High-reliability low-loss power-protection rapid dual-power-supply switching system and method based on combination of rapid mechanical switch and current-limiting loop

Abstract

The invention provides a high-reliability low-loss power-protection rapid switching system and method based on combination of a rapid mechanical switch and a current-limiting loop, aiming at solving the problem of rapidly and safely ensuring continuous operation of a load when a power supply sags or is interrupted. Firstly, based on the high-reliability and low-loss principle, a system composition mode of combination of a rapid mechanical switch and a current-limiting loop is established; secondly, a device fast switching method is constructed according to the safety and stability requirements of the system; and finally, simulation verification is carried out on the abnormal switching scene of the current-limiting resistor and the abnormal switching scene of the current-limiting resistor. According to the system and the algorithm provided by the invention, the switching speed can be ensured to be not greater than 20ms, the switching speed is obviously accelerated compared with the conventional mechanical switch ATS, and the on-state loss is small, the manufacturing cost is low, the operating mechanism is simple and the reliability is high compared with the thyristor-based solid-state switch STS. In addition, the device is low in loss and calorific value, free of noise, capable of limiting double-power-supply short circuit and higher in safety and reliability, so that the influence of voltage sag and short-time interruption is avoided, and it is guaranteed that the whole production process is safely and normally carried out.

Description

Technical Field

[0001] The present invention belongs to the field of power electronics technology, and specifically relates to a high-reliability, low-loss, power-saving, fast dual-power switching system and method based on a combination of a fast mechanical switch and a current-limiting circuit. Background Art

[0002] According to statistics from the U.S. Electric Power Research Institute (EPRI), over 90% of power quality issues are caused by voltage sags. Experts generally believe that with the increasing number of electrical devices with sensitive power characteristics, voltage sags have become a critical power quality issue and the greatest challenge to power supply quality in the information society. Downtime of sensitive loads and equipment most susceptible to voltage sags in precision manufacturing processes can force the interruption of subsequent processes. Therefore, a fast-failure solution is implemented at the user equipment level for the most sensitive, critical equipment in the process. In the event of a fault, this solution switches critical process equipment to a backup power source within 20ms, preventing voltage sags and short interruptions and ensuring the smooth operation of the entire production process.

[0003] The common automatic transfer switches (ATS) and static transfer switches (STS) currently on the market are both used for dual power switching to ensure continuous power supply to critical loads. ATS switches are mechanical, using circuit breakers, load disconnects, and other switching actuators. These switching times are relatively long, with motor-driven dual power supplies requiring over 1.5 seconds, and electromagnetic-driven dual power supplies requiring at least 200 milliseconds. Therefore, ATSs are only suitable for applications that don't require extremely fast switching. STS static transfer switches are electronic circuits, consisting of an intelligent control board, thyristors, and circuit breakers. While STSs achieve fast switching through electronic switches, they can be affected by factors such as electromagnetic interference and temperature fluctuations, resulting in low reliability. Furthermore, the power electronics have poor current-carrying capacity, high losses, and high heat generation, making them unsuitable for high-current applications.

[0004] According to the investigation, the inventions of dual power switching devices are concentrated in the field of power electronic devices. A dual power fast switching circuit and switching method thereof (publication / announcement number: CN117543797A), a dual power switching system and switching method (publication / announcement number: CN109474060A), and an automatic power switching device (publication / announcement number: CN217984652U) all proposed fast switching devices based on power electronic devices such as IGBT and MOS, which improved the switching speed of dual power supplies. However, they all have problems such as poor current capacity and high heat generation.

[0005] In response to the problems and shortcomings of existing devices and inventions, this patent proposes a high-reliability, low-loss, power-saving fast switching system and method based on a combination of a fast mechanical switch and a current-limiting circuit. When the main power supply is temporarily reduced or interrupted, it quickly switches to the backup power supply to ensure continuous operation of the load. The system and algorithm proposed in the present invention can ensure that the switching speed is no more than 20ms. Compared with the conventional mechanical switch ATS, the opening and closing speed is significantly faster. Compared with the thyristor-based solid-state switch STS, it has low on-state loss, low cost, simple operating mechanism, and high reliability. Therefore, it is more suitable for voltage sag and short-term interruption of power quality problem management scenarios. In addition, the device has low loss and heat generation, no noise, can limit the short circuit of dual power supplies, and has higher safety and reliability. Summary of the Invention

[0006] To address the deficiencies in the prior art, the present invention provides a high-reliability, low-loss, power-saving, fast dual-power switching system and method based on a combination of a fast mechanical switch and a current-limiting circuit, which solves the problems mentioned in the background technology.

[0007] The present invention adopts the following technical solutions: In a first aspect, the present invention provides a high-reliability, low-loss, power-saving fast switching system based on a combination of a fast mechanical switch and a current-limiting circuit, including a wiring method, a switching method, and key technologies.

[0008] (1) The wiring method mainly includes the first power supply, the second power supply, the working power supply, the switching controller, the section I power supply incoming line circuit breaker D1, the section I power supply incoming line current transformer C1, the section I power supply incoming line fast mechanical switch K1, the section ⅠⅠ power supply incoming line circuit breaker D2, the section ⅠⅠ power supply incoming line current transformer C2, the section ⅠⅠ power supply incoming line fast mechanical switch K2, the current limiting resistor R, the AC contactor J, the uninterruptible power supply (UPS), and the load side circuit breaker D3.

[0009] The first power supply is the normal power supply, which is connected to the upper port of the Section I power supply circuit breaker D1; the second power supply is the backup power supply, which can be drawn from an independent second grid power supply, or connected to a safety power supply, which is connected to the upper port of the Section I power supply circuit breaker D2.

[0010] The voltage sampling signal of the upper port of the section I power incoming line circuit breaker D1 is V1, and the voltage sampling signal of the upper port of the section I I power incoming line circuit breaker D2 is V2. Both voltage sampling signals V1 and V2 are connected to the switching controller.

[0011] The lower port of the power incoming line circuit breaker D1 of section I is connected to the upper port of the fast mechanical switch K1, and the current in this section of the line is sampled through the current transformer C1; the lower port of the power incoming line circuit breaker D2 of section II is connected to the upper port of the fast mechanical switch K2, and the current in this section of the line is sampled through the current transformer C2. Both current sampling signals I1 and I2 are connected to the switching controller.

[0012] The lower port of the fast mechanical switch K1 and the lower port of the fast mechanical switch K2 are connected through a resistor R. One end of the resistor R is connected to the lower port of the fast mechanical switch K1, and the other end is connected to the lower port of the fast mechanical switch K2. The contactor J and the resistor R are connected in parallel, and the contactor J is controlled by the switching controller.

[0013] The lower port of the fast mechanical switch K1 is connected to the upper port of the load-side circuit breaker D3, and the lower port of the load-side circuit breaker D3 is connected to the sensitive and important load to supply power to it.

[0014] After the working power supply is connected to the UPS, it will supply power to the switching controller and maintain power supply for at least 10 minutes.

[0015] To increase closing and opening speed, the fast-switch controller communicates with the switching controller via five optical fiber signals: closing command (ON), opening command (OFF), closing status (CLOSE), opening status (OPEN), and charging status (CHARGE). "ON" and "OFF" receive closing and opening commands, respectively. Upon receiving these commands, the two fiber optic heads convert the optical signals from these commands into electrical signals, which are then transmitted to the control board, outputting the corresponding thyristor trigger signals. "CLOSE" and "OPEN" output the closing and opening status signals, respectively, while "CHARGE" signals the completion of energy storage. This enables real-time monitoring of the fast-switch status, preventing erroneous operation of the fast-switch under abnormal conditions, improving operational reliability, and extending the operation and service life of the fast-switch.

[0016] (2) Switching method During normal operation, circuit breakers D1, D2, and D3 are closed, fast mechanical switch K1 is closed, fast mechanical switch K2 is open, contactor J is disconnected, and the load is powered by power supply 1. The switching controller detects the voltage synchronization status of the working and backup power supplies in real time.

[0017] When the working power supply 1 experiences a voltage sag or short interruption, and the switching controller detects that the voltage of any phase of power supply 1 is lower than the set value, the controller first disconnects the fast mechanical switch K1 and simultaneously sends a command to close the contactor J. After a delay of 10ms, the fast mechanical switch K2 is closed and the load is switched to power supply 2.

[0018] The entire process takes 3ms to detect the voltage anomaly, 3ms to disconnect contactor K1, 10ms to delay, and 3ms to close contactor K2, for a total of 19 ms.

[0019] (3) The key technologies mainly include the setting of working power supply, sampling and switching conditions, resistor current limiting setting and touch screen operation interface.

[0020] Working power supply. The working power supply is equipped with a UPS power supply to supply power to the switching controller. When the working power supply fails, the UPS will maintain power supply for at least 10 minutes.

[0021] Sampling and switching conditions. The status and position nodes of the fast mechanical switch and the opening and closing signals are all fiber-optic signals, making the transmission delay of the opening and closing and status and position signals 0ms, ensuring fast opening and closing. The closing circuits of K1 and K2 are interlocked, that is, K1 and K2 cannot be closed at the same time.

[0022] Resistor current limiting. Due to the high switching speed of the fast mechanical switch, this device incorporates a current-limiting resistor to prevent a short circuit caused by switching on Power Supply 2 directly when the K1 mechanical switch is open but the arc is not extinguished (i.e., Power Supply 1 is not fully disconnected). The current-limiting resistor is connected in parallel with a contactor, which closes under normal operation. During the switching process, the contactor and K1 receive the opening command simultaneously, but the contactor's response time is slow. Power Supply 2 is switched on via the current-limiting resistor, preventing excessive inrush current even when Power Supply 1 is not fully disconnected.

[0023] User interface settings. Set the touch screen as the user interface. Parameters such as voltage limits and switching delays can be set on the interface. Under normal conditions, the device's voltage and current are displayed, and the voltage, current, and waveform at the moment of operation are recorded for historical records. Three switching modes are available for dual power supplies: 1) manual switching; 2) automatic switching (automatically switches back when power source 1 is normal); and 3) automatic switching (does not automatically switch back when power source 1 is normal).

[0024] In a second aspect, the present invention provides a computer-readable storage medium.

[0025] A computer-readable storage medium having a computer program stored thereon, characterized in that when the program is executed by a processor, the program implements the steps in a virtual power plant resource aggregation method for power market grid auxiliary services.

[0026] In a third aspect, the present invention provides a computer device.

[0027] A computer device comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the processor implements the steps in a method for aggregating virtual power plant resources for power market grid auxiliary services.

[0028] The beneficial results of the present invention are: (1) The mechanical fast switch used has a closing and opening speed of about 3ms, which is significantly faster than the conventional mechanical switch ATS. Compared with the thyristor-based solid-state switch STS, it has low on-state loss, low cost, simple operating mechanism and high reliability. Therefore, it is more suitable for voltage sag and short-term interruption power quality problem management scenarios; (2) Adding a current limiting circuit can significantly reduce the impact current when power supply 2 is closed when power supply 1 is not completely disconnected, thereby reducing the impact on the system and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Shown is the main electrical wiring of the system of the embodiment of the invention.

[0030] Figure 2 Shown is a fast mechanical switch interface according to an embodiment of the invention.

[0031] Figure 3 Shown is the main circuit of the simulation model for verifying the effect of the embodiment of the invention.

[0032] Figure 4 Shown is a voltage sag fitting loop of a simulation model according to an embodiment of the invention.

[0033] Figure 5 Shown is the simulation waveform of the normal switching effect of the embodiment of the invention.

[0034] Figure 6 Shown are the simulation results of electrical quantities when the current limiting resistor switches abnormally according to an embodiment of the invention.

[0035] Figure 7 Shown are the simulation results of electrical quantities during abnormal switching with current limiting resistors in an embodiment of the invention. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] Embodiment 1 of the present invention provides a high-reliability, low-loss, power-saving, fast switching system based on a combination of a fast mechanical switch and a current-limiting circuit, characterized by comprising: like Figure 1As shown in the figure, the first power supply is the normal power supply, with a rated voltage of 380V (three-phase) / 50Hz, an equivalent resistance of 5mΩ, an equivalent inductance of 0.17mH, and a phase angle of 0° for power supply 1; the second power supply is the backup power supply, with a rated voltage of 380V (three-phase) / 50Hz, an equivalent resistance of 5mΩ, an equivalent inductance of 0.17mH, and a phase angle of 50° for power supply 2; the working power supply is 220V (single-phase) / 50Hz; circuit breakers D1, D2, and D3 all use 380V 1250A three-pole molded case switches, current transformers C1 and C2 use 400V, 800 / 5A current transformers, and contactors use 380V / 630A three-pole structure, K1 and K2 use fast mechanical switches with a closing and opening speed of 3ms, the resistor uses a 380V / 1Ω wound fixed resistance resistor, and the equivalent resistance of the load is 1Ω.

[0038] The first power supply is connected to the upper port of the section I power incoming circuit breaker D1; the second power supply is the backup power supply, which can be drawn from an independent second grid power supply, or connected to a safety power supply, and connected to the upper port of the section I I power incoming circuit breaker D2; the voltage sampling signal of the upper port of the section I power incoming circuit breaker D1 is V1, and the voltage sampling signal of the upper port of the section I I power incoming circuit breaker D2 is V2. Both voltage sampling signals V1 and V2 are connected to the switching controller.

[0039] The first power source is the normal power supply and is connected to the upper port of the Section I power incoming circuit breaker D1. The second power source is the backup power source and can be drawn from an independent second grid power source or a safety power source and is connected to the upper port of the Section I I power incoming circuit breaker D2. The voltage sampling signal at the upper port of the Section I power incoming circuit breaker D1 is V1, and the voltage sampling signal at the upper port of the Section I I power incoming circuit breaker D2 is V2. Both voltage sampling signals, V1 and V2, are connected to the switching controller.

[0040] The lower port of the power incoming line breaker D1 of section I is connected to the upper port of the fast mechanical switch K1. The current in this section of the line is sampled by the current transformer C1. The lower port of the power incoming line breaker D2 of section II is connected to the upper port of the fast mechanical switch K2. The current in this section of the line is sampled by the current transformer C2. Both current sampling signals I1 and I2 are connected to the switching controller. The lower port of the fast mechanical switch K1 is connected to the lower port of the fast mechanical switch K2 through a resistor R. One end of the resistor R is connected to the lower port of the fast mechanical switch K1, and the other end is connected to the lower port of the fast mechanical switch K2. The contactor J and the resistor R are connected in parallel, and the contactor J is controlled by the switching controller; The lower port of the fast mechanical switch K1 and the upper port of the load-side circuit breaker D3, and the lower port of the load-side circuit breaker D3 and the sensitive and important loads are supplied with power. Embodiment 2 of the present invention provides a high reliability, low loss, power-saving, fast switching method simulation based on a combination of a fast mechanical switch and a current limiting circuit. Figure 3 As shown, a corresponding working condition simulation model was built in PSCAD software. The simulation condition is: at the moment of 1s, the voltage of power supply 1 temporarily drops from 1.0pu to 0.2pu.

[0041] (1) Normal switching simulation.

[0042] During normal operation, K1 is closed, K2 is open, and J is disconnected. The load is powered by Power Supply 1, and the switch controller monitors the voltage synchronization of the working and backup power supplies in real time. Power Supply 1 experiences a 0.2 pu voltage sag at 1000ms. At 1003ms, a command is issued to open the fast mechanical switch K1. At 1006ms, K1 fully opens, and the controller commands J to close. At 1016ms, the controller commands K2 to close, and at 1019ms, K2 fully closes.

[0043] like Figure 5 As shown, V1 is the voltage waveform of Power Supply 1, V2 is the voltage waveform of Power Supply 2, VL is the voltage waveform on the load side, I1 is the current waveform of Power Supply 1, I2 is the current waveform of Power Supply 2, and IL is the voltage waveform on the load side. As can be seen from the waveforms, after the voltage sag of Power Supply 1, the load side voltage drops by 3% (lasting 3ms). The high-reliability, low-loss, power-saving fast switching device actuates, quickly disconnecting Power Supply 1 (lasting 3ms). After a 10ms delay, the K2 closing command is issued. 3ms later, Power Supply 2 closes, restoring normal load power. The total load side voltage drop and interruption duration is 3+3+10+3=19ms, slightly less than one power frequency cycle (20ms). During the switching process, Power Supply 2 is not operational until the current in Power Supply 1 completely disappears, thus avoiding the need for parallel operation of two power supplies.

[0044] (2) Simulation of current limiting effect during abnormal switching During normal operation, K1 is closed, K2 is open, and J1 is disconnected. The load is powered by Power Supply 1, and the switch controller monitors the voltage synchronization status of the working and backup power supplies in real time. Power Supply 1 experiences a 0.2 pu voltage sag at 1000ms. At 1003ms, a command is issued to open the fast mechanical switch K1, but the arc is not extinguished, preventing Power Supply 1 from being fully disconnected. At 1006ms, a command is issued to close J1, and at 1016ms, a command is issued to close the fast mechanical switch K2. At 1019ms, the fast mechanical switch K2 fully closes. At 1026ms, the arc on the fast mechanical switch K1 is completely extinguished, completely disconnecting Power Supply 1.

[0045] As attached Figure 6As shown in the figure, the simulation results without current limiting resistor (R=0Ω) show that due to the phase difference between power sources 1 and 2 and the small internal resistance of the power sources, a large inrush current is generated after the fast mechanical switch K2 is closed, with a peak value of about 4kA, which can easily damage the equipment or cause the switch to trip.

[0046] As attached Figure 7 As shown in the figure, simulation results with a current-limiting resistor (R = 1Ω) show that after adding the resistor, although the inrush current still exists at the moment the fast mechanical switch K2 is closed, the value is significantly reduced, with the peak value dropping from 4kA to 1.8kA, a 55% decrease. This avoids the risks of equipment damage and switch tripping, and achieves the current limiting effect. Different resistor values ​​can be selected according to actual site conditions and current limiting requirements.

Claims

1. The high-reliability, low-loss, power-saving fast switching system based on the combination of fast mechanical switches and current-limiting circuits consists of the first power supply, the second power supply, the working power supply, the switching controller, the section I power incoming line circuit breaker D1, the section I power incoming line current transformer C1, the section I power incoming line fast mechanical switch K1, the section ⅠⅠ power incoming line circuit breaker D2, the section ⅠⅠ power incoming line current transformer C2, the section ⅠⅠ power incoming line fast mechanical switch K2, the current limiting resistor R, the AC contactor J, the uninterruptible power supply (UPS), and the load-side circuit breaker D3.

2. Due to the high switching speed of the fast mechanical switch, this device incorporates a current-limiting resistor to prevent a short circuit caused by switching on Power Supply 2 directly when the K1 mechanical switch is open but the arc is not extinguished (i.e., Power Supply 1 is not fully disconnected). This current-limiting resistor is connected in parallel with a contactor, which is closed under normal operation. During the switching process, the contactor and K1 receive the opening command simultaneously, but the contactor's response time is slow. Power Supply 2 is switched on via the current-limiting resistor, preventing excessive inrush current even if Power Supply 1 is not fully disconnected.

3. To increase opening and closing speed, the fast switch controller communicates with the switching controller via five fiber optic signals: closing command (ON), opening command (OFF), closing status (CLOSE), opening status (OPEN), and charging status (CHARGE). "ON" and "OFF" receive closing and opening commands, respectively. Upon receiving these commands, the two fiber optic heads convert the optical signals into electrical signals, transmit them to the control board, and output the corresponding thyristor trigger signals. "CLOSE" and "OPEN" output the switch closing and opening status signals, respectively, while "CHARGE" indicates the completion of energy storage. This enables real-time monitoring of the fast switch status, preventing incorrect operation of the fast switch under abnormal conditions, improving operational reliability, and extending the operation and service life of the fast switch. The status position node and opening and closing signals of the fast mechanical switch are all fiber optic signals, resulting in a zero-ms transmission delay for the opening and closing and status position signals, ensuring fast opening and closing.

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