Abstract: A method and apparatus for surge prevention control for multistage compressors with at least two stages, at least one flow measuring device, and one overall surge recycle valve is disclosed. Furthermore, a method of accurate calculation of surge limit line for overall multistage compressor using one available flow measuring device is also disclosed. The method of surge prevention calculates multistage compressor's surge limit line as a product of individual stages surge limit lines that differs from those revealed in the prior art. This method allows accurate calculation of the distance of operating point to surge limit line that takes in account surge lines of all stages and allows reliable surge prevention control.

Abstract: A method and apparatus for surge prevention control for multistage compressors with at least two stages, at least one flow measuring device, and one overall surge recycle valve is disclosed. Furthermore, a method of accurate calculation of surge limit line for overall multistage compressor using one available flow measuring device is also disclosed. The method of surge prevention calculates multistage compressor's surge limit line as a product of individual stages surge limit lines that differs from those revealed in the prior art. This method allows accurate calculation of the distance of operating point to surge limit line that takes in account surge lines of all stages and allows reliable surge prevention control.

Abstract: A method and apparatus of coordinated voltage control for electric power systems with at least two substations and at least one load, a method of controlling distribution of reactive power between substations within a power system of similar parameters, and a method of reduction of interaction between voltage control modules in the said power system are disclosed. The purpose of coordinated control is to maintain acceptable voltage with minimal deviation from the set point across all elements of the power system. Disclosed coordinated control is accomplished via each substation's transformers equipped with on load tap changers (OLTC) and electrical generators Automatic Voltage Regulators (AVR) using proportional-integral-derivative control embedded in coordinated master controllers.