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SYSTEM AND METHOD FOR IMPLEMENTING GROUND FAULT ALGORITHM FOR SOLAR INVERTER

IP.com Disclosure Number: IPCOM000246314D
Publication Date: 2016-May-27
Document File: 5 page(s) / 177K

Publishing Venue

The IP.com Prior Art Database

Abstract

The invention proposes a system and method for implementing ground fault detection algorithm for a solar inverter with a single ground fault detection circuit. The ground fault detection circuit comprises a single ground with fuse and resistors of appropriate rating. The algorithm is triggered with the detection of ground fault current above a threshold that opens all four DC switches. The DC switches are then individually closed in turn. After closing one switch there is a time delay to measure ground fault current. If current is above the threshold then that switch is opened and "tagged out". If the current is normal, then the inverter closes the next DC switch and repeats the process to locate the fault. The algorithm allows the inverter to intelligently detect the location of the ground fault with only one ground fault sensor and therefore maximizes the availability of the inverter with reduced investment.

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This is the abbreviated version, containing approximately 51% of the total text.

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SYSTEM AND METHOD FOR IMPLEMENTING GROUND FAULT ALGORITHM FOR SOLAR INVERTER

BACKGROUND

The invention is in general related to solar power generation system and in particular to a system and method for implementing ground fault detection algorithm for a solar inverter. The solar inverter typically comprises four DC buses which are connected to four PV arrays, each of which is separately grounded. Each of these buses is connected to the common DC bus of the inverter via a DC switch. A multi-ground fault circuit is used for detecting ground fault current to protect the inverter and open the DC switches on the occurrence of a fault. Each ground fault detection circuit is connected to the common DC bus on the PV array side of the DC switches to form multi-ground fault circuit, as indicated in FIG. 1. In this way, each detection circuit reports the ground fault current to the inverter controller. If any value exceeds a threshold limit, the associated DC switch could be opened and the inverter could be restarted to function with three DC switches and PV arrays. The process could be repeated if another ground fault is detected. Thus, there is a need for a cost-effective solution for detecting ground fault in the solar inverter.

FIG. 1: Multi-ground fault circuit

However, each grounding device provides information about one of four DC buses on the PV array side of the inverter DC switches. If a PV array experiences a ground fault, the respective inverter DC switch can be opened and the inverter can continue to function. If this multi ground fault detection circuit approach is replaced with a single ground fault detection circuit, detecting which

 


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PV array experienced the ground fault becomes challenging. Thus, there is a need for reducing the number of grounding devices as well as a means for detecting which PV array has experienced a ground fault.

BRIEF DESCRIPTION OF DRAWINGS

The invention discloses a system and method for implementing a ground fault detection algorithm for solar inverter, wherein:

FIG. 1 shows a multi-ground fault circuit in the solar inverter.

FIG. 2 shows a single ground fault circuit in the solar inverter.

FIG. 3 shows a ground fault algorithm in the solar inverter.

DETAILED DESCRIPTION

The invention proposes a system and method for implementing ground fault detection algorithm for a solar inverter with a single ground fault detection circuit. The ground fault detection circuit comprises a single ground with fuse and resistors of appropriate rating, as indicated in FIG. 2. The ground fault circuit is configured to handle the combined fault current of all the PV arrays.

FIG. 2: Single ground fault circuit

 


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A summation of ground fault currents from all four PV arrays is measured by single ground fault detection circuit. During ground fault scenarios, the algorithm determines the particular DC switch responsible for the highe...