PV panel reverse connection detection device and detection method

Abstract

The present invention discloses a PV panel reverse connection detection device, including a first boost circuit for reverse connection detection of a first PV battery string, the first boost circuit including a first voltage divider resistor, a first detection resistor, a first capacitor, a first inductor, a first diode, a busbar electrolytic capacitor and a first IGBT power element. A PV panel reverse connection detection method is also provided, which is suitable for detection using a PV panel reverse connection detection device. By connecting a detection resistor in parallel in the first boost circuit and adding voltage acquisition and voltage comparison at the input stage, it is determined whether the first PV battery string is reverse connected, thereby avoiding the problem of power generation loss caused by the reverse connection of the first PV battery string, and there is no need to configure a current sensor for the first PV battery string in the first boost circuit separately, further reducing the production cost of photovoltaic power generation equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation related equipment, and in particular to a PV panel reverse connection detection device and a detection method. Background Art

[0002] Photovoltaic inverters are responsible for converting the DC energy output by PV (photovoltaic) cells into AC power with the same frequency, phase and amplitude as the power grid through power conversion technology, and transmitting power to the power grid. In the actual installation process, due to improper operation by construction workers, it is easy to connect the positive and negative terminals of the PV panels in reverse. The reverse-connected strings and the parallel strings will not enter the working state, which will greatly cause power generation losses.

[0003] Since the input of the string inverter is composed of multiple boost circuits, in actual applications, not all boost circuits may be used. At this time, the output voltage of the boost circuit that is not in working state is 0; and when the PV panel is reversed, it also outputs a similar zero voltage, which makes it difficult to distinguish the two states. If only the voltage threshold is used for judgment, it is easy to confuse the two situations. The inverters currently on the market detect the current direction by adding current sensors to each string of PV panels, and then determine whether the panel is reversely connected. However, this method requires the addition of additional current sensors, which will increase the system cost of the grid-connected inverter. Summary of the invention

[0004] In order to solve the above technical defects, the technical solution adopted by the present invention is to provide a PV panel reverse connection detection device, including a first boost circuit for reverse connection detection of a first PV battery string PV1, the first boost circuit including a first voltage divider resistor R1, a first detection resistor R2, a first capacitor C1, a first inductor L1, a first diode D1, a bus electrolytic capacitor C3 and a first IGBT power element Q1.

[0005] The first end of the first inductor L1, the positive electrode of the first diode D1, and the first end of the bus electrolytic capacitor C3 are sequentially connected in series and electrically connected to the two ends of the first PV battery string PV1 to form a loop. The first voltage-dividing resistor R1 and the first capacitor C1 are sequentially connected in parallel to the two ends of the first PV battery string PV1. The drain of the first IGBT power element Q1 is electrically connected to the positive electrode of the first diode D1, the source of the first IGBT power element Q1 is electrically connected to the second end of the bus electrolytic capacitor C3, the first end of the first detection resistor R2 is connected to the first end of the first inductor L1, and the second end of the first detection resistor R2 is connected to the negative electrode of the first diode D1.

[0006] Furthermore, it also includes a second boost circuit for reverse connection detection of the second PV battery string PV2, the second boost circuit includes a second voltage divider resistor R3, a second detection resistor R4, a second capacitor C2, a second inductor L2, a second diode D2 and a second IGBT power element Q2.

[0007] The first end of the second inductor L2 and the drain of the second IGBT power element Q2 are sequentially connected in series and electrically connected to the two ends of the second PV battery string PV2 to form a loop. The second voltage-dividing resistor R3 and the second capacitor C2 are sequentially connected in parallel to the two ends of the second PV battery string PV2. The positive electrode of the second diode D2 is electrically connected to the drain of the second IGBT power element Q2, the negative electrode of the second diode D2 is electrically connected to the negative electrode of the first diode D1, the first end of the second detection resistor R4 is electrically connected to the first end of the second inductor L2, the second end of the second detection resistor R4 is electrically connected to the negative electrode of the second diode D2, and the source of the second IGBT power element Q2 is electrically connected to the second end of the bus electrolytic capacitor C3.

[0008] Furthermore, according to the voltage distribution formula V 1 =R 1 / (R 1 +R 2 )*V bus Configure R 1 and R 2 The resistance value is, where V 1 is the real-time detection voltage of the first PV battery string PV1, 10V≤V 1 ≤20V, R 1 is the first voltage divider resistor, R 2 is the first detection resistor, V bus is the voltage of busbar electrolytic capacitor C3, V pv is the maximum voltage of the first PV battery string PV1, and V bus =V pv .

[0009] Furthermore, the positive electrode of the busbar electrolytic capacitor C3 is electrically connected to the negative electrode of the first diode D1 , and the negative electrode of the busbar electrolytic capacitor C3 is electrically connected to the source electrode of the first IGBT power element Q1 and the source electrode of the second IGBT power element Q2 , respectively.

[0010] The present invention also provides a PV panel reverse connection detection method, which is suitable for detection using the above-mentioned PV panel reverse connection detection device, and comprises the following steps:

[0011] S1: Detect the output voltage V across the first PV battery string PV1 1 ;

[0012] S2: Determine the output voltage V 1 Is it less than the reverse connection preset threshold voltage V of the first PV battery string PV1? Lmt If so, it is determined that there is a reverse connection of the PV panels in the first PV battery string PV1.

[0013] Furthermore, before step S1, the following steps are also included:

[0014] A1: Get the voltage V of the busbar electrolytic capacitor C3 when the first PV battery string PV1 is correctly connected and generating electricity normally bus , where V bus is the maximum voltage V of the first PV battery string PV1 pv ;

[0015] A2: When the first boost circuit is not connected to the first PV battery string PV1, according to the voltage configuration calculation formula V 1 =R 1 / (R 1 +R 2 )*V bus , set V 1 The value range of the first voltage divider resistor R in the first boost circuit is obtained. 1 and the first detection resistor R 2 Configuration resistance value.

[0016] Furthermore, the V 1 The voltage range is 10-20V.

[0017] Further, in step S2: when the first PV battery string PV1 includes two PV battery panels connected in series, if V 1 = 0, it is determined that one PV panel in the first PV battery string PV1 is reversely connected; when V 1 When it is close to zero and has a negative sign, it is determined that both PV panels in the first PV battery string PV1 are reversely connected.

[0018] Furthermore, the V Lmt =5V.

[0019] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0020] 1. The present invention provides a PV panel reverse connection detection device and detection method, which detects the output voltage of the PV battery string by connecting a detection resistor in parallel in the boost circuit, adds voltage collection and voltage comparison at the input stage, and determines whether the PV battery string is reversely connected, and generates an alarm when the PV battery panel is reversely connected. The problem of power generation loss caused by reverse connection of the PV battery string is avoided, and there is no need to configure a current sensor for the PV battery string in the boost circuit separately, which further reduces the production cost of photovoltaic power generation equipment. The device is suitable for reverse connection detection of photovoltaic battery strings in multiple boost circuits of string inverters.

[0021] 2. By adding a detection loop between the input stage and the output stage, the characteristics of the boost circuit in the non-working state are increased, and the difference between the boost circuit in the non-working state and the PV panel in the reverse connection state can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 is a circuit schematic diagram of a PV panel reverse connection detection device provided by an embodiment of the present invention;

[0024] Figure 2 is a circuit diagram of a PV panel reverse connection detection device provided by an embodiment of the present invention when the first PV battery group string is connected in a forward direction;

[0025] Figure 3 is a circuit diagram of a PV panel reverse connection detection device provided by an embodiment of the present invention when the first boost circuit is not connected to the first PV battery string;

[0026] Figure 4 is a circuit diagram of a PV panel reverse connection detection device provided by an embodiment of the present invention when a first PV battery string has a PV panel reversely connected;

[0027] Figure 5 This is a circuit diagram of a PV panel reverse connection detection device provided by an embodiment of the present invention when both PV panels of a first PV battery string are reversely connected. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0029] Example 1

[0030] See also Figure 1-Figure 5 As shown, a PV panel reverse connection detection device provided by the present invention includes a first boost circuit for reverse connection detection of a first PV battery string PV1 in a photovoltaic inverter, and the first boost circuit includes a first voltage-dividing resistor R1, a first detection resistor R2, a first capacitor C1, a first inductor L1, a first diode D1, a bus electrolytic capacitor C3 and a first IGBT (Insulated Gate Bipolar Transistor) power element Q1.

[0031] The first end of the first inductor L1, the positive electrode of the first diode D1, and the first end of the bus electrolytic capacitor C3 are connected in series in sequence and electrically connected to the two ends of the first PV battery string PV1 to form a loop. The first voltage-dividing resistor R1 and the first capacitor C1 are connected in parallel at the two ends of the first PV battery string PV1 in sequence. The drain of the first IGBT power element Q1 is electrically connected to the positive electrode of the first diode D1, the source of the first IGBT power element Q1 is electrically connected to the second end of the bus electrolytic capacitor C3, the first end of the first detection resistor R2 is connected to the first end of the first inductor L1, and the second end of the first detection resistor R2 is connected to the negative electrode of the first diode D1.

[0032] Furthermore, it also includes a second boost circuit for reverse connection detection of the second PV battery string PV2 in the photovoltaic inverter, and the second boost circuit includes a second voltage-dividing resistor R3, a second detection resistor R4, a second capacitor C2, a second inductor L2, a second diode D2 and a second IGBT power element Q2.

[0033] The first end of the second inductor L2 and the drain of the second IGBT power element Q2 are connected in series and electrically connected to the two ends of the second PV battery string PV2 to form a loop. The second voltage-dividing resistor R3 and the second capacitor C2 are connected in parallel at the two ends of the second PV battery string PV2. The positive electrode of the second diode D2 is electrically connected to the drain of the second IGBT power element Q2, the negative electrode of the second diode D2 is electrically connected to the negative electrode of the first diode D1, the first end of the second detection resistor R4 is electrically connected to the first end of the second inductor L2, the second end of the second detection resistor R4 is electrically connected to the negative electrode of the second diode D2, and the source of the second IGBT power element Q2 is electrically connected to the second end of the bus electrolytic capacitor C3.

[0034] like Figure 1 As shown, the detection resistor R 2 With R 4 The positive terminal of the bus electrolytic capacitor C3 is connected in parallel to the positive input terminal of the two boost circuits. When any PV battery string is connected correctly and generates electricity normally, the voltage V bus is the maximum voltage across the PV battery string V pv .

[0035] Preferably, according to the voltage distribution formula V 1 =R 1 / (R 1 +R 2 )*V bus Configure R 1 and R 2 The resistance value is, where V 1 is the real-time detection voltage of the first PV battery string PV1, 10V≤V 1 ≤20V, R 1 is the first voltage divider resistor, R 2 is the first detection resistor, V bus is the voltage of busbar electrolytic capacitor C3, V pv is the maximum voltage of the first PV battery string PV1, and V bus =V pv .

[0036] Preferably, the positive electrode of the bus electrolytic capacitor C3 is electrically connected to the negative electrode of the first diode D1 , and the negative electrode of the bus electrolytic capacitor C3 is electrically connected to the source electrode of the first IGBT power element Q1 and the source electrode of the second IGBT power element Q2 .

[0037] Preferably, the first PV cell string PV1 and the second PV cell string PV2 each include at least two PV panels connected in series.

[0038] A PV panel reverse connection detection method is applicable to use the above-mentioned PV panel reverse connection detection device for detection, taking the reverse connection detection of the first photovoltaic cell string PV1 as an example, comprising the following steps:

[0039] A1: Get the voltage V of bus capacitor C3 when the first PV battery string PV1 is correctly connected and generating electricity normally bus , where V bus is the maximum voltage V of the first PV battery string PV1 pv .

[0040] like Figure 3 As shown, when the boost circuit is in a non-operating state, that is, the PV panel is not connected, there will be a detectable configuration voltage at the input stage. The voltage is determined by the resistance value of the configuration resistor to distinguish the state where the input stage is zero when any reverse connection occurs.

[0041] A2: When the first boost circuit is not connected to the first PV battery string PV1, the first detection resistor R 2 The first voltage divider resistor R 1 A voltage divider circuit is formed. According to the voltage configuration calculation formula V 1 =R 1 / (R1 +R 2 )*V bus At this time, it can be detected that the voltage at the V1 terminal is positive. By setting V 1 The value range of the first voltage divider resistor R in the first boost circuit is obtained. 1 and the first detection resistor R 2 Configuration resistance value; where 10V≤V 1 ≤20V, which is convenient for full voltage detection.

[0042] S1: Detect the output voltage V across the first PV battery string PV1 of the photovoltaic inverter 1 ;

[0043] S2: Determine the output voltage V 1 Is it less than the reverse connection preset threshold voltage V of the first PV battery string PV1? Lmt , preferably, V Lmt =5V; if so, it is determined that there is a reverse connection of the PV panels in the first PV battery string PV1.

[0044] Wherein, in step S2: when the first PV battery string PV1 includes two PV battery panels connected in series, if V 1 = 0, it is determined that one PV panel in the first PV battery string PV1 is reversely connected; when V 1 When it is close to zero and has a negative sign, it is determined that both PV panels in the first PV battery string PV1 are reversely connected.

[0045] like Figure 2 As shown, when the first boost circuit is correctly connected to the first PV battery string PV1, the photovoltaic impedance is the power supply impedance, and its impedance R PV With R 1 In parallel. Usually, R PV < <R 1 , which can be ignored by R 2 The voltage division caused by the resistor is V 1 The voltage is mainly determined by the photovoltaic voltage. 1 The voltage across the two ends is known. If V 1 Equal to the photovoltaic cell voltage V PV , then the PV strings are connected correctly.

[0046] The present invention provides a PV cell reverse connection detection device and detection method, the working principle of which is as follows: Figure 4 As shown in the figure, when one of the two PV cells in the first boost circuit is reversely connected and the other is normally connected, the two PV cells form a short-circuit loop current, and the detected V 1 The terminal voltage is 0, and it can be determined that the PV string is reversely connected. Figure 5As shown, when the two PV cells of the first boost circuit are reversely connected, the photovoltaic panel is short-circuited through the anti-parallel diode of the IGBT power element in the boost circuit, and the input voltage V 1 The magnitude is the forward conduction voltage drop of the diode. This value is small and close to zero, and the sign is negative. At this time, it can be determined that the PV string is reversely connected.

[0047] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A PV panel reverse connection detection device, comprising a first boost circuit for performing reverse connection detection on a first PV battery string PV1, Features: The first boost circuit includes a first voltage-dividing resistor R1, a first detection resistor R2, a first capacitor C1, a first inductor L1, a first diode D1, a bus electrolytic capacitor C3 and a first IGBT power element Q1; The first inductor L1, the first diode D1, and the bus electrolytic capacitor C3 are connected in series in sequence, the first end of the first inductor L1 is connected to one end of the first PV battery string PV1, the second end of the first inductor L1 is connected to the positive electrode of the first diode D1, the negative electrode of the first diode D1 is connected to the first end of the bus electrolytic capacitor C3, and the second end of the bus electrolytic capacitor C3 is connected to the other end of the first PV battery string PV1, the first voltage-dividing resistor R1 and the first capacitor C1 are connected in parallel at both ends of the first PV battery string PV1 in sequence, the drain of the first IGBT power element Q1 is electrically connected to the positive electrode of the first diode D1, the source of the first IGBT power element Q1 is electrically connected to the second end of the bus electrolytic capacitor C3, the first end of the first detection resistor R2 is connected to the first end of the first inductor L1, and the second end of the first detection resistor R2 is connected to the negative electrode of the first diode D1; Detect the output voltage V across the first PV battery string PV1 of the photovoltaic inverter 1 ; Determine the output voltage V 1 Is it less than the reverse connection preset threshold voltage V of the first PV battery string PV1? Lmt ; If so, it is determined that there is a reverse connection of the PV panels in the first PV battery string PV1; When the boost circuit is in a non-operating state, that is, the PV panel is not connected, there is a detectable configuration voltage at the input stage to distinguish the state where the input stage is zero when any reverse connection occurs.

2. The PV panel reverse connection detection device according to claim 1, Features: Also includes a second boost circuit for performing reverse connection detection on the second PV battery string PV2, the second boost circuit including a second voltage-dividing resistor R3, a second detection resistor R4, a second capacitor C2, a second inductor L2, a second diode D2 and a second IGBT power element Q2; The second inductor L2 and the second IGBT power element Q2 are connected in series, a first end of the second inductor L2 is connected to one end of the second PV battery string PV2, a second end of the second inductor L2 is connected to the drain of the second IGBT power element Q2, a source of the second IGBT power element Q2 is connected to the other end of the second PV battery string PV2, a second voltage-dividing resistor R3 and a second capacitor C2 are sequentially connected in parallel at both ends of the second PV battery string PV2, a positive electrode of the second diode D2 is electrically connected to the drain of the second IGBT power element Q2, a negative electrode of the second diode D2 is electrically connected to the negative electrode of the first diode D1, a first end of the second detection resistor R4 is electrically connected to the first end of the second inductor L2, a second end of the second detection resistor R4 is electrically connected to the negative electrode of the second diode D2, and a source of the second IGBT power element Q2 is electrically connected to the second end of the bus electrolytic capacitor C3.

3. The PV panel reverse connection detection device according to claim 1, Features: According to the voltage distribution formula V 1 =R 1 / (R 1 +R 2 )*V bus Configure R 1 and R 2 The resistance value is, where V 1 is the real-time detection voltage of the first PV battery string PV1, 10V≤V 1 ≤20V, R 1 is the first voltage divider resistor, R 2 is the first detection resistor, V bus is the voltage of busbar electrolytic capacitor C3, V pv is the maximum voltage of the first PV battery string PV1, and V bus =V pv .

4. The PV panel reverse connection detection device according to claim 1, Features: The positive electrode of the busbar electrolytic capacitor C3 is electrically connected to the negative electrode of the first diode D1 , and the negative electrode of the busbar electrolytic capacitor C3 is electrically connected to the source electrode of the first IGBT power element Q1 and the source electrode of the second IGBT power element Q2 .

5. A PV panel reverse connection detection method, suitable for detecting using the PV panel reverse connection detection device according to any one of claims 1 to 4, Features : It includes the following steps: S1: Detect the output voltage V across the first PV battery string PV1 1 ; S2: Determine the output voltage V 1 Is it less than the reverse connection preset threshold voltage V of the first PV battery string PV1? Lmt If so, it is determined that there is a reverse connection of the PV panels in the first PV battery string PV1.

6. The PV panel reverse connection detection method according to claim 5, Features : Before step S1, the following steps are also included: A1: Get the voltage V of the busbar electrolytic capacitor C3 when the first PV battery string PV1 is correctly connected and generating electricity normally bus , where V bus is the maximum voltage V of the first PV battery string PV1 pv ; A2: When the first boost circuit is not connected to the first PV battery string PV1, according to the voltage configuration calculation formula V 1 =R 1 / (R 1 +R 2 )*V bus , set V 1 The value range of the first voltage divider resistor R in the first boost circuit is obtained. 1 and the first detection resistor R 2 Configuration resistance value.

7. The PV panel reverse connection detection method according to claim 6, Features : The V 1 The voltage range is 10V-20V.

8. The PV panel reverse connection detection method according to claim 5, Features : In step S2: When the first PV battery string PV1 includes two PV battery panels connected in series, if V 1 =0, it is determined that one PV panel in the first PV battery string PV1 is reversely connected; when V 1 When it is close to zero and has a negative sign, it is determined that both PV panels in the first PV battery string PV1 are reversely connected.

9. The PV panel reverse connection detection method according to claim 5, Features : The V Lmt =5V.

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