In recent years, the proliferation of renewable generations significantly increases the severity and possibility of subsynchronous oscillations (SSO). These events can result in significant loss of generation and impose great threats to the system stability and equipment safefy. Accurate knowledge of SSO parameters (SSO frequency, magnitude and damping) is crucial for its effective mitigation. This paper presents a method to identify SSO parameters based on synchrophasors. The basic idea is to estimate SSO parameters by analyzing the spectral leakage information of SSO in synchrophasors. To achieve this, an interpolated discrete fourier transform is first adopted to accurately determine the frequency and damping of SSO. Afterwards, the magnitude of SSO can be calculated with the help of Hann-window. Case studies demonstrate that the proposed algorithm can accurately determine the SSO frequency, damping, and current magnitude. The performance has also proved to remain satisfactory under off-nominal, dynamic and noisy conditions. Moreover, comparative studies with the existing method show the superiority of the proposed method. This technique is thus a promising tool for online monitoring of SSO in actual power systems.

Virtual synchronous generators (VSGs) have been proved to be important means to provide the inertia for future power systems. However, it suffers the issue of active power oscillation under various disturbances. In this paper, a robust damping control is proposed to mitigate the active power oscillation by reshaping the oscillation energy of VSGs. The paper first represents the power-angle dynamics of VSGs as an equivalent circuit and thus enables the understanding of oscillations from the circuit energy. It is revealed that the active power oscillation can be comprehended as an LC resonance and the damping provided by the traditional VSG is commonly insufficient. To tackle this issue, a robust damping method is proposed using interconnection and damping assignment passivity-based control (IDA-PBC). The theory of IDA-PBC is established based on the concept of energy reshaping, which guarantees the state tracking via its intrinsic energy dissipation characteristics. The IDA-PBC, when applied to VSGs, is a combination of the disturbance compensation via feedforward channels and the deviations regulation through feedback paths. Noticeably, the disturbance compensation is achieved with the support of an extended state observer (ESO), which can accurately estimate the lumped disturbance including the grid frequency variation and the model uncertainties. A guideline on the parameter selection is also provided through Bode-plot analysis. Finally, the effectiveness and merits of the proposed method is verified by hardware in the loop-based experiments with the comparison to the state of art work.

Identifying sources of subsynchronous resonance (SSR) is crucial for understanding and mitigating incidents. Recent studies have shown that SSR impedance and power are effective indicators that can identify an SSR source. However, the calculation of two indexes requires SSR voltage and current phasors as the inputs, which are not directly available from existing online monitoring systems. To address this issue, this paper presents a novel method to calculate SSR impedance/power based on synchrophasors provided by a wide-area monitoring system. As a result, the online detection of SSR sources is enabled. Through mathematical derivation, it is revealed that a synchrophasor under SSR is dominated by four modes: two from the fundamental frequency and two from the SSR frequency. The problem thus can be transformed to a modal parameter extraction (MPE). Two classic MPE algorithms, Prony analysis and the matrix pencil method, are employed in this paper to extract the SSR parameters and calculate the SSR impedance/power. Their performances are verified using synthetic signals and electromagnetic transient simulations. Furthermore, the method is applied to an actual SSR incident involving 23 wind farms. The findings suggest that 17 of 23 wind farms did not contribute negative damping to the oscillation.

Harmonic distortions at a point of common coupling (PCC) are caused by the harmonic sources in both supply system and customer facilities. In order to verify compliance with harmonic limits for an operating facility, it is essential to determine the contribution of a facility to the harmonic distortions measured at the PCC. Over the past many years, a significant amount of research work has been conducted in developing different harmonic analysis methods, and especially harmonic contribution assessment methods. A common need of this line of research is consistent test systems that can be used to verify/validate a proposed method or to compare different approaches. To address this gap, a benchmark test system representing a typical MV/LV network supplying industrial loads, is proposed in this paper. The paper also includes examples on how to use the system to assess the performance of harmonic contribution determination methods.

Accurate harmonic state estimation (HSE) is necessary to mitigate harmonic issues in power distribution networks. However, existing HSE methods face difficulties in solution of state equation that the measured data is insufficient with limited monitors. Therefore, this study proposes a HSE algorithm for distribution networks based on multi-measurement data. Firstly, a harmonic source location method based on mutual information and distribution network partition is proposed to reduce the number of state variables and to solve the state equation. Thus, HSE with low resolution (15 min) is realized. Secondly, a HSE method with enhanced resolution is developed. This method establishes maximum entropy principle models for harmonic currents injected into buses, calculates the probability density function (PDF) of the harmonic current, and realizes optimal interpolation of the harmonic data to enhance the resolution of the HSE (3 min) according to the PDF. Finally, the applicability and effectiveness of the proposed method are verified using an IEEE-33 test system simulation and a real power system in South China.

With the continuous advancement of energy transformation, the flexibility of the power system is becoming increasingly important due to the intermittent and uncertain nature of variable renewable energy. Concentrated Solar Power (CSP) is an emerging reliable and dispatchable renewable generation technology that integrates “sunlight-heat-electricity” conversion, large-scale thermal energy storage, and synchronous machine characteristics. This enables CSP to provide reliable peak-shaving, inertia support, and spinning reserve services for the power system, thereby playing an increasingly significant role in achieving a highly renewable power system. Concentrated solar power (CSP) is playing a more important role in realizing a highly renewable penetrated power system. However, the lack of a suitable dynamic CSP plant model hinders its power system dynamic studies. In this article, a delicate and efficient model of a CSP plant is proposed by considering its special energy supply mode, component structure, and control system. The model can accurately reflect the influences of salt temperature on power plant dynamic characteristics at off-design conditions. Besides, a complete model parameter calculation scheme is developed to derive the model parameters from the basic physical dimensions of components and rated operation information. The performances of the proposed model and parameter calculation scheme have been fully evaluated with field data and structural information from a real-life 50MW linear Fresnel CSP plant located in northwest China. The results indicate that the proposed model can effectively simulate the dynamic behavior of the CSP plant with a low computational cost.