ISSN 2348–2370 Vol.07,Issue.11, August-2015, Pages:2091-2098 www.ijatir.org An Ultra capacitor Integrated Power Conditioner for Intermittency Smoothing and Improving Power Quality of Distribution Grid 1 2 3 K. PRIYANKA , JOHN ARUN KUMAR , DR. J. BAGWAN REDDY 1PG Scholar, Dept of EPE, Bharat Institute of Engineering and Technology, Rangareddy (Dt), Telangana, India, E-mail: [email protected]. 2Associate Professor, Dept of EEE, Bharat Institute of Engineering and Technology, Rangareddy (Dt), Telangana, India. 3HOD, Dept of EEE, Bharat Institute of Engineering and Technology, Rangareddy (Dt), Telangana, India, E-mail: [email protected]. Abstract: Penetration of various types of Distributed power quality of the distribution grid by being able to provide Energy Resources (DERs) like solar, wind, and Plug-in sag, swell, and harmonic current compensation. In this paper, Hybrid Electric Vehicles (PHEVs) onto the distribution energy storage integration into the power conditioner topology grid is on the rise. There is a corresponding increase in is being proposed, which will allow the integrated system to power quality problems and intermittencies on the provide additional functionality. With the increase in distribution grid. In order to reduce the intermittencies and penetration of the Distribution Energy Resources (DERs) like improve the power quality of the distribution grid, an Ultra wind, solar, and Plug-in Hybrid Electric vehicles (PHEVs), Capacitor (UCAP) integrated power conditioner is there is a corresponding increase in the power quality proposed in this paper. UCAP integration gives the power problems and intermittencies on the distribution grid in the conditioner active power capability, which is useful in seconds to minutes time scale [5]. Energy storage integration tackling the grid intermittencies and in improving the with DERs is a potential solution, which will increase the voltage sag and As well compensation. UCAPs have low reliability of the DERs by reducing the intermittencies and energy density, high-power density, and fast also aid in tackling some of the power quality problems on the charge/discharge rates, which are all ideal characteristics distribution grid [5]–[8]. Applications where energy storage for meeting high-power low-energy events like grid integration will improve the functionality are being identified, intermittencies, sags/swells. In this paper, UCAP is and efforts are being made to make energy storage integration integrated into dc-link of the power conditioner through a commercially viable on a large scale [9],[10]. Smoothing of bidirectional dc–dc converter that helps in providing a stiff DERs is one application where energy storage integration and dc-link voltage. The integration helps in providing optimal control play an important role[11]–[17]. In [11], super active/reactive power support, intermittency smoothing, capacitor and flow battery hybrid energy storage system are and sag/swell compensation. Design and control of both integrated into the wind turbine generator to provide wind the dc–ac inverters and the dc–dc converter are discussed. power smoothing, and the system is tested using a real-time The simulation model of the overall system is developed simulator. and compared with the experimental hardware setup. In [12], super capacitor is used as an auxiliary energy Keywords: Distributed Energy Resources (DERs), storage for PhotoVoltaic (PV)/fuel cell, and a model-based PhotoVoltaic (PV), Plug-in Hybrid Electric Vehicles controller is developed for providing optimal control. In [13], (PHEVs). a battery energy storage system based control to mitigate I. INTRODUCTION wind/PV fluctuations is proposed. In [14], multi objective Power quality is major cause of concern in the industry, optimization method to integrate battery storage for improving and it is important to maintain good power quality on the PV integration into the distribution grid is proposed. In [15], a grid. Therefore, there is renewed interest in power quality theoretical analysis is performed to determine the upper and products like the Dynamic Voltage Restorer (DVR) and lower bounds of the battery size for grid-connected PV Active power Filter (APF). DVR prevents sensitive loads systems. In [16], a rule-based control is proposed to optimize from experiencing voltage sags/swells [1], [2], and APF the battery discharge while dispatching intermittent renewable prevents the grid from supplying non sinusoidal currents resources. In [17], optimal sizing of a zinc bromine-based when the load is nonlinear [3]. The concept of integrating energy storage system for reducing the intermittencies in wind the DVR and APF through a back–back inverter topology power is proposed. It is clear from the literature that was first introduced in [4] and the topology was named as renewable intermittency smoothing is one application that Unified Power Quality Conditioner (UPQC). The design requires active power support from energy storage in the goal of the traditional UPQC was limited to improve the seconds to minutes time scale [10]. Reactive power support is Copyright @ 2015 IJATIR. All rights reserved. K. PRIYANKA, JOHN ARUN KUMAR, DR. J. BAGWAN REDDY another application which is gaining wide recognition with system with active power capability1) to compensate proposals for reactive power pricing. Voltage sag and temporary voltage sag (0.1–0.9 p.u.) and As well (1.1–1.2 swells are power quality problems on distribution grid that p.u.), which last from 3 s to 1 min [18]; and 2)to provide have to be mitigated. sag/ swell compensation needs active active/reactive support and renewable intermittency power support from the energy storage in the milliseconds smoothing, which is in the seconds to minutes time scale. to 1 min duration [11]. All the above functionalities can be realized by integrating energy storage into the grid through a power conditioner topology as shown in Fig.1. Of all the rechargeable energy storage technologies superconducting magnet energy storage (SMES), flywheel energy storage system (FESS), battery energy storage system (BESS),and ultra capacitors (UCAPs), UCAPs are ideal for providing active power support for events on the distribution grid which require active power support in the seconds to minutes timescale like voltage sags/swells, active/reactive power support, and renewable intermittency smoothing [7]. Fig.2. Model of power conditioner with UCAP energy storage. II. CONTROLLER IMPLEMENTATION The series inverter controller implementation is based on the in-phase compensation method that requires PLL for estimating θ, and this has been implemented using the fictitious power method described in [4]. Based on the estimated θ and the line–line source, voltages Vab, Vbc, Vca(which are\ available for this delta-sourced system) are transformed into the d–q domain and the line–neutral Fig. 1.One-line diagram of power conditioner with components of the source voltage V , V , and V which are UCAP energy storage. sa sb sc not available can then be estimated using In this paper, UCAP-based energy storage integration through a power conditioner into the distribution grid is proposed, and the following application areas are addressed. (1) Integration of the UCAP with power conditioner system gives the system active power capability. Active power capability is necessary for independently (2) compensating voltage sags/swells and to provide active/reactive power support and intermittency smoothing to the grid. Experimental validation of the UCAP, dc–dc (3) These voltages are normalized to unit sine waves using converter, inverter their interface, and control. line–neutral system voltage of 120 V as reference and Development of inverter and dc–dc converter controls rms compared with unit sine waves in-phase with actual system to provide sag/swell compensation and active/reactive voltages Vs from (2) to find the injected voltage references support to the distribution grid. V necessary to maintain a constant voltage at the load Hardware integration and performance validation of ref terminals, where m is the modulation index, which is 0.45for the integrated UCAP-PC system. dc–dc converter is this case. Therefore, whenever there is a voltage sag ors well shown in Fig. 2. Both the inverter systems consist of on the source side, a corresponding voltage Vinj2 is injected IGBT module, its gate-driver, LC filter, and an in-phase by the DVR and UCAP system to negate the effect isolation transformer. The dc-link voltage V is dc and retain a constant voltage VL at the load end. The actual regulated at 260 V for optimum voltage and current active and reactive power supplied by the series inverter can compensation of the converter and the line–line be computed using (3) from the rms values of injected voltage voltage V is 208 V. The goal of this project is to ab Vinj2a and load current ILa and ϕ is the phase difference provide the integrated power conditioner and UCAP between the two waveforms International Journal of Advanced Technology and Innovative Research Volume.07, IssueNo.11, August-2015, Pages: 2091-2098 An Ultra capacitor Integrated Power Conditioner for Intermittency Smoothing and Improving Power Quality of Distribution Grid (4) (5) The shunt inverter controller implementation is based on the id –iq method, which is modified to provide active and reactive power compensation, such that id controls the reactive power and iq controls the active power. Therefore, based on the references for active and reactive powers Pref and Q ref, the reference currents iqref and idref in d–q domain Fig. 3. Controller block diagram for DVR and APF. can be calculated using (4), where vsq is the system voltage in q-domain and the reference currents are calculated using (5). The complete inverter control algorithm is B. Bidirectional DC–DC Converter and Controller implemented in the DSP TMS320F28335, which has a A bidirectional dc–dc converter is required as an interface clock frequency of150 MHz, an inbuilt A/D module, PWM between the UCAP and the dc-link, since the UCAP voltage module, and real time emulation, which are all ideal for varies with the amount of energy discharged, while the dc-link this application.