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.
Citations
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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: This paper focuses on the primal version of the new algorithm, an algorithm for minimizing a nonlinear function subject to nonlinear inequality constraints, which applies sequential quadratic programming techniques to a sequence of barrier problems.
Abstract: An algorithm for minimizing a nonlinear function subject to nonlinear inequality constraints is described. It applies sequential quadratic programming techniques to a sequence of barrier problems, and uses trust regions to ensure the robustness of the iteration and to allow the direct use of second order derivatives. This framework permits primal and primal-dual steps, but the paper focuses on the primal version of the new algorithm. An analysis of the convergence properties of this method is presented.
1,514 citations
TL;DR: Sliding-mode and feedback linearization techniques along with large-signal phase plane analysis are presented as methods to analyze, control, and stabilize automotive converters/systems operating with CPLs.
Abstract: Power electronic converters and electric motor drives are being put into use at an increasingly rapid rate in advanced automobiles. However, the new advanced automotive electrical systems employ multivoltage level hybrid ac and dc as well as electromechanical systems that have unique characteristics, dynamics, and stability problems that are not well understood due to the nonlinearity and time dependency of converters and because of their constant power characteristics. The purpose of this paper is to present an assessment of the negative impedance instability concept of the constant power loads (CPLs) in automotive power systems. The main focus of this paper is to analyze and propose design criteria of controllers for automotive converters/systems operating with CPLs. The proposed method is to devise a new comprehensive approach to the applications of power electronic converters and motor drives in advanced automotive systems. Sliding-mode and feedback linearization techniques along with large-signal phase plane analysis are presented as methods to analyze, control, and stabilize automotive converters/systems with CPLs
813 citations
TL;DR: In this paper, the authors investigate passive damping as a general method to stabilize power systems with CPLs, using a representative system model consisting of a voltage source, an LC filter, and an ideal CPL, and demonstrate that a CPL system can be stabilized by a simple damping circuit added to one of the filter elements.
Abstract: This paper addresses stability problems in power systems with loads that exhibit constant-power behavior. Instability may occur in such systems due to the negative incremental impedance of constant-power loads (CPLs). Existing approaches to stabilizing such systems require modification of the source and/or the load control characteristics, or isolating the CPL from the rest of the system by additional active devices, which are difficult to implement and often conflict with other system requirements such as control bandwidth, size, weight, and cost. In this paper, we investigate passive damping as a general method to stabilize power systems with CPL. Using a representative system model consisting of a voltage source, an LC filter, and an ideal CPL, we demonstrate that a CPL system can be stabilized by a simple passive damping circuit added to one of the filter elements. Three different damping methods are considered and analytical models are developed for each method to define damping parameters required for stabilizing the system. Time- and frequency-domain measurements from an experimental system are presented to validate the methods.
444 citations
TL;DR: The implementation of novel active-damping techniques on dc/dc converters has been shown and the proposed active- damping method is used to overcome the negative impedance instability problem caused by the CPLs.
Abstract: Multi-converter power electronic systems exist in land, sea, air, and space vehicles. In these systems, load converters exhibit constant power load (CPL) behavior for the feeder converters and tend to destabilize the system. In this paper, the implementation of novel active-damping techniques on dc/dc converters has been shown. Moreover, the proposed active-damping method is used to overcome the negative impedance instability problem caused by the CPLs. The effectiveness of the new proposed approach has been verified by PSpice simulations and experimental results.
422 citations
Additional excerpts
...…& Millar, 2004; Emadi, Khaligh, Rivetta, & Williamson, 2006; Liutanakul, Awan, Pierfederici, Nahid-Mobarakeh, & Meibody-Tabar, 2010; Magne, Nahid-Mobarakeh, & Pierfederci, 2014; Marx, Magne, NahidMobarakeh, Pierfederici, & Davat, 2012; Rahimi, Williamson, & Emadi, 2010; Rahimi & Emadi, 2009)....
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TL;DR: In this paper, the authors present tools allowing large signal stability analysis of a dc power system, which allows estimation of the domain of attraction of the system operating point, and the impact of the load dynamics on stability is also studied.
Abstract: Electric motor drives and power electronic converters have become increasingly common in advanced power systems. Passive LC filters are used in these systems to reduce the power ripples. These filters are usually poorly damped for reducing the losses as well as the size/weight and the cost of the system. This leads to instability phenomena if the load power exceeds a power limit depending on the filter parameters. The purpose of this paper is to present tools allowing large signal stability analysis of a dc power system. These tools allow estimation of the domain of attraction of the system operating point. It will be shown that this large signal stability analysis gives useful hints on the design of the system to optimize the stability criteria for constant and variable power loads. The impact of the load dynamics on stability is also studied. An electric drive connected to a dc power supply through a poorly damped LC filter is used as a case study. The simulations and the experimentations confirm the analytical results.
283 citations