A recent study published in Engineering delves into the power response characteristics of networks when excited by voltage with time-varying amplitude and frequency (TVAF). This research, led by Yingbiao Li and colleagues from various institutions, addresses a crucial gap in understanding the behavior of power systems in the era of increasing power electronic equipment integration.

With the growing prominence of renewable energy power generation and grid-connected electronic equipment, the traditional assumptions in power system analysis are being challenged. In a traditional power system dominated by synchronous generators (SGs), the amplitude and frequency of the internal voltage are relatively stable. However, power electronic equipment, with its low inertia characteristics, causes the node voltage to exhibit TVAF during dynamic processes. This change renders traditional calculation methods based on phasor and impedance invalid.

The researchers employed mathematical calculations, relying on original mathematical relationships and superimposed step response, to reveal the network power response under TVAF voltage excitation. They first analyzed the current response of a one-node inductance network. By establishing a vector model of the voltage and performing mathematical calculations, they derived an expression for the current response. The physical characteristics of the current response showed that its amplitude and frequency are time-varying and related to the voltage’s time-varying terms and higher-order differentials.

Subsequently, the multi-timescale characteristics of the power response in a one-node inductance network were explored. Considering the sinusoidal modulation of the voltage’s amplitude and frequency, the researchers found that both the active and reactive power are time-varying. The active power comprises five types of frequency components, and the reactive power contains a time-invariant component and a time-varying component. Under TVAF voltage excitation, an active power storage and release process occurs in the inductance network, and the energy exchanged between the three phases increases.

To meet practical engineering requirements, the researchers also proposed a simplified calculation method. By determining the convergence interval of the current series, they obtained a simplified current expression that retains the dominant current components. This expression has a concise form and can accurately reflect the influence of TVAF on the current. Based on this, simplified expressions for active and reactive power were derived.

The power characteristics in a two-node inductance network were also analyzed. The results showed that the transmitted active and reactive power are related to the amplitude, phase, and differentials of the voltages at both ends, as well as the phase angle difference between the voltages.

Finally, the researchers validated their theoretical analysis through time-domain simulations using the PSCAD software. The simulation results demonstrated the accuracy of the proposed current and power equations and the multi-timescale characteristics of the network power under TVAF voltage excitation.

This study provides valuable insights into the power response of networks under TVAF voltage excitation. The findings can help engineers better understand and analyze power system dynamics, which is crucial for ensuring the stability and reliability of modern power systems.

The paper “A Multi-Timescale Characteristics Analysis of the Network Power Response Excited by Voltage with Time-Varying Amplitude and Frequency,” authored by Jiabing Hu, Weizhong Wen, Yingbiao Li, Xing Liu, Jianbo Guo. Full text of the open access paper: https://doi.org/10.1016/j.eng.2024.12.015. For more information about the Engineering, follow us on X (https://twitter.com/EngineeringJrnl) & like us on Facebook (https://www.facebook.com/EngineeringJrnl).