DC Power Flow Analysis Research Articles

Optimal Management of Seasonal Pumped Hydro Storage System for Peak Shaving

Power demand varies on a daily and seasonal basis. Responding to changing demands over time is challenging for energy suppliers as it causes expensive power plants to operate in high-demand seasons, usually summer, increasing the cost of electricity. Peak load shaving makes the load curve flatten by reducing the peak load and shifting it to times of lower demand, hence reducing the operation of expensive power plants. Hence, there is a need for large-scale and long-term ESS to store energy in the time of low-demand seasons for future utilization in the highest-demand ones. In this work, an energy management system (EMS) is developed to optimally manage a grid-connected pumped hydro storage (PHS) for peak shaving. The proposed model incorporates a dynamic economic dispatch (DED) over a study period of one year; hence, a DC power flow analysis considering transmission constraints is utilized to ensure a fast load flow estimation and a manageable simulation time. The framework can be adopted to assess the long-term profitability of PHS-utilizing GAMS as an optimization tool. Further, to draw conclusions that would suit the characteristics of the demand pattern. This analysis is essential to motivate the construction of new seasonal PHS plants due to the high construction costs they are identified with, especially in geographical areas where this technology is not yet considered or is hard to construct. The simulation results demonstrate that integrating 1500 MWh PHS reduced the operation of expensive thermal units by 1224 MWh annually. Further, a reduction in operation costs was recorded after integrating a PHS unit that ranged from 2.6 M to 22 M USD/year, depending on the storage capacity.

DC RAILWAY POWER FLOW ANALYSIS FOR ADDIS ABABA LIGHT RAIL TRANSIT USING NEWTON RAPHSON METHOD

This paper uses Newton–Raphson method for DC power flow analysis of the Addis Ababa light Rail Transit (AALRT). The study focuses onthe line section from Menilik II square station up to Lideta station. First the tractive effort required by the trains for different scenarios such as train movement in a straight line, a curved line, and a line with gradient is computed as the chosen line section contains all these scenarios. Then the total input power will be calculated using computed tractive effort obtained for each scenario and using other input parameters obtained from AALRT, and different papers. The input power for the different loads is computed, and the input power is used to analyse the bus voltage for different loads and train positions. Newton Raphson Method is used to solve the DC Power bus problem assuming that the train requires constant power while moving between two feeding stations. Even if using the rail as the return conductor for DC traction systems has economic advantages, it has some limitations like the rail potential and stray current. A rail potential study is carried out and conclusions are drawn. The result shows that the maximum voltage drop was 0.1 p.u and the train power consumption increases by 136.73 kW as the train takes a gradient of 3.92% and keep increasing again by 29.17kw with a curve resistance (100 meters). The Rail potential moves from 6.0139V to 29.85V proportionally with the variation of the total ground resistance.

LP based solution for Security Constrained Optimal Power Flow including Power Routers

Power Routers offers many benefits to the power system, it helps in improving the existing transmission asset utilization. Security Constrained Optimal Power Flow (SCOPF) is becoming more important in the electrical power system especially in the present deregulated environment. This paper focuses on completely linearizing the complex non-linear SCOPF problem. The objective function is linearized using Piecewise linearization technique and the constraints are framed using linear sensitivity factors. A formal extension is made to the traditional SCOPF by including power router control in the post contingency time frame. DC power flow analysis is used to calculate the real power flow in the lines.Thus, in this paper, further minimization of cost is achieved by using Power Router control and it is compared with the conventional SCOPF.

Study of multi‐objective optimal power flow of AC–DC hybrid system with DCpower flow controller

The DC power flow controller (DCPFC) is a hotspot in DC power flow analysis and control field, which can effectively improve the power flow control degree of DC power grid. The DCPFC is usually installed at the DC bus of the hub converter station. Its power flow control function is an effective complement to the power flow control of the converter station. Therefore, it is necessary to coordinate the DCPFC and the converter station. This paper adds the network loss, static voltage stability index and voltage offset into the objective function of the optimal power flow. The optimisation model of multi-objective power flow of AC–DC hybrid system with DCPFC is established. The converter station and the DCPFC cooperate with each other to control the AC–DC system flow, and realise the coordinated control of the converter station and the DCPFC to achieve minimal loss of network, static voltage stability margin maximisation, and the use of coordinated control of the control system with economic benefits, easier scheduling and so on. Using simulation software to optimise the power flow of the hybrid system, a five-terminal hybrid system is taken as an example to verify the effectiveness of the proposed method.

DC power flow analysis incorporating interval input data and network parameters through the optimizing-scenarios method

DC power flow analysis is based on a linear approximation model for AC power flow equations, and represents an efficient approach for acquiring the bus angles and active transmission power of a power grid. However, the input data and network parameters of the power grid are uncertain due to numerous internal and external factors. Therefore, the DC power flow model should be considered as an uncertain problem, which makes deterministic DC power flow analysis methods unworkable. The present work overcomes this problem by regarding uncertain input data and network parameters as interval values, respectively, and establishes the interval DC power flow (IDCPF) models considering interval input data only (denoted as IDCPF01), and IDCPF model including both interval input data and network parameters (denoted as IDCPF02). Analyses based on the IDCPF models seek to obtain conservative ranges of bus angles and active transmission power flow, which can be employed by dispatchers to develop strategies for ensuring the operational security of the power system. The optimizing-scenarios method (OSM) is employed here to solve the IDCPF models. In addition, it is proven that the lower (or upper) bounds of the bus angles of the IDCPF01 model are simultaneously obtained when the injected power is set as its lower (or upper) interval bounds. This fact greatly improves the efficiency of the OSM for solving the IDCPF models. The results obtained by the proposed method are compared with those obtained by Monte Carlo simulation, the AA-based method, and the interval AC power flow method. The overall simulation results demonstrate the effectiveness and robustness of the proposed method.

Grid Structural Characteristics as Validation Criteria for Synthetic Networks

This paper presents a methodology and set of validation criteria for the systematic creation of synthetic power system test cases. The synthesized grids do not correspond to any real grid and are, thus, free from confidentiality requirements. The cases are built to match statistical characteristics found in actual power grids. First, substations are geographically placed on a selected territory, synthesized from public information about the underlying population and generation plants. A clustering technique is employed, which ensures the synthetic substations meet realistic proportions of load and generation, among other constraints. Next, a network of transmission lines is added. This paper describes several structural statistics to be used in characterizing real power system networks, including connectivity, Delaunay triangulation overlap, dc power flow analysis, and line intersection rate. The paper presents a methodology to generate synthetic line topologies with realistic parameters that satisfy these criteria. Then, the test cases can be augmented with additional complexities to build large, realistic cases. The methodology is illustrated in building a 2000 bus public test case that meets the criteria specified.

Development of Voltage Regulation Plan by Composing Subsystem with the SFES for DC On-line Electric Vehicle

The study of the application process of the relatively small size ‘Superconducting Flywheel Energy Storage (SFES)’ system is conducted to regulate voltage fluctuation of the DC On-Line Electric Vehicle (OLEV) system, which is designed by using DC power system network. It is recommended to construct the power conversion system nearby the substation because the charging system is under the low voltage. But as the system is usually built around urban area and it makes hard to construct the subsystems at every station, voltage drop can occur in power supply inverter that is some distance from the substation. As the alternative of this issue, DC distribution system is recently introduced and has possibility to solve the above issue. In this paper, SFES is introduced to solve the voltage drop under the low voltage distribution system by using the concept of the proposed DC OLEV which results in building the longer distance power supply system. The simulation to design the SFES by using DC power flow analysis is carried out and it is verified in this paper.

TEACHING UNDERGRADUATE POWER SYSTEM COURSES WITH THE USE OF SIEMENS PTI PSS/E-UNIVERSITY SIMULATION SOFTWARE

This paper summarizes the experience in using Siemens PSSE-University power system simulation software as a teaching aid to introduce basic power system concepts to engineering technology students at the undergraduate level. Topics to be discussed and demonstrated in this paper include AC and DC power flow analysis, power system transient stability analysis, reactive power and voltage control, as well as short circuit analysis. For each of the topics presented above, the paper will provide (i) the theoretical background, (ii) a numerical example solvable by hand-calculations, and (iii) the corresponding solution obtained from running PSSE- University. The paper will also provide the perspectives of the instructor on using PSSE as a teaching tool and the perspectives of the students on using PSSE as a learning tool.

Sensitivity Based Detennination of Suitable Locations for Controlled Series Compensation for Enhancement of Steady State Stability in a Large Power System

A procedure for determining the optimum location for installing a Controlled Series Compensation CSC (novel FACTS device) in a power system to provide the most effective damping is investigated DC powerflow analysis and Eigenvalue analysis are used to determine the sensitivities for evaluating the effectiveness of CSC control at a particular location . Computer simulations on a simple system and an Indian system is used to demonstrate the screening procedure.