19                 ! FREQUENCY CONTROL IN CIGRE LOW VOLTAGE DISTRIBUTION NETWORK WITH SIGNIFICANT AMOUNTS OF INVERTER BASED GENERATORS Ghullam Mustafa Bhutto*, Muhammad Usman Keerio*, Rameez Akbar Talani*, Ehsan Ali Buriro** ABSTRACT Maintaining demand side supply and regulating frequency in power networks are the prime requirements of the modern power systems. The frequency of the power system deviates from its nominal value if there is mismatch between power generation and the consumption. If the active power demand is higher than the active power production in the network, the frequency decreases and vice versa. The increase or the decrease in the frequency can be compensated by balancing the generation and load demands. This is normally done by allocating reserve units or by using inverter based generators such as Battery Energy Storage Devices (BESDs). The main focus of this paper is to control the frequency of the network by providing/absorbing the required/extra amounts of the power by BESDs. The work is done on a simple network and simulations are carried out by using DIgSILENT power factory software version 15.0. The procedure of modeling BES which should operate as Battery Energy Storage equipped Static Compensator (BES@STATCOM) developed in DIgSILENT power factory is also described in this paper. Keywords: Battery Energy Storage Devices (BESDs), Frequency control, Battery Energy Storage equipped Static Compensator (BES(STATCOM, CIGRE network 1. INTRODUCTION It is the prime requirement in power systems that the Load(generation must be corrected within short duration; otherwise it might leads to the power line frequency to deviate from the rated value (e.g., 50 Hz in this study). Large deviations in the frequency of the power network cause the threats to the stability and the security of power systems and might cause permanent damage to the equipments [1], [2]. Due to this reason balancing between generation and load in order to regulate the frequency at the nominal value has gained a vital importance. Several control approaches have been reported in the literature to serve the goal. Some of the power system uses Automatic Generation Control (AGC) technique which issues signals in order to control the reserve units and minimize Area Control Error (ACE), which includes both frequency deviation and unscheduled tie(line power flows [3], [4]. The spinning reserve is also used in order to regulate the frequency. The generators which are used as spinning reserve units automatically increase their outputs when supply is suddenly lost [3]. Furthermore, many generators are equipped with speed governors which adjust their speed depending on the frequency response of the network [5], [6]. The other techniques which are used for this purpose use exciters and Power system stabilizers (PSS) [7]. The problem in such kind of techniques is the time for the switching of the units from off(mode to on(mode. The ESDs are becoming popular for the load(generation balancing in the networks due to their faster response because of the power electronics interfaces as compared to the conventional reserve units such as synchronous generator based reserves. The ESD can store surplus power produced in the grid and can release the energy into the electricity grid in the case of generation deficit. This property of ES systems can smoothen the short term as well as long(term variations in the power caused by the load variations and behaves like power system balancing and reserve units. The main idea of the study proposed here is about the frequency stability in the CIGRE low voltage distribution network (i.e. developed European CIGRE working group experts) as shown in Fig. 1. This is done by matching load(generation balance in the network shown in Fig. 1. The entire study about the frequency stability within the CIGRE network is not performed here but the CIGRE network shown in Fig. 1 is split into a very simple network comprising finite grid (i.e. a synchronous generator with the active power capability of 30 kW), one battery unit and a load. This is done in order to show the detailed procedure about the control of frequency within the power networks and same procedure is proposed for the frequency stability within the CIGRE low voltage network. The load(generation matching in this paper is done by using 30 kWh BES unit which is modeled as BES(STATCOM for this study. The regulation of the network frequency by using ESDs has already been implemented in several power systems and is available in the literatures. * Department of Electrical Engineering, ** Department of Electronics Engineering, Quaid(E(Awam University of Engineering Sciences and Technology, Nawabshah