Current Controller Based Power Management Strategy for Interfacing DG Units to Micro Grid (original) (raw)
Related papers
2010
The ever increasing energy demand, the necessity of a reduction in costs and higher reliability requirements are driving the present scenario towards Distributed Generation (DG). The DG has been considered as a promising alternative for the coordinated and flexible expansion of the present energy distribution system with reduced cost and improved reliability . In particular, the small DG systems, typically from 1KW to 10 MW and located near to the loads, are gaining popularity due to their higher operating efficiencies and lower emission levels as provider of electrical energy to the consumers. These DG systems are powered by one or more microsources such as: fuel cells, photovoltaic cells, batteries, wind-turbine, micro-turbines etc. A recent evolution resulting by the diffusion of the DG systems is emerged with the concept of Microgrid, which consists in a cluster of loads and paralleled DG systems operating as a single power system that provides power to its local area . A Microgrid is a systematic organization of DG systems and therefore it has larger capacity and more control flexibility to fulfil system reliability and power quality requirements, in addition to all the inherent advantages of a single DG system. The above characteristics can be obtained thanks to the use of grid-connected inverters able to quickly manage power generated by the microsources and to generate reactive power near loads, allowing losses reduction. Therefore, high performance control algorithms for power flows control and voltage regulation are required . These algorithms should preferably have no communication links between the paralleled DG systems, which can be located far apart; thus, the control algorithms of each individual DG system should be based on feedback variables that can be measured locally and moreover, they have to ensure a safety operation of the Microgrid avoiding instability problems, which can occur especially when many DG systems are located in a same area. A good solution for the aforementioned problems can be obtained by the application proposed in this chapter. It is based on the use of a control strategy for grid-connected inverters able to dynamically change the energetic contribution of the microsources, that so adapts oneself to variations of the grid characteristics and contributes to the power management of the Microgrid. The control strategy is developed so as to combine the
Current Control Strategy for ParallelOperation of Inverters Based On Micro grids
International Journal of Advanced Research in Electrical, Electronics and Instrumentation Energy, 2014
In this paper, a new control method for the parallel operation of inverters operating based on LV micro grids is proposed. This new approach can be applied to the inverter-based micro grids using renewable energy sources where communication wires are not reliable due to the remote locations. The proposed strategy is based on the advanced droop control technique where only the locally measured values are used as feedback. Unfortunately, the trade-off has to be made between the transient response and the power sharing accuracy for the conventional voltage and frequency droop control method. Moreover, the output and line impedance of the inverter presents a great impact on the power sharing accuracy. This paper explores the resistive output impedance and line impedance of the parallel connected inverters in island micro grid. The active and reactive output current is used as the control variables so as to limit the current spikes during the initial and transient states. Additionally, t...
Control of Parallel Inverter-Interfaced Distributed Energy Resources
Due to the rapid increase in global energy consumption and the diminishing of fossil fuels, the customer demand for new generation capacities and efficient energy production, delivery and utilization keeps rising. Utilizing distributed generation, renewable energy and energy storage can potentially solve such problems as energy shortage and global warming. A promising structure to interconnect these distributed energy resources is the microgrid paradigm. A microgrid comprises a variety of inverter-interfaced distributed energy resources such as fuel cells, photovoltaic arrays, microturbines, wind-turbine generators, energy storage devices (i.e., batteries, supercapacitors, etc.) and controllable loads, offering considerable control flexibility. These systems can be connected with the power grid. They can be also operated isolated from the main grid in case of disturbances or faults, which are controlled by the microgrid central controller. The key point is to control the parallel inverters so that they can work well to achieve high performances in the microgrid. This paper presents a new control method for power sharing among the parallel inverter-interfaced distributed energy resources. The proposed control method is tested in four typical scenarios: (1) three inverters switch from gridconnected mode to isolated mode; (1) three inverters switch from isolated mode to grid-connected mode; (3) three-inverter operation switched to two inverter operation in the isolated mode; and (4) two inverter operation switches to three inverter operation in the isolated mode. Simulation results suggest that this control method can make the parallel-connected inverters work well and will increase the microgrid stability.
PQ Control Based Grid Connected DG Systems
Distributed generation (DG) generally refer to small scale electric power generators produce electricity that is bound to an electric distribution system. Distributed generation systems such as photovoltaic (PV) or wind energy systems are parts of the future smart grids. By applying intelligent techniques these future grids change as smarter grids. During the past few years electrical energy consumption to the investment is increased when compared to cost on transmission and distribution resulting in compromised reliability and high energy costs. So there is need to change from conventional grid to smart grid. Micro grids consist of small power sources called distributed generation system. Many distributed generation systems such as photovoltaic systems are grid interfaced through power electronic voltage source inverters. In this paper a boost inverter technique is explained and distributed generation sources such as PV and fuel cell are connected in series with the help of PQ controller technique the above system is evaluated.
Voltage Support and Reactive Power Control in Micro-grid using DG
Distribution Generators(DGs) are the renewable energy resource which can be connected to the grid. When it is connected to the grid it should be operated with controlled voltage and reactive power control. And in autonomous mode(i.e disconnected mode) it should operate in backup generation mode. These DGs are connected towards the micro grid operation. The proposed control system facilitates flexible and robust DG operational characteristics such as active/reactive power (PQ) or active power/voltage (PV) bus operation in the grid- connected mode, regulated power control in autonomous micro-grid mode, smooth transition between autonomous mode and PV or PQ grid connected modes and vice versa, reduced voltage distortion under heavily nonlinear loading conditions, and robust control performance under islanding detection delays. Evaluation results are presented to demonstrate the flexibility and effectiveness of the proposed controller.
Grid and Islanded Operation of a Distribution Generation Inverters in a Microgrid
This paper presents the design of a micro grid. The proposed micro grid consists of a photo voltaic array which represents the main generation unit in the microgrid and proton exchange membrane fuel cell is supplement the variable power generated by the photovoltaic array. a lithium ion battery is included in the microgrid for reduce the burden of the power generated by the microgrid during the peak period. The all those different dg’s units is coordinate to operate the energy management systems during the grid connected operation. The overall system improves the power quality and reliability of the power distribution system that the microgrid is connected to. The control design employs the output regulation (OR) theory. Kalman filters used to extract the harmonic component of the distorted source voltage and load current, and estimate the state observer gain and frequency tracking .The simulation studies verified through different test case.
IEEE Transactions on Power Electronics, 2010
This paper presents a pseudo-droop control structure integrated within a microgrid system through Distributed Power Generation modules capable to function in off-grid islanded, gensetconnected and grid-connected modes of operation. System efficiency has an important role in order to harvest the maximum available renewable energy from DC or AC sources whilst providing power backup capability. A control strategy is proposed in off grid islanded mode method based on the microgrid line frequency control as agent of communication for energy control between the DPG modules. A critical case is where the AC load demand could be lower than the available power from the photovoltaic solar array where the battery bank can be overcharged with unrecoverable damage consequences. The DPG voltage forming module controls the battery charge algorithm with a frequency generator function and the DPG current source module controls its output current through a frequency detection function. The physical installation between DPG modules is independent since no additional communication wiring is needed between power modules which represent another integration advantage within the microgrid type application. Index Terms-Distributed Power Generation (DPG), hybrid converter, PV inverter, PV converter, microgrid, islanded mode, grid-connected mode, genset-connected mode.
Smart interconnection of a PV/wind DG micro grid with the utility distribution network
2012
Future electric grids are becoming smarter by applying intelligent control techniques. Distributed Generation (DG) systems such as Photovoltaic (PV) and wind energy systems are essential parts of the future smart grids. In this paper, a smart interconnection control strategy is proposed for a grid connected PV/fixed speed wind driven micro grid. In case of industrial inductive loads, the generation of active power from the micro grid causes power factor decrease at the Point of Common Coupling (PCC) with the main grid. With the additional reactive power needs of the squirrel cage induction generator of the windsystem, the micro grid itself becomes a VAR burden.
Control of grid connected PV cell distributed generation systems
TENCON 2008 - 2008 IEEE Region 10 Conference, 2008
This paper presents modeling, controller design, and simulation study of a grid connected Photovoltaic (GCPV) distributed generation (DG) system. The overall configuration of the grid connected photovoltaic DG system is given, dynamic models for the GCPV power plant and its power electronic interfacing are described, and controller design methodologies for the control of power flow from the photovoltaic cell power plant to the utility grid are presented. A MATLAB/Simulink based simulation model is developed for the GCPV DG system by combining the individual component models and the controllers design. Simulation results are presented to show the overall system performance.
Current droop control of parallel inverters in an autonomous microgrid
The load sharing analysis in an autonomous microgrid (MG) with renewable energy sources (RES) is an important issue. The inverter is employed to integrate a distributed generation system to the utility grid, or to run the load available in the microgrid is an essential concept in the autonomous microgrid. In that situation, there is a growing demand in developing a proper control strategy to draw current with fewer distortion from the inverter, and there is a condition to connect two or more sources in parallel for satisfying the load requirements (sharing of loads). To connect two or more DG units to the load, there is a requirement of paralleling the inverters. This paper presents the development of a hybrid controller for load sharing from different DGs with the help of a parallel-connected inverters interface. The proposed systems help improve the quality of power, reliability, and economical operation of the autonomous microgrid.