Owing to the fast and large power regulating the capacity of the HVDC system, the wide-area measurement system (WAMS) based high voltage direct current (HVDC) system has been regarded as a prospective solution to deal with the low-frequency oscillation issue. However, due to the vulnerability of the WAMS communication, WAMS based HVDC system control can be a prime target of malicious penetrations that could lead to disastrous events. To remediate this adverse effect, an improved WAMS based HVDC damping control framework is proposed. First, a lightweight network named Attack Shuffle convolutional neural Networks (ASNet) is proposed to learn the characteristics of cyber attacks. Then, a model-free-based cyber attack defense framework is introduced to quickly identify the attack types based on the continuous wavelet transform and ASNet. Additionally, an improved control framework of the WAMS and HVDC-based wide-area power oscillation damping control (WH-PODC) is developed to provide different response control for mitigation of the impact of cyber attacks. Finally, the performance of the proposed WH-PODC control framework is evaluated with real PMU data in multiple scenarios in RTDS, where the results indicate that the response intensity can be kept under multiple types of cyber attacks while providing similar effectiveness in oscillation suppression to conventional controls.

Replacing expensive IGBT with thyristor to design dc circuit breaker (dcCB) is attracting attention recently due to its advantages in terms of low investment and low conduction loss. However, due to the half-controlled characteristic of thyristor, the existing thyristor-based dcCBs (T-CBs) cannot be actively turned off. As a result, the opening process is not fully controllable and reliable. In this letter, a simple active T-CB (AT-CB) topology is proposed. The proposed AT-CB can interrupt both fault current and operation current actively, and the current breaking process is fast, reliable, and fully controllable. Moreover, the proposed AT-CB can be improved to be bidirectional without increasing the conduction loss, and the topology remains simple. Parameters design principle and operation process of AT-CB are presented. Scaled-down experiment verified the effectiveness of the proposed solution.

Due to the heavy stress on environmental deterioration and the excessive consumption of fossil resources, the transition of global energy from fossil fuel energy to clean energy has significantly accelerated in recent years. The power industry and policymakers in almost all countries are focusing on clean energy development. Thanks to progressive clean energy policies, significant progress in clean energy integration and greenhouse gas reduction has been achieved around the world. However, due to the differences in economic structures, clean energy distributions, and development models, clean energy policy scope, focus, and coverage vary between different countries, states, and utilities. This paper aims at providing a policy review for readers to easily obtain clean energy policy information on various clean energies in the U.S. and some other countries. Firstly, this paper reviews and compares some countries’ clean energy policies on electricity. Then, taking the U.S. as an example, this paper introduces the clean energy policies of some representative states and utilities in the U.S in perspectives of renewable energies, electric vehicles, and energy storage.

The station-hybrid HVDC system combining diode rectifier unit (DRU) and modular multilevel converter (MMC) in parallel has garnered significant attention within the field of light-duty HVDC systems. This paper presents a comprehensive investigation into the control and capacity design of this station-hybrid scheme. Firstly, a coordinated power control strategy is presented to provide grid-forming capability and mitigate transmission losses. In addition, a software-based harmonic suppression strategy is introduced. This innovative approach eliminates the need for additional hardware filters in the DRU, streamlining the system while effectively suppressing unwanted harmonics. Moreover, the capacity of the station is meticulously designed to optimize overall system performance. An economic evaluation is conducted to compare the proposed station-hybrid scheme with the conventional compact MMC scheme, shedding light on the economic feasibility and competitiveness of the proposed configuration. Finally, the paper validates the proposed coordinated power control and harmonic suppression strategy through simulations using the PSCAD platform. The results confirm the practicality and effectiveness of these control strategies in real-world applications.

With the continuous increase of renewable energy generation and high voltage direct current (HVDC) power transmission, the system inertia is declining, thus resulting in greater risks of frequency instability. To solve this issue, a dc‐link inertia control is firstly proposed for a point‐to‐point modular multilevel converter based HVDC (MMC‐HVDC) link, which enables the MMC‐HVDC system to provide emulated inertia support by employing the electrostatic energy stored in the dc capacitors. Moreover, in order to maintain reasonable submodule capacitor size as well as provide more emulated inertia support, a virtual capacitor control for MMC‐HVDC connected an offshore wind farm (OWF) is proposed. With the virtual capacitor control, the OWF is able to provide a large capacity virtual capacitor in dc side of MMC‐HVDC link and supply desired emulated inertia support for onshore power system by utilising the offshore wind turbines’ rotor rotational kinetic energy. Furthermore, a procedure for selecting the appropriate virtual capacitor control parameters is proposed. Finally, the performance of the proposed coordinated control is researched in PSCAD/EMTDC, and the simulation results show that the onshore power system inertia is effectively improved with the coordinated control.

Distribution System State Estimation (DSSE) infers the states (e.g., voltage phasors) using measurements from the electric distribution grid. As the distribution network becomes more active due to the increasing penetration of Distributed Energy Resources (DER), a deeper investigation into conventional DSSE approaches is needed. This review paper focuses on state-of-the-art techniques and challenges for DSSE in the context of emerging concepts, such as new sensor technologies, data-driven approaches, and high DER penetration.