CN104917455A - Inverter and photovoltaic power system using same - Google Patents

Abstract

The invention discloses an inverter device, which comprises an inverter circuit, a control circuit and a grounding detection circuit based on a voltage stabilizer. The control circuit is used for controlling the power supply conversion of the inverter circuit. The voltage stabilizer-based ground detection circuit is used for sampling the input voltage of the direct current input power supply, and stabilizing and dividing the input voltage to generate the ground indication voltage. The potential of the output end of the voltage stabilizer is established based on the photovoltaic grounding end of the photoelectric module, and the grounding indication voltage is the voltage difference between the output end of the voltage stabilizer and the device grounding end of the inversion device. The control circuit judges whether the photoelectric module has a ground fault according to the ground indication voltage, and starts a ground protection mechanism to control the inverter circuit when the ground fault is judged to occur. The inverter can accurately detect whether the photoelectric module at the front end has a ground fault. The invention also discloses a photovoltaic power supply system.

Description

Inversion device and photovoltaic power supply system using it

technical field

The invention relates to a power conversion technology, in particular to an inverter device and a photovoltaic power supply system using the same.

Background technique

In a general photovoltaic power system, the front-end photovoltaic modules (such as solar panels) are generally installed outdoors to receive sunlight. However, the photoelectric modules installed outdoors will inevitably be affected by the climate environment, and there is a risk of damage.

For example, the photovoltaic ground terminal of the photovoltaic module may become floating due to the influence of the climate, so that the photovoltaic ground terminal of the photovoltaic module and the device ground terminal of the back-end inverter device are not at the same potential. This phenomenon is called It is the ground fault of the photoelectric module. In the case of a ground fault, a leakage current will be generated between the photovoltaic ground terminal and the device ground terminal due to the potential difference. Excessive leakage current may cause electric shock or fire to the user.

Under the existing technology, the low-frequency signal injection method or variable frequency signal injection method is generally used to detect the ground fault problem of the above-mentioned photoelectric modules. However, the existing methods require the application of complex circuit structures, and cannot accurately detect A ground fault condition occurs.

Therefore, there is a need for an inverter device and a photovoltaic power supply system using the same to solve the above existing problems.

Contents of the invention

An object of the present invention is to provide an inverter device that can accurately detect whether a ground fault occurs in a front-end photoelectric module.

Another object of the present invention is to provide a photovoltaic power supply system that can accurately detect whether a ground fault occurs in a front-end photoelectric module.

In order to achieve the above object, the present invention provides an inverter device, adapted to receive a DC input power from a photoelectric module, and generate an AC output power according to the DC input power, wherein the inverter device includes:

an inverter circuit for converting the DC input power into the AC output power;

a control circuit, coupled to the inverter circuit, for controlling the power conversion of the inverter circuit; and

A voltage stabilizer-based ground detection circuit, coupled to the DC input power supply and the control circuit, is used to sample an input voltage of the DC input power supply, and to stabilize and divide the input voltage. voltage, thereby generating a ground indicating voltage, wherein the potential of an output terminal of the voltage regulator is established based on a photovoltaic ground terminal of the photovoltaic module, and the ground indicating voltage is the output terminal of the voltage regulator The voltage difference between a device ground terminal of the inverter device,

Wherein, the control circuit judges whether a ground fault occurs in the photoelectric module according to the ground indication voltage, and activates a ground fault protection mechanism to control the inverter circuit when it is determined that the ground fault occurs.

Preferably, the control circuit judges whether the grounding indication voltage is within a normal voltage range, and if the grounding indication voltage is within the normal voltage range, the control circuit determines that the grounding does not occur in the photoelectric module fault, and if the ground indication voltage is outside the normal voltage range, the control circuit determines that the ground fault occurs in the photoelectric module.

Preferably, said regulator-based ground detection circuit comprises:

a power conversion unit for sampling the input voltage and generating a reference voltage according to the input voltage; and

A detection unit, coupled to the power conversion unit to receive the reference voltage, stabilize the reference voltage to generate a regulated voltage, and generate the ground indication voltage according to the regulated voltage, wherein the The stabilized voltage is the voltage difference between the output terminal of the voltage regulator and a photovoltaic ground terminal of the photovoltaic module.

Preferably, the detection unit includes:

The voltage regulator, the input terminal of the voltage regulator receives the reference voltage, and the output terminal of the voltage regulator outputs the regulated voltage;

A first resistor, the first terminal of the first resistor is coupled to the output terminal of the voltage regulator, and the second terminal of the first resistor is coupled to the device ground terminal of the inverter device, wherein the the ground indicating voltage is a voltage across the first resistor; and

A second resistor, the first end of the second resistor is coupled to the second end of the first resistor and the device ground, and the second end of the second resistor is coupled to the photovoltaic module of the photoelectric module ground terminal.

Preferably, the detection unit further includes:

a third resistor, the first terminal of the third resistor receives the reference voltage, and the second terminal of the third resistor is coupled to the input terminal of the voltage regulator; and

A fourth resistor, the first terminal of the fourth resistor is coupled to the second terminal of the third resistor, and the second terminal of the fourth resistor is coupled to the output terminal of the voltage regulator and the first terminal the first end of a resistor.

In order to achieve another purpose of the present invention, the present invention provides a photovoltaic power supply system, comprising:

a photovoltaic module for generating a DC input power supply, wherein the photovoltaic module has a photovoltaic ground; and

An inverter, coupled to the photoelectric module, is adapted to convert the DC input power into an AC output power, wherein the inverter has a device ground, and the inverter includes:

an inverter circuit for converting the DC input power into the AC output power;

a control circuit, coupled to the inverter circuit, for controlling the power conversion of the inverter circuit; and

A ground detection circuit based on a voltage regulator, coupled to the inverter circuit and the control circuit, is used to sample an input voltage of the DC input power supply, and to stabilize and divide the input voltage voltage, thereby generating a ground indicating voltage, wherein the potential of an output terminal of the voltage regulator is established based on the photovoltaic ground terminal, the ground indicating voltage is the output terminal of the voltage regulator and the device The voltage difference between the ground terminals,

Wherein, the control circuit judges whether a ground fault occurs in the photoelectric module according to the ground indication voltage, and activates a ground fault protection mechanism to control the inverter circuit when it is determined that the ground fault occurs.

Preferably, the control circuit judges whether the grounding indication voltage is within a normal voltage range, and if the grounding indication voltage is within the normal voltage range, the control circuit determines that the grounding does not occur in the photoelectric module fault, and if the ground indication voltage is outside the normal voltage range, the control circuit determines that the ground fault occurs in the photoelectric module.

Preferably, said regulator-based ground detection circuit comprises:

a power conversion unit for sampling the input voltage and generating a reference voltage according to the input voltage; and

A detection unit, coupled to the power conversion unit to receive the reference voltage, stabilize the reference voltage to generate a regulated voltage, and generate the ground indication voltage according to the regulated voltage, wherein the The stabilized voltage is the voltage difference between the output terminal of the voltage regulator and a photovoltaic ground terminal of the photovoltaic module.

Preferably, the detection unit includes:

The voltage regulator, the input terminal of the voltage regulator receives the reference voltage, and the output terminal of the voltage regulator outputs the regulated voltage;

A first resistor, the first terminal of the first resistor is coupled to the output terminal of the voltage regulator, and the second terminal of the first resistor is coupled to the device ground terminal of the inverter device, wherein the the ground indicating voltage is a voltage across the first resistor; and

A second resistor, the first end of the second resistor is coupled to the second end of the first resistor and the device ground, and the second end of the second resistor is coupled to the photovoltaic module of the photoelectric module ground terminal.

Preferably, the detection unit further includes:

a third resistor, the first terminal of the third resistor receives the reference voltage, and the second terminal of the third resistor is coupled to the input terminal of the voltage regulator; and

A fourth resistor, the first terminal of the fourth resistor is coupled to the second terminal of the third resistor, and the second terminal of the fourth resistor is coupled to the output terminal of the voltage regulator and the first terminal the first end of a resistor.

Compared with the prior art, the inverter device of the present invention and the photovoltaic power supply system using it can stabilize and divide the input voltage through the ground detection circuit based on the voltage stabilizer, so as to generate an indicating photoelectric The ground indication voltage of the voltage difference between the photovoltaic ground terminal of the module and the output terminal of the voltage regulator. Wherein, the inverter device can judge whether a ground fault occurs in the photoelectric module according to whether the ground indication voltage is within a normal voltage range, and activate a corresponding protection mechanism according to the judgment result.

Description of drawings

FIG. 1 is a schematic diagram of a photovoltaic power supply system according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of a ground detection circuit according to an embodiment of the invention.

【Symbol Description】

10: Photovoltaic power system

100: inverter device

110: inverter circuit

120: Control circuit

130: Ground detection circuit

132: Power conversion unit

134: Detection unit

ACout: AC output power

DCin: DC input power

EG: Grid

GNDd: device ground

GNDp: Photovoltaic ground terminal

I: leakage current

Iin: input current

Iout: output current

PVm: Photoelectric module

OT: the output terminal of the voltage regulator

R1, R2, R3, R4: Resistors

Sc: control signal

VR: voltage regulator

Vd: ground indication voltage

Vin: input voltage

Vout: output voltage

Vref: reference voltage

Vs: regulated voltage

Detailed ways

In order to make the content disclosed in the present invention more understandable, the following specific embodiments are taken as examples that the disclosure of the present invention can actually be implemented. In addition, wherever possible, components/members/steps with the same reference numerals are used in the drawings and embodiments to represent the same or similar parts.

FIG. 1 is a schematic diagram of a photovoltaic power supply system according to an embodiment of the present invention. Please refer to FIG. 1 , in this embodiment, a photovoltaic power supply system 10 includes a photovoltaic module PVm and an inverter device 100 . The photovoltaic module (photovoltaic module) PVm is used to convert solar energy into a DC input power supply DCin (including input voltage Vin and input current Iin) in the form of electrical energy. The inverter device 100 receives the DC input power DCin output from the photoelectric module PVm, and generates an AC output power ACout (including the output voltage Vout and the output current Iout) according to the DC input power DCin. Wherein, the photovoltaic power supply system of this embodiment is a photovoltaic grid-connected system, and the AC output power of the inverter device is provided to the grid EG connected in parallel at the rear end, but it is not limited thereto, and a battery can also be connected to the rear end of the inverter device system or a lighting system.

In this embodiment, the inverter device 100 includes an inverter circuit 110 , a control circuit 120 and a ground detection circuit 120 . The inverter circuit 110 receives the DC input power DCin from the photovoltaic module PVm, and is used for converting the DC input power DCin into the AC output power ACout. Wherein, the circuit configuration of the inverter circuit 110 may be half-bridge asymmetrical, half-bridge symmetric, full-bridge or other feasible inverter circuit configurations, which is not limited in the present invention.

The control circuit 120 is coupled to the inverter circuit 110 for providing a control signal Sc to control the power conversion operation of the inverter circuit 110. The control signal Sc can be a pulse width modulation for controlling the switching period of the inverter circuit 110. variable signal (PWM signal), but the present invention is not limited thereto.

The circuit structure of the ground detection circuit 130 in this embodiment is based on a voltage regulator, which is coupled to the inverter circuit 110 and the control circuit 120 . The ground detection circuit 130 is used for sampling the input voltage Vin of the DC input power supply DCin, and stabilizes and divides the input voltage Vin by means of a circuit structure of a voltage regulator (detailed illustration in subsequent embodiments), so as to generate a ground indication The voltage Vd is given to the control circuit 120 . Therefore, the control circuit 120 can judge whether the photovoltaic module PVm has a ground fault according to the ground indication voltage Vd (that is, the potential of the photovoltaic ground terminal GNDp of the photovoltaic module PVm is not equal to the potential of the device ground terminal GNDd of the inverter device 100), And when it is determined that the photovoltaic module PVm has a ground fault, the ground protection mechanism is activated to control the inverter circuit 110, so as to avoid electric shock or fire caused by the ground fault of the photovoltaic module PVm.

In this embodiment, the ground indication voltage Vd generated by the ground detection circuit 130 is the voltage difference between the output terminal of the voltage regulator and the device ground terminal GNDd of the inverter device 100 . Wherein, since the voltage of the output terminal of the voltage regulator is established based on the photovoltaic ground terminal GNDp of the photovoltaic module PVm, the change of the ground indication voltage Vd can indicate whether the potentials of the photovoltaic ground terminal GNDp and the device ground terminal GNDd are equal. For example, the control circuit 120 will determine whether the ground indication voltage Vd is within the normal voltage range (which can be defined by the designer), and if the ground indication voltage Vd is within the normal voltage range, the control circuit 120 will determine that the photoelectric module PVm is not grounded. Fault. On the contrary, if the ground indication voltage Vd is outside the normal voltage range, the control circuit 120 will determine that the ground fault occurs in the photoelectric module PVm.

The specific architecture of the ground detection circuit 130 according to the embodiment of the present invention will be described below with reference to FIG. 2 . Wherein, FIG. 2 is a schematic diagram of a ground detection circuit according to an embodiment of the present invention.

Please refer to FIG. 1 and FIG. 2 at the same time. The ground detection circuit 130 of this embodiment includes a power conversion unit 132 and a detection unit 134 . The power conversion unit 132 is coupled to the input terminal of the inverter circuit 110 to sample the input voltage Vin, and perform power conversion on the input voltage Vin, and generate a reference voltage Vref according to the input voltage Vin.

The detection unit 134 is coupled to the power conversion unit 132 to receive the reference voltage Vref. Wherein, the detection unit 134 stabilizes the reference voltage Vref to generate the regulated voltage Vs, and generates the ground indication voltage Vd according to the regulated voltage Vs. Here, the regulated voltage Vs is the voltage difference between the output terminal OT of the voltage regulator and the photovoltaic ground terminal GNDp of the photovoltaic module PVm.

More specifically, the detection unit 134 can be selected to be composed of a voltage regulator VR and resistors R1 - R4 . The voltage regulator VR receives the reference voltage Vref from the power conversion unit 132 through the resistor R3, and performs voltage stabilization based on the reference voltage Vref, so as to output the regulated voltage Vs at the output terminal OT.

A first end of the resistor R1 is coupled to the output end of the voltage regulator VR, and a second end of the resistor R1 is coupled to the device ground GNDd of the inverter device 100 . The first end of the resistor R2 is coupled to the second end of the resistor R1 and the device ground GNDd, and the second end of the resistor R2 is coupled to the photovoltaic ground GNDp. A first terminal of the resistor R3 receives the reference voltage Vref, and a second terminal of the resistor R3 is coupled to the input terminal of the voltage regulator VR. A first terminal of the resistor R4 is coupled to a second terminal of the resistor R3, and a second terminal of the resistor R4 is coupled to the output terminal of the voltage regulator VR and the first terminal of the resistor R1.

In this embodiment, the ground indication voltage Vd is the voltage across the resistor R1, and the regulated voltage Vs is the voltage across the resistors R1 and R2, which is also the voltage difference between the output terminal OT and the photovoltaic ground terminal GNDp.

In detail, when the photovoltaic module PVm does not have a ground fault, the photovoltaic ground terminal GNDp and the device ground terminal GNDd basically have the same potential. Therefore, in the detection unit 134 , the resistor R2 is in a short-circuit state, so that the voltage value of the ground indication voltage Vd is the same as the voltage value of the regulated voltage Vs. Since the regulated voltage Vs is a fixed voltage value, the designer can set the corresponding normal voltage range according to the rated output of the voltage regulator VR, so that the voltage value of the ground indication voltage Vd falls within the normal voltage range. In this way, the control circuit 120 can determine that the photoelectric module PVm does not have a ground fault according to the ground indication voltage Vd.

On the other hand, when a ground fault occurs in the photovoltaic module PVm, the photovoltaic ground terminal GNDp and the device ground terminal GNDd will have different potentials. In other words, the device ground terminal GNDd and the photovoltaic ground terminal GNDp generate a leakage current I passing through the resistor R2, thereby creating a voltage difference between the two ends of the resistor R2. It should be noted here that the direction of the arrow of the leakage current I is only indicative, and the leakage current I may also flow from the photovoltaic ground terminal GNDp to the device ground terminal GNDd under different ground fault conditions.

At this time, the voltage across the resistor R2 will increase in response to the leakage current I flowing through it. Since the regulated voltage Vs is a fixed voltage value, the voltage across the resistor R1 (ie, the ground indication voltage Vd) will decrease correspondingly in response to the rise in the voltage across the resistor R2. If the leakage current I exceeds a certain amount of current, the ground indication voltage Vd will increase or drop beyond the normal voltage range, so that the control circuit 120 determines that the photoelectric module PVm has a ground fault according to the ground indication voltage Vd.

For example, if the regulated voltage Vs of the rated output of the voltage regulator VR is 2.5V, a leakage current I of 1mA will be generated between the photovoltaic ground terminal GNDp and the device ground terminal GNDd in the ground fault state. The resistance values of the resistors R1 and R2 are selected as 1kΩ, and the normal voltage range is selected as 2V˜3V. At this time, the resistor R2 will respond to the leakage current of 1mA to establish a cross voltage of 1V, so that the cross voltage/ground indication voltage Vd of the resistor R1 drops from 2.5V to 1.5V. Therefore, the control circuit 120 determines that the ground fault occurs in the photoelectric module PVm according to the ground indication voltage Vd.

To sum up, the embodiment of the present invention proposes an inverter device and a photovoltaic power supply system using it, which can stabilize and divide the input voltage by using a voltage stabilizer-based ground detection circuit to generate A ground indicating voltage indicating the voltage difference between the device ground terminal GNDd of the inverter device 100 and the output terminal of the regulator. Wherein, the inverter device can judge whether the photoelectric module has a ground fault according to whether the ground indication voltage is within a normal voltage range, and activate a corresponding protection mechanism according to the judgment result.

What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot limit the scope of rights of the present invention. Therefore, equivalent changes made according to the patent scope of the present invention still fall within the scope of the present invention.

Claims (10)

1. an inverter, is suitable for receiving a direct-current input power supplying from an optical-electric module, and produces an interchange out-put supply according to described direct-current input power supplying, and it is characterized in that, described inverter comprises:

One inverter circuit, in order to be converted to described interchange out-put supply by described direct-current input power supplying;

One control circuit, couples described inverter circuit, in order to control the Power convert of described inverter circuit; And

One ground connection circuit for detecting based on pressurizer, couple described direct-current input power supplying and described control circuit, in order to sample an input voltage of described direct-current input power supplying, and voltage stabilizing and dividing potential drop are carried out to described input voltage, use generation one ground connection instructed voltage, the current potential of one output of wherein said pressurizer set up based on a photovoltaic earth terminal of described optical-electric module, described ground connection instructed voltage is the voltage difference between the described output of described pressurizer and a device earth terminal of described inverter

Wherein, according to described ground connection instructed voltage, described control circuit judges whether described optical-electric module one earth fault occurs, and in judging to enable a ground protection mechanism to control described inverter circuit when there is described earth fault.

2. inverter according to claim 1, it is characterized in that, described control circuit judges whether described ground connection instructed voltage is positioned at a normal voltage range, if described ground connection instructed voltage is positioned at described normal voltage range, described control circuit judges that described earth fault does not occur described optical-electric module, if and described ground connection instructed voltage is positioned at outside described normal voltage range, described control circuit judges that described earth fault occurs described optical-electric module.

3. inverter according to claim 1, is characterized in that, described ground connection circuit for detecting based on pressurizer comprises:

One power conversion unit, in order to sample described input voltage, and produces a reference voltage according to described input voltage; And

One detecting unit, couple described power conversion unit to receive described reference voltage, voltage stabilizing is carried out to produce a voltage of voltage regulation to described reference voltage, and produce described ground connection instructed voltage according to described voltage of voltage regulation, wherein said voltage of voltage regulation is the voltage difference between the output of described pressurizer and a photovoltaic earth terminal of described optical-electric module.

4. inverter according to claim 3, is characterized in that, described detecting unit comprises:

Described pressurizer, the input of described pressurizer receives described reference voltage, and the output of described pressurizer exports described voltage of voltage regulation;

One first resistance, the first end of described first resistance couples the output of described pressurizer, and the second end of described first resistance couples the device earth terminal of described inverter, and wherein said ground connection instructed voltage is the cross-pressure of described first resistance; And

One second resistance, the first end of described second resistance couples the second end of described first resistance and described device earth terminal, and the second end of described second resistance couples the photovoltaic earth terminal of described optical-electric module.

5. inverter according to claim 4, is characterized in that, described detecting unit more comprises:

One the 3rd resistance, the first end of described 3rd resistance receives described reference voltage, and the second end of described 3rd resistance couples the input of described pressurizer; And

One the 4th resistance, the first end of described 4th resistance couples the second end of described 3rd resistance, and the second end of described 4th resistance couples the output of described pressurizer and the first end of described first resistance.

6. a photovoltaic power supply system, is characterized in that, comprising:

One optical-electric module, in order to produce a direct-current input power supplying, wherein said optical-electric module has a photovoltaic earth terminal; And

One inverter, couples described optical-electric module, is suitable for described direct-current input power supplying to be converted to an interchange out-put supply, and wherein said inverter has a device earth terminal, and described inverter comprises:

One inverter circuit, in order to be converted to described interchange out-put supply by described direct-current input power supplying;

One control circuit, couples described inverter circuit, in order to control the Power convert of described inverter circuit; And

One ground connection circuit for detecting based on pressurizer, couple described inverter circuit and described control circuit, in order to sample an input voltage of described direct-current input power supplying, and voltage stabilizing and dividing potential drop are carried out to described input voltage, use generation one ground connection instructed voltage, the current potential of one output of wherein said pressurizer set up based on described photovoltaic earth terminal, and described ground connection instructed voltage is the voltage difference between the described output of described pressurizer and described device earth terminal

Wherein, according to described ground connection instructed voltage, described control circuit judges whether described optical-electric module one earth fault occurs, and in judging to enable a ground protection mechanism to control described inverter circuit when there is described earth fault.

7. photovoltaic power supply system according to claim 6, it is characterized in that, described control circuit judges whether described ground connection instructed voltage is positioned at a normal voltage range, if described ground connection instructed voltage is positioned at described normal voltage range, described control circuit judges that described earth fault does not occur described optical-electric module, if and described ground connection instructed voltage is positioned at outside described normal voltage range, described control circuit judges that described earth fault occurs described optical-electric module.

8. photovoltaic power supply system according to claim 6, is characterized in that, described ground connection circuit for detecting based on pressurizer comprises:

One power conversion unit, in order to sample described input voltage, and produces a reference voltage according to described input voltage; And

One detecting unit, couple described power conversion unit to receive described reference voltage, voltage stabilizing is carried out to produce a voltage of voltage regulation to described reference voltage, and produce described ground connection instructed voltage according to described voltage of voltage regulation, wherein said voltage of voltage regulation is the voltage difference between the output of described pressurizer and a photovoltaic earth terminal of described optical-electric module.

9. photovoltaic power supply system according to claim 8, is characterized in that, described detecting unit comprises:

Described pressurizer, the input of described pressurizer receives described reference voltage, and the output of described pressurizer exports described voltage of voltage regulation;

One first resistance, the first end of described first resistance couples the output of described pressurizer, and the second end of described first resistance couples the device earth terminal of described inverter, and wherein said ground connection instructed voltage is the cross-pressure of described first resistance; And

One second resistance, the first end of described second resistance couples the second end of described first resistance and described device earth terminal, and the second end of described second resistance couples the photovoltaic earth terminal of described optical-electric module.

10. photovoltaic power supply system according to claim 9, is characterized in that, described detecting unit more comprises:

One the 3rd resistance, the first end of described 3rd resistance receives described reference voltage, and the second end of described 3rd resistance couples the input of described pressurizer; And

One the 4th resistance, the first end of described 4th resistance couples the second end of described 3rd resistance, and the second end of described 4th resistance couples the output of described pressurizer and the first end of described first resistance.