Jari Leppaaho

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This paper investigates the dynamic properties of the photovoltaic-generator-interfacing voltage-controlled buck power stage operating in both the maximum and limited power point tracking modes. The photovoltaic generator (PVG) is known to possess both current- and voltage-source properties with respect to its maximum power point. While voltage-fed(More)
Reliably operating solar-energy systems composing of solar arrays and their interfacing converters are of prime importance to maximize the solar-energy harvesting. The paper investigates the solar-generator-interfacing problems in terms of voltage-fed maximum-power-point tracking converters and shows that there are two main reasons for the observed(More)
The concern on observed climate change has increased the utilization of renewable energy sources. The harvesting of solar energy is recognized as one of the key issues in reducing green house gas emission. Reliable solar-energy systems composing of solar arrays and their interfacing converters are of prime importance in uninterrupted solar energy(More)
It is well known that the application of peak-current-mode (PCM) control produces highly desirable properties in the conventional or voltage-fed converters but requires to compensate the inductor-current loop for extending the active duty ratio beyond 50%. This paper investigates the dynamical properties and operational constraints of a PCM-controlled(More)
The interfacing of photovoltaic (PV) energy source is known to be problematic due to the highly varying terminal characteristics of the energy harvesting unit, generally a PV generator. Therefore, its power flow needs to be regulated and a certain maximum power point (MPP) traced. The switched-mode dc-dc converters are conventionally used to interface(More)
Large-scale harvesting of solar energy is an important action to decelerate the observed climate changes and ensuring the availability of energy also in the future. It has been observed that the maximum-power-point (MPP) tracking converters have high contribution on the reliability problems in the photovoltaic energy systems because of misunderstanding of(More)
Utilization of solar energy is one important action to decelerate the observed climate change and to ensure the availability of energy in the future. Reliable solar-energy systems composing of solar arrays and their interfacing converters are of prime importance but known to have certain operational constraints causing reliability problems. The paper(More)
The EMI-filter design rules based on certain impedance parameters are developed in the late 1970's by means of a small-signal equivalent circuit valid only for the converters operating under direct-duty-ratio control in continuous conduction mode. Basically the design rules are valid for an arbitrary switched-mode converter but the implicit nature of some(More)
The paper investigates the dynamic effects the coupled-inductor technique creates in a superbuck converter. The results are compared to the corresponding discrete-inductor converter. It is well known that the ripple current in an inductor can be significantly reduced by using coupled inductors. The investigations show that the transient dynamics of the(More)
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