Jaeho Choi

Direct Digital Control of Single-Phase AC/DC PWM Converter System

This paper presents a new technique for directly designing a linear digital controller for a single-phase pulse width modulation (PWM) converter systems, based on closed-loop identification. The design procedure consists of three steps. First, obtain a digital current controller for the inner loop system by using the error space approach, so that the power factor of the supply is close to one. The outer loop is composed of a voltage controller, a current control loop including a current controller, a PWM converter, and a capacitor. Then, all the components, except the voltage controller, are identified by a discrete-time equivalent linear model, using the closed-loop output error (CLOE) method. Based on this equivalent model, a proper digital voltage controller is then directly designed. It is shown through PSim simulations and experimental results that the proposed method is useful for the practical design of PWM converter controllers.

Decoupling IPD controller design for three-phase DC/AC inverter

This paper presents a decoupling IPD voltage control for three-phase DC/AC inverter. Though most of three-phase inverter system for UPS or stand alone renewable energy system have been analyzed by using DQ model and controlled with IPD controller. For the simplification of this DQ model coupled each other, DQ decoupling technique is proposed firstly and so the MIMO system can be changed to SISO system. Secondary, the CRA based design procedure for IPD controller is presented and it satisfies the specified time response and overshoot of the controller, of which parameters are determined practically by trial and error method. Finally, the performance of this proposed algorithm is verified through PSiM simulation.

Electrical Modeling of Lithium-Polymer Battery

Electrical modeling of lithium-polymer battery is very important for electric energy supply system. In this paper, electric equivalent circuit of lithium-polymer battery is proposed to simulate its dynamic characteristics. Maccor 8500 charge/discharge system is used to obtain the experimental data of lithium-polymer battery. Model parameters are calculated by using Matlab. This paper defines a R-C model for charging/discharging of battery and polynomial functions are used for OCV (Open Circuit Voltage) modeling. The proposed model is simulated with PSiM and then compared the simulation results with the experimental results to verify the validity of the proposed model.

Voltage disturbance generator with phase jump for the test of microgrid

A voltage disturbance generator for the test of a microgrid is described. The generator provides the function of voltage sag, unbalance, outage, and phase jump of the output voltage. The proposed generator has good features of high reliability, low cost, simple structure, high efficiency, and easy implementation. The main components of the generator are SCR thyristors and transformers, which provides reliable system. The circuit analysis and operating principle of the proposed scheme are described in each operating mode. The characteristics of the voltage and current in each mode are analyzed, and the usefulness of the scheme is verified through simulations.

Resonant Pulse Power Converter with a Self-Switching Technique

In this paper, a resonant pulse power converter (RPPC) is proposed. The proposed RPPC transfers the pulse-shape power from a DC source to a load periodically. The RPPC consists of a resonant circuit and a resonant pulse converter driven by a self-switching circuit. Depending on the magnitude difference between the input and output voltages, the operations of the RPPC are divided into 4 modes; boost mode, hybrid mode, direct mode and cut-off mode, respectively. The main switch of the RPPC turns on in the ZCS condition and off in the ZVS condition spontaneously. The operational principles of a RPPC using the self-switching technique are analyzed and verified in experiments. An example of a RPPC application is demonstrated in the area of thermoelectric energy harvesting.

Improvement of a PV-FC hybrid source operation in a microgrid

Microgrid system has multiple distributed generators (DGs) which participate in sharing the local load. The considered microgrid system includes a hybrid source connected to a feeder in parallel with other distributed generators. The hybrid source comprises of a Photovoltaic (PV) array and a Proton exchange membrane fuel cell (PEMFC). The PV array normally uses a maximum power point tracking (MPPT) technique to continuously deliver the highest power to the load when variations in irradiation and temperature occur, which make it becomes an uncontrollable source. In coordination with PEMFC, the hybrid system output power becomes controllable. On the other hand, the microgrid has two control modes, Unit-power control (UPC) mode and Feeder-flow control (FFC) mode. Therefore, the operation of PV and FC must be coordinated when the control mode is either UPC or FFC. The paper presents a method to operate the hybrid source so that the PV can always work with MPPT and the PEMFC can work in a high efficiency performance band regardless the UPC mode or the FFC mode. Such a proposed method can improve the performance of the system operation, enhance the system stability, and decreases the number of mode change.

PSIM Simulator for Analysis of Series HEV Operation

This paper describes the PSIM simulator for the analysis of the series type HEV operation. The traction force of the series type HEV of which engine is electrically coupled with a traction motor is supplied from the traction motor only. The rating of each power train components, such as gear, motor, ESS, ICE/generator, is designed with the Energy-Based Modeling method and the Electrical Peaking Hybrid(ELPH) method. Under driving cycle, the designed series HEV is evaluated with the developed PSIM simulator. A comparison between the conventional braking and the regenerative braking is performed with the average motor input power. And the fuel economy analysis is carried out on the basis of the simulation results.

PSiM Based Dynamic Analysis of Input Split Type Hybrid Electric Vehicle

In this paper, the input split type series-parallel hybrid electric vehicle (SPHEV) is established and the interpretation of the dynamic characteristics in four kinds of HEV modes, such as electric vehicle mode, engine mode, hybrid mode, and regeneration mode, is described. For this research, the forward-facing approach simulation method is chosen, which is useful for vehicle dynamic analysis. The rating of each powertrain component is designed based on energy-based concept and electrical peaking hybrid (ELPH) method. Finally, the designed powertrain is evaluated with the developed PSiM simulator and simulation results are shown.

Indirect digital control of three-phase DC/AC inverter

This paper presents an analytical design method of indirect full digital controller with a simple structure for three-phase inverter system. Most of conventional researches on the analytical design of controller have been studied about the structure of continuous-time controller, and so the final implementation of full digital controller for industrial application was complicate and anyway based on the trial and error methods for gain tuning. So firstly, two axes model of synchronous reference frame is derived to adopt a linear controller in s-domain. During this process, two decoupling terms are generated and the system is to be MIMO. Before eliminating the coupling term to make the system be SISO, the effects of two coupling terms are analyzed by RGA and simulation. And then, the controller of two-parameter structure which has no additional zero in the transfer function is designed by the CRA method and the pole-placement method in s-domain to meet the time response specification depending on the system response. To make a digital controller, the designed controller of two-parameter structure is manipulated and minimally realized. The indirect full digital controller is simulated by PSiM DLL and experimented by TMS320VC33 without any conversion of program. The simulation and experiment results show the good performance of tracking and regulation.

Operation Analysis of Resonant DC/DC Converter able to Harvest Thermoelectric Energy

The operational characteristics of a resonant DC/DC converter, which can harvest thermoelectric energy, is analyzed, depending on the relative magnitudes of the input voltage and the load voltage. The resonant converter consists of LC resonant circuit connected to DC input source and a resonant pulse converter in which the input energy is transferred to the load as the resonant capacitor voltage is peak. The resonant capacitor doubles the input voltage by the resonance phenomenon. By the relative magnitude between the input voltage and the output voltage, the resonant DC/DC converter operates in three different modes. For boost mode, the peak voltage of the resonant capacitor is smaller than the load voltage. For hybrid mode, the peak voltage of the resonant capacitor is bigger than the load voltage and every switching period has both the boost mode and the direct mode. For the direct mode, the input voltage is bigger than the load voltage and the converter transfers directly the input energy to the load without the switching operation. Operation principles and the feasibility of the converter for the thermoelectric energy harvesting are verified with PSPICE simulation and experiment.