A Research Of Automatic Controlling Device Of Reactive Power Compensation For Distribution Network

With the contradiction of power supply and demand deepening and the power supply quality requirement increasing,the reactive power compensation problem becomes an important project in the power system. This project designs reactive power automatic controller which casts or cuts off parallel capacitors in order to achieve reactive power compensation, ensure qualified power factor.The principle of the design is that we judge by both power factor and voltage to cast or cut capacitors. according to the principle of voltage to be qualified, reactive power to be balance and controlling action to be least, when voltage is in the quality limit, we raise power factor and degrade electric power loss, when power factor is beyond assigned value,we cast in capacitors that are working, when power factor is lower assigned value, we cut off capacitors that are idle. When voltage is beyond assigned voltage,we cut off capacitors that are working,when voltage is lower assigned voltage, we cast in capacitors that are idle. To solve existing automatic controllers' defects,we improve on software, adopt optimize contolling diagram, implement force cast and force cut, overcome controllers' defects, advance compensation accuracy and velocity, and realize cycle run and prolonge the life span of the capacitor set. We take several anti-interference measures in electro-magnet compatible design from hardware design and the software design.CS5460A is the core chip in the design so that advance examination accuracy greatly . And powerful AT89C52 is the single-chip computer so that advance agility and reliability. CS5460A examines some parameters such as voltage,current,active power relating to power factor and then input it into master. Master control unit calculates power factor,then compares it with power factor lower limit and upper limit, finally makes the decision of casting in or cuting off capacitors.The design provides friendly and easy operating interface. The control apparatus can display the condition of voltage,current,power factor and capacitors operation, and have the function of warning and locking. Moreover users can set some parameters such as power factor upper limit, lower limit and so on. In this system, we use RS-485 bus standard realizing serial data communications of PC and single-chip computer. The PC can monitor the condition of power factor, voltage and so on.