Abstract
In this paper, an angular frequency dynamic-based control technique is proposed to control interfaced converters between the power grid and renewable energy sources. The proposed control technique can guarantee a stable operation of power grid under high penetration of renewable energy resources through providing the required inertia properties. The synchronous generator characteristics combined with the basic dynamic model of the interfaced converter can shape a second order derivative of the grid angular frequency consisting of converter power and virtual mechanical power derivative with embedded virtual inertia to prevent instability from the power grid as well as to generate active and reactive power with appropriate inertia. Simulation analyses are performed in Matlab/Simulink to attest the high performance of the proposed control technique.

Abstract
The growth of intermittent renewable power generation has been drawing attention to the design of balancing markets. Portugal is an interesting case study because, while wind generation already accounts for a high fraction of demand (23%), there are still no economic incentives for efficient wind forecast (wind balancing costs are passed to end consumers). We analyze the evolution of the balancing market from 2012 to 2016. Using actual costs provided by the Portuguese TSO, we find wind imbalance costs in the range of 2 to 4 EUR/MWh. These results surprisingly suggest that, even with large wind penetration and socialized imbalance costs, wind forecast errors can have a relatively low cost.

Abstract
In this work a new trading framework for demand response (DR) aggregators is proposed using a non-probabilistic model. In this model, DR is acquired from consumers to sell it to the purchasers by aggregators. Two programs, i.e., time-of-use (TOU) and reward-based DR program, are implemented to obtain DR from consumers. Then, the obtained DR is sold to buyers via two considered agreements, i.e., fixed DR contracts and DR options. The information-gap decision theory is also employed to consider the uncertainties for risk-averse aggregators. Consumer's participation behavior is considered as an uncertain parameter. A robustness function is proposed to examine the immunity of the model against adverse variations of uncertain parameters. The feasibility of the proposed model is studied on the real-world data.

Abstract
This paper presents an analytical dynamic model of a modular multilevel converter (MMC) in grid-connected operating mode. The proposed model is then efficiently used to design a circulating current controller. The proposed controller can accurately study the dynamic and steady-state performance of the converter through harmonic evaluations. Based on this configuration, the modulation is accomplished so that the stable performance of the converter in the network is obtained, which is considered as the foremost novelty of the proposed control method over existing control methods. In order to mitigate the circulating currents, the proposed controller inserts an estimated second harmonic component into modulation indices, which is considered as the second novelty of the proposed control method. The functionality and capability of the proposed control method are validated using detailed theoretical analysis and simulations with MATLAB/Simulink.

Abstract
In this paper, a function-based modulation control strategy for modular multilevel converters (MMCs) in a distributed generation (DG) system is proposed. Two novel modulation functions are introduced in this paper for the switching state functions of the lower and upper sub-modules of the interfaced MMC, which is considered as the main contribution of this control technique over other control methods. The amplitude and phase angle of the output current of the interfaced MMC can be easily applied to the proposed modulation functions to prepare a specific active and reactive power injection into the demand side. In addition, the equivalent capacitors of the lower and upper sub-modules are defined by taking into account the introduced modulation functions to guarantee an appropriate operation for the interfaced MMC in DG systems. Simulation results validate the capability of the proposed control method for MMCs under load variations.

Abstract
Ancillary services play a fundamental role in the operation of electricity systems. In the Iberian Peninsula, since mid-2014, ancillary services have gained a transnational dimension, namely through the introduction of cross border balancing replacement reserves between the Portuguese and the Spanish Transmission System Operators (TSOs). This paper evaluates the impact of replacement reserves on the Portuguese electricity system, from the onset of this mechanism until the end of 2017, as a new contribution to earlier studies. It also describes the pecuniary impact of tertiary transactions, the identification, and categorization of possible different scenarios of tertiary mobilization, and the respective impact on the internal tertiary mobilization. On the one hand, the Iberian electricity system is one of the most influenced by a high penetration of intermittent renewables, and therefore one of the best candidates to experience increased benefits from the platform. On the other hand, the Portuguese TSO is one of the most peripheral TSOs in Europe that benefits more from the market integration in various dimensions of the electricity sector.