Yeongsu Bak

MPC-SVM method for Vienna rectifier with PMSG used in Wind Turbine Systems

Using a Vienna rectifier as the machine-side rectifier of back-to-back converter is advantageous in terms of size and cost compared to three-level topologies and for this reason, the Vienna rectifier has been used in Wind Turbine Systems (WTS). This paper proposes a Model Predictive Control (MPC) method for the Vienna rectifier used in WTS with a Permanent Magnet Synchronous Generator (PMSG). The proposed MPC method considers the feasible eight-voltage vectors of the Vienna rectifier. In addition, the voltage vectors, which are the center voltage vectors of two feasible adjacent voltage vectors, are taken into consideration to improve the performance of the MPC method. The optimized voltage vector for the ripple minimization of PMSG currents is determined by cost function. Then, the neutral-point voltage unbalancing problem is considered for selecting the final switching set, which is generated by the space modulation method. The effectiveness and performance of the proposed MPC method is verified by simulations.

Discontinuous PWM for low switching losses in indirect matrix converter drives

This paper proposes a discontinuous pulse width modulation (DPWM) method for an indirect matrix converter (IMC) driving induction motor (IM) in order to reduce switching losses. The IMC has advantages that long lifetime and reduced volume depending on the lack of capacitors. However, the IMC has many electric switching devices because it is composed of two stages such as a rectifier stage and an inverter stage for AC/AC power conversion. Therefore, the IMC has higher switching losses according to a number of switching devices consequently. The other topologies are researched for reduction in the number of switching devices in the rectifier stage such as sparse matrix converter. On the contrary, in this paper, the DPWM method is used to reduce the switching losses of the inverter stage. The effectiveness of the proposed method for reduce the switching losses of the inverter stage is verified by simulation results.

An indirect matrix converter for dual output AC-drive system with reduced number of power transistors

This paper proposes a three-phase input indirect matrix converter topology for a dual ac-drive system with modified switch control schemes, along with addition of a leg. This topology is developed based on a very sparse matrix converter with addition of a leg in the inverter stage, which can reduce the amount of power transistors compared to the conventional dual matrix converter system and; therefore, can achieve the realization of highly compact ac drives. A control strategy for the system, which combines vector control technology for loads and the space vector pulse width modulation (SVPWM) algorithm for a matrix converter with a four-leg inverter, is proposed. The proposed control and modulation schemes guarantee sinusoidal input/output waveforms and bidirectional power flow. Finally, the proposed system and independent control algorithm are verified by simulation using the very sparse matrix converter, which is implemented with 14 IGBT switches and 32 diodes connected to a three-phase and single-phase loads.

Torque-Ripple Reduction and Fast Torque Response Strategy for Predictive Torque Control of Induction Motors

This paper proposes a simple control method of induction motors (IMs) with improved dynamic response and steady-state performance by using a model-based predictive control algorithm. The predictive torque control (PTC) method analyzes the relationship between the electrical torque and stator voltage of IMs by using the stator voltage vector magnitude to obtain the reference voltage vector angle and accurately control the electrical torque. However, the conventional PTC method has a fixed reference voltage vector magnitude and thus has a large torque ripple in the steady state and slow dynamics in the transient state. The proposed PTC method is based on mathematical equations, which allow minimization of torque error and calculation of a relevant reference voltage to establish a better dynamic response in the transient state and accurate control performance in the steady state. Excellent steady-state performance and a quick dynamic response of the proposed method are proved by the simulation and experimental results.

A low voltage ride through control strategy for energy storage systems

This paper proposes a low voltage ride through (LVRT) control strategy for energy storage systems (ESSs). The LVRT control strategies for wind turbine systems and photovoltaic systems have been researched until now. Regardless of the energy source, the main aim of the LVRT control strategies for a grid side converter is to inject the reactive power according to the gird code regulations. The main aim of the proposed LVRT control strategy for ESSs is the same as them; however, it additionally considers the case of charging state which cannot be taken into consideration in wind turbine systems and photovoltaic systems having unidirectional power flow. The proposed LVRT control strategy for ESSs determines not only the reactive reference current for injecting the reactive power but also the active reference current to contribute to a point of common coupling (PCC) voltage increase by considering the two operating condition of charging and discharging state. The validity of the analysis is verified by simulation results.

Constant speed control for a reverse matrix converter under variable input conditions

This paper proposed control strategy of induction motor (IM) fed by indirect matrix converter (IMC) in reverse power mode. The IMC is an AC/AC power conversion system without dc-link energy storage elements as bulky capacitor or inductor. For this reason, the IMC has many advantages that compact, low weight and durability. Furthermore, it features full four quadrant operation and sinusoidal input currents. However the IMC usually operated with maximum voltage transfer ratio of 0.866, which is an inherent restriction. In order to increase the voltage transfer ratio, the novel structure of the IMC that reverses the direction of power flow is adopted. This structure operates boost mode without auxiliary elements or circuits. The effectiveness of the proposed method is confirmed by simulation results.

Basic Control of AC Motor Drives

Abstract The basic principle and control of AC motor drives are introduced in this chapter. AC motors are divided into induction motors and permanent magnet synchronous motors. The principle of each type of AC motor is introduced. In addition, the vector control of AC motor drives is introduced as a basic control. Simulation is performed in an AC motor drive system to verify the basic control of the AC motor drive.

Modeling and Control of AC/AC Converter

Abstract In this chapter, a matrix converter for direct AC-AC power conversion will be described. The matrix converter transfers power bidirectionally and controls the power factor of an input stage but does not require any DC-link capacitor. Hence, the matrix converter has received attention as a circuit system that has the capability of providing AC output of variable voltage and frequency without DC conversion from a commercial three-phase AC source. It is used in industrial applications that require high reliability, miniaturization, and sinusoidal input and output currents as well as bidirectional power flow capabilities.

Reverse matrix converter control method for PMSM drives using DPC

ABSTRACT This paper proposes a control method for a reverse matrix converter (RMC) that drives a three-phase permanent magnet synchronous motor (PMSM). In this proposed method, direct power control (DPC) is used to control the voltage source rectifier of the RMC. The RMC is an indirect matrix converter operating in the boost mode, in which the power-flow directions of the input and output are switched. It has a minimum voltage transfer ratio of 1/0.866 in a linear-modulation region. In this paper, a control method that uses DPC as an additional control method is proposed in order to control the RMC driving a PMSM in the output stage. Simulations and experimental results verify the effectiveness of the proposed control method.

Constant Speed Control of a Permanent-Magnet Synchronous Motor Using a Reverse Matrix Converter Under Variable Generator Input Conditions

This paper proposes a control strategy for a permanent-magnet synchronous motor (PMSM) fed by an indirect matrix converter (IMC) operating in boost mode. In order to increase the voltage transfer ratio of the IMC, a structure of the IMC having the inverse direction of power flow is adopted, which is called a reverse matrix converter (RMC). This structure operates in boost mode without additional elements or circuits. In this paper, although a generator having variable conditions is used for the input stage of the RMC system, the PMSM of the output stage can be controlled to a constant speed through the proposed control strategy. The validity of the proposed control strategy is demonstrated by simulation and experimental results.