Constant power loads (CPL) with microgrids: problem definition, stability analysis and compensation techniques
TL;DR: In this paper, the authors provide a comprehensive review of the major concepts associated with the μgrid, such as constant power load (CPL), incremental negative resistance or impedance (INR/I), and its dynamic behaviors on the μ-grid, and power system distribution.
Abstract: This paper provides a comprehensive review of the major concepts associated with the μgrid, such as constant power load (CPL), incremental negative resistance or impedance (INR/I) and its dynamic behaviours on the μgrid, and power system distribution (PSD). In general, a μgrid is defined as a cluster of different types of electrical loads and renewable energy sources (distributed generations) under a unified controller within a certain local area. It is considered a perfect solution to integrate renewable energy sources with loads as well as with a traditional grid. In addition, it can operate with a conventional grid, for example, by energy sourcing or a controllable load, or it can operate alone as an islanding mode to feed required electric energy to a grid. Hence, one of the important issues regarding the μgrid is the constant power load that results from the tightly designed control when it is applied to power electronic converters. The effect of CPL is incremental negative resistance that impacts the power quality of a power system and makes it at negative damping. Also, in this paper, a comprehensive study on major control and compensation techniques for μgrid has been included to face the instability effects of constant power loads. Finally, the merits and limitations of the compensation techniques are discussed.
Citations
More filters
18 Oct 2018
TL;DR: This study analyses and presents a comprehensive review of the most recent growth in the DC microgrid protection, the fault characteristics of DC microgrids, the impact of constant power loads, the protection devices and several proposed methods to overcome the protection problems are discussed.
Abstract: A direct current (DC) microgrid has become a superior power system in recent years due to the development of DC loads and higher efficiency of DC systems. One of the challenging problems on DC microgrids operation is protection, and it is still a particular concern associated with the challenges of developing a proper protection scheme owing to its characteristics and lack of standards in DC protection. Due to the significant increasing interest on DC microgrid; this study investigates protection problems and schemes that need to be addressed in modern power systems involving DC microgrids. This study analyses and presents a comprehensive review of the most recent growth in the DC microgrids protection. Additionally, the fault characteristics of DC microgrids, the impact of constant power loads, the protection devices and several proposed methods to overcome the protection problems are discussed. The differences between the proposed protection methods for the DC microgrids are also discussed.
126 citations
TL;DR: This review article is intended to be a preface to the Special Issue on Voltage Stability of Microgrids in Power Systems and presents a comprehensive review of the literature on voltage stability of power systems with a relatively high percentage of IBGs in the generation mix of the system.
Abstract: The main purpose of developing microgrids (MGs) is to facilitate the integration of renewable energy sources (RESs) into the power grid. RESs are normally connected to the grid via power electronic inverters. As various types of RESs are increasingly being connected to the electrical power grid, power systems of the near future will have more inverter-based generators (IBGs) instead of synchronous machines. Since IBGs have significant differences in their characteristics compared to synchronous generators (SGs), particularly concerning their inertia and capability to provide reactive power, their impacts on the system dynamics are different compared to SGs. In particular, system stability analysis will require new approaches. As such, research is currently being conducted on the stability of power systems with the inclusion of IBGs. This review article is intended to be a preface to the Special Issue on Voltage Stability of Microgrids in Power Systems. It presents a comprehensive review of the literature on voltage stability of power systems with a relatively high percentage of IBGs in the generation mix of the system. As the research is developing rapidly in this field, it is understood that by the time that this article is published, and further in the future, there will be many more new developments in this area. Certainly, other articles in this special issue will highlight some other important aspects of the voltage stability of microgrids.
56 citations
Cites background from "Constant power loads (CPL) with mic..."
...In case of an improper converter control, the load voltage may drop to very small values close to zero and may lead to complete voltage collapse [54]....
[...]
TL;DR: A composite prescribed performance control strategy is developed for stabilizing dc/dc boost converter feeding constant power loads by employing the exact feedback linearization technique and the composite nonlinear controller with prescribed performance is determined.
Abstract: In this paper, a composite prescribed performance control strategy is developed for stabilizing dc/dc boost converter feeding constant power loads. First, by employing the exact feedback linearization technique, the nonlinear uncertain dc converter system is first transformed into the Brunovsky’s canonical form. Then, a nonlinear disturbance observer is utilized to evaluate the dynamic change of load power and the accuracy of output voltage regulated by feedforward compensation. Next, the prescribed performance controller is elaborately designed to ensure that the tracking error of output voltage is always within the margin of predefined error bounds. Based on the backstepping design approach, the composite nonlinear controller with prescribed performance is determined. Finally, the numerical simulation results are presented to demonstrate the tracking performance of the proposed controller.
43 citations
Cites background from "Constant power loads (CPL) with mic..."
...feedback linearization [5], [22], which can achieve largesignal stability and unlimited values of CPLs....
[...]
TL;DR: The proposed energy management strategy (EMS) for a DC microgrid to supply power to rural communities with solar, wind, fuel cell, and batteries as input sources is offered and the performance of the system is analyzed based on different operating conditions of the input sources.
Abstract: The AC and DC power system structures need to be modernized to meet consumer demands. DC microgrids are suitably admired due to their high efficiency, consistency, reliability, and load sharing performance, when interconnected to DC renewable and storage sources. The main control objective for any DC microgrid is providing proper load–power balancing based on the Distributed Generator (DG) sources. Due to the intermittent nature of renewable energy sources, batteries play an important role in load–power balancing in a DC microgrid. The existing energy management strategy may be able to meet the load demand. However, that technique is not suitable forrural communities’ power system structure. This research offers an energy management strategy (EMS) for a DC microgrid to supply power to rural communities with solar, wind, fuel cell, and batteries as input sources. The proposed EMS performs the load–power balancing between each source (renewable and storage) in a DC microgrid for dynamic load variation. Here, the EMS handles two battery sources (one is used to deliver power to the priority load, and the other is utilized in the common DC bus) to meet the required demand. The proposed EMS is capable of handling load–power balancing using renewable energy sources with less consumption of non- conventional energy sources (such as a diesel generator). The performance of the system is analyzed based on different operating conditions of the input sources. The MATLAB/Simulink simulation model for the proposed DC microgrid with their EMS control system is developed and investigated, and their results are tabulated under different input and load conditions. The proposed EMS is verified through a laboratory real-time DC microgrid experimental setup, and the results are discussed.
42 citations
TL;DR: In this article, the authors presented an optimal scheduling of vehicle-to-grid using the genetic algorithm to minimize the power grid load variance, which is achieved by allowing electric vehicles charging (grid-tovehicle) whenever the actual power grid loading is lower than the target loading, while conducting electric vehicle discharging (vehicle-togrid) whenever a higher load is higher than target loading.
Abstract: The introduction of electric vehicles into the transportation sector helps reduce global warming and carbon emissions. The interaction between electric vehicles and the power grid has spurred the emergence of a smart grid technology, denoted as vehicle-to grid-technology. Vehicle-to-grid technology manages the energy exchange between a large fleet of electric vehicles and the power grid to accomplish shared advantages for the vehicle owners and the power utility. This paper presents an optimal scheduling of vehicle-to-grid using the genetic algorithm to minimize the power grid load variance. This is achieved by allowing electric vehicles charging (grid-to-vehicle) whenever the actual power grid loading is lower than the target loading, while conducting electric vehicle discharging (vehicle-to-grid) whenever the actual power grid loading is higher than the target loading. The vehicle-to-grid optimization algorithm is implemented and tested in MATLAB software (R2013a, MathWorks, Natick, MA, USA). The performance of the optimization algorithm depends heavily on the setting of the target load, power grid load and capability of the grid-connected electric vehicles. Hence, the performance of the proposed algorithm under various target load and electric vehicles’ state of charge selections were analysed. The effectiveness of the vehicle-to-grid scheduling to implement the appropriate peak load shaving and load levelling services for the grid load variance minimization is verified under various simulation investigations. This research proposal also recommends an appropriate setting for the power utility in terms of the selection of the target load based on the electric vehicle historical data.
42 citations
References
More filters
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
"Constant power loads (CPL) with mic..." refers background in this paper
...A multiconverter has a large variety of operation instructions because of the interconnection of components of the multiconverter [22,36,37]....
[...]
...Some power systems need a multiconverter to provide the system with various power and voltage forms [22,36,37]; these are known as multiconverter power electronic system [24,25]....
[...]
...The load converters (second stage of multiconverter) tend to display the properties of a constant power load when control is applied tightly [22,36,37], which means a converter has a fast response and low output ripple [37]; therefore, the converter behaves as the CPL with their control bandwidth [39]....
[...]
...The converters (second stage of multiconvert r) ten to display th properties of a constant power load when control is applied tightly [22,36,37], which means a converter has a fa t response and low output ripple [37]; therefore, the converter behaves as the CPL with their control bandwidth [39]....
[...]
...Many loads like motor drives or electronic loads with tightly regulated controllers behave as a constant power load [22,36,37]....
[...]
Book•
01 Jan 2014
TL;DR: In this article, the authors present the final activity report of energycon 2018 and discuss microgrid architectures and control, including free e-books download from the Wiley online library.
Abstract: publishable final activity report cordis. pac world magazine microgrids architectures and controls. microgrids architectures and control wiley online library. microgrids architectures and control wiley ieee ebook. wele energycon2018. microgrids architectures and control free ebooks download. microgrids architectures and control edition 1 by nikos. microgrids architectures and control scribd. enclosures and accessories schneider electric. publications stream wise list iit kanpur. microgrid
514 citations
"Constant power loads (CPL) with mic..." refers methods in this paper
...The μgrid was introduced as an efficient solution to guarantee the reliable operation of distribution generating (DG) when DGs operate in connected mode or islanded mode [6,25,29,30]....
[...]
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
"Constant power loads (CPL) with mic..." refers methods in this paper
...This method in [39,59] is valid for small disturbances [60]....
[...]
...Passive damping is a simple method to increase the damping of a system by adding passive elements; which are contain resistance (R), inductor (L) and capacitor (C), to the input filter of the system, as described in [39,59]....
[...]
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
"Constant power loads (CPL) with mic..." refers background or methods in this paper
...Active damping has received inter st from res arche s [34,45,54,58,63–68,73]; however, active damping causes effect ve performance but only comp nsates for li it d values of CPL [25] and sometimes causes th output voltage t drop, as in [63]....
[...]
...Active damping has received interest from researchers [34,45,54,58,63–68,73]; however, active damping causes effective performance but only compensates for limited values of CPL [25] and sometimes causes the output voltage to drop, as in [63]....
[...]
...It guarantees that any extra power does not dissipate into the system [45,63,64], as in Figure 8a....
[...]
...In [63] the authors presented a new method to overcome the problems of CPL by adding virtual resistance, which will affect the series resistance with an inductor to feedback control system....
[...]
...Also, it can be achieved by adding a device that injects a compensating current [63]....
[...]
TL;DR: The authors in this article reviewed all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments.
Abstract: Electric vehicles (EV), including Battery Electric Vehicle (BEV), Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), are becoming more commonplace in the transportation sector in recent times. As the present trend suggests, this mode of transport is likely to replace internal combustion engine (ICE) vehicles in the near future. Each of the main EV components has a number of technologies that are currently in use or can become prominent in the future. EVs can cause significant impacts on the environment, power system, and other related sectors. The present power system could face huge instabilities with enough EV penetration, but with proper management and coordination, EVs can be turned into a major contributor to the successful implementation of the smart grid concept. There are possibilities of immense environmental benefits as well, as the EVs can extensively reduce the greenhouse gas emissions produced by the transportation sector. However, there are some major obstacles for EVs to overcome before totally replacing ICE vehicles. This paper is focused on reviewing all the useful data available on EV configurations, battery energy sources, electrical machines, charging techniques, optimization techniques, impacts, trends, and possible directions of future developments. Its objective is to provide an overall picture of the current EV technology and ways of future development to assist in future researches in this sector.
372 citations
"Constant power loads (CPL) with mic..." refers background in this paper
...The development of electronic switch devices has led to penetrations of power electronic applications in a power system [1,2], advanced control approaches, and more renewable energy sources [3], and on the other hand an increase in energy demands that has consequently led to increased environmental problems such as greenhouse gases being emitted from non-renewable energy sources [4,5]; all these factors have contributed to the appearance of new applications in power systems and have taken many forms in modern life [6]....
[...]