The integration of non-synchronous generation units and energy storage through power electronics is introducing new challenges in power system dynamics. Specifically, the rotor angle stability has been identified as one of the major obstacle with regards to power electronics dominated power systems. To date, conventional power system stabilizer (PSS) devices are used for damping electromechanical oscillations, which are only tuned sporadically leading to significant deterioration in performance against the ever-changing operating conditions. In this paper, an intelligent power oscillation damper (iPOD) is proposed for grid-forming converters to attenuate electromechanical inter-area power oscillation. In particular, the iPOD is applied to a synchronous power controller (SPC) based grid-forming power converter to increases gain of the active power control loop at the oscillatory frequency. Predictions regarding the mode frequency, corresponding to the current operating points, are given by an artificial intelligence ensemble model called Random Forests. The performance of the proposed controller is verified using the two area system considering symmetrical fault for random operating points. In addition, a comparison with PSS installed in each generator reveals the individual contribution with respect to the inter-area mode damping.

to these spikes, damaging thus the control performance. This problem is worse in case of harmonics where the noise presence is still higher and the control signals themselves have a higher frequency.This paper deals with the implementation of parallel virtual admittances at harmonic frequencies. The virtual admittance approach provides advantages if compared with virtual impedance, as it does not introduce any derivative term in the controller. As the admittance is a virtual element this work takes advantage of this and considers a synchronous generation systems with different admittances at different frequencies. By means of this approach once the grid harmonic distortion is being analyzed, several harmonic virtual admittance loops can be implemented in the control of DC-AC converters, in order to attenuate the grid voltage distortion. These virtual admittances operate in parallel with the main voltage loop at fundamental frequency, in order to inject the required harmonic content at a specific frequency to enhance the voltage profile.On this paper the scope will be focused just in the harmonic attenuation. As it will be proven, being able to inject harmonics to the grid by this synchronous power control makes it possible to inject active and reactive power and also attenuate harmonic distortion appearing at the point of common coupling (PCC). II. FUNDAMENTAL AND HARMONIC CURRENT CONTROL LOOPIn this chapter the control strategy applied is based on the enhanced emulation of a synchronous generator where the synchronization loop is inherently implemented in the control equations [5]. The main mechanical characteristics of the synchronous generators, collected by the swing equations, are the mechanical inertia and the damping effect. Following the electrical characteristic of the synchronous generator is enclosed in the virtual admittance block, which is described in detail in [6].These blocks are depicted in Fig. 1.Abstract -The appearance of harmonics in the grid voltage is an issue for the generation systems and grid connected consumers. This paper presents the basic control strategy to be implemented in Synchronous Power Control (SPC) based power converters, which contributes to reduce the harmonic content in the voltage by means of injecting different harmonic current to the grid using a separated virtual admittance algorithm. This control strategy is capable of generating such a current reference that attenuates the harmonic values at the point of connection of the converter.

The increasing penetration of renewable energy systems force the grid-connected power converters to use advanced active power controls, which needs to add more functionalities to their control strategies. A power reserve control is being required for grid support capabilities on Renewable Energy Sources (RES). Classical algorithms as the Maximum Power Point Tracking (MPPT) cannot withstand power reserve on its control, due to this, different control strategies have to be formulated to gain the power reserve capability. On this paper a cost-effective solution to perform the power reserve is presented, which provide a good solution for frequency regulation as well as for general grid fault conditions. Simulation test have been performed to verify the control capacity of this cost-effective solution.

The advent of renewable energy has posed difficulties in the operation of power systems whose net inertia is becoming critically low. To face such challenges, grid-forming power has been one of the potential solutions pursued by the industry and research community. Though promising, grid-forming power converters are still immature for mass deployment in power systems. In the meanwhile, an enormous amount of grid-following power converters has been underexploited when it comes to gridsupporting functionalities. Therefore, this paper proposes an external inertia emulation controller (eIEC) for grid-following power converter to provide frequency support to the grid. For the purpose of minimizing installation efforts and resources, the controller is designed in such a way that it can be implemented in an external controller communicating with the grid-following power converter via an industrial communication link. This paper also investigates the effect of communication delay on the stability performance of the proposed controller. In addition to the detailed analysis, hardware-in-the-loop experiments are also carried out to validate the proposed eIEC.

The increasing penetration of grid-connected RES systems, advanced control algorithms have been developed to operate under grid faults and fulfill strict requirements of the grid codes. In order to overcome this, the current controller performance is critical considering it as the inner control loop of any grid-connected RES system. Based on the resonant control concept, this paper presents a modified structure for this controller which results advantageous when implemented on RES systems, as it permits better performance during the dynamic state of the controller. This paper also deals with the analysis of the decoupling terms in the reference frame, as well as the capability to generate a decoupled control of the positive and the negative sequence. The proposed controller will be analyzed, discussed and finally validated by means of simulation analysis.