be able to acquire all power system data every 10 seconds. The SEBM system could estimate the state of the system every minute. The RSCS could reset the relay system every five minutes. The IMPU system could estimate all relay parameters every 15 minutes. The SDPU system could track the system trends and estimate all load and generation parameters every 30 minutes. It is believed that such an implementation is sufficient for the presently envisioned space station. Connections to a terrestrial based ground controller (GC) are also shown in Fig. 3. It is expected that all experiment scheduling will be performed at ground control, that all SCADA functions will be monitored by ground control and that all instrumentation models will be monitored by ground control. Software Implementation The SCADA functions have been implemented on an IBM PC/AT interfaced with a Harris Corporation remote terminal unit (RTU). The RTU is being connected to the Auburn University energy conversion test facility (AUECTF). This facility includes a configurable photovoltaic array and programmable motor/generator set to simulate any satellite power source, a configurable distribution system to simulate any satellite power system distribution bus and configurable static and dynamic loads. Power system conditioning equipment is available to provide specified terminal conditions (e.g. power quality). If large or more elaborate power distribution systems have to be simulated, a harmonic power flow [9] and a power system dynamic simulator [10-14] are available on either a personal computer or a DEC VAX. These simulations can be executed on a separate personal computer without impact on the control system by simulating the RTU interface with a single RS-232 connection. The harmonic power flow simulates the steady-state operating conditions for a single-phase or multi-phase AC power system. The presence of non-linear conversion devices introduces nonsinusoidal currents. The nonsinusoidal currents can be written in terms of a fundamental and harmonic components (Fourier analysis). The harmonic currents and voltages are predicted by a modified Newton-Raphson numerical algorithm. The power system dynamic simulator simulates the transient response of any power system composed of linear or non-linear components. The state variable representation of the system is assembled and solved using a clamped state variable algorithm. Load and generation management control strategies are being evaluated through the power system dynamic simulator. An automatic generation control algorithm has been implemented to balance the load and generation demands for the power system. The AGC algorithm is a modified differential proportional-integral-derivative (PID) controller. A security assessment package [15] has been written to analyze the power system for all single point failures (first order contingencies). This package determines if the system will survive the contingency. The results are saved as a function of the configuration and the failure. This information can then be used to determine the mode of the power system based on present system conditions for system monitoring and alarm processing. If the system mode is initially diagnosed as normal, then the security assessment package can be run with real-time data to determine if the system has actually entered the alert mode. If the mode is alert or emergency, then an alarm should be issued for operator or ground control interaction. A state estimation package [15-16], including observability and bad measurement
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