a b s t r a c tThis paper proposes an overarching review of national municipal waste management systems and wasteto-energy as an important part of it in the context of circular economy in the selected countries in Europe. The growth of population and rising standards of living means that the consumption of goods and energy is increasing. On the one hand, consumption leads to an increase in the generation of waste. On the other hand, the correlation between increased wealth and increased energy consumption is very strong as well. Given that the average heating value of municipal solid waste (MSW) is approximately 10 MJ/kg, it seems logical to use waste as a source of energy. Traditionally, waste-to-energy (WtE) has been associated with incineration. Yet, the term is much broader, embracing various waste treatment processes generating energy (for instance, in the form of electricity and/or heat or producing a wastederived fuel). Turning waste into energy can be one key to a circular economy enabling the value of products, materials, and resources to be maintained on the market for as long as possible, minimising waste and resource use. As the circular economy is at the top of the EU agenda, all Member States of the EU (including the EEA countries) should move away from the old-fashioned disposal of waste to a more intelligent waste treatment encompassing the circular economy approach in their waste policies. Therefore, the article examines how these EU policies are implemented in practice. Given that WtE traditionally is attached to the MSW management and organisation, the focus of this article is twofold. Firstly, it aims to identify the different practices of municipal waste management employed in selected countries and their approaches in embracing the circular economy and, secondly, the extent to which WtE technologies play any role in this context. The following countries, Estonia, Greece, Italy, Latvia, Lithuania, Norway, Poland, Slovenia, Spain, and the UK were chosen to depict a broad European context.

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Abstract-This paper presents a novel modulation strategy for n-phase neutral-point-clamped (NPC) converters. The proposed modulation strategy is able to control and completely remove the low frequency neutral-point (NP) voltage oscillations for any operation point and load types. Even when unbalanced and/or nonlinear loads are considered, the NP voltage remains under total control. Consequently, the strategy is very attractive for nphase active filters. In addition, it enables the use of low capacity film capacitors in NPC converters.The proposed modulation takes the carrier-based modulation strategy as a basis. It is formulated following a generalized approach that makes it expandable to n-phase NPC converters. In addition, the NP voltage is controlled directly using a closedloop algorithm that does not rely on the use of the linear control regulators or the additional compensators used in other modulation algorithms. Therefore, no tuning of parameters is required and it performs optimally for any operating conditions and kind of loads, including unbalanced and nonlinear loads. Although the high frequency harmonic content of the output voltages may increase, the weighted total harmonic distortion generated by the proposed strategy is similar to that of a standard sinusoidal pulsewidth modulated strategy. The proposed modulation algorithm has been tested in a four-leg NPC converter prototype performing as a three-and four-phase system and operating with balanced and unbalanced loads.

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This paper presents a generalized PWM-based control algorithm for multiphase neutral-point-clamped (NPC) converters. The proposed algorithm provides a zero-sequence to be added to the reference voltages that contributes to improve the performance of the converter by: i) regulating the neutral-point (NP) current to eliminate/attenuate the low-frequency NP voltage ripples, ii) reducing the switching losses of the power semiconductors and iii) maximizing the range of modulation indices for linear operation mode. The control method is formulated following a carrier-based PWM approach. Hence, dealing with complex space-vector diagrams to solve the modulation problem for multiphase converters is avoided. The recursive approach means that it can be easily extended to n-phase converters without increasing the complexity and computational burden, making it especially attractive for digital implementation. The proposed method allows regulating the NP voltage without the need for external controllers; therefore, no parameter tuning is required. The algorithm has been tested in a four-leg NPC converter prototype performing as a three-and four-phase system and operating with balanced and unbalanced loads. Index TermsCarrier-based pulse-width modulation, multiphase multilevel converter, neutral-point-clamped converter, capacitor voltage balance.

This paper proposes three generator control strategies for Wells turbine-based floating oscillating water column (OWC) devices comprising electrical or mechanical energy storage systems. The first control strategy is indicated for low inertia turbine OWC devices that include ultracapacitors. This control law optimizes the power take-off efficiency by means of an instantaneous speed controller that allows variation of the turbine rotational speed in a wave-by-wave basis. In addition, the profile of the electrical power injected into the grid is smoothed, so that a high penetration of wave energy does not threaten the grid stability. The second and third control laws are developed for OWC systems comprising a flywheel. Quasi-constant and variable speed controllers are proposed. These control laws do not maximize the system efficiency but allow the use of simpler, smaller and cheaper power electronics.Additionally the power quality is also optimized. The development of the proposed control algorithms is accomplished by means of simulations and verified with an experimental test rig.