Plug-in Repetitive Controller Research Articles

Multirate Repetitive Control for PWM DC/AC Converters

In this paper, a multirate repetitive control (RC) scheme is developed and applied to constant-voltage constant-frequency pulsewidth modulation converter systems. In this scheme, the converter has a fast sampling rate, while the repetitive controller has a reduced sampling rate. The learning is based on the downsampled input and error signals in previous periods. The multirate RC synthesis method, as well as its convergence and stability conditions, is discussed in detail. Systematic experiments are also carried out to illustrate the effectiveness of multirate RC. Experimental results show that, with a well-designed multirate RC, the total harmonic distortion can be very low. This approach can reduce the computation delay caused by the plug-in RC in each switching control period and will enhance the system stability. Consequently, the switching control frequency of the converter can be increased to compensate the control performance loss. This approach is suitable for design of cost-effective and flexible converter control systems.

Circulating Harmonic Current Elimination of a CPS-PWM-Based Modular Multilevel Converter With a Plug-In Repetitive Controller

An improved circulating current control method by applying a digital plug-in repetitive controller is discussed for harmonic elimination of a carrier-phase-shift pulse-width-modulation (CPS-PWM)-based modular multilevel converter (MMC) in this paper. The performance of the controller is analyzed in detail based on an improved circulating current control model with the consideration of the submodule voltage disturbance. It is shown that the proposed control method has the merits of simplicity, versatility, and better performance of circulating harmonic current elimination than the traditional proportional integral controller. The stability analysis of the proposed method are also discussed in the paper as well as the design principles. Finally, the experimental results including the steady-state performance and the transient response are given, which validates the feasibility and excellent performance of the proposed control scheme.

New Repetitive Control With Improved Steady-State Performance and Accelerated Transient

In repetitive control (RC), the enhanced servo performance at the fundamental frequency and its higher order harmonics is usually followed by undesired error amplifications at other frequencies. In this paper, we discuss a new structural configuration of the internal model in RC, wherein designers have more flexibility in the repetitive loop-shaping design, and the amplification of nonrepetitive errors can be largely reduced. Compared to conventional RC, the proposed scheme is especially advantageous when the repetitive task is subject to large amounts of nonperiodic disturbances. An additional benefit is that the transient response of this plug-in RC can be easily controlled, leading to an accelerated transient with reduced overshoots. Verification of the algorithm is provided by simulation of a benchmark regulation problem in hard disk drives, and by tracking-control experiments on a laboratory testbed of an industrial wafer scanner.

Research on fast transient and 6 n ±1 harmonics suppressing repetitive control scheme for three‐phase grid‐connected inverters

The repetitive control technique is widely adopted in ac systems, because of its excellent steady-state tracking performance and low total harmonic distortion. The repetitive control method with one-sixth of the system fundamental period T0 as the delay time has been proposed to achieve fast transient response. In this study, an improved control scheme based on the T0/6 repetitive control is proposed for three-phase grid-connected inverters. The proposed scheme adopts T0/6 as the delay time in the positive-rotating and negative-rotating synchronous reference frames to suppress the 6n ± 1 harmonics. Meanwhile, the proportional-integral regulator and the plug-in repetitive controller are combined to reinforce the system performance. A new auxiliary function based on the linear interpolation is proposed to maintain the ideal repetitive control performance when one-sixth of the ratio of the sampling frequency to the grid fundamental frequency is non-integer. The effectiveness of the proposed scheme on improving the T0/6 repetitive control is confirmed by simulation and experimental results finally.

Repetitive control of a trilayer conjugated polymer actuator

This paper investigates the dynamics of a polypyrrole-based conducting electroactive polymer actuator which is desired to track repeating reference commands for position control applications. A proportional-integral (PI) control assisted plug-in repetitive controller is proposed and implemented to improve the tracking performance of the polypyrrole actuator. The response of the system with repetitive controller is then compared to the system response which is solely obtained by the implementation of the PI controller. The results show that the repetitive controller improves the tracking performance of the actuator significantly and reduces the steady-state tracking errors compared to the stand-alone PI controller.

Digital Plug-In Repetitive Controller for Single-Phase Bridgeless PFC Converters

This paper investigates a plug-in repetitive control scheme for bridgeless power factor correction (PFC) converters to mitigate input current distortions under continuous conduction mode and discontinuous conduction mode operating conditions. From the PFC converter model and the fact that a type-II compensator is used, a design methodology to maximize the bandwidth of the feedback controller is suggested. After that, the error transfer function including the feedback controller is derived, and the stability of the repetitive control scheme is evaluated using the error transfer function. The implementation of the digital repetitive controller is also discussed. The simulation and experimental results show that the input current THD is significantly improved by using the proposed control scheme for a 1-kW single-phase bridgeless PFC converter prototype.

Grid-Connected Boost-Half-Bridge Photovoltaic Microinverter System Using Repetitive Current Control and Maximum Power Point Tracking

This paper presents a novel grid-connected boost-half-bridge photovoltaic (PV) microinverter system and its control implementations. In order to achieve low cost, easy control, high efficiency, and high reliability, a boost-half-bridge dc-dc converter using minimal devices is introduced to interface the low-voltage PV module. A full-bridge pulsewidth-modulated inverter is cascaded and injects synchronized sinusoidal current to the grid. Moreover, a plug-in repetitive current controller based on a fourth-order linear-phase IIR filter is proposed to regulate the grid current. High power factor and very low total harmonic distortions are guaranteed under both heavy load and light load conditions. Dynamic stiffness is achieved when load or solar irradiance is changing rapidly. In addition, the dynamic behavior of the boost-half-bridge dc-dc converter is analyzed; a customized maximum power point tracking (MPPT) method, which generates a ramp-changed PV voltage reference is developed accordingly. Variable step size is adopted such that fast tracking speed and high MPPT efficiency are both obtained. A 210 W prototype was fabricated and tested. Simulation and experimental results are provided to verify the validity and performance of the circuit operations, current control, and MPPT algorithm.

Two-Period Repetitive and Adaptive Control for Repeatable and Nonrepeatable Runout Compensation in Disk Drive Track Following

This paper presents the design and implementation of an integrated two-period repetitive and adaptive control scheme to reject both repeatable and nonrepeatable disturbances in the track-following servo control of a hard disk drive read-write head. A baseline linear quadratic Gaussian controller is augmented by a plug-in repetitive controller to reject periodic disturbances with two periods, one that is synchronized with the disk rotation and the other that is not, and an additional adaptive-Q control scheme to reject the remaining aperiodic and random disturbances. The adaptive-Q control algorithm uses the well-known result that all stabilizing controllers for a plant can be synthesized by conveniently parameterized augmentation to a nominal controller. The Q-filter is restricted to a finite impulse response filter, which minimizes the root-mean-square value of the track-following error. Experimental results show substantial performance improvement for the two-stage augmented controller over the single-stage repetitive or adaptive-Q control acting alone.

Design and control of a fast tool servo used in noncircular piston turning process

Noncircular pistons are becoming more and more popular in the automotive industry. The challenge of machining this kind of pistons (e.g., middle-convex and varying ellipse piston (MCVEP)), lies in the rigorous demand of the cutting feed mechanism for large force generation, high stiffness, fast response, long stroke and high accuracy. The conventional processing methods cannot meet the challenge so a new piezoelectric actuator (PEA) based fast tool servo (FTS) mechanism was developed to incorporate additional functions to a general CNC system that will facilitate the execution of MCVEP turning. Since the desired tool trajectories are approximately periodic signals in MCVEP turning, and the repetitive control can achieve asymptotic tracking and disturbance rejection of periodic signals, a plug-in repetitive control is designed to be added on the conventional PID controller. In the experiments, the designed prototype was used to machine a MCVEP for the gasoline engine, which was equipped with the PEA-based FTS system, as well as the plug-in repetitive controller. The machining test validated the effective of the designed noncircular turning system.

Design of a Plug-In Repetitive Control Scheme for Eliminating Supply-Side Current Harmonics of Three-Phase PWM Boost Rectifiers Under Generalized Supply Voltage Conditions

This paper presents a digital repetitive control (RC) scheme to minimize the even-order harmonics at the dc link voltage and odd-order harmonics in the line-side currents under distorted and unbalanced supply voltage conditions. The proposed current control scheme consists of a conventional PI and a plug-in repetitive controller. On the basis of the mathematical model of the three-phase pulsewidth-modulated (PWM) boost rectifier under the generalized supply voltage conditions, the control task is divided into: 1) dc-link voltage harmonics control and 2) line-side current harmonics control . In the voltage harmonics control scheme, a reference current calculation algorithm has been derived accordingly to ensure that the dc link voltage is maintained constant at the demanded value and the supply-side power factor is kept close to unity. In the line-side current harmonics control scheme, a plug-in repetitive controller is designed to achieve low total harmonic distortion (THD) line-side currents of the three-phase PWM boost rectifier. The experimental test results obtained from a 1.6-kVA laboratory-based PWM rectifier confirm that the proposed control scheme can reduce the line-side current THD from 16.63% to 4.70%, and improve the dc-link voltage tracking accuracy substantially over the conventional PI-based controller.

Design method of single-phase inverters for UPS systems

This article presents the complete design of a low power voltage source inverter (VSI) dedicated for a UPS system. The analysis of the rectangular PWM-AC voltage spectrum allows for a choice of the basic architecture of the inverter. Output filter parameters were calculated to reduce the maximum amplitude of the output VSI voltage harmonics for the steady-state inverter mode. The choice of the feedback loop type was based on a discussion of the inverter output impedance using a continuous model of the inverter. The parameters of the inner loop digital control for the discrete inverter model were calculated using the Coefficient Diagram Method. The influence of the step load was modelled. The time constant of the inverter closed loop system was selected to ensure sufficient system robustness. An outer feedback loop with a plug-in repetitive controller, simplified owing to the properties of the PID/CDM inner loop control, was introduced to eliminate the periodic disturbances generated by the non-linear rectifier load and the deadtime influence. The experimental verification of the design method is presented.

DC Link Voltage and Supply-Side Current HarmonicsMinimization of Three Phase PWM BoostRectifiers Using Frequency Domain BasedRepetitive Current Controllers

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper presents a digital plug-in frequency domain based repetitive control scheme for minimizing the odd order harmonics in the supply line side currents of the three phase pulsewidth modulation (PWM) boost rectifier under the distorted and unbalanced supply voltage conditions. Based on the mathematical model of the three-phase PWM boost rectifier under the generalized supply voltage conditions, the control task is divided into: (a) dc-link voltage harmonics control and (b)supply line side current harmonics control. The proposed plug-in repetitive controller together with the conventional PI controller is designed to achieve supply line side currents with low total harmonic distortion (THD) for the three phase PWM boost rectifier. The repetitive control learning algorithm is implemented in the frequency domain by means of Fourier series approximation, instead of commonly used time domain based scheme, and provides the flexibility of choosing different learning gains and phase angle delay compensations individually for each harmonic component. The experimental test results obtained from a 1.6 kVA laboratory based PWM rectifier confirm that the THD of the supply line side currents can be reduced from 21.09% to 4.12% with the plug-in frequency domain based repetitive current controllers. </para>

Frequency Domain Based Repetitive Control of Three Phase Boost PWM Rectifier Under Distorted Supply Voltage Conditions

This paper presents a digital plug-in frequency domain based repetitive control scheme for minimizing the even order harmonics at the output dc link voltage and odd order harmonics in the line currents under the distorted and unbalanced supply voltage conditions. The proposed current controller consists of a conventional PI controller and a frequency domain based plug-in repetitive controller. Based on the mathematical model of the three-phase PWM boost rectifier under the generalized supply voltage conditions, the control task is divided into: (a)dc-link voltage harmonics control and (b)line side current harmonics control. The plug-in repetitive controller is designed to achieve line side currents with low THD for the three phase PWM boost rectifier. The repetitive control learning algorithm is designed in frequency domain instead of commonly used time domain and provides the flexibility of choosing different learning gains and phase delay compensations individually for each harmonic component. The experimental test results obtained from a 1.6 kVA laboratory based PWM rectifier confirm that the THD of the line side current can be reduced from 21.09% to 4.12% with the insertion of the plug-in frequency domain based repetitive controller.

Analysis and estimation of tracking errors of plug-in type repetitive control systems

Subject to stability constraints, tracking performance of a plug-in type repetitive control system with periodic inputs is explored in this note. An upper bound for the square integral of the tracking error over one time period of periodic input signals is derived based on Fourier analysis. The magnitude and the decay rate of the tracking error can be estimated using the harmonics of the input signal within the designed bandwidth. Both computer simulations and experimental results are presented to illustrate the effectiveness of the proposed method. It is also shown that the tracking error can decay significantly in the first two time periods in the proposed repetitive control system if the required bandwidth conditions are satisfied.

Digital repetitive controlled three-phase PWM rectifier

In this paper, a digital repetitive control (RC) strategy is proposed to achieve zero tracking error for constant-voltage constant-frequency (CVCF) pulse width modulation (PWM) converters. The proposed control scheme is of structure: a plug-in digital repetitive controller plus a conventional controller (e.g., PD controller). The design of the plug-in repetitive learning controller is systematically developed. The stability analysis of overall system is discussed. A repetitive controlled three-phase reversible PWM rectifier is given as an application example. Near unity power factor and constant output DC voltage are ensured under parameter uncertainties and load disturbances. Simulation and experimental results are provided to testify the effectiveness of the proposed control scheme.

Digital repetitive learning controller for three-phase CVCF PWM inverter

In this paper, a plug-in digital repetitive leaning control scheme is proposed for three-phase constant-voltage constant-frequency (CVCF) pulsewidth modulation inverters to achieve high-quality sinusoidal output voltages. In the proposed control scheme, the repetitive controller (RC) is plugged into the stable one-sampling-ahead-preview-controlled three-phase CVCF inverter system using only two voltage sensors. The RC is designed to eliminate periodic disturbance and/or track periodic reference signal with zero tracking error, The design theory of plug-in repetitive learning controller is described systematically and the stability analysis or overall system is discussed. The merits of the controlled systems include features of minimized total harmonic distortion, robustness to parameter uncertainties, fast response, and fewer sensors. Simulation and experimental results are provided to illustrate the effectiveness of the proposed scheme.