Switch-Mode Power Supply Design - P.R.K. Chetty

LINK
http://www.mediafire.com/file/ykc91hx0k4o565x/Switch-Mode-Power-Supply-Design-Chetty.pdf

SIMPLE PWM inverter circuit SG3524(PWM)

A Study on the Wireless Parallel Operation of a Three-phase Modular UPS Inverter Seon – Tae Kim Department of Electrical Communication System Engineering Graduate School of Soonchunhyang University Asan, Korea

A Study on the Wireless Parallel Operation of a Three-phase Modular UPS Inverter Seon – Tae Kim Department of Electrical Communication System Engineering Graduate School of Soonchunhyang University Asan, Korea (Supervised by Professor Jun–Keun Ji) 

 This paper proposes a wireless parallel operation method of three-phase modular UPS inverter using resistive droop control. Control schemes for the parallel operation of UPS inverters can be classified into two types depending on the presence or absence of the communication line. In this paper, the wireless droop control method is used to overcome the disadvantages of the parallel operation method using communication line. Line impedance of low voltage grid such as parallel UPS inverter system is predominantly resistive. Hence, this paper uses resistive droop control method. And it uses the method holding the system frequency on 60  by applying Q-f(reactive power-phase angle) droop control that takes phase angle instead of frequency of output voltage. Furthermore, it applies a virtual resistor to droop control so that the output impedance of UPS inverter gets closer to resistive. It makes resistive droop control effective. This paper considers modular UPS using three-phase four-wire three-level NPC inverter. Because of symmetry of the circuit configuration, it can be modeled as a separate single-phase three-level inverter. From this, PR voltage controller with excellent control characteristics in single-phase inverter and PI current controller is used. The simulation using PSIM was performed in order to verify the validity of proposed algorithm. After consisting two-parallel system with three-phase modular UPS inverter, the experiment according to resistive load was conducted. It demonstrated the performance of current sharing and power sharing.

A Study on the Wireless Parallel Operation of a Single-phase UPS Inverter using Single-loop Robust Voltage Controller Dae-kwan Ku Department of Electrical Communication System Engineering Graduate School of Soonchunhyang University South Korea

A Study on the Wireless Parallel Operation of a Single-phase UPS Inverter using Single-loop Robust Voltage Controller Dae-kwan Ku Department of Electrical Communication System Engineering 
Graduate School of Soonchunhyang University Asan, South Korea
 (Supervised by Professor Jun - Keun Ji, Guee - Soo Cha) 

ABSTRACT
This paper proposes a wireless parallel operation method of single-phase UPS inverter using single-loop robust voltage controller and resistive droop control. Conventional parallel operation methods of UPS inverter using communication line are that such as centralized control, master-slave(MS), average current sharing(ACS), and circular chain control(3C). Although these methods achieve both good THD of output voltage and equal current sharing, but they need communication line. Therefore could reduce the system reliabilty and expandability. The wireless parallel operation such as droop control is suitable method to overcome for demerits of parallel operation methods using communication line. The droop control method don't need communication line because it uses only local power measurements. Thus droop control method is proper method for parallel operation of modular UPS. Conventional P-ω, Q-E inductive droop control method is derived from the assumption that UPS inverter output impedance is pure inductive. Therefore it's not proper method for low voltage grid such as parallel UPS inverter system. Hence, this paper uses P-E, Q-ω resistive droop control method. This method is derived from the assumption that UPS inverter output impedance is pure resistive. In addition, a single-loop robust voltage controller is used for the UPS inverter. The single-loop voltage controller can reduce material cost owing to the decrease of current sensor in the UPS system. Then simulations and experiments for the two-parallel system of single-phase UPS inverters with resistive and nonlinear loads demonstrate the feasibility of proposed parallel operation method providing improved performance - good output voltage control and equal power sharing. Key words : UPS inverter, parallel operation, robust voltage control, droop control.

A Study on the Heat Flow Inside UPS according to the Outside Temperature Dong – Min Kim Department of Mechanical Engineering, The Graduate School Konyang University

A Study on the Heat Flow Inside UPS according to the Outside Temperature Dong – Min Kim
 Department of Mechanical Engineering, The Graduate School Konyang University 
Nonsan Chungnam Korea 
(Supervised by Professor Young-Sik Yoon)
ABSTRACT
 UPS is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails. When installing UPS in outdoors (a road near or mountain, etc..), it is also possible many problems according to the outdoor environment. And it is possible generate condensation by a temperature difference The purpose of this study was to predict the inner temperature of UPS and to prevent dew condensation in UPS by simulating the heat flow using ANSYS. So in this study, The inner heat flow simulations for UPS were conducted by the Computation Fluid Dynamics Analysis, ANSYS, during the active state of UPS. Compared with Air temperature, Relative humidity, Inner temperature of UPS to be found that condensation is occurring. It’s can be improved by ventilation or insulation effectively inside UPS according to this simulation result.
LINK
http://www.mediafire.com/file/qoeywubv5dful8a/A_Study_on_the_Heat_Flow_Inside_UPS_according_to_the_Outside_Temperature.pdf