Zdenek Muller

Evaluation of IRP, FBD, SD, and generalized non-active power theories

Most of modern power equipments connected to the grid must be viewed as non-linear loads producing voltage and current harmonics, subharmonics, and quasi-periodic and stochastic disturbances even under normal operation conditions. An analysis and comparison of usage of different power theories for the parallel compensation of periodic and non-periodic disturbances is presented in the paper. Different reference voltage vectors and averaging time intervals are applied in the power theories.

Comparative review of reactive power compensation technologies

The quality of electrical power in a network is a major concern which has to be examined with caution in order to achieve a reliable electrical power system network. Reactive power compensation is a means for realising the goal of a qualitative and reliable electrical power system. This paper made a comparative review of reactive power compensation technologies; the devices reviewed include Synchronous Condenser, Static Var Compensator (SVC) and Static Synchronous Compensator (STATCOM). These technologies were defined, critically examined and compared, the most promising technology is recommended for the realisation of an effective, efficient, sustainable, qualitative and reliable electrical power network.

FACTS devices influence on power losses in transmission systems

Since there are still higher efforts for transmission systems equipment utilization, more control mechanisms and devices are integrated to the systems and their dispatch centers and these will be also in future. FACTS devices purpose is preferably to maintain voltage levels and to control active and reactive power flows. Their implementation in the grid can result from the necessity to improve the system capabilities in a long-term period or to solve some extraordinary states. The paper deals with the implementation of shunt and series FACTS devices into electrical transmission systems and their influence on active power losses. There are provided comparison analyses of how different FACTS types have a potential to changes power losses in the system either in a negative or in a positive way. There are explained basic principles and the results are presented on the IEEE/CIGRE transmission system model.

Synchronous phasors monitoring system application possibilities

The paper deals with some tasks of advanced methods to achieve security and reliability of transmission power systems. There are discussed advanced principles and techniques in monitoring systems. The paper main part is devoted to possible applications of PMUs (Phasor Measurement Unit) and their integration into WAMPaC systems (Wide Area Monitoring, Protection and Control). Significant transmission system states were analyzed in several case studies. PMUs utilization for voltage monitoring is demonstrated for three cases - standard system state, high-load state and islanding. Here the attention is paid to the possibilities of power system observability improvement using measuring chain error elimination. Other possible applications in transmission systems include ampacity determination of transmission corridors, the calculation of line electrical parameters using synchrophasor measurement, state estimation issues and power system stability. The power system model was established for methods and algorithms verification purposes. The appropriate algorithms and their parameters were found using simulation outputs to create the local automatics, e.g. Automatic Power System Stabilizer (PSS).

Using renewable MV wind energy resource to supply reactive power in MV distribution network

This paper deals with the use of Medium Voltage (MV) renewable wind energy source to optimize reactive power in a distribution network, it describes the increase of power factor when the reactive power is controlled at a wind farm increase in power factor allows improvement in the stability of distribution networks, and the increase in power factor is used as new methodology to reduce power losses, Matlab/Simulink program is used to show the results of the analysis.

Advantageous positioning of wind turbine generating system in MV distribution network

This paper presents a new method for achieving voltage stability and reduction of power losses with renewable wind turbine generating system (WTGS) installed at different position on a Medium Voltage (MV) distribution system. The proposed network is a three-phase system consisting of 0.4 kV low voltage (LV) feeder with an active power (P) of 8 MW and a negative VAR (Qc) of 0.5 MV AR. And a 20 kV MV feeder with an active power (P) of 22 MW and a negative VAR (Qc) of 1.5 MV AR. The 0.4 kV and 20 kV feeders has varying positive VAR values of 2, 2.25, 2.5 and 6, 6.5, 7 MVARs respectively. Three sets of datas were observed; data 1, 2, and 3, the feeders are connected to a 20 kV MV distribution network, which is then linked to a 20 kV substation. Thereafter, a 20 kV MV renewable WTGS energy source with IGBT converters is integrated to the network for effective reactive power compensation. Three different Cases have been analyzed; First is the case with the proposed power system network analyzed without any WTGS attached to the network, in other words when the WTGS is switched off (this is designated as Case 1). Second is the situation with the WTGS positioned at the terminal end of the 20 kV MV distribution network (point 1, which is designated as Case 2) and Third is the situation when the position of the wind energy source is changed and stationed at the beginning of the terminal of the 20 kV MV power line (point 2, which is designated as Case 3). Matlab/Simulink software is used for the simulation of the system model. Simulation results for each of the case studies is analyzed and it is observed that research findings for Case 2 is more efficient in achieving improved voltage stability and power losses reduction in medium voltage electric-power distribution network.

The reliability of the system with wind power generation

Electricity supply is a fundamental need of a modern society. A crucial property of electricity supply - reliability, is achieved by keeping a power system in a secure state most of the time. A secure state means that the risk of a disturbance to spread further and endanger the system integrity, resulting into supply interruption, is minimal. Large wind power integration can also lead to problems on the voltage control and power quality at large. Voltage control when wind turbines are used can usually be achieved by changing the amount of reactive power compensation (by shunt capacitors installation). The lack of control on the active and reactive powers can disturb the voltage on the Point of Common Coupling (PCC).

STATCOM effect on voltage stability in Ghanaian electrical grid

This paper deals with using STATCOM for voltage stability purposes which is analyzed on the Ghanaian power system development. Preliminary studies have shown that the northern sector is vulnerable to voltage instability which has led to the proposed installation of STATCOM in a key substation Tamale. It is therefore necessary to assess the performance of the device when put in operation. Comparison had therefore been made between the use of STATCOM and a fixed compensator. Line and generator contingencies as well as small signal disturbances analysis have been carried out. Voltage stability is improved with the installation of STATCOM but do not affect the interconnection between Ghana and Burkina Faso. Further evaluation focused on the inter-tie is proposed.

Method of Calculating the Correction Factors for Cable Dimensioning in Smart Grids

One of the main causes of overloading electrical equipment by currents of higher harmonics is the great increasing of a number of non-linear electricity power consumers. Non-sinusoidal voltages and currents affect the operation of electrical equipment, reducing its lifetime, increases the voltage and power losses in the network, reducing its capacity. There are standards that respects emissions amount of higher harmonics current that cannot provide interference limit for a safe level in power grid. The article presents a method for determining a correction factor to the long-term allowable current of the cable, which allows for this influence. Using mathematical models in the software Elcut, it was described thermal processes in the cable in case the flow of non-sinusoidal current. Developed in the article theoretical principles, methods, mathematical models allow us to calculate the correction factor to account for the effect of higher harmonics in the current spectrum for network equipment in any type of non-linear load.

Optimal location of the synchronous condenser in electric-power system networks

In this paper, authors focus on the use of the synchronous condenser device for voltage stability and power flow control on a three-phase 33 kV Medium Voltage (MV) electric-power system network. Matlab/Simulink is used for the simulation of the proposed system model. To test the validity of the system, measured and calculated power factor values were obtained. Two scenarios were studied; Firstly, is the scenario with the synchronous condenser located at the terminal end of the 33 kV MV network (position 1). And secondly, is the scenario with the synchronous condenser placed at the beginning of the 33 kV MV power Line (position 2). Simulation results obtained from the study are compared in order to determine the most appropriate location for situating the synchronous condenser device. It is observed that the locations of the synchronous condenser equipment have different impacts on the electric-power system network. However, the proposed study of the simulation model base on the location of the synchronous condenser at the terminal end of the 33 kV MV electric-power system network (position 1) demonstrate a more effective and suitable scheme of the electric-power network concerning issues of voltage stability and power flow control.