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Abstract--The increasing amount of renewable power generation systems is a challenging issue for the control and operation of the electrical networks. One of the main issues is their lack of inertia, which is becoming a greater problem as much as the share of the power plants based on traditional synchronous generators gets reduced. In this regard the new grid codes ask these plants to provide new functionalities such as the frequency support and inertia emulation.In this paper, a synchronous power controller for gridconnected converters is proposed as a good solution for the renewable generation systems with energy storage. It provides inertia, damping and flexible droop characteristics. Different from the faithful replication of the swing equation of synchronous machines, an alternative control structure is proposed, by which the damping and inherent droop slope can be configured independently to meet the requirements in both dynamics and frequency regulations. Analysis and experimental results are both shown to validate the proposed controller.

Abstract:Due to increasing level of power converter-based component and consequently the lack of inertia, automatic generation control (AGC) of interconnected systems is experiencing different challenges. To cope with this challenging issue, a derivative control-based virtual inertia for simulating the dynamic effects of inertia emulations by HVDC (highvoltage direct current) interconnected systems is introduced and reflected in the multi-area AGC system. Derivative control technique is used for higher level applications of inertia emulation. The virtual inertia will add an additional degree of freedom to the system dynamics which makes a considerable improvement on first overshoot responses in addition to damping characteristics of HVDC links. Complete trajectory sensitivities are used to analyse the effects of virtual inertia and derivative control gains on the system stability. The effectiveness of the proposed concept on dynamic improvements is tested through Matlab simulation of two-area test system for different contingencies.

The utilization of renewable sources brings many benefits to electric power systems, but also some challenges like the impact that renewable power plants employing power electronics have on the grid, which is gaining importance as the penetration of this type of generating stations increases, driven by the construction of large wind or solar photovoltaic power plants. This paper analyses the impact of large-scale photovoltaic power plants on a transmission grid for different penetration levels. The analysis considers power plants formed by a number of power converters employing synchronous power controllers, that allow them to have a harmonious interaction with the grid, and compares their performance with that of conventional power converter controllers, assuming in both cases that the power plants participate in frequency and voltage regulation. The study addresses both the small-signal stability of the system and its response to large disturbances that alter the active power balance and frequency stability. The results of the analysis show that photovoltaic power plants using synchronous power controllers are able to limit frequency deviations, improve the oscillation damping, and reduce the stress of other generating units, thus having a beneficial impact on the power system.