Sina Hamzehlouia

A Hydraulic Wind Power Transfer System: Operation and Modeling

Conventional wind power plants employ a variable speed gearbox to run a generator housed on top of a tower. A new topology can remove some of the weight from the tower and centralize the wind power generation. This new topology uses a hydraulic wind power transfer system to connect several wind turbines to the generation unit. This paper demonstrates a mathematical modeling of this wind power transfer technology and its dynamic behavior. The flow response, angular velocity, and pressure of the system obtained from the mathematical model are compared with test results to demonstrate the accuracy of the mathematical model. Several speed-step responses of the system obtained from the mathematical model demonstrate a close agreement with the results from the prototype of the hydraulic wind power transfer unit.

Modeling of gearless wind power transfer

In this paper, a gearless hydraulic wind energy harvesting and transfer system is mathematically modeled and verified by experimental results. The energy is harvested by a low speed-high torque wind turbine connected to a high displacement hydraulic pump, which is connected to hydraulic motors. The quality of transferred power from the wind turbine to the generator is important to maintaining the systems power balance, and frequency droop control in grid-connected applications, and to ensure that the maximum output power is obtained. The gearless wind power transfer technology may replace the current energy harvesting system to reduce the cost of operation and increase the reliability of wind power generation.

Controls of hydraulic wind power transfer

The energy of wind can be transferred to the generator by employing a gearbox or through an intermediate medium such as hydraulic fluids. In this method, a high-pressure hydraulic system is utilized to transfer the energy produced from a wind turbine to a central generator. The speed control of wind driven hydraulic machinery is challenging, since the intermittent nature of wind imposes the fluctuation on the wind power generation and consequently varies the frequency of voltage. On the other hand, as the load of the generators increases, the frequency of the voltage drops. Therefore, hydraulically connected wind turbine and generator need to be controlled to maintain the frequency and compensate for the power demands. This paper introduces a closed loop gain scheduling flow control technique to maintain a constant frequency at the wind turbine generator. The governing equations of the renewable energy transfer system are derived and used to design the control system. The mathematical model is verified with a detailed model built using the SimHydraulics toolbox of MATLAB. The speed control profile obtained from a gain scheduling PI controller demonstrates a high performance speed regulation. The simulation results demonstrate the effectiveness of both the proposed model and the control technique.

Modeling of hydraulic wind power transfers

The energy of wind can be transferred to the generators by using a gearbox or through an intermediate medium such as hydraulic fluids. In this method, a high-pressure hydraulic system is utilized to transfer the energy produced from a wind turbine to a central generator. In this paper, a gearless hydraulic wind energy transfer system is introduced and the dynamic model of the system is obtained. A pressure loss model is introduced to address transmission efficiency. The dynamic model is verified with a detailed model created by using the SimHydraulics toolbox of MATLAB. The comparison of the simulation results demonstrated successful validation of the mathematical model.

State-space representation of a hydraulic wind power transfer

Gearless hydraulic wind power transfers are considered noble candidates for wind energy harvesting. In this method, high-pressure hydraulics is utilized to collect the energy of multiple wind turbines and transfer it to a central generation unit. This paper introduces a state space representation of a central hydraulic wind energy generation unit. The state space model is derived from the dynamic equations of the hydraulic circuitry. The model is verified with simulation results from SimHydraulics toolbox of MATLAB. The results of state space model were in good agreement with the Matlab toolbox.

Nonlinear state space model of a hydraulic wind power transfer

Nonlinearities in gearless hydraulic wind power transfer are originated by operation of discrete elements such as check valves, proportional and directional valves, and leakage factor of hydraulic pumps and motors. Nonlinearities cause behavioral change in the system. This paper introduces a nonlinear state space representation of a hydraulic wind energy transfer system. A rate-limit controller is designed to regulate the proportional valve position to maintain the primary motors reference angular velocity. The performance of the controller is verified with simulation results. The simulation response demonstrates accurate modeling of the system operation and close tracking of the reference angular velocity profile.

Adaptive speed regulation of gearless wind energy transfer systems

The energy of wind can be transferred to the generator either by direct connection through a gearbox or by employing an intermediate medium such as hydraulic fluid. Gearless hydraulic wind power transfer systems are considered noble candidates to transfer wind energy to generators since they can collect the energy of multiple wind turbines in one generation unit. However, non-ideal dynamics of hydraulic systems imposed by pressure drops, leakage coefficient variations, and motor/generator damping coefficient, degrade the performance of power generation. This paper introduces a model reference adaptive controller (MRAC) to maintain and track a reference speed profile at the generator of a hydraulic wind power transfer. The mathematical modeling of a gearless hydraulic wind power transfer is presented and used to generate an accurate model of the plant. The control performance is verified with simulation results, which demonstrates a close tracking profile.

Modeling and Control of a Hybrid Hydraulic-Electric Propulsion System

This paper introduces a gearless hydraulic transmission system that provides an infinite speed ratio similar to a Continuous Variable Transmission (CVT) with energy storage capabilities. The transmission system is modeled in various operating conditions such as all-electric and gasoline configurations. A Rate Limited (RL) controller is designed to control the vehicle traction forces. A PI controller is designed to regulate the charge and discharge power through storage and range extender engine in different driving conditions. The results demonstrate high performance operation of the transmission system in standardized drive cycles. The results show that the control system provides a good speed-command tracking performance.

An energy storage technique for gearless wind power systems

Hydraulic wind power transfer systems allow collecting of energy from multiple wind turbines into one generation unit. They bring the advantage of eliminating the gearbox as a heavy and costly component. The hydraulically connected wind turbines provide variety of energy storing capabilities to mitigate the intermittent nature of wind power. This paper introduces the hydraulic circuitry and control algorithm for a novel wind energy electrical energy storage technique. The simulation results demonstrate successful operation of the storage to maintain the fluid in the system and control the generator speed at a reference.

Modeling of a Hybrid-Hydraulic Electric Vehicle

This paper introduces modeling of a gearless hydraulic transmission system that provides an infinite speed ratio like continuous variable transmission (CVT). The transmission system is modeled in various operating conditions such as all-electric and gasoline configurations. The results demonstrate the high performance operation of the transmission system.Copyright