Frequency sampling circuit, device, converter, system, method, medium and product

Abstract

The invention provides a frequency sampling circuit and device, a converter, a system, a method, a medium and a product. The frequency sampling circuit comprises an isolation sampling circuit configured to receive a first voltage signal from a power grid and output a second voltage signal in response to the first voltage signal, the voltage value of the second voltage signal is smaller than that of the first voltage signal, and the second voltage signal comprises a first sub-voltage signal and a second sub-voltage signal; the operational amplification circuit is configured to receive the first sub-voltage signal and the second sub-voltage signal and perform differential amplification processing on the first sub-voltage signal and the second sub-voltage signal to output a third voltage signal; and the comparison circuit is configured to receive the third voltage signal and compare the third voltage signal with a reference voltage signal to output a comparison result.

Description

Technical Field

[0001] This disclosure relates to the field of photovoltaic converter technology, and in particular to a frequency sampling circuit, device, converter, system, method, medium and product. Background Technology

[0002] Currently, large shopping malls, hotels, hospitals, schools, and office buildings are all places with high demand for cooling, and air conditioning accounts for a significant portion of building electricity consumption. There is a potential compatibility between photovoltaic (PV) power generation and air conditioning power consumption. High-power commercial PV converter centrifugal / screw chillers are widely used in these locations. In summer, PV power directly supplies the centrifugal / screw chillers. When there is surplus PV power, it can be fed into the grid. In winter, when the centrifugal / screw chillers are not running, PV power is fed into the grid. During the operation of the PV converter (or frequency converter), if the grid frequency detection is inaccurate, it will affect the rectification AC / DC process, leading to inaccurate control of the IGBT (Insulated-Gate Bipolar Transistor) transistors, resulting in harmonics and reduced efficiency. Furthermore, when there is surplus PV power fed into the grid, if the frequency is too high or too low, the PV converter needs to disconnect from the grid.

[0003] However, the accuracy of power grid frequency detection in related technologies is low, which can easily lead to the aforementioned problems. Summary of the Invention

[0004] One technical problem addressed by this disclosure is the low accuracy of power grid frequency detection in related technologies.

[0005] According to one aspect of this disclosure, a frequency sampling circuit is provided, comprising: an isolation sampling circuit configured to receive a first voltage signal from a power grid and, in response to the first voltage signal, output a second voltage signal, wherein the voltage value of the second voltage signal is less than the voltage value of the first voltage signal, and the second voltage signal includes a first sub-voltage signal and a second sub-voltage signal; an operational amplifier circuit configured to receive the first sub-voltage signal and the second sub-voltage signal, and differentially amplify the first sub-voltage signal and the second sub-voltage signal to output a third voltage signal; and a comparison circuit configured to receive the third voltage signal and compare the third voltage signal with a reference voltage signal to output a comparison result.

[0006] In some embodiments, the isolation sampling circuit includes: a first resistor and a second resistor connected in series between a first voltage terminal and a second voltage terminal of the power grid; an isolation device, wherein a first input terminal of the isolation device is electrically connected to a first terminal of the second resistor, a second input terminal of the isolation device is electrically connected to a second terminal of the second resistor, a first output terminal of the isolation device is electrically connected to a first input terminal of the operational amplifier circuit, and a second output terminal of the isolation device is electrically connected to a second input terminal of the operational amplifier circuit.

[0007] In some embodiments, the operational amplifier circuit includes: a differential operational amplifier, wherein a first input terminal of the differential operational amplifier is electrically connected to a first output terminal of the isolation device, a second input terminal of the differential operational amplifier is electrically connected to a second output terminal of the isolation device, and an output terminal of the differential operational amplifier is electrically connected to a first input terminal of the comparator circuit; a third resistor disposed between the second input terminal of the differential operational amplifier and the second output terminal of the isolation device; a fourth resistor disposed between the first input terminal of the differential operational amplifier and the first output terminal of the isolation device; a fifth resistor electrically connected between the first input terminal of the differential operational amplifier and a ground terminal; and a sixth resistor electrically connected between the second input terminal of the differential operational amplifier and the output terminal of the differential operational amplifier.

[0008] In some embodiments, the resistance value of the third resistor is equal to the resistance value of the fourth resistor, the resistance value of the fifth resistor is equal to the resistance value of the sixth resistor, and the ratio of the resistance value of the fourth resistor to the resistance value of the fifth resistor is a predetermined ratio.

[0009] In some embodiments, the operational amplifier circuit further includes: a first capacitor electrically connected between a first input terminal and a ground terminal of the differential operational amplifier; and a second capacitor electrically connected between a second input terminal and an output terminal of the differential operational amplifier.

[0010] In some embodiments, the comparison circuit includes: a comparator, a first input terminal of the comparator being electrically connected to the output terminal of the operational amplifier circuit, a second input terminal of the comparator being configured to receive the reference voltage signal, and an output terminal of the comparator being configured to output the comparison result.

[0011] In some embodiments, the comparator circuit further includes a seventh resistor and an eighth resistor connected in series between the power supply voltage terminal and the ground terminal; wherein the second input terminal of the comparator is electrically connected to the connection point between the seventh resistor and the eighth resistor.

[0012] In some embodiments, the frequency sampling circuit further includes a filtering circuit disposed between the operational amplifier circuit and the comparator circuit, configured to filter the third voltage signal.

[0013] In some embodiments, the filter circuit includes: a ninth resistor and a third capacitor electrically connected between the output terminal of the operational amplifier circuit and the first input terminal of the comparator circuit; and a tenth resistor, the first end of which is electrically connected to the connection point between the ninth resistor and the third capacitor, and the second end of which is electrically connected to ground.

[0014] In some embodiments, the frequency sampling circuit further includes a clamping circuit disposed between the operational amplifier circuit and the comparator circuit, configured to clamp the third voltage signal so that the third voltage signal is within a predetermined voltage range.

[0015] In some embodiments, the clamping circuit includes an eleventh resistor and a twelfth resistor connected in series between a power supply voltage terminal and a ground terminal, wherein the connection point between the eleventh resistor and the twelfth resistor is electrically connected to a first input terminal of the comparator circuit.

[0016] In some embodiments, the frequency sampling circuit further includes a pull-up circuit or a pull-down circuit, disposed at the output terminal of the comparator circuit.

[0017] According to another aspect of this disclosure, a frequency detection apparatus is provided, comprising: a frequency sampling circuit as described above; and a control device configured to receive the comparison result from the frequency sampling circuit, record the number of comparison results within a predetermined time period, and calculate the frequency of the power grid based on the predetermined time period and the number of comparison results.

[0018] In some embodiments, the frequency detection device is applied to the generator system; the control device is further configured to determine that the generator system is not faulty when the frequency of the power grid is within a predetermined frequency range, and to determine that the generator system is faulty when the frequency of the power grid is outside the predetermined frequency range.

[0019] According to another aspect of this disclosure, a converter is provided, comprising: a rectifier, one side of which is electrically connected to a power grid, and the other side of which is electrically connected to an inverter and a photovoltaic power generation system; the inverter, electrically connected to an electrical appliance; a first sampling circuit, electrically connected to the power grid, the first sampling circuit including the frequency sampling circuit as described above; and a control device configured to receive the comparison results from the frequency sampling circuit, record the number of comparison results within a predetermined time period, and calculate the frequency of the power grid based on the predetermined time period and the number of comparison results.

[0020] In some embodiments, the converter further includes: a first drive circuit disposed between the control device and the rectifier, configured to receive a first control signal from the control device, and control the rectifier to turn on or off based on the first control signal; wherein the control device is further configured to send the first control signal to the first drive circuit based on information collected by the first sampling circuit.

[0021] In some embodiments, the converter further includes: a second sampling circuit electrically connected to the inverter, configured to acquire the current signal output by the inverter and transmit it to the control device; a second drive circuit disposed between the control device and the inverter, configured to receive a second control signal from the control device and control the inverter to turn on or off based on the second control signal; wherein the control device is further configured to send the second control signal to the second drive circuit based on the current signal output by the inverter.

[0022] According to another aspect of this disclosure, a unit system is provided, including: a converter as described above.

[0023] According to another aspect of this disclosure, a frequency detection method based on the frequency sampling circuit as described above is provided, comprising: receiving the comparison result from the frequency sampling circuit and recording the number of comparison results within a predetermined time period; and calculating the frequency of the power grid based on the predetermined time period and the number of comparison results.

[0024] In some embodiments, the frequency detection method further includes: determining that the unit system has not failed when the frequency of the power grid is within a predetermined frequency range; and determining that the unit system has failed when the frequency of the power grid is outside the predetermined frequency range.

[0025] According to another aspect of this disclosure, a control device is provided, comprising: a memory; and a processor coupled to the memory, the processor being configured to execute the frequency detection method as described above based on instructions stored in the memory.

[0026] According to another aspect of this disclosure, a computer-readable storage medium is provided having computer instructions stored thereon that, when executed by a processor, implement the frequency detection method as described above.

[0027] According to another aspect of this disclosure, a computer program product is provided, comprising a computer program or instructions that, when executed by a processor, implement the frequency detection method as described above.

[0028] In the frequency sampling circuit described above, since the isolation sampling circuit can isolate the first voltage signal of the power grid from the second voltage signal used for frequency detection, the interference of the first voltage signal on the signal during the frequency detection process can be reduced. Moreover, through the differential amplification processing of the operational amplifier circuit, a voltage signal that is easy to process can be formed so that the comparison circuit can compare and process it, thereby facilitating frequency detection. Therefore, this can improve the accuracy of frequency detection of the power grid.

[0029] Other features and advantages of this disclosure will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0030] The accompanying drawings, which form part of this specification, illustrate embodiments of this disclosure and, together with the specification, serve to explain the principles of this disclosure.

[0031] This disclosure will become clearer with reference to the accompanying drawings and the following detailed description, wherein:

[0032] Figure 1 This is a schematic block diagram illustrating the structure of a frequency sampling circuit according to some embodiments of the present disclosure;

[0033] Figure 2 This is a schematic diagram showing the connection of a frequency sampling circuit according to some embodiments of the present disclosure;

[0034] Figure 3 This is a schematic diagram showing the connection of a frequency sampling circuit according to other embodiments of the present disclosure;

[0035] Figure 4 This is a schematic block diagram illustrating the structure of a frequency detection apparatus according to some embodiments of the present disclosure;

[0036] Figure 5 This is a schematic block diagram illustrating the structure of a converter according to some embodiments of the present disclosure;

[0037] Figure 6 This is a schematic diagram illustrating the direction of current in photovoltaic power generation according to some embodiments of the present disclosure;

[0038] Figure 7 This is a schematic diagram illustrating the direction of current in an electrical device according to some embodiments of the present disclosure when it is powered on;

[0039] Figure 8 This is a flowchart illustrating a frequency detection method according to some embodiments of the present disclosure;

[0040] Figure 9 This is a structural block diagram illustrating a control device according to some embodiments of the present disclosure;

[0041] Figure 10 This is a structural block diagram illustrating a control device according to some embodiments of the present disclosure.

[0042] It should be understood that the dimensions of the various parts shown in the accompanying drawings are not drawn to actual scale. Furthermore, the same or similar reference numerals denote the same or similar components. Detailed Implementation

[0043] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. The descriptions of the exemplary embodiments are merely illustrative and are in no way intended to limit the present disclosure or its application or use. The present disclosure may be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided so that the present disclosure will be thorough and complete, and will fully express the scope of the disclosure to those skilled in the art. It should be noted that, unless specifically stated otherwise, the relative arrangement of components and steps, the composition of materials, numerical expressions, and values ​​set forth in these embodiments should be interpreted as exemplary only and not as limiting.

[0044] The terms "first," "second," and similar words used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. Words such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well. Terms such as "above," "below," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, this relative positional relationship may also change accordingly.

[0045] In this disclosure, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may be not directly connected to the other devices but have an intermediary device.

[0046] All terms used in this disclosure (including technical or scientific terms) have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in a general dictionary, such as a dictionary, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and not as having an idealized or highly formalized meaning, unless expressly defined herein.

[0047] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0048] The inventors of this disclosure have discovered that in related technologies, when a frequency sampling circuit collects the voltage signal of the power grid to detect the frequency of the power grid, the voltage signal of the power grid, being a strong electrical signal, is prone to interfering with the relevant signals during the detection process, thereby affecting the detection results and reducing the accuracy of power grid frequency detection.

[0049] Therefore, embodiments of this disclosure provide a frequency sampling circuit to improve the accuracy of power grid frequency detection. The frequency sampling circuit is described in detail below with reference to the accompanying drawings.

[0050] Figure 1 This is a schematic block diagram illustrating the structure of a frequency sampling circuit according to some embodiments of the present disclosure. Figure 1 As shown, the frequency sampling circuit includes an isolation sampling circuit 110, an operational amplifier circuit 120, and a comparator circuit 130.

[0051] The isolation sampling circuit 110 is configured to receive a first voltage signal V1 from the power grid and, in response to the first voltage signal, output a second voltage signal V2. The voltage value of the second voltage signal V2 is less than the voltage value of the first voltage signal V1. The second voltage signal V2 includes a first sub-voltage signal V. 21 Second sub-voltage signal V 22 In other words, the first sub-voltage signal V 21 The voltage value and the second sub-voltage signal V 22 The voltage values ​​of all of them are less than the voltage value of the first voltage signal V1.

[0052] It should be noted that in some cases, when the first voltage signal and the second voltage signal are alternating voltage signals, the above "voltage values" can all be the effective voltage values ​​of the corresponding voltage signals.

[0053] Here, the first voltage signal is a high-voltage signal, and the second voltage signal is a low-voltage signal. For example, the first voltage signal is a sinusoidal voltage signal with an effective voltage value of 380V. The second voltage signal has a voltage value of 2V; therefore, the first and second sub-voltage signals of the second voltage signal also have a voltage value of 2V. In this way, the isolation sampling circuit converts the high-voltage signal into a low-voltage signal of a certain proportion, thereby isolating the high-voltage signal from the power grid from the low-voltage signal in the subsequent frequency detection process. This reduces the interference of the high-voltage signal on the low-voltage signal during detection, thus improving the accuracy of power grid frequency detection.

[0054] Operational amplifier circuit 120 is configured to receive first sub-voltage signal V 21 Second sub-voltage signal V 22 The first and second sub-voltage signals are differentially amplified to output the third voltage signal V3.

[0055] Here, the operational amplifier circuit performs differential processing to convert the first sub-voltage signal V... 21 Second sub-voltage signal V 22 By synthesizing a voltage signal, such as a sine wave, and then amplifying it using an operational amplifier circuit, the voltage signal can be converted into a more easily processed signal. For example, a sine wave voltage signal ranging from -2V to +2V can be amplified to a sine wave voltage signal ranging from -3.3V to +3.3V. This facilitates subsequent comparison processing.

[0056] Comparator circuit 130 is configured to receive a third voltage signal V3 and compare the third voltage signal V3 with a reference voltage signal V ref Compare and output the comparison result V4.

[0057] For example, a comparator circuit is used when the third voltage signal V3 is greater than the reference voltage signal V. ref The first level signal is output when the third voltage signal V3 is less than or equal to the reference voltage signal V. ref The comparator outputs a second-level signal, where the first-level signal is higher than the second-level signal. That is, the first-level signal is a high-level signal (e.g., +3.3V), and the second-level signal is a low-level signal (e.g., -3.3V). Here, the first-level signal and the second-level signal are the comparison result. The comparator can output the comparison result to the control device so that the control device can calculate the frequency of the power grid.

[0058] Thus, a frequency sampling circuit according to some embodiments of the present disclosure is provided. The frequency sampling circuit includes: an isolation sampling circuit configured to receive a first voltage signal from the power grid and, in response to the first voltage signal, output a second voltage signal, wherein the voltage value of the second voltage signal is less than the voltage value of the first voltage signal, and the second voltage signal includes a first sub-voltage signal and a second sub-voltage signal; an operational amplifier circuit configured to receive the first sub-voltage signal and the second sub-voltage signal, and differentially amplify the first sub-voltage signal and the second sub-voltage signal to output a third voltage signal; and a comparator circuit configured to receive the third voltage signal and compare the third voltage signal with a reference voltage signal to output a comparison result. In this frequency sampling circuit, since the isolation sampling circuit can isolate the first voltage signal from the power grid from the second voltage signal used for frequency detection, the interference of the first voltage signal on the signal during the frequency detection process can be reduced. Moreover, the differential amplification processing by the operational amplifier circuit can form a voltage signal that is easy to process, facilitating comparison processing by the comparator circuit, thereby facilitating frequency detection. Therefore, this can improve the accuracy of frequency detection of the power grid.

[0059] Figure 2 This is a schematic diagram showing the connection of a frequency sampling circuit according to some embodiments of the present disclosure.

[0060] like Figure 2 As shown, the frequency sampling circuit includes an isolation sampling circuit 110, an operational amplifier circuit 120, and a comparator circuit 130.

[0061] like Figure 2 As shown, the isolation sampling circuit 110 includes a first resistor R1 and a second resistor R2. The first resistor R1 and the second resistor R2 are connected in series between the first voltage terminal UA and the second voltage terminal UB of the power grid. That is, the first terminal of the first resistor R1 is electrically connected to the first voltage terminal UA, the second terminal of the first resistor R1 is electrically connected to the first terminal of the second resistor R2, and the second terminal of the second resistor R2 is electrically connected to the second voltage terminal UB.

[0062] The isolated sampling circuit 110 also includes an isolation device U1. The first input terminal INP of the isolation device U1 is electrically connected to the first terminal of the second resistor R2, the second input terminal INN of the isolation device U1 is electrically connected to the second terminal of the second resistor R2, the first output terminal OUTP of the isolation device U1 is electrically connected to the first input terminal of the operational amplifier circuit 120, and the second output terminal OUTN of the isolation device U1 is electrically connected to the second input terminal of the operational amplifier circuit 120.

[0063] In the above embodiment, the first voltage terminal UA and the second voltage terminal UB are connected via a first resistor R1 and a second resistor R2. For example, the voltage between the first voltage terminal UA and the second voltage terminal UB is 380V, with a peak value of 380V × 1.414 = 537V. Therefore, the ratio of the resistance value of the first resistor R1 to the resistance value of the second resistor R2 can be adjusted to 535:2. This allows the desired first voltage signal V1 to be obtained. Furthermore, the frequency sampling circuit can use surface-mount components to reduce sampling loss.

[0064] In some embodiments, the first resistor R1 can be a resistor of several hundred kΩ (kiloohms), and the second resistor R2 can be a resistor of several kΩ. For example, the first resistor has a resistance of 535 kΩ and the second resistor has a resistance of 2 kΩ, which makes the voltage between the two input terminals IN1 and IN2 of the input isolation device U1 ±2V.

[0065] Of course, those skilled in the art will understand that the resistance values ​​of the first and second resistors described above are merely exemplary, and the scope of this disclosure is not limited thereto. For example, appropriate resistance values ​​for the first and second resistors can be selected according to actual circumstances or needs.

[0066] The isolation device U1 can be an isolation operational amplifier, isolating its input from its output. This isolation device U1 is electrically connected to two power supply terminals 210 and 230. For example, power supply terminal 210, which can be called the first power supply terminal, can provide a voltage of 3.3V. As another example, power supply terminal 230, which can be called the second power supply terminal, can provide a voltage of 5V. That is, the front and rear ends of the isolation device U1 are powered by 5V and 3.3V, respectively. The isolation device U1 is also electrically connected to ground terminal 220.

[0067] For example, the gain of isolation device U1 is 1. For example, the voltage range of the output terminals OUT1 / OUT2 of isolation device U1 is ±2V.

[0068] In the above embodiments, the isolation sampling circuit is implemented using a first resistor, a second resistor, and an isolation device. This isolation sampling circuit can isolate the strong electrical signal from the weak electrical signal during the frequency detection process, reducing the interference of the strong electrical signal on the weak electrical signal during the detection process, thereby improving the accuracy of power grid frequency detection.

[0069] like Figure 2As shown, the operational amplifier circuit 120 includes a differential operational amplifier U2. The first input terminal IN21 (e.g., the positive input terminal) of the differential operational amplifier U2 is electrically connected to the first output terminal OUTP of the isolation device U1, the second input terminal IN22 (e.g., the negative input terminal) of the differential operational amplifier U2 is electrically connected to the second output terminal OUTN of the isolation device U1, and the output terminal OUT2 of the differential operational amplifier U2 is electrically connected to the first input terminal of the comparator circuit.

[0070] like Figure 2 As shown, the operational amplifier circuit 120 may also include a third resistor R3. The third resistor R3 is disposed between the second input terminal IN22 of the differential operational amplifier U2 and the second output terminal OUTN of the isolation device U1.

[0071] like Figure 2 As shown, the operational amplifier circuit 120 may also include a fourth resistor R4. The fourth resistor R4 is disposed between the first input terminal IN21 of the differential operational amplifier U2 and the first output terminal OUTP of the isolation device U1.

[0072] like Figure 2 As shown, the operational amplifier circuit 120 may also include a fifth resistor R5. The fifth resistor R5 is electrically connected between the first input terminal IN21 of the differential operational amplifier U2 and the ground terminal 220. In this way, the rear end of the fourth resistor R4 is connected to the ground terminal (i.e., analog ground) through the fifth resistor R5.

[0073] like Figure 2 As shown, the operational amplifier circuit 120 may further include a sixth resistor R6. The sixth resistor R6 is electrically connected between the second input terminal IN22 of the differential operational amplifier U2 and the output terminal OUT2 of the differential operational amplifier U2. In this way, the rear end of the third resistor R3 is connected to the output terminal of the differential operational amplifier U2 through the sixth resistor R6.

[0074] This provides an operational amplifier circuit according to some embodiments of the present disclosure. This operational amplifier circuit enables differential amplification, thereby combining the inconveniently compared first and second sub-voltage signals into a more easily processed third voltage signal. This facilitates comparison by subsequent comparison circuitry, thereby simplifying frequency detection and improving the accuracy of power grid frequency detection.

[0075] In some embodiments, the resistance value of the third resistor R3 is equal to the resistance value of the fourth resistor R4, the resistance value of the fifth resistor R5 is equal to the resistance value of the sixth resistor R6, and the ratio of the resistance value of the fourth resistor R4 to the resistance value of the fifth resistor R5 is a predetermined ratio. This allows a matched input voltage signal to be input to the input terminal of the differential operational amplifier U2, and a matched output voltage signal to be output from the output terminal of the differential operational amplifier U2, improving the accuracy of the differential amplification process.

[0076] For example, R3 = R4, R5 = R6, and R4:R5 = 2:3.3. This allows the input terminal of the differential operational amplifier U2 to receive an input voltage signal of ±2V, and the output terminal of the differential operational amplifier U2 to output an output voltage signal of ±3.3V.

[0077] In some embodiments, the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6 are each selected as resistors in the kiloohm range. Of course, the embodiments disclosed herein are not limited to the specific values ​​of the third resistor R3, the fourth resistor R4, the fifth resistor R5, and the sixth resistor R6; resistors with appropriate resistance values ​​can be used according to actual circumstances or needs.

[0078] In some embodiments, such as Figure 2 As shown, the operational amplifier circuit 120 may further include a first capacitor C1, which is electrically connected between the first input terminal IN21 of the differential operational amplifier U2 and the ground terminal 220. That is, the first capacitor C1 is connected in parallel with the fifth resistor R5. The operational amplifier circuit 120 may further include a second capacitor C2, which is electrically connected between the second input terminal IN22 of the differential operational amplifier U2 and the output terminal OUT2 of the differential operational amplifier U2. That is, the second capacitor C2 is connected in parallel with the sixth resistor R6. In this embodiment, the first and second capacitors can serve as filters to reduce signal interference.

[0079] For example, the first capacitor C1 and the second capacitor C2 can be nanofarad (nF) level capacitors. For example, the capacitance values ​​of the first capacitor and the second capacitor can be 3.3nF, respectively. Of course, the embodiments of this disclosure are not limited to the specific values ​​of the first capacitor and the second capacitor, and appropriate capacitance values ​​of the first capacitor and the second capacitor can be selected according to the actual situation or actual needs.

[0080] like Figure 2As shown, the comparator circuit 130 may include a comparator U3. The first input terminal IN31 (e.g., the positive input terminal) of the comparator U3 is electrically connected to the output terminal of the operational amplifier circuit 120 (e.g., the output terminal OUT2 of the differential operational amplifier U2), and the second input terminal IN32 (e.g., the negative input terminal) of the comparator U3 is configured to receive a reference voltage signal V. ref The output terminal OUT3 of comparator U3 is configured to output the comparison result V4. In this embodiment, the comparator can be used to compare the third voltage signal with the reference voltage signal to output the comparison result, which facilitates frequency detection based on the comparison result.

[0081] like Figure 2 As shown, the comparator circuit 130 may further include a seventh resistor R7 and an eighth resistor R8. The seventh resistor R7 and the eighth resistor R8 are connected in series between the power supply voltage terminal 210 and the ground terminal 220. That is, the first end of the seventh resistor R7 is electrically connected to the power supply voltage terminal 210, the second end of the seventh resistor R7 is electrically connected to the first end of the eighth resistor R8, and the second end of the eighth resistor R8 is electrically connected to the ground terminal 220. The second input terminal IN32 of the comparator U3 is electrically connected to the connection point between the seventh resistor R7 and the eighth resistor R8 (i.e., the first end of the eighth resistor R8). This enables the comparator to receive the reference voltage signal V. ref The reference voltage signal V ref This is the voltage across the eighth resistor R8, which facilitates comparison and processing.

[0082] The seventh resistor R7 and the eighth resistor R8 are voltage divider resistors. For example, the resistance value of the seventh resistor R7 is equal to the resistance value of the eighth resistor R8. When the power supply voltage terminal 210 provides a voltage of 3.3V, the circuit composed of the seventh resistor R7 and the eighth resistor R8 can make the voltage at the second input terminal IN32 of the input comparator 1.65V.

[0083] In some embodiments, the resistance value of the seventh resistor R7 ranges from 1kΩ to 5kΩ. For example, the resistance value of the seventh resistor R7 is 2kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the seventh resistor R7 mentioned above. For example, the resistance value of the seventh resistor R7 can be set according to actual conditions or actual needs.

[0084] In some embodiments, the resistance value of the eighth resistor R8 ranges from 1kΩ to 5kΩ. For example, the resistance value of the eighth resistor R8 is 2kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the eighth resistor R8 mentioned above. For example, the resistance value of the eighth resistor R8 can be set according to actual conditions or actual needs.

[0085] Thus, a frequency sampling circuit according to some embodiments of the present disclosure is provided. In this frequency sampling circuit, the isolation device of the isolation sampling circuit can isolate the first voltage signal of the power grid from the second voltage signal used for frequency detection. Therefore, the interference of the first voltage signal on the signal during the frequency detection process can be reduced. Moreover, through the differential amplification processing of the operational amplifier circuit, a voltage signal that is easy to process can be formed for comparison processing by the comparison circuit, thereby facilitating frequency detection. Therefore, this can improve the accuracy of power grid frequency detection.

[0086] The frequency sampling circuit with isolation described in this embodiment can isolate the grid-side sampling signal from the motherboard-side signal, reduce the interference of high-voltage side-introduced interference signals to the control terminal, improve the accuracy of frequency sampling, and improve the stability of photovoltaic converter operation in centrifuge system and photovoltaic power generation system.

[0087] Figure 3 This is a schematic diagram showing the connection of a frequency sampling circuit according to other embodiments of the present disclosure.

[0088] like Figure 3 As shown, the frequency sampling circuit includes an isolation sampling circuit 110, an operational amplifier circuit 120, and a comparator circuit 130.

[0089] like Figure 3 As shown, the first resistor R1 includes a first sub-resistor R1' and a second sub-resistor R1". In actual sampling circuits, since the resistance value of the first resistor may not be easily matched with the second resistor R2 to form the required ratio, this utilizes two resistors to form a first resistor, thereby facilitating the realization of the resistance value of the first resistor. Of course, the embodiments of this disclosure are not limited to the above-described composition of the first resistor. For example, in some cases, a single resistor can be used as the first resistor, or three or more resistors can be used to form the first resistor.

[0090] In some embodiments, as Figure 3 As shown, the frequency sampling circuit may further include a filter circuit 140. The filter circuit 140 is disposed between the operational amplifier circuit 120 and the comparator circuit 130. For example, the filter circuit 140 is disposed between the differential operational amplifier U2 and the comparator U3. The filter circuit 140 is configured to filter the third voltage signal V3. By filtering the third voltage signal, signal interference can be reduced, and the accuracy of power grid frequency detection can be improved.

[0091] like Figure 3As shown, the filter circuit 140 may include a ninth resistor R9 and a third capacitor C3. The ninth resistor R9 and the third capacitor C3 are electrically connected between the output terminal of the operational amplifier circuit 120 and the first input terminal of the comparator circuit 130. For example, the first terminal of the ninth resistor R9 is electrically connected to the output terminal of the differential operational amplifier U2, the second terminal of the ninth resistor R9 is electrically connected to the first terminal of the third capacitor C3, and the second terminal of the third capacitor C3 is electrically connected to the first input terminal IN31 of the comparator U3.

[0092] In some embodiments, the resistance value of the ninth resistor R9 ranges from 3kΩ to 7kΩ. For example, the resistance value of the ninth resistor R9 is 5.1kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the ninth resistor R9 mentioned above. For example, the resistance value of the ninth resistor R9 can be set according to actual conditions or actual needs.

[0093] In some embodiments, the capacitance value of the third capacitor C3 ranges from 5 μF (microfarads) to 15 μF. For example, the capacitance value of the third capacitor C3 can be 10 μF. It should be noted that the scope of this disclosure is not limited to the specific range of the capacitance value of the third capacitor C3 mentioned above. For example, the capacitance value of the third capacitor C3 can be set according to actual conditions or actual needs.

[0094] like Figure 3 As shown, the filter circuit 140 may further include a tenth resistor R10. The first end of the tenth resistor R10 is electrically connected to the connection point between the ninth resistor R9 and the third capacitor C3 (i.e., the second end of the ninth resistor R9), and the second end of the tenth resistor R10 is electrically connected to the ground terminal 220. This tenth resistor can function as a pull-down resistor.

[0095] In some embodiments, the resistance value of the tenth resistor R10 ranges from 0.5kΩ to 1.5kΩ. For example, the resistance value of the tenth resistor R10 is 1kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the tenth resistor R10 mentioned above. For example, the resistance value of the tenth resistor R10 can be set according to actual conditions or actual needs.

[0096] Thus, the filter circuit is formed by the ninth resistor R9, the tenth resistor R10, and the third capacitor C3. This filter circuit has a simple structure, is easy to implement, and can reduce signal interference and improve the accuracy of power grid frequency detection.

[0097] In some embodiments, such as Figure 3As shown, the frequency sampling circuit may further include a clamping circuit 150. The clamping circuit 150 is disposed between the operational amplifier circuit 120 and the comparator circuit 130. Further, the clamping circuit 150 may be disposed between the filter circuit 140 and the comparator circuit 130. The clamping circuit 150 may be configured to clamp the third voltage signal so that the third voltage signal is within a predetermined voltage range (which may be referred to as a first predetermined voltage range). For example, the predetermined voltage range is -3.3V to 3.3V, that is, the clamping circuit 150 makes the third voltage signal within the range of -3.3V to 3.3V. In this embodiment, clamping the signal using the clamping circuit can make the sampled signal more accurate.

[0098] It should be noted that the specific range of the above-mentioned predetermined voltage range is merely exemplary, and the scope of this disclosure is not limited to the specific range of the predetermined voltage range. The specific value of the predetermined voltage range can be set according to the actual situation or actual needs.

[0099] For example, such as Figure 3 As shown, the clamping circuit 150 may include an eleventh resistor R11 and a twelfth resistor R12. The eleventh resistor R11 and the twelfth resistor R12 are connected in series between the power supply voltage terminal 210 and the ground terminal 220. For example, the first end of the eleventh resistor R11 is electrically connected to the power supply voltage terminal 210, the second end of the eleventh resistor R11 is electrically connected to the first end of the twelfth resistor R12, and the second end of the twelfth resistor R12 is electrically connected to the ground terminal. The connection point between the eleventh resistor R11 and the twelfth resistor R12 (e.g., the second end of the eleventh resistor R11) is electrically connected to the first input terminal of the comparator circuit. For example, the second end of the eleventh resistor R11 is electrically connected to the first input terminal IN31 of the comparator U3. Thus, the clamping circuit is implemented using the eleventh and twelfth resistors. By clamping the voltage signal using the clamping circuit, the sampling signal can be made more accurate, and the clamping circuit is simple and easy to implement.

[0100] In some embodiments, the resistance value of the eleventh resistor R11 ranges from 50kΩ to 100kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the eleventh resistor R11 mentioned above. For example, the resistance value of the eleventh resistor R11 can be set according to actual conditions or actual needs.

[0101] In some embodiments, the resistance value of the twelfth resistor R12 ranges from 50kΩ to 100kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the twelfth resistor R12 mentioned above. For example, the resistance value of the twelfth resistor R12 can be set according to actual conditions or actual needs.

[0102] In some embodiments, the resistance value of the eleventh resistor R11 is equal to the resistance value of the twelfth resistor R12. For example, the resistance values ​​of both the eleventh resistor R11 and the twelfth resistor R12 can be 100kΩ.

[0103] In some embodiments, such as Figure 3 As shown, the frequency sampling circuit may further include a pull-up circuit 160, which is disposed at the output terminal of the comparator circuit 130. For example, the pull-up circuit 160 may include a thirteenth resistor R13. The first terminal of the thirteenth resistor R13 is electrically connected to the power supply voltage terminal 210, and the second terminal of the thirteenth resistor R13 is electrically connected to the output terminal of the comparator circuit 130. That is, the thirteenth resistor R13 is electrically connected between the power supply voltage terminal 210 and the output terminal of the comparator circuit 130. This pull-up circuit can ensure that the voltage signal output by the comparator circuit is within a predetermined voltage range (e.g., -3.3V to +3.3V). This pull-up circuit can ensure that when the comparator circuit does not output a low-level signal, the signal connected to the chip (the chip connected to the output terminal of the comparator circuit, for example, a control device) is a high-level signal, which can reduce the occurrence of low-level interference signals at the output terminal of the comparator circuit caused by signal interference, making the signal more stable and improving the accuracy of power grid frequency detection.

[0104] In some embodiments, the resistance value of the thirteenth resistor R13 ranges from 0.5kΩ to 1.5kΩ. For example, the resistance value of the thirteenth resistor R13 is 1kΩ. It should be noted that the scope of this disclosure is not limited to the specific range of the resistance value of the thirteenth resistor R13 mentioned above. For example, the resistance value of the thirteenth resistor R13 can be set according to actual conditions or actual needs.

[0105] It should be noted that the pull-up circuit described above can also be replaced by a pull-down circuit. That is, the frequency sampling circuit may include a pull-down circuit (not shown in the figure), which is located at the output of the comparator circuit. This pull-down circuit can be electrically connected between the output of the comparator circuit 130 and the ground terminal. For example, the pull-down circuit may also include a resistor (which can be called the fourteenth resistor), which is electrically connected between the output of the comparator circuit 130 and the ground terminal. This pull-down circuit ensures that when the comparator circuit does not output a high-level signal, the signal connected to the chip (the chip connected to the output of the comparator circuit, for example, a control device) is a low-level signal. This reduces the occurrence of high-level interference signals at the output of the comparator circuit due to signal interference, making the signal more stable and improving the accuracy of power grid frequency detection.

[0106] Thus, a frequency sampling circuit according to some other embodiments of the present disclosure is provided. In addition to the isolation sampling circuit, operational amplifier circuit, and comparator circuit 130, this frequency sampling circuit may also include a filter circuit, a clamping circuit, and a pull-up or pull-down circuit, etc. By setting these circuits, signal interference can be reduced and the accuracy of power grid frequency detection can be improved.

[0107] In the above embodiments, the grid-side frequency is sampled by a circuit. Isolation devices are used to isolate the high-voltage side sampling signal from the low-voltage side to reduce signal interference. Operational amplifier circuits and clamping circuits are used to filter the signal again to improve the accuracy of the sampling signal.

[0108] Figure 4 This is a schematic block diagram illustrating the structure of a frequency detection apparatus according to some embodiments of the present disclosure.

[0109] like Figure 4 As shown, the frequency detection device includes a frequency sampling circuit 411. For example, this frequency sampling circuit can be the frequency sampling circuit described above (e.g., such as...). Figure 1 , Figure 2 or Figure 3 The frequency sampling circuit shown is configured to acquire the voltage signal of the power grid, and after isolation processing, differential amplification processing, and comparison processing, output the comparison result.

[0110] like Figure 4 As shown, the frequency detection device also includes a control device 420. The control device 420 is configured to receive comparison results from the frequency sampling circuit 411, record the number of comparison results within a predetermined time, and calculate the frequency of the power grid based on the predetermined time and the number of comparison results.

[0111] As mentioned earlier, the comparator circuit in the frequency sampling circuit can output a first-level signal or a second-level signal; for example, the first-level signal is a high-level signal, and the second-level signal is a low-level signal. When the control device receives the first-level signal from the comparator circuit in the frequency sampling circuit, the control device records it as receiving one comparison result. When the control device receives the second-level signal from the comparator circuit in the frequency sampling circuit, the control device records it as receiving another comparison result. Since the first voltage signal of the power grid is a sine wave signal, the third voltage signal input to the comparator circuit after passing through the isolation sampling circuit and the operational amplifier circuit is also a sine wave signal. Thus, when the comparator circuit compares the third voltage signal with the reference voltage signal, the output comparison result is an alternating high-level signal and a low-level signal; that is, the comparator circuit outputs a square wave signal. Therefore, every two consecutive comparison results recorded by the control device (i.e., a set of high-level signals and low-level signals) correspond to one cycle of the voltage signal in the power grid, thereby obtaining the frequency of the power grid.

[0112] Therefore, when calculating the frequency of the power grid, half of the number of recorded comparison results can be divided by a predetermined time. This yields the number of high and low level samples taken per unit time, which is the frequency of the power grid. For example, if 200 comparison results are recorded in 2 seconds, then half of 200 is the number of high and low level samples taken, which means 100 cycles of voltage signal are sampled. In other words, 100 cycles of voltage signal are sampled in 2 seconds. Thus, 100 / 2 = 50 cycles of voltage signal are sampled per unit time (1 second). Therefore, the frequency of the power grid is 50Hz.

[0113] Thus, a frequency detection apparatus according to some embodiments of the present disclosure is provided. The frequency detection apparatus includes: a frequency sampling circuit as described above; and a control device configured to receive comparison results from the frequency sampling circuit, record the number of comparison results within a predetermined time, and calculate the frequency of the power grid based on the predetermined time and the number of comparison results. In this frequency detection apparatus, comparison results are obtained by sampling through the frequency sampling circuit, and the number of comparison results is recorded by the control device within a predetermined time, thereby calculating the frequency of the power grid based on the predetermined time and the number of comparison results. Since the frequency sampling circuit includes the aforementioned isolation sampling circuit, operational amplifier circuit, and comparison circuit, this improves the accuracy of the calculated power grid frequency.

[0114] In some embodiments, the frequency detection device is applied to a generator system. For example, the generator system may be an air conditioning system, a centrifugal chiller system, or a photovoltaic system.

[0115] In some embodiments, the control device 420 may also be configured to determine that the generator system has not failed when the grid frequency is within a predetermined frequency range, and to determine that the generator system has failed when the grid frequency is outside the predetermined frequency range. This achieves fault detection of the generator system.

[0116] For example, the predetermined frequency range can be 49.5Hz to 50.2Hz. That is, if the grid frequency is greater than or equal to 49.5Hz and less than or equal to 50.2Hz, it is determined that the unit system has not experienced a fault; if the grid frequency is less than 49.5Hz or greater than 50.2Hz, it is determined that the unit system has experienced a fault.

[0117] It should be noted that the above-mentioned predetermined frequency range is merely exemplary, and the scope of this disclosure is not limited to the specific value of the predetermined frequency range.

[0118] For example, control device 420 can also be configured to control the normal operation of the unit system when it is determined that no fault has occurred in the unit system. For example, it can control the start-up of the centrifuge / screw chiller system, or control the start-up of the photovoltaic system, etc.

[0119] For example, control device 420 can also be configured to shut down the unit system upon determining that a fault has occurred. This reduces the damage to the unit system caused by the fault.

[0120] In some implementations, upon powering on the generator system, the system first checks if the grid frequency is normal. If normal, the centrifuge system or photovoltaic system can be started. If the grid is abnormal, the generator system will issue a fault alarm and prevent startup. When the centrifuge system or photovoltaic system is started, the grid frequency is checked. If normal, the generator operates normally; if abnormal, the centrifuge system or photovoltaic system shuts down. During frequency detection, the grid's UAB voltage (i.e., the voltage between UA and UB) is sampled, passed through an analog isolation device, amplified by an operational amplifier circuit, and then output as a high or low level signal by a comparator to the control device. The control device calculates the grid frequency based on the number of high and low level samples per unit time.

[0121] Figure 5 This is a schematic block diagram illustrating the structure of a converter according to some embodiments of the present disclosure. For example, the converter is a photovoltaic converter.

[0122] like Figure 5 As shown, the converter may include a rectifier 510. One side of the rectifier 510 is electrically connected to the power grid. Figure 5 The diagram shows the three-phase power supply of the grid (UA, UB, and UC). For example, a first set of switches QF1 can be installed between the rectifier 510 and the grid. The other side of the rectifier 510 is electrically connected to the inverter 520 and the photovoltaic power generation system (e.g., Figure 5 The diagram shows the positive voltage terminal PV+ and the negative voltage terminal PV- of a photovoltaic power generation system. The voltage terminals PV+ and PV- of this photovoltaic power generation system are electrically connected to the connection point between the rectifier 510 and the inverter 520. For example, a second set of switches QF2 can be installed between the voltage terminals PV+ and PV- of the photovoltaic power generation system and this connection point.

[0123] like Figure 5 As shown, the converter may also include an inverter 520. The inverter 520 is electrically connected to the electrical equipment. For example, the electrical equipment is a motor M. The motor M can be a motor of a centrifuge / screw compressor, etc.

[0124] like Figure 5 As shown, the converter may further include a first sampling circuit 410. The first sampling circuit 410 is electrically connected to the power grid. The first sampling circuit 410 includes a frequency sampling circuit 411. The frequency sampling circuit 411 is the frequency sampling circuit as described above.

[0125] like Figure 5As shown, the converter may also include a control device 420. The control device 420 is configured to receive comparison results from the frequency sampling circuit 411, record the number of comparison results within a predetermined time period, and calculate the grid frequency based on the predetermined time and the number of comparison results. The method for calculating the grid frequency based on the predetermined time and the number of comparison results has already been described above and will not be repeated here.

[0126] Thus, a converter according to some embodiments of the present disclosure is provided. The converter includes: a rectifier, one side of which is electrically connected to the power grid, and the other side of which is electrically connected to an inverter and a photovoltaic power generation system; an inverter electrically connected to electrical appliances; a first sampling circuit electrically connected to the power grid, the first sampling circuit including the frequency sampling circuit as described above; and a control device configured to receive comparison results from the frequency sampling circuit, record the number of comparison results within a predetermined time, and calculate the frequency of the power grid based on the predetermined time and the number of comparison results. In this converter, by providing a first sampling circuit including the frequency sampling circuit and a control device, the detection of the power grid frequency can be realized; moreover, since the frequency sampling circuit adopts the frequency sampling circuit as described above, which includes the isolation sampling circuit, operational amplifier circuit and comparison circuit described above, the accuracy of the calculated power grid frequency can be improved.

[0127] In some embodiments, such as Figure 5 As shown, the converter may further include a first drive circuit 531. The first drive circuit 531 is disposed between the control device 421 and the rectifier 510. The first drive circuit 531 is configured to receive a first control signal from the control device and control the rectifier 510 to turn on or off based on the first control signal. Here, the control device 420 is also configured to send the first control signal to the first drive circuit based on information collected by the first sampling circuit 410.

[0128] For example, the control device includes a first main control board 421. The first main control board 421 receives information collected by the first sampling circuit 410 and sends a first control signal to the first drive circuit based on this information to control the rectifier 510 to turn on or off. For example, the first main control board 421 can calculate the frequency of the power grid based on the comparison result sent by the frequency sampling circuit of the first sampling circuit, and determine whether the frequency of the power grid is within a predetermined frequency range. If the frequency of the power grid is within the predetermined frequency range, it is determined that the converter has not failed, and a first control signal can be sent to the first drive circuit to drive the rectifier to turn on; if the frequency of the power grid is outside the predetermined frequency range, it is determined that the converter has failed, and another first control signal can be sent to the first drive circuit to drive the rectifier to turn off.

[0129] Therefore, by setting up a first drive circuit, the control device can control the rectifier to turn on and off through the first drive circuit, thereby realizing the control of the entire converter and improving the safety of the system.

[0130] In some embodiments, such as Figure 5 As shown, the first sampling circuit 410 may further include a voltage sampling circuit. This voltage sampling circuit is configured to collect voltage information from the power grid and transmit the voltage information to a control device (e.g., a first main control board of the control device). The control device (e.g., the first main control board of the control device) is configured to determine, based on the voltage information from the power grid, whether the voltage of the power grid is within a predetermined voltage range (which may be referred to as a second predetermined voltage range). If the voltage of the power grid is within the predetermined voltage range, it is determined that the converter has not failed; otherwise, it is determined that the converter has failed. The control device (e.g., the first main control board of the control device) sends the aforementioned first control signal to the first drive circuit to control the rectifier's on or off state. This achieves the purpose of determining whether the system is faulty based on the power grid voltage, thereby controlling the rectifier and improving system safety.

[0131] For example, the aforementioned second predetermined voltage range can be from -418V to +418V. Of course, this is merely an example, and the scope of this disclosure is not limited to the specific value of the second predetermined voltage range. The second predetermined voltage range can be set according to actual circumstances or actual needs.

[0132] In some embodiments, such as Figure 5 As shown, the converter may also include a first current sensor CT1 and a second current sensor CT2. The first current sensor CT1 is used to collect the current signal in one wire of the power grid. The second current sensor CT2 is used to collect the current signal in another wire of the power grid.

[0133] like Figure 5 As shown, the first sampling circuit 410 may further include a current sampling circuit. The current sampling circuit is electrically connected to the first current sensor CT1 and the second current sensor CT2. The current sampling circuit is used to obtain the current values ​​of the two wires in the power grid and transmit the current values ​​to the control device 420 (e.g., the first main control board 421 in the control device 420).

[0134] The control device 420 (e.g., the first main control board 421 in the control device 420) can also be configured to send a first control signal to the first drive circuit based on the current value in the power grid to control the rectifier's on or off state. For example, the control device can be used to calculate the current value of the third wire in the power grid based on the current values ​​of the two wires in the power grid, and determine whether the converter has failed based on the current values ​​of the three wires in the power grid, thereby sending the first control signal to the first drive circuit. For example, the control device can be used to determine that the converter has not failed when the current values ​​of the three wires in the power grid are all within a first predetermined current range, and to determine that the converter has failed when the current value of at least one wire in the power grid is outside the first predetermined current range. This achieves the purpose of determining whether the system is faulty based on the current in the power grid, thereby controlling the rectifier and improving system safety.

[0135] For example, the first predetermined current range can be from 0 to 168.8A. It should be noted that the scope of this disclosure is not limited to the specific range of the first predetermined current range, and the specific value of the first predetermined current range can be set according to the actual situation or actual needs.

[0136] In some embodiments, such as Figure 5 As shown, the converter may further include a second sampling circuit 540. The second sampling circuit 540 is electrically connected to the inverter 520. The second sampling circuit 540 is configured to acquire the current signal output by the inverter and transmit it to the control device.

[0137] For example, a third current sensor CT3 can be installed on the first phase wire U of the inverter 520, and a fourth current sensor CT4 can be installed on the second phase wire W of the inverter 520. The third current sensor CT3 is used to collect the current signal in the first phase wire U and transmit it to the second sampling circuit. The fourth current sensor CT4 is used to collect the current signal in the second phase wire W and transmit it to the second sampling circuit. In this way, the second sampling circuit 540 can obtain the current signals in the two phase wires output by the inverter and transmit them to the control device.

[0138] like Figure 5 As shown, the converter may further include a second drive circuit 532. The second drive circuit 532 is disposed between the control device 420 and the inverter 520. The second drive circuit 532 is configured to receive a second control signal from the control device and control the inverter to turn on or off based on the second control signal.

[0139] The control device 420 can also be configured to send a second control signal to the second drive circuit 532 based on the current signal output by the inverter.

[0140] For example, the control device 420 may further include a second main control board 422. The second main control board 422 is configured to determine whether the current signal output by the inverter is within a second predetermined current range. If it is, it determines that the inverter has not failed; otherwise, it determines that the inverter has failed. For example, the second main control board 422 can determine the current value in the third phase wire V based on the current values ​​of the first phase wire U and the second phase wire W. If the current values ​​of all three phase wires are within the second predetermined current range, it determines that the inverter has not failed; if the current value of at least one of the three phase wires is outside the second predetermined current range, it determines that the inverter has failed. Furthermore, if it is determined that the inverter has not failed, the second main control board 422 can send a second control signal to the second drive circuit 532 to cause the second drive circuit to control the inverter to turn on; if it is determined that the inverter has failed, it can send another second control signal to the second drive circuit 532 to cause the second drive circuit to control the inverter to turn off. This achieves control of the inverter.

[0141] In the above embodiments, the control of the second sampling circuit, the second driving circuit and the control device enables the determination of whether the system is faulty based on the current signal output by the inverter, thereby controlling the inverter and improving the safety of the system.

[0142] For example, the second predetermined current range can be from 0 to 168.8A. It should be noted that the scope of this disclosure is not limited to the specific range of the second predetermined current range, and the specific value of the second predetermined current range can be set according to the actual situation or actual needs.

[0143] In some embodiments, in order to ensure that the centrifuge system does not feed DC bus power back to the grid side when the grid suddenly fails, a high-power variable frequency centrifuge grid-side overvoltage protection circuit can be set up. When the voltage at the front end of the centrifuge inverter is detected to be too high and the current direction is from the centrifuge to the grid, the rectifier / inverter module is quickly shut down and the capacitor on the DC bus is disconnected so that it cannot feed power back to the grid side.

[0144] In some embodiments, such as Figure 5 As shown, the converter may also include a fifth current sensor, CT5. This fifth current sensor is installed on the wire between the photovoltaic power generation system and the rectifier. This fifth current sensor is used to collect the current signal output by the photovoltaic power generation system. This achieves the detection of the current in the photovoltaic power generation system.

[0145] In summary, embodiments of this disclosure provide a converter. For example... Figure 5As shown, UA, UB, and UC represent the three-phase power from the grid side. This power is connected to the rectifier module (i.e., the rectifier) ​​via switch QF1 and current sensors CT1 and CT2. The rectifier module is then connected to the inverter module (i.e., the inverter) via the DC bus. The inverter module is connected to the motor M via current sensors CT3 and CT2. The first sampling circuit processes the front-end voltage and current signals and transmits them to the first main control board. The first main control board controls the rectifier module via the first drive circuit. The second sampling circuit samples the motor-side current and transmits it to the second main control board. The second main control board controls the inverter module via the second drive circuit. The photovoltaic (PV) photovoltaic array is connected to the inverter's DC bus via switch QF2 and current sensor CT5.

[0146] The circuits in the embodiments of this disclosure can reduce the problem of efficiency conversion and control of centrifuge / screw compressor operation affected by inaccurate grid frequency detection, improve the quality of grid-connected power during photovoltaic power generation, and provide timely protection against grid frequency fluctuations.

[0147] Figure 6 This is a schematic diagram illustrating the direction of current in photovoltaic power generation according to some embodiments of this disclosure. For example... Figure 6 As shown, the current output by the photovoltaic power generation system flows into the power grid through rectifier 510. Please refer to the current direction 601 in the figure.

[0148] Figure 7 This is a schematic diagram illustrating the direction of current in an electrical device according to some embodiments of the present disclosure when it is powered on. For example... Figure 7 As shown, when the photovoltaic power generation system supplies power to the electrical equipment, the current output by the photovoltaic power generation system flows into the electrical equipment through the inverter 520, as shown in the first current direction 701. When the power grid supplies power to the electrical equipment, the current output by the grid flows into the electrical equipment through the rectifier 510 and the inverter 520, as shown in the second current direction 702.

[0149] In the embodiments of this disclosure, when the unit is powered on, the converter collects the grid-side voltage signal and current signal through the first sampling circuit. When the frequency is normal, the unit can start the centrifuge / screw turbine system normally. Photovoltaic power is connected to the DC bus of the photovoltaic converter through switch QF2. When the centrifuge / screw turbine system is turned on, the photovoltaic power will prioritize the use of the centrifuge / screw turbine system. When there is surplus, it will generate electricity to the grid (for example, the photovoltaic power generation is greater than the power consumption of the centrifuge / screw turbine). Alternatively, if the centrifuge / screw turbine system is not turned on and only the photovoltaic power generation system is turned on, the photovoltaic power will be directly generated and connected to the grid through the converter.

[0150] In some embodiments of this disclosure, a unit system is also provided, which includes a converter as described above (e.g., such as...). Figure 5(The converter shown). For example, the unit system may include air conditioning equipment, centrifugal / screw chiller systems, or photovoltaic systems, etc.

[0151] Figure 8 This is a flowchart illustrating a frequency detection method according to some embodiments of the present disclosure. This frequency detection method can be executed by a control device. Figure 8 As shown, the frequency detection method includes steps S810 to S820.

[0152] In step S810, the comparison result is received from the frequency sampling circuit, and the number of comparison results within a predetermined time period is recorded.

[0153] In step S820, the frequency of the power grid is calculated based on the predetermined time and the number of comparison results.

[0154] For example, when calculating the frequency of the power grid, one can divide half of the number of recorded comparison results by a predetermined time to obtain the number of high and low level samples per unit time, which is the frequency of the power grid.

[0155] Thus, a frequency detection method according to some embodiments of the present disclosure is provided. The frequency detection method includes: receiving comparison results from a frequency sampling circuit and recording the number of comparison results within a predetermined time; and calculating the frequency of the power grid based on the predetermined time and the number of comparison results. This achieves the detection of the power grid frequency, thereby enabling corresponding control based on the power grid frequency.

[0156] In some embodiments, the frequency detection method further includes: determining that the generating system has not failed when the grid frequency is within a predetermined frequency range; and determining that the generating system has failed when the grid frequency is outside the predetermined frequency range. This achieves the purpose of determining whether a system has failed based on the grid frequency, thereby facilitating the execution of corresponding processing and improving system security.

[0157] For example, if it is determined that the unit system is not faulty, the unit system can be started up or allowed to operate normally; if it is determined that the unit system is faulty, the unit can be shut down. This improves the safety of the system.

[0158] Figure 9 This is a structural block diagram illustrating a control device according to some embodiments of the present disclosure. The control device includes a memory 910 and a processor 920. Wherein:

[0159] The memory 910 can be a disk, flash memory, or any other non-volatile storage medium. The memory is used for storage. Figure 8 The instructions in the corresponding embodiment.

[0160] Processor 920 is coupled to memory 910 and can be implemented as one or more integrated circuits, such as a microprocessor or microcontroller. Processor 920 executes instructions stored in memory, enabling detection of the power grid frequency and allowing for corresponding control based on the power grid frequency.

[0161] In one embodiment, it can also be as follows: Figure 10 As shown, the control device 1000 includes a memory 1010 and a processor 1020. The processor 1020 is coupled to the memory 1010 via a BUS bus 1030. The control device 1000 can also be connected to an external storage device 1050 via a storage interface 1040 to access external data, and can also be connected to a network or another computer system (not shown) via a network interface 1060, which will not be described in detail here.

[0162] In this embodiment, data instructions are stored in a memory and then processed by a processor to achieve power grid frequency detection, thereby enabling corresponding control based on the power grid frequency.

[0163] In another embodiment, this disclosure also provides a computer-readable storage medium (e.g., a non-transitory computer-readable storage medium) having stored thereon computer program instructions that, when executed by a processor, are implemented. Figure 8 The steps of the method in the corresponding embodiments are described. Those skilled in the art will understand that embodiments of this disclosure can be provided as methods, apparatus, or computer program products. Therefore, this disclosure can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this disclosure can take the form of a computer program product embodied on one or more computer-usable non-transitory storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0164] This disclosure is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this disclosure. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create a machine for implementing the flowchart illustrations. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0165] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0166] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0167] In some embodiments of this disclosure, a computer program product is also provided, which includes a computer program or instructions that, when executed by a processor, implement the frequency detection method as described above.

[0168] In some embodiments of this disclosure, a computer program is also provided, comprising: instructions that, when executed by a processor, cause the processor to perform the frequency detection method as described above.

[0169] This concludes the detailed description of the present disclosure. To avoid obscuring the concept of the disclosure, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions disclosed herein based on the above description.

[0170] While specific embodiments of this disclosure have been described in detail by way of example, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of this disclosure. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this disclosure. The scope of this disclosure is defined by the appended claims.

Claims

1. A frequency sampling circuit, comprising: an isolated sampling circuit, configured to receive a first voltage signal from a power grid, and output a second voltage signal in response to the first voltage signal, wherein a voltage value of the second voltage signal is smaller than a voltage value of the first voltage signal, and the second voltage signal includes a first sub-voltage signal and a second sub-voltage signal; an operational amplifier circuit configured to receive the first sub-voltage signal and the second sub-voltage signal, and perform differential amplification processing on the first sub-voltage signal and the second sub-voltage signal to output a third voltage signal; and The comparison circuit is configured to receive a third voltage signal and compare the third voltage signal with a reference voltage signal to output a comparison result.

2. The frequency sampling circuit according to claim 1, wherein: The isolation sampling circuit comprises: A first resistor and a second resistor are connected in series between a first voltage terminal and a second voltage terminal of the power grid; an isolation device, wherein a first input terminal of the isolation device is electrically connected to a first end of the second resistor, a second input terminal of the isolation device is electrically connected to a second end of the second resistor, a first output terminal of the isolation device is electrically connected to a first input terminal of the operational amplifier circuit, and a second output terminal of the isolation device is electrically connected to a second input terminal of the operational amplifier circuit.

3. The frequency sampling circuit according to claim 2, wherein: The operational amplifier circuit comprises: a differential operational amplifier, wherein a first input terminal of the differential operational amplifier is electrically connected to a first output terminal of the isolation device, a second input terminal of the differential operational amplifier is electrically connected to a second output terminal of the isolation device, and an output terminal of the differential operational amplifier is electrically connected to a first input terminal of the comparison circuit; A third resistor is arranged between the second input terminal of the differential operational amplifier and the second output terminal of the isolation device; a fourth resistor, arranged between the first input terminal of the differential operational amplifier and the first output terminal of the isolation device; a fifth resistor electrically connected between the first input terminal of the differential operational amplifier and a ground terminal; and A sixth resistor is electrically connected between the second input terminal of the differential operational amplifier and the output terminal of the differential operational amplifier.

4. The frequency sampling circuit according to claim 3, wherein: The resistance value of the third resistor is equal to the resistance value of the fourth resistor, the resistance value of the fifth resistor is equal to the resistance value of the sixth resistor, and the ratio of the resistance value of the fourth resistor to the resistance value of the fifth resistor is a predetermined ratio.

5. The frequency sampling circuit according to claim 3, wherein: The operational amplifier circuit further includes: A first capacitor, electrically connected between the first input terminal of the differential operational amplifier and a ground terminal; The second capacitor is electrically connected between the second input terminal of the differential operational amplifier and the output terminal of the differential operational amplifier.

6. The frequency sampling circuit according to claim 1, wherein: The comparison circuit comprises: A comparator, wherein a first input terminal of the comparator is electrically connected to an output terminal of the operational amplifier circuit, a second input terminal of the comparator is configured to receive the reference voltage signal, and an output terminal of the comparator is configured to output the comparison result.

7. The frequency sampling circuit according to claim 6, wherein: The comparison circuit further comprises: A seventh resistor and an eighth resistor are connected in series between the power supply voltage terminal and the ground terminal; The second input terminal of the comparator is electrically connected to a connection point between the seventh resistor and the eighth resistor.

8. The frequency sampling circuit according to claim 1, further comprising: The filter circuit is arranged between the operational amplifier circuit and the comparison circuit, and is configured to perform filter processing on the third voltage signal.

9. The frequency sampling circuit according to claim 8, wherein: The filtering circuit comprises: a ninth resistor and a third capacitor, electrically connected between the output terminal of the operational amplifier circuit and the first input terminal of the comparison circuit; a tenth resistor, wherein a first end of the tenth resistor is electrically connected to a connection point between the ninth resistor and the third capacitor, and a second end of the tenth resistor is electrically connected to a ground terminal.

10. The frequency sampling circuit according to claim 1, further comprising: The clamping circuit is arranged between the operational amplifier circuit and the comparison circuit, and is configured to clamp the third voltage signal so that the third voltage signal is within a predetermined voltage range.

11. The frequency sampling circuit according to claim 10, wherein: The clamping circuit comprises: An eleventh resistor and a twelfth resistor are connected in series between a power supply voltage terminal and a ground terminal, wherein a connection point between the eleventh resistor and the twelfth resistor is electrically connected to a first input terminal of the comparison circuit.

12. The frequency sampling circuit according to claim 1, further comprising: The pull-up circuit or the pull-down circuit is arranged at the output end of the comparison circuit.

13. A frequency detection device, comprising: The frequency sampling circuit according to any one of claims 1 to 12; and The control device is configured to receive the comparison result from the frequency sampling circuit, record the number of the comparison results within a predetermined time, and calculate the frequency of the power grid based on the predetermined time and the number of the comparison results.

14. The frequency detection device according to claim 13, wherein: The frequency detection device is applied to a unit system; The control device is further configured to determine that the unit system has not failed when the frequency of the power grid is within a predetermined frequency range, and to determine that the unit system has failed when the frequency of the power grid is outside the predetermined frequency range.

15. A converter, comprising: A rectifier, one side of the rectifier is electrically connected to the power grid, and the other side of the rectifier is electrically connected to the inverter and the photovoltaic power generation system; The inverter is electrically connected to the power-consuming equipment; A first sampling circuit, electrically connected to the power grid, the first sampling circuit comprising the frequency sampling circuit according to any one of claims 1 to 12; and The control device is configured to receive the comparison result from the frequency sampling circuit, record the number of the comparison results within a predetermined time, and calculate the frequency of the power grid based on the predetermined time and the number of the comparison results.

16. The converter according to claim 15, further comprising: A first drive circuit is provided between the control device and the rectifier, and is configured to receive a first control signal from the control device, and control the on or off of the rectifier based on the first control signal; Wherein, the control device is further configured to send the first control signal to the first driving circuit based on the information collected by the first sampling circuit.

17. The converter according to claim 15, further comprising: a second sampling circuit, electrically connected to the inverter, configured to collect a current signal output by the inverter and transmit the current signal to the control device; a second drive circuit, disposed between the control device and the inverter, configured to receive a second control signal from the control device, and control the on or off of the inverter based on the second control signal; Wherein, the control device is further configured to send the second control signal to the second drive circuit based on the current signal output by the inverter.

18. A unit system, comprising: A converter as claimed in any one of claims 15 to 17.

19. A frequency detection method implemented based on the frequency sampling circuit according to any one of claims 1 to 12, comprising: receiving the comparison results from the frequency sampling circuit and recording the number of the comparison results within a predetermined time; and The frequency of the power grid is calculated based on the predetermined time and the number of the comparison results.

20. The frequency detection method according to claim 19, further comprising: When the frequency of the power grid is within a predetermined frequency range, determining that no fault occurs in the unit system; and When the frequency of the power grid is outside a predetermined frequency range, it is determined that a fault occurs in the unit system.

21. A control device comprising: Memory; as well as A processor coupled to the memory, wherein the processor is configured to execute the frequency detection method according to claim 19 or 20 based on instructions stored in the memory.

22. A computer-readable storage medium having computer instructions stored thereon, wherein the computer instructions are executed by a processor to implement the frequency detection method according to claim 19 or 20.

23. A computer program product, comprising a computer program or instructions, which implement the frequency detection method according to claim 19 or 20 when executed by a processor.

Images