There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

http://ieeexplore.ieee.org/iel5/5610941/5624686/05624745.pdf

Power electronics

In this paper, a Distribution STATic COMpensator (DSTATCOM) is proposed for compensation of reactive power and unbalance caused by various loads in distribution system. An evaluation of three different methods is made to derive reference currents for a DSTATCOM. These methods are an instantaneous reactive power theory, a synchronous reference frame theory, and a new Adaline-based algorithm. The Adaline-based algorithm is an adaptive method for extracting reference current signals. These schemes are simulated under MATLAB environment using SIMULINK and PSB toolboxes. Simulation and experimental results demonstrate the performance of these schemes for the control of DSTATCOM.

A Comparison of Control Algorithms for DSTATCOM

This paper presents a nonlinear control technique for a three-phase shunt active power filter (SAPF). The method provides compensation for reactive, unbalanced, and harmonic load current components. A proportional-integral (PI) control law is derived through linearization of the inherently nonlinear SAPF system model, so that the tasks of current control dynamics and dc capacitor voltage dynamics become decoupled. This decoupling allows us to control the SAPF output currents and the dc bus voltage independently of each other, thereby providing either one of these decoupled subsystems a dynamic response that significantly slower than that of the other. To overcome the drawbacks of the conventional method, a computational control delay compensation method, which delaylessly and accurately generates the SAPF reference currents, is proposed. The first step is to extract the SAPF reference currents from the sensed nonlinear load currents by applying the synchronous reference frame method, where a three-phase diode bridge rectifier with R-L load is taken as the nonlinear load, and then, the reference currents are modified, so that the delay will be compensated. The converter, which is controlled by the described control strategy, guarantees balanced overall supply currents, unity displacement power factor, and reduced harmonic load currents in the common coupling point. Various simulation and experimental results demonstrate the high performance of the nonlinear controller.

Correction to “Experimental Design of a Nonlinear Control Technique for Three-Phase Shunt Active Power Filter”

Conventional model predictive torque control (MPTC) suffers from weighing factor tuning work and relatively high torque ripple, due to the different units of torque and stator flux and the limited number of voltage vectors. This paper proposes an improved MPTC without the use of weighting factor. The torque and flux magnitude references are converted into an equivalent reference vector of stator flux, hence eliminating the weighting factor of stator flux in conventional MPTC. Furthermore, two voltage vectors are applied during one control period to achieve better steady-state performance. Different from prior method using an active vector and a zero vector, the selected voltage vectors may be two nonzero vectors in the proposed method, which provides more opportunities to reduce both torque and flux ripples. The durations of the selected voltage vectors are determined based on the principle of stator flux error minimization. Both simulation and experimental results are presented to validate the effectiveness of the proposed method.

Two-Vector-Based Model Predictive Torque Control Without Weighting Factors for Induction Motor Drives

This paper proposes a simple but effective method to reduce the torque ripple for direct torque control (DTC) of induction motor drives. The proposed DTC provides a global minimum torque ripple, which satisfies the root-mean-square (rms) criteria of torque ripple. Such a global minimum torque ripple DTC has not been derived before. The proposed global minimum torque ripple DTC is a two-step design. The first step drives the torque error to zero at the end of the control period. Then, the second step reduces the torque bias and rms ripple by modifying the asymmetry switching patterns of the applied voltage vectors of the first step into symmetry ones. Theoretical analysis is provided to show that the torque ripple of the proposed DTC is a global minimum rms ripple. Furthermore, to verify the effectiveness of this study, a DSP-based experimental induction motor DTC drive system is built. Simulation and experimental results verify that the torque ripple performance has been improved.

Global Minimum Torque Ripple Design for Direct Torque Control of Induction Motor Drives

This paper proposes a simple but effective method of electric brake with energy regeneration for a brushless DC motor of an electric vehicle (EV). During the braking period, the proposed method only changes the switching sequence of the inverter to control the inverse torque so that the braking energy will return to the battery. Compared with the presented methods, the proposed solution simultaneously achieves dual goals of the electric brake and the energy regeneration without using additional converter, ultracapacitor, or complex winding-changeover technique. Since the braking kinetic energy is converted into the electrical energy and then returns to the battery, the energy regeneration could increase the driving range of an EV. In addition to the braking period, the duration of release throttle is also included in the energy-regenerative mechanism such that the EV is similar to engine vehicles having the engine brake. Therefore, the electric brake can improve rider's comfort and enhance the EV's safety. Finally, the feasibility of the proposed method is demonstrated by experimental results. It shows that the driving range of the EV could be increased to about 16.2%.

A Cost-Effective Method of Electric Brake With Energy Regeneration for Electric Vehicles

In this paper, model reference adaptive control (MRAC) is proposed for a single-phase shunt active power filter (APF) to improve line power factor and to reduce line current harmonics. The proposed APF controller forces the supply current to be sinusoidal, with low current harmonics, and to be in phase with the line voltage. The advantages of using MRAC over conventional proportional-integral control are its flexibility, adaptability, and robustness; moreover, MRAC can self-tune the controller gains to assure system stability. Since the APF is a bilinear system, it is hard to design the controller. This paper will solve the stability problem when a linearization method is used to solve the nonlinearity of the system. Moreover, by using Lyapunov's stability theory and Barbalat's lemma, an adaptive law is designed to guarantee an asymptotic output tracking of the system. To verify the proposed APF system, a digital signal controller (dsPIC30F4012) is adopted to implement the algorithm of MRAC, and a 1-kVA laboratory prototype is built to test feasibility. Experimental results are provided to verify the performance of the proposed APF system.

Model Reference Adaptive Control Design for a Shunt Active-Power-Filter System

In this paper, model reference adaptive control (MRAC) is proposed for a single-phase shunt active power filter (APF) to improve line power factor and to reduce line current harmonics The proposed active power filter controller forces the supply current to be sinusoidal with low current harmonics and in phase with the line voltage The advantages of using MRAC over conventional proportional-integral (PI) control are more flexibility, adaptive and robustness; moreover, MRAC can self-tune the controller gains to assure the system stability Since the APF is a bilinear system, it is hard to design the controller This paper will solve the stability problem when linearization method is used to approach the nonlinearity of the system Besides, using Lyapunov's stability theory and Barbalat's Lemma, an adaptive law is designed to guarantee asymptotic output tracking for the system To verify the proposed APF system, a digital signal controller is adopted to implement the algorithm of MRAC and an 1-kVA laboratory prototype is built to test the feasibility

Model Reference Adaptive Control Design for a Shunt Active Power Filter System

This paper proposes a fuzzy state-of-charge (SOC) estimation for ReflexTM battery charging, which allows rapid and efficient charging for sealed lead-acid batteries used in electric vehicles. The proposed SOC estimation can avoid undercharging or overcharging. Overcharge in particular can shorten a battery's lifetime. The charging control and the SOC estimation are based on fuzzy theorem and they are implemented by a digital signal controller (dsPIC30F4011). The battery's SOC is estimated while the system was charging the battery and the estimated error is maintained within an acceptable range (±5%) . Moreover, this system used a method of equivalent internal resistance to calculate the internal resistance of the batteries. During the ReflexTM charging, the controller can self-tune the discharging time according to the internal resistances, which reduces the thermal rises and the lifetimes for the batteries. Finally, experimental results are provided to verify the performance of the system and the feasibility of the proposed SOC estimation in this paper.

Ming-Ji Yang

Papers

Global Minimum Torque Ripple Design for Direct Torque Control of Induction Motor Drives

A Cost-Effective Method of Electric Brake With Energy Regeneration for Electric Vehicles

Model Reference Adaptive Control Design for a Shunt Active-Power-Filter System

Model Reference Adaptive Control Design for a Shunt Active Power Filter System

Design fuzzy SOC estimation for sealed lead-acid batteries of electric vehicles in Reflex TM