Hydraulic Wind Power Transfer Technology

poster abstractExpiration of renewable energy tax credits in general and a gap in wind energy breakthroughs in particular have caused high cost of wind energy and technological dependency on countries such as China and Germany. Reducing the cost of wind energy requires a paradigm shift that offers simple structures, affordable design, and efficient operation. High performance energy collection, conversion, and storage techniques should therefore be introduced. Earlier solutions were based on hydraulic power transmission for a single turbine as a promising technique to decrease the weight of towers and reduce the construction process and the overall capital investment. Hydraulic techniques have not been widely used probably because of the following reasons: 1) the power transfer efficiency is low in a single turbine-single generator configuration, 2) their operation is hard to control, and 3) they require special design of hydraulic machines, such as pistons and variable displacement pumps. Recent advancements in large hydraulic equipment and their improved efficiencies have encouraged companies such as Mitsubishi and Chapdrive to invest in onshore and offshore hydraulic driven wind power. However, in their designs, the already existing problems such as the heavy weight of the tower and the efficiency of the overall power transfer systems remain un-resolved. Proposed in this research is a technology that reduces the capital investment and enhances the overall system efficiency of hydraulic equipment. The technique integrates multiple wind turbines to a central generation unit through hydraulic wind power, and by doing so, it reduces the capital equipment of the entire power plant and substantially increases power transfer efficiency. The system operates when a wind-driven hydraulic pump converts the energy of the wind into a high-pressure medium. The energy of several wind turbines is collected and transferred to a pair of hydraulic pumps coupled with two ground-level generators. The main generator generates power at 60 Hz, while the auxiliary generator stores and releases the energy as required to regulate the wind power and load variations

Automatic Control and Fault Diagnosis of MEMS Lateral Comb Resonators

Recent advancements in microfabrication of Micro Electro Mechanical Systems have made MEMS an important part of many applications such as safety and sensor/control devices. Miniature structure of MEMS makes them very sensitive to the environmental and operating conditions. In addition, fault in the device might change the parameters and result in unwanted behavioral variations. Therefore, imperfect device structure, fault and operating point dependencies suggest for active control of MEMS.;This research is focused on two main areas of control and fault diagnosis of MEMS devices. In the control part, the application of adaptive controllers is introduced for trajectory control of the device under health and fault conditions. Fault in different forms in the structure of the device are modeled and foundry manufactured for experimental verifications. Pull-in voltage effect in the MEMS Lateral Comb Resonators are investigated and controlled by variable structure controllers. Reliability of operation is enhanced by active control of the device under fault conditions.;The second part of this research is focused on the fault diagnosis of the MEMS devices. Fault is introduced and investigated for better understanding of the system behavioral changes. Modeling of the device in different operating conditions suggests for the multiple-model adaptive estimation (MMAE) fault diagnosis technique. Application of Kalman filters in MMAE is investigated and the performance of the fault diagnosis is compared with other techniques such as self-tuning and auto self-tuning techniques. According to the varying parameters of the system, online parameter identification systems are required to monitor the parameter variations and model the system accurately. Self-tuning banks are applied and combined with MMAE to provide accurate fault diagnosis systems. Different parameter identification techniques result in different system performances. In this regard, this research investigates the application of Recursive Least Square with Forgetting Factor. Different techniques for tuning of forgetting factor value are introduced and their results are compared for better performance. The organization of this dissertation is as follows:;Chapter I introduces the structure of the MEMS Lateral Comb Resonator; Chapter II introduces the application of control techniques and displacement feedback approach. Chapter III investigates the control approach and experimental results. In chapter IV, a new controller is introduced and designed for the MEMS trajectory controls. Chapter V is about the fault and different techniques of fault diagnosis in MEMS LCRs. Chapter 6 is the future work suggested through the current results and observations. Each chapter contains a section to summarize the concluding remarks

A Bipolar SEPIC Converter with Wide Output Voltage Range

poster abstractEnergy Systems and Power Electronics Laboratory, Purdue School of Engineering, IUPUI. In order to pursue a perfect inverter, a new inverter technology is designed based on SEPIC converter that can efficiently generate pure sinusoidal waveforms and operate in a wide range of loading conditions. The groundbreaking design of the new inverter is that, for the first time, the number of high-frequency switching-transistors is reduced to one. By changing the switching frequency and duty cycle for the switch, the voltage-level of the output signal will be continuously controlled to produce a nearly pure sinusoidal waveform, and the voltage-level can reach infinity without using any switch map in theory. In order to achieve the DC to AC conversion, inversing the polarity and the boost operation for the output voltage are the two main problems in the process of achieving this goal. To proof the possibility of the new inverter technology, a research for a bipolar SEPIC converter is firstly proposed in order to achieve the voltage polarity inversion and the boost operation. The research basically use a diode to regulate the current direction that goes through the load. By changing the direction of the diode, the polarity of the output voltage can be inversed. For the boost operation, a simulation setup in Simulink and some actual tests have been used to find out the sizes for each elements in the circuit that can boost the output voltage of the converter to 110V at a specific frequency and duty cycle of the only switch. The result of the research had showed that this converter not only had the capability to provide a very wide output voltage ranges and power levels, but also can generate output voltage and power levels for positive and negative polarities

Modeling and Control of A Combined Wind-Solar Microgrid

This paper introduces a standalone hybrid power generation system consisting of solar and wind power sources and a DC load. A supervisory control unit, designed to execute maximum power point tracking (MPPT), is introduced to maximize the simultaneous energy harvesting from overall power generation under different climatic conditions. Two contingencies are considered and categorized according to the power generation from each energy source, and the load requirement. Simulation results demonstrate effectiveness of the controllers and functionality of the maximum power point tracking algorithm in each operating condition for both solar and wind power sources

Control of a Hydraulic Wind Power Transfer System under Wind Disturbance

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 poster introduces a closed loop 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 speed control profile obtained from a PI controller demonstrates a high performance speed regulation. The simulation results demonstrate the effectiveness of both the proposed model and the control technique

Piecewise Affine System Identification of a Hydraulic Wind Power Transfer System

Hydraulic wind power transfer systems exhibit a highly nonlinear dynamic influenced by system actuator hysteresis and disturbances from wind speed and load torque. This paper presents a system identification approach to approximate such a nonlinear dynamic. Piecewise affine (PWA) models are obtained utilizing the averaged nonlinear models of hysteresis in a confined space. State-space representation of PWA models is obtained over the allocated operating point clusters. The experimental results demonstrate a close agreement with that of the simulated. The experimental results and simulation show more than 91% match

ENERGY STORAGE SYSTEM FOR HYDRAULIC WIND ENERGY TRANSFERS

poster abstractGearless hydraulic transmissions are considered noble candidates for wind power transfer systems. Hydraulic wind power transfer systems allow collecting the energy of multiple wind turbines into one generation unit. Fur-thermore, elimination of the gearbox as a bulky and expensive to maintain component reduces the cost of energy conversion. The hydraulically con-nected harvesting systems require controllers to maintain the frequency and generate the required power. However, the intermittent nature of wind im-poses fluctuation on the amount of generated wind power and on the fre-quency of the output voltage. This poster introduces a wind energy storage technique through a hydraulically connected wind power transfer system. The simulation results demonstrate the successful operation of the storage to maintain the fluid in the system to keep the generator speed at a prede-termined value. The system is mathematically modeled and the control sys-tem is derived

Energy Storage Techniques for Hydraulic 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 presents an approach to make wind power become a more reliable source on both energy and capacity by using energy storage devices, and investigates methods for wind energy electrical energy storage. The survey elaborates on three different methods named “Battery-based Energy Storage”, Pumped Storage Method, and “Compressed Air Energy Storage (CAES)”

Control of Single Switch Inverters

poster abstractThe single switch inverter was introduced to generate a pure sinusoidal output voltage. The system behaves like a non-minimum phase system in all operating ranges except when it is operating to produce negative half cycle in buck mode. When addressed from a control perspective, the right half plane zeros or the non-minimum phase zeros in the transfer function complicate the control design scheme. The Dual Feed-forward Predictive Control (DFPC) is a method of feed-forward control is used to force the non-minimum phase system to behave like a minimum phase system. The controller successfully isolates the non-minimum phase part of the system from the minimum phase. Both separated minimum phase and non-minimum phase sub-systems were used in the dual feed-forward scheme to generate desired references. The non-minimum phase dynamics are transformed to minimum phase by using an inverse system transfer function as parallel compensator. In this method, the plant is split into two parts to generate two signals. One signal is to make the plant track with a feed-forward control signal that drives the plant to track the reference signal. The signals produced by the feed-forward transfer functions are assumed to contain bounded energy and have no influence on the closed loop stability. For perfect tracking, the error should reach zero which can be accomplished using various types of controller including a simple gain. However, in the new inverter circuit, an adaptive PI controller is required to adjust the gains continuously