Miniature grid-connected inverter leakage protection circuit

Abstract

The utility model discloses an electric leakage protection circuit of a miniature grid-connected inverter. The electric leakage protection circuit comprises a main control module, a detection module and a power-off protection module, the detection module is connected to a power supply loop of the micro grid-connected inverter and is used for detecting the vector sum of live wire current and zero wire current of the micro grid-connected inverter so as to output a first detection current signal and a second detection current signal; the main control module outputs a first level signal when receiving the first detection current signal, and outputs a second level signal when receiving the second detection current signal; the power-off protection module outputs a starting signal to control normal operation in a power supply loop of the miniature grid-connected inverter when receiving the first level signal, and outputs a stopping signal to control disconnection of the power supply loop of the miniature grid-connected inverter when receiving the second level signal. According to the invention, the leakage protection effect of the miniature grid-connected inverter is improved.

Description

Technical Field

[0001] This application relates to the technical field of protection circuits, and particularly to a leakage protection circuit for a micro grid-connected inverter. Background Art

[0002] With the rapid development of photovoltaic technology, the micro grid-connected inverter, as a core component of the solar power generation system, has become increasingly important. The micro grid-connected inverter not only realizes the efficient conversion of the direct current generated by the photovoltaic panels into alternating current and feeds it into the grid, but also has the advantages of small size, light weight, and flexible control, and is widely used in distributed photovoltaic systems.

[0003] The micro grid-connected inverter contains a large number of components such as capacitors and inductors inside. During the high-frequency operation process, these components are prone to generating leakage current. When the leakage current reaches a certain level, it will damage the internal components of the inverter and may also cause electric shock accidents, posing a safety threat to the operators and surrounding personnel. However, although some micro grid-connected inverters on the market are equipped with certain leakage protection measures, they often have problems such as low detection sensitivity and slow response speed, and cannot effectively cope with the safety hazards brought by high-frequency leakage current. Therefore, there is a defect that the leakage protection effect of the micro grid-connected inverter is poor and needs to be improved. Summary of the Utility Model

[0004] In order to improve the leakage protection effect of the micro grid-connected inverter, this application provides a leakage protection circuit for a micro grid-connected inverter.

[0005] A leakage protection circuit for a micro grid-connected inverter provided by this application adopts the following technical solutions:

[0006] A leakage protection circuit for a micro grid-connected inverter includes a main control module, a detection module, and a power-off protection module;

[0007] The detection module is connected to the power supply circuit of the micro grid-connected inverter, and detects the vector sum of the live wire current and the neutral wire current of the micro grid-connected inverter to output a first detection current signal and a second detection current signal;

[0008] The main control module is connected to the detection module and the power-off protection module. The main control module outputs a first level signal when receiving the first detection current signal, and outputs a second level signal when receiving the second detection current signal; the power-off protection module outputs an enabling signal to control the normal operation of the power supply circuit of the micro grid-connected inverter when receiving the first level signal, and outputs a shutdown signal to control the disconnection of the power supply circuit of the micro grid-connected inverter when receiving the second level signal.

[0009] By adopting the above technical solution, a leakage protection circuit is connected to the power supply circuit of the micro grid-connected inverter. When the micro grid-connected inverter is operating normally, the detection module of the present invention detects the vector sum of the live wire current and the neutral wire current in the power supply circuit of the micro grid-connected inverter in real time. When the micro grid-connected inverter is operating normally, the vector sum of the live wire current and the neutral wire current is zero. If a leakage current occurs, the vector sum of the live wire current and the neutral wire current is not zero. Therefore, the detection module outputs a first detection current signal (when the vector sum is zero) and a second detection current signal (when the vector sum is not zero) respectively through the vector sum of the live wire current and the neutral wire current in the power supply circuit of the micro grid-connected inverter. Then, the main control module outputs a first level signal and a second level signal correspondingly. When a leakage current is detected in the power supply circuit of the micro grid-connected inverter, the main control module gives a power-off protection module through the first level signal, so that the power-off protection module outputs a shutdown signal to control the disconnection of the power supply circuit of the micro grid-connected inverter, and the leakage protection of the micro grid-connected inverter is completed efficiently. Thus, the leakage protection effect of the micro grid-connected inverter is improved in this application.

[0010] Preferably, the main control module includes a main control chip. The switch state control terminal of the main control chip is connected to the input terminal of the power-off protection module, and the analog signal receiving terminal of the main control chip is connected to the output terminal of the detection module.

[0011] By adopting the above technical solution, the switch state control terminal of the main control chip is used to output a first level signal and a second level signal, and the analog signal receiving terminal of the main control chip is used to receive the first detection current signal and the second detection current signal.

[0012] Preferably, the detection module includes a current mutual induction unit and a signal comparison unit. The primary side of the current mutual induction unit is connected to the power supply circuit of the micro grid-connected inverter, the secondary side of the current mutual induction unit is connected to the first input terminal of the signal comparison unit, a threshold signal is connected to the second input terminal of the signal comparison unit, and the output terminal of the signal comparison unit is connected to the main control module.

[0013] By adopting the above technical solution, the current mutual induction unit is applied to the micro grid-connected inverter. By connecting the primary side to the measured circuit and the secondary side to the current detection device, the transformation and electrical isolation of current or voltage are realized through electromagnetic induction, providing a reliable guarantee for the measurement and protection of the power system.

[0014] Preferably, the current mutual induction unit includes a transformer.

[0015] By adopting the above technical solution, the mutual inductor is a current mutual inductor. In the current mutual inductor, the primary coil (referring to the primary side) is directly connected in series in the measured circuit to carry the large current in the measured circuit, and the current or voltage signal output by the secondary coil (referring to the secondary side) can be connected to various measuring instruments and protection devices to monitor the operating state of the power system in real time and cut off the power supply in time when a fault occurs.

[0016] Preferably, the signal comparison unit includes a comparator. The first input terminal of the comparator is the inverting input terminal, and the second input terminal of the comparator is the non-inverting input terminal.

[0017] By adopting the above technical solution, the comparator compares the magnitudes of the signals at the two input terminals and outputs a first detection current signal and a second detection current signal through the output terminal.

[0018] Preferably, the power-off protection module includes a relay and a power-off switch unit. The control terminal of the relay is connected to the live wire and the neutral wire of the micro grid-connected inverter. The controlled terminal of the relay is connected to the output terminal of the power-off switch unit, and the input terminal of the power-off switch unit is connected to the switch state control terminal of the main control chip.

[0019] By adopting the above technical solution, when the micro grid-connected inverter is operating normally, the relay is normally attracted to one end of the live wire and the neutral wire. When the detection module detects a leakage between the live wire and the neutral wire of the micro grid-connected inverter, the relay closes and stops outputting, and the output terminal of the power-off switch unit controls whether the relay is in the holding output state or the closed stop state through its controlled terminal, which is beneficial to improving the leakage protection effect of the micro grid-connected inverter.

[0020] Preferably, the power-off switch unit includes a triode. The base of the triode is connected to the RELAY_IO pin of the main control chip. The emitter of the triode is grounded, and the collector of the triode is connected to the relay.

[0021] By adopting the above technical solution, the base of the triode receives the first level signal and the second level signal from the RELAY_IO pin of the main control chip, and controls the relay to be attracted to one end of the live wire and the neutral wire of the micro grid-connected inverter (at this time, the micro grid-connected inverter is operating normally) and close and stop outputting (at this time, the micro grid-connected inverter is turned off and not operating) through the emitter to achieve the function of safety protection.

[0022] Preferably, the triode is an NPN-type triode, and a diode is connected to the controlled terminal of the relay.

[0023] By adopting the above technical solution, it is convenient to achieve power-off switch protection with high efficiency when a leakage of the inverter is found.

[0024] In summary, the present application includes at least one of the following beneficial technical effects:

[0025] 1. A leakage protection circuit is connected to the power supply circuit of the micro grid-connected inverter. When the micro grid-connected inverter is operating normally, the present invention detects, through the detection module, the vector sum of the live wire current and the neutral wire current in the power supply circuit of the micro grid-connected inverter in real time. When the micro grid-connected inverter is operating normally, the vector sum of the live wire current and the neutral wire current is zero. If there is a leakage current, the vector sum of the live wire current and the neutral wire current is not zero. Therefore, the detection module outputs a first detection current signal (corresponding to the case when the vector sum is zero) and a second detection current signal (corresponding to the case when the vector sum is not zero) through the vector sum of the live wire current and the neutral wire current in the power supply circuit of the micro grid-connected inverter. Then, the main control module outputs a first level signal and a second level signal correspondingly. When a leakage current is detected in the power supply circuit of the micro grid-connected inverter, the main control module gives a power-off protection module through the first level signal, so that the power-off protection module outputs a shutdown signal to control the disconnection of the power supply circuit of the micro grid-connected inverter, thereby efficiently providing leakage protection for the micro grid-connected inverter. Thus, the present application improves the leakage protection effect of the micro grid-connected inverter;

[0026] 2. The mutual inductor is a current mutual inductor. In the current mutual inductor, the primary coil (referring to the primary side) is directly connected in series in the measured circuit to carry the large current in the measured circuit, and the current or voltage signal output by the secondary coil (referring to the secondary side) can be connected to various measuring instruments and protection devices to monitor the operating state of the power system in real time and cut off the power supply in time when a fault occurs;

[0027] 3. The base of the triode receives the first level signal and the second level signal from the RELAY_IO pin of the main control chip, and controls the relay to attract at one end of the live wire and the neutral wire of the micro grid-connected inverter (at this time, the micro grid-connected inverter is operating normally) and turn off to stop output (at this time, the micro grid-connected inverter is turned off and not operating) through the emitter, so as to achieve the function of safety protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a circuit diagram of a leakage protection circuit for a micro grid-connected inverter.

[0029] Description of the reference numerals:

[0030] 1. Main control module; 2. Detection module; 3. Power-off protection module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The following will further describe the present application in detail with reference to the attached Figure 1 This application will be further described in detail below.

[0032] An embodiment of the present application discloses a leakage protection circuit for a micro grid-connected inverter. Refer to Figure 1 , taking the Figure 1 shown circuit diagram as an example, the leakage protection circuit for the micro grid-connected inverter includes a main control module 1, a detection module 2, and a power-off protection module 3; the detection module 2 is connected to the power supply circuit of the micro grid-connected inverter to detect the vector sum of the live wire current and the neutral wire current of the micro grid-connected inverter, so as to output a first detection current signal and a second detection current signal; the main control module 1 is connected to the detection module 2 and the power-off protection module 3, and the main control module 1 outputs a first level signal when receiving the first detection current signal and outputs a second level signal when receiving the second detection current signal; the first level signal is a high level signal, and the second level signal is a low level signal; the power-off protection module 3 outputs an enable signal to control the normal operation in the power supply circuit of the micro grid-connected inverter when receiving the first level signal, and outputs a shutdown signal to control the disconnection in the power supply circuit of the micro grid-connected inverter when receiving the second level signal.

[0033] Refer to Figure 1 , taking the Figure 1 shown circuit diagram as an example, the main control module 1 includes a main control chip U1. The switch state control terminal (RELAY_IO pin) of the main control chip U1 is connected to the input terminal of the power-off protection module 3, and the analog signal receiving terminal (ADC pin) of the main control chip U1 is connected to the output terminal of the detection module 2; the detection module 2 includes a current mutual inductance unit and a signal comparison unit. The primary side of the current mutual inductance unit is connected to the power supply circuit of the micro grid-connected inverter, the secondary side of the current mutual inductance unit is connected to the first input terminal of the signal comparison unit, the second input terminal of the signal comparison unit is connected to a threshold signal VREF, and the output terminal of the signal comparison unit is connected to the main control module 1; the current mutual inductance unit includes a mutual inductor T1; the signal comparison unit includes a comparator U2-A. The first input terminal of the comparator U2-A is the inverting input terminal, and the second input terminal of the comparator U2-A is the non-inverting input terminal; the current mutual inductance unit is applied to the micro grid-connected inverter. By connecting the primary side in the measured circuit and the secondary side in the current detection device, the transformation and electrical isolation of current or voltage are realized through electromagnetic induction, providing a reliable guarantee for the measurement and protection of the power system.

[0034] The power-off switch unit includes a triode Q1. The base of the triode Q1 is connected to the RELAY_IO pin of the main control chip U1. The emitter of the triode Q1 is grounded, and the collector of the triode Q1 is connected to a relay; the triode Q1 is an NPN-type triode Q1, and a diode D1 is connected to the controlled terminal of the relay.

[0035] The implementation principle of the leakage protection circuit of a micro grid-connected inverter in an embodiment of this application is as follows: When the circuit of the micro grid-connected inverter is operating normally, the RELAY_IO pin of the main control chip U1 outputs a first level signal of high level. The vector sum of the currents passing through the primary side L1 (connected to the live wire) / N1 (connected to the neutral wire) of the current transformer T1 is zero, and no induced voltage is output on the secondary side. Then, the comparator U2-A outputs a threshold signal VREF of the reference voltage. At this time, the voltage detected by the ADC of the main control chip U1 is within the threshold, and it is determined that there is no leakage. Then, the relay is continuously maintained in the closed state to keep normal output. When there is leakage in the output, the leakage current directly flows from the live wire to the ground. At this time, the vector sum of the currents passing through the primary side L1 / N1 of the current transformer T1 is no longer zero, and the secondary coil outputs an induced voltage Vo. Then, the comparator U2-A outputs a voltage (V_REF - nVo). When the voltage detected by the comparator U2-A exceeds the set threshold, it is determined that there is leakage in the output. As a result, the RELAY_IO pin of the main control chip U1 outputs a second level signal of low level, the triode Q1 is cut off, and the relay is turned off to stop the output to achieve the purpose of leakage protection.

[0036] The above are all the preferred embodiments of this application, and the protection scope of this application is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A leakage protection circuit for a micro grid-connected inverter, characterized in that, It includes a main control module (1), a detection module (2) and a power-off protection module (3); The detection module (2) is connected to the power supply circuit of the micro grid-connected inverter, and detects the vector sum of the live wire current and the neutral wire current of the micro grid-connected inverter to output a first detection current signal and a second detection current signal; The main control module (1) is connected to the detection module (2) and the power-off protection module (3). The main control module (1) outputs a first level signal when receiving the first detection current signal, and outputs a second level signal when receiving the second detection current signal; The power-off protection module (3) outputs an enabling signal to control the normal operation in the power supply circuit of the micro grid-connected inverter when receiving the first level signal, and outputs a shutdown signal to control the disconnection in the power supply circuit of the micro grid-connected inverter when receiving the second level signal.

2. The leakage protection circuit of a micro grid-connected inverter according to claim 1, wherein, The main control module (1) includes a main control chip. The switch state control terminal of the main control chip is connected to the input terminal of the power-off protection module (3), and the analog signal receiving terminal of the main control chip is connected to the output terminal of the detection module (2).

3. The leakage protection circuit of a micro grid-connected inverter according to claim 1, characterized in that, The detection module (2) includes a current mutual induction unit and a signal comparison unit. The primary side of the current mutual induction unit is connected to the power supply circuit of the micro grid-connected inverter. The secondary side of the current mutual induction unit is connected to the first input terminal of the signal comparison unit. The second input terminal of the signal comparison unit accesses a threshold signal, and the output terminal of the signal comparison unit is connected to the main control module (1).

4. A leakage protection circuit for a micro grid-connected inverter according to claim 3, characterized in that, The current mutual induction unit includes a mutual inductor.

5. A leakage protection circuit for a micro grid-connected inverter according to claim 3, characterized in that, The signal comparison unit includes a comparator. The first input terminal of the comparator is the inverting input terminal, and the second input terminal of the comparator is the non-inverting input terminal.

6. The leakage protection circuit of a micro grid-connected inverter according to claim 2, characterized in that, The power-off protection module (3) includes a relay and a power-off switch unit. The control terminal of the relay is connected to the live wire and the neutral wire of the micro grid-connected inverter. The controlled terminal of the relay is connected to the output terminal of the power-off switch unit, and the input terminal of the power-off switch unit is connected to the switch state control terminal of the main control chip.

7. A leakage protection circuit for a micro grid-connected inverter according to claim 6, characterized in that, The power-off switch unit includes a triode. The base of the triode is connected to the RELAY_IO pin of the main control chip. The emitter of the triode is grounded, and the collector of the triode is connected to the relay.

8. A leakage protection circuit for a micro grid-connected inverter according to claim 7, characterized in that, The triode is an NPN type triode, and a diode is connected to the controlled terminal of the relay.

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