A New Method for Smoothing Output Power Fluctuations of PV System Connected to Small Power Utility

Tomonobu Senjyu,Manoj Datta,Atsushi Yona,Hideomi Sekine,Toshihisa Funabashi 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

A Photovoltaic (PV) system’s power output is not constant and fluctuates depending on weather conditions. Fluctuating power causes frequency deviations in the power utilities when PV power penetration is large. Using a battery is one feasible measure to stabilize a PV system’s power output, but it requires additional costs and results in additional waste of used batteries. In this paper, to overcome these problems, we propose a new method for leveling the fluctuations in a PV system’s power output. By means of the proposed method, output power control of PV system considering the conditions of power utilities becomes possible and the conflicting objective of output power leveling and maximizing energy capture are achieved. Here, fuzzy reasoning is used to generate the output leveling power command. This fuzzy reasoning has three inputs of average insolation, variance of insolation, and absolute average of frequency deviation. Power converter is used to achieve output power same as command power employing PI control law. The proposed method is compared with the method where extracted maximum power is given to the utility without leveling. The simulation results show that proposed method is effective for leveling output fluctuations and feasible to reduce the frequency deviation of the small power utility.

Smoothing Output Power Variations of Isolated Utility Connected Multiple PV Systems by Coordinated Control

Manoj Datta,Tomonobu Senjyu,Atsushi Yona,Hideomi Sekine,Toshihisa Funabashi 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.2

A Photovoltaic (PV) system’s power output varies with the change of climate. Frequency deviations, tie line voltage swings are caused by the varying PV power when large PV power from several PV systems is fed in the utility. In this paper, to overcome these problems, a simple coordinated control method for smoothing the variations of combined PV power from multiple PV systems is proposed. Here, output power command is formed in two steps: central and local. Fuzzy control is used to produce the central smoothing output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is kept between the central power command and the local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV systems. Simulation results show that the proposed method is effective for smoothing the output power variations and feasible to reduce the frequency deviations of the power utility.

An Adaptive Dead-time Compensation Strategy for a Permanent Magnet Synchronous Motor Drive Using Neural Network

Naomitsu Urasaki,Tomonobu Senjyu,Toshihisa Funabashi,Hideomi Sekine 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4

This paper presents a neural network based adaptive dead-time compensation strategy for an inverter fed permanent magnet synchronous motor drive. The neural network is used for identifying the dead-time compensation time (DTCT) that includes an equivalent dead-time, turn-on/off time and on-state voltage components of the voltage source inverter. In order to train the neural network, desired DTCTs for eight operating points are prepared as training data. The trained neural network can identify a desired DTCT for any operating point because it has the capability of the interpolation. The accuracy of the identified DTCT is experimentally confirmed by comparing the calculated active power with a measured one.

Smoothing Output Power Variations of Isolated Utility Connected Multiple PV Systems by Coordinated Control

Datta, Manoj,Senjyu, Tomonobu,Yona, Atsushi,Sekine, Hideomi,Funabashi, Toshihisa The Korean Institute of Power Electronics 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.2

A Photovoltaic (PV) system's power output varies with the change of climate. Frequency deviations, tie line voltage swings are caused by the varying PV power when large PV power from several PV systems is fed in the utility. In this paper, to overcome these problems, a simple coordinated control method for smoothing the variations of combined PV power from multiple PV systems is proposed. Here, output power command is formed in two steps: central and local. Fuzzy control is used to produce the central smoothing output power command considering insolation, variance of insolation and absolute average of frequency deviation. In local step, a simple coordination is kept between the central power command and the local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV systems. Simulation results show that the proposed method is effective for smoothing the output power variations and feasible to reduce the frequency deviations of the power utility.

A Coordinated Control Method for Leveling Output Power Fluctuations of Multiple PV Systems

Tomonobu Senjyu,Manoj Datta,Atsushi Yona,Hideomi Sekine,Toshihisa Funabashi 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

A Photovoltaic (PV) system’s power output fluctuates with the change of weather conditions. Frequency deviations, tie line voltage fluctuations etc. are caused by fluctuating PV power when large PV 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 PV power from multiple PV systems is proposed. Here, output power command is generated in two steps: central and local. Fuzzy control 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 PI control law for each of the PV generation systems. The proposed method is compared with the method where conventional Maximum Power Point Tracking (MPPT) control is used for each of the PV system’s power output. Simulation results show that the proposed method is effective for leveling output power fluctuations and feasible to reduce the frequency deviations of the power utility.

An Adaptive Dead-time Compensation Strategy for a Permanent Magnet Synchronous Motor Drive Using Neural Network

Urasaki Naomitsu,Senjyu Tomonobu,Funabashi Toshihisa,Sekine Hideomi The Korean Institute of Power Electronics 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.4

This paper presents a neural network based adaptive dead-time compensation strategy for an inverter fed permanent magnet synchronous motor drive. The neural network is used for identifying the dead-time compensation time (DTCT) that includes an equivalent dead-time, turn-on/off time and on-state voltage components of the voltage source inverter. In order to train the neural network, desired DTCTs for eight operating points are prepared as training data. The trained neural network can identify a desired DTCT for any operating point because it has the capability of the interpolation. The accuracy of the identified DTCT is experimentally confirmed by comparing the calculated active power with a measured one.

Speed Sensorless Control of Ultrasonic Motors Using Neural Network

Tomohiro Yoshida,Tomonobu Senjyu,Mitsuru Nakamura,Naomitsu Urasaki,Toshihisa Funabash,Hideomi Sekine 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.1

In this paper, a speed sensorless control for an ultrasonic motor (USM) using a neural network (NN) is presented. In the proposed method, rotor speed is estimated by a three-layer NN which adapts nonlinearities associated with load torque and motor temperature into control. The intrinsic properties of a USM, such as high torque for low speeds, high static torque, compact size, etc., offer great advantages for industrial applications. However, the speed property of a USM has strong nonlinear properties associated with motor temperature and load torque, which make accurate speed control difficult. These properties are considered in designing a control method through the application of mathematical models. In these strategies, a detailed speed model of the USM is required which makes actual applications impractical. In the proposed method, a three-layer NN estimates the speed of the USM from the drive frequency, the root mean square value of input voltage and the surface temperature of the USM, where no mechanical speed sensor is needed. The NN speed based estimator enables inclusion of variations in driving conditions due to input signals of the NN involved during the driving state of the USM. The disuse of sensors offers many advantages on both the cost and maintenance front. Moreover, the model free sensorless control method offers practical controller construction within a small number of parameters. To validate the proposed speed sensorless control method for a USM, experiments have been executed under several conditions.

Wide-Speed-Range Optimal PAM Control for Permanent Magnet Synchronous Motors

Tomonobu Senjyu,Yohei Noguchi,Naomitsu Urasaki,Atsushi Yona,Hideomi Sekine,Toshihisa Funabashi 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-

Generally, PWM voltage source inverter (VSI) has been used for the variable speed permanent magnet synchronous motor (PMSM) drives. However, the PWM-VSI fed PMSMs has two disadvantages. Firstly, PMSMs cannot operate at the speed at which the motor terminal voltage exceeds voltage constraint imposed by the DC-link voltage. Secondly, the distortion of the voltage commands increase at the low speed, because the DC-link voltage is significantly higher than the motor line voltage. Because of this, the armature currents are distorted and then the torque ripple increases. Consequently, higher DC-link voltage influences the speed control performance at the low speed range. This paper proposes an optimal PAM control which can adjust the inverter DC-link voltage by using the buck-boost DC-DC converter. Further, considering the electrical vehicle application, the converter enables bi-directional power flow. At low speed range, the proposed system can reduce the total harmonic distortion (THD) of the voltage commands, and then the armature currents waveforms would be improved. Also, the allowable speed range would be extended. In order to verify the proposed method, simulation results are presented.

Speed Sensorless Control of Ultrasonic Motors Using Neural Network

Yoshida Tomohiro,Senjyu Tomonobu,Nakamura Mitsuru,Urasaki Naomitsu,Funabashi Toshihisa,Sekine Hideomi The Korean Institute of Power Electronics 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.1

In this paper, a speed sensorless control for an ultrasonic motor (USM) using a neural network (NN) is presented. In the proposed method, rotor speed is estimated by a three-layer NN which adapts nonlinearities associated with load torque and motor temperature into control. The intrinsic properties of a USM, such as high torque for low speeds, high static torque, compact size, etc., offer great advantages for industrial applications. However, the speed property of a USM has strong nonlinear properties associated with motor temperature and load torque, which make accurate speed control difficult. These properties are considered in designing a control method through the application of mathematical models. In these strategies, a detailed speed model of the USM is required which makes actual applications impractical. In the proposed method, a three-layer NN estimates the speed of the USM from the drive frequency, the root mean square value of input voltage and the surface temperature of the USM, where no mechanical speed sensor is needed. The NN speed based estimator enables inclusion of variations in driving conditions due to input signals of the NN involved during the driving state of the USM. The disuse of sensors offers many advantages on both the cost and maintenance front. Moreover, the model free sensorless control method offers practical controller construction within a small number of parameters. To validate the proposed speed sensorless control method for a USM, experiments have been executed under several conditions.

Position Sensorless Control for Ultrasonic Motors Based on Input Voltage Information

Tomonobu Senjyu,Tomohiro Yoshida,Naomitsu Urasaki,Katsumi Uezato,Toshihisa Funabashi,Hideomi Sekine,S. K. Panda 전력전자학회 2004 ICPE(ISPE)논문집 Vol.- No.-

This paper presents a method of position sensorless control of ultrasonic motor (USM). The rotor position of USM is estimated based on the input voltage information. The characteristic of input voltage versus rotor position is expressed by a quadratic function. Since the parameters of quadratic function are adjusted by using recursively least square method, estimated rotor position agrees well with actual rotor position against load torque and motor temperature changes. Position sensorless control is achieved by using estimated rotor position instead of measured rotor position. The validity of the proposed method is confirmed by experimental results.