Research On Distributed Intelligent Reactive Power Compensation System

With the continuous expansion of the electricity scale, a large number of low power factor loads are connected to the grid, causing serious power quality problems. To achieve safe and stable operation of the power grid, it’s necessary to balance the load reactive power; reactive power compensation is a key technology to achieve this goal. Low-voltage reactive power compensation device which based on shunt capacitor is fit for the compensation of the widely used inductive reactive load, and it is currently the most widely used reactive compensation device. In this article, with discussion of the development trend of low-voltage reactive power compensation device, the design of a distributed intelligent reactive compensation system and related technologies are studied.Firstly, the design of intelligent reactive power compensation module controller is completed. Combined with intelligent function requirements of the module controller, hardware design is completed by applying the STM32F103RDT6which based on Cortex-M3processor as the control core. The design of composite switch which is the key component in the controller is discussed in detail, and in this way, the capacitor can be switched safely. In software design,μc/os-Ⅱ operating system is transplanted in the main chip and STM32firmware library is applied. The software is divided into several tasks according to different functions; this makes the software development and upgrade easier.Secondly, in order to meet the user site requirements, such as capacity expansion of reactive power compensation, a distributed intelligent reactive power compensation system is designed. The system is based on multiple intelligent reactive compensation modules, a new multi-module networking and compensation capacity expansion operation strategy is promoted, to realize the coordinated operation of multiple modules, and compensate verifying reactive power; reactive power compensation strategy employed is compatible with different capacities. Successful application in the industrial site verifies good performance of the system.Finally, a hybrid compensation system which is composed of shunt active power filter (APF) and distributed reactive power compensation system is promoted. In many industrial sites, APF and shunt capacitor or LC branch are operating in parallel. For this case, system characteristics when APF and these two passive reactive compensation devices operating in parallel is studied; since the system which is composed of APF and parallel capacitor is instable when source current is detected to control APF, a new method in which both the source current and grid voltage are detected to control the APF is introduced. On this basis, a hybrid compensation system which is composed of APF and distributed reactive power compensation is proposed; the hybrid compensation system combines both the advantages of the active device and the passive compensation device i.e., high compensation precision, harmonic suppression function, low-cost. The above contents are all verified by simulation results.