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Voltage source converter (VSC) has been extensively used in power systems for interfacing renewable energies and other modern loads. Because of the nonlinear nature, it is important to establish a proper harmonic model of VSC devices when con-ducting harmonic analysis in power systems. This is especially true for low-order harmonics which are routinely encountered in present power systems. To this end, an analytical harmonic model that represents the low-order harmonic characteristics of the VSC is developed in this paper. The new model takes both the control loop and power loop (i.e., dc-link capacitor) of the VSC into account through rigorous mathematical derivations. The final result has shown that the VSC can be represented by a coupled impedance matrix at harmonic frequencies, which can be easily used for harmonic analysis in large-scale power systems. It also shows that the dc-link capacitor has a more noticeable impact on the harmonic impedance of VSC with a smaller dc-link capacitance and low-order harmonics. The correctness of the new model has been verified using EMT simulations and lab experiments. A complete procedure to construct the proposed VSC model is also established based on the research findings.

This paper presents an online method to monitor the conditions of substation grounding grid. The proposed method utilizes phase-to-ground faults occurring in downstream feeders as test current sources and the neutral of a specially selected feeder as the electrode for GPR (ground potential rise) measurement. The measured fault currents and GPRs are then used to estimate substation grounding grid impedance. The method, once established, can monitor the grounding grid impedance continuously and automatically, and the trend of the impedance change can be observed. As a result, the proposed method can yield much more reliable information on the substation grounding conditions. The method also overcomes many disadvantages of the offline methods. The proposed idea, algorithm, and hardware setup are described in the paper. Factors contributing to measurement errors are investigated in detail.

Adding a damping unit to a shunt capacitor is an effective way to mitigate capacitor-caused resonance. However, damping units suffer from power loss issues. This shortcoming is amplified further in cases where resonance has a low possibility of occurring. In view of this, an adaptive damping method is proposed to improve the existing scheme. The damping unit is capable of mitigating resonance and eliminating the power loss under the non-resonance condition. The core idea of the proposed approach is to add a breaker so that the damping unit can be switched on or off depending on whether resonance occurs. The design of and control mechanism for the proposed switchable damping unit are presented. The performances of the new resonance mitigation scheme in terms of harmonic mitigation, loading, switching transient and cost are verified for an actual capacitor application case.

Voltage and current waveforms contain the most authentic and granular information on the behaviors of power systems. In recent years, it has become possible to synchronize waveform data measured from different locations. Thus large-scale coordinated analyses of multiple waveforms over a wide area are within our reach. This development could unleash a set of new concepts, strategies, and tools for monitoring, protecting, and controlling power systems and apparatuses. This paper presents an in-depth review and analysis of the advancements in synchronized waveform data, including measurement devices, data characteristics, use cases, and comparisons with synchrophasor data. Based on the findings, five strategies are proposed to discover and develop synchronized waveform based applications over multiple application areas. The paper also presents three complementary measurement platforms and two data screening algorithms for application implementation. It further discusses committee activities and standard developments useful to explore the full potential of the data.

Voltage source converter (VSC) based devices have become widely accepted by the power industry in recent years as a result of renewable energy initiatives and other developments. Due to their nonlinear v~i characteristics, it is essential to understand and model the harmonic impact of VSC devices in a power system. In response to such a need, this paper proposes a rigorous harmonic model of VSC devices suitable for harmonic power flow studies of large-scale power systems. Through detailed mathematical derivations, this research has shown that the model takes the form of a coupled frequency-dependent impedance matrix. Formulas to compute the impedance elements have been established. The results show that the impedance is independent of the harmonic voltages experienced by the VSC device, and thus it can be easily integrated into existing harmonic power flow tools. The accuracy of the model, as well as its usefulness for harmonic power flow studies, have been verified using EMT simulations.

Detection of open conductor condition in a system with unloaded ${{{\bf Y}}_{{\bf g}}}$ connected primary transformers has been a challenging task. This is due to the lack of detectable abnormal voltage and current responses when a conductor opens. This paper recognizes that the above situation is related to the positive sequence nature of the supply voltage. If the supply voltage were in zero-sequence, an open conductor would result in distinct voltage and current responses. Based on this understanding, a relaying scheme that uses the 3rd harmonic power is proposed to solve the open conductor detection problem. The 3rd harmonic is known to be dominant in zero-sequence and it exists in various parts of a power system. Performances of the proposed method have been evaluated using simulation and experimental studies. The proposed scheme can be easily implemented using a relay similar to the zero-sequence power relay. Extensive study results show that the proposed method is a promising technique to solve the open conductor detection problem.

Configuring a shunt capacitor as a detuned C-type filter is an effective way to mitigate the capacitor caused harmonic resonance. A design method has been developed recently that can guarantee the damping performance of the filter even if the system impedance data is not available. This article further improves the design method by considering the case where the system impedance data is available. It also answers the question if cost can be reduced by utilizing known system impedance data. For this purpose, the cost and power loss characteristics of the filter are investigated and included in the design. The performance of various design methods is compared from the perspectives of resonance-mitigation, power loss, cost, and robustness. The results have shown that the system independent design leads to superior performance except for the power loss. A guide on how to design the detuned C-type filter is recommended.

Single-point bonding for cable sheath is a widely used method to increase cable ampacity. The method requires a dedicated grounding continuity conductor (GCC), which adds to the cost of implementation significantly. This letter proposes a new bonding method, called single-sheath bonding, to overcome the disadvantage of the single-point bonding method. The key idea is to use one of the sheaths as the GCC. The resulting configuration has a performance similar to that of the single-point bonding method but at a much lower cost. Feasibility study shows that this is a very attractive bonding method that has the potential to replace both single-point bonding and cross-bonding methods.