At present, the electric vehicle (EV) market is developing strongly and widely across many countries around the world. Increasing clean energy infrastructure for EVs is a possible solution to reduce greenhouse gas emissions and help improve air quality in urban areas. Electric vehicles charged by electricity from photovoltaic (PV) systems can produce less emissions than conventional EVs charged by the utility grid. Thus, the combination of solar power and EV charging stations is one of the possible methods to achieve sustainable development in the current EV market. EVs in cities in Vietnam have developed very quickly in recent times, but the charging station infrastructure is still very limited, and most existing charging stations use electricity from the utility grid. In this paper, the optimal configuration of PV-powered EV charging stations is analyzed technically and economically under different solar irradiation conditions in Vietnam. The study results show that the optimal configuration and investment efficiency of PV-powered EV charging stations in each urban area are greatly affected by the solar irradiation value and feed-in tariff (FIT) price of rooftop solar power. In Vietnam, a region with high solar irradiation, such as Ho Chi Minh, is more likely to invest in PV-powered EV charging stations than other areas with lower solar irradiation, such as Hanoi.

With the average solar radiation reaching up to 5 kWh/m², Vietnam is considered as a country showing an excellent potential for solar power production. Since the year 2000, there have been a lot of studies about the potential of this source in Vietnam. So far, many applications of solar power have been implemented on small, medium, and large scales. In fact, the total capacity of current grid-connected solar power plants has exceeded the planned capacity by 2020 nearly 6 times. However, the studies of solar potential in Vietnam are still incomplete. The policies and mechanisms for developing solar power projects have received attention from the authorities but have not been really satisfactory. The infrastructure is still poor and the power system does not keep up with the development of modern grids. This paper reviewed the potential and actual implementation stage of photovoltaic projects in Vietnam. Moreover, the barriers and challenges of institution, technique, economy, and finance have been considered explicitly for the future development of solar energy in Vietnam.

Vietnam became the world’s third largest market for solar photovoltaic energy in 2020. Especially after the Vietnamese government issued feed-in tariffs for grid-connected solar photovoltaic systems, the installed capacity of solar photovoltaic applications exploded in 2019. From studies carried out in the relevant literature, it can be said that support policies are highly important for the initial development of the renewable energy industry in most countries. This is especially true in emerging countries such as Vietnam. This paper reviews the feed-in tariffs issued and deployed in different regions of Vietnam for grid-connected solar photovoltaic applications. Moreover, the paper takes a closer look at the costs of electricity production from these systems in relation to the feed-in tariffs issued in Vietnam. The results show that the gap between the levelized cost of electricity and the feed-in tariff for solar photovoltaic electricity is relatively high, particularly in regions with a lower irradiation potential.

In modern power systems, the increasing penetration of renewable energy resources has reduced frequency stability. Consequently, wind turbines (WTs) are expected to participate in frequency regulation. By integrating the electrostatic energy stored in the DC capacitor with the kinetic energy stored in the rotating mass of the WT, an advanced control method is implemented to facilitate frequency regulation. However, previous studies have mainly concentrated on frequency control using WTs but ignored the rotor speed recovery of WT. Therefore, this work proposes a novel control strategy that separates the operating mode of a WT into two distinct states: the frequency support and the recovery of rotation speed stages. The proposed method improves the recovery process for rotor speeds after a WT participates in frequency support, returning the WT quickly to its normal operation to reduce wind energy loss. Furthermore, a new adaptive DC virtual inertia (DVIC) coefficient that utilizes real-time DC voltage to adjust the DVIC’s output smoothly is proposed. The proposed strategy is compared with other mature control strategies and implemented in PSCAD/EMTDC to verify their effectiveness and robustness. The simulation results demonstrate that the proposed method outperforms other mature methods because it reduces wind energy loss by at least 15 % when WTs participate in the frequency support process.

The increasing integration of renewable energy sources (RESs) into the power system reduces system inertia, which presents substantial challenges for maintaining frequency stability. Existing studies have mainly focused on using the load frequency control method (LFC) to stabilize area frequency and tie-line power by optimizing the parameters of supplementary control for synchronous generators (SGs). However, these works primarily used simplified first-order transfer functions for wind turbines (WT), high-voltage direct current (HVDC), and battery energy storage systems (BESS). They neglected dynamic models and, importantly, the impact of control parameters in supplementary frequency control strategies on the stability of the studied system. Therefore, this study proposes a novel load frequency control strategy that coordinates the operation of WT, HVDC, and BESS in conjunction with traditional SGs to participate in frequency regulation. The proposed strategy develops a comprehensive state-space model that incorporates accurate models of WT, HVDC, BESS, and SGs, along with their supplementary control strategies. Then, the developed state-space model was utilized to investigate the impact of control parameters in the supplementary frequency control strategies of BESS, HVDC, and WT on system stability. As a result, this work yields a specific range of coefficients for supplementary strategies to improve stability in the studied system. Lastly, a two-area interconnected benchmark system is adopted to validate the effectiveness of the proposed strategy. Based on the suggested parameters, the results demonstrate that the proposed strategy ensures frequency stability with a high penetration of RESs into the power grid. Furthermore, the results indicate that incorporating diverse sources, such as HVDC, WT, and BESS, to support SGs in frequency regulation reduces the impacts of low system inertia. This approach leads to an improved frequency response not only in areas where disturbances occur but also in other regions, provided that tie-line power interchanges are maintained in balance.

This study introduced a novel control approach based on fuzzy logic control (FLC) to enhance the frequency regulation capacity of variable-speed wind turbines (VSWTs). The proposed method integrates FLC within droop and inertia control loops. Real-time measurements of the system frequency and the rate of change of frequency (ROCOF) serve as inputs to the FLC, enabling the method to improve the frequency response by VSWTs. In addition, the method employs FLC for pitch angle frequency control, optimizing reserve power for frequency regulation under varying wind speed levels. The innovative aspect of this study lies in the simultaneous application of FLC to pitch angle frequency control and droop/inertia control, leading to the enhanced frequency regulation capability of VSWTs and smoother operation across a range of wind speeds. Compared with traditional methods, the proposed approach provides a comprehensive and effective solution to the challenges associated with frequency regulation in VSWTs. Through simulations across different wind speed scenarios, the proposed control method demonstrated the best performance among various mature methods, highlighting the efficacy of the proposed method on the frequency regulation of VSWTs under different wind speeds. This study’s findings highlight the potential of the proposed FLC-based method to optimize frequency regulation and contribute to more reliable and efficient wind energy systems.