FTEEE-16100 Control and Operation of a DC Grid-Based Wind Power Generation System in a Micro grid – IEEE EEE Project 2016-2017
The design of a dc grid-based wind power generation system in a poultry farm. The proposed system allows flexible operation of multiple parallel-connected wind generators by eliminating the need for voltage and frequency synchronization. A model predictive control algorithm that offers better transient response with respect to the changes in the operating conditions is proposed for the control of the inverters. The design concept is verified through various test scenarios to demonstrate the operational capability of the proposed micro grid when it operates connected to and islanded from the distribution grid, and the results obtained are discussed.
Many research works on dc micro grids have been conducted to facilitate the integration of various DERs and energy storage systems. In dc micro grid based wind farm architecture in which each wind energy conversion unit consisting of a matrix converter, a high frequency transformer and a single-phase ac/dc converter is proposed. However, the proposed architecture increases the system complexity as three stages of conversion are required. In a dc micro grid based wind farm architecture in which the WTs are clustered into groups of four with each group connected to a converter is proposed. However, with the proposed architecture, the failure of one converter will result in all four WTs of the same group to be out of service.
The overall configuration of the proposed dc grid based wind power generation system for the poultry farm. The system can operate either connected to or islanded from the distribution grid and consists of four 10 kW permanent magnet synchronous generators (PMSGs) which are driven by the variable speed WTs. The PMSG is considered in this paper because it does not require a dc excitation system that will increase the design complexity of the control hardware. The three-phase output of each PMSG is connected to a three-phase converter, which operates as a rectifier to regulate the dc output voltage of each PMSG to the desired level at the dc grid.
The most significant advantage of the proposed system is that only the voltage at the dc grid has to be controlled for parallel operation of several WGs without the need to synchronize the voltage, frequency and phase, thus allowing the WGs to be turned ON or OFF anytime without causing any disruptions. Many research works on designing the controllers for the control of inverters in a micro grid during grid-connected and islanded operations is conducted. A commonly adopted control scheme which is detailed contains an inner voltage and current loop and an external power loop to regulate the output voltage and the power flow of the inverters.
- System Operation
- System Operation
- DC/AC Inverter Modeling
- AC/DC Converter Modeling
- Numerical simulation analysis
- Report Generation
When the micro grid is operating connected to the distribution grid, the WTs in the micro grid are responsible for providing local power support to the loads, thus reducing the burden of power delivered from the grid. The SB can be controlled to achieve different demand side management functions such as peak shaving and valley filling depending on the time-of-use of electricity and SOC of the SB. During islanded operation where the CBs disconnect the micro grid from the distribution grid, the WTs and the SB are only available sources to supply the load demand.
The micro grid to operate in both grid-connected and islanded modes of operation, a model based controller using MPC is proposed for the control of the inverters. MPC is a model-based controller and adopts a receding horizon approach in which the optimization algorithm will compute a sequence of control actions to minimize the selected objectives for the whole control horizon, but only execute the first control action for the inverter.
DC/AC Inverter Modeling
The two 40 kW three-phase dc/ac inverters which connect the dc grid to the point of common coupling (PCC) are identical, and the single-phase representation of the three-phase dc/ac inverter. To derive a state-space model for the inverter, Kirchhoff’s voltage and current laws are applied to loop i and point x respectively, the grid is set as a large power system, which means that the grid voltage is a stable three-phase sinusoidal voltage. Hence, when operating in the CCM, a three-phase sinusoidal signal can be used directly as the exogenous input. During islanded operation, the inverters will be operated in the voltage control mode (VCM). The voltage of the PCC will be maintained by the inverters when the micro grid is islanded from the grid.
AC/DC Converter Modeling
The effectiveness of the proposed design concept is evaluated under different operating conditions when the micro grid is operating in the grid-connected or islanded mode of operation. The system parameters. The impedances of the distribution line are obtained. In practical implementations, the values of the converter and inverter loss resistance are not precisely known. Therefore, these values have been coarsely estimated. When the micro grid is operating in the grid-connected mode of operation, the proposed wind power generation system will supply power to meet part of the load demand. Under normal operating condition, the total power generated by the PMSGs at the dc grid is converted by inverters 1 and 2 which will share the total power supplied to the loads. When one of the inverters fails to operate and needs to be disconnected from the dc grid, the other inverter is required to handle all the power generated by the PMSGs. In this test case, an analysis on the Micro grid operation when one of the inverters is disconnected from operation is conducted.
Numerical simulation analysis:
When the micro grid operates islanded from the distribution grid, the total generation from the PMSGs will be insufficient to supply for all the load demand. Under this condition, the SB is required to dispatch the necessary power to ensure that the micro grid continues to operate stably. The third case study shows the micro grid operation when it islands from the grid. The micro grid is initially operating in the grid-connected mode. The grid is supplying real power of 40 kW and reactive power of 4 kVAr to the loads for 0 ≤ t < 0.2 s while each inverter is delivering real power of 10 kW and reactive power of 4 kVAr to the loads.
The design of a dc grid based wind power generation system in a micro grid that enables parallel operation of several WGs in a poultry farm has been presented. As compared to conventional wind power generation systems, the proposed micro grid architecture eliminates the need for voltage and frequency synchronization, thus allowing the WGs to be switched on or off with minimal disturbances to the micro grid operation. The design concept has been verified through various test scenarios to demonstrate the operational capability of the proposed micro grid and the simulation results has shown that the proposed design concept is able to offer increased flexibility and reliability to the operation of the micro grid. However, the proposed control design still requires further experimental validation because measurement errors due to inaccuracies of the voltage and current sensors, and modelling errors due to variations in actual system parameters such as distribution line and transformer impedances will affect the performance of the controller in practical implementation.
 M. Czarick and J.Worley, “Wind turbines and tunnel fans,” Poultry Housing
Tips, vol. 22, no. 7, pp. 1–2, Jun. 2010.
 The poultry guide: Environmentally control poultry farm ventilation systems for broiler, layer, breeders and top suppliers. [Online]. Available: http://thepoultryguide.com/poultry-ventilation/
 Livestock and climate change. [Online]. Available: http://www.
 Farm Energy: Energy efficient fans for poultry production. [Online].Available:
 A. Mogstad, M. Molinas, P. Olsen, and R. Nilsen, “A power conversion system for offshore wind parks,” in Proc. 34th IEEE Ind. Electron., 2008, pp. 2106–2112.