A composite switching circuit and its control method

Abstract

This invention discloses a composite switching circuit and its control method, comprising a first relay J1, a diode D1, a unidirectional thyristor S1, and a second relay J2. The first relay J1 and diode D1 are connected in series. The series circuit of the first relay J1 and diode D1 is connected in reverse parallel with the unidirectional thyristor S1. The series circuit of the first relay J1 and diode D1 is also connected in parallel with the second relay J2 to form a control circuit. The two ends of the control circuit are respectively connected to the contacts of the two ends of the switch. This invention eliminates the need to detect zero-crossing points during the closing and opening of the switching circuit, and also eliminates the need to control the switch action at zero-crossing points. Control is only required to complete the zero-crossing closing and opening of the composite switching circuit within the corresponding time period. This solves the problem of capacitor bank damage caused by inaccurate zero-crossing detection in existing technologies, and improves the reliability of zero-crossing switching of the composite switch.

Description

Technical Field

[0001] This invention relates to a switching circuit and its control method, particularly a composite switching circuit and its control method, belonging to the field of electrical switches. Background Technology

[0002] The composite switch connects a high-voltage, high-current thyristor in parallel with the contacts of a magnetically latched relay. Controlled by a microcomputer, it automatically finds the optimal switching points, achieving zero-crossing switching (voltage switching on and zero-crossing switching off). The switching is instantaneously completed by the thyristor, while the current flow is initiated by the magnetically latched relay via a pulse voltage trigger that closes the contacts. However, existing composite switch circuits suffer from inaccurate zero-crossing detection under harmonic conditions, resulting in large inrush currents and potential damage to capacitor banks. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a composite switching circuit and its control method to improve the reliability of zero-crossing switching of the composite switch.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A composite switching circuit is characterized in that it includes a first relay J1, a diode D1, a unidirectional thyristor S1, and a second relay J2. The first relay J1 is connected in series with the diode D1. The series circuit of the first relay J1 and the diode D1 is connected in reverse parallel with the unidirectional thyristor S1. The series circuit of the first relay J1 and the diode D1 is connected in parallel with the second relay J2 to form a control circuit. The two ends of the control circuit are respectively connected to the contacts at both ends of the switch.

[0006] Furthermore, it also includes a microprocessor circuit M, a first control circuit K1, a second control circuit K2, and a third control circuit K3. The first control circuit K1 is connected to the control terminal of the first relay J1, the second control circuit K2 is connected to the control terminal of the second relay J2, and the third control circuit is connected to the control terminal of the unidirectional thyristor S1. The first control circuit K1, the second control circuit K2, and the third control circuit K3 are respectively connected to the microprocessor circuit M.

[0007] Furthermore, it also includes a voltage detection circuit V, the two ends of which are respectively connected to the contacts at both ends of the switch to collect the voltage signal between the contacts at both ends of the switch.

[0008] Furthermore, it also includes a current detection circuit A, which is connected in series with the control circuit between the contacts at both ends of the switch to collect the current signal of the switching circuit.

[0009] Furthermore, a power supply circuit P is provided within the microprocessor circuit M.

[0010] Furthermore, the series circuit of the first relay J1 and diode D1 is replaced by a unidirectional thyristor that is aligned with diode D1.

[0011] Furthermore, the unidirectional thyristor S1 is replaced by a series circuit of a diode and a relay arranged in the same direction as the unidirectional thyristor S1.

[0012] A control method for a composite switching circuit, characterized by comprising the following steps:

[0013] When the microprocessor circuit M receives the closing command from the signal input circuit, it judges the detection signal of the voltage detection circuit V, and sends a control signal during the time period t1 when the voltage is opposite to that of diode D1. The first control circuit K1 controls the first relay J1 to close. During the time period t2 when the voltage is opposite to that of unidirectional thyristor S1, the third control circuit K3 provides a control signal to the control electrode of unidirectional thyristor S1. During the time period t3 or later, the second control circuit K2 controls the second relay J2 to close, and the switching circuit completes the closing.

[0014] When the microprocessor circuit M receives the tripping command from the signal input circuit, it controls the second relay J2 to disconnect through the second control circuit K2. Then, it judges the detection signal of the current detection circuit A. During the time period t4 when the current is opposite to that of the diode D1, it controls the first relay J1 to disconnect through the first control circuit K1. During the time period t4 or later, it controls the control signal of the control electrode of the unidirectional thyristor S1 to be turned off through the third control circuit K3. The switching circuit completes the tripping.

[0015] Furthermore, the voltage detection circuit V detects the voltage signals at the contacts U1 and U2 at both ends of the switch circuit, and simultaneously provides input power to the power supply circuit P. When the switch is open, the voltage signal between U1 and U2 is a sine wave, which is transmitted to the microprocessor circuit M.

[0016] Furthermore, the current detection circuit A detects the current signal of the switching circuit. When the switch is closed and the capacitor is engaged, the current signal waveform is a sine wave, which is transmitted to the microprocessor circuit M.

[0017] Compared with the prior art, the present invention has the following advantages and effects: The present invention provides a novel composite switch circuit and control method. Through reasonable structural design, the zero-crossing point does not need to be detected during the closing and opening of the switch circuit, nor is it necessary to control the switch action at the zero-crossing point. The zero-crossing closing and opening of the composite switch circuit can be completed by completing the control within the corresponding time period. This solves the problem of capacitor bank damage caused by inaccurate zero-crossing detection in the prior art and improves the reliability of zero-crossing switching of the composite switch. In addition, the circuit structure of the present invention is simple, the number of components is small, the control process is simple, and the control time is short. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a composite switching circuit according to the present invention.

[0019] Figure 2 This is a diagram showing the closing time period of a control method for a composite switching circuit according to the present invention.

[0020] Figure 3 This is a diagram showing the opening time period of a control method for a composite switching circuit according to the present invention. Detailed Implementation

[0021] To illustrate in detail the technical solutions adopted by the present invention to achieve the intended technical objectives, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Furthermore, the technical means or technical features in the embodiments of the present invention can be replaced without creative effort. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0022] like Figure 1 As shown, a composite switching circuit of the present invention includes a first relay J1, a diode D1, a unidirectional thyristor S1, and a second relay J2. The first relay J1 and the diode D1 are connected in series. The series circuit of the first relay J1 and the diode D1 is connected in reverse parallel with the unidirectional thyristor S1. The series circuit of the first relay J1 and the diode D1 is also connected in parallel with the second relay J2 to form a control circuit. The two ends of the control circuit are respectively connected to the contacts of the two ends of the switch. The conduction direction of the diode D1 is opposite to the conduction direction of the unidirectional thyristor S1.

[0023] The composite switching circuit of the present invention further includes a microprocessor circuit M, a first control circuit K1, a second control circuit K2, and a third control circuit K3. The first control circuit K1 is connected to the control terminal of a first relay J1, the second control circuit K2 is connected to the control terminal of a second relay J2, and the third control circuit is connected to the control terminal of a unidirectional thyristor S1. Specifically, the control circuit K3 is connected to the control electrode G and the cathode K of the unidirectional thyristor S1. The first control circuit K1, the second control circuit K2, and the third control circuit K3 are each connected to the microprocessor circuit M. A power supply circuit P is provided within the microprocessor circuit M.

[0024] The composite switching circuit of the present invention further includes a voltage detection circuit V and a current detection circuit A. The two ends of the voltage detection circuit V are respectively connected to the two contacts of the switch to collect the voltage signal between the two contacts. The current detection circuit A is connected in series with the control circuit between the two contacts of the switch to collect the current signal of the switching circuit.

[0025] In this invention, the series circuit of the first relay J1 and the diode D1 and the unidirectional thyristor S1 both serve to achieve controllable unidirectional conduction, so the two can be substituted for each other.

[0026] A control method for a composite switching circuit includes the following steps:

[0027] The voltage detection circuit V detects the voltage signals at contacts U1 and U2 across the switch circuit, and simultaneously provides input power to the power supply circuit P. When the switch is open, the voltage signal between U1 and U2 is a sine wave, which is transmitted to the microprocessor circuit M. The current detection circuit A detects the current signal from the switch circuit. When the switch is closed and the capacitor is engaged, the current signal waveform is a sine wave, which is also transmitted to the microprocessor circuit M.

[0028] When the microprocessor circuit M receives the closing command from the signal input circuit, it determines the detection signal of the voltage detection circuit V as follows: Figure 2 As shown, a control signal is issued during time period t1, controlling the first relay J1 to close via the first control circuit K1. At this moment, the conduction direction of diode D1 is opposite to the voltage direction across U1 and U2, and the diode D1 circuit is not conducting. Therefore, the relay J1 closing will not generate a surge. During time period t2, a control signal is provided to the control electrode of the unidirectional thyristor S1 via the third control circuit K3. At this moment, the voltage direction across U1 and U2 is the same as that of diode D1, and the diode D1 circuit is conducting. However, the voltage direction is opposite to that of the unidirectional thyristor S1, so the unidirectional thyristor S1 is not conducting. This controls the unidirectional thyristor S1 to enter the conducting state. Since no current flows through it, no surge will occur. During time period t3 or later, the second relay J2 is controlled to close via the second control circuit K2, completing the closing of the switching circuit. At this time, since the unidirectional thyristor S1 is conducting and sharing the current, switching relay J2 will not generate a large surge. The entire closing process does not require detection of the zero-crossing point, nor does it require control of the switch action at the zero-crossing point. It only needs to complete the control within the corresponding time period to achieve zero-voltage closing at both ends of the switching circuit.

[0029] When the microprocessor circuit M receives the tripping command from the signal input circuit, it first controls the second relay J2 to disconnect via the second control circuit K2. At this time, the bidirectional conduction circuit composed of diode D1 and unidirectional thyristor S1 still conducts voltage and current in both directions. Then, it judges the detection signal of the current detection circuit A. Figure 3As shown, during time period t4, the first relay J1 is disconnected by the first control circuit K1. At this moment, diode D1 is in the opposite direction to the voltage and has no current. Disconnecting relay J1 does not generate a surge. During time period t4 or later, the control signal of the control electrode of unidirectional thyristor S1 is turned off by the third control circuit K3. When the third control circuit K3 cuts off the control signal of unidirectional thyristor S1, due to the characteristics of unidirectional thyristor S1, even without a control signal, as long as there is still current, unidirectional thyristor S1 will continue to conduct. As the current gradually decreases to 0 at time t4, unidirectional thyristor S1 has no current and thus achieves true turn-off. That is, unidirectional thyristor S1 can automatically find the current zero-crossing point for switching, and the switching circuit completes the disconnection. The entire disconnection process does not require detection of the zero-crossing point, nor does it require control of the switch action at the zero-crossing point. It only needs to complete the control in the corresponding time period to achieve the switching circuit current zero-crossing disconnection.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A control method of a composite switch circuit, the composite switch circuit comprising a first relay J1, a diode D1, a unidirectional thyristor S1 and a second relay J2, the first relay J1 being connected in series with the diode D1, the series circuit of the first relay J1 and the diode D1 being connected in anti-parallel with the unidirectional thyristor S1 and the series circuit of the first relay J1 and the diode D1 being connected in parallel with the second relay J2 to form a control circuit, the control circuit being connected between two contacts of a switch; further comprising a microprocessor circuit M, a first control circuit K1, a second control circuit K2 and a third control circuit K3, the first control circuit K1 being connected to a control terminal of the first relay J1, the second control circuit K2 being connected to a control terminal of the second relay J2, the third control circuit being connected to a control terminal of the unidirectional thyristor S1, the first control circuit K1, the second control circuit K2 and the third control circuit K3 being connected to the microprocessor circuit M respectively; further comprising a voltage detection circuit V, the voltage detection circuit V being connected to the two contacts of the switch for collecting a voltage signal between the two contacts of the switch; further comprising a current detection circuit A, the current detection circuit A being connected in series with the control circuit between the two contacts of the switch for collecting a current signal of the switch circuit; characterized in that comprising the following steps: when the microprocessor circuit M receives a closing command from a signal input circuit, the microprocessor circuit M judges a detection signal of the voltage detection circuit V, sends a control signal in a t1 time period when the voltage is opposite to the diode D1, controls the first relay J1 to close through the first control circuit K1, sends a control signal to the control terminal of the unidirectional thyristor S1 in a t2 time period when the voltage is opposite to the unidirectional thyristor S1 through the third control circuit K3, controls the second relay J2 to close in a t3 or later time period through the second control circuit K2, and the switch circuit is closed; when the microprocessor circuit M receives an opening command from the signal input circuit, the microprocessor circuit M controls the second relay J2 to open through the second control circuit K2, then judges a detection signal of the current detection circuit A, controls the first relay J1 to open in a t4 time period when the current is opposite to the diode D1 through the first control circuit K1, and controls the control terminal of the unidirectional thyristor S1 to be in an off state in a t4 or later time period through the third control circuit K3, and the switch circuit is opened.

2. The control method of a composite switching circuit according to claim 1, characterized by: The voltage detection circuit V detects a voltage signal of the two contacts U1, U2 of the switch circuit, and simultaneously provides an input power supply for a power supply circuit P, the voltage signal between U1 and U2 is a sine wave when the switch is opened, and is transmitted to the microprocessor circuit M.

3. The control method of a composite switching circuit according to claim 1, characterized by: The current detection circuit A detects a current signal of the switch circuit, the current signal waveform is a sine wave when a capacitor is put into the switch, and is transmitted to the microprocessor circuit M.

4. The control method of a composite switching circuit according to claim 1, characterized by: The microprocessor circuit M is provided with a power supply circuit P.

5. The control method of a composite switching circuit according to claim 1, characterized by: The series circuit of the first relay J1 and the diode D1 is replaced by a unidirectional thyristor arranged in the same direction as the diode D1.

6. The control method of a composite switching circuit according to claim 1, characterized by: The unidirectional thyristor S1 is replaced by a series circuit of a diode and a relay arranged in the same direction as the unidirectional thyristor S1.

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