and then output it from the inverting output end of the bias module, and the bias module is used to reduce the common mode voltage input to the main operational amplifier.

2. The DC component detection circuit according to claim 1, characterized in that: The differential filter amplification module includes a first low-pass filter unit, which is connected between the first power line and the inverting input terminal of the main operational amplifier; the bias module includes a second low-pass filter unit, which has the same time constant as the first low-pass filter unit.

3. The DC component detection circuit according to claim 2, characterized in that: The bias module includes a first resistor, a second resistor, a first capacitor and a bias operational amplifier; The first resistor is connected between the input end of the bias module and the inverting input end of the bias operational amplifier, and the second resistor and the first capacitor are connected in parallel and then connected between the inverting input end of the bias operational amplifier and the output end of the bias operational amplifier; The first capacitor and the first resistor constitute the second low-pass filtering unit.

4. The DC component detection circuit according to claim 3, characterized in that: The differential filtering and amplifying module comprises: a third resistor, a fourth resistor, a fifth resistor and a second capacitor; The third resistor and the fourth resistor are connected in series between the inverting input terminal of the main operational amplifier and the first power line; The fifth resistor is connected in series between the inverting output terminal of the bias module and the inverting input terminal of the main operational amplifier; The third resistor and the second capacitor constitute the first low-pass filter unit, and the first low-pass filter unit is used to filter out the AC signal input to the inverting input terminal of the main operational amplifier.

5. The DC component detection circuit according to claim 4, characterized in that: The amplification factor of the bias module is: , in, , ∈[-1,0), is the resistance value of the fifth resistor, is the resistance of the third resistor, is the resistance value of the fourth resistor.

6. The DC component detection circuit according to claim 5, characterized in that: The differential filter amplification module further includes a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a third capacitor, a fourth capacitor and a fifth capacitor; the sixth resistor and the seventh resistor are connected in series between the non-inverting input terminal of the main operational amplifier and the second power line; The eighth resistor is connected in series between the inverting output terminal of the bias module and the non-inverting input terminal of the main operational amplifier; One end of the tenth resistor and the fifth capacitor is connected to the non-inverting input terminal of the main operational amplifier, and the other end is grounded; one end of the ninth resistor and the fourth capacitor is connected to the inverting input terminal of the main operational amplifier, and the other end is connected to the output terminal of the main operational amplifier.

7. The DC component detection circuit according to claim 4, characterized in that: The differential filter amplification module also includes a first follower unit, and the fifth resistor is connected to the inverting input terminal of the main operational amplifier through the first follower unit. The first follower unit is used to ensure the integrity of the signal input to the inverting input terminal of the main operational amplifier.

8. The DC component detection circuit according to claim 6, characterized in that: The differential filter amplification module also includes a second follower unit, and the eighth resistor is connected to the non-inverting input terminal of the main operational amplifier through the second follower unit. The second follower unit is used to ensure the integrity of the signal input to the non-inverting input terminal of the main operational amplifier.

9. The DC component detection circuit according to claim 1, characterized in that: The bias module includes a common-direction amplification unit and a reverse-direction amplification unit; a non-phase input terminal of the common-direction amplification unit is connected to the first power line, and an output terminal of the common-direction amplification unit is connected to an inverting input terminal of the reverse-direction amplification unit; The differential filtering and amplifying module further comprises an adder; the output end of the main operational amplifier is connected to the inverting input end of the adder, and the output end of the in-phase amplifying unit is connected to the inverting input end of the adder.

10. A photovoltaic inverter system, characterized in that: It comprises a photovoltaic inverter and a DC component detection circuit as described in any one of claims 1 to 9; the output end of the photovoltaic inverter is connected to the first power line.

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