Supercapacitors come under different names and scientific nominations as Ultracapacitors (UCs) or double layer capacitors, or electrochemical capacitors, they are considered as promising technological devices used for storing energy in the field of energy storage systems. They are able to deliver high power and enable high load currents in addition their ability to bridge power gaps. As we will notice, they have fast yet complicated charging/discharging mechanism interpretations. This paper will provide an overview on different equivalent circuits of a supercapacitor, and will highlight the concept of unbalanced series of connected ultracapacitors and different options in rectifying such unbalance. The balancing of supercapacitors connected in series can come in different modes passive or active and maybe hybrid. A comparison between the different modes will be executed using MATLAB/Simulink and results will be shown based on the economical and performance perspectives.
The microgrid is an emerging trend in modern power systems. Microgrids consist of controllable power sources, storage, and loads. An elaborate control infrastructure is established to regulate and synchronize the interaction of these components. The control scheme is divided into a hierarchy of several layers, where each layer is composed of multi-agents performing their dedicated functions and arriving at a consensus of corrective values. Lateral and horizontal interaction of such multi-agents forms a comprehensive hierarchical control structure that regulates the microgrid operation to achieve a compendium of objectives, including power sharing, voltage, and frequency regulation. The success of a multi-agent-based control scheme is dependent on the health of the communication media that is used to relay measurements and control signals. Delays in the transmission of control signals result in an overall deterioration of the control performance and non-convergence. This paper proposes novel multi-agent moving average estimators to mitigate the effect of latent communication links and establishes a hierarchical control scheme incorporating these average estimators to accurately arrive at system values during communication delays. Mathematical models are established for the complete microgrid system to test the stability of the proposed method against conventional consensus-based methods. Case-wise simulation studies and lab-scale experimental verification further establish the efficacy and superiority of the proposed control scheme in comparison with other conventionally used control methods.
The article highlights and optimizes a controller for the single ended primary inductance converter (SEPIC) direct current-direct current (DC-DC) converter. The SEPIC converter adjusts a range of dc input voltages and delivers a constant and stable output voltage. Three different models of the SEPIC converter are presented in order to derive its transfer function. Being a 4th order, an approximation method for the reduction of this transfer function to 2nd and 1st order is implemented. Two methods for controlling the converter are presented, the first one is based on guessing techniques and the second explains the design steps of the controller based on the internal model control (IMC). Furthermore, an improvement on the IMC controller is proposed and results were shown and discussed. IMC is based on integrating the “process model” in the control operation of the actual system. By using an approximation of the original transfer function of the system, it is expected that the IMC control will be able to achieve the desired results. Control schemes of the SEPIC will be presented and results will be shown. The response of the controller was tested with mathematical models for batteries and supercapacitors in MATLAB, as non-ideal DC-sources, and results were presented.
The work is devoted to increasing the energy efficiency of uninterruptible power supplies in enterprises with a continuous technological cycle. During the operation of continuous technological processes, a power failure even for a short period of time leads to significant economic damage. The most modern technical solution to this problem is the creation of guaranteed power supply systems using diesel power plants (DES) and uninterruptible power supplies (UPS), based on rechargeable batteries and supercapacitor modules. It is proposed to use supercapacitors in parallel with the battery in order to ensure the stable operation of the diesel generators under starting conditions, as well as during load transfer. In this case, when using supercapacitors, it becomes possible to reduce the power capacity of the generators and uninterruptible power supplies along with the size of their batteries. Therefore, the cost of the solution decreases and its energy efficiency increases. To test the efficiency of the system, a computer model was created using MATLAB. The system showed a successful operation in supplying the load from all the power sources as well as maintaining Unity Power Factor at the Mains/Generator side.
Nowadays, diesel power plants (DPS) are widely used as sources of primary, backup or emergency power supply for various facilities. Mathematical modeling and optimization techniques are widely used for studies in order to improve energy and economic efficiency of diesel power plants. The article describes the modeling of a stand-alone electromechanical power system consisting of a Diesel Power Plant and an ESS (Energy Storage System) based on supercapacitors with a load of comparable power of a diesel motor to increase its energy efficiency.
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