Inverter unit and converter
By placing an arc fault divider near the power switching transistors of the converter, the problem of arc detection caused by environmental pollution inside the converter is solved, achieving timely identification and prevention of fault expansion, and improving the safety and reliability of the system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-21
- Publication Date
- 2026-03-24
AI Technical Summary
Existing converters cannot detect arcing caused by environmental pollution, which may lead to short circuits and overheating disconnection, and in turn, fire.
An arc fault divider is placed near the power switching transistors of the converter. By detecting high-frequency characteristic quantities, the internal arcing phenomenon is identified, and arc extinguishing is performed to prevent the fault from spreading.
Effectively identify and prevent arcing inside the converter caused by environmental pollution, avoid short circuit and fire risks, and improve system reliability.
Smart Images
Figure CN224037276U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of current transformer, in particular to an inverter unit and a current transformer. BACKGROUND
[0002] Most of the existing current transformers are provided with arc fault circuit interrupters (AFCI) at the input end, which can sample, analyze and arc judge the current of the direct current input in combination with an AI algorithm, so as to quickly detect the arc phenomenon of the front-stage components or cables at the input end (the outside) of the current transformer, and quickly break and extinguish the arc to avoid further expansion of the fault. For example, as shown in FIG. 1, the arc fault circuit interrupter AFCI_1 can detect the direct current arc phenomenon in the photovoltaic array. Figure 1
[0003] The internal environment of the current transformer will be polluted to different degrees when the current transformer reaches a certain service life or in the case of extremely harsh environment, which will cause great risk to the reliability of the current transformer and the system. The reasons are as follows: on the one hand, the sealing medium such as the dust plug of the current transformer may be damaged to different degrees as the service life increases, resulting in a decrease in the sealing performance of the current transformer, and rainwater, dust and other impurities will enter the current transformer to pollute the internal environment; on the other hand, when the external environment temperature rapidly decreases, the temperature of the metal shell of the current transformer will also rapidly decrease, while the specific heat capacity of air and metal is quite different, and the temperature change of the internal air of the current transformer is relatively slow, thereby causing a temperature difference between the internal air and the inner wall of the metal shell, and the air with a higher temperature will condense into water droplets when meeting the inner wall of the metal shell with a lower temperature, thereby polluting the internal environment of the current transformer. No matter what the reason is, when the internal environment of the current transformer is polluted to a certain degree, it may cause short-circuit failure of the power semiconductor device, a decrease in the safety insulation performance of the circuit board, and a short-circuit loop of the current transformer, which will heat at the device with a large impedance, and finally overheat and break, at this time, arc phenomenon is easily formed, and the internal fire of the current transformer is caused.
[0004] Therefore, although the existing technology can identify the arc phenomenon outside the input end of the current transformer, the AFCI cannot detect the arc phenomenon caused by serious environmental pollution in the internal environment of the current transformer because the distance between the AFCI and the power semiconductor device in the current transformer is far, and multiple capacitors are passed in between. CONTENT OF THE INVENTION
[0005] Therefore, the purpose of the present application is to provide an inverter unit and a current transformer to solve the problem that the AFCI in the prior art cannot detect the arc phenomenon caused by serious environmental pollution in the internal environment of the current transformer.
[0006] The technical solution adopted by the present application to solve the above technical problems is as follows:
[0007] The first aspect of the present application provides an inverter unit, comprising a positive direct current end and a negative direct current end, a plurality of bridge arms connected between the positive direct current end and the negative direct current end, each bridge arm comprising a first power switch tube and an alternating current end;
[0008] The alternating current end of at least one bridge arm is connected with a first arc fault segmenter.
[0009] The second aspect of the present application provides a converter comprising the inverter unit of the first aspect.
[0010] The inverter unit and the converter provided by the present application can detect the arc phenomenon inside the converter by placing the arc fault segmenter near the power switch tube, and indirectly identify the short circuit fault caused by the serious environmental pollution leading to the decrease of the safety regulation insulation performance inside the converter by means of the arc fault segmenter, and finally perform arc extinguishing and breaking to prevent the fault from further increasing. BRIEF DESCRIPTION OF DRAWINGS
[0011] Figure 1 It is a schematic diagram of a photovoltaic inverter of the prior art;
[0012] Figure 2 It is a schematic diagram of a photovoltaic inverter provided by the embodiment of the present application;
[0013] Figure 3 It is a schematic diagram of the function flow of the arc fault segmenter provided by the embodiment of the present application;
[0014] Figure 4 It is a schematic diagram of a double BOOST circuit provided by the embodiment of the present application;
[0015] Figure 5 It is a schematic diagram of a flying capacitor BOOST circuit provided by the embodiment of the present application;
[0016] Figure 6 It is a schematic diagram of an ANPC three-level three-phase bridge circuit provided by the embodiment of the present application;
[0017] Figure 7 It is a schematic diagram of a T-type three-level three-phase bridge circuit provided by the embodiment of the present application;
[0018] Figure 8 It is a schematic diagram of a single-phase full-bridge circuit provided by the embodiment of the present application;
[0019] Figure 9 It is a schematic diagram of a single-phase Heric bridge circuit provided by the embodiment of the present application.
[0020] The implementation, functional features and advantages of the present application will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION
[0021] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer and more apparent, the present application will be further described in detail below in conjunction with the drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application and not to limit the present application.
[0022] The embodiment of the present application provides a converter, which comprises an inverter unit, the inverter unit comprising a positive direct current end and a negative direct current end, a plurality of bridge arms connected between the positive direct current end and the negative direct current end, each bridge arm comprising a first power switch tube and an alternating current end; wherein the alternating current end of at least one bridge arm is connected with a first arc fault segmenter.
[0023] In one example, no capacitive device is arranged between the first arc fault segmenter and the first power switch tube.
[0024] In one example, the plurality of bridge arms constitute a single-phase inverter circuit or a three-phase inverter circuit. The single-phase inverter circuit comprises one of a Heric circuit, a H5 circuit, a H6 circuit, a single-phase H bridge circuit; the three-phase inverter circuit comprises one of a type I three-level three-phase bridge circuit, an ANPC three-level three-phase bridge circuit, a T-type three-level three-phase bridge circuit, and a three-phase full-bridge circuit.
[0025] In one example, a bus capacitor is further connected between the positive direct current end and the negative direct current end. The bus capacitor comprises a group of capacitors or is composed of a plurality of groups of capacitors in series and / or parallel.
[0026] The converter includes but is not limited to a common photovoltaic inverter, a wind power converter, an energy storage converter, etc.
[0027] Taking a photovoltaic inverter as an example, the converter further comprises a DC / DC conversion unit connected with the positive direct current end and the negative direct current end of the inverter unit. The DC / DC conversion unit comprises a two-level boost circuit or a three-level boost circuit. The two-level boost circuit comprises a single BOOST circuit or a BUCK-BOOST circuit; the three-level boost circuit comprises a double BOOST circuit or a flying capacitor BOOST circuit. The DC / DC conversion unit further comprises a second power switch tube and a second arc fault segmenter connected with the second power switch tube.
[0028] The wind power converter is taken as an example. The converter further comprises a rectifier circuit connected with the positive DC end and the negative DC end of the inverter unit, and the rectifier circuit comprises a single-phase rectifier circuit or a three-phase rectifier circuit. The single-phase rectifier circuit comprises a Heric circuit, a H5 circuit, a H6 circuit, a single-phase H-bridge circuit, etc. The three-phase rectifier circuit comprises a type I three-level three-phase bridge circuit, an ANPC three-level three-phase bridge circuit, a T-type three-level three-phase bridge circuit, a three-phase full-bridge circuit, etc. Similarly to the DC / DC conversion unit, the rectifier circuit also comprises a third power switch tube and a third arc fault segmenter connected with the third power switch tube.
[0029] In order to better understand the present application, the following will take a photovoltaic inverter as an example and combine Figures 2-9 with the accompanying drawings to illustrate the technical solutions of the present application.
[0030] As shown in the drawings, the inverter unit of the photovoltaic inverter is a type I three-level three-phase bridge circuit. Figure 2
[0031] In the type I three-level three-phase bridge circuit, the power switch tubes TA1-TA4 (i.e. the power switch tubes TA1, TA2, TA3 and TA4, hereinafter similar), the diodes DA1-DA6 constitute a first bridge arm; the power switch tubes TB1-TB4, the diodes DB1-DB6 constitute a second bridge arm; the power switch tubes TC1-TC4, the diodes DC1-DC6 constitute a third bridge arm.
[0032] The AC end of the first bridge arm is connected with the arc fault segmenter AFCI_A, i.e. connected with the power grid through the arc fault segmenter AFCI_A; the AC end of the second bridge arm is connected with the arc fault segmenter AFCI_B, i.e. connected with the power grid through the arc fault segmenter AFCI_B; the AC end of the third bridge arm is connected with the arc fault segmenter AFCI_C, i.e. connected with the power grid through the arc fault segmenter AFCI_C.
[0033] The capacitors C2 and C3 are bus capacitors, and the capacitors C2 and C3 are connected between the positive DC end and the negative DC end of the type I three-level three-phase bridge circuit. The neutral points of the first bridge arm, the second bridge arm and the third bridge arm are all connected between the capacitors C2 and C3.
[0034] The DC / DC conversion unit of the photovoltaic inverter is connected between the photovoltaic cell and the inverter unit, and the capacitor C1 is a filter capacitor. The DC / DC conversion unit is a single BOOST circuit.
[0035] The single BOOST circuit includes a power switch Q1, an inductor L1, and a diode D1. Further, the single BOOST circuit also includes an arc fault segmenter AFCI_2, which is connected with one end of the power switch Q1 and the anode of the diode D1 through the inductor L1.
[0036] Since there is no capacitive element between the arc fault segmenter AFCI_2 and the power switch Q1 and the diode D1, when the power switch Q1 or the diode D1 and the nearby line caused by serious pollution inside the photovoltaic inverter appear a direct current arc phenomenon, the arc fault segmenter AFCI_2 can identify and report the fault and react in time to prevent the fault from further expanding, and alarm that the inside of the photovoltaic inverter needs to be cleaned.
[0037] Since there is no capacitive element between the arc fault segmenter AFCI_A and the power switches TA1-TA4 and the diodes DA1-DA6, the high-frequency characteristic quantity at the moment of arc is ensured not to be absorbed by the capacitive element, so that the arc fault segmenter AFCI_A cannot detect it. Therefore, when the power switches TA1-TA4 or the diodes DA1-DA6 and the nearby line caused by serious pollution inside the photovoltaic inverter appear a direct current arc phenomenon, the arc fault segmenter AFCI_A can identify and report the fault and react in time to prevent the fault from further expanding, and alarm that the inside of the photovoltaic inverter needs to be cleaned. The arc fault segmenters AFCI_B and AFCI_C are similar.
[0038] AFCI, which can be a current sensor provided by the existing converter or a component for sampling current of the corresponding branch of the existing converter, in other words, additional hardware does not need to be added.
[0039] Figure 3 The figure is a functional flow diagram of the arc fault segmenter. When the photovoltaic inverter has serious environmental pollution and an arc phenomenon occurs, the arc fault segmenter samples the current, then performs fast Fourier transform (FFT), extracts the high-frequency characteristic quantity of 50-120 kHz, analyzes whether the arc occurs (arc detection), then confirms the arc or the fault, reports the fault after the confirmation is completed, and finally starts protection.
[0040] The starting protection method can include: tripping the segment switch on the alternating current and / or direct current side.
[0041] In an example, Figure 2 The single BOOST circuit in the figure can be replaced by the double BOOST circuit shown in the figure or the flying capacitor BOOST circuit shown in the figure. Figure 4 Figure 5
[0042] In an example, Figure 2 The type I three-level three-phase bridge circuit in the can be replaced by Figure 6 the ANPC three-level three-phase bridge circuit shown in FIG. 1, or Figure 7 the T-type three-level three-phase bridge circuit shown in FIG. 2, or Figure 8 the single-phase full-bridge circuit shown in FIG. 3, or Figure 9 the single-phase Heric bridge circuit shown in FIG. 4.
[0043] The scheme provided by the embodiments of the present application is not limited to the above-mentioned circuit topologies. The core idea of the present application is that the AFCI is placed near the power switch tube, and no capacitive device is contained between the AFCI and the power switch tube, so as to ensure that the high-frequency characteristic quantity of the power switch tube at the arc drawing moment cannot be absorbed by the capacitive device, and thus the AFCI cannot be detected. Based on the core idea, the scheme provided by the embodiments of the present application is applied to any circuit topology of the converter, and is within the protection scope of the present application.
[0044] The above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to some technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. An inverter unit, characterized in that, It includes a positive DC terminal and a negative DC terminal, and multiple bridge arms connected between the positive DC terminal and the negative DC terminal, each bridge arm including a first power switch and an AC terminal; At least one of the bridge arms has its AC terminal connected to the first arc fault breaker.
2. The inverter unit according to claim 1, characterized in that, No capacitive device is installed between the first arc fault segmenter and the first power switch.
3. The inverter unit according to claim 1, characterized in that, The multiple bridge arms constitute a single-phase inverter circuit or a three-phase inverter circuit.
4. The inverter unit according to claim 3, characterized in that, The single-phase inverter circuit includes one of the following: Heric circuit, H5 circuit, H6 circuit, and single-phase H-bridge circuit. The three-phase inverter circuit includes one of the following: a type I three-level three-phase bridge circuit, an ANPC three-level three-phase bridge circuit, a type T three-level three-phase bridge circuit, and a three-phase full-bridge circuit.
5. The inverter unit according to claim 1, characterized in that, A bus capacitor is also connected between the positive DC terminal and the negative DC terminal.
6. The inverter unit according to claim 5, characterized in that, The bus capacitor includes a set of capacitors or is composed of multiple sets of capacitors connected in series and / or in parallel.
7. A converter, characterized in that, Includes the inverter unit as described in any one of claims 1-6.
8. The converter according to claim 7, characterized in that, The converter also includes a DC-DC conversion unit connected to the positive DC terminal and the negative DC terminal of the inverter unit.
9. The converter according to claim 8, characterized in that, The DC-DC conversion unit includes a two-level boost circuit or a three-level boost circuit.
10. The converter according to claim 8, characterized in that, The DC-DC conversion unit includes a second power switch and a second arc fault segmenter connected to the second power switch.