Active Filter Protection Measures for Stable Operation
Active filters are a new type of power electronic device. In practical applications, to ensure that the compensation current of an active filter quickly tracks changes in the command current, devices with a high switching frequency must be used. Currently, the power electronic device used in the main circuit of small and medium-capacity active filters is generally IGBTs. For large-capacity active filters, to resolve the conflict between switching capacity and switching speed, multiple main circuits can be used to achieve a larger compensation capacity. Active filters use IGBTs as the main circuit power switching device. Due to their high operating frequency, they are very effective in compensating for high-order harmonics. However, when operating at higher frequencies, their losses increase, reducing the efficiency of the active filter. The operation of power electronic switching devices requires peripheral circuit technologies such as base drive circuits, snubber circuits, and overcurrent and overvoltage protection circuits. The base drive circuit controls the operating characteristics of the switching transistor, while the snubber and protection circuits prevent damage to the power electronic device.
Although power electronic devices and technologies have made significant advances, the problem of tube burnout still occurs frequently, primarily due to the limited application of power electronic device drivers and protection.
Furthermore, active power filters often encounter various operating conditions during operation: overload or load short-circuit, arm shoot-through, overvoltage caused by excessive di/dt when shutting down high currents, excessive voltage during shutdown, voltage slope, poor heat dissipation, or other faults that cause device overheating.
These can affect the normal operation of the device, leading to performance degradation, even malfunction and damage to components. In severe cases, they can also affect the normal operation of other surrounding equipment. Therefore, to ensure safe and reliable operation, active power filters must be equipped with overcurrent protection, arm shoot-through protection, overvoltage protection, di/dt protection, du/dt protection, and overtemperature protection circuits to prevent overload and damage and ensure normal operation.