Tomonori Goya

A Coordinated Control Method to Smooth Wind Power Fluctuations of a PMSG-Based WECS

This paper presents an output power smoothing method by a simple coordinated control of DC-link voltage and pitch angle of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG). The WECS adopts an AC-DC-AC converter system with voltage-source converters (VSC). The DC-link voltage command is determined according to output power fluctuations of the PMSG. The output power fluctuationsin low- and high-frequency domains are smoothed by the pitch angle control of the WECS, and the DC-link voltage control, respectively. By using the proposed method, the wind turbine blade stress is mitigated as the pitch action in high-frequency domain is reduced. In addition, the DC-link capacitor size is reduced without the charge/discharge action in low-frequency domain. A chopper circuit is used in the DC-link circuit for stable operation of the WECS under-line fault. Effectiveness of the proposed method is verified by the numerical simulations.

A Hybrid Smart AC/DC Power System

Recently, smart grids are attracting attention. Already, a smart grid based on an AC grid is proposed. However, no study on research is presented or published on a smart grid based on a dc grid. This paper presents an ac/dc hybrid smart power system. The proposed system has advantages of both dc and ac grids. The proposed power system consists of a wind generator and several controllable loads. The controllable loads have different capacities. Therefore, by applying power consumption control with the droop characteristic, the dc bus voltage is maintained within the acceptable range. As controllable loads, electric water heater and electric vehicle are assumed. Effectiveness of the proposed method is verified by numerical simulation results.

Optimal Operation by Controllable Loads Based on Smart Grid Topology Considering Insolation Forecasted Error

From the perspective of global warming mitigation and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all electric apartment houses or residence such as dc smart houses are increasing. However, due to the fluctuating power from renewable energy sources and loads, supply-demand balancing of power system becomes problematic. The smart grid is a solution to this problem. This paper presents a methodology for optimal operation of a smart grid to minimize the interconnection point power flow fluctuation. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuation, it is possible to reduce the electric power consumption and the cost of electricity. This system consists of a photovoltaic generator, heat pump, battery, solar collector, and load. To verify the effectiveness of the proposed system, results are used in simulation presented.

Optimal operation of smart grid in isolated island

From the perspective of global warming suppression and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic facility (PV) are getting attention in distribution systems. On the other hand, the introduction of an all-electric house is increasing in the world. So the controllable load such as electric water heater, heat pump, and electric vehicles are introduced to the power system. In addition, controllable load such as electric water heater, heat pump, and electric vehicles could accomplish to shift the high demand in daytime to the low demand in nighttime and it is effective method for leveling the load and upgrading the load factor. The authors propose an optimization approach to determine operational planning of WG, PV facility, diesel generator (DG), and battery energy storage system (BESS). In this optimization approach, it is assumed that forecast data of wind speed, solar insolated, and load demand are available. The proposed method uses tabu search and genetic algorithm for optimization method. Optimizing procedure is divided by two patrs. Firstly, actual load is controlled by controllable load. Secandly, the schedule of diesel generator units commitment problem is decided in the revised load. The simulation results show the reduction of operational cost.

Frequency control strategy for parallel operated battery systems based on droop characteristics by applying H ∞ control theory

Stand alone ac power supply system like that is designed for isolated islands is subjected to large frequency and voltage fluctuations caused by power deviation of wind turbine generator and load demand. An autonomous decentralized frequency control system of parallel operated decentralized generators based on droop characteristic is presented in this paper. The conventional droop control methods proposed in past researches exhibit slow and oscillating dynamic responses. Moreover, the conventional droop control is affected by measurement noise when the fast controllability of the system is emphasized. This paper proposes the improved droop control system for load sharing of multi operated decentralized generators by applying H∞ control theory, improving transient response of droop control and robustness against measurement noise and parameter variations. Simulation results validate the effectiveness of the proposed control system.

Output power smoothing of PMSG-based wind energy conversion system

This paper presents a control method for output power smoothing of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG) using the inertia of wind turbine and pitch control. The WECS used in this paper adopts an AC-DC-AC method with voltage-source converters (VSC). The generator-side converter controls the generator torque of the PMSG, while the grid-side inverter controls the DC-link voltage and the grid voltage, respectively. In the generator-side converter, the generator torque command is determined by using a fuzzy logic. By means of the proposed method, the generator torque is smoothed and the kinetic energy can be utilized to smooth the output power fluctuations of the PMSG. The effectiveness of the proposed method is validated by numerical simulations.

Optimal operation of controllable load and battery considering transmission constraint in smart grid

Recently, the deregulation and liberalization in power market increase the competition in retail and power sector. Therefore, power company needs to reduce operational cost and maximizes the profit by operating generator with higher efficiency. On the other hand, energy consumption is increasing rapidly due to the proliferation of all-electric houses. So the controllable load such as electric water heater, heat pump and electric vehicles are introduced to the power system. However conventional system does not operate the thermal unit and controllable load in a coordinated manner. This paper focuses on operating the controllable load, battery and thermal units in a coordinated manner. Furthermore, this paper considers the transmission constraints. The proposed method uses a tabu search for optimization method. Optimizing procedure is divided into two parts. Firstly, actual load is controlled by controllable load and battery. Finally, the schedule of thermal unit commitment problem is decided in the revised load. Simulation results show the validation of proposed method and validate the performance and effectiveness of the algorithm for controllable load and battery.

Optimal operation for DC smart-houses considering forecasted error

From the perspective of global warming suppression and depletion of energy resources, renewable energy such as wind generation (WG) and photovoltaic generation (PV) are getting attention in distribution systems. Additionally, all electrification apartment house or residence such as DC smart-house have increase in recent years. However, due to fluctuating power from renewable energy sources and loads, supply-demand balancing fluctuation of power system become problematic. Therefore, smart-grid has become very popular in worldwide. This paper presents a methodology for optimal operation of a smart grid to minimize interconnection point power flow fluctuation. To achieve the proposed optimal operation, we use distributed controllable loads such as battery and heat pump. By minimizing the interconnection point power flow fluctuation, it is possible to reduce the maximum electric power consumption and the electric cost. This system consists of photovoltaics generator, heat pump, battery, solar corrector, and load. In order to verify the effectiveness of the proposed system, MATLAB® is used in simulations.

Thermal units commitment with demand response to optimize battery storage capacity

Recently, the deregulation and liberalization in power market increase the competition in retail and power sector. Therefore, power company needs to reduce operational cost and maximizes the profit by operating generator with higher efficiency. For the operation of the thermal generating units, it is important to satisfy transmission constraints. One of the system to satisfy the transmission constraints is the battery storage system. However, the battery storage system requires high capital cost, therefore, it is impossible to introduce the large capacity of the battery storage system to the power system. This paper introduces the demand response system to the thermal units commitment program. The demand response system can reduce the additional battery storage system capacity to satisfy the transmission constraints. The heat pump water heater (HPWH) and the electric vehicle (EV) are assumed as demand response system. Simulation results show the validation of the proposed method and validate the performance and effectiveness of the algorithm for controllable loads and batteries.

Coordinated Control of Energy Storage System and Diesel Generator in Isolated Power System

Nowadays, renewable energy systems such as wind turbine generators and photovoltaic systems are introduced to power systems. However, the renewable energy system is influenced by weather conditions, and the generated power of the renewable energy system is deviated. For the provision of deviated power, the battery energy storage system is introduced to suppress the deviation of the frequency and voltage in power system. However, it needs the large capacity of a battery system, which increases the capital cost. In this paper, we propose a coordinated control strategy between the diesel generator and the battery system to reduce the capital cost of battery, inverter capacity and storage capacity. The proposed control system incorporates the H-infinity control theory, which enables intuitive controller design in frequency domain. Effectiveness of the proposed control system is validated by simulation results.