# US 11,909,353 B2 · Ground-fault detecting device and related method

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- Number: US 11,909,353 B2
- Document ID: US11909353B2
- Status: Granted
- Kind: B2
- Application number: 17/940,743
- Filed: 2022-09-08
- Published: 2023-01-05
- Granted: 2024-02-20
- Earliest claimed: 2019-08-30
- Assignees: Kehua Hengsheng Co., Ltd.
- Applicants: Kehua Hengsheng Co., Ltd.
- Inventors: Chunbao Zeng; Peizai Hong; Wen Wei; Zhenhuang Lin; Kailong Chen
- Web page: https://patentgrep.com/patent/US11909353B2

## CPC

- H02S 50/00: Monitoring or testing of PV systems, e.g. load balancing or fault identification
- G01R 31/50: Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections (testing of sparking plugs H01T13/58)
- G01R 31/52: Testing for short-circuits, leakage current or ground faults
- H02J 3/0012: characterised by the contingency detection means in AC networks, e.g. using phasor measurement units [PMU], synchrophasors or contingency analysis
- H02J 3/381: {Dispersed generators}
- H02J 3/388: Arrangements for the handling of islanding, e.g. for disconnection or for avoiding the disconnection of power
- G01R 31/40: Testing power supplies (testing photovoltaic devices H02S50/10)
- G01R 31/42: AC power supplies
- H02J 2101/24: Photovoltaics
- Y02E 10/56: Power conversion systems, e.g. maximum power point trackers
- H02S: GENERATION OF ELECTRIC POWER BY CONVERSION OF INFRARED RADIATION, VISIBLE LIGHT OR ULTRAVIOLET LIGHT, e.g. USING PHOTOVOLTAIC [PV] MODULES (obtaining electrical energy from radioactive sources G21H1/12; light sensitive inorganic semiconductor devices H10F; light sensitive organic semiconductor devices H10K30/00; thermoelectric devices H10N10/00; pyroelectric devices H10N15/00)
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A ground-fault detecting device includes: a first detecting module, having a first input terminal, a second input terminal, and a third input terminal coupled to a first-phase electric power, a second-phase electric power, and a third-phase electric power on an AC side of a photovoltaic power generating system respectively, for sampling voltages of the first-phase electric power, the second-phase electric power, and the third-phase electric power to generate a first sampled voltage, a second sampled voltage, and a third sampled voltage respectively; and a controller, coupled to the first detecting module, for determining if a ground-fault occurs in the AC side before the photovoltaic power generating system is connected to a grid according to the first sampled voltage, the second sampled voltage, and the third sampled voltage; wherein the controller generates an alarm signal when the ground-fault occurs in the AC side.

## Claims

### Claim 1

A ground-fault detecting device, comprising:
a first detecting module, having a first input terminal, a second input terminal, and a third input terminal coupled to a first-phase electric power, a second-phase electric power, and a third-phase electric power on an AC (Alternating Current) side of a photovoltaic power generating system respectively, for sampling voltages of the first-phase electric power, the second-phase electric power, and the third-phase electric power to generate a first sampled voltage, a second sampled voltage, and a third sampled voltage respectively; and
a controller, coupled to the first detecting module, for determining if a ground-fault occurs in the AC side before the photovoltaic power generating system is connected to a grid according to the first sampled voltage, the second sampled voltage, and the third sampled voltage;
wherein the controller generates an alarm signal when the ground-fault occurs in the AC side, wherein the first detecting module comprises:
a first matching impedance device, having a first terminal coupled to the first-phase electric power;
a first grounding resistor, having a first terminal coupled to a second terminal of the first matching impedance device, and a second terminal coupled to a ground;
a second matching impedance device, having a first terminal coupled to the second-phase electric power;
a second grounding resistor, having a first terminal coupled to a second terminal of the second matching impedance device, and a second terminal coupled to the ground;
a third matching impedance device, having a first terminal coupled to the third-phase electric power;
a third grounding resistor, having a first terminal coupled to a second terminal of the third matching impedance device, and a second terminal coupled to the ground;
wherein the first sampled voltage is a voltage difference between the first terminal and the second terminal of the first grounding resistor; the second sampled voltage is the voltage difference between the first terminal and the second terminal of the second grounding resistor; the third sampled voltage is the voltage difference between the first terminal and the second terminal of the third grounding resistor.

### Claim 2 (depends on 1)

The ground-fault detecting device of claim 1, wherein the controller is arranged to obtain the first sampled voltage when a first switch is closed and a second switch and a third switch are opened, to compare the first sampled voltage to a first predetermined threshold voltage, and to generate the alarm signal when the first sampled voltage is smaller than the first predetermined threshold voltage;
the controller is further arranged to obtain the second sampled voltage when the second switch is closed and the first switch and the third switch are opened, to compare the second sampled voltage to a second predetermined threshold voltage, and to generate the alarm signal when the second sampled voltage is smaller than the second predetermined threshold voltage; and
the controller is further arranged to obtain the third sampled voltage when the third switch is closed and the first switch and the second switch are opened, to compare the third sampled voltage to a third predetermined threshold voltage, and to generate the alarm signal when the third sampled voltage is smaller than the third predetermined threshold voltage;
wherein the first sampled voltage, the second sampled voltage, and the third sampled voltage are voltage differences between the first terminal and the second terminal of the grounding resistor respectively.

### Claim 3 (depends on 2)

The ground-fault detecting device of claim 2, further comprising:
a second detecting module, having a first terminal coupled to a grounding electrode on a DC (Direct Current) side of the photovoltaic power generating system, and a second terminal coupled to the ground, for generating a first sampled current; and
a third detecting module, having a first terminal coupled to a non-grounding electrode on the DC side of the photovoltaic power generating system, and a second terminal coupled to the ground, for generating a second sampled current;
wherein the controller is further arranged to determine if the ground-fault occurs in the DC side before the photovoltaic power generating system is connected to the grid and to determine if the ground-fault occurs in the DC side and the AC side when the photovoltaic power generating system is connected to the grid according to the first sampled current and the second sampled current.

### Claim 4 (depends on 3)

The ground-fault detecting device of claim 3, wherein the second detecting module comprises:
a first controllable switch; and
a first current detecting unit, coupled to the first controllable switch in series; and
the third detecting module comprises:
a second controllable switch; and
a second current detecting unit, coupled to the second controllable switch in series;
wherein the first current detecting unit is arranged to detect the first sampled current flowing to the ground from the grounding electrode when the first controllable switch is closed and the second controllable switch is opened;
the second current detecting unit is arranged to detect the second sampled current flowing to the ground from the non-grounding electrode when the second controllable switch is closed and the first controllable switch is opened; and
the controller is further arranged to generate the alarm signal when the ground-fault occurs.

### Claim 5 (depends on 4)

The ground-fault detecting device of claim 4, wherein the alarm signal comprises a first alarm signal and a second alarm signal, and the controller comprises:
a first comparing unit, arranged to compare the first sampled current to a first predetermined threshold value, and to generate the first alarm signal for opening the first controllable switch when the first sampled current is greater than the first predetermined threshold value; and
a second comparing unit, arranged to compare the second sampled current to a second predetermined threshold value, and to generate the second alarm signal for opening the second controllable switch when the second sampled current is greater than the second predetermined threshold value.

### Claim 6 (depends on 4)

The ground-fault detecting device of claim 4, wherein the first current detecting unit comprises:
a first current sensor, arranged to directly sense the first sampled current flowing to the ground from the grounding electrode; and
the second current detecting unit comprises:
a second current sensor, arranged to directly sense the second sampled current flowing to the ground from the non-grounding electrode.

### Claim 7 (depends on 4)

The ground-fault detecting device of claim 4, wherein the second detecting module further comprises:
a first overcurrent protecting unit, coupled to the first current detecting unit in series, for opening a connection between the first current detecting unit and the grounding electrode when the ground-fault occurs; and
the third detecting module further comprises:
a second overcurrent protecting unit, coupled to the second current detecting unit in series, for opening the connection between the first current detecting unit and the non-grounding electrode when the ground-fault occurs.

### Claim 8

A photovoltaic power generating system, comprising:
a photovoltaic array, arranged to converting solar energy into a DC (Direct Current) power on a DC side;
an inverter, coupled to the photovoltaic array, for converting the DC power into an AC (Alternating Current) power on an AC side;
a plurality of switches, coupled to the inverter, for selectively connecting the AC power to a grid; and
a ground-fault detecting device, coupled between the AC side and a ground, for sampling a voltage of the AC power to detect if a ground-fault occurs in the AC side before the AC power is connected to the grid,
wherein the ground-fault detecting device comprises:
a first detecting module, having an input terminal coupled to a specific-phase electric power of the AC power on the AC side, for sampling a voltage of the specific-phase electric power to generate a sampled voltage; and
a controller, coupled to the first detecting module, for determining if a ground-fault occurs in the AC side before the AC power is connected to the grid according to the sampled voltage, wherein the first detecting module comprises:
a matching impedance device, having a first terminal coupled to the specific-phase electric power; and
a grounding resistor, having a first terminal coupled to a second terminal of the matching impedance device, and a second terminal coupled to the ground;
wherein the sampled voltage is a voltage difference between the first terminal and the second terminal of the grounding resistor.

### Claim 9 (depends on 8)

The photovoltaic power generating system of claim 8, wherein the controller is arranged to obtain the sampled voltage when a switch is closed, to compare the sampled voltage to a predetermined threshold voltage, and to generate an alarm signal when the sampled voltage is smaller than the predetermined threshold voltage; and
wherein the sampled voltage is a voltage difference between the first terminal and the second terminal of the grounding resistor respectively.

### Claim 10 (depends on 9)

The photovoltaic power generating system of claim 9, further comprising:
a second detecting module, having a first terminal coupled to a grounding electrode on the DC side, and a second terminal coupled to the ground, for generating a first sampled current; and
a third detecting module, having a first terminal coupled to a non-grounding electrode on the DC side, and a second terminal coupled to the ground, for generating a second sampled current;
wherein the controller is further arranged to determine if the ground-fault occurs in the DC side before the AC power is connected to the grid and to determine if the ground-fault occurs in the DC side and the AC side when the AC power is connected to the grid according to the first sampled current and the second sampled current.

### Claim 11 (depends on 10)

The photovoltaic power generating system of claim 10, wherein the second detecting module comprises:
a first controllable switch; and
a first current detecting unit, coupled to the first controllable switch in series; and
the third detecting module comprises:
a second controllable switch; and
a second current detecting unit, coupled to the second controllable switch in series;
wherein the first current detecting unit is arranged to detect the first sampled current flowing to the ground from the grounding electrode when the first controllable switch is closed and the second controllable switch is opened;
the second current detecting unit is arranged to detect the second sampled current flowing to the ground from the non-grounding electrode when the second controllable switch is closed and the first controllable switch is opened; and
the controller is further arranged to generate the alarm signal when the ground-fault occurs.

### Claim 12 (depends on 11)

The photovoltaic power generating system of claim 11, wherein the alarm signal comprises a first alarm signal and a second alarm signal, and the controller comprises:
a first comparing unit, arranged to compare the first sampled current to a first predetermined threshold value, and to generate the first alarm signal for opening the first controllable switch when the first sampled current is greater than the first predetermined threshold value; and
a second comparing unit, arranged to compare the second sampled current to a second predetermined threshold value, and to generate the second alarm signal for opening the second controllable switch when the second sampled current is greater than the second predetermined threshold value.