Dual-power switch with voltage sag protection

Abstract

The invention discloses a dual-power switch with voltage sag protection, the dual-power switch has the voltage sag protection function and the dual-power switching function, a voltage sag protection circuit is composed of an LC parallel circuit, the circuit is characterized in that the voltage change of a load does not need to be detected, and once the voltage sag occurs, the voltage sag protection circuit can be switched off. The LC parallel circuit can immediately provide AC voltage support for the load. The dual-power switch with the voltage sag protection function is not a simple combination of a voltage sag protection circuit and a dual-power change-over switch, the functions of the voltage sag protection circuit and the dual-power change-over switch are organically combined, and the voltage sag protection circuit can be prevented from being short-circuited by controlling the switch to be switched off; and the voltage sag protection circuit can assist the dual-power switch to complete power supply switching under the condition that the load is uninterruptible, so that uninterruptible power supply switching is truly realized. In addition, in a normal power supply state, the dual-power switch can continuously and smoothly realize dual-power switching, so that more fields are developed for the application of the dual-power switch.

Description

Technical Field

[0001] The present invention relates to the field of dual power conversion, and in particular to a dual power switch with voltage sag protection. Background Art

[0002] Voltage sags are a common power quality issue in power supply systems, damaging sensitive loads, impacting normal equipment operation, and even causing equipment failure. An automatic transfer switch (ATS) is a device used to automatically or manually switch between two power sources (such as a primary power source and a backup power source). It is widely used in hospitals, airports, data centers, financial institutions, industrial production lines, and other environments where power supply stability is paramount, ensuring that life support equipment, data storage, and production processes are not affected by power outages. Its core function is to ensure the continuity and reliability of load power supply. However, existing dual-power switches cannot switch between the two power sources without interruption even under normal power conditions, let alone ensure uninterrupted switching in the event of a sudden loss of the primary power source. Power supply system failures are often caused by voltage sags, hence the development of the dynamic voltage restorer (DVR), a power quality management device based on power electronics technology, primarily used to address voltage sags and other issues in power grids. While ensuring voltage stability for sensitive loads, DVR response speed is limited. Because detection and execution take time, and execution speed is dependent on the inverter frequency, the typical DVR response speed is currently 3-5ms, with the fastest response speed being around 1ms. Chinese patent applications 202210770934.8 and 202420399764.1 disclose a combined DVR and ATS that can shorten the ATS's power outage time during power conversion, but cannot achieve completely uninterrupted power conversion.

[0003] The essence of DVR is an inverter based on power electronics technology. Power electronics technology has only been widely used in power grids for more than ten years. Although its reliability has been continuously improving since its initial application, it is still far from the reliability requirements of other equipment in the power system. Therefore, using a technology that has not been proven to have long-term reliability to guarantee the power supply system with extremely high reliability requirements is obviously not tenable in theory.

[0004] SUMMARY OF THE INVENTION

[0005] In order to solve the problems that existing dual power switches (ATS) cannot switch power supplies without power outages and that dynamic voltage restorers (DVRs) have slow response speed and low reliability to sudden voltage sags, the present invention provides a dual power switch with a voltage sag protection circuit, which has the functions of voltage sag protection and dual power conversion. When a sudden voltage sag occurs, the dual power switch with a voltage sag protection circuit of the present invention will quickly respond to provide AC voltage support to the load, ensuring that the load voltage has only minor changes. When the power supply voltage changes significantly or even a power outage may occur, it can ensure that power switching can be performed without powering off the load, thereby ensuring the normal operation of the electrical equipment.

[0006] To achieve the above-mentioned purpose, the technical solution of the present invention is as follows: The dual power switch with voltage sag protection of the present invention is composed of a voltage sag protection circuit, a main power switch circuit and a backup power switch circuit, wherein the voltage sag protection circuit is a parallel circuit of a capacitor C and an inductor L, with both ends connected in parallel to the load Z; the main power switch circuit is composed of a main power switch K A and K NA Composition, K A One end is connected to the main power phase line L A , the other end is connected to the load Z, K NA One end is connected to the main power neutral line N A , the other end is connected to the load Z, T A1 +D A1 The series branch and T A2 +D A2 The series branch and K A In parallel; the backup power switch circuit consists of the backup power switch K B and K NB Composition, K B One end is connected to the backup power phase line L B , the other end is connected to the load Z, K NB One end is connected to the standby power supply neutral line N B , the other end is connected to the load Z, K B1 +D B1 The series branch and K B2 +D B2 The series branch and K B In parallel, all switches are relay switches, and the action control of relay contact closing or opening is completed by a dedicated control circuit.

[0007] Furthermore, the voltage sag protection circuit is a controllable inverter power supply, with both ends connected to the load Z.

[0008] Furthermore, the main power switch K A Use a magnetic latching relay or a normally closed contact of a relay.

[0009] The beneficial effects of the present invention are as follows:

[0010] The dual power switch with voltage sag protection of the present invention can quickly detect voltage sags and respond quickly to different levels of voltage sags, effectively preventing damage to the load caused by voltage sags. By rationally designing the combination of switching elements and diodes, power switching without interruption of load power supply is truly achieved, improving the stability and reliability of load operation. The dual power switch with voltage sag protection of the present invention has a simple circuit structure, high reliability, is easy to implement and maintain, and is low in cost and suitable for a variety of power supply scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is one of the schematic diagrams of the dual power switch circuit with voltage sag protection of the present invention;

[0012] Figure 2 This is the second schematic diagram of the dual power switch circuit with voltage sag protection of the present invention;

[0013] Figure 3 This is one of the current waveforms of the LC parallel circuit in the voltage sag simulation experiment;

[0014] Figure 4 This is the second current waveform diagram of the LC parallel circuit in the voltage sag simulation experiment;

[0015] Figure 5 This is the third current waveform diagram of the LC parallel circuit in the voltage sag simulation experiment;

[0016] Figure 6 This is a current waveform diagram of the backup power supply switching process of the dual power switch with voltage sag protection of the present invention;

[0017] Figure 7 This is an application example of the dual power switch with voltage sag protection of the present invention in a three-phase power supply.

[0018] Specific embodiment description

[0019] like Figure 1 As shown, the dual power switch with voltage sag protection of the present invention is composed of a voltage sag protection circuit, a main power switch circuit and a backup power switch circuit. The voltage sag protection circuit is a parallel circuit of a capacitor C and an inductor L, with both ends connected in parallel to the load Z; the main power switch circuit is composed of a main power switch K A and K NA Composition, K A One end is connected to the main power phase line L A , the other end is connected to the load Z, K NA One end is connected to the main power neutral line N A , the other end is connected to the load Z, T A1 +DA1 The series branch and T A2 +D A2 The series branch and K A In parallel; the backup power switch circuit consists of the backup power switch K B and K NB Composition, K B One end is connected to the backup power phase line L B , the other end is connected to the load Z, K NB One end is connected to the standby power supply neutral line N B , the other end is connected to the load Z, K B1 +D B1 The series branch and K B2 +D B2 The series branch and K B in parallel, Figure 1 All switches are relay switches, T A1 and T A2 It is an IGBT transistor. The control of the closing or opening of the relay contacts and the control of the IGBT are completed by a dedicated control circuit. It is easy for professional technicians to design and complete it. Figure 1 Not marked in.

[0020] Under normal power supply conditions, the main power switch K A and K NA In the closed state, the main power supply is through K A and K NA Supply power to load Z, switch K of all backup power switch circuits B , K NB , K B1 and K B2 In the disconnected state. When the main power supply experiences a sudden voltage sag, the LC parallel circuit connected in parallel with load Z can readily provide AC voltage support to the load. For example, if the power supply voltage suddenly drops by 25%, the voltage on the load will only change by no more than 5%. The principle is that the inductor L and capacitor C form a resonant circuit close to 50Hz. When the voltage across the terminals suddenly changes, the LC parallel circuit can provide a compensation voltage close to 50Hz. This compensation voltage is the circuit response of the LC parallel circuit to the sudden voltage change. Unlike a DVR (voltage sag restorer), which needs to detect changes in grid voltage and then control the inverter to output the corresponding compensation voltage, the fastest response of a DVR takes several milliseconds, while the LC parallel circuit responds almost instantly. Therefore, the LC parallel circuit has a faster and more reliable response to voltage sags than a DVR. Figure 3 The figure shows the simulated grid voltage experiencing a 50% voltage sag lasting 1ms during the voltage rise phase, with and without an LC shunt circuit connected in parallel with the load to provide AC voltage support. It can be seen that with the LC shunt circuit supporting the load, there is almost no voltage change. Figure 4 The figure shows the simulated grid voltage experiencing a 50% voltage sag near its peak voltage for 1ms, with and without an LC parallel circuit connected in parallel with the load to provide AC voltage support. It can be seen that with the LC parallel circuit supporting the load, the maximum voltage change is only 15%, and the average voltage change is only about 5%. Figure 5 The display shows the performance of a simulated grid voltage drop phase with a 50% voltage sag lasting 1ms, with and without an LC shunt circuit connected in parallel with the load to provide AC voltage support. It can be seen that with the LC shunt circuit supporting the load, the maximum voltage change is only 15%, and the average voltage change is only about 7%.

[0021] The voltage support capacity provided by the LC parallel circuit is limited. When the voltage sag amplitude and duration exceed a certain value, the dual power switch with voltage sag protection of the present invention will enter the backup power supply switching mode. The process is as follows: Assuming that the voltage sag occurs in the positive half cycle of the AC, the maximum voltage sag amplitude exceeds 20% and the duration exceeds 2ms. This is likely caused by a short circuit or disconnection of the main power supply. The switch enters the backup power supply switching mode and first gives T A1 The G pole of the K is increased to a high level to enter the conduction standby state. A Closed T A1 The voltage across the terminals is zero, even if T A1 The G pole will not conduct even if it has a high level. At the same time, it controls the main power switch K A Disconnect, K A Disconnection moment T A1 It will be turned on immediately, and the main power supply will be turned on through D A1 +T A1 The series branch continues to supply power to load Z, so contact K A It will not arc and will not affect the continuous power supply of the main power supply to the load. A1 +T A1 The function of the series branch is to make K A It can be disconnected quickly and there is no possibility of reignition. A After disconnecting, immediately give T A1 Add a low level to the G pole to cut it off and disconnect K NA , T A1 After the cut-off, the power supply between the main power supply and the load has actually been cut off. After the main power supply and the load are disconnected, the LC parallel circuit enters the free discharge process of the load Z AC voltage support. When the LC parallel circuit supplies power to the load, the backup power supply is switched: close K B2 and K NB During the positive half cycle, the instantaneous value of the backup power supply is higher than the instantaneous value of the LC parallel circuit discharge voltage, D B2 Reverse conduction is not possible, and the backup power supply will not pass through K B2 +D B2The series branch supplies power to the load Z until about 1-2ms into the negative half cycle, when the instantaneous value of the backup power supply voltage is lower than the instantaneous value of the LC parallel circuit discharge voltage.

[0022] When the diode D B2 Turn on the backup power supply to start supplying power to the load. The backup power supply access point relies on diode D B2 Automatically find, then close K in the negative half cycle B , that is, the backup power supply switching process is completed, and there is no power outage during the entire switching process. The backup voltage switching process waveform is as follows Figure 6 As shown in the figure, point 1 to point 2 is the main power supply. A voltage sag occurs at about 2ms. At point 2, the main power supply is disconnected and the LC parallel circuit enters the discharge stage. From point 2 to point 3, the instantaneous value of the LC parallel circuit discharge voltage is lower than the instantaneous value of the backup power supply voltage (dashed line part). Until point 3, the instantaneous value of the backup power supply voltage is lower than the instantaneous value of the LC parallel circuit discharge voltage. The diode D B2 Turn on the backup power supply to start supplying power to the load.

[0023] When a voltage drop is detected, the main power switch K must be disconnected as soon as possible. A and K NA Only by disconnecting the power supply where the voltage sag occurs from the load can the voltage sag protection circuit operate normally. A The use of magnetic latching relays or normally closed contacts of relays can improve the response speed of switch disconnection. Using special control methods, the fastest action response can be achieved in less than 1 millisecond. That is, when a voltage sag is detected, an action command is sent to the relay, and the connection between the main power supply and the load can be disconnected within 1 millisecond.

[0024] The above is the process of switching the backup power supply during the negative half cycle. If the voltage sag occurs in the negative half cycle, the backup power supply switching process can be performed during the positive half cycle: A2 The G pole of the MOSFET is increased to a high level to make it enter the conduction standby state, while the K A , then remove T A2 The high level of G turns it off and disconnects K NA , closed K B1 and K NB , since the instantaneous value of the voltage across the load is higher than the instantaneous value of the backup power supply, D B1 No current flows in the reverse direction B1 +K B1 The series branch, that is, only the LC parallel circuit provides current to the load. When the zero point is 1-2ms, the instantaneous value of the voltage across the load is less than the instantaneous value of the backup power supply. B1 Forward conduction, backup power through D B1 +K B1 Series branch and K NBSupply power to the load and then close K B That is, the process of switching from the main power supply to the backup power supply is completed.

[0025] When the main power failure is eliminated, the process of switching from the backup power supply to the main power supply can be carried out from the positive half cycle to the negative half cycle of the voltage, or from the negative half cycle to the positive half cycle of the voltage. The following describes the power conversion process from the positive half cycle to the negative half cycle: When the backup power supply is supplied, K B and K NB Closed, closed in the positive half cycle K B1 and K NB1 , while giving T A2 The G pole of the MOSFET is high-leveled to make it enter the conduction standby state and close K NA , due to D A2 In reverse direction, no current flows through D A2 +T A2 Series branch and K NA The main power supply and the backup power supply do not interfere with each other, and K is disconnected during the positive half cycle. B , when the contact is disconnected, the current flows from D B1 +K B1 The series branch passes through to ensure the continuity of current, and the contact K B At the moment of disconnection, the voltage is only 0.7V, so the contacts will not arc and can be disconnected quickly; when the voltage changes from the positive half cycle to the negative half cycle, D B1 +K B1 No current flows through the series branch in the reverse direction, and D A2 +T A2 The branch is forward conducting, and the main power supply passes through D A2 +T A2 Series branch and K NA To supply power to the load, close K during the negative half cycle A And disconnect K NB , that is, the switching from the backup power supply to the main power supply is completed. During the entire power switching process, there is no power outage and no inrush current. The contacts of all switches do not spark or arc. The switching between the backup power supply and the main power supply at the zero point is very smooth.

[0026] In the normal power supply state, it is also possible to achieve uninterrupted power supply switching from the main power supply to the backup power supply. Those skilled in the art can implement the complete process of dual power supply switching based on the above description, and will not be repeated here.

[0027] Figure 2 The figure shows a circuit diagram of a dual power switch with voltage sag protection of the present invention using a controllable inverter as a voltage sag protection circuit. The controllable inverter replaces the Figure 1In the LC parallel circuit, the two ends of the controllable inverter power supply are connected in parallel to the two ends of the load Z. The load voltage detection module is connected in parallel to the two ends of the load to monitor the load voltage changes and control the output of the controllable inverter power supply. The controllable inverter power supply can be powered by a battery. Under normal power supply conditions, the controllable inverter power supply has no voltage output. If the load voltage detection module detects a voltage drop in the main power supply during the positive half cycle of the voltage, the controllable inverter power supply will be started to work. Before the controllable inverter power supply enters the working state, it is necessary to disconnect K A , K NA To prevent the main power failure from causing a short circuit to the controllable inverter power supply: First, give T A1 The G pole of the switch is turned high to make it enter the conduction standby state, and the K A , K is detected A After disconnecting, give T A1 Adding a low level to the G pole of the switch makes it enter the cut-off state, and disconnects K NA , T A1 After the cut-off, the connection between the main power supply and the load has actually been cut off. Then the load voltage detection module controls the controllable inverter power supply to enter the working state, and the controllable inverter power supply supplies power to the load Z, enters the negative half cycle of the voltage, and closes K B2 and K NB2 , adjust the output voltage of the controllable inverter power supply to be slightly higher than the standby power supply voltage, that is, the instantaneous value of the output voltage of the controllable inverter power supply is slightly lower than the instantaneous value of the standby power supply voltage. In the negative half cycle, the diode D B2 In reverse, the backup power supply will not cause short circuit interference with the controllable inverter power supply, ensuring K B2 and K NB After closing, the controllable inverter power supply output voltage is stopped, and the backup power supply immediately passes through D B2 +K B2 Series branch and K NB Supply power to load Z and close K B1 , and close contact K B , contact K B Once the closure is completed, the switching process to the backup power supply is completed, and the entire process is uninterrupted and without inrush current.

[0028] Figure 7 This is an embodiment of the dual power switch with voltage sag protection of the present invention applied to three-phase power supply occasions. In the figure, A1B1C1N1 is the main power supply, A2B2C2N2 is the backup power supply, and the voltage sag protection circuit can be a three-phase LC parallel circuit or a controllable three-phase inverter. Professional technicians can use the following methods according to the Figure 1 and Figure 2 As described in the embodiment, the action time of the corresponding relay switch contacts and the conduction time of the IGBT can be designed by the user to complete the compensation of the voltage sag and the switching between the two power supplies, which will not be described in detail here.

[0029] The dual power switch with voltage sag protection provided by the present invention has both voltage sag protection function and dual power switching function. A voltage sag protection circuit composed of an LC parallel circuit is disclosed. The characteristic of the circuit is that it does not need to detect the voltage sag of the power supply. Once a sudden voltage sag occurs, the circuit is switched off.

[0030] In the event of a voltage sag, the LC parallel circuit can immediately provide AC voltage support to the load, i.e., the LC parallel circuit can realize the function of DVR. Obviously, the reliability of capacitors and inductors is much higher than that of inverters. The dual power switch with voltage sag protection of the present invention is not a simple combination of a voltage sag protection circuit and a dual power conversion switch, but rather combines the functions of the two very well. When the switch is disconnected, it can prevent the voltage sag protection circuit from being short-circuited. During power switching, the voltage sag protection circuit can assist the dual power switch in completing the unit switching without interrupting the load power supply, thus truly realizing uninterrupted power supply switching. In addition, under normal power supply conditions, the dual power switch of the present invention can realize dual power switching continuously and smoothly, which will open up more areas for the application of the dual power switch.

[0031] The dual power switch with voltage sag protection of the present invention does not require precise control of the power switching point during the power conversion process, and can also achieve smooth switching between the two power supplies without power outage, which provides favorable conditions for the maintenance of the dual power switch.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. Dual power switch with voltage sag protection: It consists of a voltage sag protection circuit, a main power switch circuit, and a backup power switch circuit. The voltage sag protection circuit is a parallel circuit of a capacitor C and an inductor L, with both ends connected in parallel at both ends of the load Z; the main power switch circuit consists of the main power switch K A and K NA Composition, K A One end is connected to the main power phase line L A , the other end is connected to the load Z, K NA One end is connected to the main power neutral line N A , the other end is connected to the load Z, T A1 +D A1 The series branch and T A2 +D A2 The series branch and K A In parallel; the backup power switch circuit consists of the backup power switch K B and K NB Composition, K B One end is connected to the backup power phase line L B , the other end is connected to the load Z, K NB One end is connected to the standby power supply neutral line N B , the other end is connected to the load Z, K B1 +D B1 The series branch and K B2 +D B2 The series branch and K B in parallel.

2. The dual power switch with voltage sag protection according to claim 1, characterized in that: The voltage sag protection circuit is a controllable inverter power supply, with both ends connected to the load Z.

3. The dual power switch with voltage sag protection according to claims 1 and 2, characterized in that: The main power switch K A Use a magnetic latching relay or a normally closed contact of a relay.

Images