This paper deals with the modeling and control of the NEREIDA wave generation power plant installed in Mutriku, Spain. This kind of Oscillating Water Column (OWC) plants usually employ a Wells ...turbine coupled to a Doubly Fed Induction Generator (DFIG). The stalling behavior of the Wells turbine limits the generated power. In this context, a sliding mode rotational speed control is proposed to help avoiding this phenomenon. This will regulate the speed by means of the Rotor Side Converter (RSC) of the Back-to-Back converter governing the generator. The results of the comparative study show that the proposed control provides a higher generated power compared to the uncontrolled case.
An application of contra-rotating rotors, consisting of front and rear rotors rotating in the opposite direction each other, has been proposed against a demand for developing higher specific speed ...axial flow pump with more compact structure, higher efficiency and better cavitation performance. Air/water two-phase flow performance of contra-rotating pump has to be, also, investigated as axial flow pumps are used for standby operations of air-lock and air/water mixing discharge to prevent floods. In the present paper, experimental results on air/water two-phase flow performance of test pump of contra-rotating rotors (RR1 Type) are shown and compared with those of conventional axial flow pump, consisting of a front rotor and a rear stator. Effects of changes of rear rotor rotational speed, which is an advantage of contra-rotating axial flow pump, on two-phase flow performance of RR1 type are discussed. It is shown that air/water two-phase flow performance of contra-rotating axial flow pump is capable to be improved by this control procedure for rear rotor rotational speed.
Motor spindle (three-phase asynchronous AC motor) is one of important components of Computer Numerical Control (CNC) Printed Circuit Board (PCB) milling and drilling machine. This motor can engrave ...copper layer to form circuit paths and drill holes to fit electronic components of the circuit. To perform engraving process, the speed of the spindle motor should be regulated according to PCB material used. This paper discusses development of Field Programmable Gate Array (FPGA)-based three-phase spindle motor speed control module. This module uses fixed Voltage/Frequency (V/F) control method that is implemented by Sinusoidal Pulse Width Modulation (SPWM) technique so that maximum torque of the motor can be kept constant and harmonic signals can be suppressed. This module consists of a digital controller implemented in an FPGA and a three-phase, full-bridge inverter circuit. The FPGA controller generates digital SPWM signals sent to the inverter. This circuit converts DC voltage to three-phase AC voltage with certain frequency according to the input. This module has a capability to control the rotational speed of the spindle motor in the range of 14000-28000 RPM. This corresponds to input frequencies in the range of 250-500 Hz with fixed V/F and Speed/Frequency (N/F) ratio. The acceleration and deceleration are accomplished using a ramp function so that the starting torque of the motor is not reduced at high input frequencies.
An improved Narendra model reference adaptive control (MRAC) scheme is proposed to research one variable displacement pump driving four hydraulic variable displacement motors. This approach not only ...ensures the underdamped and unstable system be global uniform asymptotic stability, but also has good robustness in these aspects of modeling uncertainty, pressure fluctuation of constant pressure network, and disturbance from external load, which also upgrades the rapidity of system response so as to make controlled system with nicer dynamic quality. The scheme of one pump driving four motors can meet the demand on off-road mobility of engineering vehicles and armored cars. A proof of stability about improved Narendra MRAC scheme is also given.
The hybrid offshore renewable energy conversion system (HORECS) consists of offshore wind, wave and tidal power generations. Its output power fluctuates, which may cause power quality problems. A ...coordinated control method is presented in this paper to smooth the short-term power fluctuations. The tidal generation system is used to compensate the wind and wave power fluctuations. According to the variations of the tidal speed, the proposed method is divided into two stages. When the tidal speed is larger than the cut-in speed, the output fluctuations are smoothed by the coordinated rotational speed control and pitch control of the tidal generator. When the tidal speed is smaller than the cut-in speed, the tidal generator can be operated as a fly-wheel energy storage, and the kinetic energy of the tidal generator is used to compensate the power fluctuations. Simulations are performed to illustrate the control performance.
