A method for controlling multi-stage centrifugal compressors is provided. The method includes, for each stage of the compressor, defining a Mach ratio and impeller diameter, calculating a minimum required motor drive frequency to operate free from surge conditions for a current head factor and flow reduction device position, and adjusting the flow reduction device position while maintaining an actual motor drive frequency at a acceptable level to achieve a leaving chilled water temperature set point. The method also includes measuring a suction pressure and a discharge pressure and calculating a saturated suction temperature and a saturated discharge temperature for each stage of the compressor. The method further includes calculating an actual minimum motor drive frequency that is the greater of a first actual minimum motor drive frequency and a second actual minimum motor drive frequency associated with a first compressor stage and a second compressor stage of the compressor, respectively.

Disclosed is a system for controlling a water turbine generator for waterworks, which monitors and controls a plurality of water turbine generators, provided in a water pipe, for waterworks in real time to integratedly operate the water turbine generators, contributes to stably generate and secure power, and increases an efficiency of the water turbine generators through integrated management. The system for controlling a water turbine generator for waterworks includes an integration control system configured to establish a power generation driving plan, based on a target amount of energy collected by a plurality of water turbine generators and a driving range of each of the plurality of water turbine generators, and a power generation unit configured to generate power through generation of power by a water turbine according to control based on the power generation driving plan, measure an amount of generated power, an amount and a pressure of water flowing into the plurality of water turbine generators, and an amount and a pressure of water flowing out from the plurality of water turbine generators, and supply a result of the measurement to the integration control system.

Control device for hydraulic turbines configured to adjust the resistant torque provided by the generator to the movement of the impeller of an hydraulic turbine so that a stable pressure is set at the inlet (Pi) and at the outlet (Po) regardless of the circulating flow rate (Q), and to adjust the electrical energy produced by the turbine to achieve the desired hydraulic behavior, the device comprising a controller and a power device; wherein said controller is connected to a pressure detector at the inlet (Pi) and at the outlet (Po) and to a flow-meter for obtaining the circulating flow rate (Q), as well as to a power sensor for measuring the power of the turbine; all this, in such a way that the controller acts on the power device for causing the application of the braking torque necessary to maintain a stable set-point value on the turbine.

A method for controlling multi-stage centrifugal compressors is provided. It allows an optimization of compressor head and efficiency at each compression stage and is specifically valuable at reduced compressor flow.

An example system comprises an enclosure submerged in a body of water. The system also comprises an intake port disposed along a periphery of the enclosure to transport water into the enclosure. The system also includes a turbine generator disposed inside the enclosure and coupled to the intake port to receive the water entering the enclosure through the intake port. The system also comprises a water storage tank coupled to the turbine generator to receive the water flowing out of the turbine generator. The system also comprises a pump coupled to the water storage tank to pump the water out of the water storage tank. The system also comprises a controller to control flow of the water into the enclosure by operating the intake port and to control flow of the water out of the enclosure by operating the pump.

An example system comprises an enclosure submerged in a body of water. The system also comprises an intake port disposed along a periphery of the enclosure to transport water into the enclosure. The system also includes a turbine generator disposed inside the enclosure and coupled to the intake port to receive the water entering the enclosure through the intake port. The system also comprises a water storage tank coupled to the turbine generator to receive the water flowing out of the turbine generator. The system also comprises a pump coupled to the water storage tank to pump the water out of the water storage tank. The system also comprises a controller to control flow of the water into the enclosure by operating the intake port and to control flow of the water out of the enclosure by operating the pump.