Improving grid stability by integration renewables using static synchronous generators

Abstract

(English) The European Commission has plans to transition from classic power system to a net-zero emission power system, mainly by focusing on renewable sources. The power plants owners and power grid operators have technical challenges to achieve this goal. The used renewables technology is one of key challenges. The active power dynamic stability, generation frequency regulation, voltage stability issues, and reactive power balancing are main technical challenges. This Ph.D. thesis proposes a new technology for operation, control, and grid connection of renewable power plant that suports power system dynamic stability during energy transition. The proposed technology is emulation of classic synchronous machine in control loops of electronic power converters, and it provides a feasible operation of a renewable static synchronous generator (SSG) based on synchronous power controller (SPC). The proposed technology (RSSG-SPC) has flexibility and can comply with grid codes. The SPC technique is the core of RSSGSPC technology. So, there are two main parts in RSSG-SPC. The electromechanical part emulates performance of synchronous power generation. This part provides virtual damping and virtual inertia functionalities and it contributes to active power control and frequency regulation. The second part is virtual admittance which provides the control of a voltage source converter in current mode. So, the converter can be modeled such as Thevenin model of synchronous generator. This part provides reactive power control and voltage regulation. The theory of RSSG-SPC, control layers modeling, and RSSG SPC’s grid connection modeling are illustrated. The RSSG-SPC’s operations to overcome technical challenges during grid connection, RSSG-SPC’s flexibilities to comply with grid codes, and RSSG-SPC’s capabilities to support dynamic stability have been discussed. The performance of renewable power plant based on RSSG-SPC technology has been evaluated by doing detailed mathematical analysis, dynamic modeling, time domain simulation, and laboratory tests validations. The RSSG-SPC grid connection is analyzed for several network topologies and different RSSG-SPC operations including, i) RSSG-SPC connected to simple bus supported by weak grid either while bus is supported by a stiff grid, ii) RSSG-SPC operates to support a long ac transmission system, iii) RSSGSPC contributes in a unique generation area system (IEEE 14B), iv) RSSG-SPC operates as big generation plant and supports a multi area generation system (Kundur’s system), and v) RSSG-SPC operates as a small generation unit in Kundur’s system. An algorithm is developed for implementation and modeling of RSSG-SPC in the noted applications. The algorithm covers RSSGSPC grid connection modeling taking to account the parameters of RSSG-SPC and power grid. The dynamic indices are proposed for tuning of RSSG-SPC’s dynamic parameters (virtual inertia and virtual damping) aiming to have a stable operation of RSSG-SPC. Also, considering the real situation of power grid, adequate modifications are applied to RSSG-SPC’s control layers leads to provide adaptable operation of RSSG-SPC in the grid connection mode. Moreover, an active power limiter is proposed to solve the power transfer limitation of renewables and to provide functionalities to follow the grid operators balancing signals.