Microprocessor-Based Power Cable Carrier Control (MPC Exp 3 )

摘要

The MPC exp 3 was developed to control the orientation of individual solar energy collectors in a distributed field. The system was to be reliable, yet its total installed cost had to be kept to a minimum. Both goals were accomplished by transmitting a carrier signal over the power cables that lead to the field, usimg frequency shift keying (FSK) and Manchester data coding. Its operation is simple. A microprocessor at central control solves a sun-position equation. The microprocessor then transmits its results to the collector via carrier signal imposed on the power cable to the collector's drive mechanism. At the drive mechanism, an inclinometer mounted on each collector determines the orientation of its collector. There a system compares this data with the information gathered by the inclinometer, determines any discrepancies, and makes the necessary adjustments to the collector by actuating the drive mechanism until it detects a null position (that is, until the information coming from the inclinometer matches the results of the sun-position equation). Each row, or every other row, or each 2-axis tracking collector in a field can thus be controlled. Each collector control receives updated information from the central control every 0.75 or 1.5 seconds, depending on whether one or two separate commands are required. The MPC exp 3 system is rugged and, since it uses the power cables as transmission lines, it obviates the need for separate and expensive control wiring to the field. This approach also enables the manufacturer to control quality at the factory. The combination of mechanical inclinometer and microprocessor data frees the system from light-sensitive devices that could be confused by clouds or other environmental uncertainties. These qualities improve system reliability. In addition, the money saved in the eliminated control wiring and the necessarily slow and expensive checkout required in former systems can pay for an installed MPC exp 3 system. (ERA citation 07:043058)