Fast Dynamic Performance Research Articles

An innovative optimal RPO-FOSMC based on multi-objective grasshopper optimization algorithm for DFIG-based wind turbine to augment MPPT and FRT capabilities

Abstract Doubly Fed Induction Generator (DFIG) with consideration of its exceptional capabilities, i.e.: variable speed operation, low mechanical stresses, and excellent power quality in limited-range speed applications is a famous kind of wind turbines. Even so, there is a challenge due to its nonlinear dynamic features and several uncertainties like unknown non-linear disturbances and parameter uncertainties. Hence, this paper proposes a novel Robust Perturbation Observer based Fractional Order Sliding Mode Controller (RPO-FOSMC) for DFIG to extract the maximum power and improve the Fault Ride-Through (FRT) capability. The strong nonlinear aerodynamics of wind turbine, the uncertain dynamic parameters of induction generator and the stochastic characteristics of wind waves are constructed in perturbation term which is estimated using the proposed RPO-FOSMC. Accordingly, the perturbation compensator provides an appropriate robustness concerning different uncertain models and attains an exceptional control capability during stochastic wind waves. Considering the inherent multi-objective nature of the nonlinear control design problem, Multi-Objective Grasshopper Optimization Algorithm (MOGOA) has been implemented to augment the robustness and dynamic performance of RPO-FOSMC. Three distinct conditions are considered to compare and analyse the fast and robust dynamic performance of optimal RPO-FOSMC against other conventional approaches. Eventually, the comprehensive simulation results have revealed and validated the exceptional dynamic capability of the suggested control strategy.

A Hybrid Passivity-Based Control Strategy for Three-Level T-Type Inverter in LVRT Operation

The fast dynamic performance of a photovoltaic (PV) inverter is one of the most important issues in low-voltage ride-through (LVRT) operation, as the voltage dip period is short. Nevertheless, it is difficult to control the output currents with conventional methods, especially during transients or under low-power factor operation. In order to satisfy the LVRT requirements and improve the performances of a three-level T-type inverter (3LT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> I) in a PV system, the hybrid passivity-based control (HPBC) strategy with the fast transient response and strong robustness to system parameter changes and external disturbances is proposed in this paper. First, the Euler- Lagrange model of the 3LT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> I under the LVRT condition is derived and analyzed. Then, the 3LT <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> I system is theoretically proved to be strictly passive by using some ingenious arithmetic and differential calculation techniques. Furthermore, based on the error energy function and the Lyapunov stability criterion, a passivity-based controller including a negative sequence of grid voltage feedforward control terms is designed to suppress the negative-sequence currents effectively. The balanced grid currents are obtained, which improve the stability of the system in LVRT operation. Compared with the conventional methods, the proposed HPBC scheme has the superior characteristics of fast and non-overshoot response in a transient state and accurate current tracking performance in a steady state. The theoretical analysis and effectiveness of the proposed strategy have been validated by means of both simulations and experiments.

Steady-State Error Suppression and Simplified Implementation of Direct Source Current Control for Matrix Converter With Model Predictive Control

A matrix converter (MC) with model predictive control based on the source reactive power control usually fails to show sinusoidal source currents. The analysis presented in this paper shows that this common combination of a converter and control has the inherent inability to suppress some harmonics in the source currents, even with additional passive or active damping control. Direct source current control can be implemented to give sinusoidal source currents and intrinsic active damping. However, the issue of steady-state error in output currents then arises, as the MC topology does not allow of the independent control of source and output currents. Therefore, feedback control of load active power is proposed to address this issue without degrading the fast dynamic performance. Benefiting from the direct source current control, a simplified implementation is also proposed to decrease the number of candidate switching states from 27 to 5, which significantly reduces the computational burden. Experimental results have verified the theoretical analysis and the effectiveness of the proposed control scheme.

Modelling and analysis of an analogue MPPT‐based PV battery charging system utilising dc–dc boost converter

Nowadays, the research is being devoted to the development of rapid and precise maximum power point tracking (MPPT) for various photovoltaic (PV) applications. However, the constraints imposed by size, cost, efficiency, and tracking performances essentially limit the application of conventional MPPT techniques and their analysis methodologies. This study recommends a fast and robust analogue PV MPPT for the battery charging system using dc-dc boost converter. The fast dynamic performances with absolute robustness are ensured here by fast-scale stability analysis of actually switched boost converter using the concepts based on non-linear dynamics and bifurcation theory. Such concepts not only provide the information to design an efficient MPPT system under rapidly changing environmental conditions but also guarantee the system to operate either in period-1 or chaotic mode. The theoretical and mathematical analyses are experimentally verified using a prototype PV battery charging system utilising dc-dc boost converter. It is presented that operating the MPPT system in chaos not only yields the broader power spectrum with reduced spectral peaks at the multiples of converter's switching frequency but also exhibits high overall conversion efficiency.

Second‐order sequence filter based control algorithm for single‐phase grid interfaced solar PV system

This work deals with an implementation of a unique control approach for the power quality enhancement in solar photovoltaic (PV) based grid interfaced system. In this work, a robust control technique with strong filtering capabilities is implemented. A single-phase two-stage grid interacted solar PV topology is considered with a second-order sequence filter as a test system for the validation of the power quality enhancement features. The system constitutes a PV array, a boost converter, a DC link capacitance, a voltage source converter (VSC), an interfacing inductor and a ripple filter. A boost converter is used at a primary stage of proposed topology, which supports the extraction of maximum power from the solar PV array. In addition, the VSC feeds the solar PV power into the grid. It also provides harmonics elimination and power factor correction. A new maximum power point tracking technique avoiding a drift feature is adopted for the fast dynamic performance. The implementation of the solar PV system is performed and the harmonic profile of grid current is observed in compliance to the IEEE-519 standard.

Research on predictive current control method of PMSM for continuous switched boost inverter

In this paper, the continuous switched boost inverter (CSBI) is used to improve permanent magnet synchronous motor (PMSM) control performance through predictive control, aiming at the drawback of the traditional PMSM drive system. Between the inverted circuit and the input DC power, a switched boost circuit is added to form a switched boost inverter circuit to achieve higher voltage gain and eliminate the dead band. Meanwhile, the drive system has higher reliability. Moreover, the paper adopts predictive current control (PCC) to control PMSM, comparing with the traditional field oriented control (FOC), PCC has faster dynamic performance and reduces current ripple. Finally, the simulation and experimental results verify the feasibility of the based on the continuous switched boost inverter of predictive current control for PMSM.

An Active Vehicle Suspension Control Approach with Electromagnetic and Hydraulic Actuators

An active vibration control approach from an online estimation perspective of unavailable feedback signals for a quarter-vehicle suspension system is introduced. The application of a new signal differentiation technique for the online estimation of disturbance trajectories due to irregular road surfaces and velocity state variables is described. It is assumed that position measurements are only available for active disturbance suppression control implementation. Real-time signal differentiation is independent of detailed mathematical models of specific dynamic systems and control force generation mechanisms. Active control forces can be supplied by electromagnetic or hydraulic actuators. Analytical and simulation results prove the effective and fast dynamic performance of the online signal estimation as well as a satisfactory active disturbance attenuation on a quarter-vehicle active suspension system.

A Simple Current-Constrained Controller for Permanent-Magnet Synchronous Motor

Under the noncascade structure, a permanent-magnet synchronous motor (PMSM) regulates the speed and current in one loop. On the one hand, fast dynamic performance requires large transient current to provide a high torque. On the other hand, unlike a cascade control, the q -axis current is no longer governed by a reference current signal. In such a system, the nominal controllers cannot guarantee that the q -axis current is within the required range. But an excessively large transient current may threaten the circuit safety. To solve the overcurrent protection problem, the ordinary solution is to choose conservative control parameters, but the dynamic performance inevitably suffers a certain degree of loss. In order to improve this drawback, a simple and effective control scheme is introduced with a current-constrained technique. By constructing a special nonlinear gain, the punishment mechanism for the q -axis current is established in the control action directly. The proposed control approach does not impose limitations on the initial state. Moreover, it has good robustness to load torque uncertainty and undergoes rigorous theoretical analysis. Besides, the proposed current-constrained controller has a very concise structure. It yields a higher reliability of the PMSM control system. Comparative simulation and experimental results between the classic PID and the current-constrained controller on the PMSM servo system verify the feasibility of the presented control scheme.

Accurate and Fast Harmonic Detection Based on the Generalized Trigonometric Function Delayed Signal Cancellation

The abundant grid-connected power electronic devices and non-linear loads used widely have caused power system harmonic pollution. Harmonic detection is very important for selective harmonic compensation used to improve the power quality. To detect the individual harmonic component accurately and fast, a harmonic extraction based on generalized trigonometric function delayed signal cancellation (GTFDSC) is proposed to extract the fundamental component or the desired harmonic component. The proposed GTFDSC can be used to accurately extract the desired harmonic component under various harmonic scenarios because of its excellent filtering capability. What’s more, the parameters of the GTFDSC can be flexibly designed according to the distribution of the harmonic series of the input signal, thereby reducing the delay time and the number of operators. Furthermore, the GTFDSC is self-adjustable to fundamental frequency deviations by introducing the frequency feedback loop, and it is able to achieve excellent filtering capability and fast dynamic performances. Lastly, the experimental results are provided to verify the effectiveness of the proposed method.

Dahlin-Based Fast and Robust Current Control of a PMSM in Case of Low Carrier Ratio

The low ratio of sampling frequency to electrical frequency (carrier ratio) is a challenging issue for applications, such as high-speed or high-power drives. In fact, high-speed drives have high fundamental frequency and high-power drives have low switching (sampling) frequency, leading to the same control challenges of having high dynamic and stability with a limited number of control actions in one period. Parameters mismatch occurs due to the converter non-linearities, deadtimes, temperature change, and saturation; hence, providing robust control is a key challenge. This paper starts reviewing the problems of controlling machines with a few switching instances per fundamental period and an analysis of the state-of-the-art current control strategies for permanent magnet synchronous motors (PMSMs). Three different control schemes are analyzed. The discrete-time PI current controller is providing good robustness, while the dynamic performance may not be sufficient for some applications. Second, the deadbeat control offers very fast dynamic performance but is weak under parameter mismatch. The novel application of the Dahlin controller offers a tradeoff between performance and stability. The control algorithms are evaluated based on the stability, robustness, and dynamic and steady-state performances. Their performance and sensitivity to parameter variation are analyzed through simulations, and the experimental measurements are proving the results.

Designed Dynamic Reference With Model Predictive Control for Bidirectional EV Chargers

This paper presents a finite control set model predictive control (MPC) using a designed dynamic reference for bidirectional electric vehicle (EV) chargers. In the conventional MPC scheme, a PI controller is involved to generate an active power reference from the DC voltage reference. It is hard to find one fixed set of coefficients for all working conditions. In this paper, a designed dynamic reference based MPC strategy is proposed to replace the PI control loop. In the proposed method, a DC voltage dynamic reference is developed to formulate the inherent relationship between the DC voltage reference and the active power reference. Multi-objective control can be achieved in the proposed scheme, including controlling of the DC voltage, battery charging/discharging current, active power and reactive power, independently. Bidirectional power flow is operated effectively between the EV- and the grid-side. Experimental results are obtained from a laboratory three-phase two-stage bidirectional EV charger controlled by dSPACE DS1104. The results show that fast dynamic and good steady state performance of tracking the above objectives can be achieved with the proposed method. Compared with the system performance obtained by the conventional MPC method, the proposed method generates less active power ripples and produces a better grid current performance.

Direct Power Control of Pulsewidth Modulated Rectifiers Without DC Voltage Oscillations Under Unbalanced Grid Conditions

Direct power control with space vector modulation (DPC-SVM) features simple structure, fast dynamic performance, and little tuning work. However, the conventional DPC-SVM cannot achieve accurate power control under unbalanced grid conditions. A modified DPC-SVM is thus proposed for accurate power control under both ideal and unbalanced grid conditions. Though the power control accuracy is improved when compared with the conventional DPC-SVM, it still suffers highly distorted grid current and dc voltage oscillations with an unbalanced network. Therefore, a power compensation method is subsequently derived aiming at the following targets: eliminating dc voltage oscillations, achieving sinusoidal grid current, and obtaining unity power factor. To that end, average grid-side reactive power and oscillations in converter-side active power are controlled as zero by simply adding a compensation to original power reference. Additionally, the proposed method does not require extraction of a positive sequence or negative sequence component of grid voltage. Compared with the conventional DPC-SVM in an ideal grid, only additional compensation of power reference is required. As a result, control performance can be significantly improved without substantial increase in complexity. The superiority of the proposed method over the prior DPC-SVM is validated by both simulation and experimental results obtained on a two-level pulsewidth modulation voltage source rectifier.

Dynamic performance improvement of single‐phase PWM converters with power hysteresis control scheme

This study presents a direct power control (DPC) scheme with pulse width modulation module and two hysteresis comparators, for the application in single-phase PWM converters to overcome the drawbacks of conventional proportion-integration-based DPC (PI-based DPC), including poor dynamic performance and complexity of tuning PI parameters. According to the outputs of inner-loop power hysteresis controllers, the proposed DPC scheme divides d-q reference frame into four sectors. In each sector, the dynamic power components are estimated to be equivalent as the outputs of PI controllers in PI-based DPC. The proposed DPC scheme provides a new solution of non-linear hysteresis control to achieve fast dynamic performance with constant switching frequency. Additionally, due to inductance parameter mismatch, the effect on powers is analysed in detail, and an inductance parameter on-line estimation method is present and discussed. A comprehensive comparison of conventional table-based DPC, PI-based DPC and the proposed DPC methods has been conducted in this study, including steady-state performance with respect to different factors, and dynamic response under different extreme conditions. The experimental results have verified the effectiveness of the proposed DPC scheme.

Optimized Design of Space Solar Array Simulator With Novel Three-Port Linear Power Composite Transistor Based on Multiple Cascaded SiC-JFETs

Space solar array simulators (SSASs), which are used for testing space power systems, generally utilize linear power topologies owing to their fast dynamic performance and satisfactory simulation accuracy. However, to output a medium power level from a linear-power-topology SSAS, multiple parallel linear voltage-controlled current sources are required for addressing the redundant power dissipation, thereby limiting the overall mechanical structure and volume optimization; in addition, the presence of multiple parallel sources results in a complex circuit structure with poor reliability. In this context, in this study, we propose a novel three-port linear power composite transistor as a linear power dissipation device, which is composed of multiple cascaded SiC-JFETs to improve on the above-mentioned shortcomings. The proposed 510-W optimized SSAS requires only eight parallel linear current-source paths to form a linear power stage and uses a high-speed field-programmable gate array (FPGA) digital controller to quickly react to a load step between short circuit and open circuit (the harshest working condition for a solar array simulator) at a 1-kHz stepping frequency. Further, the device can react to a load step between short circuit and the nominal working point at 10-kHz stepping frequency, thus, offering a better dynamic performance over other similar devices.

Predictive control of plug-in electric vehicle chargers with photovoltaic integration

This paper presents a model predictive control (MPC) for off-board plug-in electric vehicle (PEV) chargers with photovoltaic (PV) integration using two-level four-leg inverter topology. The PEV charger is controlled by a unified controller that incorporates direct power and current MPC to dynamically control decoupled active-reactive power flow in a smart grid environment as well as to control PEV battery charging and discharging reliably. PV power generation with maximum power tracking is seamlessly integrated with the power flow control to provide additional power generation. Fast dynamic response and good steady-state performance under all power flow modes and various environmental conditions are evaluated and analyzed. From the results obtained, the charger demonstrates less than 1.5% total harmonic distortion as well as low active and reactive power ripple of less than 7% and 8% respectively on the grid for all power flow modes. The PEV battery also experiences a low charging and discharging current ripple of less than 2.5%. Therefore, the results indicate the successful implementation of the proposed charger and its control for PV integrated off-board PEV chargers.

Field‐oriented control based on hysteresis band current controller for a permanent magnet synchronous motor driven by a direct matrix converter

The hysteresis band controller offers excellent dynamic performance. It has been widely researched and applied to the voltage source inverter and inverter fed drives, however it has not been investigated within the context of a matrix converter or a matrix converter based motor drive. In this study, both fixed-band and sinusoidal-band hysteresis current controllers are proposed and developed for a direct matrix converter. A comprehensive comparative evaluation of the two methods is then carried out. Both methods have fast dynamic performance and they inherently integrate the line modulation technique of the virtual rectifier stage into the overall modulation. Surge currents are prevented with the proposed scheme. The sinusoidal-band hysteresis controller demonstrates lower total harmonic distortion at the expense of higher average switching frequency, which is only significantly observable at very high sampling frequencies. The proposed controller is integrated with the field-oriented control to drive a matrix converter fed permanent magnet synchronous machine. The proposed methods are simple and incur a light computational burden, which advances the practical applications of matrix converters in AC motor drives. The simulation and experiment results demonstrate the effectiveness and feasibility of the proposed scheme.

A Constant Switching Frequency Finite-Control-Set Predictive Current Control Scheme of a Five-Phase Inverter With Duty-Ratio Optimization

As is well known, the additional low-order harmonic currents and the huge computation amount of the cost function value with all available control sets are the two special issues of finite-control-set model predictive current control (FCS-MPCC) for multiphase inverters. Thus, this paper proposes a FCS-MPCC scheme with duty-ratio optimization for five-phase inverters. First, a group of the reconstructed virtual voltage vectors (V3) with low-order harmonic elimination is defined and employed as the control sets in FCS-MPCC scheme. Thus, it leads to no requirement for harmonic items and weighting factors existing in the cost function. Then, a combination of zero vectors and the selected V3 during each control horizon is adopted to rearrange the pulse sequence, which can realize constant switching frequency. In addition, the durations of the selected V3 and zero vectors during each control horizon are also estimated to minimize the steady-state current ripples in different subspaces based on the cost function optimization. Finally, a comparison of the proposed V3-FCS-MPCC scheme and the other FCS-MPCCs are presented in simulation and experimental test. Simulation and experimental results verify that the proposed V3-FCS-MPCC scheme can remain the simplified structure, fast dynamic performance, constant switching frequency, and achieve minimum current ripples in different subspaces.

A DC-Link Voltage Fast Control Strategy for High-Speed PMSM/G in Flywheel Energy Storage System

This paper presents a dc-link voltage fast control strategy for high-speed permanent magnet synchronous motor/generator of flywheel energy storage system (FESS) to ensure fast dynamic performance within its wide operation range. Instead of the conventional strategy with cascaded outer dc-link voltage loop and inner current loop, the proposed strategy is a direct voltage control strategy without an intermediate current loop. The nonlinear dc-link voltage loop model is globally linearized by treating the square of dc-link voltage as the state variable, and lumping the nonlinear and uncertain terms in the power balance equation as the total disturbance. An extended state observer (ESO) is designed to observe the total disturbance, and a control law that compensates the speed variation and the total disturbance is proposed. The inner dynamic of the proposed ESO is analyzed, and the tracking performance and antidisturbance capability of the proposed strategy is hereby derived. Finally, the proposed strategy is validated on a high-speed FESS test bench.

A novel dual closed-loop control scheme based on repetitive control for grid-connected inverters with an LCL filter

Grid-connected inverters with LCL filters need high steady-state control accuracy, fast dynamic response performance, and strong robustness to guarantee the power quality. However, there are many problems in traditional control strategies that restrict improvements to control system performance, such as poor dynamic performance of traditional single-repetitive control, large ripples, low steady-state accuracy of inverter current feedback based repetitive dual-loop control or grid-current feedback based single-loop proportional-integral control. In this paper, a novel dual closed-loop repetitive control strategy based on grid current feedback is proposed for single-phase grid-connected inverters with LCL filters. The proportional-integral inner loop is stabilized by using an inherent one-beat delay achieved by digital controller. Based on the inner loop system, a detailed design scheme of a repetitive controller is presented, through which direct control of the grid current is realized, the reference is tracked perfectly to a zero phase shift, and high-attenuation gain is achieved in the high frequency range. In particular, the gird-voltage feed forward control and current reference feedforward control are adopted to suppress grid-voltage disturbance and increase dynamic tracking performance. Finally, the simulation and experimental results show that the proposed method has the advantages of high steady-state accuracy, fast dynamic response, and anti-disturbance ability.

High Dynamic Performance Solar Array Simulator Based on a SiC MOSFET Linear Power Stage

The power conditioning unit system is a critical part in a spacecraft and is responsible for converting the solar panel energy into a stable bus voltage. This system requires a high dynamic characteristic solar array simulator (SAS) for testing purposes. Space solar array simulators (SSASs) used for testing space power systems generally use a linear power topology because of its fast dynamic performance and good simulation accuracy. However, commercially available SASs are not sufficiently fast for simulating the actual solar array panel output and, therefore are unreliable for terrestrial testing. In this paper, a highly dynamic SSAS is developed with multipath SiC MOSFET linear voltage-controlled current source paralleling for power regulation. The proposed 510 W SSAS, consisting of 20 linear current paths paralleling the power stage and a high-speed FPGA digital controller, can quickly react to a load step between the nominal and short circuit at 50-kHz stepping frequency. It can also react to a step change from a short circuit to an open circuit perfectly at a 1-kHz stepping frequency offering a superior dynamic performance compared to other similar devices.