scholarly journals Variable Structure Back-Stepping Control of Two-stage Three Phase Grid Connected PV Inverter

2020 ◽  
Author(s):  
Nasim Ullah ◽  
Ahmad Aziz Al Ahmadi
Keyword(s):  
Reactive Power ◽  
Control Method ◽  
Sliding Mode ◽  
Variable Structure ◽  
Control Approach ◽  
Control Loops ◽  
Pv Inverter ◽  
Voltage Variation ◽  
Three Phase ◽  
Back Stepping Control

This work presents a detailed analysis of a three phase grid tied photovoltaic inverter with variable structure back-stepping control approach. A nonlinear model of the system is derived and presented in rotational frame using the direct quadrature zero transformation (DQ). For the derivation of active and reactive power loops of the inverter, nonlinear back stepping approach is used. Moreover, sliding mode control method is used to derive the inner current loops while for the outer loop a virtual controller is derived using the Lyapunov function. The control loops are implemented in MATLAB/Simulink environment. To test the controller performance, active power variation, DC link voltage variation and reactive power variations are inflicted. The obtained results under the proposed control scheme are compared with boundary layer design based sliding mode controller. From the comparative analysis it is concluded that the proposed controller exhibit superior and robust performance under all test conditions.

Rotor Current Control of DFIG for Improving Fault Ride – Through Using a Novel Sliding Mode Control Approach

2013 ◽  
Vol 14 (6) ◽  
pp. 629-640 ◽  
Author(s):  
Guowei Cai ◽  
Cheng Liu ◽  
Deyou Yang
Keyword(s):  
Wind Power ◽  
Control Method ◽  
Sliding Mode ◽  
Rapid Development ◽  
Variable Structure ◽  
Current Control ◽  
Integral Control ◽  
Control Approach ◽  
Induction Generators ◽  
Fault Ride Through

Abstract The doubly fed induction generators (DFIG) have been recognized as the dominant technology used in wind power generation systems with the rapid development of wind power. However, continuous operation of DFIG may cause a serious wind turbine generators tripping accident, due to destructive over-current in the rotor winding which is caused by the power system fault or inefficient fault ride-through (FRT) strategy. A new rotor current control scheme in the rotor-side converter (RSC) ispresented to enhance FRT capacities of grid-connected DFIG. Due to the strongly nonlinear nature of DFIG and insensitive to DFIG parameter’s variations, a novel sliding mode controller was designed. The controller combines extended state observer (ESO) with sliding model variable structure control theory. The simulation is carried out to verify the effectiveness of the proposed control approach under various types of grid disturbances. It is shown that the proposed controller provides enhanced transient features than the classic proportional-integral control. The proposed control method can effectively reduce over-current in the RSC, and the transient pulse value of electromagnetic torque is too large under power grid fault.

scholarly journals Anti-Disturbance Finite-Time Adaptive Sliding Mode Backstepping Control for PV Inverter in Master–Slave-Organized Islanded Microgrid

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4490
Author(s):  
Chengshun Yang ◽  
Shuangfei Ni ◽  
Yuchen Dai ◽  
Xiaoning Huang ◽  
Dongdong Zhang
Keyword(s):  
Finite Time ◽  
Reactive Power ◽  
Control Method ◽  
Sliding Mode ◽  
Second Order ◽  
Convergence Time ◽  
Model Parameters ◽  
Adaptive Sliding Mode ◽  
Pv Inverter ◽  
Islanded Microgrid

With the aim to solve the problem related to the power chattering and anti-disturbance performance of a photovoltaic (PV) inverter in master–slave-organized islanded microgrid, an anti-disturbance finite-time adaptive sliding mode backstepping (DFA-SMB) controller is designed in this paper. First, the topology and the second-order dynamic model of PV inverter are established based on constant DC voltage and constant reactive power control method. Subsequently, the backstepping method is adopted to perform the control of a high-order system. Moreover, a second-order sliding mode differentiator is used to realize the function of command-filter, solving the differential expansion problem caused by the derivation of virtual controller. Besides, the terminal sliding mode control (TSMC) is introduced into the q-axis controller and d-axis inner loop controller, increasing the robustness and reducing the convergence time of the system. Adaptive control and disturbance-observer (DO) are used to perform the adaptive estimation of model parameters and the observation of lumped disturbances, respectively, enhancing the dynamic characteristics of the controller. Finally, a master–slave-organized islanded microgrid with 100 kW PV array is established in MATLAB/Simulink. The results demonstrate that the proposed control method can effectively reduce power chattering and improve the anti-disturbance ability of the PV system.

scholarly journals A Novel Adaptive Control Approach Based on Available Headroom of the VSC-HVDC for Enhancement of the AC Voltage Stability

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3222
Author(s):  
Duc Nguyen Huu
Keyword(s):  
Adaptive Control ◽  
Voltage Stability ◽  
Reactive Power ◽  
Control Method ◽  
Offshore Wind ◽  
Voltage Source ◽  
Long Distance ◽  
Control Approach ◽  
Hvdc System ◽  
Voltage Support

Increasing offshore wind farms are rapidly installed and planned. However, this will pose a bottle neck challenge for long-distance transmission as well as inherent variation of their generating power outputs to the existing AC grid. VSC-HVDC links could be an effective and flexible method for this issue. With the growing use of voltage source converter high-voltage direct current (VSC-HVDC) technology, the hybrid VSC-HVDC and AC system will be a next-generation transmission network. This paper analyzes the contribution of the multi VSC-HVDC system on the AC voltage stability of the hybrid system. A key contribution of this research is proposing a novel adaptive control approach of the VSC-HVDC as a so-called dynamic reactive power booster to enhance the voltage stability of the AC system. The core idea is that the novel control system is automatically providing a reactive current based on dynamic frequency of the AC system to maximal AC voltage support. Based on the analysis, an adaptive control method applied to the multi VSC-HVDC system is proposed to realize maximum capacity of VSC for reactive power according to the change of the system frequency during severe faults of the AC grid. A representative hybrid AC-DC network based on Germany is developed. Detailed modeling of the hybrid AC-DC network and its proposed control is derived in PSCAD software. PSCAD simulation results and analysis verify the effective performance of this novel adaptive control of VSC-HVDC for voltage support. Thanks to this control scheme, the hybrid AC-DC network can avoid circumstances that lead to voltage instability.

scholarly journals A new approach to three-phase asynchronous motor model for electric power system analysis

2021 ◽  
Vol 12 (4) ◽  
pp. 2083
Author(s):  
Laura Collazo Solar ◽  
Angel A. Costa Montiel ◽  
Miriam Vilaragut Llanes ◽  
Vladimir Sousa Santos
Keyword(s):  
Power Systems ◽  
Reactive Power ◽  
Mechanical Load ◽  
Asynchronous Motor ◽  
Electrical Power ◽  
Variable Load ◽  
Electrical Power Systems ◽  
Active And Reactive Power ◽  
Voltage Variation ◽  
Three Phase

In this paper, a new steady-state model of a three-phase asynchronous motor is proposed to be used in the studies of electrical power systems. The model allows for obtaining the response of the demand for active and reactive power as a function of voltage and frequency. The contribution of the model is the integration of the characteristics of the mechanical load that can drive motors, either constant or variable load. The model was evaluated on a 2500 kW and 6000 V motor, for the two types of mechanical load, in a wide range of voltage and frequency, as well as four load factors. As a result of the evaluation, it was possible to verify that, for the nominal frequency and voltage variation, the type of load does not influence the behavior of the powers and that the reactive power is very sensitive to the voltage variation. In the nominal voltage and frequency deviation scenario, it was found that the type of load influences the behavior of the active and reactive power, especially in the variable load. The results demonstrate the importance of considering the model proposed in the simulation software of electrical power systems.

scholarly journals Modeling and control of a hybrid DC/DC/AC converter to transfer power under different power management strategies

2021 ◽  
Vol 12 (3) ◽  
pp. 1620
Author(s):  
Amin Alizadeh Asl ◽  
Ramin Alizadeh Asl
Keyword(s):  
Reactive Power ◽  
Control Method ◽  
Proper Time ◽  
Management Strategies ◽  
Additional Advantage ◽  
Modeling And Control ◽  
Phase Inverter ◽  
Three Phase ◽  
Three Phase Inverter ◽  
Generation Power

<span>A hybrid DC/DC/AC converter connected to the grid without a three-phase transformer is controlled. The decentralized control method is applied to the hybrid DC-DC converter such that the maximum power of PV flows to the grid side. This controller must charge and discharge the battery at the proper time. It must also regulate DC-link voltage. An additional advantage of the proposed control is that the three-phase inverter does not need a separate controller such as PWM and SPWM. A simple technique is used for creating the desired phase shift in the three-phase inverter, which makes the active and reactive power of the inverter controllable. A new configuration is also proposed to transmit and manage the generation power of PV. In this<br />scheme, the battery and fuel cell are employed as an auxiliary source to manage the generation power of PV. Finally, a real-time simulation is performed to verify the effectiveness of the proposed controller and system by considering the real characteristics of PV and FC.</span>

scholarly journals Variable Structure Compensation PID Control of Asymmetrical Hydraulic Cylinder Trajectory Tracking

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Difei Liu ◽  
Zhiyong Tang ◽  
Zhongcai Pei
Keyword(s):  
Trajectory Tracking ◽  
Pid Control ◽  
Control Method ◽  
Sliding Mode ◽  
Variable Structure ◽  
Hydraulic Cylinder ◽  
Control Value ◽  
Equivalent Control ◽  
Asymmetrical Hydraulic Cylinder ◽  
The Stability

A novel variable structure compensation PID control, VSCPID in short, is proposed for trajectory tracking of asymmetrical hydraulic cylinder systems. This new control method improves the system robustness by adding a variable structure compensation term to the conventional PID control. The variable structure term is designed according to sliding mode control method and therefore could compensate the disturbance and uncertainty. Meanwhile, the proposed control method avoids the requirements for exact knowledge of the systems associated with equivalent control value in SMC that means the controller is simple and easy to design. The stability analysis of this approach is conducted with Lyapunov function, and the global stability condition applied to choose control parameters is provided. Simulation results show the VSCPID control can achieve good tracking performances and high robustness compared with the other control methods under the uncertainties and varying load conditions.

scholarly journals Sliding Mode Based Control of Dual Boost Inverter for Grid Connection

Energies ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 4241 ◽  
Author(s):  
Diana Lopez-Caiza ◽  
Freddy Flores-Bahamonde ◽  
Samir Kouro ◽  
Victor Santana ◽  
Nicolás Müller ◽  
...  
Keyword(s):  
Control Method ◽  
Controller Design ◽  
Sliding Mode ◽  
Current Control ◽  
Voltage Step ◽  
Control Loops ◽  
Voltage Ratio ◽  
Grid Connection ◽  
Resonant Controller ◽  
Laboratory Prototype

Single-stage voltage step-up inverters, such as the Dual Boost Inverter (DBI), have a large operating range imposed by the high step-up voltage ratio, which together with the converter of non-linearities, makes them a challenge to control. This is particularly the case for grid-connected applications, where several cascaded and independent control loops are necessary for each converter of the DBI. This paper presents a global current control method based on a combination of a linear proportional resonant controller and a non-linear sliding mode controller that simplifies the controller design and implementation. The proposed control method is validated using a grid-connected laboratory prototype. Experimental results show the correct performance of the controller and compliance with power quality standards.

scholarly journals Voltage Ride through Control Strategy of Modular Multilevel Converter under Unbalanced Voltage Sag

2019 ◽  
Vol 9 (3) ◽  
pp. 551
Author(s):  
Seyed Hakimi ◽  
Amin Hajizadeh
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Current Control ◽  
Adaptive Robust Control ◽  
Voltage Sag ◽  
Modular Multilevel Converter ◽  
Multilevel Converter ◽  
Control Approach ◽  
Control Loops ◽  
Unbalanced Voltage

This paper develops modeling and describes a control strategy for a modular multilevel converter (MMC) for grid-connected renewable energy systems. The proposed model can be used to simulate MMC activity during normal and faulty situations. Firstly, a dynamic model of a grid-connected MMC (GC-MMC), based upon the symmetrical component of voltages and currents, was designed. Then an adaptive robust control approach was established in order to follow the reference currents of the converter and stabilize the submodule (SM) capacitor voltage. The positive and negative sequences of reference currents that were given from the demanded active and reactive power during grid voltage disturbance and a normal situation were then utilized in control loops. Finally, the numerical results for the performance of the MMC throughout voltage sag conditions and the effect of uncertainties on the filter parameters during changing power demands were evaluated. The results specified that the current control strategy is more potent under voltage sag situations and able to fulfill the stability requirements of the MMC.

scholarly journals A Speed Control Method for Underwater Vehicle under Hydraulic Flexible Traction

2015 ◽  
Vol 2015 ◽  
pp. 1-16
Author(s):  
Yin Zhao ◽  
Ying-kai Xia ◽  
Ying Chen ◽  
Guo-Hua Xu
Keyword(s):  
Control System ◽  
Control Theory ◽  
Control Method ◽  
Sliding Mode ◽  
Variable Structure ◽  
Speed Control ◽  
Underwater Vehicle ◽  
Vehicle Speed ◽  
Sliding Mode Variable Structure ◽  
Traction System

Underwater vehicle speed control methodology method is the focus of research in this study. Driven by a hydraulic flexible traction system, the underwater vehicle advances steadily on underwater guide rails, simulating an underwater environment for the carried device. Considering the influence of steel rope viscoelasticity and the control system traction structure feature, a mathematical model of the underwater vehicle driven by hydraulic flexible traction system is established. A speed control strategy is then proposed based on the sliding mode variable structure of fuzzy reaching law, according to nonlinearity and external variable load of the vehicle speed control system. Sliding mode variable structure control theory for the nonlinear system allows an improved control effect for movements in “sliding mode” when compared with conventional control. The fuzzy control theory is also introduced, weakening output chattering caused by the sliding mode control switchover while producing high output stability. Matlab mathematical simulation and practical test verification indicate the speed control method as effective in obtaining accurate control results, thus inferring strong practical significance for engineering applications.

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