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Penetration of equipment such as photovoltaic power generations (PV), heat pump water heaters (HP), and electric vehicles (EV) introduces voltage unbalance issues in distribution systems. Controlling PV and energy storage system (ESS) outputs or coordinated EV charging are investigated for voltage unbalance compensation. However, some issues exist, such as dependency on installed capacity and fairness among consumers. Therefore, the ideal way to mitigate unbalanced voltages is to use grid-side equipment mainly. This paper proposes a voltage unbalance compensation based on optimal tap operation scheduling of three-phase individual controlled step voltage regulators (3ϕSVR) and load ratio control transformer (LRT). In the formulation of the optimization problem, multiple voltage unbalance metrics are comprehensively included. In addition, voltage deviations, network losses, and coordinated tap operations, which are typical issues in distribution systems, are considered. In order to investigate the mutual influence among voltage unbalance and other typical issues, various optimization problems are formulated, and then they are compared by numerical simulations. The results show that the proper operation of 3ϕSVRs and LRT effectively mitigates voltage unbalance. Furthermore, the results also show that voltage unbalances and other typical issues can be improved simultaneously with appropriate formulations.
Akito Nakadomari; Ryuto Shigenobu; Takeyoshi Kato; Narayanan Krishnan; Ashraf Hemeida; Hiroshi Takahashi; Tomonobu Senjyu. Unbalanced Voltage Compensation with Optimal Voltage Controlled Regulators and Load Ratio Control Transformer. Energies 2021, 14, 2997 .
AMA StyleAkito Nakadomari, Ryuto Shigenobu, Takeyoshi Kato, Narayanan Krishnan, Ashraf Hemeida, Hiroshi Takahashi, Tomonobu Senjyu. Unbalanced Voltage Compensation with Optimal Voltage Controlled Regulators and Load Ratio Control Transformer. Energies. 2021; 14 (11):2997.
Chicago/Turabian StyleAkito Nakadomari; Ryuto Shigenobu; Takeyoshi Kato; Narayanan Krishnan; Ashraf Hemeida; Hiroshi Takahashi; Tomonobu Senjyu. 2021. "Unbalanced Voltage Compensation with Optimal Voltage Controlled Regulators and Load Ratio Control Transformer." Energies 14, no. 11: 2997.
High-voltage direct current (DC) transmission systems and multi-terminal direct current transmission systems are attracting attention for expanding the grid to promote introduction of renewable energy. Fault clearing in DC systems is difficult because there is no zero point of current. Hybrid circuit breakers are suitable for fault clearing in DC systems. Conventional hybrid circuit breakers have a hard-switching path that damages the switch. Hard switching damages the device and produces emissions due to harmonic noise. A novel resonant hybrid DC circuit breaker is proposed in this paper. The proposed circuit breaker reduces the damage to the switching device using soft switching due to the current zero point. The proposed circuit breaker is compared with conventional hybrid circuit breakers using numerical simulations. Interruption times and switching types of circuit breakers were compared. The simulation results of the fault clearing characteristics of the proposed breakers show that the proposed breakers have sufficient performance and are capable of stable reconnections in multi-terminal direct current transmission systems.
Ryo Miyara; Akito Nakadomari; Hidehito Matayoshi; Hiroshi Takahashi; Ashraf M. Hemeida; Tomonobu Senjyu. A Resonant Hybrid DC Circuit Breaker for Multi-Terminal HVDC Systems. Sustainability 2020, 12, 7771 .
AMA StyleRyo Miyara, Akito Nakadomari, Hidehito Matayoshi, Hiroshi Takahashi, Ashraf M. Hemeida, Tomonobu Senjyu. A Resonant Hybrid DC Circuit Breaker for Multi-Terminal HVDC Systems. Sustainability. 2020; 12 (18):7771.
Chicago/Turabian StyleRyo Miyara; Akito Nakadomari; Hidehito Matayoshi; Hiroshi Takahashi; Ashraf M. Hemeida; Tomonobu Senjyu. 2020. "A Resonant Hybrid DC Circuit Breaker for Multi-Terminal HVDC Systems." Sustainability 12, no. 18: 7771.
This paper presents a compensation method for unbalanced voltage through active and reactive power control by utilizing a smart inverter that improves the voltage unbalance index and detects an unbalanced state of voltage magnitude and phase, and thus enhances power quality by minimizing the voltage imbalance. First of all, this paper presents an analysis of a mathematical approach, which demonstrates that the conventional voltage unbalanced factor (VUF) using the symmetrical component cannot correctly detect the imbalanced state from index equations; and by only minimizing the VUF value, it cannot establish a balanced condition for an unbalanced state of the voltage profile. This paper further discusses that intermittent photovoltaic (PV) output power and diversified load demand lead to an unexpected voltage imbalance. Therefore, considering the complexity of unbalanced voltage conditions, a specific load and an PV profile were extracted from big data and applied to the distribution system model. The effectiveness of the proposed scheme was verified by comparing VUF indices and controlling the active and reactive power of a smart inverter through a numerical simulation.
Ryuto Shigenobu; Akito Nakadomari; Ying-Yi Hong; Paras Mandal; Hiroshi Takahashi; Tomonobu Senjyu. Optimization of Voltage Unbalance Compensation by Smart Inverter. Energies 2020, 13, 4623 .
AMA StyleRyuto Shigenobu, Akito Nakadomari, Ying-Yi Hong, Paras Mandal, Hiroshi Takahashi, Tomonobu Senjyu. Optimization of Voltage Unbalance Compensation by Smart Inverter. Energies. 2020; 13 (18):4623.
Chicago/Turabian StyleRyuto Shigenobu; Akito Nakadomari; Ying-Yi Hong; Paras Mandal; Hiroshi Takahashi; Tomonobu Senjyu. 2020. "Optimization of Voltage Unbalance Compensation by Smart Inverter." Energies 13, no. 18: 4623.
Optimal sizing of power systems has a tremendous effective role in reducing the total system cost by preventing unneeded investment in installing unnecessary generating units. This paper presents an optimal sizing and planning strategy for a completely hybrid renewable energy power system in a remote Japanese island, which is composed of photovoltaic (PV), wind generators (WG), battery energy storage system (BESS), fuel cell (FC), seawater electrolysis plant, and hydrogen tank. Demand response programs are applied to overcome the performance variance of renewable energy systems (RESs) as they offer an efficient solution for many problems such as generation cost, high demand peak to average ratios, and assist grid reliability during peak load periods. Real-Time Pricing (RTP), which is deployed in this work, is one of the main price-based demand response groups used to regulate electricity consumption of consumers. Four case studies are considered to confirm the robustness and effectiveness of the proposed schemes. Mixed-Integer Linear Programming (MILP) is utilized to optimize the size of the system’s components to decrease the total system cost and maximize the profits at the same time.
Mahmoud M. Gamil; Makoto Sugimura; Akito Nakadomari; Tomonobu Senjyu; Harun Or Rashid Howlader; Hiroshi Takahashi; Ashraf M. Hemeida. Optimal Sizing of a Real Remote Japanese Microgrid with Sea Water Electrolysis Plant Under Time-Based Demand Response Programs. Energies 2020, 13, 3666 .
AMA StyleMahmoud M. Gamil, Makoto Sugimura, Akito Nakadomari, Tomonobu Senjyu, Harun Or Rashid Howlader, Hiroshi Takahashi, Ashraf M. Hemeida. Optimal Sizing of a Real Remote Japanese Microgrid with Sea Water Electrolysis Plant Under Time-Based Demand Response Programs. Energies. 2020; 13 (14):3666.
Chicago/Turabian StyleMahmoud M. Gamil; Makoto Sugimura; Akito Nakadomari; Tomonobu Senjyu; Harun Or Rashid Howlader; Hiroshi Takahashi; Ashraf M. Hemeida. 2020. "Optimal Sizing of a Real Remote Japanese Microgrid with Sea Water Electrolysis Plant Under Time-Based Demand Response Programs." Energies 13, no. 14: 3666.