Zero Steady-state Error Research Articles

Multiple Discrete Adaptive Filter Based Position Error Reduction for Sensorless IPMSM Drives

The inverter nonlinearity and the flux spatial harmonics will lead to noticeable (6κ±1) harmonics in the observed back electromotive force (EMF), causing (6κ) pulsations in the rotor position estimation error and deteriorating the performance of sensorless interior permanent magnet synchronous motor (IPMSM) drives. To improve the sensorless IPMSM control accuracy, a multiple discrete adaptive filter (MDAF) embedded between sliding mode observer (SMO) and normalized quadrature phase-locked loop (PLL) is adopted to solve the above problem in this paper. The MDAF consists of a fundamental extraction block and a harmonic cancellation block. Harmonic cancellation works similarly to fundamental extraction, simply by removing the dominant 5th and 7th harmonics from the distorted back-EMF in a frequency multiplicative manner. The proposed algorithm is designed directly in the discrete domain, avoiding the complex discretization process. The open-loop amplitude-frequency characteristic curves show that the method is able to achieve infinite gain exactly at the expected frequency, thus allowing closed-loop zero steady-state error tracking of the back-EMF and providing higher precision for harmonic estimation. The excellent performance of the suggested method is validated based on a 1.5kW sensorless IPMSM control system.

Discrete Switching Sequence Control for Converter Reference Tracking With Zero Steady-State Errors

This letter proposes a discrete switching sequence control (dSSC) to achieve zero steady-state error tracking for L-type converters. Considering switching characteristics of power electronics, a discrete-time model is established and dSSC is designed step-by-step. A strict mathematical proof ensures that the proposed dSSC achieves reference tracking with zero steady-state errors. Meanwhile, the theoretical discussion shows that the expected dynamics is obtained by choosing the control parameter of dSSC. Compared with classical methods such as pulse width modulation (PWM) and model predictive control (MPC), the proposed dSSC systemically analyzes and designs the dynamics and steady-state accuracy of converters, from a switching theoretical viewpoint. Simulations and experiments verify the effectiveness of the proposed dSSC.

Low Earth Orbit Satellite Attitude Stabilization Using Linear Quadratic Regulator

This study compares the result of the PID controller to the LQR controller when used in the on-orbit stabilization of a satellite in the low earth orbit. The results from the PID controller show that the controller is too weak when used alone as the controller could not stabilize the system after 500 s which is not even allowable in practical application. For the LQR controller, a performance metric was set which is: i. the settling time is to be ≤ 10 seconds, ii. Maximum power consumption ≤ 1.5 Watts and iii. Zero (0) steady-state error / final value. The LQR controller meets system performance by achieving a settling time of roll (peak amplitude=0.26 s, settling time=10.0 s), Pitch (peak amplitude=0.395 s, settling time=5.52 s), Yaw (peak amplitude=0.350 s, settling time=5.52 s) and Total power consumption are 1.26 watt with a maximum torque of 3.22 mNm. Because power consumption and precision are critical in satellite applications, particularly military surveillance satellites. As a result, for an aerospace engineer to achieve their space mission, for instance, space mission like low earth orbit surveillance satellites, flexible solar panels, a high accuracy pointing accuracy, it will be impossible to adopt a PID controller except the engineer is ready for the complexity of design filters and compensators. An LQR design in this study can take care of all this complexity with minimum power consumption.

Model Identification and Control of a Buoyancy Change Device

There are several compelling reasons for exploring the ocean, for instance, the potential for accessing valuable resources, such as energy and minerals; establishing sovereignty; and addressing environmental issues. As a result, the scientific community has increasingly focused on the use of autonomous underwater vehicles (AUVs) for ocean exploration. Recent research has demonstrated that buoyancy change modules can greatly enhance the energy efficiency of these vehicles. However, the literature is scarce regarding the dynamic models of the vertical motion of buoyancy change modules. It is therefore difficult to develop adequate depth controllers, as this is a very complex task to perform in situ. The focus of this paper is to develop simplified linear models for a buoyancy change module that was previously designed by the authors. These models are experimentally identified and used to fine-tune depth controllers. Experimental results demonstrate that the controllers perform well, achieving a virtual zero steady-state error with satisfactory dynamic characteristics.

Zero Steady-state Error Tracking Control for Ball and Plate System Based on Principle of Internal Model

Zero Steady-state Error Tracking Control for Ball and Plate System Based on Principle of Internal Model

Composite Adaptive Synchronous Control of Dual-Drive Gantry Stage With Load Movement

In gantry systems, load usually moves according to different production tasks. The continuous change of the beam centroid position is a non-negligible factor for achieving high-performance synchronous control. Therefore, it cannot be simply treated as an external disturbance. In addition, advanced controller design and model parameter identification are very important for precision motion control systems. This article addresses the synchronous control of dual-drive gantry platforms with load movement to improve their steady-state and transient performance. Based on the analysis of the rigid and flexible characteristics of gantry mechanical components, a rigid-flexible coupling dynamic model is proposed, which provides a theoretical basis for the control system design. To ensure zero steady-state tracking error and parameter convergence in the presence of parameter uncertainties and unknown disturbances, a composite adaptive control method integrating excellent output tracking performance and parameter estimation is presented. Furthermore, the bridge between load movement and centroid position is established through frequency domain identification, which facilitates reasonable thrust distribution. Comparative experimental results are presented that confirm the effectiveness and advantages of the proposed synchronous control scheme.

Modeling of Automatic Generation Control and Automatic Voltage Regulator Under Generation Rate Constraint

As the interconnected power system transmits power from one area to another, the frequency will inevitable deviate from scheduled frequency. In addition, the active and reactive power demands continually change with rising and falling trend. Any mismatch between system generation and demand results in change in system frequency that is highly undesired. Excitation of generator must be regulated in order to match the power demand, otherwise the bus voltage may fall beyond the permitted limit. In this paper, a simulation model is developed for each component of AGC and AVR loops considering generator rate constraints. The response with GRC is compared with the analysis done without the Generation Rate Constraint. Although the frequency deviation is less with suitable controllers when the GRC is not considered, it is not the actual frequency deviation. When GRC is considered the actual frequency deviation can be found and then accordingly the controller is tuned. So that the desired frequency and power interchange with neighboring systems are maintained in order to minimize the transient deviations and to provide zero steady state error in appropriate short time. Further the role of automatic voltage control is to maintain the terminal voltage of synchronous generator in order to maintain the bus bar voltage Results are obtained using MATLAB SIMULINK software.

Analysis and design of flexible arc suppression device based on proportional series lagging control

Flexible arc suppression technology can control zero-sequence voltage flexibly and realize arc suppression completely by injecting current to the neutral point of distribution network. However, in the existing control method, PI control cannot achieve zero steady-state error, and injecting current control needs to accurately measure the phase-to-ground parameters, so it is difficult to apply it in practice. For improvement, a new control method of the flexible arc suppression device is developed by using proportional controller and lagging network controller in this paper. The double closed-loop control method and the parameters of the controller are designed to improve the injecting current control performance. The zero-sequence voltage is set as the control target of the control system to realize arc suppression completely without measuring the phase-to-ground parameters. The effectiveness of the proposed control technology is verified by PSIM simulation and practical experiments. The simulation and experimental results show that the proportional series lagging control has better response speed and stability than the existing control method.

Adaptive Control With Guaranteed Transient Behavior and Zero Steady-State Error for Systems With Time-Varying Parameters

It is nontrivial to achieve global zero-error regulation for uncertain nonlinear systems. The underlying problem becomes even more challenging if mismatched uncertainties and unknown time-varying control gain are involved, yet certain performance specifications are also pursued. In this work, we present an adaptive control method, which, without the persistent excitation (PE) condition, is able to ensure global zero-error regulation with guaranteed output performance for parametric strict-feedback systems involving fast time-varying parameters in the feedback path and input path. The development of our control scheme benefits from generalized <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$t$</tex> -dependent and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$x$</tex> -dependent functions, a novel coordinate transformation and “congelation of variables” method. Both theoretical analysis and numerical simulation verify the effectiveness and benefits of the proposed method.

Coupling between Automatic Generation Control and Automatic Voltage Regulator While Considering Generation Rate Constraint of Two Areas

This paper describes the implementation of automatic generation control (AGC) and automatic voltage regulator (AVR) under generation rate constraint (GRC) and coupling between automatic generation control and automatic voltage regulator while considering generation rate constrain of two areas for improve and better performance characteristic of load frequency control (LFC) problem. our control aim has to normalize the area control error (ACE), frequency error and tie-line power error in spite of the presences of system uncertainties and external load disturbance, So that the required frequency and power interchange with adjacent structures are maintained in order to reduce the transient deviations and to provide zero steady state error in proper short time, the behavior of the planned is checked by MATLAB SIMULINK software.

Deadbeat PQ Control for Islanded Smart Grids

The dynamic performance of smart (micro)grids depends on the proper selection of the controller gains and power-sharing parameters. This manuscript describes the control design to achieve a deadbeat desirable performance in terms of: i) Zero steady-state error. ii) Minimum rise time. iii) Minimum settling time. iv) Less than 2% overshoot/undershoot. This paper considers an Islanded microgrid system composed of two distributed generation (DG) units. Each DG unit includes three-phase pulse width modulation (PWM) inverter. The proposed controllers are proportional- integral (PI) type. The Controllers gains of the inverters and the Phase Locked Loop (PLL) parameters are designed to guarantee deadbeat dynamic performance in terms of minimal overshoot and system stability. The Particle Swarm Optimization (PSO) is used to tune the controller parameters of the current, PQ loops, and the PLL. The proposed controllers are compared with the traditional (Ziegler and Nichols), auto-tuned, and interior-point methods to shows the excellence of the proposed technique. Results authenticate and endorse the effectiveness of the proposed controllers and PLL design technique to achieve the desired deadbeat response of the study microgrid system.

Gain compensation approach for low‐voltage ride‐through and dynamic performance improvement of three‐phase type‐3 PLL

Despite the ability of type-3 phase-locked loop (PLL) to provide zero steady-state error when a three-phase voltage experiences frequency ramp change, its major drawback is slow dynamic performance and instability during voltage sag condition. In this paper, by obtaining the linearised model of PLL, instability associated with the presence of voltage amplitude within the PLL control loop is illustrated. Furthermore, analysis of two common techniques employed in improving PLL stability (high phase margin design and use of phase-lead compensator) is presented and their inapplicability to three-phase type-3 PLL is revealed. Thus, to address the said problems, a gain compensation technique is proposed in this paper. In the proposed approach, the PLL loop gain is adjusted by inserting a DC gain within the PLL control loop when the frequency of supply voltage deviates from its nominal value. The inserted DC gain compensates for reduction in voltage amplitude within the PLL control loop, thus, enhancing PLL's stability especially during voltage sags. Also, the gain increases PLL's bandwidth thereby improving its estimation speed. Effectiveness of the proposed solution is confirmed through experimental studies and it is compared with five existing type-3 PLL schemes and a type-2 PLL.

Stability analysis of single area power system considering parameter uncertainties

ABSTRACT In this work, the stability of a single area power system AVR loop is analysed in terms of specified gain and phase margin standpoint, by utilising an extended reduced-order observer (EROO). The design approach utilises a full-state feedback as well as an estimated signal for external disturbance (parametric uncertainties and disturbances due to change in load demands) to form the control law. Symmetric root locus (SRL) technique is used to assign the closed-loop poles (CLPs) of the system at desired locations by considering the stability margins. Parametric model uncertainty has been considered to demonstrate the robustness of control achieved by assigning a bound on the deviations in plant parameters. The proposed observer provides the estimates of unavailable states and state of the disturbance model in order to compensate system in the presence of external disturbances. The control scheme achieves performances satisfying the specified stability margins with asymptotic tracking and disturbance rejection property. The methodology provides control over peak values of the terminal voltage (with guaranteed zero steady-state errors) and control signal deviations which may be utilised to meet hardware constraints. Step by step design procedures with illustrative examples have been provided using MATLAB commands.

On Offset-Free Continuous Model Predictive Current Control of Permanent Magnet Synchronous Motors

In this work, an offset-free continuous control set model predictive current control (CCS-MPCC) strategy for synchronous machines based on a slack formulation of the Primal-Dual Interior-Point method is proposed. A horizon of two steps is achieved within 100 µs sampling period. To account for robustness against model mismatch and uncertainty, an incremental formulation of the MPC problem is used to ensure zero steady-state tracking error. The proposed controller is compared with the state of the art Field Oriented Control with PI controllers (FOC-PI), with the Deadbeat Model Predictive Current Control (DB-MPCC), and with the latter controller combined with discrete integrators in the feedback loop (DB-MPCC-I). Experimental results on a 0.5 kW PMSM prove that the proposed CCS-MPCC has outperformed the state of the art control techniques typically used to control electrical machines.

A Frequency-Adaptive Improved Moving-Average-Filter-Based Quasi-Type-1 PLL for Adverse Grid Conditions

The moving-average-filter-based quasi-type-1 phase-locked loop (MAF-QT1 PLL) can provide zero steady-state phase error in the presence of frequency drifts, achieving a high filtering capability. However, in the presence of an MAF and frequency drift, MAF-QT1 PLL cannot achieve a fast transient response and frequency-dependent characteristic under adverse grid conditions. To overcome this drawback of the MAF-QT1 PLL, this paper proposes a frequency-adaptive improved moving-average-filter-based quasi-type-1 PLL (FAIMAF-QT1 PLL). Aiming at the shortcoming of the slow dynamic response of the MAF-QT-1 PLL, a correction link is introduced, and an improved moving-average-filter-based quasi-type-1 PLL (IMAF-QT1 PLL) is obtained. To improve the anti-interference ability of the IMAF-QT1 PLL in response to grid frequency changes, a FAIMAF-QT1 PLL and a corresponding digital implementation scheme are proposed. The regulator parameter setting method is proposed based on the small-signal model of the FAIMAF-QT1 PLL. Simulation and experimental results show that the FAIMAF-QT1 PLL can accurately track the grid voltage phase in the presence of power grid frequency fluctuations, phase angle jumps, distorted harmonic injections and unbalanced voltage drops and has good steady-state and dynamic performance.

A Comprehensive Survey on Use of Soft Computing and Optimization Techniques for Load Frequency Control

Load frequency control (LFC) is one of the most profitable ancillary services of power system market presently. The main goal of LFC is to reduce zero steady-state error for frequency deviations. In the present review paper of LFC problem, worldwide history of various types of controllers, control strategy, smart techniques and methodologies which are implemented and which can be implemented at generation, transmission and distribution areas of a power system. Moreover, ABT mechanism in India is implemented in 2002 to regulate grid frequency. Out of this in deregulated power system energy storage with the potential of different types of energy storage at distribution area in the power system has been highlighted. In a smart grid due to intermittent nature of the renewable energy sources (wind and solar), unpredictable daily and seasonal variations there may be an imbalance between supply and demand which results in deviations in the grid frequency. To eliminate the problem of LFC Electrical energy storage (EES) is technologies are listed. LFC problem with different soft computing techniques such as Genetic Algorithm (GA), Neural Network (NN), Fuzzy Logic (FG), Particle Swarm Optimization (PSO), Bacterial Foraging Optimization (BFP), Tabu Search Algorithm (TSA) has been carried out. This literature review will help the new researcher to give the guideline to work in the area of load frequency control.

Dual Phase-Locked Loop-Based Speed Estimation Scheme for Sensorless Vector Control of Linear Induction Motor Drives

In power electronics and power systems, the dual-phase-locked loop (DPLL) is a well-accepted approach to maintain zero steady-state errors when subjecting to a frequency ramp input. This distinctive characteristic of the DPLL may make it as a promising candidate for speed estimation in speed-sensorless drive systems. Considering this issue, a DPLL-based speed estimation scheme for linear induction motor speed-sensorless drive systems is presented in this article to achieve accurate speed estimation. The basics of the DPLL and the direct application of the DPLL scheme are provided. However, in practice, the direct application of the DPLL scheme may degrade the performance of the entire system, which includes the nonidealities in the secondary electromotive force (EMF) signals, such as harmonics and parameter variations. Accordingly, the prefilter and the amplitude normalization scheme are employed to mitigate the effect of nonidealities. Meanwhile, the small-signal model of the proposed DPLL scheme is presented, enabling the analysis of the dynamic performance and the comparison of the synchronous reference frame phase locked-loop scheme. In addition, a parameter tuning guideline of the proposed DPLL scheme is detailed by using the derived small signal model. The performance of the proposed DPLL scheme is investigated by experimental tests.

Deadbeat Predictive Current Control for Permanent Magnet Synchronous Machines With Closed-Form Error Compensation

Deadbeat predictive current regulator features fast dynamic responses. However, it suffers from the steady-state current tracking error in a practical system due to the plant uncertainties, particularly the inductances. Instead of using observer-based disturbance voltage feedforward methods, this article proposes a new closed-form method to directly compensate the current tracking errors with a simple feedforward term added to the voltage commands. Zero steady-state error is achieved with negligible computation compared to the observer-based methods. The new method is first derived to tackle the inductance mismatch in the surface-mount permanent magnet synchronous motor, then the system close-loop transfer function is established to prove that the proposed method guarantees the zero steady-state error even with mismatches of the stator resistance and rotor flux linkage. Furthermore, based on the proposed compensation method, noise suppression schemes are added and designed to reduce high-frequency noise sensitivities in practical systems. Finally, the proposed method is extended to the interior permanent magnet synchronous motor (IPMSM). IPMSM system simulation and 68.5-kW experimental results are provided to validate the proposed method.

Control Strategy of Single-Phase Hybrid-Mode Ćuk Inverter for LVRT Capability

This article proposes a control strategy for a Cuk module-integrated inverter (MII) with hybrid operation mode for low-voltage ride-through (LVRT) capability. The hybrid-mode Cuk MII operates in unfolding-type power conversion (UPC) mode during normal grid conditions and in two-stage power conversion (TPC) mode during grid faults. It also has the advantages of highly efficient power transfer and LVRT capability but is difficult to control because UPC and TPC modes have distinct system dynamics and suffer from grid voltage disturbances that have different magnitudes. To overcome this control problem, this article proposes a control strategy that corresponds to the operating mode of the hybrid-mode Cuk inverter. To achieve zero steady-state tracking error during the grid disturbance, a repetitive controller (RC) is used in the proposed control scheme. Different phase-lead compensators in the RC compensate for different phase lags caused by distinct system dynamics. To reduce the burden from the RC, different nominal duty ratios are used as the feedforward control input. To minimize the tracking error during grid faults, a proportional-resonant controller is used in parallel with the RC controller in the TPC mode. To analyze the stability of different control systems, a unified control system model is presented for the proposed inverter. The procedure to select control parameters is also presented in detail. Simulation results validate the proposed control scheme in the hybrid-mode Cuk inverter, and experiments are conducted using the 400-VA MII prototype to demonstrate its validity.

Grid current low‐order harmonics suppression of the three‐phase grid converter with an LCL filter under the distorted grid voltage

This article presents an extended backstepping control method to reduce the grid-side current harmonics caused by grid voltage distortion. A dynamic model considering the grid voltage as an external disturbance is derived in the stationary reference frame. The extended back-stepping design procedure based on pole displacement guarantees that the system is stable without damping. The proposed method has a general low-order harmonics suppression instead of selective harmonics elimination. Zero steady-state error can be obtained tracking the grid currents. Stability, as well as good transient and steady-state performance are verified through numerical simulation. A comparison with the state-of-the-art proportional resonant control with active damping is also conducted. The results show that a good low-order harmonics reduction in the grid current is achieved by the proposed control method.