Multimodule parallel series-loaded resonant converters

The design and implementation of a multimodule parallel series-loaded resonant (SLR) converter system is presented. The SLR converter to be paralleled is operated in the n=2 discontinuous mode (DCM). Its dc analysis and dynamic modeling are made. In parallel operation, an average control technique is proposed to compensate the mismatch in current control characteristics of each parallel converter. Good dynamic and static current sharing characteristics are obtained. In addition, to obtain good output voltage regulating control performance, a design procedure is presented to find the parameters of feedback voltage controller according to the prescribed specifications     

Random hysteresis PWM inverter with robust spectrum shaping

A hysteresis current-controlled pulsewidth modulation (PWM) scheme is simple and robust in switching control, but it is subject to not constant switching frequency. However, since its harmonic spectrum is not randomly distributed like those yielded by the random PWM (RPWM) scheme, the annoying harmonic effects still exist. A random switching control strategy is proposed here to let the harmonic spectrum of the hysteresis current-controlled PWM inverter be randomly distributed. First, the effect of varying band on the harmonic distribution characteristic of a hysteresis current-controlled PWM scheme is analyzed. Then a random hysteresis PWM scheme and its quantitative design procedure are proposed. Finally, a robust spectrum shaping technique is devised such that the desired harmonic distribution pattern can be achieved. In the resulting frequency spectrum, the magnitudes of lower frequency harmonics are shaped and reduced. Hence the inverter output with a better harmonic attribute is obtained. Validity of the proposed random hysteresis PWM scheme is verified by some simulated and measured results     

Quantitative speed control for SRM drive using fuzzy adapted inverse model

Quantitative and robust speed control for a switched reluctance motor (SRM) drive is considered to be rather difficult and challenging owing to its highly nonlinear dynamic behavior. A speed control scheme having two-degree-of-freedom (2DOF) structure is developed here to improve the speed dynamic response of an SRM drive. In the proposed control scheme, the feedback controller is quantitatively designed to meet the desired regulation control requirements first. Then a reference model and a command feedforward controller based on an inverse plant model are employed to yield the desired tracking response at nominal case. As the variations of system parameters and operating conditions occur, the prescribed control specifications may not be satisfied any more. To improve this, the inverse model is adaptively tuned by a fuzzy control scheme so that the model-following tracking error is significantly reduced. In addition, a simple disturbance cancellation robust controller is added to improve the tracking and regulation control performances further.     

Development of three-phase switch-mode rectifier using single-phase modules

This paper presents a three-phase (3/spl phi/) switch-mode rectifier (SMR) consisting of three 1 /spl phi/ SMRs, two center-tapped autotransformers and three changeover switches. The ac input sides of three modules are /spl Delta/-connected, and their dc output sides are connected in parallel. As any one module fault occurs, the remaining two modules becomes modified T-connected and continuously perform three-phase rectification with good line drawn power quality. When two constituted 1/spl phi/ modules are faulted, the proposed 3/spl phi/ SMR will be operated as 1/spl phi/ SMR. The quantitative and robust voltage regulation controls for the developed SMR are made to consider the effects of changes of system parameters, operating condition, and number of connected modules.     

Improved field-weakening control for IFO induction motor

Generally, good transient response and high conversion efficiency of a field-weakened indirect field-oriented (IFO), induction motor drive are difficult to obtain simultaneously owing to their contradictory behaviors. Moreover, its operating performance is quite sensitive to the flux level, detuned effect, and parameter variations. An improved field-weakening control approach for an IFO induction motor drive is developed here. In the proposed method, the saturated magnetizing inductance is represented by a fitted quadratic polynomial of flux current. And the normal d-axis flux current command is composed of a no-load, a load-compensating, and a transient compensating component. The first one is represented by a third-order polynomial of rotor speed, which is estimated at no-load to consider the effects of nonlinear magnetizing inductance and the limitation of motor rated voltage. As for the latter two compensating current command components, they are utilized to further weaken the field such that current tracking performances during loaded cases and transient period can be improved. And hence the torque-generating capability is also enhanced accordingly. During steady-state operation, the slip angular speed command or the flux current command is tuned using the proposed approach to let the motor quickly reach a stable operating condition with better efficiency. Experimental results show that good dynamic responses and better energy conversion efficiencies can be simultaneously obtained by the proposed field-weakening control method.     

Dynamic modeling and controller design of flyback converter

The accurate dynamic modeling and quantitative controller design for an isolated converter with optocoupler isolation in its feedback loop are considered to be difficult issues, since the transfer characteristics of some blocks are highly nonlinear and difficult to be modeled analytically. First a current-mode controlled flyback converter with an optically isolated feedback path is designed. Then the equivalent control system block diagram is constructed, and its block transfer functions are found. To increase the accuracy, the dynamic models of some critical blocks are estimated from measurements. In order to facilitate the controller design, the model simplification is further made. Finally, based on the reduced dynamic model, a quantitative design procedure is derived to find the parameters of the voltage controller to meet the prescribed regulating specifications. Validity of the estimated dynamic model and the proposed controller design approach is demonstrated by some simulation and experimental results     

An adaptive controller for current-fed induction motor

A model reference speed adaptive controller for a current-fed induction motor drive is proposed. It uses a proportional-plus-integral (PI) adaptation to satisfy the hyperstability condition for taking care of the load and machine parameter changes of the drive. The available information on the states and output of the reference model as well as the plant output are all that are required for the control; no explicit parameter identification is needed. The controller can be designed by using a reduced reference model to simplify the design without much degradation of the performance, so that it is relatively easy to implement practically