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Sustainable development of power and energy systems (PES) can effectively handle challenges of fuel shortage, environmental pollution, climate change, energy security, etc. Data of PES presents distinctive characteristics including large collection, wide coverage, diverse temporal and spatial scales, inconsistent sparsity, multiple structures and low value density, putting forward higher requirements for real-time and accuracy of data analysis, and bringing great challenges to operation analysis and coordinated control of PES. In order to realize data quality improvement and further support flexible choice of operating mode, safe and efficient coordinated control, dynamic and orderly fault recovery of sustainable PES, this paper proposes an unscented particle filter algorithm, adopting unscented Kalman filter to construct importance density functions and KLD resampling to dynamically adjust the particle number. Simulation results obtained by taking an 85-node system as a benchmark for simulation verification show that compared with traditional PF algorithm and UKF algorithm, UPF algorithm has higher estimation accuracy.

Virtual synchronous control has been widely studied for the advantages of emulating inertia for voltage source converters (VSCs). A constant dc-link voltage is usually assumed in existing literature to estimate transient stability of virtual synchronous generators (VSGs). However, actual power supply in the dc-side of VSGs is limited and different dc-link voltage controllers are needed to achieve power balance between DC side and AC side. Addition of dc-link voltage controller has great influence on transient behavior of VSGs, which has not been investigated by previous research. To fill this gap, this paper gives insights into the effect of dc-link voltage dynamics on transient stability of VSGs. First, two typical kinds of VSGs with dc-link voltage controllers are introduced. Then, mathematical models considering dc-link dynamics are established and the effect of dc-link voltage controllers on transient synchronization stability of VSGs is revealed through equal area criterion (EAC). It is found that dc-link voltage controller would reduce stability margin of VSGs and design-oriented transient stability analysis is carried out quantitively using critical clearing time (CCT). Finally, simulation results are given to validate correctness of theoretical analysis.

The use of frequency-changers is widespread in daily electric power generation. If a frequency-changer could automatically adjust its power output according to the load status and power network operation, it would have a positive impact on power system stability. To achieve this a novel control strategy based on virtual synchronous motors (VSM) is proposed in this paper. The frequency-changer consists of two main parts: the rectifier and the inverter. In the rectifier part, a UDC-Q control strategy is adopted to control the DC-link voltage and the reactive power. In the inverter part, a VSM control strategy is used; it includes a power-frequency controller and an excitation controller, and can change the inverter's output frequency and voltage with the variation of load, can adjust the active power with change of the power system frequency. The proposed control strategy is simulated using Simulink/Matlab. The simulation results show that the proposed control strategy can follow the mechanical inertia and electrical characteristics of the synchronous moto and can effectively improve the system power quality and system stability.