Yongsoo Cho

Virtual-Flux-Based Predictive Direct Power Control of Three-Phase PWM Rectifiers With Fast Dynamic Response

This paper proposes a power predictive control (PPC) method for three-phase pulse width modulated rectifiers without a proportional-integral controller. The proposed PPC method calculates the optimized voltage vector by analyzing the relationship between the virtual flux, active power, converter voltage, and filter parameters. Thus, an overshoot does not occur and the fast and accurate power control becomes possible. The predictive algorithm computes the power error that would be produced by applying each vector and selects the one that contributes the minimum error. The simulation and experimental results prove that the proposed method provides an excellent steady-state performance and quick dynamic response.

Torque ripple reduction and fast torque response strategy of direct torque control for permanent-magnet synchronous motor

This paper proposes a simple method direct torque control (DTC) based on space vector pulse width modulation (SVPWM) of surface-mounted permanent-magnet synchronous motors (SPMSM). The proposed DTC method calculates the optimized voltage vector using the motor parameters and the analysis of the relationship between the stator flux, torque, and stator voltage to calculate the optimized voltage vector. Thus the overshoot does not occur and the fast and accurate torque control becomes possible. The voltage vector calculation is divided into three steps. First, the magnitude of the voltage vector is calculated using the reference torque. Second, even though the motor parameters are not precise, the accurate torque control can be achieved through the compensation of the voltage vector. Last, the angle of the voltage vector is calculated through the magnitude of the voltage vector and the stator flux error. The calculated voltage vector controls the motor instantly and accurately by operating the inverter through the DTC-SVPWM method. The effectiveness of the proposed DTC method is verified through simulation. The simulation result proves that new strategies provide low torque ripple and quick dynamic performance.

Novel torque predictive control for a permanent-magnet synchronous motor with minimum torque ripple and fast dynamics

This paper proposes a simple and effective method to reduce the torque ripple for torque predictive control (TPC) of permanent-magnet synchronous motors (PMSM). The proposed minimum torque ripple TPC is a two-step design. The first step is to determine hysteresis band by using stator flux error in order to apply effective voltage as much as needed by stator flux control. Then, the second step is to recreate reference voltage vector, by estimating the magnitude and the angle of output voltage vector, which generates torque that is of equal magnitude to reference voltage vector previously produced by using bandwidth. The predictive algorithm computes the torque error that would be present by applying each vector and selects the one that contributes with the minimum error. Finally, the effectiveness of new strategies is verified through simulation. The simulation result proves that proposed TPC method is very simple and provides excellent steady-state response, quick dynamic performance.

Model predictive control using a three-level inverter for induction motors with torque ripple reduction

This paper proposes an improved model predictive control (MPC) algorithm for the direct torque and flux control of induction motors (IMs) using the three- level inverter. To reduce the calculation amount, which is the drawback of MPC, first the reference value and the state of the motor are analyzed to preselect the calculation region for the cost function; by only subdividing the voltage vectors in the selected region, the reference voltage vector is selected by the MPC algorithm. The selected voltage vector applies the output voltage to the actual system through the space vector modulation (SVM) method. Even though the proposed MPC algorithm has a slight increase of calculation compared to the conventional MPC, it can control the induction motor more precisely. The effectiveness of the proposed MPC method is verified through simulation. The simulation result proves that new strategies provides low torque ripple performance.

Predictive control algorithm for capacitor-less inverters with fast dynamic response

This paper presents a scheme to improve the input current ripple of capacitor-less inverter system using a predictive control algorithm. The capacitor-less inverter, which is using small capacitor in the dc-link, has several advantages such as competitive cost, compact size, enhanced reliability, and elimination of initial charging circuit. However, the dc-link voltage shows instability because the energy storage capability of the small capacitor is not sufficient. Therefore, DC-link shunt compensator (DSC) should be used in capacitor-less inverter to stabilize the dc-link voltage and nullify the negative impedance by injecting the compensation current. However, the general proportional integral (PI) current controller, which has wide bandwidth to track the compensation current having a sinusoidal waveform, is weak for the noise and disturbance. This paper proposes a model predictive control (MPC) algorithm to improve the performance of DSC. Given the optimal duty cycle calculated by estimating the next state current, the proposed algorithm has a fast dynamic response and accuracy. The proposed method is verified through PSIM simulations.

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.

LCL-filter design for grid-connected three-phase inverter using space vector PWM

This paper proposes a LCL-filter design for grid-connected three-phase inverter using space vector pulse width modulation (SVM). There is a variety of studies in progress. However, the existing methods have an error because they are not applicable in SVM. This paper presents the design method of LCL-filter that optimized for SVM switching operation. The LCL-filter design procedure performed step by step. Inverter-side inductor was obtained by mathematical analysis of the ripple components of the grid current according to the switching state. Filter capacitor was chosen by consideration of the reactive power absorption ratio. Grid-side inductor was designed by ripple attenuation factor of the output current. The effectiveness of the described design method of LCL-filter is verified by simulation.

Simple rotor position estimation for sensorless control of IPMSM using PLL based on EEMF

This paper proposes a simple sensorless control method based on an extended electromotive force (EEMF) models for an interior permanent magnet synchronous motor. The EEMF contains the position information of a motor. The EEMF can be estimated by using a lease-order observer. The proposed method estimates the position and speed of a motor using a phase locked-loop based on an EEMF. Because the calculation burden is reduced by using the proposed algorithm, the control period can be de decreased. The simulation results are provided to verify the effectiveness and performance of the proposed method.

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.

Virtual-flux-based power predictive control of three-phase PWM rectifiers using space-vector modulation

This paper proposes a power predictive control (PPC) method of three-phase pulse width modulated (PWM) rectifiers without a proportional-integral (PI) controller. The proposed PPC method calculates the optimized voltage vector by analyzing the relationship between virtual flux (VF), active power, converter voltage, and filter parameter. Thus the overshoot does not occur and the fast and accurate power control becomes possible. The predictive algorithm computes the power error that would be produced by applying each vector and selects the one that contributes with the minimum error. The simulation result proves that the proposed method provides low power ripple and quick dynamic performance.