TWI785446B - Bidirectional solid-state circuit breaker applied to dc microgrid - Google Patents

Abstract

A bidirectional solid-state circuit breaker applied to a DC microgrid includes: a power supply module for outputting a stable DC voltage; a short circuit switch, when a short circuit occurs in the DC microgrid, a reverse current is obtained to make the short-circuit switch turns and forms a open circuit; a coupled inductor includes two windings, and the two windings are in reverse coupling; a snubber circuit is used to suppress a surge, which includes a commutation capacitor to generate a reverse current; and a connection circuit. When the connection circuit is operating normally, the short-circuit switch is turned on and generates a maintenance current to keep the short-circuit switch in an on state. When the connection circuit is short-circuited, the snubber circuit generates the reverse current.

Description

Bidirectional solid-state circuit breaker for DC microgrid

The present invention relates to a bidirectional solid-state circuit breaker applied to a DC microgrid, and in particular to a bidirectional solid-state circuit breaker that uses solid-state switching elements to achieve circuit breaker protection and is applied to a DC microgrid.

In order to ensure the stability of power supply, the power supply device that supplies power to electronic devices usually includes a short circuit protection circuit, which is used to stop power supply to electronic devices in case of short circuit, so as to avoid overcurrent damage caused by short circuit, while traditional short circuit protection The circuit is mainly used to transmit the short-circuit signal to the primary side of the conversion module when the electronic system connected to the secondary side of the conversion module is short-circuited, so as to stop the conversion module from performing electric energy conversion. However, during the transmission of the signal, the components on the secondary side of the conversion module may have been damaged.

Traditional DC circuit breakers are usually switched mechanically to break the circuit. When the circuit breaks or overcurrent occurs, it is easy to generate an arc and increase the risk of failure of the protection circuit. The life of the circuit breaker is short and the reliability is low after a failure. Power electronics technology cannot prolong its service life. If a solid-state circuit is used for DC current protection, although the solid-state switching element can prolong the life of the circuit breaker, it is often necessary to judge the protection condition through current detection or other sensing circuits during the process. In addition to the high cost of the circuit, the sensing circuit will also affect whether the circuit breaker can operate normally. At the same time, it must also solve the high voltage stress on the power electronic components caused by the circuit breaker, so the relative benefit is not high. Therefore, it is currently developing solid-state DC current circuit breakers still have a lot of room for improvement, and there are many challenges in reducing costs and improving efficiency.

In addition, in the current foreign research, the solid-state DC current circuit breaker mostly adopts the coupling inductor method, which can naturally suppress the short-circuit current, and at the same time integrates the silicon-controlled rectifier Components, using the conduction current lower than the maintenance current to isolate the fault, reduce the complexity of the controller and increase the reliability, but most of the research lacks the functional design of bidirectional protection, and also lacks the filter function, which cannot reduce the power electronics on the DC grid. The ripple current problem generated by the converter.

The present invention provides a bidirectional solid-state circuit breaker applied to a DC micro-grid. Its purpose is to use solid-state switching elements to achieve the effect of circuit breaker protection. The coupling inductor is integrated to naturally suppress the short-circuit current of the switch and reduce the current stress of the switch. At the same time, it uses The natural cut-off characteristics of silicon-controlled rectifier components can reduce the complexity of its control circuit. The structure is composed of a symmetrical circuit design and a group of coupled inductors. Compared with traditional mechanical circuit breakers, the size and weight are smaller and the life is better. The filter function can be integrated to reduce the ripple current problem generated by the power electronic converter on the DC grid.

A bidirectional solid-state circuit breaker applied to a DC micro-grid of the present invention includes: a power supply module for outputting a DC voltage of stable DC power; a short-circuit switch including a control terminal, wherein the control terminal is electrically connected to the power supply The module, when a short circuit occurs in a DC microgrid, obtains a reverse current to turn the short circuit switch and form a circuit break; a coupled inductor electrically connects the short circuit switch, including two windings, electrically connects the short circuit a switch, and the two windings form reverse coupling; a snubber circuit, electrically connected to the coupling inductor, used to suppress a surge circuit, including a commutation capacitor, used to generate a reverse current; and a connecting circuit, It has a third terminal and a fourth terminal, wherein the third terminal is electrically connected to the coupling inductor, and the fourth terminal is electrically connected to a negative output terminal of the power module. When the connection circuit operates normally, the short circuit The switch is turned on and generates a holding current to keep the short-circuit switch in a turned-on state. When the connection circuit is short-circuited, the snubber circuit generates the reverse current.

In an embodiment of the present invention, the above-mentioned short-circuit switch is a silicon controlled rectifier (Silicon Controlled Rectifier, SCR).

In one embodiment of the present invention, the control end of the above-mentioned short-circuit switch is a gate of the silicon-controlled rectifier, and the first end is a positive electrode of the silicon-controlled rectifier. pole, and the second end is a negative pole of the silicon controlled rectifier.

In one embodiment of the present invention, the above coupled inductor further includes: a first winding and a second winding, the first winding has a fifth end and a sixth end, the second winding has a seventh end and an eighth end, the sixth end and the eighth end are connected to one end of the buffer circuit.

In one embodiment of the present invention, the above buffer circuit is an RCD clamp (Resistor Capacitor Diode clamp, RCD clamp) circuit.

In an embodiment of the present invention, the above-mentioned RCD clamping circuit includes the commutation capacitor, a resistor, and a diode.

In an embodiment of the present invention, one end of the buffer circuit is electrically connected to the coupling inductor, and the other end is electrically connected to the power module.

In one embodiment of the present invention, when the DC microgrid is on, the short-circuit switch measures the holding current to keep the DC microgrid on.

In one embodiment of the present invention, when the DC microgrid is disconnected, the snubber circuit generates the reverse current to convert the maintaining current into a negative current, and the short-circuit switch automatically shuts off when measuring the negative current. On, the DC microgrid is disconnected.

The present invention also provides a bidirectional solid-state circuit breaker applied to a DC microgrid, including: a power supply module for outputting a DC voltage of stable DC power; a short-circuit switch, which is a silicon-controlled rectifier, including a control terminal, a A first terminal and a second terminal, the control terminal is a gate of the silicon controlled rectifier, the first terminal is a positive terminal of the silicon controlled rectifier, and the second terminal is a negative terminal of the silicon controlled rectifier, wherein The control terminal is electrically connected to the power module, and when a short circuit occurs in a DC microgrid, a reverse current is obtained to turn the short circuit switch and form a circuit break; a coupling inductor is electrically connected to the short circuit switch, including: A first winding and a second winding, the first winding has a fifth end and a sixth end, the second winding has a seventh end and an eighth end, the sixth end and the eighth end are connected One end of a buffer circuit, the fifth end is electrically connected to the short-circuit switch, and the first winding and the second winding form reverse coupling; the buffer circuit is an RCD clamp flyback converter circuit, electrically Connect the coupling inductor to suppress a surge circuit, which includes a resistor, a diode and a commutation capacitor, to generate a reverse current; and a connecting circuit with a third terminal and a fourth terminal , wherein the third terminal is electrically connected to the coupling inductor, and the fourth terminal is electrically connected to a negative output terminal of the power module. When the connection circuit operates normally, the short-circuit switch is turned on and generates a holding current, so that the The short-circuit switch remains on, and when the connecting circuit is short-circuited, the snubber circuit generates the reverse current; wherein, when the DC microgrid is disconnected, the snubber circuit generates the reverse current to convert the holding current into a negative current , when the short-circuit switch measures the negative current, it is automatically disconnected, and the DC microgrid is disconnected.

The effect of the present invention is to solve the problems of poor service life and slow speed of mechanical DC circuit breakers. When the DC power grid application market begins to grow rapidly in the future, it will help to obtain market opportunities and popularize applications, and reduce the complexity of the controller. This creation integrates coupled inductors to naturally suppress the short-circuit current of the switch. At the same time, it uses the natural cut-off characteristics of the silicon-controlled rectifier to reduce the complexity of its control circuit and improve the reliability of the circuit. It also has the function of a power filter. This creation can be integrated Inductors and capacitors can be equivalent to a low-pass and band-stop filter, and reduce the ripple current problem generated by the power electronic converter on the DC grid.

110: Power module

1101: Positive output terminal

1102: Negative output terminal

120: Short circuit switch

121: Control terminal

122: first end

123: second end

130: coupled inductance

131: First winding

1311: fifth end

1312: sixth end

132: Second winding

1321: seventh end

1322: eighth end

140: buffer circuit

141: commutation capacitor

142: resistance

143: Diode

150: Connect the circuit

1501: the third end

1502: the fourth terminal

210: reverse current

A: Reverse current value

B: current value

Fig. 1 is a circuit block diagram of a bidirectional solid-state circuit breaker applied to a DC microgrid according to the present invention.

Fig. 2 is a circuit diagram of a bidirectional solid-state circuit breaker applied to a DC microgrid according to the present invention.

Fig. 3 is a schematic diagram of current variation of a bidirectional solid-state circuit breaker applied to a DC microgrid according to the present invention.

In order to make the above-mentioned features and advantages of the present invention more comprehensible, the following specific embodiments are described in detail in conjunction with the accompanying drawings.

Fig. 1 is a kind of double grid applied to DC microgrid according to the present invention A circuit block diagram of a solid state circuit breaker. In Fig. 1, the bidirectional solid-state circuit breaker applied to the DC microgrid includes: a power module 110, which is used to output a stable DC voltage; a short-circuit switch 120, when the DC microgrid operates normally 120 forms a path, and when a short circuit occurs in the DC microgrid, the short circuit switch 120 is turned around to form a circuit break; a coupled inductor 130 includes two windings, and the two windings form reverse coupling; a snubber circuit 140 , used to suppress the surge circuit and generate a reverse current; and a connection circuit 150, when the connection circuit 150 is in normal operation, the short circuit switch 120 is turned on and generates a holding current, so that the short circuit switch 120 remains in the conduction state, when the connection circuit 150 is in normal operation When the connection circuit 150 is short-circuited, the snubber circuit 140 generates the reverse current.

The short-circuit switch is a Silicon Controlled Rectifier (SCR), and the SCR is a three-terminal device, which further includes the control terminal, a first terminal, and a second terminal.

The control terminal of the short-circuit switch is a gate of the SCR silicon-controlled rectifier, the first terminal is a positive terminal of the SCR silicon-controlled rectifier, and the second terminal is a negative terminal of the silicon-controlled rectifier.

In addition, the SCR silicon-controlled rectifier can be used as a large current control in the DC microgrid, and has control elements for phase control, time delay and temperature control.

The coupled inductor in this system also includes: a first winding and a second winding, the first winding has a fifth end and a sixth end, the second winding has a seventh end and an eighth end, The sixth end and the eighth end are connected to one end of the buffer circuit.

Wherein, the coupled inductor includes a first winding, a second winding and a magnetic material; wherein: the first winding is a flat metal wire wound in a helical shape, and a second winding is arranged at both ends of the first winding. An upper electrode portion of the winding and a lower electrode portion of the first winding; the second winding is a flat metal wire wound in a helical shape, and the diameter of the second winding is the same as that of the first winding, and the number of turns is also the same, And the two ends of the second winding are respectively provided with the upper end electrode part of the second winding and the lower end electrode of the second winding part, make the axes of the first winding and the second winding overlap and rotate in the same direction to be helically combined, so that the turns of the first winding and the second winding are staggered and overlapped, so that the first winding and the second winding are each There is a good overlap between the turns, so as to avoid misalignment of the wires of the turns of the first winding and the second winding.

The snubber circuit in this system is an RCD clamp flyback converter (Resistor Capacitor Diode clamp, RCD clamp) circuit.

Wherein, the RCD clamping circuit includes the commutation capacitor, a resistor, and a diode.

In the DC microgrid, when the transistor (MOSFET) in the circuit changes from ON to OFF, a large surge voltage (spike noise) will be generated. This surge voltage is applied between the drain and source of the transistor (MOSFET), so if the generated surge voltage exceeds the withstand voltage of the transistor (MOSFET), it may cause damage to the transistor (MOSFET). In order to prevent transistor (MOSFET) from being damaged, a snubber circuit composed of RCD (resistance, capacitance, diode) is inserted to suppress surge voltage.

When the DC microgrid is on, the short-circuit switch measures the holding current to keep the DC microgrid on.

When the DC micro-grid is disconnected, the buffer circuit generates the reverse current to convert the maintaining current into a negative current, and the short-circuit switch automatically disconnects when measuring the negative current, and the DC micro-grid is disconnected.

Fig. 2 is a circuit diagram of a bidirectional solid-state circuit breaker applied to a DC microgrid according to the present invention. A bidirectional solid-state circuit breaker for DC micro-grids, including: a power supply module 110 for outputting a DC voltage of stable DC power, with a positive output terminal 1101 and a negative output terminal 1102; a short-circuit switch 120, which is a The silicon controlled rectifier includes a control terminal 121, a first terminal 122 and a second terminal 123, the control terminal 121 is a gate of the silicon controlled rectifier, the first terminal 122 is a positive terminal of the silicon controlled rectifier, And the second end 123 is a negative pole of the silicon controlled rectifier, wherein the control end 121 is electrically connected to the power module 110, when a short circuit occurs in a DC microgrid, a reverse current 210 is obtained to make the short circuit switch 120 turn, and form a circuit break; a coupled inductor 130, electrically connected to the short circuit switch 120, including: a The first winding 131 and a second winding 132, the first winding 131 has a fifth end 1311 and a sixth end 1312, the second winding 132 has a seventh end 1321 and an eighth end 1322, the sixth End 1312 and the eighth end 1322 are connected to one end of a buffer circuit 140, the fifth end 1311 is electrically connected to the short circuit switch 120, and the first winding 131 and the second winding 132 form reverse coupling; the buffer circuit 140 , is an RCD clamp flyback converter circuit electrically connected to the coupled inductor 130 to suppress a surge circuit, which includes the commutation capacitor 141, a resistor 142, and a diode 143 for Generate a reverse current; and a connection circuit 150, which has a third end 1501 and a fourth end 1502, wherein the third end 1501 is electrically connected to the coupling inductor 130, and the fourth end 1502 is electrically connected to the power module When the connection circuit 150 is in normal operation, the short-circuit switch 120 is turned on and generates a holding current to keep the short-circuit switch 120 on. When the connection circuit 110 is short-circuited, the buffer circuit 140 generates the Reverse current; wherein, when the DC microgrid is disconnected, the buffer circuit 140 generates the reverse current to convert the maintaining current into a negative current, and the short-circuit switch 120 is automatically disconnected when measuring the negative current, The DC microgrid is open circuit.

The bidirectional solid-state circuit breaker in the present invention enables the short-circuit switch to maintain current conduction when the circuit is normally turned on, so that the DC microgrid forms a path.

When the device in the connecting circuit is abnormal, the short-circuit current of the circuit changes. In a certain period of time set by the system, for example, when the short-circuit time is 100 microseconds, the commutation capacitor in the snubber circuit starts to discharge, and such a current will cause the short-circuit switch The negative current value is measured instantaneously, so that the short-circuit switch is automatically disconnected, thereby achieving the function of short-circuit protection.

If the current is only unstable for a short time and the short-circuit time set by the system is not exceeded, the commutation capacitor in the snubber circuit will not discharge.

If the current is unstable and the load current measured by the short-circuit switch increases, it will not cause the current measured by the short-circuit switch to reach a negative value, but maintain the current conduction, so that the DC microgrid forms a path.

Among them, when the integrated coupled inductor naturally suppresses the short-circuit current, it also includes Low-pass and band-stop filter functions are incorporated to reduce the ripple current problem generated by power electronic converters on the DC grid.

The reliability and service life of the bidirectional solid-state circuit breaker are enhanced by integrating the coupled inductor to naturally suppress the short-circuit current, and at the same time utilizing the natural cut-off characteristics of the silicon-controlled rectifier element.

Fig. 3 is a schematic diagram of current variation of a bidirectional solid-state circuit breaker applied to a DC microgrid according to the present invention. In the solid-state circuit breaker in the invention of the present application, the current changes when the circuit is short-circuited. Assume that when the short-circuit time is 100 microseconds, the commutation capacitor of the snubber circuit will start to discharge and generate a reverse current to measure the reverse current value A. Therefore, the short-circuit switch will instantly measure a negative current value, making the current in the DC microgrid The value B drops momentarily to a negative value. When the current is negative, the short-circuit switch will be automatically disconnected, thereby achieving the function of short-circuit protection. On the contrary, if only the load current increases, the current of the short circuit switch will not reach a negative value and remain on.

In this embodiment, when the power module in the DC microgrid is continuously discharging, when the short-circuit switch receives a positive voltage, the short-circuit switch is turned into an SCR ON state through a gate trigger signal of the short-circuit switch.

When the SCR is ON and the connected circuit is in normal operation, the short-circuit switch is turned on and generates a holding current to keep the short-circuit switch on.

In addition, when the connecting circuit is short-circuited, the reverse capacitance in the snubber circuit discharges at a short-circuit time of 100 microseconds, generating a reverse current, and the impact of the surge on the DC microgrid is reduced through the snubber circuit. , the short-circuit switch measures a negative current, so that the short-circuit switch is automatically disconnected to achieve short-circuit protection.

To sum up, the present invention utilizes silicon-controlled rectifier elements for short-circuit fault protection, which can improve the problems of poor life and slow speed of DC circuit breakers, and increase the function of power filters. When the integrated coupling inductor naturally suppresses short-circuit current, Low-pass and band-stop filter functions can also be added to reduce the ripple current problem caused by power electronic converters on the DC grid, and can also reduce circuit costs, without additional detection circuits, simple control and cost reduction, and effective control development cost, and because the circuit is reliable High precision, through the integration of coupled inductors to naturally suppress the short-circuit current, and at the same time, the reliability and service life of the present invention are enhanced by utilizing the natural cut-off characteristics of the silicon-controlled rectifier element.

Although the present invention is disclosed as above with the foregoing embodiments, it is not intended to limit the present invention. Anyone who is familiar with the similar art, without departing from the spirit and scope of the present invention, the equivalent replacement of changes and modifications is still the scope of the present invention. within the scope of patent protection.

110: Power module

1101: Positive output terminal

1102: Negative output terminal

120: Short circuit switch

121: Control terminal

122: first end

123: second end

130: coupled inductance

131: First winding

1311: fifth terminal

1312: sixth end

132: Second winding

1321: seventh end

1322: eighth end

140: buffer circuit

141: commutation capacitor

142: resistance

143: Diode

150: Connect the circuit

1501: the third end

1502: the fourth terminal

210: reverse current

Claims (8)

A bidirectional solid-state circuit breaker applied to a DC microgrid, comprising: a power module for outputting a DC voltage of stable DC power; a short-circuit switch including a control terminal, wherein the control terminal is electrically connected to the power module, When a short circuit occurs in a DC micro-grid, a reverse current is obtained to turn the short-circuit switch and form a circuit break; a coupling inductor is electrically connected to the short-circuit switch, including two windings, electrically connected to the short-circuit switch, and The two windings form reverse coupling, the coupled inductor further includes a first winding and a second winding, the first winding has a fifth end and a sixth end, the second winding has a seventh end and a The eighth end; a snubber circuit, electrically connected to the coupling inductor, used to suppress a surge circuit, including a commutation capacitor, used to generate a reverse current, one end of the snubber circuit connected to the sixth end and the first Eight terminals; and a connecting circuit having a third terminal and a fourth terminal, wherein the third terminal is electrically connected to the coupling inductor, and the fourth terminal is electrically connected to a negative output terminal of the power module, when the When the connection circuit is in normal operation, the short-circuit switch is turned on and generates a holding current to keep the short-circuit switch in a conduction state. When the connection circuit is short-circuited, the buffer circuit generates the reverse current. A bidirectional solid-state circuit breaker applied to a DC microgrid as described in item 1 of the scope of patent application, wherein the short-circuit switch is a silicon-controlled rectifier, and further includes the control terminal, a first terminal, and a second terminal. A bidirectional solid-state circuit breaker applied to a DC microgrid as described in item 2 of the scope of the patent application, wherein the control terminal of the short-circuit switch is a gate of the silicon-controlled rectifier, and the first terminal is a gate of the silicon-controlled rectifier a positive pole, and the second terminal is a negative pole of the silicon controlled rectifier. A bidirectional solid-state circuit breaker applied to a DC microgrid as described in item 1 of the scope of the patent application, wherein the snubber circuit is an RCD clamping circuit. A bidirectional solid-state circuit breaker applied to a DC microgrid as described in item 4 of the scope of patent application, wherein the RCD clamping circuit includes the commutation capacitor, a resistor, and and a diode. A bidirectional solid-state circuit breaker applied to a DC microgrid as described in item 1 of the scope of the patent application, wherein one end of the snubber circuit is electrically connected to the coupling inductor, and the other end is electrically connected to the power module. A bidirectional solid-state circuit breaker applied to a DC micro-grid as described in item 1 of the scope of the patent application, wherein when the DC micro-grid is on, the short-circuit switch measures the holding current to keep the DC micro-grid on. A bidirectional solid-state circuit breaker applied to a DC microgrid as described in item 1 of the scope of the patent application, wherein when the DC microgrid is disconnected, the buffer circuit generates the reverse current to convert the maintaining current into a negative current , when the short-circuit switch measures the negative current, it is automatically disconnected, and the DC microgrid is disconnected.

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