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Surge tests were performed to derive a generator model considering its frequency characteristics. Impulse voltages were applied to one terminal of the generators after placing a variable capacitor at the same terminal. The inductances and the core-loss resistances of a generator model can be determined from the measured oscillating voltages. This paper presents a generalization of the method aimed at deriving these generator parameters. The accuracy of the proposed method is confirmed to be satisfactory after comparing measured and simulated transfer voltages. [ABSTRACT FROM AUTHOR]

Focuses on hydraulic generator modeling in a transient simulation for a transformer transfer voltage due to a lightning surge on a transmission line from the perspective of an insulation design of a hydraulic generator station. Measurement of the transfer voltage of a generator; Three generator models; Inductance elements and capacitance elements.

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. [ABSTRACT FROM AUTHOR]

A photovoltaic (PV) system’s output power fluctuates according to the weather conditions. Fluctuating PV power causes frequency deviations in the power utilities when the penetration is large. Usually, an energy storage system (ESS) is used to smooth the PV output power fluctuations and then the smoothed power is supplied to the utility. In this paper, a simple fuzzy-based frequency-control method is proposed for the PV generator in a PV–diesel hybrid system without the smoothing of PV output power fluctuations. By means of the proposed method, output power control of a PV generator considering the conditions of power utilities and the maximizing of energy capture are achieved. Here, fuzzy control is used to generate the PV output power command. This fuzzy control has average insolation, change of insolation, and frequency deviation as inputs. The proposed method is compared with a maximum power point tracking control-based method and with an ESS-based conventional control method. The numerical simulation results show that the proposed method is effective in providing frequency control and also delivers power near the maximum PV power level. [ABSTRACT FROM AUTHOR]

With the increasing trend of connecting high penetrations of wind energy conversion systems (WECSs) to the transmission networks comes the challenge of updating the grid code for the connection of megawatt-class wind turbines. Starting with each WECS entity in the wind farm, the specifications would require the ability to complement some of the power system control services - voltage and frequency control - currently carried out by conventional synchronous generation. This paper investigates output power stability of a WECS ma highly fluctuating wind environment. Based on a performability model, a control strategy is devised for maximizing energy conversion in low to medium winds, and maintaining rated output in above rated winds while keeping torsional torque fluctuations to a minimum. Control is exercised via collective blade pitch control as well as generator torque control. The fundamental philosophy behind the proposed control strategy for the wind turbine coupled to an asynchronous doubly fed induction generator is general and can be easily extended to other WECS configurations. [ABSTRACT FROM AUTHOR]

Strong growth figures prove that wind is now a mainstream option for new power generation. All the successful megawatt-class wind technology developments to date are results of evolutionary design efforts based on the premise that control can significantly improve energy capture and reduce dynamic loads. The main challenge is wind stochasticity that impacts both power quality and drivetrain fatigue life for a wind generating system. In the proposed paradigm, control is exercised through a self-tuning regulator (STR) that incorporates a recursive least-squares algorithm to predict the process parameters and update the states. In above rated regimes, the control strategy incorporating a pitch regulatory system aims to regulate turbine power and maintain stable, closed-loop behavior in the presence of turbulent wind inflow. The control scheme is formulated based on a detailed performability model; the wind speed is generated by a stochastic model, while the drivetrain is modeled as a multiinertia system linked by a non- ideal (Ks ≠ ∞) shaft described by nonlinear equations. Computer simulations reveal that achieving the two objectives of maximizing energy extraction and load reduction by the STR becomes more attractive relative to the classical PID controller design. [ABSTRACT FROM AUTHOR]

A Photovoltaic (PV) system's power output is not constant and fluctuates depending on weather conditions. Fluctuating power causes frequency deviations and reduction in reliability of the isolated power utility or microgrid when large output power from several PV systems is penetrated in the utility. In this paper, to overcome these problems, a simple coordinated control method for leveling the fluctuations of combined power output from multiple PV systems is proposed. The conflicting objective of output power leveling and acquisition power increase is achieved by means of the proposed method. Here, output power command is generated in two steps: central and local. Fuzzy reasoning is used to generate the central leveling output power command considering insolation, variance of insolation, and absolute average of frequency deviation. In local step, a simple coordination is maintained between central power command and local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing P1 control law for each of the PV generation systems. The proposed method is compared with the method where a modified maximum power point tracking control is used for smoothing the short-term change in each of the PV system's output. Simulation results show that the proposed method is effective for leveling output power fluctuations and feasible to reduce the frequency deviations of the isolated power utility to maintain reliability. [ABSTRACT FROM AUTHOR]

The rapid expansion of wind power generation has brought problems involving lightning strikes to the fore. Many such incidents have damaged not only the wind turbine that was actually struck but also other turbines that were not, a phenomenon that has yet to be fully explained. In this paper, the authors present a case study using a wind farm model with multiple wind turbines connected to a power system. The aim is to clarify the influence of the grounding system on surge propagation from a wind turbine that has been struck to others which have not, during a winter lightning strike. Sensitivity analyses show that the surge propagated to nearby wind turbines can sometimes become large, depending on the conditions of the grounding system, and result in the burnout of surge arresters in turbines that have not been struck, especially during winter lightning strikes. [ABSTRACT FROM AUTHOR]

This paper presents an adaptive dead-time compensation strategy to obtain fundamental phase voltage for inverter-fed vector-controlled permanent magnet synchronous motor drives. A phase dead-time compensation voltage (DTCV) to compensate the disturbance voltage due to undesirable characteristics of inverter, such as dead time, turn on/off time of switching devices, and on-voltages of switching devices and diode, is transformed into q-axis DTCV in the rotor reference frame. The relationship between q-axis DTCV and a dead-time compensation time (DTCT) is investigated. DTCT is identified online by using q-axis disturbance voltage, which is estimated by a disturbance observer. The amplitude of phase DTCV is adaptively determined according to the identified DTCT. The accuracy of identified DTCT is experimentally confirmed by calculating the mean absolute percentage error (MAPE) between calculated active power and measured one. MAPE for adaptive DTCT is within 5 % at any operating point and is less than that for the fixed DTCT. [ABSTRACT FROM AUTHOR]

Photovoltaic power generation and wind power generation have an advantage that energy is clean and infinite, but they have a disadvantage in that electrical output energy is unstable, and initial and maintenance costs are expensive. This paper presents an optimal configuration for renewable generating systems in residence using a genetic algorithm (GA). We define that the objective function is the total cost, where the total cost is the sum of initial cost, an operation cost, and a maintenance cost. We determine an optimal configuration of renewable generating systems, where total cost is more reasonable using GA. The simulation using this technique is shown. [ABSTRACT FROM AUTHOR]

Wind energy is not constant and windmill output is proportional to the cube of wind speed, which causes the generated power of wind turbine generators (WTGs) to fluctuate. In order to reduce fluctuation, different methods are available to control the pitch angle of blades of windmill. In a previous work, we proposed the pitch angle control using minimum variance control, and output power leveling was achieved. However, it is a controlled output power for only rated wind speed region. This paper presents a control strategy based on average wind speed and standard deviation of wind speed and pitch angle control using a generalized predictive control in all operating regions for a WTG. The simulation results by using actual detailed model for wind power system show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A hybrid power system uses many wind turbine generators in isolated small islands. The output power of wind turbine generators is mostly fluctuating and has an effect on system frequency. In order to solve this problem, we propose a new power system using renewable energy in small, isolated islands. The system can supply high-quality power using an aqua electrolyzer, fuel cell, renewable energy; and diesel generator. The generated hydrogen by an aqua electrolyzer is used as fuel for a fuel cell. The simulation results are given to demonstrate the availability of the proposed system in this paper. [ABSTRACT FROM AUTHOR]