Hybrid synchronous condenser system design and control for enhanced grid services
Creators: name: Nuhic, Mirza
Publisher: name: Zenodo
Year: 2022
Subjects: Power system modelling, battery energy storage system, synchronous condenser, hybrid plant, oscillation damping, inertia

description: One of the major challenges for the future power systems is decommissioning of synchronous machine-based generation, which will result in reduced overall strength of the system. For example, as the number of synchronous machines in the generation mix subsides, the inertia in the system will reduce making the frequency more susceptible to large swings in the face of disturbances, the voltage control will be significantly affected, as well as the short circuit power levels. The total renewable energy capacity of the world has increased by ca. 260 GW in 2020 as compared to the previous year, taking the total capacity to ca. 2800 GW. The share of the renewable energy in the energy mix is expected to continue to rise, making it a necessity to address the problems previously mentioned. Phasing out of conventional synchronous machines means that other technologies will have to be able to provide and replicate their functions and capabilities in terms of voltage and frequency control, short-circuit power, inertia, oscillation damping etc. The most common technology is the power converter interfaced renewable energy. Flexibility of power converter control is one of the major advantages of this technology in bringing the necessary functions to the system and provide similar characteristics as a conventional generation. However, there are some obstacles that cannot be overcome by only power converters due to the physical and economical aspects of the technology. In that regard, battery systems and supercapacitors can introduce that additional active power and provide a range of beneficial functions. Synchronous condensers have been identified as a technology that can contribute with high levels of shortcircuit power and provide inertia that will inevitably reduce in converter dominated power systems. In this thesis, we are proposing a hybrid synchronous condenser (HSC) system consisting of a synchronous condenser and BESS. This system is designed with a goal to integrate and combine the benefits of both technologies with regards to provision of ancillary services. Furthermore, we analyzed and compared the capabilities of the different technologies and control strategies and attempted to quantify the contribution in terms of voltage and frequency support. The criteria for comparison are based on the speed of the response, overloading capability, and performance in weak and strong grids. The idea was to test each technology and control strategy against voltage and frequency disturbance, voltage angle jump, and short circuit. Additionally, we proposed a VSC based damping controller for SSR torsional oscillations with support for multiple generator and multiple mode oscillation damping. The solution is integrated within the HSC system. The proposed controller acts as a supplementary function, which means that the HSC can provide all other functions listed previously with only a small capacity margin reserved for the SSR oscillation damping. The controller uses local voltage measurement as feedback for torsional oscillation identification and suppression. In the final chapter, we propose a solution to maximize the inertial contribution of the HSC system by utilizing energy storage to compensate the power swings caused by the synchronous condenser. The solutions have been tested and validated in power hardware in the loop.