High power factor AC/DC/AC converter with random PWM

A three-phase AC/DC/AC converter is presented with a power factor preregulator to improve the power quality in the input side and a pseudorandom noise generator to reduce the emitted acoustic noise and the mechanical vibration for an induction motor drive. The space vector modulation with hysteresis current control for a voltage source rectifier is adopted to simplify the hardware circuit. A control scheme is presented to drive the supply current following the reference current. The amplitude of reference current for the pulsewidth modulation (PWM) rectifier is derived from the DC bus voltage regulator and the estimated output power. Random switching frequency technique for a three-phase PWM inverter system to reduce the annoying tonal noise and resonant vibration from an induction motor is described. By randomly varying the instantaneous PWM switching frequency from one cycle to the next, the frequency distribution of harmonics is spread in a wide frequency range. The major advantage for using such a strategy is the nonrepetitive output spectral characteristic that results in reduction of torque pulsations in motor drive systems. The nearly unity power factor at the three-phase rectifier and the absence of acoustic noise concentrated at the specific tones which is usually present with conventional sinusoidal modulation are verified by the experimental tests     

Single-phase power-factor-correction AC/DC converters with threePWM control schemes

Three pulse-width modulation (PWM) control schemes for a single-phase power-factor-correction (PFC) AC/DC converter are presented to improve the power quality. A diode bridge with two power switches is employed as a PFC circuit to achieve a high power factor and low line current harmonic distortion. The control schemes are based on look-up tables with hysteresis current controller (HCC) to generate two-level or three-level PWM on the DC side of diode rectifier. Based on the proposed three control schemes, the line current is driven to follow the sinusoidal current command which is in phase with the supply voltage, and two capacitor voltages on the DC bus are controlled to be balanced. The simulation and experimental results of a 1 kW converter with load as well as line voltage variation and shown to verify the proposed control schemes. It is shown that unity PFC is achieved using a simple control circuit and the measured line current harmonics satisfy the IEC 1000-3-2 requirements     

Full control of a PWM DC-AC converter for AC voltage regulation

The design and implement action of a DSP-based fully digital-controlled single-phase pulsewidth modulated (PWM) dc-ac converter for ac voltage regulation is described. The proposed multiloop digital controller (MDC) consists of a current controller, a voltage controller, and a feedforward controller. This MDC was realized using a single-chip digital signal processor (DSP). The PWM gating signals are determined at every sampling instant by the proposed multiloop digital control scheme using a set of detected feedback signals. A software current control; scheme has been developed to achieve fast current control of the PWM inverter and decouple the inductor of the output filter. Experimental results have been given to verify the proposed digital control scheme. The constructed DSP-based PWM dc-ac converter system can achieve fast dynamic response and with low total harmonic distortion (THD) for rectifier type of loads     

Sliding mode control of reaction flywheel-based brushless DC motor with buck converter

Reaction flywheel is a significant actuator for satellites’ attitude control. To improve output torque and rotational speed accuracy for reaction flywheel, this paper reviews the modeling and control approaches of DC-DC converters and presents an application of the variable structure system theory with associated sliding regimes. Firstly, the topology of reaction flywheel is constructed. The small signal linearization process for a buck converter is illustrated. Then, based on the state averaging models and reaching qualification expressed by the Lee derivative, the general results of the sliding mode control (SMC) are analyzed. The analytical equivalent control laws for reaction flywheel are deduced detailedly by selecting various sliding surfaces at electromotion, energy consumption braking, reverse connection braking stages. Finally, numerical and experimental examples are presented for illustrative purposes. The results demonstrate that favorable agreement is established between the simulations and experiments. The proposed control strategy achieves preferable rotational speed regulation, strong rejection of modest disturbances, and high-precision output torque and rotational speed tracking abilities.     

基于PWM控制器ISL6752大功率DC/DC变换器的研究

以一种新型的PWM控制器-ISL6752为核心,对其控制机理进行分析,在Simplorer7.0仿真平台基础上建立了其内部关键子模块的模型,进行理论设计与系统综合仿真,并以一台48V/20A的原理样机为例进行验证对比,其模型对于原理性分析以及设计控制网络的参数具有重要的指导价值。     

Improved DC/AC interface inverter for high-frequency spaceapplications

A DC/AC interface inverter for a high-frequency space power distribution system that uses dual asymmetrical resonant bridges is examined. Compared to the conventional approach in which two symmetrical bridges are used, the asymmetrical bridges arrangement offers better use of the installed kVA rating and efficiency of the inverter system. A simplified approach for modeling the inverter system in steady-state is presented, and a criteria to select the resonant components is given. A detailed simulation is performed for the following: a symmetrical inverter system with a resistive load, an asymmetrical inverter system with a resistive load, and an asymmetrical inverter system with the type-1A AC/DC converter load     

Novel single-switch converter with power factor correction

A new single-stage single-switch power factor correction converter with output electrical isolation is presented. The configuration of this converter is achieved by combining a flyback circuit and a forward circuit in one power stage. The principle of operation and steady-state analysis of the proposed topology is given. Based on its steady-state operation constraints, a design procedure along with a specific design example is reported. To verify the theoretical analysis of the proposed converter, a design example is given with its PSPICE simulation and experimental results     

DC/AC High Power Cell Structure Improves Sine Generator Performance

A new generation of dc/ac sine generators, based on dc/dc, pulse-width modulation (PWM) storage converter structure operating with rectified sine wave control and associated with a controlled bridge, is described. The efficiency, harmonic distortion, and transien't behavior are better in dc/dc sine convertors than conventional dc/ac sine convertors. Continuous non-linear or linear methods previously described can be extended to design this structure.     

Integrated power and attitude control with two flywheels

Energy storage and attitude control are two distinct subsystems of the typical satellite. Energy storage is provided using batteries and active attitude control is accomplished with control moment gyroscopes or reaction wheels. A system mass savings can be achieved if these two subsystems are combined using multiple flywheels for simultaneous kinetic energy storage and momentum transfer. This paper develops, simulates, and experimentally demonstrates the control algorithms to accomplish integrated power and single-axis attitude control using two flywheels.     

Parallel resonant converter with LLC-type commutation

It is shown that by using a proper transformation of state variables, the third-order system of the parallel resonant converter (PRC) with LLC-type commutation can be analyzed by means of a two-dimensional state-plane diagram. A set of characteristic curves which can be used for the converter design is derived from the analysis. It is shown from these curves that the converter possesses more desirable features than the conventional PRC     

Transonic buffet control research with two types of shock control bump based on RAE2822 airfoil

Current research shows that the traditional shock control bump (SCB) can weaken the intensity of shock and better the transonic buffet performance.The author finds that when SCB is placed downstream of the shock,it can decrease the adverse pressure gradient.This may prevent the shock foot separation bubble to merge with the trailing edge separation and finally improve the buffet performance.Based on RAE2822 airfoil,two types of SCB are designed according to the two different mechanisms.By using Reynolds-averaged Navier-Stokes (RANS) and unsteady Reynolds-averaged Navier-Stokes (URANS) methods to analyze the properties of RAE2822 airfoil with and without SCB,the results show that the downstream SCB can better the buffet performance under a wide range of freestream Mach number and the steady aerodynamics characteristic is similar to that of RAE2822 airfoil.The traditional SCB can only weaken the intensity of the shock under the design condition.Under the off-design conditions,the SCB does not do much to or even worsen the buffet performance.Indeed,the use of backward bump can flatten the leeward side of the airfoil,and this is similar to the mechanism that supercritical airfoil can weaken the recompression of shock wave.     

Tunnel/predictor display with two-axis control coordination and simplification

A longitudinal-lateral control coordination and simplification concept is considered for a tunnel/predictor display, which presents the command flight path and a specified future aircraft position in a 3-dimensional format to the pilot, for improving flight path control. A basic element of the proposed concept is the generation of common longitudinal-lateral transfer characteristics of the predictor-aircraft system for the crossover frequency region. Control coordination is supported by a dynamics similarity between the longitudinal and the lateral response characteristics of the predictor position in closed-loop pilot control actions. The control coordination and simplification concept is considered to support the pilot in manual flight path control, directed at an enhancement of his control performance and at a reduction of his workload. Results from pilot-in-the-loop simulation experiments support the theoretical findings and show the effectiveness of the proposed predictor concept with control coordination.     

Large-eddy simulation of shock-wave/turbulent boundary layer interaction with and without SparkJet control

The efficiency and mechanism of an active control device ‘‘Spark Jet" and its application in shock-induced separation control are studied using large-eddy simulation in this paper.The base flow is the interaction of an oblique shock-wave generated by 8° wedge and a spatially-developing Ma = 2.3 turbulent boundary layer.The Reynolds number based on the incoming flow property and the boundary layer displacement thickness at the impinging point without shock-wave is20000.The detailed numerical approaches were presented.The inflow turbulence was generated using the digital filter method to avoid artificial temporal or streamwise periodicity.The numerical results including velocity profile,Reynolds stress profile,skin friction,and wall pressure were systematically validated against the available wind tunnel particle image velocimetry(PIV) measurements of the same flow condition.Further study on the control of flow separation due to the strong shock-viscous interaction using an active control actuator ‘‘Spark Jet" was conducted.The single-pulsed characteristic of the device was obtained and compared with the experiment.Both instantaneous and time-averaged flow fields have shown that the jet flow issuing from the actuator cavity enhances the flow mixing inside the boundary layer,making the boundary layer more resistant to flow separation.Skin friction coefficient distribution shows that the separation bubble length is reduced by about 35% with control exerted.