A sampling circuit and a photovoltaic power system
By introducing an isolation module into the photovoltaic power system, and using linear optocouplers and voltage divider circuits to isolate the voltage of the photovoltaic power generation device and the DC/DC converter, the safety problem caused by the rise in bus voltage is solved, and the safety and stability of the system are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GREE ELECTRIC APPLIANCE INC OF ZHUHAI
- Filing Date
- 2022-09-29
- Publication Date
- 2026-07-17
AI Technical Summary
In existing photovoltaic power systems, the establishment of DC bus voltage leads to an increase in the output voltage of photovoltaic power generation devices, which affects system safety.
In a photovoltaic power system, first and second isolation modules are introduced, located between the photovoltaic power generation device and the positive terminal of the DC/DC converter, respectively. Voltage isolation is achieved through linear optocouplers and voltage divider circuits to avoid the influence of bus voltage on photovoltaic voltage.
It effectively reduces the impact of bus voltage on photovoltaic voltage, improves system safety, prevents malfunctions, and ensures personal safety.
Smart Images
Figure CN115567056B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electronic power technology, and more specifically, to a sampling circuit and a photovoltaic power system. Background Technology
[0002] In recent years, solar energy has been widely used as a clean and renewable energy source. Before the inverter converts direct current (DC) to alternating current (AC) for grid connection, a DC / DC converter is needed to optimize the photovoltaic output voltage so that the photovoltaic power generation device reaches its maximum power point. Therefore, the DC / DC converter is a very important part of grid connection.
[0003] However, in actual testing, it was found that when the DC / DC converter circuit is in standby mode, that is, when only weak power is supplied, once the bus voltage is established, even if the photovoltaic power generation device is not connected, its output voltage will increase to a certain extent, about 100-200V. Therefore, the DC bus voltage will not only affect the actual sampled value of the photovoltaic voltage, but may also cause circuit malfunctions, posing a threat to personal safety.
[0004] There is currently no effective solution to the problem that the establishment of DC bus voltage in existing photovoltaic power systems leads to an increase in the output voltage of photovoltaic power generation devices, which affects the safety of the photovoltaic power system. Summary of the Invention
[0005] This invention provides a sampling circuit and a photovoltaic power system to solve the problem that, in the prior art, the output voltage of the photovoltaic power generation device increases after the DC bus voltage of the photovoltaic power system is established, which affects the safety of the photovoltaic power system.
[0006] To address the aforementioned technical problems, this invention provides a sampling circuit applied to a photovoltaic power system, the circuit comprising:
[0007] The first isolation module is connected between the positive terminal and the negative terminal of the photovoltaic power generation device in the photovoltaic power system, and is used to isolate the photovoltaic power generation device from the first sampling module; wherein, the first sampling module is used to collect the photovoltaic power generation voltage;
[0008] The second isolation module is connected between the positive terminal and the negative terminal of the DC / DC converter of the photovoltaic power system, and is used to isolate the DC / DC converter from the second sampling module; wherein, the second sampling module is used to collect the DC bus voltage.
[0009] Furthermore, the first isolation module includes:
[0010] The voltage divider unit has its first end connected to the positive terminal of the photovoltaic power generation device, its second end connected to the negative terminal of the photovoltaic power generation device, and its third end connected to the second pin of the linear optocoupler.
[0011] The linear optocoupler has its first pin connected to a first voltage source, its third and fourth pins both connected to the second end of the voltage divider unit, its fifth pin grounded, its sixth and seventh pins connected to the first sampling module, and its eighth pin connected to a second voltage source.
[0012] Furthermore, the voltage divider unit includes:
[0013] A first resistor and a second resistor are connected in series. The first resistor is connected to the positive terminal of the photovoltaic power generation device, and the second resistor is connected to the negative terminal of the photovoltaic power generation device. The line between the first resistor and the second resistor is connected to the second pin of the linear optocoupler.
[0014] Furthermore, the voltage divider unit also includes:
[0015] The first capacitor is connected in parallel across the second resistor.
[0016] Furthermore, the second isolation module has the same internal circuit structure as the first isolation module.
[0017] Furthermore, the first sampling module includes:
[0018] The operational amplifier has its inverting input connected to the sixth pin of the linear optocoupler in the first isolation module via a third resistor, its non-inverting input connected to the seventh pin of the linear optocoupler via a fourth resistor, its non-inverting input grounded via a fifth resistor, and its output connected to its own inverting input via a sixth resistor.
[0019] Furthermore, the first sampling module also includes:
[0020] The second capacitor has its first end connected to the negative power supply of the operational amplifier, and its second end grounded.
[0021] Furthermore, the first sampling module also includes:
[0022] The third capacitor is connected in parallel across the sixth resistor.
[0023] Furthermore, the structure of the second sampling module is the same as the internal circuit structure of the first sampling module.
[0024] The present invention also provides a photovoltaic power system, including the above-described sampling circuit.
[0025] By applying the technical solution of this invention, a first isolation module and a second isolation module are added to the existing sampling circuit structure of a photovoltaic power system. The first isolation module is set between the photovoltaic power generation device and the photovoltaic voltage sampling module, and the second isolation module is set between the DC / DC converter and the bus voltage sampling module. This is used to isolate the photovoltaic power generation device side and the DC / DC converter side, prevent the photovoltaic voltage from increasing with the DC bus voltage, and improve the safety of the photovoltaic power system. Attached Figure Description
[0026] Figure 1 This is a structural block diagram of the sampling circuit according to an embodiment of the present invention;
[0027] Figure 2 This is a structural diagram of the first isolation module according to an embodiment of the present invention;
[0028] Figure 3 This is a diagram showing the internal circuit structure of a linear optocoupler according to an embodiment of the present invention;
[0029] Figure 4 This is a structural diagram of the second isolation module according to an embodiment of the present invention. Detailed Implementation
[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0031] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, and “multiple” generally includes at least two unless the context clearly indicates otherwise.
[0032] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.
[0033] It should be understood that although the terms first, second, third, etc., may be used to describe resistors in the embodiments of the present invention, these resistors should not be limited to these terms. These terms are only used to distinguish different resistors. For example, without departing from the scope of the embodiments of the present invention, a first resistor may also be referred to as a second resistor, and similarly, a second resistor may also be referred to as a first resistor.
[0034] Depending on the context, the words “if” or “suppose” as used here can be interpreted as “when” or “in response to determination” or “in response to detection.” Similarly, depending on the context, the phrases “if determination” or “if detection (of the stated condition or event)” can be interpreted as “when determination” or “in response to determination” or “when detection (of the stated condition or event)” or “in response to detection (of the stated condition or event).”
[0035] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device that includes said element.
[0036] The optional embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0037] Example 1
[0038] This embodiment provides a sampling circuit applied to a photovoltaic power system. In existing photovoltaic power systems, in the DC / DC converter circuit design, the high-voltage reference ground of the photovoltaic power generation device and the DC / DC converter is usually on the same network. The sampling circuits of both use a non-isolated differential sampling method, and their reference grounds are also consistent. Therefore, the photovoltaic power generation device and the DC / DC converter are indirectly connected through the sampling circuit. During actual operation, the DC / DC converter needs to first stabilize the bus at a fixed value before connecting the photovoltaic power generation device for step-up / step-down voltage conversion. Once the DC bus voltage on the output side of the DC / DC converter is established, the capacitor C1 on the photovoltaic power generation device side is slowly charged through the second sampling module and the first sampling module. The higher the DC bus voltage on the output side of the DC / DC converter, the higher the output voltage of the photovoltaic power generation device will rise. The DC bus voltage not only affects the actual sampled value of the photovoltaic voltage but may also cause circuit malfunctions, posing a threat to personal safety. A capacitor C2 is also provided on the output side of the DC / DC converter.
[0039] Figure 1This is a structural block diagram of the sampling circuit according to an embodiment of the present invention, such as... Figure 1 As shown, the photovoltaic power generation voltage and DC bus voltage are acquired through the first sampling module 20 and the second sampling module 40. To solve the above problems, the sampling circuit further includes: a first isolation module 10, connected between the positive terminal PV+ and the negative terminal PV- of the photovoltaic power generation device in the photovoltaic power system, used to isolate the photovoltaic power generation device from the first sampling module 20; the input terminal of the first sampling module 20 is connected to the first isolation module 10, and its output terminal outputs the photovoltaic power generation voltage sampling signal V_PV; a second isolation module 30, connected between the positive terminal DC+ and the negative terminal DC- of the DC / DC converter in the photovoltaic power system, used to isolate the DC / DC converter from the second sampling module 40; the input terminal of the second sampling module 40 is connected to the second isolation module 30, and its output terminal outputs the bus voltage sampling signal V_DC.
[0040] The sampling circuit of this embodiment adds a first isolation module 10 and a second isolation module 30 to the existing sampling circuit structure of the photovoltaic power system. The first isolation module 10 is located between the photovoltaic power generation device and the first sampling module 20, and the second isolation module 30 is located between the DC / DC converter and the second sampling module 40. This is used to isolate the photovoltaic power generation device side and the DC / DC converter side, prevent the photovoltaic voltage from increasing with the DC bus voltage, and improve the safety of the photovoltaic power system.
[0041] Figure 2 This is a structural diagram of the first isolation module according to an embodiment of the present invention, as shown below. Figure 2 As shown, in order to achieve isolation, the first isolation module 10 includes: a voltage divider unit, the first end of which is connected to the positive terminal PV+ of the photovoltaic power generation device, the second end of which is connected to the negative terminal PV- of the photovoltaic power generation device, and the third end of which is connected to the second pin 2 of the linear optocoupler U; the linear optocoupler U, the first pin 1 of which is connected to a first voltage source, the voltage provided by the first voltage source can be 5V, which is the power supply voltage of the linear optocoupler, the third pin 3 and the fourth pin 4 of which are both connected to the second end of the voltage divider unit, the fifth pin 5 of which is grounded, the sixth pin 6 and the seventh pin 7 of which are connected to the first sampling module 20, and the eighth pin 8 of which is connected to the second voltage source Vcc.
[0042] To convert the photovoltaic power generation voltage to a lower voltage, the voltage divider unit includes a first resistor R1 and a second resistor R2 connected in series. The first resistor R1 is connected to the positive terminal PV+ of the photovoltaic power generation device, and the second resistor R2 is connected to the negative terminal PV- of the photovoltaic power generation device. The line between the first resistor R1 and the second resistor R2 is connected to the second pin 2 of the linear optocoupler U. The first resistor R1 and the second resistor R2 achieve the voltage divider function. The first resistor R1 can be a single resistor or multiple resistors R11, R12, and R13 connected in series.
[0043] To achieve the filtering effect, the voltage divider unit further includes a first capacitor C3, which is connected in parallel across the second resistor R2.
[0044] As mentioned above Figure 2 As shown, the first sampling module includes: an operational amplifier A, whose inverting input terminal is connected to the sixth pin 6 of the linear optocoupler U in the first isolation module through a third resistor R3, its non-inverting input terminal is connected to the seventh pin 7 of the linear optocoupler U through a fourth resistor R4, its non-inverting input terminal is also grounded through a fifth resistor R5, and its output terminal is connected to its own inverting input terminal through a sixth resistor R6.
[0045] like Figure 2 As shown, the first sampling module further includes a second capacitor C4, whose first end is connected to the negative power supply of operational amplifier A, and whose second end is grounded, for the purpose of filtering.
[0046] The first sampling module 20 also includes a third capacitor C5, which is connected in parallel across the sixth resistor R6 to achieve a filtering effect.
[0047] Figure 3 This is a diagram of the internal circuit structure of a linear optocoupler according to an embodiment of the present invention, such as... Figure 3 As shown, after the first pin 1 of the linear optocoupler is connected to the power supply, the LED conducts. The second pin 2 and the third pin 3 are connected to the sampling signal. After the LED conducts, the output signals from the sixth pin 6 and the seventh pin 7 are linear with the input signals from the second pin 2 and the third pin 3. When a power signal is applied to the input terminal, the LED emits light, which shines on the photodetector. After the photodetector receives the light, it conducts, generating a photocurrent that is output from the output terminal, thus realizing the "electric-optical-electric" conversion.
[0048] Figure 4 This is a structural diagram of the second isolation module according to an embodiment of the present invention, as shown below. Figure 4As shown, the second isolation module 30 has the same internal circuit structure as the first isolation module 10. The only difference is that the second pin 2 of the second isolation module 30 is connected to the positive terminal DC+ of the DC / DC converter through the first resistor R1, and the third pin 3 and the fourth pin 4 of the second isolation module 30 are connected to the negative terminal DC- of the DC / DC converter. The structure of the second sampling module 40 is the same as the internal circuit structure of the first sampling module 20. The only difference is that the output signal of the second sampling module 40 is the DC bus voltage sampling signal V_DC.
[0049] In summary, this embodiment adds an isolation module (linear optocoupler) to the existing sampling circuit to sample the photovoltaic and bus-side voltages. The isolation module is located at the rear end of the voltage divider on the photovoltaic or bus side, inputting the divided small voltage to the input terminal of the linear optocoupler. Its output terminal outputs a voltage value linearly related to the input. The front and rear ends of the linear optocoupler are independent, effectively reducing interference from the high-voltage side to the low-voltage side. Simultaneously, since the photovoltaic and bus ends are isolated from the sampling modules at the rear end using linear optocouplers, their coupling is also lost, significantly reducing the influence between the photovoltaic and bus ends. This prevents the bus side from using the "virtual short" characteristic of the operational amplifier to charge the photovoltaic-side capacitor C1. This solves the problem of the photovoltaic-side voltage rising after the bus voltage is established when the DC / DC converter is not operating. It avoids the influence of the bus voltage on the photovoltaic-side voltage, ensuring the normal operation of the photovoltaic power system and protecting the safety of testing personnel.
[0050] Example 3
[0051] The present invention also provides a photovoltaic power system, including the sampling circuit in the above embodiments, for preventing the photovoltaic voltage from increasing with the DC bus voltage, thereby improving the safety of the photovoltaic power system.
[0052] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.
[0053] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.
[0054] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A sampling circuit applied to a photovoltaic power system, characterized in that, The circuit includes: The first isolation module is connected between the positive terminal and the negative terminal of the photovoltaic power generation device in the photovoltaic power system, and is used to isolate the photovoltaic power generation device from the first sampling module; wherein, the input terminal of the first sampling module is connected to the first isolation module, and the output terminal of the first sampling module outputs a photovoltaic power generation voltage sampling signal for collecting photovoltaic power generation voltage; The second isolation module is connected between the positive terminal and the negative terminal of the DC / DC converter of the photovoltaic power system, and is used to isolate the DC / DC converter from the second sampling module; wherein, the input terminal of the second sampling module is connected to the second isolation module, and the output terminal of the second sampling module outputs a bus voltage sampling signal for acquiring DC bus voltage; The first isolation module includes: The voltage divider unit has its first end connected to the positive terminal of the photovoltaic power generation device, its second end connected to the negative terminal of the photovoltaic power generation device, and its third end connected to the second pin of the linear optocoupler. The linear optocoupler has its first pin connected to a first voltage source, its third and fourth pins both connected to the second end of the voltage divider unit, its fifth pin grounded, its sixth and seventh pins connected to the first sampling module, and its eighth pin connected to a second voltage source.
2. The circuit according to claim 1, characterized in that, The voltage divider unit includes: A first resistor and a second resistor are connected in series. The first resistor is connected to the positive terminal of the photovoltaic power generation device, and the second resistor is connected to the negative terminal of the photovoltaic power generation device. The line between the first resistor and the second resistor is connected to the second pin of the linear optocoupler.
3. The circuit according to claim 2, characterized in that, The voltage divider unit further includes: The first capacitor is connected in parallel across the second resistor.
4. The circuit according to claim 1, characterized in that, The second isolation module has the same internal circuit structure as the first isolation module.
5. The circuit according to claim 1, characterized in that, The first sampling module includes: The operational amplifier has its inverting input connected to the sixth pin of the linear optocoupler in the first isolation module via a third resistor, its non-inverting input connected to the seventh pin of the linear optocoupler via a fourth resistor, its non-inverting input grounded via a fifth resistor, and its output connected to its own inverting input via a sixth resistor.
6. The circuit according to claim 5, characterized in that, The first sampling module further includes: The second capacitor has its first end connected to the negative power supply of the operational amplifier, and its second end grounded.
7. The circuit according to claim 5, characterized in that, The first sampling module further includes: The third capacitor is connected in parallel across the sixth resistor.
8. The circuit according to claim 5, characterized in that, The structure of the second sampling module is the same as the internal circuit structure of the first sampling module.
9. A photovoltaic power system, characterized in that, The sampling circuit includes any one of claims 1 to 8.