Compensation Of Harmonic Disturbances Research Articles

Current Controller Design of Grid-Connected Inverter with Incomplete Observation Considering L-/LC-Type Grid Impedance

This paper presents a current control design for stabilizing an inductive-capacitive-inductive (LCL)-filtered grid-connected inverter (GCI) system under uncertain grid impedance and distorted grid environment. To deal with the negative impact of grid impedance, LC-type grid impedance is considered in both the system model derivation and controller design process of an LCL-filtered GCI system. In addition, the integral and resonant control terms are also augmented into the system model in the synchronous reference frame to guarantee the reference tracking of zero steady-state error and good harmonic disturbance compensation of the grid-injected currents from GCI. By considering the effect of grid impedance on the control design process, an incomplete state feedback controller will be designed based on the linear-quadratic regulator (LQR) without damaging the asymptotic stabilization and robustness of the GCI system under uncertain grid impedance. By means of the closed-loop pole map evaluation, the asymptotic stability, robustness, and resonance-damping capability of the proposed current control scheme are confirmed even when all the system states are not available. In order to reduce the number of required sensors for the realization of the controller, a discrete-time current-type full-state observer is employed in this paper to estimate the system state variables with high precision. The feasibility and effectiveness of the proposed control scheme are demonstrated by the PSIM simulations and experiments by using a three-phase GCI prototype system under adverse grid conditions. The comprehensive evaluation results show that the designed control scheme maintains the stability and robustness of the LCL-filtered GCI when connecting to unexpected grids, such as harmonic distortion and L-type and LC-type grid impedances. As a result, the proposed control scheme successfully stabilizes the entire GCI system with high-quality grid-injected currents even when the GCI faces severe grid distortions and an extra grid dynamic caused by the L-type or LC-type grid impedance. Furthermore, low-order distortion harmonics come from the background grid voltages and are maintained as acceptable limits according to the IEEE Std. 1547-2003. Comparative test result with the conventional one also confirms the effectiveness of the proposed control scheme under LC-type grid impedance thanks to the consideration of LC grid impedance in the design process.

Parameter estimation of biased harmonic signal

This paper deals with the problem of asymptotically estimating amplitude, frequency and phase of a sinusoidal signal by adopting the theory of invariant relations proposed in analytical mechanics [8] and further investigated in [9, 10] (see also [11]). The problem of frequency, amplitude and phase estimation of a sinusoidal signal has attracted a remarkable research attention in the past and current literature. The reasons of this interest rely on several engineering applications where an effective and robust solution to this problem is crucial. To mention few, it is worth mentioning problems of harmonic disturbance compensation in automatic control, design of phase-looked loop circuits in telecommunication, adaptive filtering in signal processing, etc. In principle, the method of least squares, Fourier analysis, Laplace transform provide a potential solution to the corresponding problems. However, these methods may not be suitable, for example, for control algorithms with real-time data processing. The goal of this paper is to suggest a further contribution to this task by showing how to solve the problem at hand through the observer’s theory. The method of invariant relations is used for the asymptotically observation scheme design. This aproach is based on dynamical extension of original system and construct of appropriate invariant relations, from which the unknowns variables can be expressed as a functions of the known quantities on the trajectories of extended system. The final synthesis is carried out from the condition of obtaining asymptotic estimates of unknown parameters. It is shown that an asymptotic estimate of the unknown states can be obtained by rendering attractive an appropriately selected invariant manifold in the extended state space. The asymptotic convergence of the estimates of the sought phase vector components to their true value is proved. The simulation results demonstrate the effectiveness of the proposed method of solving the state observation problem of the harmonic oscillator. It should be noted that a more general approach, which forms an appropriate method for solving observation problems for nonlinear dynamical systems due to the synthesis of invariant manifold, was proposed as a modification of the I&I method (Input and Invariance) of stabilization of nonlinear systems in [12, 13].

Harmonic Disturbance Compensation of a System With Long Dead-Time, Design and Experimental Validation

An internal model control scheme is proposed to compensate both a long dead-time of a system and a harmonic disturbance. The controller is based on an inversion of the first-order model used to approximate the system dynamics together with an input delay. Two other components of the controller consist of a filter and an additional delay by which the harmonic modes are targeted via adjusting the control loop gain and phase shift. The design of the filter-delay pair is fully analytical and the implementation of the scheme is straightforward. The main attention is paid to the complete compensation of a single-harmonic disturbance. Besides, an extension of the scheme is proposed to target a double harmonic disturbance. Increased attention is paid to the robustness aspects of the schemes. Outstanding performance in terms of harmonic disturbance compensation of the proposed schemes is demonstrated on a series of laboratory experiments.

Observer of harmonic oscillator parameters

This paper deals with the problem of asymptotically estimating amplitude, frequency and phase of a sinusoidal signal by adopting the theory of invariant relations proposed in analytical mechanics [8] and further investigated in [9], [10] (see also [11]). The problem of frequency, amplitude and phase estimation of a sinusoidal signal has attracted a remarkable research attention in the past and current literature. The reasons of this interest rely on several engineering applications where an effective and robust solution to this problem is crucial. To mention few, it is worth mentioning problems of harmonic disturbance compensation in automatic control, design of phase-looked loop circuits in telecommunication, adaptive filtering in signal processing, etc. In principle, the method of least squares, Fourier analysis, Laplace transform provide a potential solution to the corresponding problems. However, these methods may not be suitable, for example, for control algorithms with real-time data processing. The goal of this paper is to suggest a further contribution to this task by showing how to solve the problem at hand through the observer’s theory. The method of invariant relations is used for the asymptotically observation scheme design. This aproach is based on dynamical extension of original system and construct of appropriate invariant relations, from which the unknowns variables can be expressed as a functions of the known quantities on the trajectories of extended system. The final synthesis is carried out from the condition of obtaining asymptotic estimates of unknown parameters. It is shown that an asymptotic estimate of the unknown states can be obtained by rendering attractive an appropriately selected invariant manifold in the extended state space. The asymptotic convergence of the estimates of the sought phase vector components to their true value is proved. The simulation results demonstrate the effectiveness of the proposed method of solving the state observation problem of the harmonic oscillator. It should be noted that a more general approach, which forms an appropriate method for solving observation problems for nonlinear dynamical systems due to the synthesis of invariant manifold, was proposed as a modification of the I\&I method (Input and Invariance) of stabilization of nonlinear systems in [12, 13].

Adaptive Internal Model-Based Harmonic Control for Active Torsional Vibration Reduction

This paper proposes a method for the compensation of harmonic disturbances with parametrically varying frequencies for linear time-invariant (LTI) plants. Torsional oscillations arising from cyclic irregularity is an inherent problem of the internal combustion engine (ICE) powered automotive powertrains. The ICE due to its cyclic combustion process generates periodic disturbances whose frequency varies with its operating speed. Furthermore, the amplitude of the oscillatory torque depends on the demanded set-point torque and the speed of operation. The objective of the controller is to reduce the effect of disturbances resulting in a reduction of oscillatory motion quantities using external actuation. The proposed scheme uses a harmonic controller to command input of the compensating actuators. Torsional vibration systems are studied, in which the effect of disturbance torques resulting in speed oscillations are reduced using the commanded compensation torque. The developed controller is evaluated using simulations and validated with experiments using a two-cylinder gasoline engine at a powerpack test bench.

Compensation of harmonic disturbances in piezoelastic structures

The use of self-sensing piezoelectric actuators in smart structures means collocation of actuator and sensor. The measured electric current carries contributions from an electrical and mechanical subsystem. The latter contribution is due to the direct piezoelectric effect that is used for the purpose of vibration control. This procedure requires the robust separation of the electric current due to the direct piezoelectric effect from the measured electric current. Due to the unfavourable ratio of these two signals, the design of an observer for the electric current due to the direct piezoelectric effect is proposed. The control design for the purpose of harmonic disturbance suppression is based on an internal model approach and is facilitated by the special structure of the underlying mathematical model. Stability issues with respect to the distributed parameter system are resolved by applying the concepts of passivity and stability in conjunction with the small gain theorem. The control concept is evaluated by exciting the piezoelastic structure under investigation at a dominant eigenfrequency.

Compensation of harmonic disturbances in nonlinear plants with parametric and functional uncertainty

Methods of compensation of harmonic disturbances from the measurements of the output variable are developed for nonlinear plants with parametric and functional uncertainty. A new control algorithm is proposed, which outperforms known methods in simplicity of implementation and some other characteristics.

Compensation of Harmonic Disturbance for Nonlinear Plant with Parametric and Functional Uncertainty

AbstractThis paper devoted to the disturbance cancellation problem for the nonlinear plant. We present a new output control approach of harmonic disturbance compensation. The proposed control law is easier to implement and outperform known analogs by some characteristics.

하드 디스크 드라이브에서 나이퀴스트 주파수 안의 고조파 외란 보상

This paper describes new harmonic disturbance compensation based on a peak filter array for Hard Disk Drives. Unlike a conventional method, the proposed method does not require any sin/cos functions or tables and reduces effects of all harmonic disturbances within a nyquist frequency. Two factors are introduced to parameterize stability and a gain tune. In addition, it is verified that the order of the proposed filter is minimal. From 600 experimental results, 8.5% performance improvement is achieved.

Output control algorithm with the compensation of biased harmonic disturbances

The paper develops the methods of harmonic disturbance compensation using the measurements of plant output variable. An approach for biased harmonic disturbance compensation is proposed. This approach is superior to known ones in some characteristics.

A robust adaptive feedforward method for the compensation of harmonic disturbances

Most of disk drives suffer from various disturbances that degrade read–write performances. As the track density rapidly increases, basic drive functions may fail even with a small scale disturbance in a normal operating environment. For the reason, an accurate identification of the repeatable runout (RRO) of a hard disk drive has been one of the most important tasks for the successful servo designs in modern hard disk drive integration. Extensive research efforts have been dedicated for the compensation of the runouts and produced many successful strategies to minimize the influences to the critical basic drive functions. Primarily for the simple implementation and the cost reduction in the actual drive development and manufacturing, most of the developed methods being used in the actual drive integration are preferred to be formulated on time domain or frequency domain with very basic limited functions. The primitive frequency domain approaches usually require extensive calculations and large physical memories. In the present work, a RRO compensation method that combines advantages of the transient Fourier coefficients (TFC) and the least mean square (LMS) update is introduced. Combining the two methods in a proper fashion, the present work provides many benefits for the drive design and outperforms the previous compensation methods. The proposed method requires significantly less amount of computational work and physical memories compared to the conventional runout compensation methods. And it also provides effective frequency component selectivity so that the compensation resources are to be concentrated to a specific problem reason. Comprehensive frequency domain formulation of the method followed by a series of experimental test results is provided in the present article.

A hybrid formulation for blended adaptive feedforward and feedback closed-loop control

Development and implementation of a novel control algorithm, suitable for active vibration control (AVC) or active structural acoustic control (ASAC), is introduced in this paper. The hybrid algorithm combines the closed-loop properties of the stochastically optimal linear quadratic Gaussian (LQG) design with the robust filtered-X LMS (FXLMS) adaptive algorithm. The resulting compensator provides active damping of plant poles in combination with optimal suppression of persistent disturbances. It is shown that the inclusion of a FXLMS compensator in the forward path leads to more robust harmonic disturbance compensation than is practical for completely feedback-based (e.g., LQG disturbance modeling) techniques. Additionally, the pole-placement properties retained in the hybrid controller provide simultaneous suppression of transient disturbances. The hybrid paradigm uses the Kalman filter estimate of the plant disturbance for the reference signal to the FXLMS block. This nice feature makes the hybrid controller practical for structures where an adequate reference signal is not readily available. Theoretical development of the hybrid controller equations are presented along with a demonstration of a hybrid AVC controller on a simply supported plate. [Work supported by ONR.]