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In many important occasions, the electrical reliability of the load is extremely important. To improve the power reliability under load, typical power supply systems employ dual-power supply configurations, such as two mains power sources, or one mains power source combined with a UPS. However, a more reliable method is to use dual UPS power supply; this approach is employed by computer systems in many factories and enterprises, comprehensive commercial IDC facilities, bank branches, as well as many critical loads in the telecommunications, mobile communication, and power sectors. For dual-power supply systems, the way in which switching is carried out safely, quickly, and efficiently has a direct impact on the reliability of power supply to the loads. Especially since many devices have very strict requirements regarding the duration of power outages, the common solution is to install ATS or STS dual-power switches on the load side. However, market requirements dictate that the power outage duration should not exceed 10 ms, with some even requiring 5 ms. Under such conditions, conventional ATS devices with mechanical contacts are not capable of meeting these demands; their capabilities in terms of overload protection for the input voltage, as well as protection against high/low input voltages, high/low output voltages, overtemperature, and overload, are far from sufficient. Drawing on years of field experience in power switching, Nanjing Guogao Electrical Automation Co., Ltd. has developed the GSS series of static switches, which are available for both single-phase and three-phase systems. As shown in Figure 1, this static switch is capable of dynamically monitoring the power supply quality of both the primary and backup AC power grids. In cases where the main power source experiences fluctuations, outages, low voltage, or overvoltage, the static switch switches to the backup power source to supply the load. The entire switching process is seamless and fast. When a fault occurs in a critical component of the system or an IGBT, it automatically switches to the bypass mode and triggers an alarm. 1. By changing the previous design approach, which relied solely on IGBT control for switching or did not take into account the system’s operation in the event of IGBT failure, a new system architecture was developed that utilizes static switching powered supplies. Advanced hardware, combined with optimized control software, enables the achievement of high technical performance standards. 2. Voltage drop detection is accomplished through a combination of software and hardware, allowing for fast and accurate determination of both the acceptable and unacceptable voltage thresholds. This approach represents a significant improvement over traditional detection methods; moreover, the system has a low cost, making it highly suitable for rapid and accurate identification of AC signals in power-frequency environments. 3. Intelligent switching control module: It works in conjunction with the IGBT control module to regulate the conduction of IGBTs, and it dynamically collects parameters related to input and output. The hardware is reliable, with comprehensive failure prevention measures. The software, through its various operating mode architectures, automatically identifies and controls the system status – it identifies the situation before switching occurs and performs closed-loop monitoring after the switch is made. As a result, the system features good real-time performance and high stability. 4. Redundant bypass control technology: The reliability of a system is often determined by its failure mitigation mechanisms. This switch features powerful diagnostic capabilities; by quickly diagnosing issues in the circuit, especially when the IGBT cannot be turned off or closed, it enables the use of a bypass system to ensure a reliable power supply, thereby **improving the system’s reliability**. Starting from the need for rapid switching between two power sources, it has been redesigned in accordance with industry standards on the demand side. It features high levels of system intelligence and compatibility, excellent product stability, as well as the ability to quickly detect voltage drops and enable rapid switching. It can provide protection against overvoltage, undervoltage in the input voltage, as well as against overvoltage, undervoltage, overheating, and overload in the output. It is suitable for various system configurations such as those with one mains supply and one UPS, two mains supplies, or two UPS units. Additionally, the product offers advantages such as small size, flexible installation, and long-term reliability, and it holds great value in terms of environmental protection. The purpose of this three-phase static switching switch is achieved through the following system modules: an AC flexible switching cabinet, which is divided into several sections – A for rapid voltage loss detection, B for intelligent switching control, and C for intelligent control of high-power IGBTs. Its features include: A rapid voltage detection mechanism that collects the AC voltage using software to calculate the normal voltage level; at the same time, an AC hardware comparator is used to monitor the AC signal. When the AC signal falls below a preset threshold, the hardware comparator triggers the system to carry out a software comparison, thereby accelerating the detection of voltage loss. This process is much faster than relying solely on software-based calculations; normal voltage loss can be detected in about 2 milliseconds. Once a voltage loss is correctly identified, the result is sent to the intelligent switching control module. B is the intelligent switching control module, which records the operating parameters of the main power supply and the backup power supply to determine the current operating condition as well as in cases of faults requiring bypassing. Module A is responsible for acquiring AC signals and detecting voltage loss signals; it controls the IGBTs in area C to turn them off or on. In the event of an IGBT failure, it automatically activates the bypass circuit and sends out signals indicating device abnormalities. C, the IGBT intelligent control module, is used to receive commands from the intelligent switching control module, to carry out reliable switching operations, and to feedback the module’s operating status to the switching control module in a timely manner. It also alerts the intelligent switching control module whenever an abnormality occurs in the module. The working process is as follows: As shown in Figure 21 below, under normal power supply conditions, both the main power source and the backup power source are within the acceptable voltage range. At this time, K1\K2\Q1\K5 are closed while Q2\K3\K4 are open, and the load is powered by the main power source. When there is overvoltage, undervoltage, overfrequency, or underfrequency in the main power source, but the backup power source is functioning properly, the voltage detection module quickly identifies the issue, opens Q1 and closes Q2, then after a delay it opens K1, thereby completing one cycle of proper switching control. The control of Q1 and Q2 is accomplished through an IGBT intelligent control module in conjunction with a switching control module. 2. When the normal power supply is restored, after a reliable delay, the main control module B issues a command to turn off Q2 and turn on Q1, thereby completing the automatic restoration of power supply. 3. When a fault is detected in either Q1 or Q2, the control module switches to activate the bypass circuit K3 or K4 to maintain normal power supply and issue audible and visual alarms; whenever any of the circuits K1\K2\K3\K4\K5 is in an abnormal state, the system detects this and triggers an alarm. Figure 2 shows the AC static switch, which is suitable for capacitive and resistive loads in data centers and control systems, but not for inductive loads at the input side of motors or transformers. This static switch is capable of dynamically monitoring the power quality of both the primary and backup AC power supplies. In cases where the main power source experiences fluctuations, outages, low voltage, or overvoltage, it automatically switches to the backup power supply to supply power to the load; this switching process takes place in a static manner. When faults occur in key components of the system or in the IGBTs, it automatically switches to the bypass circuit and triggers an alarm. It features protection functions against excessive or insufficient input voltage, as well as excessive or insufficient output voltage, overtemperature, and overload. With support for the standard RS485-MODBUS protocol, it offers high levels of intelligence and compatibility. The product is highly stable, and it can effectively detect rapid drops in input voltage. It is suitable for various system configurations, such as those with one mains power supply and one UPS, or two mains power supplies with two UPS units. Additionally, it has advantages such as a small size, flexible installation, and long-term reliability, making it ideal for use in data centers and control systems as an important component for dual-power supply switching.