Emulating DC constant power load: a robust sliding mode control approach
TL;DR: In this article, an emulation of a programmable power electronic, constant power load (CPL) using a dc/dc step-up (boost) converter is presented, which is controlled by a robust sliding mode controller (SMC).
Abstract: This article presents emulation of a programmable power electronic, constant power load (CPL) using a dc/dc step-up (boost) converter. The converter is controlled by a robust sliding mode controller (SMC). A novel switching surface is proposed to ensure a required power sunk by the converter. The proposed dc CPL is simple in design, has fast dynamic response and high accuracy, and offers an inexpensive alternative to study converters for cascaded dc distribution power system applications. Furthermore, the proposed CPL is sufficiently robust against the input voltage variations. A laboratory prototype of the proposed dc CPL has been developed and validated with SMC realised through OPAL-RT platform. The capability of the proposed dc CPL is confirmed via experimentations in varied scenarios.
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TL;DR: An intelligent proportional-integral based on sliding mode (SM) observer to mitigate the destructive impedance instabilities of nonideal CPLs with time-varying nature in the ultralocal model sense is addressed.
Abstract: The nonlinearities and unmodeled dynamics inevitably degrade the quality and reliability of power conversion, and as a result, pose big challenges on higher-performance voltage stabilization of dc–dc buck converters. The stability of such power electronic equipment is further threatened when feeding the nonideal constant power loads (CPLs) because of the induced negative impedance specifications. In response to these challenges, the advanced regulatory and technological mechanisms associated with the converters require to be developed to efficiently implement these interface systems in the microgrid configuration. This article addresses an intelligent proportional-integral based on sliding mode (SM) observer to mitigate the destructive impedance instabilities of nonideal CPLs with time-varying nature in the ultralocal model sense. In particular, in the current article, an auxiliary deep deterministic policy gradient (DDPG) controller is adaptively developed to decrease the observer estimation error and further ameliorate the dynamic characteristics of dc–dc buck converters. The design of the DDPG is realized in two parts: (i) an actor-network which generates the policy commands, while (ii) a critic-network evaluates the quality of the policy command generated by the actor. The suggested strategy establishes the DDPG-based control to handle for what the iPI-based SM observer is unable to compensate. In this application, the weight coefficients of the actor and critic networks are trained based on the reward feedback of the voltage error, by using the gradient descent scheme. Finally, to investigate the merits and implementation feasibility of the suggested method, some experimental results on a laboratory prototype of the dc–dc buck converter, which feeds a time-varying CPL, are presented.
62 citations
Cites background from "Emulating DC constant power load: a..."
...CPL in the dc–dc converters poses a destabilizing impact on the circuit and can result in a sever voltage distractions [30], [31]....
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TL;DR: A digital control method that does not need any comparator is developed and has excellent dynamic performance thanks to its feature of reference tracking in only one switching period.
Abstract: In this study, Perturb and Observe Maximum Power Point Tracking algorithm and Model Predictive Control (MPC) algorithm are combined to improve the dynamic performance of the control structu...
40 citations
Cites result from "Emulating DC constant power load: a..."
...Some recent studies (Errouissi, Al-Durra, & Muyeen, 2016; Khosravi et al., 2017; Singh et al., 2017; ValdezResendiz et al., 2017) using these techniques are compared with the presented study....
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...Among the compared studies except from this study, the lowest dynamic response time is obtained in Singh et al. (2017), in which the step change analysis has been performed by doubling and then reducing the reference current....
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01 May 2018
TL;DR: The study shows that switching converters with a series inductor at the input port may behave as an instantaneous constant power load under sliding-mode control based on a nonlinear switching surface representing the error between the input power of the converter and a suitable power reference.
Abstract: In this paper, a systematic approach is presented to synthesize constant power loads using switching converters under sliding mode control. The study shows that switching converters with a series inductor at the input port may behave as an instantaneous constant power load under sliding-mode control based on a nonlinear switching surface representing the error between the input power of the converter and a suitable power reference. With the proposed approach, the synthesis and design of constant power loads is simple. The synthesized loads can offer an inexpensive alternative to analyze switching converters feeding constant power loads such as in dc distributed power systems and electric vehicles. The theoretical derivations are validated by numerical simulations performed on the detailed switched model of boost, SEPIC and Cuk converters.
13 citations
TL;DR: The proposed adaptive perturb and observe (P&O) algorithm provides better results using the OPAL-RT simulator compared to the P&O method using MATLAB/SIMULINK™.
Abstract: This paper proposes an adaptive maximum power point tracking (MPPT) control method to achieve the maximum power from the wind turbine (WT) power generation system. The MPPT control method has a vit...
11 citations
TL;DR: The design procedure yields a simple, economical and small-size prototype that can be useful in the experimental validation of converters supplying constant power loads and establishes the existence conditions for sliding-mode and the stability of the resulting ideal dynamics.
Abstract: This paper presents a systematic approach to synthetize constant power loads using switching converters under sliding-mode control. The generation of sliding motions is analyzed in converters with a series inductor in the input port and a switching function representing the error between the input power and a suitable power reference. The analysis establishes the existence conditions for sliding-mode and the stability of the resulting ideal dynamics. Simulation and experimental results verifying the theoretical predictions in boost, Cuk and SEPIC converters illustrate the proposal. The design procedure yields a simple, economical and small-size prototype that can be useful in the experimental validation of converters supplying constant power loads.
8 citations
Cites methods from "Emulating DC constant power load: a..."
...A third approach is based on the use of SMC with a nonlinear switching surface in a boost converter, which emulates successfully a CPL in [25] showing the advantages of this type of control in the presence of line and load...
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References
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TL;DR: A robust control with time-delay concept is introduced for regulating a boost converter capacitor output voltage to keep the output voltage constant under input voltage variations with fast response, and little overshoot and ripples.
Abstract: This paper studies a robust control for regulating a boost converter capacitor output voltage The boost converter is inherently a highly nonlinear system that displays interconnected state variables and system parameter variations due to load change with input disturbances Therefore, a robust control scheme is required to cope with these characteristics The main objective of controlling the capacitor output voltage is to keep the output voltage constant under input voltage variations with fast response, and little overshoot and ripples To satisfy this objective, a robust control with time-delay concept is introduced The control utilizes time-delayed switching input to the converter, as well as output current and voltage variables, to replace the unknown dynamics and disturbance To prove the effectiveness of the algorithm, two operating point variations are considered: variations in source voltage, and changes in output load Simulations are performed using MATLAB/Simulink to show the effectiveness of the algorithm by choosing the output voltage lift, drop, settling time, and ripples as the system performance criteria Then, a comparison of the results is made of the proportional and integral control, and the sliding mode control An experimental test is also performed to demonstrate the effectiveness of the system
130 citations
"Emulating DC constant power load: a..." refers methods in this paper
...SMC ensures invariance towards variation in load, parameters and this controller is widely used to regulate power converters (Kumar & Jeevananthan, 2012; Martinez-Salamero et al., 2013; Oucheriah & Guo, 2013; Ravichandran et al., 2013; Wang et al., 2014)....
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TL;DR: The consistency of the experimental results with the simulation results proves the ability of the emulator and the proposed testing approach, and the feasibility of connecting a particular machine to a grid under various load conditions can be examined without the need for any electromechanical machinery.
Abstract: This paper presents a method of emulating electrical loads using power electronic converters. The loads include machines such as induction motors and their associated mechanical load and also more complex machine systems such as wind-driven generators. The load emulator is, effectively, a dynamically controllable source or sink which is capable of bidirectional power exchange with either a grid or another power electronic converter system. Using load emulation, the feasibility of connecting a particular machine to a grid under various load conditions can be examined without the need for any electromechanical machinery. This paper considers the case of a power electronic voltage source inverter (VSI) emulating a three-phase induction motor connected to a three-phase ac grid. The VSI is operated in a mode where the current drawn from the ac grid is controlled by closed-loop control. The consistency of the experimental results with the simulation results proves the ability of the emulator and the proposed testing approach.
119 citations
"Emulating DC constant power load: a..." refers background in this paper
...…of Technology Jodhpur, Jodhpur 342011, India © 2017 Informa UK Limited, trading as Taylor & Francis Group Hametner, Prochart, and Jakubek (2014), Newton, Betz, and Penfold (1995), Paing and Zane (2006), Rahimi, Khaligh, and Emadi (2006), Rao and Chandorkar (2010) and Thorne and Kazerani (2009)....
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...Emulation of three-phase induction motor load connected to the grid and wind-driven generator load based on voltage source inverter is presented in Rao and Chandorkar (2010)....
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...Chang et al. (1997), Deese and Nwankpa (2006), Hsieh and Li (1993), Kazerani (2008), Newton et al. (1995) and Rao and Chandorkar (2010) have presented emulation of controllable AC loads....
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TL;DR: In this paper, a method to design a fault-tolerant stabilizing system for a dc-microgrid with CPLs is presented, which consists in implementing a local stabilizing agent on each CPL.
Abstract: It is known that constant power loads (CPLs) can yield instability in dc-power systems under certain operating conditions. This instability phenomenon is due to the interaction between the dc-grid and the negative input impedance characteristic of the CPLs. Dynamic behavior and stability analysis of a dc-microgrid with CPLs is presented in this paper. Then, a method to design a fault-tolerant stabilizing system for a dc-microgrid with CPLs is presented. It consists in implementing a local stabilizing agent on each CPL. Then, a method to design the stabilizing system is proposed. The method is based on the definition and resolution of a constrained optimization problem. It permits to consider several fault scenarios, such as the electrical reconfiguration of the dc-microgrid, or the failure of an agent. To illustrate the method's effectiveness, it has been implemented and experimentally tested on a test bed.
88 citations
"Emulating DC constant power load: a..." refers background in this paper
...The stability and dynamics of a dc micro-grid in the presence of CPL has been analysed in Magne et al. (2014) and it has been shown that high penetration of CPLs poses a severe stability challenge....
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TL;DR: Nonlinear local model networks are used to obtain dynamic battery models with high fidelity that can be computed in real time that results in superior dynamic performance and stable dc-bus voltage control even for testing of tightly controlled electric motor inverters with negative differential input resistance.
Abstract: Battery emulation with a controllable high-power dc supply enables repeatable hardware-in-the-loop testing of powertrains for hybrid and electric vehicles. For this purpose, not only the power flow but also the nonlinear characteristic and dynamic impedance of batteries need to be emulated. In this paper, nonlinear local model networks are used to obtain dynamic battery models with high fidelity that can be computed in real time. This approach also allows the extraction of local linear impedance models for high-bandwidth impedance emulation, leading to a tighter coupling between the test bed and simulation model with predictable closed-loop dynamics. A model predictive controller that achieves optimal control with adherence to system constraints is extended to impedance control and robustness against constant power loads. This results not only in superior dynamic performance but also in stable dc-bus voltage control even for testing of tightly controlled electric motor inverters with negative differential input resistance. Since the controller design is based on a model of the test bed setup including the virtual battery model, emulator hardware, and input characteristics of the powertrain under test, it is possible to systematically analyze stability.
88 citations
TL;DR: The analysis and design of a sliding-mode control of a boost converter operating in continuous conduction mode that minimizes the inrush current and provides output voltage regulation in front of input voltage perturbations and load changes is presented.
Abstract: This paper presents the analysis and design of a sliding-mode control of a boost converter operating in continuous conduction mode that minimizes the inrush current and provides output voltage regulation in front of input voltage perturbations and load changes. The analytical expression of the inrush current is obtained, and the conditions to minimize the current peak are derived. The resulting controller is implemented analogically and employs two switching surfaces. Namely, one surface is combined with the conventional auxiliary diode branch for the start-up, while another one is used for the voltage regulation in steady state. Experimental results are in perfect agreement with the theoretical predictions.
71 citations
"Emulating DC constant power load: a..." refers methods in this paper
...SMC ensures invariance towards variation in load, parameters and this controller is widely used to regulate power converters (Kumar & Jeevananthan, 2012; Martinez-Salamero et al., 2013; Oucheriah & Guo, 2013; Ravichandran et al., 2013; Wang et al., 2014)....
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