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1.
To achieve the frequency restoration (FR) and accurate reactive power sharing (RPS) in islanded microgrids (MGs), an improved P-f droop control is proposed. Firstly, the inverter impedance, whose value is set by the virtual impedance method, is used to minimize the impact of line resistance on powers coupling and RPS. Then, in order to restore the frequency of distributed generations (DGs) to the rated value, the reference is changed for compensating the frequency deviation (FD) caused by loads change. And the fast FR rate is achieved under a large constant k. Besides, in order to eliminate the inaccuracy of RPS caused by voltages difference (VD), the line voltage drop (LVD) is used to compensate the voltage droop characteristics. The use of voltage feedback ensures that the obtained voltage is desired after the LVD compensation. Finally, the simulation in RT-LAB indicates the effectiveness of proposed method in an islanded MG model.  相似文献   

2.
This paper presents the design of a hysteresis band controller to regulate the switching frequency in a sliding mode controlled nonlinear Boost power converter. The proposed architecture relies on a piecewise linear modeling of the switching function behavior within the hysteresis band, and consists of a continuous-time integral-type controller that modifies the amplitude of the hysteresis band of the comparator in accordance with the error between the desired and the actually measured switching period. The study provides the dynamical models of the converter operating in sliding mode and the switching frequency control loop. Moreover, the design of the parameters of both the sliding mode control and the switching frequency controller guarantee the fulfilment of the desired output voltage regulation of the Boost converter and the steady state setting of the switching frequency with a known, taylored dynamics. A Boost power converter prototype has been built to validate the proposal. Experimental results confirm the predicted good performance of the controllers, as well as the robustness with respect to changes in the switching frequency reference and the system parameters.  相似文献   

3.
In the islanded microgrid (MG), to improve the control effect of the output voltages of DERs and keep the economical operation of MG, a consensus-based economic hierarchical control strategy is proposed in this paper. The corresponding control structure is divided into physical and cyber layers, where the cyber layer is mainly composed by communicators. In these two layers, there are two main designs: the consensus-based primary control (CBPC) method and the secondary control (CBSC) method. In CBPC: Firstly, the undirected communication path among communicators is designed by path planning. Then, based on the constructed path, an economic P–U droop control method considering with line loss and flexible load is realized by using consensus control. In CBSC: Firstly, a cyber-physical vulnerability assessment method is designed. Based on this method, the DER with the lowest vulnerability is selected to be connected with the “virtual leader”. And when the data transmission behavior of the undirected communication path is selected, the undirected network can be transferred as a directed network. Thus, it can make the virtual leader-following consensus control (VLFCC) and the secondary control on voltage accomplished. Finally, the simulation results show the effectiveness of the proposed strategy.  相似文献   

4.
This paper proposes a unified method to design an optimized type of the hysteresis modulation-based sliding mode current controller for non-minimum phase power converters in continuous conduction mode. The traditional sliding mode controlled converters have a slow transient voltage response at heavy loads, a large overshoot at light loads and during abrupt output resistance variations. To solve these problems, an optimized feedback control scheme is used according to the output resistance to adjust the coefficients of the controller. The basic idea of this controller is to suggest a new way for reduction of the sensitivity function amplitude of the closed loop system. The presented approach is developed for three basic DC/DC converters; i.e. boost, buck-boost and quadratic boost converters. Generally, the certain advantages of the suggested control approach are: (i) a fast transient response can be achieved in heavy load conditions, (ii) the voltage overshoot can be effectively reduced during load variations; (iii) the transient voltage overshoot can be eliminated in light load conditions; (iv) the closed loop control sensitivity can be reduced and therefore, the performance specification of a control system can be improved compared with the conventional sliding mode current control. To show the reliability of the suggested control scheme, simulations and experimental results for the derived systems are developed. Several conditions are performed to confirm the effectiveness of the proposed controller.  相似文献   

5.
In this paper, Denial-of-Service (DoS) attacks on a microgrid (MG), especially on service-provider-edge routers in the MG, are considered and analysed. To increase the tolerance of the MG for DoS attacks with decreased computing time, we present consensus-based secondary frequency controllers with dynamic P-f droop controllers. Then, with the consideration of the impact on these controllers caused by DoS attacks, a state-space model of the MG is established based on which the stability analysis is derived. Finally, the effectiveness of the method is verified by simulation and experimental results.  相似文献   

6.
The power sharing of AC/DC micro-grids is researched in this paper. The proposed strategy mainly include two parts: the primary power event triggering control with secondary control and an adaptive quasi sliding mode voltage control in inner-loop. Firstly, a event triggering power sharing control (ETPSC) based on P?F droop curve is developed to regulate the voltage and frequency of AC and voltage of DC with the aim of the proportional power sharing between AC and DC micro-grids. The triggered threshold of ETPSC can be chosen to decide the transmitted power between AC and DC micro-grids. When the difference power between AC and DC micro-grids is less than the triggered threshold of power flow, there is no power sharing between AC and DC micro-grids, which can less the number of switching the power flow direction and the transmitted line power loss. The ETPSC has a great robust for the disturbances of load and improve the stability of the system. An adaptive quasi-sliding-mode control,which is implemented easily and flexibly with small computational burden and only based on input/output (I/O) measurement data but not the model any more, is used to control voltage in inner-loop. The effectiveness of the proposed control schemes is demonstrated by some numerical simulations and experimental results.  相似文献   

7.
A microgrid (MG) is a building block of future smart grid, it can be defined as a network of low voltage power generating units, storage devices and loads. System of systems (SoS) is another concept involving large scale integration of various systems. In this paper, we provide an overview of recent developments in modeling and control methods of microgrid as well as presenting the reason towards incorporating MG into the existing grid. Various SoS control strategies when applied to MG are discussed.  相似文献   

8.
Load voltage waveforms corresponding to symmetrical phase-angle triggering and integral-cycle triggering in single-phase thyristor circuits, and also the waveform due to half-wave rectification, are all discrete forms of amplitude modulation. In each case the modulated output voltage is obtained from a sinusoidal (supply) carrier signal by use of a rectangular modulating function, dependent on thyristor switching.The use of amplitude modulation (AM) techniques for frequency conversion in high power applications is subject to certain severe restrictions of performance. These restrictions can be largely overcome by the use of phase modulation (PM) methods which involve two channels of AM in each electrical supply line.Appropriate waveforms may be realised by the use of controlled switching of thyristors. These are arranged in combinations of inverse-parallel connected pairs forming subtractor modulators. Certain thyristor commutation problems arise in PM systems at high power levels. These problems can be overcome by producing so-called AM/PM waveforms that combine the separate advantages of AM and PM systems.  相似文献   

9.
This paper deals with the distributed secondary control problem for multiple distributed generators in an islanded microgrid. A distributed fixed-time secondary controller is designed for each generator using only its neighbors’ information, where saturation functions are introduced to the designed controllers to constrain the adverse influence of abnormal data from neighbors. Several indicator variables are introduced to reformulate the saturation function to reduce conservatism. The objective of this paper is to realize the recovery of the frequency and voltage as well as the active power-sharing within a fixed time. The fixed-time convergence of the proposed distributed control algorithm is analyzed through rigorous analysis. Also, the upper bound of the settling time is derived, which does not depend on the system’s initial state. Finally, a simulation example is utilized to verify the effectiveness of the proposed distributed control scheme by using the MATLAB/SimPowerSystems toolbox.  相似文献   

10.
In this paper, the adaptive sliding mode control issue for switched nonlinear systems with matched and mismatched uncertainties is addressed, where the persistent dwell-time switching rule is introduced to describe the switching of parameters. Besides, considering the case that the upper bound of the matched uncertainty is unknown, the purpose of this paper is to utilize an adaptive control method to estimate its upper bound parameters. To begin with, a linear sliding surface is constructed, and then the reduced-order sliding mode dynamics can be obtained through a reduced-order method. Next, sufficient conditions can be derived based on the Lyapunov stability and the persistent dwell-time switching analysis techniques ensuring that the reduced-order sliding mode dynamics is globally uniformly exponentially stable. Moreover, a switched adaptive sliding mode control law is designed, which can not only ensure the reachability of the sliding surface but also estimate the upper bound parameters of the matched uncertainty. Finally, a numerical example and a circuit model are introduced to verify the effectiveness of the proposed method.  相似文献   

11.
This paper deals with the sliding mode control problem for semi-Markovian jump systems with state saturation, in which the controller may not be synchronized with the considered systems. A mode-detector is introduced to estimate the unavailable system mode, based on which an asynchronous sliding mode controller is designed. Then, both the μ-exponential mean-square stability and the reachability of sliding surface are analyzed. Furthermore, a solving algorithm is given to acquire the feasible controller gains. Finally, the proposed asynchronous sliding mode control approach under state-saturation is illustrated via simulation results.  相似文献   

12.
In this paper, a robust fault tolerant control, which provides a global fixed-time stability, is proposed for robot manipulators. This approach is constructed based on an integration between a fixed-time second-order sliding mode observer (FxTSOSMO) and a fixed-time sliding mode control (FxTSMC) design strategy. First, the FxTSOSMO is developed to estimate the lumped disturbance with a fixed-time convergence. Then, based on the obtained disturbance estimation, the FxTSMC is developed based on a fixed-time sliding surface and a fixed-time reaching strategy to form a global fixed-time convergence of the system. The proposed approach is then applied for fault tolerant control of a PUMA560 robot and compared with other state-of-the-art controllers. The simulation results verify the outstanding fault estimation and fault accommodation capability of the proposed fault diagnosis observer and fault tolerant strategy, respectively.  相似文献   

13.
In this paper, an asynchronous sliding mode control design method based on the event-triggered strategy is proposed for the continuous stirred tank reactor (CSTR) under external disturbance. Firstly, with the purpose of appropriately modeling the multi-mode switching phenomenon in the CSTR caused by the fluctuation of temperature and concentration, the Markov process is applied. Secondly, the asynchronous switching characteristics are introduced to describe mismatch between the controller and the system, which caused by some factors such as signal transmission delay and packet dropout. In order to effectively estimate the system states that cannot be measured in real time, an observer based on the event-triggered strategy is proposed, which also can reduce the computational cost. In addition, a sliding mode controller is designed to ensure the dynamic stability and the sliding dynamics is reachable in a finite time. Finally, the effectiveness of the proposed method is verified by simulation experiments.  相似文献   

14.
Finite time convergence based on robust synergetic control (SC) theory and terminal attractor techniques is investigated. To this end a fast terminal synergetic control law (FTSC) is applied to drive a DC–DC Buck converter via simulation and through a dSpace based experimental setup to validate the approach. As robust as sliding mode control, the synergetic approach used is chattering free and provides rapid convergence. Efficacy of the proposed fast terminal synergetic controller is tested for step load change and output voltage variation and results compared to classical synergetic and PI control. Experimental validation using dSpace DS1104 confirms the results obtained in simulation showing the soundness of this approach compared to synergetic and PI controllers.  相似文献   

15.
This paper deals with the load frequency control problem of multi-area power system with doubly-fed-induction-generator-based wind farm. An area-based event-triggered (ET) sliding mode control scheme is proposed to restore the nominal frequency by transmitting less information. The main feature of area-based ET scheme is that each area will transmit its states information to the controller independently via its own triggering mechanism. By flexibly selecting triggering thresholds, the area-based ET scheme can meet the unbalanced network resources among different areas. Meanwhile, the designed sliding mode controller can effectively suppress the fast fluctuation resulting from load and wind generation to achieve frequency restoration and maintain the tie-line power at its scheduled value. The optimization algorithm on the sufficient conditions is given. Finally, the proposed control scheme is illustrated via a three-area power system and IEEE 39-bus system.  相似文献   

16.
Conventional direct torque control (DTC) suffers from large torque ripple and nonconstant switching frequency, which are caused by the hysteresis band amplitude and the motor speed. Many methods have been proposed to tackle these problems. However, these methods are usually complicated and parameter dependent. A novel DTC method for brushless DC motors based on duty ratio control is proposed to reduce torque ripple and maintain a constant switching frequency. During each switching period, an active voltage vector and a zero voltage vector are applied. A simple and effective method implemented to calculate the duty ratio relies only on the torque error, reducing the parameter dependence. The proposed method has the advantages of conventional DTC and effectively reduces torque ripple, which improves the performance of conventional DTC. Simulation and experimental results are given to confirm the method’s validity.  相似文献   

17.
This paper investigates the frequency change problem of hydraulic turbine regulating system based on terminal sliding mode control method. By introducing a novel terminal sliding mode surface, a global fast terminal sliding mode controller is designed for the closed loop. This controller eliminates the slow convergence problem which arises in the terminal sliding mode control when the error signal is not near the equilibrium. Meanwhile, following consideration of the error caused by the actuator dead zone, an adaptive RBF estimator based on sliding mode surface is proposed. Through the dead zone error estimation for feed-forward compensation, the composite terminal sliding mode controller has been verified to possess an excellent performance without sacrificing disturbance rejection robustness and stability. Simulations have been carried out to validate the superiority of our proposed methods in comparison with other two other kinds of sliding mode control methods and the commonly used PID and FOPID controller. It is shown that the simulation results are in good agreement with the theoretical analysis.  相似文献   

18.
To achieve accurate position control of electro-hydraulic asymmetric cylinder system with only available displacement signal, an output feedback controller is proposed in this paper. The dynamic model of the system is expressed as a Brunovsky form, which helps to estimate the system states and simplify the controller structure. Then Levant differentiator is introduced to estimate the position, velocity and acceleration of the asymmetric cylinder system based on the output signal, which can reduce the impact of measurement noise compared to the means of calculating the time derivative of the displacement signal directly. Besides, a high gain disturbance observer is designed to reject the lumped disturbance rejection of the system including parameter uncertainty, modelling error and external disturbance. Moreover, a sliding mode surface is introduced to the controller design and a robust item with continuous function is applied to compensate for estimation errors. According to Lyapunov theory, the developed output controller is pledged to be stable that can realize disturbance rejection control as well as backstepping-free control. Furthermore, a large-size asymmetric cylinder experimental rig is set up to simulate practical applications environment. Comparative experimental results reveal the validity and potential practical meaning of the developed control approach.  相似文献   

19.
The recent transition in power generation and consumption is based on the integration of renewable energy sources using DC microgrids. To facilitate this integration, a multi-source DC microgrid structure with wind, photovoltaics, fuel cell and hybrid energy storage system including battery and supercapacitor is presented in this paper. These sources are linked to a DC-bus via DC-DC converters. A hierarchical control strategy with a device and a system-level control for coordinated control between energy sources and their storage devices is proposed. In the device-level control, a variable structure based sliding mode control is applied to regulate the DC bus voltage and to ensure global asymptotic stability. Whereas, the system-level control compensates for the supply and demand mismatches by using a rule-based fuzzy system. To verify the effectiveness of the proposed scheme and the superiority of one controller over another, the proposed controllers are simulated and compared in the MATLAB/Simulink environment under varying load and weather data conditions. Results show that super twisting sliding mode control had negligible chattering as well as better convergence as compared to controllers. Furthermore, the efficiency of the developed scheme is validated by controller hardware in loop experiments.  相似文献   

20.
黄金海  郭庆  王卫俊 《大众科技》2012,(12):89-90,175
升频升压驱动方式已广泛应用在混合式步进电机驱动器中,文章介绍了以频压转换芯片LM2097、脉宽控制芯片TL494、调压电路组成的升频升压控制方式,其输出的直流母线电压接步进电机各相的MOSFET功率驱动电路。在驱动器中过压过流保护电路也是必须设计的。  相似文献   

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