Itaru Ando

Development of Single Phase UPS having AC Chopper and Active Filter Ability

This paper describes about development of single phase uninterruptible power supply (UPS) having AC chopper and active filter ability. The proposed UPS consists of a single phase full bridge type active filter and the source and load side AC choppers using bidirectional IGBT switches. It realizes long life and maintenance free of the main circuit because it has no use of the bulky electrolytic capacitor. The proposed UPS has active filter ability between the source and load side choppers, which realizes unity input power factor operation. The AC chopper regulates the output voltage sinusoidaly. The fundamental source power supply to the load in direct without switching of the every AC choppers under the normal power condition, which achieves high efficient system and high system reliability. The simulation results point out that the proposed UPS has the desired input and output characteristics such as 99% power factor and under 3% voltage regulation.

High efficient speed control of parallel-connected induction motors with unbalanced load condition using one inverter

Recently, the parallel speed control of two induction motors, which uses only one inverter, has been proposed by the vector control method. However, the conventional control method does not consider both the efficiency of the motor control and condition of different load torque to each induction motor (IM). This paper proposes a new high efficient parallel speed control method, which calculations the optimal voltage and frequency value based on non-linear programming method, even when two induction motors on condition different load torque. The non-linear programming method requires the information on load torque and speed reference. Each load torque is estimated by disturbance observer with current simulator and flux simulator. The IM driven system requests only speed sensor using rotary encoder. Hence, it has no current sensor and no voltage sensor. The experimental results point out that both induction motors keep the near same speed control performance with high efficiency in the steady state and the transient state, on condition of different load torque.

High efficient parallel-connected induction motor speed control with unbalanced load condition using one inverter

Recently, the parallel speed control of two induction motors, which uses only one inverter, has been proposed by the vector control method. However, the conventional control method does not consider both the efficiency of the motor control and the condition of different load torque to each induction motor (IM). This paper proposes a new high efficient parallel speed control method of two induction motors on condition of different load torque, which is based on non-linear programming method. The non-linear programming method requires the information on load torque and speed reference. Each load torque is estimated by disturbance observer and current simulator. The IM drive system requests only speed sensor such as rotary encoder. Hence, it has no current sensor and no voltage sensor. Moreover, this paper discusses the condition of low-resolution rotary encoder, such as 60pulse/rev. The numerical simulation results point out that both induction motors keep the nearly same speed control performance with high efficiency in steady state and the transient state on condition of different load torque.

Electric load controlled by computer simulator having power regeneration ability

This paper describes the newly developed electric load having a real time computer simulator and power regeneration ability. This electric load can be utilized by the various load-test equipment for the inverter and the converter. The developed single phase load has the following abilities: (1) it has the isolated power regeneration ability, and realizes small size and light weight because of high efficiency; (2) by compensating the input current waveform of the test equipment using active filter ability of the electric load, the unity power factor and the sinusoidal input current of the total system can be achieved; and (3) it can simulate various type of loads such as R-L, RC or rectifier circuits, and changing their circuit device values by real time simulator of the personal computer. As an experimental result, it is possible to obtain excellent simulation of loads including rapid load fluctuations and rush currents.

A simple sensorless method for sinusoidal PWM converters

This paper describes a simple sensorless method of PWM converters which can remove the line voltage sensors. It has the following characteristics. The voltage sensorless method is realized only by adding two operational amplifiers to the conventional PWM control circuit. Therefore, it has low cost and small size. The line current waveform can be improved by compensating voltage drops of the input filter reactor and dead-time of IGBTs. Quick response is also obtained on the high speed fluctuation of voltage and frequency or transient states. It can get characteristics other than the conventional complexity sensorless control methods. As a result, the input power factor and the total input current distortion of more than 99.5% and less than 2.3% are achieved, respectively on a 3 kW system. It not only obtains excellent performance but also realizes the small size, simple control construction and low cost converter.

Development of economical UPS system having active filter across DC-bus

This paper proposes an economical single-phase flywheel uninterruptible power supply (UPS) having active filter across the dc-bus. The proposed UPS consists of diode rectifier, inverters, LC filter and flywheel energy storage unit, and it has many features such as low production cost, long life of the system. The proposed UPS has the active filter ability across the dc-bus, which realizes unity power factor operation without both PWM rectifier and bulky electrolytic capacitor. A three-phase inverter regulates PM motor/generator speed with flywheel and compensates the harmonic input current to the sinusoidal input current. The dc-bus line has the absolute waveform of input voltage. The output voltage obtains the sinusoidal waveform by using synchronous switched single-phase inverter. The simulation results point out that the proposed economical flywheel UPS system has the desired sinusoidal input current and output voltage. Moreover, the proposed system realizes maintenance free system, small size, long life and very low production cost

Fine output voltage control for inverter system having nonlinear load and time-delay

This paper proposes a new output voltage control for inverter system which contains time-delay and nonlinear load. In the next generation X-ray CT system with the contactless power transfer method, the feedback signal often contains some long delay time by AD/DA conversion and error detection/correction time. When the PID controller of inverter system has the harmful influence on the time-delay, it often has an overshoot and an oscillated response. In order to overcome this problem, this paper proposes the compensation method based on Smith predictor for inverter system having the time-delay and the nonlinear load which is the diode bridge rectifier. The proposed compensation method consists of Smith predictor with the equivalent analog circuit. The experimental results confirm the validity of the proposed system.

Long life ups based on active filter and flywheel without electrolytic capacitor

This paper describes single-phase uninterruptible power supply (UPS) with active filter and flywheel. The UPS consists of a diode rectifier, a single-phase inverter, a flywheel energy storage unit with PM motor/generator and a three-phase inverter, not using a bulky electrolytic capacitor, battery and filter reactor. It contains many excellent characteristics: small size, lightweight and maintenance-free. The switching frequency of the single-phase inverter is more efficient with low frequency, which is synchronous with source voltage. However, it can supply stable power with the load. The unity input power factor control and the sinusoidal current waveform control of input side are realized by the active filter ability with quick energy charge/discharge control based on flywheel. The proposed system gives rise to sinusoidal output voltage waveform without LC filter. In this paper, the experiments are carried out under the structural conditions of using the pilot flywheel unit and the driving simulator of PM motor/generator connected to flywheel. The results indicate that the UPS has a desired active filter operation, and supplies the stable power with the load under any power condition.

Development of high efficiency control method for common leg converter using golden section method

This paper describes about development of high efficiency control method for the common leg converter using golden section method. The characteristics of this system are obtained as follows. (1) This system realizes high efficiency, small size, lightweight and low cost, because the adopted conversion circuit is consisted of the common leg type single phase converter/inverter. (2) The converter/inverter system achieves to high efficiency based on the current and voltage follow up control with golden section method in real time. Golden section method is calculated to optimal output voltage of the every legs for get maximum efficiency under the calculated switching and the conducting losses and the desired output voltage of converter/inverter. As a result, it is not only obtained the excellent performances such as 99% power factor, over 94% efficiency, sinusoidal source current and output line voltage but also applied to the three phase system and the active filter.

High power factor control using load resonant frequency auto tracking phase shift inverter

This paper proposes a new method for frequency control and for output power control using a load resonant frequency auto tracking phase shift inverter. The proposed method employs a phase shift inverter with a single output current sensor. The fundamental waveform signal of the output voltage of a phase shift inverter is generated by using the proposed method because the conventional method produces an output voltage that has a pulse waveform. The proposed control strategy to utilize load resonant frequency easily achieves unity power factor control with high efficiency. In the proposed method, the fundamental waveform signal of the inverter output voltage coincides with the detected inverter output current wave form. Moreover, as the inverter output power is regulated by controlling the phase angle of each inverter leg using the proposed method, soft-switching control can be realized. The experimental results presented in this paper confirm the validity of the proposed methods.