On any electrical system, the introduction of devices with dynamic load characteristics or larger motor loads will give rise to situations where the local system power factor will fall to unacceptable levels. If these levels are maintained at a low enough level, for a long enough time, the electrical utility will usually apply a punitive tariff for the reactive power consumed. Although most residential and small commercial electrical demand meters do not measure reactive power, the utility does not want their customers contributing to low power factors, which can lead to voltage sags and other undesirable issues. When a system’s power factor shifts from unity due to a transient loading condition, it can generally be corrected by adding a capacitive component equal and opposite to that by which it has shifted from unity.
This project will involve the creation of a static VAR compensator (SVC) to ensure that the local system power factor is maintained at near unity. Control elements, protective elements and monitoring devices will be implemented in this project. The project should be created in a modular fashion. A SVC handling a lower voltage level (120V) will be designed and implemented. Once this SVC has been created, larger more robust SVC’s can be built accordingly. The current design size that we will be working with is that which would be suitable for maintaining the power factor an a standard 120V, 15A circuit. Attempts will be made to minimize harmonic contributions to the local power system through various techniques including predetermined times of capacitor inclusion onto the system.
Power electronic controllers (thyristors) will be implemented to control the addition of inductive and capacitive components on the system. An MSP430 will be used to determine the gating signals required by the thyristors for the appropriate output voltage levels. An AD536A will be incorporated for converting ac current and voltage levels to a dc value.
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