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EP-4404406-B1 - PROTECTION APPARATUS AND PROTECTION METHOD FOR PHOTOVOLTAIC POWER GENERATION SYSTEM AND PHOTOVOLTAIC POWER GENERATION SYSTEM

EP4404406B1EP 4404406 B1EP4404406 B1EP 4404406B1EP-4404406-B1

Inventors

  • ZHANG, Xiufeng
  • ZHANG, Yanzhong

Dates

Publication Date
20260506
Application Date
20210316

Claims (5)

  1. A protection apparatus (200) for a photovoltaic power generation system (2400), applied to the photovoltaic power generation system (2400), wherein the apparatus (200) comprises at least one DC/DC conversion circuit, at least one group of interfaces, protection switches, a direct current bus, and a controller; the at least one DC/DC conversion circuit is connected to the direct current bus, the interfaces configured to be connected to photovoltaic units, the protection apparatus is characterised in that : the at least one DC/DC conversion circuit is configured to be connected to four photovoltaic units via the direct current bus using the at least one group of interfaces, wherein the at least one group of interfaces are configured to connect two of the four photovoltaic units in parallel, one polarity (-) of the direct current bus is connected to three first switches and the opposite polarity (+) of the direct current bus connected to one or two second switches, wherein the interfaces are configured to connect output ends of one polarity (-) of the four photovoltaic units to the three first switches and output ends of other polarity (+) of the four photovoltaic units are connected to one or two second switch, wherein the first and second switches are configured to disconnect all or some of the photovoltaic units (101a) from the direct current bus; and the controller is configured to: when determining, based on a parameter detection value of the branch, that the photovoltaic power generation system (2400) is faulty, control at least one of the protection switches to be open, wherein the parameter detection value is a reverse current value, and the controller is specifically configured to: when a reverse current value of a branch is greater than a first current value, determine that the photovoltaic power generation system (2400) is faulty to control a protection switch to be open, so that a current of the branch is less than the first current value.
  2. The apparatus (200) according to claim 1, wherein the controller is further configured to control, according to a control instruction sent by a host computer, the protection switch to be open or closed.
  3. The apparatus (200) according to claim 1 or 2, wherein any one of the protection switchs is a rotary direct current switch (102) disconnector or direct current circuit breaker.
  4. The apparatus (200) according to claim 3, wherein the controller is further configured to: after a preset time elapses when it is determined that a fault is rectified, control any one of the protection switchs to be closed.
  5. A protection method for a photovoltaic power generation system (2400), applied to a protection apparatus (200) for the photovoltaic power generation system (2400) of claim 1, and the method comprises: when determining, based on a parameter detection value of the branch, that the photovoltaic power generation system (2400) is faulty, controlling any one of the protection switches to be open, wherein the parameter detection value is a reverse current value, and the determining, based on a parameter detection value of the branch or a parameter detection value of the direct current bus, that the photovoltaic power generation system (2400) is faulty specifically comprises: when a reverse current value of a branch is greater than a first current value, determining that the photovoltaic power generation system (2400) is faulty, and controlling a protection switch to be open, so that a current of the branch is less than the first current value.

Description

TECHNICAL FIELD This application relates to the field of photovoltaic power generation technologies, and in particular, to a protection apparatus for a photovoltaic power generation system, and a protection method for a photovoltaic power generation system. BACKGROUND Photovoltaic power generation is a technology that uses a photovoltaic effect of a semiconductor interface to convert light energy into electric energy. A photovoltaic power generation system may usually include a photovoltaic unit, an inverter, an alternating current power distribution device, and the like. To obtain a relatively high output voltage or output current, the photovoltaic unit usually formed by connecting a plurality of photovoltaic components in a specific serial and/or parallel connection manner. The photovoltaic unit is connected to a component with an independent MPPT (maximum power point tracking, maximum power point tracking) function, to improve power generation efficiency of the photovoltaic power generation system. Currently, to improve a direct current ratio of the photovoltaic power generation system (a ratio of power of the photovoltaic unit to input power of the inverter), each MPPT component is usually connected to at least two photovoltaic units. In an example in which a photovoltaic unit or a line in which a photovoltaic unit is located is short circuited, a short-circuit current is a sum of output currents of other connected photovoltaic units. When there is only one other connected photovoltaic unit, the photovoltaic unit and the line can tolerate this short-circuit current because the short-circuit current is relatively small. However, when there are two or more connected photovoltaic units, the short-circuit current is relatively large. To protect the photovoltaic unit and the line, fuses or a fuse may be connected to a positive output end and/or a negative output end of the photovoltaic unit in series, so that the fuse blows to protect the photovoltaic unit and the line. However, because a fuse current of the fuse is usually relatively high, and an output current of each photovoltaic unit is relatively low, a sum of short-circuit currents of a plurality of photovoltaic units can hardly reach the fuse current of the fuse. Consequently, the fuse cannot effectively protect the photovoltaic unit and the line. In addition, a resistance of the fuse is relatively large, and this may cause a relatively large power loss in the photovoltaic power generation system. US 2017/229856 Al discloses a combiner box including input connections for string lines from a plurality of strings of photovoltaic modules, and output connections for a pair of output lines to an inverter. The combiner box further includes a switching device by means of which the strings are connected to the inverter and which comprises output-side switching contacts and, for each of the strings or for each pair of strings connected in parallel in a fixed manner in the combiner box, at least one separate input-side switching contact, and an overcurrent protection device, which interrupts occurring overcurrents from or to each of the strings or at least from or to each of the pairs of strings connected in parallel in a fixed manner in the combiner box. The switching device includes a switching-contact drive, which is controlled in order to selectively disconnect the strings from the inverter. CN 110 224 381 A discloses a photovoltaic inverter, which comprises a DC/AC converter, a positive DC bus, a negative DC bus, a drive control circuit and at least one first unit. A first end of the positive DC bus and a first end of the negative DC bus are electrically connected with the DC/AC converter. The first unit includes a first bypass circuit and an isolation circuit. The drive control circuit is used for making a first end and a second end of the first bypass circuit connected to form a circuit and making a first end and a second end of the isolation circuit disconnected so as to disconnect a first photovoltaic module from the positive DC bus or the negative DC bus after the positive DC bus or the negative DC bus fails, and the disconnection time of the isolation circuit is later than the conduction time of the first bypass circuit. JP 2018 182945 A discloses a power conversion device which can suppress the degradation of a solar photovoltaic device by a simple structure. SOLUTION: A power conversion device comprises a power conversion part which converts a DC power received from a solar photovoltaic generation part to an AC power, and outputs the resultant AC power to a power system or load. A storage battery or a power-generation part operable to generate a power by use of an energy different from solar light energy are connected to the power system or load through the power conversion part. The power conversion device further comprises a switch for switching whether or not to electrically connect the solar photovoltaic generation part and the power conversion