Amit Pandey

Surge Capability Testing of Supercapacitor Families Using a Lightning Surge Simulator

Supercapacitors (SCs) are capable of storing energy in the range of fractional joules to several thousands of joules despite their lower dc voltage ratings. Farad-order capacitances combined with milliohm-order equivalent series resistances provide time constants ranging from fractional seconds to seconds. Given these time constants, compared to the time durations of power line transients in the range of a few microseconds to several hundreds of microseconds, these devices may be able to withstand short-duration surges with energy values specified in IEEE C62-XX series, IEC 61400-4-5, and similar standards. However, there is little or no manufacturer datasheet information on these aspects. This paper provides details of an automatic tester interfaced with a lightning surge simulator, a test procedure, and summarized test data on three different families of SCs. The test data set provides some valuable insight in estimating the capabilities of these new SC families to withstand surges and transients, which, in turn, could lead to nontraditional applications.

Robust Pole Placement With Moore's Algorithm

We consider the classic problem of pole placement by linear state feedback. We adapt the Moore eigenstructure assignment algorithm to obtain a novel parametric form for the pole-placing gain matrix, and introduce an unconstrained nonlinear optimization algorithm to obtain a gain matrix that will deliver robust pole placement. Numerical experiments indicate the algorithms performance compares favorably against several other notable robust pole placement methods from the literature.

Integration of supercapacitors into wirelessly charged biomedical sensors

Conventional implantable sensors are often battery operated. Batteries are characterized by their high energy densities which allow for long term operation. However, it can take a long time to charge up a battery. As an emerging technology, a supercapacitor can be charged very quickly and it is considered as alternative energy storage to replace traditional batteries. This paper proposes an implantable biomedical sensor which operates off a super capacitor which is wirelessly charged. A feasibility analysis of supercapacitors is presented first, and then the system design and implementation are detailed for achieving wireless charging control with digital data logging. Design considerations relating to supercapacitor specific issues are also presented in detail. The implemented circuit can wirelessly charge a 5.5V, 1F supercapacitor in approximately 5 seconds. This capacitor powers a microcontroller and wireless transceiver for approximately 60 minutes before the circuit needs to be charged again.

A unified method for optimal arbitrary pole placement

Abstract We consider the classic problem of pole placement by state feedback. We offer an eigenstructure assignment algorithm to obtain a novel parametric form for the pole-placing feedback matrix that can deliver any set of desired closed-loop eigenvalues, with any desired multiplicities. This parametric formula is then exploited to introduce an unconstrained nonlinear optimisation algorithm to obtain a feedback matrix that delivers the desired pole placement with optimal robustness and minimum gain. Lastly we compare the performance of our method against several others from the recent literature.

The role of nonminimum phase zeros in the transient response of multivariable systems

Nonminimum phase zeros are known to cause fundamental performance limitations in the system transient response, particularly undershoot and overshoot. Much of the available literature deals with scalar-input scalar-output systems. In this paper we consider the role of nonminimum phase zeros on the transient response of multivariable systems. We explore via examples the extent to which such zeros may imply undershoot or overshoot in the transient response.

Performance survey of robust pole placement methods

The classic problem of robust pole placement for linear time invariant systems via state feedback has been studied for several decades, and involves obtaining a gain matrix that will assign a certain desired set of closed-loop poles, while also providing a robust eigenstructure that is insensitive to uncertainties in the system matrices. There are several ways of measuring the robustness of the eigenstructure, and numerous methodologies have appeared in the literature to address the problem. In this paper, results from extensive experiments comparing the performance of a number of methods-including variations on two methods previously proposed by the present authors-against a variety of robustness measures are reported. The size of the matrix gain, runtime and accuracy of the pole placement achieved by each method are also compared. The results show some notable differences between the methods surveyed.

Surge endurance capability testing of supercapacitor families

Supercapacitors are usually low voltage, high capacity devices with milliohm order equivalent series resistances. They usually have time constants from fractional seconds to seconds. Due to these long time constants, compared to the time durations of power line transients in the range of few microseconds to several 100 microseconds, these devices may be able to withstand short duration surges with energy values specified in IEEE C62–41 series and IEC 61400–4–5 and similar standards. However there is little or no manufacturer data sheet information on these aspects. The paper provides the details of a test procedure to test the surge withstand capability of supercapacitors. In addition, essential details of a customized tester interface required for a lightning surge simulator and surge-endurance test results for three supercapacitor families are also presented.

Pre-filtering in gain-scheduled and robust control

We revisit the issue of gain-scheduled versus robust control with a focus on matrix inequalities. It has been established that for uncertain continuous-time linear systems that depend affinely on the uncertainty, gain-scheduled stabilizability implies robust stabilizability. That is, as far as stabilizability is concerned, using a more complex gain-scheduled controller brings no advantage. In the case of performance and discrete-time systems, counter-examples exist that show that gain-scheduling can indeed be advantageous. These proof are unfortunately not constructive, and the associated necessary and sufficient conditions are hard to verify even in low dimensions. In practice, conditions based on Linear Matrix Inequalities (LMIs) are widely used to design robust and gain scheduled controllers at the expense of some conservatism. The main goal of the present paper is to explore to what extent solvability of certain LMIs for gain-scheduled control also implies solvability of the corresponding robust control inequalities. One issue investigated in detail is that of using pre-filters to handle uncertainty appearing in the input matrix. Our results show that this technique, which has been used since the 80s is rarely productive in the sense that solvability of certain gain-scheduled control design problems for the original system augmented with a pre-filter often implies existence of a robust control for the original system, which we calculate explicitly using a projection. One exception seem to be the LMIs based on the condition of Daafouz and Bernussou (2001) for discrete-time systems. A series of examples illustrate the results.

Robust repeated pole placement

We consider the classic problem of pole placement by state feedback. Recently [1] offered an eigenstructure assignment algorithm to obtain a novel parametric form for the pole-placing gain matrix to deliver any set of desired closed-loop eigenvalues, with any desired multiplicities. In this paper we employ this parametric formula to introduce an unconstrained nonlinear optimisation algorithm to obtain a gain matrix that delivers any desired pole placement with optimal robustness.

Investigation of failure patterns of desktop computer power supplies using a lightning surge simulator and the generation of a database for a comprehensive surge propagation study

According to the International Technology Roadmap for Semiconductors (ITRS) future VLSI devices of gigahertz capability are expected to have feature sizes below 45 nm with DC power supply requirements with sub 1V and the equivalent noise voltages close to the DC rail values. This scenario makes the surge resist capability of processor type loads and the associated power conversion interfaces with lot of power semiconductors, seriously vulnerable to lightning and other power transients. In a major research project to predict the propagation of transients within the power conversion interfaces using wavelet transform, it was necessary to develop an experimental database of surge failures in power electronic subsystems. This paper highlights the results of destructive testing of desk top PC power supplies using a lightning surge simulator which will be used for comparing experimental data with analytical/simulated results.