Intelligent photovoltaic shutdown

Abstract

The application discloses an intelligent photovoltaic shutdown device, which comprises a photovoltaic assembly, a PLC demodulation circuit, a switch tube driving circuit, a first coupling capacitor, a second coupling capacitor, a first switch tube, a bypass diode and a load resistor; the source electrode of the first switch tube is connected with the negative electrode of the photovoltaic assembly; the drain electrode of the first switch tube is connected with the anode of the bypass diode; the gate electrode of the first switch tube is electrically connected with the switch tube driving circuit; the first end of the second coupling capacitor is connected with the positive electrode of the photovoltaic assembly; the second end of the second coupling capacitor is electrically connected with the PLC demodulation circuit; the first end of a capacitor is connected with the source electrode of the first switch tube; the second end of the capacitor is connected with the drain electrode of the first switch tube; the cathode of the bypass diode is connected with the positive electrode of the photovoltaic assembly; the first end of the load resistor is connected with the drain electrode of the first switch tube; and the second end of the load resistor is connected with the positive electrode of the photovoltaic assembly. The application discloses a photovoltaic shutdown device structure based on power line carrier communication, which has simple structure and low cost.

Description

Technical Field

[0001] This invention relates to the field of distributed photovoltaic technology, and more specifically to an intelligent photovoltaic shut-off device. Background Technology

[0002] Solar energy is gaining increasing attention as a clean energy source. With the further reduction in the cost of photovoltaic power generation, the installed capacity of photovoltaic power generation is also showing an explosive growth trend.

[0003] Currently, photovoltaic (PV) power generation systems generally adopt a string structure. The series connection of PV modules generates a high-voltage DC current of thousands of volts, posing a safety risk to personnel during maintenance and firefighting operations. Therefore, some countries and regions have introduced relevant standards requiring PV power generation systems to support module-level rapid shutdown functions to prevent high DC voltage during firefighting and maintenance, thus eliminating safety hazards.

[0004] To achieve module-level shutdown functionality, the shutdown device needs communication capabilities to receive on / off signals. Power line carrier communication (PLC) is widely used in photovoltaic (PV) module shutdown devices because it requires no additional wiring. In existing PV module shutdown technologies (such as CN212367219U), an inductor is connected in series in the PV DC circuit to provide AC impedance for the PLC demodulation circuit, facilitating the coupling of the carrier signal. However, as the power output of individual PV modules increases, the string current in the PV string also increases. Furthermore, the series inductor itself has a certain DC resistance, and under high current, it consumes significant power and generates heat. For example, when the string current is 20A and the DC resistance of the series inductor is 5mΩ, the series inductor will consume 2W of power. This results in heat not dissipating easily in the confined space of the PV junction box, and the 2W of power will cause high temperatures inside the junction box, accelerating the aging and cracking of the plastic junction box and adhesive, posing a safety hazard. Meanwhile, high-rated-current inductors are expensive and costly, which hinders the promotion of photovoltaic junction boxes.

[0005] Therefore, how to overcome the shortcomings of the existing technology is the subject of this invention. Summary of the Invention

[0006] The purpose of this invention is to provide an intelligent photovoltaic shutdown device.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A smart photovoltaic shut-off device includes a photovoltaic module, a PLC demodulation circuit, a switching transistor drive circuit, a first coupling capacitor, a second coupling capacitor, a first switching transistor, a bypass diode, and a load resistor.

[0009] Wherein, the source of the first switching transistor is connected to the negative terminal of the photovoltaic module, the drain of the first switching transistor is connected to the anode of the bypass diode, and the gate of the first switching transistor is electrically connected to the switching transistor driving circuit.

[0010] The PLC demodulation circuit is electrically connected to the switching transistor drive circuit;

[0011] The first end of the first coupling capacitor is connected to the source of the first switching transistor, and the second end of the first coupling capacitor is connected to the drain of the first switching transistor.

[0012] The first end of the second coupling capacitor is connected to the positive terminal of the photovoltaic module, and the second end of the second coupling capacitor is electrically connected to the PLC demodulation circuit.

[0013] The cathode of the bypass diode is connected to the positive electrode of the photovoltaic module;

[0014] The first end of the load resistor is connected to the drain of the first switching transistor, and the second end of the load resistor is connected to the positive terminal of the photovoltaic module.

[0015] The relevant content in the above technical solution is explained as follows:

[0016] 1. The above scheme also includes a second switch, which is turned on when the first switch is turned off;

[0017] The source of the second switching transistor is connected to the drain of the first switching transistor, the drain of the second switching transistor is connected to the positive terminal of the photovoltaic module, and the gate of the second switching transistor is electrically connected to the PLC demodulation module.

[0018] 2. In the above scheme, the photovoltaic module includes a solar panel, parasitic capacitance, resistor, and parasitic inductance;

[0019] The resistor is connected in series with the parasitic inductance, and one end of the resistor is connected to the positive terminal of the solar panel; one end of the parasitic capacitance is connected to the positive terminal of the solar panel, and the other end is connected to the negative terminal of the solar panel.

[0020] The working principle and advantages of this invention are as follows:

[0021] This invention discloses an intelligent photovoltaic (PV) switch, comprising a PV module, a PLC demodulation circuit, a switching transistor drive circuit, a first coupling capacitor, a second coupling capacitor, a first switching transistor, a bypass diode, and a load resistor. The source of the first switching transistor is connected to the negative terminal of the PV module, the drain of the first switching transistor is connected to the anode of the bypass diode, and the gate of the first switching transistor is electrically connected to the switching transistor drive circuit. The first terminal of the second coupling capacitor is connected to the positive terminal of the PV module, and the second terminal of the second coupling capacitor is electrically connected to the PLC demodulation circuit. The first terminal of the first coupling capacitor is connected to the source of the first switching transistor, and the second terminal of the first coupling capacitor is connected to the drain of the first switching transistor. The cathode of the bypass diode is connected to the positive terminal of the PV module. The first terminal of the load resistor is connected to the drain of the first switching transistor, and the second terminal of the load resistor is connected to the positive terminal of the PV module.

[0022] Compared to existing technologies, this invention proposes a simple and low-cost photovoltaic turn-off structure based on power line carrier communication. This invention utilizes the parasitic inductance of the photovoltaic module itself as the carrier signal load, significantly simplifying the carrier signal sampling and coupling circuit and reducing costs compared to existing technologies. Simultaneously, it avoids the safety hazards caused by heating of the series inductor under high current, thus improving the reliability of the turn-off device. Attached Figure Description

[0023] Appendix Figure 1 This is a schematic diagram of a PLC coupling circuit in the prior art;

[0024] Appendix Figure 2 This is a schematic diagram of the circuit structure according to an embodiment of the present invention;

[0025] Appendix Figure 3 This is a schematic diagram of the circuit structure of a photovoltaic module according to an embodiment of the present invention;

[0026] Appendix Figure 4 This is a typical frequency response curve of a photovoltaic module according to an embodiment of the present invention.

[0027] In the above figures: 101. Photovoltaic module; 102. Switching transistor drive circuit; 103. PLC demodulation circuit; 104. First coupling capacitor; 105. Second coupling capacitor; 106. First switching transistor; 107. Bypass diode; 108. Load resistor; 109. Second switching transistor; PS. Solar panel; Cp. Parasitic capacitance; Rs. Resistor; Lp. Parasitic inductance. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0029] Example: The present invention will be clearly described below with illustrations and detailed description. Any person skilled in the art who understands the examples of the present invention can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0030] The terminology used herein is for the purpose of describing specific embodiments only and is not intended to limit the scope of this work. Singular forms such as “a,” “this,” “this,” “the,” and “the” as used herein also include plural forms.

[0031] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0032] The terms “include,” “including,” and “have” used in this article are all open-ended, meaning they include but are not limited to.

[0033] Unless otherwise specified, the terms used herein generally have their ordinary meaning in the context of the art, the subject matter, and the specific context. Certain terms used to describe this case will be discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the case.

[0034] See appendix Figure 2 As shown, an intelligent photovoltaic switch includes a photovoltaic module 101, a switching transistor drive circuit 102, a PLC (power line carrier) demodulation circuit 103, a first coupling capacitor 104, a second coupling capacitor 105, a first switching transistor 106, a bypass diode 107, and a load resistor 108.

[0035] The PLC demodulation circuit 103 is electrically connected to the switching transistor drive circuit 102.

[0036] The source (S) of the first switching transistor 106 is connected to the negative terminal (PV-) of the photovoltaic module 101, the drain (D) of the first switching transistor 106 is connected to the anode of the bypass diode 107, and the gate (G) of the first switching transistor 106 is electrically connected to the switching transistor driving circuit 102.

[0037] The first end of the first coupling capacitor 104 is connected to the source (S) of the first switching transistor 106, and the second end of the first coupling capacitor 104 is connected to the drain (D) of the first switching transistor 106. The first coupling capacitor 104 is connected in parallel with the source and drain terminals of the first switching transistor 106 to provide an AC path for the AC carrier signal when the first switching transistor 106 is turned off.

[0038] The first end of the load resistor 108 is connected to the drain (D) of the first switching transistor 106, and the second end of the load resistor 108 is connected to the positive terminal (PV+) of the photovoltaic module 101. The load resistor 108 is connected between the outputs Vout+ and Vout- of the switch, and its resistance is greater than 10KΩ. When the first switching transistor 106 is turned off, it can provide reverse current to the first switching transistor 106.

[0039] The cathode of the bypass diode 107 is connected to the positive terminal (PV+) of the photovoltaic module 101; the bypass diode 107 is connected between the positive and negative terminals of the output of the switch and is used to provide a current path for other series components when the first switch 106 is turned off, so as to prevent high voltage from appearing between the source and drain of the first switch 106 and between Vout+ / Vout-.

[0040] Preferably, it further includes a second switch 109, which is turned on when the first switch 106 is turned off; the source (S) of the second switch 109 is connected to the drain (D) of the first switch 106, the drain (D) of the second switch 109 is connected to the positive terminal (PV+) of the photovoltaic module 101, and the gate (G) of the second switch 109 is electrically connected to the switch drive circuit 102.

[0041] The first switching transistor 106 and the second switching transistor 109 can be high-power MOSFET devices, or IGBTs, thyristors, or other electronic switches.

[0042] The second switch 109 and the first switch 106 cannot be turned on simultaneously. When the first switch 106 is turned off, the second switch 109 is turned on to provide a current path for other series components. Since the bypass diode 107 has a certain forward voltage (typically around 0.6V), when the first switch 106 is turned off and the string current is large, the bypass diode 107 will consume a lot of power and generate significant heat, potentially damaging the circuit breaker or even causing a fire in extreme cases. By adding the second switch 109, when the first switch 106 is turned off, the second switch 109 is turned on. Because the second switch 109 has a lower on-resistance, the heat generated when a large current flows through it is far less than the heat generated when current flows through the bypass diode 107, reducing the risk.

[0043] The first terminal of the second coupling capacitor 105 is connected to the positive terminal (PV+) of the photovoltaic module 101, and the second terminal of the second coupling capacitor 105 is electrically connected to the PLC demodulation circuit 103. The second coupling capacitor 105 is used to couple the carrier signals sampled from the positive and negative terminals (PV+ and PV-) of the photovoltaic module 101 into the PLC demodulation circuit 103 for demodulation. After the PLC demodulation circuit 103 demodulates the control information sent by the transmitting end, it controls the first switch 106 and the second switch 109 accordingly through the switch drive circuit 102.

[0044] Among them, such as Figure 3 As shown, the photovoltaic module 101 includes a solar panel PS, a parasitic capacitance Cp, a resistor Rs, and a parasitic inductance Lp; the resistor Rs is connected in series with the parasitic inductance Lp, and one end of the resistor Rs is connected to the positive terminal of the solar panel PS; one end of the parasitic capacitance Cp is connected to the positive terminal of the solar panel PS, and the other end is connected to the negative terminal of the solar panel PS.

[0045] The parasitic inductance Lp is 5uH, the resistance Rs is 1Ω, and the parasitic capacitance Cp is 100uF.

[0046] Preferably, since the parasitic inductance Lp and parasitic capacitance Cp of the photovoltaic module 101 exhibit band-resistance characteristics ( Figure 4 To reduce the attenuation of the PLC signal by the photovoltaic module 101, the carrier frequency band needs to avoid the band-stop portion of the photovoltaic module 101. However, if a low-frequency carrier band is chosen, large-capacitance coupling capacitors 104 and 105 are required, resulting in higher costs. Therefore, a carrier frequency band of around 1MHz is more suitable.

[0047] If the first switching transistor 106 is a PMOS device, then the source (S) is connected to PV+, the drain (D) is connected to Vout+, and the gate is connected to the switching transistor drive circuit; if the first switching transistor is an NMOS device, then the source (S) is connected to Vout+, the drain (D) is connected to PV+, and the gate is connected to the switching transistor drive circuit.

[0048] Compared to existing technologies, this invention proposes a simple and low-cost photovoltaic turn-off structure based on power line carrier communication. This invention utilizes the parasitic inductance of the photovoltaic module itself as the carrier signal load, significantly simplifying the carrier signal sampling and coupling circuit and reducing costs compared to existing technologies. Simultaneously, it avoids the safety hazards caused by heating of the series inductor under high current, thus improving the reliability of the turn-off device.

[0049] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A smart photovoltaic shut-off device, characterized in that: It includes photovoltaic modules, PLC demodulation circuit, switching transistor drive circuit, first coupling capacitor, second coupling capacitor, first switching transistor, bypass diode, and load resistor; Wherein, the source of the first switching transistor is connected to the negative terminal of the photovoltaic module, the drain of the first switching transistor is connected to the anode of the bypass diode, and the gate of the first switching transistor is electrically connected to the switching transistor driving circuit. The PLC demodulation circuit is electrically connected to the switching transistor drive circuit; The first end of the first coupling capacitor is connected to the source of the first switching transistor, and the second end of the first coupling capacitor is connected to the drain of the first switching transistor. The first end of the second coupling capacitor is connected to the positive terminal of the photovoltaic module, and the second end of the second coupling capacitor is electrically connected to the PLC demodulation circuit. The cathode of the bypass diode is connected to the positive electrode of the photovoltaic module; The first end of the load resistor is connected to the drain of the first switching transistor, and the second end of the load resistor is connected to the positive terminal of the photovoltaic module. The photovoltaic module includes a solar panel, parasitic capacitance, resistor, and parasitic inductance; The resistor is connected in series with the parasitic inductance, and one end of the resistor is connected to the positive terminal of the solar panel; one end of the parasitic capacitance is connected to the positive terminal of the solar panel, and the other end is connected to the negative terminal of the solar panel. Specifically, the first end of the second coupling capacitor is connected to the positive terminal of the photovoltaic module, and the first end of the second coupling capacitor is connected to one end of the parasitic inductor to couple the sampled carrier signal into the PLC demodulation circuit. The carrier frequency band of the carrier signal is outside the band-stop frequency band corresponding to the band-stop portion of the photovoltaic module.

2. The intelligent photovoltaic shut-off device according to claim 1, characterized in that: It also includes a second switch, which is turned on when the first switch is turned off; The source of the second switching transistor is connected to the drain of the first switching transistor, the drain of the second switching transistor is connected to the positive terminal of the photovoltaic module, and the gate of the second switching transistor is electrically connected to the switching transistor driving circuit.

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