HYBRID UNINTERRUPTABLE POWER SUPPLY ENERGY STORAGE SYSTEM USING SUPER CAPACITOR AND BATTERY

Size: px

Start display at page:

Download "HYBRID UNINTERRUPTABLE POWER SUPPLY ENERGY STORAGE SYSTEM USING SUPER CAPACITOR AND BATTERY"

Georgina Gibbs
5 years ago
Views:

1 HYBRID UNINTERRUPTABLE POWER SUPPLY ENERGY STORAGE SYSTEM USING SUPER CAPACITOR AND BATTERY P.Anand 1 R.Venkatesh 2 1 (EEE Department, M.E., Scholar, SNS College of Engineering, Coimbatore, India) 2 (EEE Department, Assistant professor, SNS College of Engineering, Coimbatore, India) Abstract Power interruption is the major problem in many sectors, to overcome this interruption renewable energy systems are used. The utilization of wind as renewable sources causes uncontrollable fluctuations in power generation. So energy storage is needed. However, since it is not possible to cover fast power fluctuations without dramatically reducing the battery s lifetime. A control concept of the UPS operation, according short and long failure of the supply utility voltage is developed. Hybrid UPS consists of two controlled energy storage systems. The first one is a static energy storage system based on super capacitor bank. The second energy source is a lead acid battery. The super capacitor mitigates the short term fluctuation in wind generator and also reduces drawing of pulsating power from the battery. The proposed method has a variable speed wind turbine using a permanent magnet synchronous generator (PMSG), integrated with the grid system. This combination with hybrid UPS reduces the wind turbine fluctuation and voltage variation. The design, simulation development and study are accomplished using MATLAB Simulink tool box. A prototype has been developed and it is used to perform and verify the simulation studies. Keywords PIC Microcontroller; Ultra Capacitor; DC Motor; Brige Rectifier 1. INTRODUCTI In recent years, power variations and energy criteria have been the main motivations for developing Uninterruptible Power Supply (UPS) system. In many industry sectors, high reliability power supply is required for critical loads. Uninterruptible power supplies (UPS) are used to improve power quality and guarantee the reliability of backup power. During voltage sags or complete interruptions of the power supply, the energy has to be supplied by local energy storage systems (ESS). Conventional ESS for UPS is basically relying on the choice of good lead-acid batteries. The battery is the source of energy which is delivered to load usually through DC/AC power electronic converter. A capacity of the battery storage is rated from seconds to hours or even days. In this paper, super capacitor is used to overcome the disadvantages. Super capacitors represent one of the newest innovations in the field of electrical energy storage, and will find their place in many applications where energy storage can help to the smoothing of strong and short time power solicitations of a distribution network. A super capacitor is a double-layer electrochemical capacitor that can store thousand times more energy than a typical capacitor. It shares the characteristics of both batteries and conventional capacitors and has an energy density about 20% of a battery. Moreover, they have almost negligible losses and long Lifespan. They can process a large number of charge and discharge cycles (several hundred thousand cycles) compared to only a few thousand cycles for leadacid batteries and can supply much higher currents than batteries. Batteries are mostly efficient when used to supply low, reasonably steady power levels. Super capacitors are very effective in storing charge for later use. Their leakage rate and series resistance are quite small. The power sharing between super capacitors, and batteries is a promising solution for improving system performance due to the dynamic behaviour of the SCs and their long life. Renewable Energy Systems (RES) is also an independent power producer, owning and operating a growing portfolio of wind farms around the world. Bi-directional converters are used in connecting energy storage systems like super capacitors and battery banks to wind power systems. The wind turbine is coupled with permanent-magnet synchronous generator. With this interfacing RES based output is controlled, load shared and maintained to UPS system. An applications of super capacitor and battery tie is used in pure battery powered electric vehicle, hybrid electric vehicle and in escalators. Simulation results are provided for maintaining the load and sharing the dc voltage to UPS system and reducing the stress in battery to show the effectiveness of the proposed system. 2. MPPT CTROL METHODS IN WIND ENERGY SYSTEM Wind energy conversion systems have been attracting wide attention as a renewable energy source due to depleting fossil fuel reserves and environmental concerns as a direct consequence of using fossil fuel and nuclear energy sources. Wind energy, even though abundant, varies continually as wind speed changes throughout the day. The amount of power output from a wind energy conversion system (WECS) depends upon the accuracy with which the peak power points are tracked by the maximum power point tracking (MPPT) controller of the WECS control system irrespective of the type of generator used. The study provides a review of past and present MPPT controllers used for extracting maximum IJREE - International Journal of Research in Electrical Engineering Volume: 04 Issue:

2 power from the WECS using permanent magnet synchronous generators (PMSG), squirrel cage induction generators (SCIG) and doubly fed induction generator (DFIG). These controllers can be classified into three main control methods, namely 1. Tip speed ratio (TSR) control 2. Power signal feedback (PSF) 3. Hill climb search (HCS) 3. BLOCK DIAGRAM BASED TIP SPEED RATIO &DESCRIPTI The overall block diagram of the project with tip speed ratio is shown in figure 1.The rectifier is connected to the wind generator, it converts Dc to Ac, and the output is variable. The TSR control method regulates the rotational speed of the generator in order to maintain. The TSR to an optimum value at which power extracted is maximum. This method requires both the wind speed and the turbine speed to be measured or estimated in addition to requiring the knowledge of optimum TSR of the turbine in order for the system to be able extract maximum possible power. Figure 1 Block Diagram Based On Tip Speed Ratio The load is connected to the grid. The battery and super capacitor tie is connected to bi-directional converter, it is controlled by PI controller. Normally when there is a demand and wind generator doesn t meet the demanded power, the battery acts as a backup. But when heavy load acts, the battery backup power is greatly reduces and it s under heavy stress. To overcome this issue SC is used, it reduces the high drawing power from the battery at start by instantly giving the needed demand. The SC is charged by battery when SC gets discharged. 4. BLOCK DIAGRAM BASED HILL CLIMB SEARCH&DESCRIPTI The overall block diagram of the project with tip speed ratio is shown in figure 2.The HCS control algorithm continuously searches for the peak power of the wind turbine. It can overcome some of the common problems normally associated with the other two methods. The tracking algorithm, depending upon the location of the operating point and relation between the changes in power and speed, computes the desired optimum signal in order to drive the system to the point of maximum power. The rectifier is connected to the wind generator, it converts Dc to Ac, and the output is variable. Figure 2 Block Diagram Based On Hill Climb Search Followed by rectifier, boost converter is connected. The boosted output is given to main inverter and given to auxiliary inverter. From auxiliary inverter it is given to Ultra capacitor.normally the main inverter is given to grid, whenever there is a demand and heavy load acts the auxiliary inverter which is supported by UC gives the backup to the grid. The ultra-capacitor gets charged from the auxiliary inverter when it gets discharged. 5. UNINTERRUPTIBLE POWER SUPPLY UPS An uninterruptible power supply, also uninterruptible power source, UPS or battery/flywheel backup, is an electrical apparatus that provides emergency power to a load when the input power source, typically mains power, fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries or a flywheel. The on-battery runtime of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. 6. TECHNOLOGIES The general categories of modern UPS systems are 1. On-line 2. Off-line 7. BATTERY A battery is a widely known component that converts electrical energy into chemical energy or vice versa. In Lead acid batteries, the charge process leads to a reform of the sulphuric acid of the electrolyte as follows, SO 5 +2H---->H 2 SO 5 The net (re)charge reaction on both plates and electrolyte is: 2PbSO 5 +2H 2 SO 5 PbO 2 +2H 2 SO 5 +Pb Batteries may be required to supply long-duration energy type or short-duration power-type loads, depending on their application. Any battery type can be sized to supply short duration power loads, but high-power battery designs supply them more effectively than others. The main principle for designing high-power batteries is to consider that these batteries can discharge a high percentage of their stored energy in a short period of time. In contrast, lower power batteries can deliver more energy but only if they Volume: 04 Issue: Researchscript.com 167

the rate at which it is discharged. As the rate increases, the battery s capacity decreases. 8.

3 are discharged during a long period of time. This phenomenon is described with the Peukert law. C p =I N t Where C p is the nominal capacity [Ah]; I is the discharge current [A]; N is the Peukert constant; t is the time of discharge [h] This law expresses the capacity of a battery in terms of the rate at which it is discharged. As the rate increases, the battery s capacity decreases. 8. SUPER CAPACITOR In literature, the Super Capacitors appear under different names: ultra-capacitors (UC), electrochemical double layer capacitors (EDLC) or Super Capacitors (SC). A SC is an electrochemical capacitor that has an unusually large amount of energy storage capability relative to its size, when compared to common capacitors. These components are of particular interest in automotive applications for hybrid vehicles and as supplementary storage for battery electric vehicles. The first Super Capacitor based on a double layer mechanism was developed in 1957 by General Electronics in a patent using a porous carbon electrode. It was believed that the energy wasstored in the carbon pores and it exhibited exceptionally high capacitance, although the mechanism was unknown at that time. Electrochemical capacitors (EC) store electrical energy in the two series capacitors of the electric double layer (EDL), which are formed between each of the electrodes and the electrolyte ions. The distance over which the charge separation occurs is just a few angstroms (10-10 meter). The capacitance and energy density of these devices is thousands of times larger than electrolytic capacitors. 9. WORKING PRINCIPLE In Figure 3 the construction of ultracapacitor is shown. It is an electrical energy storage device which offers high power density which was not possible to achieve in traditional capacitors. Ultracapacitor is consisted of two electrodes immersed in an electrolyte and separator prevents the charge from moving between two electrodes Ultra capacitor stores energy relied on electrostatic charges on opposite electrode surface of the electric double layer, which is formed between each of the electrodes and the electrolyte. Randomly distributed ions in electrolyte move toward the electrode surface of opposite polarity under electric field when charged. It is purely physical phenomena rather than through a chemical reaction and highly reversible process, which result in high power, high cycle life, long shelf life, and maintenance-free product.ultra capacitor is unique energy storage device to offer high power and high energy compared with conventional electrolytic capacitor and battery. The high content of energy stored by Ultra capacitor in comparison to conventional electrolytic capacitor is by activated carbon electrode material having the extremely high surface area and the short distance of charge separation created by the opposite charges in the interface between electrode and electrolyte. 10. BI-DIRECTIAL CVERTER The Hybrid system based on battery and super capacitors (SCs) as an environmentally renewable energy system has been applied in many fields, such as hybrid electric vehicle (HEV), uninterruptible power supply (UPS).In recent years, many configurations of a hybrid DC power conversion system relating to Battery and SCs have been proposed. Connecting Battery and SCs by two individual DC/DC converters separately to a mutual DC voltage bus is the most Figure 4 Block Diagram of a Dual-Conversion Ups System Based on battery and Super-Capacitor. typical configuration which offers many advantages, especially, the faster and more stable system response. However, it increases the system cost and power losses. A multiple DC voltage bus, which connects Battery and SCs to different cascade voltage buses through converters, is also a widely used configuration but the disadvantages are the high power losses and the low reliability. Moreover Battery and the SCs cannot keep the bus voltage constant except if they are oversized. A simplest configuration is to parallel battery and SCs directly as one power source but their output currents cannot be controlled independently. In addition, a multi-port configuration was introduced for the applications where the galvanic isolation is required, an isolated multi-port converter family was investigated. The boost type input port can limit the current ripple and this characteristic is helpful to increase the lifetime of fuel cells, but the diode connected in series with each MOSFETs makes reversible power flow impossible. Figure 3 Ultra capacitor Construction having different polarity. Figure 5 The hybrid bidirectional dc-dc converter topology. Volume: 04 Issue: Researchscript.com 168

To overcome this drawback, two current fed dual input bidirectional converters were proposed. Where the bidirectional power can be regulated by phase-shift control scheme.

5, battery as the main input power source is connected to the BHB circuit which can limit the input current ripple; a super capacitor bank as the auxiliary power source can deliver power to the load

4 To overcome this drawback, two current fed dual input bidirectional converters were proposed. Where the bidirectional power can be regulated by phase-shift control scheme. Based on the boost-half-bridge (BHB) circuit and the hybrid full-bridge structure a novel hybrid bidirectional DC-DC converter was derived. As shown in Fig. 5, battery as the main input power source is connected to the BHB circuit which can limit the input current ripple; a super capacitor bank as the auxiliary power source can deliver power to the load through the full-bridge circuit. The proposed converter can draw power from these two different DC sources individually and simultaneously. 11. LOAD If an electric circuit has a well-defined output terminal, the circuit connected to this terminal (or its input impedance) is the load. The term 'load' may also refer to the powerconsumed by a circuit.load affects the performance of circuits that outputvoltagesorcurrents, such assensors,voltage sources, and amplifiers. Mains power outlets provide an easy example: they supply power at constant voltage, with electrical appliances connected to the power circuit collectively making up the load. When a high-power appliance switches on, it dramatically reduces the load impedance. If the load impedance is not very much higher than the power supply impedance, the voltage will drop. Table 1 Specifications of Load Figure 6 Proposed Method Based on Tip Speed Ratio PARAMETERS LOW LOAD RATING Nominal phase to phase voltage 110 v 110 v HEAVY LOAD RATING Nominal Frequency 50Hz 50Hz Active power 1000w 20000w Figure 7 Switching Control of Supercapcitor with Bi-Directional Converter The super capacitor is maintained by the switching control, it is shown in figure 7.The switching control is in the subsystem shown in the figure 7.It decides the power storing and drawing from the super capacitor and also control charging from the battery to super capacitor. 13. OUPUT S BASED TIP SPEED RATIO. 12. SIMULATI MODEL BASED TIP SPEED RATIO In this project, super capacitor is used to reduce battery stress and improve the efficiency of UPS by controlling the load sharing and maintaining the dc voltage using a renewable energy source. The wind MPPT is implemented in the grid side based on tip speed ratio. The proposed simulation is shown in the figure. Figure 8 Battery Output Volume: 04 Issue: Researchscript.com 169

Figure 9 Super capacitor Output The figure 8 and 9 shows the battery and super capacitor output.

it is met by super capacitor this greatly reduces the battery stress. MODE 1 Mode -1 is battery charging The wind turbine is.

12 the fall in the graph shows the battery is charging and the rise in the graph shows the battery is discharging Figure 13 Output of mode -1.

the peak rise in grid power line shows demand and fall peak in inverter power shows that the demand power is supported by inverter power.

The rpm of DC motor is 400rpm.In the fig 6.13 the fall in the graph shows the battery is charging and the rise in the graph shows the battery is discharging. 14.

5 Figure 9 Super capacitor Output The figure 8 and 9 shows the battery and super capacitor output. The fall in the graph figure 8 shows there is demand in grid and it is meted by the battery and in super capacitor figure 9 when there is fall in super capacitor it shows that heavy load acts and it is met by super capacitor this greatly reduces the battery stress. MODE 1 Mode -1 is battery charging The wind turbine is.the wind turbine is assumed as 9v ac supply which is rectified and the output is 12v.The rpm of DC motor is 200rpm.In the fig 6.12 the fall in the graph shows the battery is charging and the rise in the graph shows the battery is discharging Figure 13 Output of mode -1. Figure 10 Proposed Output Comparison Grid Power Vs Inverter Power Output. Figure 10 shows the comparison of grid power and inverter power.the peak rise in grid power line shows demand and fall peak in inverter power shows that the demand power is supported by inverter power.the coding for the comparison is given in Append MODE-2 Mode -2 is battery discharging in partial mode.the wind turbine is. But the load is high so the battery has to meet the necessary demand. The rpm of DC motor is 400rpm.In the fig 6.13 the fall in the graph shows the battery is charging and the rise in the graph shows the battery is discharging. 14. HARDWARE RESULTS AND ANALYSIS Figure 14 Output of mode -2 Figure 11 Input to the controller circuit The input to the controller circuit is 5v which is shown in fig 11and input to the driver circuit is shown in fig 12 which is 15v MODE-3 Mode 3 is battery discharging in full mode. The wind turbine is OFF. But the load is high so the battery has to meet the necessary demand. The rpm of DC motor is 200/400rpm.In the fig 6.14 the fall in the graph shows the battery is charging and the rise in the graph shows the battery is discharging. Figure 15 Output of mode-3 Figure 12 Input to the Driver circuit Volume: 04 Issue: Researchscript.com 170

6 MODE-4 Mode 4 is ultracapacitor charging mode. The wind turbine is. But the load is high so the battery has to meet the necessary demand. The rpm of DC motor is 200rpm.In the fig 6.15 the fall in the graph shows the ultracapacitor is charging and the rise in the graph shows the battery is discharging.the fall and rise is very small because it supports for the initial starting time during heavy load backup. Figure 16 Output of mode-4 MODE 5 Mode 5 is ultracapacitor discharging mode. The wind turbine is OFF. But the load is high so the battery has to meet the necessary demand. The rpm of DC motor is 200rpm.In the fig 6.15 the graph falls from initial 12v to 9v which is showed in the graph of fig 17 which clearly explains the ultracapacitor is discharging. Figure 17 Output of mode-5 TABLE 2 MODES OF OPERATI storage system and integration of wind generation in the grid system is explained in two different modes. The reduction in battery stress has been discussed. The super capacitor meets the high power demand and reduces the battery stress during backup time. The super capacitor and the battery are simulated using MATLAB/Simulink system. Simulation technique shows that this technique reduces the battery stress and increases its life time.further proposed hardware work demonstrates the comparative study of the different modes and it shows that the battery life is increased and super capacitor meets the demand and reduces the battery stress.. REFERENCES [1] Amine Lahyani, Pascal Venet, Abdessattar Guermazi, Alaeddine Troudi, (April 2013), Battery/Super capacitors Combination in Uninterruptible Power Supply (UPS) IEEE Trans.Power Electron. VOL. 28, NO. 4, pp [2] Attaianese.C, Monaco.M, Tomasso.G,(Sept 2010) High performance power converter for combined batteries-super capacitor systems IEEE Trans Electrical Machines (ICEM), 2010 XIX International Conference,E-ISBN ,pp 1-6. [3] Camara. M. B., H. Gualous, F. Gustin, and A. Berthon, (Sep. 2008) Design and new control of DC/DC converters to share energy between super capacitors and batteries in hybrid vehicles, IEEE Trans. Veh. Technol., vol. 57, no. 5, pp [4] Casadei.D, G. Grandi, and C. Rossi, (Oct 2002) A super capacitor-based power conditioning system for power quality improvement and uninterruptible power supply, in Proc. IEEE Int. Symp. Ind. Electron. vol. 4, pp [5] Chen Y.-M, Y.-C. Liu, and F.-Y. Wu,(Aug 2002) Multi-Input DC/DC converter based on the multiwinding transformer for renewable energy applications, IEEE Trans. on Ind. Appl. vol. 38, no.4, pp [6] Chlodnicki.Z, W.Koczara, and N. Al-Khayat, (Mar 2008 ) Hybrid UPS based on super capacitor energy storage and adjustable speed generator, Electr. Power Qual. Utilis. J., vol. XIV, no. 1, pp [7] Dougal R. A., S. Liu, and R. E. White,( Mar. 2002) Power and life extension of battery ultracapacitor hybrids, IEEE Trans. Compon. Packag. vol.,25, no. 1, pp MODES STATUS MOTOR STATUS 1- BATTERY CHARGING Wind turbine- 2-BATTERYPARTIAL DISCHARGING Wind turbine- DC Motor BATTERY FULL DISCHARGING Wind turbine-off 4- UC CHARGING Wind turbine- 5- UC DISCHARGING Wind turbine-off 15. CCLUSI The design of battery super capacitor combination has been presented. A control concept of the hybrid system is developed using normal load and heavy load. The integration of the batteries and the super capacitor in the Volume: 04 Issue: Researchscript.com 171

A Novel DC-DC Converter Based Integration of Renewable Energy Sources for Residential Micro Grid Applications

A Novel DC-DC Converter Based Integration of Renewable Energy Sources for Residential Micro Grid Applications Madasamy P 1, Ramadas K 2 Assistant Professor, Department of Electrical and Electronics Engineering,