Jung-Ryol Ahn

Algorithms for Controlling Both the DC Boost and AC Output Voltage of Z-Source Inverter

This paper aims to achieve the good performances of both the DC boost control and AC output voltage control of the Z-source inverter. The algorithm to control linearly the capacitor voltage is suggested in order to improve the transient response for DC boost control of the Z-source inverter. The peak AC output voltage is used to control exactly the AC output voltage to its desired level. The proposed algorithms are verified with simulation and experiment with 32-bit DSP

A Novel Strategy of Efficiency Control for a Linear Compressor System Driven by a PWM Inverter

Linear compressors with a free piston driven by a linear motor have attracted wide attention in cooling apparatuses such as refrigerators due to their high efficiency. The method of using triacs as a linear motor drive is not satisfactory for improving the efficiency of linear compressors. In this paper, the performance of linear compressors using a pulsewidth modulation inverter is investigated, with emphasis on the efficiency and power factor along with variations of both mechanical and electrical resonant frequencies. The strategy for improving the efficiency of the linear compressor is suggested by controlling the average value of the product of the piston stroke and motor current to 0. The performance of both the stroke and efficiency controls of the linear compressor is verified through experiments under various gas pressure conditions.

Algorithms for controlling both the DC boost and AC output voltage of the Z-source inverter

This paper aims to achieve good performance for both the dc boost and the ac output voltage control of the Z-source inverter (ZSI). The algorithm to control linearly the capacitor voltage is suggested in order to improve the transient response for dc boost control of the ZSI. The peak value of the ac output voltage is used to control exactly the ac output voltage to its desired level. A modified space vector pulsewidth modulation scheme is applied to control the shoot-through time for boosting dc voltage. The proposed algorithms are verified with simulation and experiment with a 32-bit digital signal processor.

AC Output Voltage Control with Minimization of Voltage Stress Across Devices in the Z-Source Inverter Using Modified SVPWM

The paper proposes the algorithms of ac output voltage control in the Z-source inverter while minimizing the voltage stress across the devices. A novel switching pattern in the SVPWM is used in order to boost easily the capacitor voltage by controlling a shoot through time. The possible operating region for obtaining a desired ac output voltage to dc input voltage is analyzed. The voltage stress across the switching devices can be so mush reduced at a given ac output voltage. The proposed methods are verified with the simulation studies and experiments with 32-bit DSP.

Method of Estimating the Stroke of LPMSM Driven by PWM Inverter in a Linear Compressor

Linear compressors with a free piston driven by a linear motor have widely attention in cooling apparatuses such as refrigerators due to their high efficiency. The stroke of piston in a linear compressor driven by LPMSM can be obtained from integrating the EMF of LPMSM, but it may be saturated due to dc components in measured motor voltage and current. The method for estimating the piston stroke by using both the high-pass filter and dc offset compensation is suggested. The attenuation and dc offset of stoke are investigated according to a variation of cut-off frequency of high-pass filter. Through the experiments with 16-bit DSP, it can be seen that the piston stroke is nearly sinusoidal waveform without any dc offset at transient state as well as at steady-state condition.

A modified space vector PWM for common mode voltage itigation in diode rectifier / Z-source inverter system

In this paper, the common-mode voltage of the diode rectifier/Z-source inverter system is analyzed in detail under both the shoot-through state and non-shoot-through state. Then, a modified space-vector modulation strategy is proposed to effectively mitigate the amount of negative common-mode voltage. The negative common-mode voltage can be attenuated, by eliminating the zero voltage vector V0 in modified space-vector modulation. The proposed method is easily implemented in software. Finally, some simulation studies by PSIM and experiments with 32-bit DSP are carried out to demonstrate the benefits of the proposed algorithm.

Development of servo motor drive systems for embroidery machines

The precise and fast position control of motor for the embroidery machine drive is very important to improve an operating efficiency. In this paper, the method to control rapidly and precisely the position of PMSM by adjusting the proportional gain in the position controller to a position error is suggested. Through simulation studies, the position of PMSM reaches rapidly reference position without any overshoots.

Algorithm for Reducing the Effect of Network Delay of Sensor Data in Network-Based AC Motor Drives

Network-based controls for ac motor drive systems are becoming increasingly important. In this paper, an ac motor control system is implemented by a motor control module and three sensor modules such as a voltage sensor module, a current sensor module, and an encoder module. There will inevitably be network time delays from the sensor modules to the motor control system, which often degrades and even destabilizes the motor drive system. As a result, it becomes very difficult to estimate the network delayed ac sensor data. An algorithm to reduce the effects of network time delays on sensor data is proposed, using both a synchronization signal and a simple method for estimating the sensor data. The algorithm is applied to a vector controlled induction motor drive system, and the performance of the proposed algorithm is verified with experiments.