Power supply switching device

Abstract

To provide a power supply switching device.SOLUTION: A first power supply and a second power supply having three phase alternating current power, a first power switch group, a second power switch group, and a three phase transformer, wherein the three phase transformer comprises a first winding, a second winding, and a third winding arranged in a delta connection configuration to form a first common node, a second common node, and a third common node, the first common node is connected to the first switch and the fourth switch, and the second common node is connected to the second switch and the fifth switch; The third common node is connected to the third switch and the sixth switch.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply switching device, and more particularly to a power supply switching device that can provide a forced commutation process. [Background technology]

[0002] A static transfer switch (STS) is an essential component in the power system of a data center, supplying uninterruptible power to loads such as critical equipment. It typically contains multiple silicon-controlled rectifiers. Static transfer switches are typically powered by two or more independent power sources, with one set corresponding to one independent power source. If the preferred main power source exceeds its tolerance range, the STS automatically switches from the preferred main power source to the backup power source, providing uninterruptible power. This provides a continuous power supply to critical equipment, preventing the critical equipment from being forced to shut down due to an interruption in the power supply to the critical equipment.

[0003] Typically, the outputs of multiple sets of static switching devices are interconnected and connected to critical equipment via transformers. Because transformers are inductive devices, excessively high accumulated magnetic flux can lead to magnetic flux saturation. Therefore, if the primary power source exceeds its tolerance range and improper switching occurs between the two power sources, for example, the transformer voltage may become discontinuous, resulting in magnetic flux deviation and high inrush currents in downstream transformers. Excessive inrush currents can overload upstream circuits and trip breakers, resulting in a system-wide power outage and potential damage to the static switching devices. Therefore, to avoid excessive inrush currents, current switching methods wait an appropriate time after the current through the primary power source or silicon-controlled rectifier becomes zero before turning on the silicon-controlled rectifier in the backup power source. However, this switching method requires waiting for the current to become zero and then waiting an appropriate time before switching on, which can result in excessively low output voltages and potentially shutting down critical equipment. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, how to design a power supply switching device to solve the problems and technical bottlenecks of the prior art is an important issue that has been studied by the inventors of the present application.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a power supply switching device. [Means for solving the problem]

[0006] In order to achieve the above object, a power supply switching device according to the present invention is a power supply switching device including a first power supply and a second power supply having three-phase AC power, and further including a first power supply switch group including a first switch, a second switch, and a third switch electrically connected in sequence to a first phase, a second phase, and a third phase of the first power supply; a second power supply switch group including a fourth switch, a fifth switch, and a sixth switch electrically connected in sequence to the first phase, the second phase, and the third phase of the second power supply; and a three-phase transformer including a first winding, a second winding, and a third winding arranged in a delta connection configuration to form a first common node, a second common node, and a third common node, wherein the first common node is connected to the first switch and the fourth switch, and the second common node is connected to the second switch and the fifth switch. the third common node is connected to the third switch and the sixth switch, and the power supply switching device provides a forced commutation process for switching the first power supply to the second power supply, the forced commutation process including: turning off the first switch, the second switch, and the third switch connected to the first power supply; detecting magnetic fluxes of the first winding, the second winding, and the third winding, and selecting a winding with the fastest flux switching speed as a fastest flux switching winding; turning on two of the fourth switch, the fifth switch, and the sixth switch electrically connected to the fastest flux switching winding; and turning on any of the fourth switch, the fifth switch, and the sixth switch that is not turned on.

[0007] In order to achieve the above object, a power supply switching device according to the present invention is a power supply switching device including a first power supply and a second power supply having three-phase AC power, the power supply switching device including a first power supply switch group including a first switch, a second switch, and a third switch electrically connected in sequence to a first phase, a second phase, and a third phase of the first power supply, a second power supply switch group including a fourth switch, a fifth switch, and a sixth switch electrically connected in sequence to the first phase, the second phase, and the third phase of the second power supply, and a three-phase transformer including a first winding, a second winding, and a third winding arranged in a star-connected configuration to form a common node, a first node, a second node, and a third node, the common node being grounded, the first node being connected to the first switch and the fourth switch, and the second node being connected to the second switch and the third switch. a fourth switch connected to the fourth winding, a fifth switch connected to the sixth switch, and the third node connected to the third switch and the sixth switch, and the power supply switching device provides a forced commutation process for switching the first power supply to the second power supply, the forced commutation process including: turning off the first switch, the second switch, and the third switch connected to the first power supply; detecting magnetic fluxes of the first winding, the second winding, and the third winding, and selecting a winding with the fastest flux switching speed as a fastest flux switching winding; turning on one of the fourth switch, the fifth switch, and the sixth switch electrically connected to the fastest flux switching winding; and turning on two of the fourth switch, the fifth switch, and the sixth switch that are not turned on. [Effects of the Invention]

[0008] According to the present invention, by realizing the optimum timing for executing the forced switching of the thyristor, it is possible to effectively achieve switching between two power sources.

[0009] In order to better understand the techniques, means, and advantages of the present invention which are contemplated to achieve the objects of the present invention, the objects and features of the present invention will be better understood by referring to the detailed description of the invention and the accompanying drawings, which are provided for reference and explanation only and are not intended to limit the invention. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a circuit block diagram of a power supply switching device according to the present invention; [Figure 2] 3A and 3B are schematic waveform diagrams of a main power supply, a standby power supply, and an output power supply according to the present invention. [Figure 3] 1 is a schematic diagram showing forced commutation of a power supply switching device according to the present invention; [Figure 4] 2 is a flowchart of a forced commutation method for a power supply switching device according to the present invention. [Figure 5] 3A and 3B are waveform diagrams showing voltages and magnetic fluxes of forced commutation in the power supply switching device according to the present invention. [Figure 6] 1 is a circuit block diagram of a three-phase three-wire power supply switching device according to the present invention. [Figure 7] 1 is a circuit block diagram of a three-phase four-wire power supply switching device according to the present invention. [Figure 8] 2 is a flowchart of a forced commutation method for a three-phase three-wire power supply switching device according to the present invention; [Figure 9] 2 is a flowchart of a forced commutation method for a three-phase four-wire power supply transfer device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The technical contents and detailed description of the present invention will be described below with reference to the drawings.

[0012] 1 is a circuit block diagram of a power supply switching device according to the present invention. The power supply switching device 100 mainly supplies power to a load 121 (e.g., a critical facility) and includes static switch devices 130 and 131, an inductive device 120, and a controller 134. The static switch devices 130 and 131 include a first static switch 130 and a second static switch 131. The load 121 may be, for example, but is not limited to, a device that requires continuous, uninterrupted operation, such as a server or a communication system.

[0013] The input side of the first static switch 130 is connected to the first power source 110, the input side of the second static switch 131 is connected to the second power source 111, and the output side of the first static switch 130 and the output side of the second static switch 131 are connected to a common node. The inductive device 120 may be, for example, but is not limited to, a transformer including a primary winding 120A and a secondary winding 120B. The primary winding 120A is connected to the first static switch 130 and the second static switch 131 at a common node, and the secondary winding 120B is connected to the load 121.

[0014] The controller 134 is used to detect the power supply power of the first power source 110 and the second power source 111 and collect power supply information of the first power source 110 and the second power source 111 in real time. The controller 134 also detects the output power provided by the first static switch 130 or the second static switch 131 and received by the inductive device 120, thereby adjusting and controlling the first static switch 130 and the second static switch 131. Here, the controller 134 controls the first static switch 130 and the second static switch 131 to select the first power source 110 or the second power source 111 and supply power to the load 121 connected to the inductive device 120. In one embodiment, the controller 134 may be a digital signal processor (DSP), but is not limited thereto. A physical circuit capable of performing circuit control using a signal, a control device having built-in control software, and the like are also within the scope of this embodiment.

[0015] Specifically, the power supply switching device 100 further includes voltage sensors 122, 123, and 124 and current sensors 132 and 133. The voltage sensors 122, 123, and 124 include a first voltage sensor 122, a second voltage sensor 123, and a third voltage sensor 124. The first voltage sensor 122 and the second voltage sensor 123 are connected to the first power supply 110 and the second power supply 111, respectively, and detect a first voltage signal V1 and a second voltage signal V2 corresponding to the first power supply 110 and the second power supply 111, respectively. The current sensors 132 and 133 include a first current sensor 132 and a second current sensor 133, and are connected to the first power supply 110 and the second power supply 111, respectively, and detect a first current signal I1 and a second current signal I2 corresponding to the first power supply 110 and the second power supply 111, respectively, to obtain the power supply power of the first power supply 110 and the second power supply 111. Also, a third voltage sensor 124 is connected to the primary winding 120A (shown in FIG. 1 ) or the secondary winding 120B (not shown, but included in the scope of this embodiment) of the inductive device 120 to detect a third voltage signal Vo corresponding to the primary winding 120A or the secondary winding 120B. Thus, the voltage signals and current signals detected by the voltage sensors 122, 123, 124 and the current sensors 132, 133 are sent to the controller 134 for control by the controller 134.

[0016] FIG. 2 is a schematic waveform diagram of the main power supply, the standby power supply, and the output power supply according to the present invention. As shown in the figure, the voltage waveforms of the first power supply 110 and the second power supply 111 have a phase difference, but this is only a rough representation and are not correlated with each other. That is, the switching control method of the present invention mainly controls magnetic flux, regardless of the magnitude of the phase difference. The controller 134 acquires the first voltage signal V1, the second voltage signal V2, and the third voltage signal Vo, and integrates the first voltage signal V1, the second voltage signal V2, and the third voltage signal Vo to obtain magnetic fluxes f1 and f2 corresponding to the first power supply 110 and the second power supply 111, and a magnetic flux fo, which is the predicted magnetic flux on the inductive device 120. Here, the first magnetic flux f1 is the integral of the first voltage signal V1, the second magnetic flux f2 is the integral of the second voltage signal V2, and the third magnetic flux fo is the integral of the third voltage signal Vo. Note that the first magnetic flux f1 and the third magnetic flux fo are equal because the first static switch 130 is turned on to connect the first power supply 110 to the inductive device 120. Here, the integral of the voltage is the magnetic flux, and the integral of a sine wave remains a sine wave, so the first magnetic flux f1, the second magnetic flux f2, and the third magnetic flux (predicted magnetic flux) fo remain sinusoidal waveforms.

[0017] Referring again to FIG. 1, the first static switch 130 and the second static switch 131 each include a plurality of silicon controlled rectifiers (SCRs). The first static switch 130 includes a first thyristor 130a and a second thyristor 130b. The first thyristor 130a and the second thyristor 130b are active thyristors for positive and negative half-cycle operation, respectively, and are connected in anti-parallel to each other. For example, the anode of the first thyristor 130a is connected to the cathode of the second thyristor 130b, and the cathode of the first thyristor 130a is connected to the anode of the second thyristor 130b. The second static switch 131 includes a third thyristor 131a and a fourth thyristor 131b. The third thyristor 131a and the fourth thyristor 131b are active thyristors that operate in the positive and negative half cycles, respectively, and are connected in antiparallel to each other. For example, the anode of the third thyristor 131a is connected to the cathode of the fourth thyristor 131b, and the cathode of the third thyristor 131a is connected to the anode of the fourth thyristor 131b. Here, the thyristors 130a to 131b are preferably, but not limited to, silicon-controlled rectifiers.

[0018] The controller 134 also generates a plurality of independent control signals Sc1 to Sc4 for controlling the first to fourth thyristors 130a to 131b, respectively. Specifically, the first control signal Sc1 controls the gate of the first thyristor 130a, the second control signal Sc2 controls the gate of the second thyristor 130b, the third control signal Sc3 controls the gate of the third thyristor 131a, and the fourth control signal Sc4 controls the gate of the fourth thyristor 131b. The anodes / cathodes of the first thyristor 130a and the third thyristor 131a are arranged in the same direction, and the anodes / cathodes of the second thyristor 130b and the fourth thyristor 131b are arranged in the same direction. Therefore, the forward bias direction of the paths of the first thyristor 130a and the fourth thyristor 131b is the same, and the forward bias direction of the paths of the second thyristor 130b and the third thyristor 131a is the same.

[0019] Due to the characteristics of the thyristors 130a-131b, the controller 134 cannot turn off the thyristors 130a-131b by controlling the gates when current is flowing. Therefore, the thyristors 130a-131b can only be turned off after the current has naturally gone to zero or after canceling the anode current by forced commutation techniques.

[0020] Specifically, the controller 134 of the present invention selectively controls the first thyristor 130a, the second thyristor 130b, the third thyristor 131a, and the fourth thyristor 131b depending on whether the power supply source is the first power supply 110 or the second power supply 111. Here, the controller 134 can be used to continuously and instantaneously calculate the first magnetic flux f1, the second magnetic flux f2, and the third magnetic flux fo in the first power supply 110, the second power supply 111, and the inductive device 120 (e.g., an inductive component such as a transformer, but not limited to this), respectively. When a power supply failure occurs (e.g., an abnormality occurs in the first power supply 110, but not limited to this), the controller 134 supplies the first control signal Sc1 and the second control signal Sc2, respectively, to turn off the first thyristor 130a and the second thyristor 130b on the operating path of the first power supply 110.

[0021] Then, the controller 134 supplies the third control signal Sc3 and the fourth control signal Sc4 to turn on the third thyristor 131a and the fourth thyristor 131b on the standby path (i.e., the second power supply 111) based on the magnetic flux calculated from the currently detected first voltage signal V1, second voltage signal V2, and third voltage signal Vo, according to a specific operation method designed by the present invention. This prevents a high inrush current from being generated in the downstream inductive device 120 due to improper switching between the two power supplies, and also prevents a situation in which the output power supply drops and the stable operation of the load 121 cannot be maintained because the current in the silicon-controlled rectifier 121 has to be zero. Here, according to the specific operation method designed by the present invention, the third control signal Sc3 and the fourth control signal Sc4 are supplied to turn on the third thyristor 131a and the fourth thyristor 131b, respectively, i.e., only one of the third thyristor 131a and the fourth thyristor 131b is turned on during a specific switching period.

[0022] Meanwhile, the controller 134 detects the first current (i.e., the first current signal I1) flowing through the first static switch 130 using the first current sensor 132 to determine whether the first static switch 130 is on or off. That is, the controller 134 can determine whether the first static switch 130 is turned on or off correctly using the first current (i.e., the first current signal I1) to determine whether the entire power supply switching device 100 operates normally. Meanwhile, the controller 134 can easily determine whether the first thyristor 130a and the second thyristor 130b are turned on or off correctly by detecting the voltages (first voltage signal V1 and third voltage signal Vo) across the first thyristor 130a and the second thyristor 130b. Similarly, the controller 134 detects the second current (i.e., the second current signal I2) flowing through the second static switch 131 using the second current sensor 133 to determine whether the second static switch 131 is on or off. That is, the controller 134 can check whether the second static switch 131 is turned on / off correctly by the second current (i.e., the second current signal I2) and thereby check whether the entire power supply switching device 100 operates normally. Meanwhile, the controller 134 can easily determine whether the third thyristor 131a and the fourth thyristor 131b are turned on / off correctly by detecting the voltages (second voltage signal V2 and third voltage signal Vo) between both ends of the third thyristor 131a and the fourth thyristor 131b.

[0023] FIG. 3 is a schematic diagram illustrating forced commutation in a power supply switching device according to the present invention. As shown in FIG. 3, the controller 134 provides a forced commutation mechanism to prevent simultaneous supply of the two power supplies S-pri and S-alt or a short circuit between them. Unlike conventional natural commutation methods, the present invention provides a control method using forced commutation. FIG. 4 is a flowchart illustrating the forced commutation method in a power supply switching device according to the present invention. As shown in FIG. 3, enabling the forced commutation mechanism, i.e., the opportunity for forced commutation, can be likened to obtaining a ticket. When an abnormality occurs in the main power supply S-pri, the controller 134 first controls the gate to turn off all thyristors connected to the main power supply S-pri, i.e., thyristors T1P and T1N (step S101: shown as "Gate-off pri. SCR" in FIG. 4). As mentioned above, due to the characteristics of thyristors, it may not be possible to completely turn off the thyristors T1P and T1N, which are controlled to be off via the gate.

[0024] Next, the controller 134 determines whether the detected current ipri of the main power supply S-pri is greater than zero (step S102). If the current ipri is greater than zero, it means that there is a thyristor T1P that is not completely turned off. At this time, the thyristor T1P is in the on state. Next, the controller 134 determines whether the voltage V of the standby power supply S-alt is greater than zero. alt It is determined whether the voltage V is greater than the load voltage Vload (step S103). alt is greater than the load voltage Vload, the controller 134 alt turns on thyristor T2P so as to reverse-excite thyristor T1P, and turns off thyristor T1P (positive switch) that is still on with a reverse voltage, thereby permitting forced commutation of the positive switch that is on, i.e., acquiring a ticket (FC ticket-Pos) for forced commutation of the positive switch that is on (step S104).

[0025] On the other hand, if it is determined in step S102 that the current ipri of the main power supply S-pri is less than zero, this means that there is a thyristor T1N that is not completely turned off. At this time, the thyristor T1N is in the on state. Next, the controller 134 controls the voltage V of the standby power supply S-alt. alt It is determined whether the voltage V is smaller than the load voltage Vload (step S105). alt is smaller than the load voltage Vload, the controller 134 can forcibly turn off the thyristor T1N (negative switch) that is still on by turning on the thyristor T2N through the current change effect, thereby permitting the forced commutation of the negative switch that is on, that is, obtaining a ticket (FC ticket-Neg) for forced commutation of the negative switch that is on (step S106).

[0026] Note that when a forced commutation ticket for an ON positive switch is obtained (can be obtained once or multiple times), i.e., when the forced commutation of an ON positive switch is permitted, or when a forced commutation ticket for an ON negative switch is obtained (can be obtained once or multiple times), i.e., when the forced commutation of an ON negative switch is permitted, the effect of the forced commutation is not necessarily ideal at that time, so it is not necessary to perform the forced commutation immediately. This is because the introduction of forced commutation may cause excessive magnetic flux deviation. Preferably, the time to introduce the forced commutation is determined taking into account the magnetic flux switching speed, magnetic flux magnitude, etc. (as will be described later).

[0027] Furthermore, if forced commutation is not introduced in consideration of the switching speed of the magnetic flux, the magnitude of the magnetic flux, etc. (even if there are forced commutation conditions for the positive switch that is turned on and / or the negative switch that is turned on), the thyristor that was originally on will be turned off due to natural switching, as its current will naturally become zero. alt There is a voltage difference ΔV between the load voltage Vload and the pri Therefore, the controller 134 determines the voltage difference ΔV pri is the voltage threshold V thzIt is determined whether the voltage difference ΔV is greater than pri is the voltage threshold V thz If it is greater than 1 / (1 / 2), it means that the thyristors connected to the main power supply S-pri, i.e., both thyristors T1P and T1N, are turned off. As a result, a ticket (FC ticket-NoCare) to turn on the turned-off positive switch or the turned-off negative switch is acquired (step S108). In this case, even if either thyristor is turned on, a short circuit abnormality between the main power supply S-pri and the standby power supply S-alt does not occur.

[0028] The following describes how to determine the time to introduce forced commutation, i.e., the timing for determining the use of a ticket to perform forced commutation. Figure 5 is a waveform diagram showing the voltage and magnetic flux of forced commutation in a power supply switching device according to the present invention. As shown in the figure, since the load voltage is a sine wave (shown by the waveform at the top of Figure 5), the magnetic flux is also a sine wave.

[0029]

number

[0030] Since the magnetic flux is a constant sine wave, we can predict the excitation energy generated by this flux within the period of the sine wave, i.e., obtain the integral of the voltage (shown in the middle waveform of Figure 5).

[0031] That is, because the excitation energy due to the magnetic flux is predictable, by calculating the magnitude of the voltage excitation during the period when the thyristor is not turned on, it is possible to calculate back how much magnetic flux excitation energy will be obtained when the thyristor is turned on. In this way, the time to introduce forced commutation can be determined based on the magnitude of the current load voltage and the magnitude of the magnetic flux excitation energy that can be back-calculated. In other words, if the magnitude of the stored excitation energy does not exceed the saturation magnetic flux after the switch is turned on, forced commutation of the thyristor can be performed.

[0032] On the other hand, if there is a possibility that the magnitude of the stored excitation energy will exceed the saturation magnetic flux after the switch is turned on, the forced commutation of the thyristor may be temporarily suspended so as not to be executed, and the forced commutation of the thyristor may be executed until the magnitude of the stored excitation energy does not exceed the saturation magnetic flux.

[0033] Specifically, the polarity of the magnetic flux deviation and the polarity of the voltage are further taken into consideration. In one case, when the polarity of the magnetic flux deviation is the same as the polarity of the voltage, for example, when the magnetic flux is positive during a positive half cycle of the voltage, it is possible to select the timing for performing forced commutation of the thyristor. In other words, if the accumulated excitation energy is too large, it is possible to wait. On the other hand, if the accumulated excitation energy is not yet large, it is possible to perform forced commutation of the thyristor as long as magnetic flux saturation does not occur.

[0034] In another case, if the polarity of the magnetic flux deviation is different from the polarity of the voltage, for example, a power failure occurs during the negative half cycle, causing excitation during the negative half cycle. If demagnetization is performed during the positive half cycle, magnetic flux saturation is less likely to occur. In the case of demagnetization, it is preferable to be able to execute forced commutation of the thyristors early. Therefore, if the controller 134 determines that the polarity of the magnetic flux deviation is not the same as the polarity of the voltage and magnetic flux saturation will not occur, it can immediately execute forced commutation of the thyristors. The above content can be calculated using the following relationship:

[0035]

number

number

number

[0036] Here, the amount of magnetic flux deviation accumulated by the load can be calculated using Equation 2. The magnetic flux that can be obtained in the future can be calculated using Equation 3, and the maximum magnetic flux in the future is max and the minimum magnetic flux (shown by the waveform at the bottom of Figure 5) are calculated to determine whether or not they exceed the saturation magnetic flux. Equation 4 can be used to determine the polarity of the future magnetic flux and present magnetic flux. As mentioned above, if the polarities are the same, it is necessary to wait for the appropriate timing to execute forced commutation of the thyristor. Conversely, if the polarities are different, forced commutation of the thyristor can be executed under relatively lenient conditions.

[0037] How the above-mentioned magnetic flux, voltage, and thyristor forced commutation are applied to a three-phase power supply device, and more specific thyristor control will be described later. Figure 6 is a circuit block diagram of a three-phase three-wire power supply switching device according to the present invention. As shown in Figure 6, two power supplies including a main power supply S-pri and a standby power supply S-alt are connected to a downstream three-phase transformer 33 via respective three-phase static switch devices 31 and 32.

[0038] 6, the three-phase power supply switching device includes a first power supply S-pri and a second power supply S-alt, each having three-phase AC power. The power supply switching device includes a first power supply switch group 31 and a second power supply switch group 32. The first power supply switch group 31 includes a first switch 311, a second switch 312, and a third switch 313, which are electrically connected in sequence to the first phase (R phase), second phase (S phase), and third phase (T phase) of the first power supply S-pri. The second power supply switch group 32 includes a fourth switch 321, a fifth switch 322, and a sixth switch 323, which are electrically connected in sequence to the first phase (R phase), second phase (S phase), and third phase (T phase) of the second power supply S-alt.

[0039] The three-phase transformer 33 includes a first winding W12, a second winding W23, and a third winding W31. The first winding W12, the second winding W23, and the third winding W31 of the three-phase transformer 33 are arranged in a delta connection configuration (Δ connection) to form three common nodes N1, N2, and N3. The first common node N1 is connected to the first switch 311 and the fourth switch 321, the second common node N2 is connected to the second switch 312 and the fifth switch 322, and the third common node N3 is connected to the third switch 313 and the sixth switch 323.

[0040] By the way, there are common problems with three-phase, three-wire systems. One is the problem of over-excitation, and the other is the problem of ineffective excitation.

[0041] Regarding the problem of over-excitation, some windings of three-phase transformer 33 are supplied with power from main power supply S-pri, and some other windings are supplied with power from standby power supply S-alt, so it is possible that some windings may be supplied with power from both main power supply S-pri and standby power supply S-alt. In this case, if the phase difference between main power supply S-pri and standby power supply S-alt is floating, in the worst case scenario, a voltage twice the rated voltage may be applied to this winding, causing insulation breakdown in three-phase transformer 33 or generating an inrush current due to saturation of three-phase transformer 33.

[0042] Regarding the problem of ineffective excitation, when the timing of forced commutation is determined by calculating the magnetic flux as described above and then the forced commutation is executed, if only one thyristor is turned on, the current path cannot flow back, so the conduction of such thyristor becomes ineffective and has no effect on the excitation or demagnetization of the three-phase transformer 33.

[0043] Therefore, the present invention can effectively achieve switching between two power sources to avoid the above-mentioned problems of over-excitation and ineffective excitation. When an abnormality occurs in the main power source S-pri, all thyristors connected to the main power source S-pri are first turned off by controlling the gate. Then, permission for forced commutation (ticket) is obtained, and two thyristors of two phases are selected to be turned on simultaneously to avoid ineffective excitation. After that, a half-cycle is waited. If the current time is a positive half-cycle, for example, the remaining thyristors of two phases are turned on in the next negative half-cycle, completing the conduction of all four thyristors of two phases.

[0044] The timing to turn on the thyristor of the remaining phase is determined based on whether or not magnetic flux saturation occurs after the calculated future magnetic flux is applied. If magnetic flux saturation occurs, the timing to turn on is waited. If magnetic flux saturation does not occur, the two thyristors of the remaining phase are turned on sequentially.

[0045] The present invention provides a forced commutation process suitable for a three-phase, three-wire power supply switching device. Referring to Fig. 8 in conjunction with Fig. 6, this forced commutation process first turns off the first switch 311, the second switch 312, and the third switch 313 connected to the main power supply S-pri. Then, the magnetic flux speeds of the first winding W12, the second winding W23, and the third winding W31 of the three-phase transformer 33 are detected, and the winding with the fastest magnetic flux switching speed is selected as the fastest magnetic flux switching winding (step S201). For example, the first winding W12 may be selected as the fastest magnetic flux switching winding, but the present invention is not limited to this.

[0046] Next, two of the fourth switch 321, fifth switch 322, and sixth switch 323 electrically connected to the fastest magnetic flux switching winding are turned on (step S202). If the first winding W12 is the fastest magnetic flux switching winding, the fourth switch 321 and fifth switch 322 of the second power switch group 32 are turned on. Incidentally, if the second winding W23 is the fastest magnetic flux switching winding, the fifth switch 322 and sixth switch 323 of the second power switch group 32 are turned on.

[0047] Finally, among the fourth switch 321, the fifth switch 322, and the sixth switch 323, those that are not turned on are turned on (step S203). If the first winding W12 is the fastest magnetic flux switching winding, the remaining sixth switch 323 that is not turned on is turned on. Incidentally, if the second winding W23 is the fastest magnetic flux switching winding, the remaining fourth switch 321 that is not turned on is turned on.

[0048] Therefore, by evaluating and considering the above-mentioned conditions for permission of forced commutation, the polarity of magnetic flux deviation, and the polarity of voltage, it is possible to realize the optimal timing for executing forced commutation of the thyristors, and to effectively achieve switching between the two power sources.

[0049] It should be noted that the above description is given using the example of "fastest magnetic flux switching." However, other embodiments of the present invention may be implemented using the example of "maximum magnetic flux," and should be included within the scope of the present invention. Modifications or modifications that can be easily conceived by a person skilled in the art of the present invention are also included within the scope of the present invention.

[0050] 7 is a circuit block diagram of a three-phase four-wire power supply switching device according to the present invention. As shown in FIG. 7, two power supplies including a main power supply S-pri and a standby power supply S-alt are connected to a downstream three-phase transformer 43 via respective three-phase static switch devices 41 and 42.

[0051] 7, the three-phase power supply switching device includes a first power supply S-pri and a second power supply S-alt, each having three-phase AC power. The power supply switching device includes a first power supply switch group 41 and a second power supply switch group 42. The first power supply switch group 41 includes a first switch 411, a second switch 412, and a third switch 413, which are electrically connected in sequence to the first phase (R phase), second phase (S phase), and third phase (T phase) of the first power supply S-pri. The second power supply switch group 42 includes a fourth switch 421, a fifth switch 422, and a sixth switch 423, which are electrically connected in sequence to the first phase (R phase), second phase (S phase), and third phase (T phase) of the second power supply S-alt.

[0052] Three-phase transformer 43 includes a first winding W11, a second winding W22, and a third winding W33. Furthermore, the first winding W11, the second winding W22, and the third winding W33 of three-phase transformer 43 are arranged in a star-connection configuration (Y connection) to form one common node Nc and three nodes N1, N2, and N3, and the common node Nc is grounded to GND. Furthermore, first node N1 is connected to first switch 411 and fourth switch 421, second node N2 is connected to second switch 412 and fifth switch 422, and third node N3 is connected to third switch 413 and sixth switch 423.

[0053] By the way, there are common problems with three-phase four-wire systems: one is over-excitation and the other is passive excitation.

[0054] Regarding the problem of over-excitation, please refer to the corresponding explanation above, so we will omit it here. Regarding the problem of passive excitation, when performing forced commutation on a three-phase four-wire device, it is not possible to turn on only two thyristors, because when two thyristors are turned on, the third thyristor is affected by magnetic flux even if it is not turned on.

[0055] Therefore, the present invention can effectively achieve switching between two power sources to avoid the above-mentioned problems of over-excitation and passive excitation. When an abnormality occurs in the main power source S-pri, all thyristors connected to the main power source S-pri are first turned off by controlling the gate. Then, permission for forced commutation (a ticket) is obtained and one thyristor in one phase is selected to be turned on to avoid passive excitation. After that, a half-cycle is waited. If the current time is a positive half-cycle, for example, another thyristor is turned on in the next negative half-cycle, completing the conduction of both thyristors in one phase.

[0056] The timing to turn on the remaining two phase thyristors is determined based on whether or not magnetic flux saturation occurs after the calculated future magnetic flux is applied. If magnetic flux saturation occurs, the timing to turn on is awaited. If magnetic flux saturation does not occur, the four thyristors of the remaining two phases are turned on in sequence.

[0057] The present invention provides a forced commutation process suitable for a three-phase, four-wire power supply switching device. Referring to FIG. 9 in conjunction with FIG. 7, this forced commutation process first turns off the first switch 411, the second switch 412, and the third switch 413 connected to the main power supply S-pri. Then, the magnetic flux speeds of the first winding W11, the second winding W22, and the third winding W33 of the three-phase transformer 43 are detected, and the winding with the fastest magnetic flux switching speed is selected as the fastest magnetic flux switching winding (step S301). For example, the first winding W11 may be selected as the fastest magnetic flux switching winding, but the present invention is not limited to this.

[0058] Next, one of the fourth switch 421, fifth switch 422, and sixth switch 423 electrically connected to the fastest magnetic flux switching winding is turned on (step S302). If the first winding W11 is the fastest magnetic flux switching winding, the fourth switch 421 of the second power switch group 42 is turned on. Incidentally, if the second winding W22 is the fastest magnetic flux switching winding, the fifth switch 422 of the second power switch group 42 is turned on.

[0059] Finally, two of the fourth switch 421, fifth switch 422, and sixth switch 423 that are not turned on are turned on (step S303). If the first winding W11 is the fastest magnetic flux switching winding, the remaining fifth switch 422 and sixth switch 423 that are not turned on are turned on. Incidentally, if the second winding W22 is the fastest magnetic flux switching winding, the remaining fourth switch 421 and sixth switch 423 that are not turned on are turned on.

[0060] Therefore, by evaluating and considering the above-mentioned conditions for permission of forced commutation, the polarity of magnetic flux deviation, and the polarity of voltage, it is possible to realize the optimal timing for executing forced commutation of the thyristors, and to effectively achieve switching between the two power sources.

[0061] The above describes in detail preferred embodiments of the present invention with reference to the accompanying drawings. However, it goes without saying that the present invention is not limited to such examples, and does not limit the scope of the present invention. The entire scope of the present invention is based on the following claims. The spirit of the present invention and similar modifications that satisfy the claims of the present invention should be included in the scope of the present invention. Those skilled in the art can easily think of modifications and alterations within the technical scope of the present invention, and such modifications and alterations are also included in the scope of the following claims. [Explanation of symbols]

[0062] 100 Power Switching Device 110 1st power supply 111 2nd power supply 130 First static switch 131 Second static switch 130a 1st thyristor 130b Second thyristor 131a Third thyristor 131b 4th thyristor 122 First voltage sensor 123 Second voltage sensor 124 Third voltage sensor 132 First current sensor 133 Second current sensor 134 Controller 120 Inductive devices 120A primary winding 120B secondary winding 121 Load V1 First voltage signal V2 Second voltage signal Vo 3rd voltage signal I1 1st current signal I2 2nd current signal Sc1 First control signal Sc2 Second control signal Sc3 Third control signal Sc4 4th control signal f1 First magnetic flux f2 Second magnetic flux fo third magnetic flux S-pri main power supply (1st power supply) S-alt standby power supply (second power supply) ipri, ialt current V pri , V alt Voltage Vload Load voltage T1P, T1N, T2P, T2N thyristors ΔV pri Voltage difference V THz Voltage Threshold 31 First power switch group 32 Second power switch group 311 First Switch 312 Second Switch 313 Third Switch 321 4th Switch 322 5th Switch 323 6th Switch 33 Three-phase transformer W12 1st winding W23 Second winding W31 3rd winding N1 First common node N2 Second common node N3 Third common node 41 First power switch group 42 Second power switch group 411 First Switch 412 Second Switch 413 Third Switch 421 4th Switch 422 5th Switch 423 6th Switch 43 Three-phase transformer W11 First winding W22 2nd winding W33 3rd winding GND grounding

Claims

1. A power supply switching device including a first power supply and a second power supply having three-phase AC power, a first power supply switch group including a first switch, a second switch, and a third switch electrically connected to a first phase, a second phase, and a third phase of the first power supply in that order; a second power supply switch group including a fourth switch, a fifth switch, and a sixth switch electrically connected to a first phase, a second phase, and a third phase of the second power supply in this order; a three-phase transformer including a first winding, a second winding, and a third winding arranged in a delta configuration to form a first common node, a second common node, and a third common node; the first common node is connected to the first switch and the fourth switch, the second common node is connected to the second switch and the fifth switch, and the third common node is connected to the third switch and the sixth switch; the power supply switching device provides a forced commutation process for switching the first power supply to the second power supply; The forced commutation step includes: turning off the first switch, the second switch, and the third switch connected to the first power supply; detecting magnetic fluxes of the first winding, the second winding, and the third winding, and selecting a winding with the fastest flux switching speed as a fastest flux switching winding; turning on two switches among the fourth switch, the fifth switch, and the sixth switch electrically connected to the fastest magnetic flux switching winding; turning on any of the fourth switch, the fifth switch, and the sixth switch that is not turned on. Power switching device.

2. 2. The power supply switching device according to claim 1, wherein the first switch, the second switch, and the third switch each include two thyristors connected in anti-parallel, and the fourth switch, the fifth switch, and the sixth switch each include two thyristors connected in anti-parallel.

3. 3. The power supply switching device according to claim 2, wherein, when switching from the first power supply to the second power supply, if it is determined in the forced commutation step that the current flowing out from the first power supply is greater than zero, it is further determined whether or not the voltage of the second power supply is greater than a load voltage.

4. 4. The power supply switching device according to claim 3, wherein when the voltage of the second power supply is greater than the load voltage, the controller turns on the thyristor connected in a forward direction to the second power supply based on the voltage, thereby reverse-exciting the thyristor connected to the first power supply and not completely turned off, and turning it completely off.

5. 3. The power supply switching device according to claim 2, wherein, when switching from the first power supply to the second power supply, if it is determined in the forced commutation step that the current flowing out from the first power supply is less than zero, it is further determined whether or not the voltage of the second power supply is less than a load voltage.

6. 6. The power supply switching device according to claim 5, wherein when the voltage is smaller than the load voltage, the controller turns on the thyristor connected in the reverse direction to the second power supply based on the load voltage, thereby completely turning off the thyristor connected to the first power supply and not completely turned off.

7. 3. The power supply switching device according to claim 2, wherein, when the first power supply is to be switched to the second power supply, if in the forced commutation step a voltage difference between the voltage of the second power supply and a load voltage is greater than a voltage threshold, it means that the thyristor connected to the first power supply is already completely turned off.

8. 3. The power supply switching device according to claim 2, wherein when the polarity of the magnetic flux deviation and the polarity of the voltage are the same, the forced commutation step is executed as long as magnetic flux saturation does not occur.

9. 3. The power supply switching device according to claim 2, wherein the forced commutation step is executed when the polarity of the magnetic flux deviation and the polarity of the voltage are different.

10. A power supply switching device including a first power supply and a second power supply having three-phase AC power, a first power supply switch group including a first switch, a second switch, and a third switch electrically connected to a first phase, a second phase, and a third phase of the first power supply in that order; a second power supply switch group including a fourth switch, a fifth switch, and a sixth switch electrically connected to a first phase, a second phase, and a third phase of the second power supply in this order; a three-phase transformer having a first winding, a second winding, and a third winding arranged in a star-connected configuration to form a common node, a first node, a second node, and a third node; the common node is grounded, the first node is connected to the first switch and the fourth switch, the second node is connected to the second switch and the fifth switch, and the third node is connected to the third switch and the sixth switch; the power supply switching device provides a forced commutation process for switching the first power supply to the second power supply; The forced commutation step includes: turning off the first switch, the second switch, and the third switch connected to the first power supply; detecting magnetic fluxes of the first winding, the second winding, and the third winding, and selecting a winding with the fastest flux switching speed as a fastest flux switching winding; turning on one of the fourth switch, the fifth switch, and the sixth switch electrically connected to the fastest magnetic flux switching winding; turning on two of the fourth switch, the fifth switch, and the sixth switch that are not turned on; Power switching device.

11. 11. The power supply switching device according to claim 10, wherein the first switch, the second switch, and the third switch each include two thyristors connected in anti-parallel, and the fourth switch, the fifth switch, and the sixth switch each include two thyristors connected in anti-parallel.

12. 12. The power supply switching device according to claim 11, wherein, when switching from the first power supply to the second power supply, if it is determined in the forced commutation step that the current flowing out from the first power supply is greater than zero, it is further determined whether or not a voltage of the second power supply is greater than a load voltage.

13. 13. The power supply switching device according to claim 12, wherein when the voltage of the second power supply is greater than the load voltage, the controller turns on the thyristor connected to the second power supply in a forward direction based on the voltage, thereby reverse-exciting the thyristor connected to the first power supply and not completely turned off, and turning it completely off.

14. 12. The power supply switching device according to claim 11, wherein, when attempting to switch from the first power supply to the second power supply, if it is determined in the forced commutation step that the current flowing out from the first power supply is less than zero, it is further determined whether or not the voltage of the second power supply is less than a load voltage.

15. 15. The power supply switching device of claim 14, wherein when the voltage is smaller than the load voltage, the controller turns on the thyristor connected in a reverse direction to the second power supply based on the load voltage, thereby completely turning off the thyristor connected to the first power supply and not completely turned off.

16. 12. The power supply switching device according to claim 11, wherein, when attempting to switch the first power supply to the second power supply, if in the forced commutation step a voltage difference between the voltage of the second power supply and a load voltage is greater than a voltage threshold, it means that the thyristor connected to the first power supply is already completely turned off.

17. 12. The power supply switching device according to claim 11, wherein when the polarity of the magnetic flux deviation and the polarity of the voltage are the same, the forced commutation step is executed as long as magnetic flux saturation does not occur.

18. 12. The power supply switching device according to claim 11, wherein the forced commutation step is executed when the polarity of the magnetic flux deviation and the polarity of the voltage are different.

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