Constructing new-type power systems is a key goal for the transformation of the power industry in China. It is also essential for achieving the objectives of carbon peaking and carbon neutrality. This paper explores the establishment of new-type power systems from a different perspective, drawing inspiration from ongoing practices and existing discussions. In this paper, we summarize the current status and challenges of traditional power systems firstly to identify the key issues that require resolution. Next, this paper traces the evolving trajectory of the power system to seek the motivation for further development. Then, this paper examines several topics of general interest, including inertia and system strength, to reveal the inherent causes of technical challenges. Finally, this paper brings out a proposal of development for a new-type power system, clarifying its main characteristics and key technologies that require further in-depth research.

Traditionally, synchronous generators are equipped with power system stabilizers (PSSs) to stabilize electromechanical low-frequency oscillations (LFOs). With increasing applications of converter-based devices in modern power systems, system-wide control interactions between different converter-based devices are causing more prevalent electromagnetic wideband oscillations (WBOs). Extensive research has been done on design, application, and standardization of classical PSSs for addressing LFOs associated with synchronous generators. However, little attention is given to same for converter-based devices as a countermeasure to electromagnetic WBOs. This paper proposes a concept of utilizing new-type power system stabilizers (NPSSs) specifically designed to address WBOs caused by converter-control interactions in modern converter-dominated power systems. The article puts forward various design strategies, tuning methods, and implementation techniques of the NPSSs to counteract WBOs. The NPSSs are not limited to inverter-based resources (type-3/4 wind turbines); they can also be applied to other converter-based devices such as FACTS controllers, HVDC links, battery storage inverters, etc. We present several application scenarios demonstrating the importance of supplementing NPSSs in converter-based devices. Furthermore, the paper highlights current research challenges and opportunities in designing and implementing NPSS for various converter-based devices, providing a comprehensive overview of state-of-the-art and future directions in this area.

Connecting converter-based renewable power generators (RPGs) to the power grid can cause serious sub-/super-synchronous oscillations (SSO). Changes in the operating conditions, grid strengths, and converter control can cause the SSO frequency to gradually approach the fundamental frequency while then leads to low-frequency small-signal synchronizing stability (SSS) oscillations. This paper compares the characteristics of SSO and SSS oscillations using the impedance model (IM)-based method that has been used to analyze SSO and is believed to be useful for analyzing the low-frequency oscillations caused by synchronous instabilities. Then, a mathematical model is used to show the equivalence between the phase-locked loop (PLL) dynamic equation-based method and the IM based method for the same grid-tied voltage source converter (VSC) system as a theoretical foundation for SSS analyses using the IM-based method. Finally, time-domain simulations verify the accuracy of the IM-based method for analyzing SSS oscillations of converter-based RPGs.