Method for switching power supplies with quick-switching device, and quick-switching device

Abstract

The present invention provides a method for switching power supplies with a quick-switching device, and a quick-switching device, the method comprising: acquiring an instantaneous value of a target voltage on the bus according to a preset cycle, after identifying that a main power supply has been disconnected; acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to a formula, while regarding an angular frequency of voltage as being constant within a short period of time; and determining whether to execute an operation of connecting the bus to a backup power supply, according to the real-time peak value and the real-time phase angle.

Description

[0001]Siemens Aktiengesellschaft 1 METHOD FOR SWITCHING POWER SUPPLIES WITH QUICK-SWITCHING DEVICE, AND QUICK-SWITCHING DEVICE TECHNICAL FIELD The present invention relates to the field of electric power systems, in particular to a method for switching power supplies with a quick-switching device, and a quick-switching device. BACKGROUND ART In many types of large-scale industry, a power supply system generally has two independent power supplies to ensure reliable and continuous supply of power, with the main type of electrical device being electric motors. The two power supplies may serve as backup for each other, or one may be operational while the other serves as backup; if a fault occurs in one power supply, the load needs to be switched to the other power supply quickly and safely, to ensure the continuity of production. In the prior art, a quick-switching device is generally used to trigger a switching operation between the two power supplies, i.e. switch from an operational power supply to a backup power supply. As an example for illustration, an electric power system generally comprises a quick-switching device and at least two power supplies; Fig.1 shows a scenario in which there are two power supplies. The power supply that is currently operational may serve as a main power supply, while the other power supply serves as a backup power supply. As shown in Fig. 1, the main power supply P1 is connected to a bus via an incoming line, and the backup power supply P2 is likewise connected to the bus via an incoming line. The three phases included in the incoming line are phase A, phase B and phase C, which are respectively connected to the corresponding three phases of the bus BB. Each load is connected to the bus BB via an outgoing line. That is, the incoming line, the bus and the outgoing line on phase A are connected together, and the respective incoming lines, buses and outgoing lines on phase B and phase C are likewise connected together. The incoming line of the main power supply P1 has a switch CB1, and the main power supply P1 can be disconnected from the bus BB by means of the switch CB1. The incoming line of the backup power supply P2 has a switch CB2, and the backup power supply P2 can be Siemens Aktiengesellschaft 2 disconnected from the bus BB by means of the switch CB2. When a fault occurs in the electric power system, a relay protection device will be activated, disconnecting the first main power supply P1 that is currently supplying power, and a quick-switching device 101 will quickly switch the bus BB to the backup power supply P2, so that the backup power supply P2 supplies power to the bus BB. There are many ways in which switching can be achieved; among these, the most ideal quick-switching method has the following conditions for quick switching to be achieved: the frequency difference of the bus and backup power supply is less than the quick switching frequency difference, and the phase angle difference of the bus and backup power supply is less than the quick switching phase angle difference. When quick switching is unsuccessful, synchronous capture switching is second only to quick switching; the conditions for synchronous capture switching to be achieved are that when the backup power supply is connected, the phase angle difference of the bus and backup power supply is less than the synchronous capture switching phase angle difference. It can be seen that these two switching methods, which are the fastest, both require phase angle differences to be acquired. To acquire the phase angle differences, the phase angle on the bus must be acquired in real time, so as to be combined with the phase angle of the backup power supply to calculate whether it meets the switching condition. In the prior art, in order to calculate the phase angle of the bus, the bus voltage must be sampled in real time to acquire the instantaneous voltage value, and the phase angle must be calculated from the instantaneous voltage value using a Fourier transform. This method requires a large number of samples; for example, in the case of a 50 Hz electric power system, 1 sample is taken every 1 millisecond, and at least 20 milliseconds are needed to calculate the phase angle of the bus. Such a method of calculation is time-consuming, and it is highly likely that the opportunity for connection by quick switching or synchronous capture switching will be missed. SUMMARY OF THE INVENTION In view of the above, the present invention proposes a method for switching power supplies with a quick-switching device, the quick-switching device being Siemens Aktiengesellschaft 3 located in an electric power system, the electric power system comprising a main power supply and a backup power supply, the quick-switching device being able to trigger switching between two power supplies, the main power supply and the backup power supply both being connected to a bus, and the method comprising: acquiring an instantaneous value of a target voltage on the bus according to a preset cycle, after identifying that the main power supply has been disconnected; acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula: A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, M is the real-time peak value of the target voltage, φ is the real-time phase angle of the target voltage, ω is the angular frequency of the target voltage, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i; determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle. According to the method described above, optionally, the value of k is 4 - 5. According to the method described above, optionally, the step of acquiring an instantaneous value of a target voltage on the bus according to a preset cycle Siemens Aktiengesellschaft 4 comprises: simultaneously acquiring an instantaneous value of a target voltage corresponding to a target phase of the bus according to a preset cycle, the target phase being one of three phases of the bus; the step of acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula comprises: acquiring a real-time peak value and a real-time phase angle of the target voltage of the target phase according to the following formula. According to the method described above, optionally, the step of acquiring an instantaneous value of a target voltage on the bus according to a preset cycle comprises: simultaneously acquiring an instantaneous value of a target voltage corresponding to each phase of the bus according to a preset cycle; the step of acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula comprises: acquiring a real-time peak value and a real-time phase angle of the target voltage of each phase on the bus according to the following formula; the step of determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle, comprises: taking the mean value of the real-time peak values of all of the phases to be a final real-time peak value, and taking the mean value of the real-time phase angles of all of the phases to be a final real-time phase angle; and determining whether to execute an operation of connecting the bus to the backup power supply, according to the final real-time peak value and the final real-time phase angle. The present invention further provides a quick-switching device, the quick- switching device being located in an electric power system, the electric power system comprising a main power supply and a backup power supply, the quick- switching device being able to trigger switching between two power supplies, the main power supply and the backup power supply both being connected to a bus, and the quick-switching device comprising: a sampling unit, for acquiring an instantaneous value of a target voltage on the bus according to a preset cycle; an acquisition unit, for acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula: Siemens Aktiengesellschaft 5 A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, sin(ω^^) cos(ω^^) sin(ω^^) cos(ω^^)ù ú … … ú sin(ω^^) cos(ω^^)， ú … … ú sin(ω^^) cos(ω^^)û M is the real-time peak value of the target voltage, φ is the real-time phase angle of the target voltage, ω is the angular frequency of the target voltage, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i; a determining unit, for determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle, after identifying that the main power supply has been disconnected. According to the quick-switching device described above, optionally, the value of k is 4 - 5. According to the quick-switching device described above, optionally, the sampling unit is specifically used for: simultaneously acquiring an instantaneous value of a target voltage corresponding to a target phase of the bus according to a preset cycle, the target phase being one of three phases of the bus; the acquisition unit is specifically used for: acquiring a real-time peak value and a real-time phase angle of the target voltage of the target phase according to the following formula. Siemens Aktiengesellschaft 6 According to the quick-switching device described above, optionally, the sampling unit is specifically used for: simultaneously acquiring an instantaneous value of a target voltage corresponding to each phase of the bus according to a preset cycle; the acquisition unit is specifically used for: acquiring a real-time peak value and a real-time phase angle of the target voltage of each phase on the bus according to the following formula; the determining unit is specifically used for: taking the mean value of the real- time peak values of all of the phases to be a final real-time peak value, and taking the mean value of the real-time phase angles of all of the phases to be a final real-time phase angle; and determining whether to execute an operation of connecting the bus to the backup power supply, according to the final real-time peak value and the final real-time phase angle. The present invention also provides a quick-switching device, comprising: at least one memory, used for storing instructions; at least one processor, configured to execute the method for switching power supplies with a quick-switching device as described in any one of the embodiments above according to the instructions stored in the memory. The present invention also provides a readable storage medium, wherein machine-readable instructions are stored in the readable storage medium, and when the machine-readable instructions are executed by a machine, the machine will execute the method for switching power supplies with a quick-switching device as described in any one of the embodiments above. It can be seen from the solution above that, by regarding the angular frequency on the bus as constant within a short period of time, and by means of the formulae above, it is possible to calculate the real-time peak value and real-time phase angle of the target voltage of the bus using fewer sampling points. Thus, the right time to connect the backup power supply can be determined more quickly, so the solution is especially suitable for quick switching. BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of the present invention are described in detail below with reference to the drawings, to give those skilled in the art a clearer understanding of the abovementioned and other features and advantages of the Siemens Aktiengesellschaft 7 present invention. In the drawings: Fig.1 is a schematic flowchart of a method for switching power supplies with a quick-switching device according to an embodiment of the present invention. Fig.2A is a schematic flowchart of a method for switching power supplies with a quick-switching device according to another embodiment of the present invention. Fig.2B is a schematic drawing of a curve of the real-time phase angle, and a curve of the real phase angle, of the voltage acquired using the method for switching power supplies with a quick-switching device in another embodiment of the present invention. Fig.2C is a schematic drawing of a curve of the real-time peak value, and a curve of the real amplitude, of the voltage acquired using the method for switching power supplies with a quick-switching device in another embodiment of the present invention. Fig.3A is a schematic flowchart of a method for switching power supplies with a quick-switching device according to another embodiment of the present invention. Fig.3B is a schematic drawing of a curve of the real-time phase angle, and a curve of the real phase angle, of the voltage acquired using the method for switching power supplies with a quick-switching device in another embodiment of the present invention. Fig.3C is a schematic drawing of a curve of the real-time peak value, and a curve of the real amplitude, of the voltage acquired using the method for switching power supplies with a quick-switching device in another embodiment of the present invention. Fig.4 is a schematic structural drawing of a quick-switching device according to an embodiment of the present invention. Siemens Aktiengesellschaft 8 DETAILED DESCRIPTION OF EMBODIMENTS To clarify the objective, technical solution and advantages of the present invention, the present invention is explained in further detail below through embodiments. A noun or pronoun referring to a person in the present patent application is not limited to a specific gender. The voltage of an electric power system is an AC voltage, so the instantaneous value of voltage varies in real time. A quick-switching device samples voltage periodically, in order to calculate phase angle. When the main power supply is disconnected, the bus loses its supply of power, the amplitude of the voltage thereon gradually falls, and the frequency of the voltage thereof also gradually falls. However, the frequency changes slowly, and the angular frequency of the voltage is ω = 2πf, where f is the frequency of the voltage. Therefore, within a short period of time, such as 4 - 5 ms, the angular frequency of the voltage may be regarded as remaining unchanged. Based on this, the inventors of the present invention propose a method for switching power supplies with a quick-switching device. EMBODIMENT 1 This embodiment provides a method for switching power supplies with a quick- switching device, the method being executed by a quick-switching device. The quick-switching device is located in an electric power system, the electric power system comprising a main power supply and a backup power supply, the quick- switching device being able to trigger switching between two power supplies, the main power supply and the backup power supply both being connected to a bus. Fig.1 shows a schematic flowchart of a method for switching power supplies according to this embodiment. The method for switching power supplies comprises: step 101, after identifying that the main power supply has been disconnected, acquiring an instantaneous value of a target voltage on the bus according to a preset cycle. Siemens Aktiengesellschaft 9 The quick-switching device monitors voltage on the bus in real time, and acquires an instantaneous value of voltage according to the preset cycle. The preset cycle in this step is a sampling period. The specific sampling period may be set according to actual needs, e.g. once per millisecond. In this embodiment, after identifying that the main power supply has been disconnected, the quick-switching device continues to monitor voltage on the bus in real time, and calculates a real-time peak value and a real-time phase angle of voltage according to the acquired voltage sample values. In this example, the voltage on the bus which is sampled after identifying that the main power supply has been disconnected is called the target voltage. To identify whether the main power supply has been disconnected, information such as bus voltage, bus current and / or bus frequency may be monitored; the specific method of identification may be any prior art, which is not described again here. The quick-switching device may acquire the voltage of any phase on the bus as the target voltage, the acquired voltage being the instantaneous value of the target voltage of the bus on this phase; of course, the quick-switching device could also acquire voltages on three phases, and process the voltages on the three phases to serve as the target voltage. The specific choice may be made according to actual needs; no further description is given here. Step 102: a real-time peak value and a real-time phase angle of the target voltage on the bus are acquired according to the following formula. A = (^′^)^^^′^ Mcos(φ) wherein ^ = ^ Msin(φ)^ ê … … ú ë sin(ω^^) cos(ω^^)û Siemens Aktiengesellschaft 10 M is the real-time peak value of the target voltage, φ is the real-time phase angle of the target voltage, ω is the angular frequency of the target voltage, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i. It can be imagined that, since the target voltage is gradually changing, the peak value thereof is also changing all the time, so the real-time peak value of voltage needs to be determined according to the sample values. Here, k is for example 4 - 5, and the sampling frequency thereof is for example once per millisecond. If k is 4 - 5, there are 4 - 5 sample values, so the sampling window which elapses is 4 - 5 ms, which is a very short time, so change in the angular frequency of bus voltage can be neglected. Specifically, the angular frequency of bus voltage is ω = 2πf, where f is the real-time frequency of bus voltage. Since the main power supply is disconnected, the bus loses its supply of electric power, so the voltage thereon gradually falls, and the frequency of this voltage also gradually falls. In this embodiment, after identifying that the main power supply has been disconnected, calculation of M and φ is begun immediately, using a small number of sample values, and the sampling window is small, so the change in the frequency of the voltage can be neglected, and correspondingly, the change in the angular frequency can also be neglected. In this embodiment, the angular frequency of the target voltage may be calculated using nominal frequency, i.e. f = 50 Hz. This 50 Hz is the nominal frequency of the grid. Of course, the angular frequency of the target voltage could also be calculated using an existing method, which is not described again in detail here. The following relation links the instantaneous value of voltage to the real-time peak value of voltage, the real-time phase angle and the angular frequency. ^(^)= ^sin(ωt + φ)= ^^^^(φ)^^^(ωt)+ ^^^^(φ)^^^(ωt) Siemens Aktiengesellschaft 11 where ^(^) denotes the instantaneous value of voltage sampled at time t, ω denotes the angular frequency of voltage, φ denotes the phase angle of voltage, M denotes the peak value of voltage, and t denotes the current time. Taking the point in time when sampling begins to be time 0, t denotes the current time, and the point in time when sampling begins is the starting point of the sampling window for calculating the real-time peak value and the real-time phase angle. Thus, the following formulae may be used to express the instantaneous value of the sampled voltage: ^(^^) = ^sin(ω^^+ φ) = ^^^^(φ)^^^(ω^^) + ^^^^(φ)^^^(ω^^) ^(^^)= ^sin(ω^^+ φ)= ^^^^(φ)^^^(ω^^)+ ^^^^(φ)^^^(ω^^)…… ^(^^)= ^sin(ω^^+ φ)= ^^^^(φ)^^^(ω^^)+ ^^^^(φ)^^^(ω^^)…… ^(^^)= ^sin(ω^^+ φ)= ^^^^(φ)^^^(ω^^)+ ^^^^(φ)^^^(ω^^)where denotes the time corresponding to the ith sampling point, e.g.1 sample per millisecond; taking the time when sampling of the target voltage begins to be 0 ms, denotes 1 ms, and denotes 2 ms. Thus, the formulae above may be alternatively written as: Siemens Aktiengesellschaft 12 Thus, A = (^′^)^^^′^. Step 103: determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle. The quick-switching device may further determine the connection method and the right time for connection of the backup power supply, according to the acquired real-time peak value and real-time phase angle. For example, the real- time peak value cannot be lower than a certain value, and the difference between the phase angle of the backup power supply and the real-time phase angle must meet a switching condition, which may be specifically determined according to actual needs, and is not described further here. In addition, the real-time peak value of the target voltage may also be used for other judgments, e.g. for judging whether the bus has lost voltage, etc. According to the present invention, by regarding the angular frequency on the bus as constant within a short period of time, and by means of the formulae above, it is possible to calculate the real-time peak value and real-time phase angle of the target voltage of the bus using fewer sampling points. Thus, the right time to connect the backup power supply can be determined more quickly, so the method is especially suitable for quick switching. EMBODIMENT 2 This embodiment further describes the method for switching power supplies in embodiment 1. Siemens Aktiengesellschaft 13 Fig.2A shows a schematic flowchart of a method for switching power supplies with a quick-switching device according to this embodiment. The method for switching power supplies with a quick-switching device comprises: step 201, after identifying that the main power supply has been disconnected, simultaneously acquiring an instantaneous value of a target voltage corresponding to a target phase of the bus according to a preset cycle. An electric power system generally has three phases: phase A, phase B and phase C. The target phase in this embodiment may be any one of the three phases, or a phase determined as being non-faulty by another method; the specific choice may be made according to actual needs, and no further description is given here. Step 202: a real-time peak value and a real-time phase angle of the target voltage of a target phase of the bus are acquired according to the following formula: A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, M is the real-time peak value of the target voltage of the target phase, φ is the real-time phase angle of the target voltage of the target phase, ω is the angular frequency of the target voltage of the target phase, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage of the target phase corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i. Siemens Aktiengesellschaft 14 Specifically, this step is the same as step 102, so is not described again here. Step 203: determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle of the target phase. Specifically, this step is the same as step 103, so is not described again here. Fig.2B shows a curve N1 of the real-time peak value, and a curve N2 of the real amplitude, of the target voltage acquired using the method for switching power supplies with a quick-switching device in this embodiment. It can be seen from the figure that the two curves nearly coincide. The schematic drawing of Fig.2C is a curve R1 of the real-time phase angle, and a curve R2 of the real phase angle, of the target voltage acquired using the method for switching power supplies with a quick-switching device in this embodiment. It can be seen from the figure that the two curves nearly coincide. Thus, it has been verified that even if the angular frequency of the target voltage is imprecise, for example in the case where the nominal angular frequency is used in a fixed manner, the real-time peak value and real-time phase angle obtained by the method of this embodiment tally with the real values quite well; for details, see Figs.2B and 2C. Here, the nominal angular frequency may be acquired using the nominal frequency of the grid, which for example is 50 Hz. According to this embodiment, using one of the three phases of the bus as a target phase and determining the real-time peak value and real-time phase angle of the bus voltage by means of the target phase involves little computation, and is convenient to implement. EMBODIMENT 3 This embodiment further describes the method for switching power supplies in embodiment 1. Fig.3A shows a schematic flowchart of a method for switching power supplies with a quick-switching device according to this embodiment. The method for switching power supplies with a quick-switching device comprises: Siemens Aktiengesellschaft 15 step 301, after identifying that the main power supply has been disconnected, simultaneously acquiring an instantaneous value of a target voltage corresponding to each phase of the bus according to a preset cycle. An electric power system generally has three phases: phase A, phase B and phase C. In this embodiment, an instantaneous value of voltage on each phase of the bus may be simultaneously acquired, i.e. the voltage of each phase is a target voltage. step 302: a real-time peak value and a real-time phase angle of the target voltage of each phase on the bus are acquired according to the following formula. A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, M is the real-time peak value, φ is the real-time phase angle, ω is the angular frequency of the target voltage, is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i. The value of M finally obtained for phase A may be denoted ^(^), the value of M finally obtained for phase B may be denoted ^(^), and the value of M finally obtained for phase C may be denoted ^(^). The value of φ finally obtained for phase A may be denoted φ(^), the value of φ finally obtained for phase B may Siemens Aktiengesellschaft 16 be denoted φ(^), and the value of φ finally obtained for phase C may be denoted φ(^). Step 303: the mean value of the real-time peak values of all of the phases is taken to be a final real-time peak value, and the mean value of the real-time phase angles of all of the phases is taken to be a final real-time phase angle. That is, the final real-time peak value = [^(^)+ ^(^)+ ^(^)] / 3, and the final real-time phase angle Step 304: determining whether to execute an operation of connecting the bus to the backup power supply, according to the final real-time peak value and the final real-time phase angle. This step has the same operation as step 103, so is not described again here. Fig.3B shows a schematic drawing of a curve Q1 of the final real-time peak value, and a curve Q2 of the real voltage amplitude, of the voltage acquired using the method for switching power supplies with a quick-switching device in this embodiment. Fig.3C shows a schematic drawing of a curve P1 of the final real- time phase angle, and a curve P2 of the real phase angle, of the voltage acquired using the method for switching power supplies with a quick-switching device in this embodiment. It can be seen from Figs.3B and 3C that in terms of the degree to which P1 tallies with P2 and the degree to which Q1 tallies with Q2 in this embodiment, the result is better than in Embodiment 2. In this embodiment, the voltages of the three phases on the bus are sampled, and a final real-time peak value and a final real-time phase angle of voltage on the bus are acquired according to the mean value of real-time peak values and the mean value of real- time phase angles of voltages acquired for all of the phases. Thus, even if the angular frequency is imprecise, and there is fluctuation error in the real-time peak value and real-time phase angle acquired using a single phase, the errors of the three phases are symmetric, and the effects of changes in angular frequency can be greatly reduced by using the mean value of real-time peak values and the mean value of real-time phase angles of the voltages of three phases. Thus, the errors will cancel each other out in the real-time peak value and real-time phase Siemens Aktiengesellschaft 17 obtained using the mean values for the three phases, so precision is still very high when the angular frequency is imprecise. EMBODIMENT 4 This embodiment provides a quick-switching device, used for the method for switching power supplies with a quick-switching device in embodiment 1. The quick-switching device is located in an electric power system, the electric power system comprising a main power supply and a backup power supply, the quick- switching device being able to trigger switching between two power supplies, the main power supply and the backup power supply both being connected to a bus. Fig.4 shows a structural schematic drawing of the quick-switching device according to this embodiment. The quick-switching device comprises a sampling unit 401, an acquisition unit 402 and a determining unit 403. The sampling unit 401 is used for acquiring an instantaneous value of a target voltage on the bus according to a preset cycle. The acquisition unit 402 is used for acquiring a real-time peak value and a real- time phase angle of the target voltage on the bus according to the following formula: A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, Siemens Aktiengesellschaft 18 M is the real-time peak value of the target voltage, φ is the real-time phase angle of the target voltage, ω is the angular frequency of the target voltage, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i. The using unit is specifically used for determining whether to execute an operation of connecting the bus to the backup power supply, according to the real- time peak value and the real-time phase angle, after identifying that the main power supply has been disconnected. As an exemplary illustration, the value of k is 4 - 5. The methods of operation of the units in this embodiment are the same as those in the embodiments described above, so they are not described again here. According to the present invention, by regarding the angular frequency on the bus as constant within a short period of time, and by means of the formulae above, the quick-switching device is able to calculate the real-time peak value and real-time phase angle of the target voltage of the bus using fewer sampling points. Thus, the right time to connect the backup power supply can be determined more quickly, so the device is especially suitable for quick switching. EMBODIMENT 5 This embodiment will further explain the quick switching device of embodiment 4. Example 1: The using unit of the quick-switching device is used for simultaneously acquiring an instantaneous value of a target voltage corresponding to a target phase of the bus according to a preset cycle, the target phase being one of three phases of the bus; the acquisition unit 402 is used for acquiring a real-time peak value and a real- time phase angle of the target voltage of the target phase according to the following formula: Siemens Aktiengesellschaft 19 A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, sin(ω^^) cos(ω^^) sin(ω^^) cos(ω^^)ù ú … … ú sin(ω^^) cos(ω^^)， ú … … ú sin(ω^^) cos(ω^^)û Thus, using one of the three phases of the bus as a target phase and determining the real-time peak value and real-time phase angle of the bus voltage by means of the target phase involves little computation, and is convenient to implement. Example 2: The sampling unit 401 of the quick-switching device is specifically used for simultaneously acquiring an instantaneous value of a target voltage corresponding to each phase of the bus according to a preset cycle. The acquisition unit 402 is used for acquiring a real-time peak value and a real- time phase angle of the target voltage of each phase on the bus according to the following formula: A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^, Siemens Aktiengesellschaft 20 The value of M finally obtained for phase A may be denoted ^(^), the value of M finally obtained for phase B may be denoted ^(^), and the value of M finally obtained for phase C may be denoted ^(^). The value of φ finally obtained for phase A may be denoted φ(^), the value of φ finally obtained for phase B may be denoted φ(^), and the value of φ finally obtained for phase C may be denotedφ(^).The determining unit 403 is specifically used for: taking the mean value of the real-time peak values of all of the phases to be a final real-time peak value, and taking the mean value of the real-time phase angles of all of the phases to be a final real-time phase angle; and determining whether to execute an operation of connecting the bus to the backup power supply, according to the final real-time peak value and the final real-time phase angle. That is, the final real-time peak value = [^(^)+ ^(^)+ ^(^)] / 3, and the final real-time phase angle = [φ(^)+ φ(^)+ φ(^)] / 3. The methods of operation of the units in this embodiment are the same as those in the embodiments described above, so they are not described again here. In this embodiment, the voltages of the three phases on the bus are sampled, and a final real-time peak value and a final real-time phase angle of voltage on the bus are acquired according to the mean value of real-time peak values and the mean value of real-time phase angles of voltages acquired for all of the phases. Thus, even if the angular frequency is imprecise, and there is fluctuation error in the real-time peak value and real-time phase angle acquired using a single phase, the errors of the three phases are symmetric, and the effects of changes in angular frequency can be greatly reduced by using the mean value of real-time peak values and the mean value of real-time phase angles of the voltages of three phases. Thus, the errors will cancel each other out in the real-time peak value Siemens Aktiengesellschaft 21 and real-time phase obtained using the mean values for the three phases, so precision is still very high when the angular frequency is imprecise. The present invention further provides a quick-switching device, comprising at least one memory and at least one processor. The memory is used to store instructions. The processor is used to execute the method for switching power supplies with a quick-switching device described in any of the preceding embodiments, according to the instructions stored in the memory. Embodiments of the present invention further provide a readable storage medium. The readable storage medium has machine-readable instructions stored therein, and when the machine-readable instructions are executed by a machine, the machine will execute the method for switching power supplies with a quick- switching device described in any of the preceding embodiments. The readable medium stores machine-readable instructions that, when executed by a processor, cause the processor to execute any one of the above-described methods. Specifically, a system or device equipped with a readable storage medium may be provided; software program code realizing a function of any one of the embodiments above is stored on the readable storage medium, and a computer or processor of the system or device is caused to read and execute a machine-readable instruction stored in the readable storage medium. In this case, the function of any one of the above embodiments may be performed by a program code read from the readable medium, so a machine-readable code and a readable storage medium for storing the machine-readable code constitute a part of the present invention. Examples of readable storage media include floppy disks, hard disks, magneto- optical disks, optical disks (such as CD-ROM, CD-R, CD-RW, DVD-ROM, DVD- RAM, DVD-RW, DVD+RW), magnetic tapes, non-volatile memory cards and ROM. Optionally, the program code may be downloaded from a server computer or a cloud via a communication network. Those skilled in the art should understand that various changes in form and Siemens Aktiengesellschaft 22 modifications may be made to the embodiments disclosed above without departing from the substance of the invention. Thus, the scope of protection of the present invention shall be defined by the appended claims. It should be noted that not all steps and units in the above-described process flows and system structure diagrams are necessary, and some steps or units may be omitted according to actual needs. The sequence in which the steps are executed is not fixed, and may be adjusted as needed. The device structure described in the above embodiments may be either a physical structure or a logical structure, which means that some units may be implemented by the same physical entity, or some units may be implemented by a plurality of physical entities separately or by some parts of a plurality of independent devices jointly. In the embodiments above, a hardware unit may be realized in a mechanical or an electrical manner. For example, a hardware unit or processor may comprise a permanently dedicated circuit or logic (for example, a specialized processor, FPGA, or ASIC) to complete corresponding operations. A hardware unit or processor may further comprise programmable logic or circuits (such as general- purpose processors or other programmable processors), which may be temporarily set by software to complete corresponding operations. Particular embodiments (mechanical, or dedicated permanent circuitry, or temporarily set circuitry) may be determined based on considerations of cost and time. The above are merely preferred embodiments of the present invention, which are not intended to limit it. Any amendments, equivalent substitutions or improvements etc. made within the spirit and principles of the present invention shall be included in the scope of protection thereof.

Claims

Siemens Aktiengesellschaft 23 CLAIMS 1. A method for switching power supplies with a quick-switching device, the quick-switching device being located in an electric power system, the electric power system comprising a main power supply and a backup power supply, the quick-switching device being able to trigger switching between two power supplies, the main power supply and the backup power supply both being connected to a bus, and the method comprising: acquiring an instantaneous value of a target voltage on the bus according to a preset cycle, after identifying that the main power supply has been disconnected; wherein a real-time peak value and a real-time phase angle of the target voltage on the bus are acquired according to the following formula: A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^,M is the real-time peak value of the target voltage, φ is the real-time phase angle of the target voltage, ω is the angular frequency of the target voltage, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i; determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle.Siemens Aktiengesellschaft 24 2. The method as claimed in claim 1, wherein the value of k is 4 - 5.

3. The method as claimed in claim 1 or 2, wherein the step of acquiring an instantaneous value of a target voltage on the bus according to a preset cycle comprises: simultaneously acquiring an instantaneous value of a target voltage corresponding to a target phase of the bus according to a preset cycle, the target phase being one of three phases of the bus; the step of acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula comprises: acquiring a real-time peak value and a real-time phase angle of the target voltage of the target phase according to the following formula.

4. The method as claimed in claim 1 or 2, wherein the step of acquiring an instantaneous value of a target voltage on the bus according to a preset cycle comprises: simultaneously acquiring an instantaneous value of a target voltage corresponding to each phase of the bus according to a preset cycle; the step of acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula comprises: acquiring a real-time peak value and a real-time phase angle of the target voltage of each phase on the bus according to the following formula; the step of determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle, comprises: taking the mean value of the real-time peak values of all of the phases to be a final real-time peak value, and taking the mean value of the real-time phase angles of all of the phases to be a final real-time phase angle; and determining whether to execute an operation of connecting the bus to the backup power supply, according to the final real-time peak value and the final real-time phase angle.

5. A quick-switching device, the quick-switching device being located in an electric power system, the electric power system comprising a main power supply and a backup power supply, the quick-switching device being able to trigger switching between two power supplies, the main power supply and the backup power supply both being connected to a bus, and the quick-switching deviceSiemens Aktiengesellschaft 25 comprising: a sampling unit, for acquiring an instantaneous value of a target voltage on the bus according to a preset cycle; wherein the quick-switching device further comprises: an acquisition unit, for acquiring a real-time peak value and a real-time phase angle of the target voltage on the bus according to the following formula: A = (^′^)^^^′^ Mcos(φ) where ^ = ^ Msin(φ)^,M is the real-time peak value of the target voltage, φ is the real-time phase angle of the target voltage, ω is the angular frequency of the target voltage, ^^is the time corresponding to the ith sampling point, ^^is the instantaneous value of the target voltage corresponding to the ith sample value, k and i are both positive integers and k is greater than or equal to i; a determining unit, for determining whether to execute an operation of connecting the bus to the backup power supply, according to the real-time peak value and the real-time phase angle, after identifying that the main power supply has been disconnected.

6. The quick-switching device as claimed in claim 6, wherein the value of k is 4 - 5.

7. The quick-switching device as claimed in claim 5 or 6, wherein the sampling unit is specifically used for: simultaneously acquiring an instantaneousSiemens Aktiengesellschaft 26 value of a target voltage corresponding to a target phase of the bus according to a preset cycle, the target phase being one of three phases of the bus; the acquisition unit is specifically used for: acquiring a real-time peak value and a real-time phase angle of the target voltage of the target phase according to the following formula.

8. The quick-switching device as claimed in claim 5 or 6, wherein the sampling unit is specifically used for: simultaneously acquiring an instantaneous value of a target voltage corresponding to each phase of the bus according to a preset cycle; the acquisition unit is specifically used for: acquiring a real-time peak value and a real-time phase angle of the target voltage of each phase on the bus according to the following formula; the determining unit is specifically used for: taking the mean value of the real-time peak values of all of the phases to be a final real-time peak value, and taking the mean value of the real-time phase angles of all of the phases to be a final real-time phase angle; and determining whether to execute an operation of connecting the bus to the backup power supply, according to the final real-time peak value and the final real-time phase angle.

9. A quick-switching device, comprising: at least one memory, used for storing instructions; at least one processor, configured to execute the method for switching power supplies with a quick-switching device as claimed in any one of claims 1 - 4 according to the instructions stored in the memory.

10. A readable storage medium, wherein machine-readable instructions are stored in the readable storage medium, and when the machine-readable instructions are executed by a machine, the machine will execute the method for switching power supplies with a quick-switching device as claimed in any one of claims 1 - 4.

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