Relay failure detection method, device and system for photovoltaic grid-connected inverter

Abstract

The embodiments of the present invention provide a relay failure detection method, device and system for a photovoltaic grid-connected inverter. According to the method, a first relay is controlled tobe switched on, and a second relay is controlled to be switched off; the voltage value of a first capacitor during a preset time period is obtained, and a first target value is determined according to the direct current branch value of the voltage value and the alternating current branch value of the voltage value; and when the first target value is smaller than or equal to a preset relay adhesion fault threshold, it is determined that the first relay does not undergo an adhesion fault, and when the first target value is greater than the preset relay adhesion fault threshold, it is determinedthat the first relay undergoes an adhesion fault. According to the technical schemes of the invention, the voltage value of the first capacitor is detected and is compared with the preset threshold,so that whether the relay undergoes a fault can be determined, that is, only one voltage is required to be collected, and therefore, the cost of detection hardware and the resources of a digital processing chip can be saved; since the feature of the preset threshold is obvious, a judgment result is reliable, and therefore, the accuracy of detection can be improved.

Description

technical field [0001] The invention relates to the technical field of new energy power generation, in particular to a relay failure detection method, device and system of a photovoltaic grid-connected inverter. Background technique [0002] The photovoltaic grid-connected inverter is a power conversion device connected between the PV photovoltaic panel and the grid, and its function is to convert the direct current generated by the photovoltaic photovoltaic panel into alternating current. For safety reasons, the inverter is required to disconnect the inverter from the grid in time when it detects some abnormal conditions. [0003] At present, the mainstream photovoltaic grid-connected inverters (such as string type and distributed photovoltaic grid-connected inverters) need to be isolated by relays on the inverter side and the grid side. When the inverter detects an abnormal situation, it will break open, cut off the inverter from the grid in time. [0004] Specifically, ...

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Problems solved by technology

Similarly, when judging the relay failure of phase B and phase C, it is necessary to collect the inverter voltage Vinv_B and Vinv_C of phase B and phase C respectively, and the grid voltage Vac_B and Vac_C of phase B and phase C, which requires three inverters The inverter voltage sampling circuit and the three power grid voltage sampling circuits, the digital processing chip (such as DSP) in the inverter also needs a corresponding number of sampling ports, resulting in an increase in hardware costs and a waste of digital processing chip resources. The voltage Vinv is generally sampled relative to the neutral point of the power grid. When the relay is disconnected, Vinv collects the floating voltage, which leads to the poor definition of the relay fault judgment thresholds ΔV1 and ΔV2, and it is easy to misjudge the relay fault.

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