H. R. Pota

Minimax LQG optimal control of a flexible beam

The paper presents a practical robust controller design methodology based on recent theoretical results on minimax LQG control. This controller design methodology is illustrated with the design of a robust feedback controller for the control of vibrations in a flexible cantilever beam. The minimax LQG control approach is used to design a controller which minimizes the total vibration energy in the beam which is subject to white noise disturbances. The controller is designed to be robust against uncertainties introduced by neglecting the higher order modes of the beam.

Voltage control of distribution networks with distributed generation using reactive power compensation

Voltage profile of distribution networks with distributed generation are affected significantly due to the integration of distributed generation (DG) on it. This paper presents a way to control voltage of distribution networks with DG using reactive power compensation approach. In this paper, the voltage control approach is shown based on the worst case scenario of the network. To keep the voltage profile within the specified limits, it is essential to regulate the reactive power of the compensators. Finally, based on this concept, a static analysis is done on a 15- bus Japanese distribution system, called Kumumoto system where the system is modified with the inclusion of distributed wind generators, photovoltaics, and synchronous generators.

Robust H ∞ control in fast atomic force microscopy

This paper presents the design of a robust H∞ controller for fast tracking of an Atomic Force Microscope (AFM). The controller design is based on a physical model of the AFM piezoelectric tube positioner. External capacitors are connected in series with the x and y contacts of the piezoelectric tube to provide measured voltages which are proportional to the charge on the actuator. The parameters for a nonlinear hysteresis model are obtained from measurements of the system frequency response and time domain response. Experimental results show that the robust H∞ controller can increase the scanning speed significantly.

Application of centrality measures of complex network framework in power grid

The classical definitions of various centrality measures are modified to incorporate electrical parameters of the power grid. In this paper three distinct measures of centrality are presented and they are described with suitable examples. The usefulness of these measures are described. Various standard test systems are simulated to find critical nodes of the system. Complex network is a new area of research in power system. Simulation of several systems suggests that the definitions proposed in this paper can be used as a standard.

Robust sliding mode control of an agricultural tractor under the influence of slip

Precise guidance of agricultural vehicles is an area which is beginning to benefit from an increased awareness of its importance and its challenge. It is important as farming is becoming increasingly and justifiably automated, and because precision and autonomous farming is more necessary now, in order for the industry and individual farms to be competitive. It is a challenge because agricultural vehicles operate in quite uncertain and unpredictable environments. It is important that vehicles are guided with precision in a lateral as well as longitudinal direction, while being subjected to often significant disturbance forces, or slip, due to uncertain and sloping terrain. Little work has been carried out thus far in the guidance of such vehicles where vehicle slip is significant. In this paper, the authors provide an alternative approach to the robust trajectory tracking of an agricultural tractor under the influence of lateral and longitudinal velocity slip. This approach takes into account the dynamics of the steering system, and caters for slip velocities which are bounded but time varying. This is achieved via the use a robust combination of sliding mode control and integrator backstepping. Robust stability is achieved, ensuring the trajectory error is bounded to an adjustable region around the origin. Simulation results show that the alternative approach proposed yields suitable robust trajectory tracking.

Worst case scenario for large distribution networks with distributed generation

Integration of distributed generation (DG) in distribution network has significant effects on voltage profile for both customers and distribution network service providers (DNSPs). This impact may manifest itself positively or negatively, depending on variation of the voltage and the amount of DG that can be connected to the distribution networks. This paper presents a way to estimate the voltage variation and the amount of the DG that can be accommodated into the distribution networks. To do this, a voltage rise formula is used with some approximation and the validation of this formula is checked by comparing with the existing power systems simulation software. Using the voltage variation formula, the worst case scenario of the distribution network with DG is used to estimate the amount of voltage variation and maximum permissible DG.

Modified centrality measures of power grid to identify critical components: Method, impact, and rank similarity

This paper justifies the criticality of nodes in a power system found from previous analysis. Critical nodes are identified from complex network theory based modified centrality approaches whose failure would stress the system badly in terms of line overloading. Impact of removal of critical nodes on two different standard test systems are analyzed. Simulation results suggest that these indices do not change with continually varying power system load and generation.

Impact of high wind penetration on the voltage profile of distribution systems

In this paper, simulation results showing the effect of lower and higher penetration of distributed wind generation on the voltage profile in distribution systems have been presented. The analysis is carried out over two distribution test systems. The detailed mathematical modeling of the system is also presented. It also investigates the small-signal stability of distribution systems using eigenvalue approach. The analyses show that voltage variation problems occur in different nodes of the distribution networks with an increase of penetration level. However, proper selection of dispersion level can improve the voltage profile of the distribution systems.

Nonlinear excitation controller for power systems using Zero dynamic design approach

This paper presents a nonlinear excitation controller design technique for interconnected power systems. A zero dynamic design approach is used to design the controller which is useful when the system is partially linearizable and the obtained control law, using this approach is simpler as compared to that of a fully or exactly linearizable system. The performance of this controller is tested on a single machine infinite bus (SMIB) system over a wide variation of operating region and compared to the nonlinear excitation controller which is designed using the concept of exact linearization. Simulation results show that the proposed control scheme can improve the stability of power systems, regardless of operating points and the performance is very similar to that of exactly linearized controller.

Critical node identification of smart power system using complex network framework based centrality approach

A method of critical node identification in a power system is presented in this paper. Maximum flow in a network is used to measure centrality of various nodes in the power system. The proposed approach is an improvement of previous methodology in the sense that it does not take into consideration shortest electrical distance as path to flow power. Instead of using normal steady-state condition maximum possible flow is considered. Simulation of various standard test systems are carried out to identify critical nodes.