Energy management system for critical loads using power electronics

The aim of this paper is to give an brief work about an Energy management system (EMS) for critical loads using power electronics hybrid power sources (grid and photovoltaic cells) with battery storage and this whole EMS system is used to control the peak power for ac loads and continuous power supply to the critical loads. Photo voltaic cells are used for battery charging purpose, battery will be discharge at two conditions. One is when grid is shut down and another one is sudden increase in critical or non- critical loads by users.

Here EMS with hybrid power sources guaranties that the continuous supply of electrical power to the critical loads with or without grid with the help of stored energy from batteries.

The system monitoring, controlling, and optimizing the working of the generation and/or transmission system can be done through Computer Aided tools by operators are known as Ems. The main purpose of using solar or photovoltaic cells to produce more power and that can be stored in batteries.

The photovoltaic systems are broadly classified as standalone system and grid connected system. Here batteries are mainly used to improve reliability of the standalone system. The generated pv power is fed to the grid, or it supplies linear and non linear loads connected at the ac side. In this paper hybrid system (grid and solar) with battery is used to compensate the mismatch between the generation and local demand at load side. The EMS in this paper includes energy storage in the form of batteries in order to accomplish three main goals.

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Store energy produced by pv cells or by electric power is least expens ive.

A grid-connected PV system with a battery backup has many advantages such as peak shaving to generate power during peak load hours, and therefore, the grid-side inverter should operate at any condition to supply uninterrupted power to the critical loads during grid fails or sudden increases in load. When the solar radiation is less, the power quality is decreases as compared to the total harmonic distortion (THD) of the line currents, which are inversely proportional to the power into the grid. The proposed PV and grid (hybrid) system consists of three power sources (grid, PV array, and battery), two power sinks (battery, and load), and EMS for load leveling or peak shaving.

The EMS proposed in this paper includes energy storage in the form of batteries in order to accomplish these main goals: Make electric power available to critical loads at all times with or without grid. Reduce peak power consumption to lower electricity costs. Store energy produced by pv cells or by electric power is least expensive. Peak shaving is controlled quickly at the time of high power demand at load side by energy storage system. Islanding or standalone mode of operation can be done, when the grid power is not available. Battery charging mode through photovoltaic panels.

Lots of authors reseached on this EMS with different statergies, they solved many problems like smartb meters problems with solution , controlling of droop in Inverters, high frequency problems in ac microgrids, use of cascaded dual buck converter with renewable energy applications. Many authors fouced on energy management system with dc loads, but in this we are focusing on EMS with solar and ac loads. For house hold energy management system can be built with smart meters to get detailed information about users consumption of power with bill. The EMS presented in this paper includes batteries, three leg power module controlled by FPGA. The Fig. 1 shows the EMS architecture with critical and non critical loads. Three legs of the power IGBT is use to control power flow of the buck and boost converter and single-phase voltage source operation (H-bridge inverter) of the respected module [10]. The H-bridge inverter is connected to an output (LC filter) to produce the sinusoidal voltage for the ac loads. Critical loads are those loads to which power supply has to maintain at any condition. Here critical loads are connected in parallel to Vac with h bridge inverter for continuous service to these critical loads using a thyristor switches. Noncritical loads are also connected in parallel to Vac but these are powered when necessary by using a thyristor switch. Here buck and boost converters are used to control the dc bus voltage as user’s preference.Battery supply additional current to the load when sudden increase in critical load. Islanding mode occurs when EMS or source is disconnected from the system and critical load can be decreased at that time battery can discharge stored energy to the critical loads. Shedding of non critical loads can be done at the high demand of critical loads and batteries can supply stored energy to critical loads to manage energy or load leveling.

By using this technique of energy management system critical load are powered even if AC grid fails. The control system designed to perform the experimental implementation of typical scenarios is presented in this .the EMS supports critical loads when the ac grid becomes unavailable or sudden increase in load and how the connection to the ac grid is restored by the EMS when the ac grid becomes available again. Additionally, the EMS can have other advantageous tasks such as peak shaving. Experimental measurements with linear and nonlinear loads demonstrate how the EMS, controlled in current mode, provides some of the power to the loads to accomplish peak shaving, thus reducing the cost of electricity.