First, the series technology of high-power power electronic devices
With the rapid development of dynamic reactive power compensation and the trend toward high voltage and high power, the requirements for power electronic devices are gradually developing toward high voltage and large capacity. As power electronic devices are constrained by the degree of development of technology and technology, Therefore, it is necessary to use in series in a high voltage circuit. In the series application of the device, since the static volt-ampere characteristics and dynamic switching parameters of the various components are different, the voltage distribution between the components will be uneven, resulting in an accident that damages the device. Therefore, the voltage equalization measure must be used in use. The specific requirements can be divided into first-time use of components with consistent characteristics to be connected in series. Before installation, according to the test parameters provided by the manufacturer, the reverse recovery charge of the semiconductor device is basically the same. In addition, with the dynamic voltage equalization circuit, since the parameters of the components cannot be completely consistent, even if the same control signal is added to the above, it is impossible to turn on and off at the same time, thereby causing overvoltage of the device, and the device is connected in parallel to absorb the circuit. The voltage equalization reduces these overvoltages. The working principle is to use the property that the voltage across the capacitor can not be abrupt to slow down the voltage change speed of the power electronic device and realize dynamic voltage equalization. The resistor is used to suppress the oscillation of the circuit and limit the discharge current of the capacitor. In addition, it functions as an overvoltage protection. The requirement for the drive is that the drive signals of the series devices must be synchronized, and the leading edge of the trigger is steep and the amplitude is high enough to cause the device to turn on and off at the same time. In short, the series reliability of power electronic devices directly affects the reliability of the equipment, and directly affects the development speed of the entire industry and the maturity of the equipment.

Second, fully enclosed water cooling
 In the power system, the power electronic device plays a decisive role in the flexible transmission. Its reliability is directly related to the reliable operation of the whole set of equipment. The power electronic device is very sensitive to temperature, the temperature of the device is increased, and the various components of the power electronic device. The parameters will also deteriorate accordingly, and even cause damage to the device. Therefore, the heat dissipation problem of power electronic devices is also a key technology. Since flexible transmission is mainly in the case of high voltage, it is necessary to consider the problem of withstand voltage insulation and heat dissipation. The cooling methods that have appeared in recent years mainly include natural cooling and water cooling. Among them, water cooling is the most direct and effective way to dissipate heat. Its main features are high heat dissipation efficiency, complete control and protection, and no noise. The entire cooling unit is a closed circulation line. The fully enclosed water cooling device can provide a good development and progress basis for high-voltage, large-capacity flexible power transmission equipment.

Third, on the same section of the busbar multiple SVC parallel operation problem
 In the use of SVC, there are multiple SVCs running in parallel on the same busbar. Avoiding the simultaneous operation of multiple SVCs causes the resonance of the system to become the primary problem. Since the response time of each SVC is not necessarily the same, even products produced by the same company may not be guaranteed, so overshoot may occur and the equipment and system may be unstable. Multiple SVC coordinated control technologies can solve this problem. All control commands of SVC are controlled by one main controller, and a single operation can be realized according to user needs.