Cascaded multilevel inverters are popular in fields such as oil and gas, power supply installations, and
power quality devices. While there are many advantages of the cascaded multilevel inverter, its main
disadvantage is the need for large numbers of multiple dc sources. In order to reduce total harmonics
distortion (THD) of the output voltage waveform, the amount of output voltage level must be increased,
hence the higher number of dc sources. This essentially complicated the inverter design, as most converter
transform only one voltage source to another. In this paper a cascaded multilevel inverter topology with a
single dc source is discussed. The topology is based on capacitors instead of cells as the multiple voltage
sources. The cascaded multilevel inverter topology validity and functionality is verified by the Matlab
Simulink simulation of a 100W and 1kW aircraft single phase 41-level inverter.
One of the concerns in power system preventive control and security assessment is to find the point where the voltage and frequency collapse and when the system forces a severe disturbance. Identifying the weakest bus in a power system is an essential aspect of planning, optimising and post-event analysing procedures. This paper proposes an approach to identify the weakest bus from the frequency security viewpoint. The transient frequency deviation index for the individual buses is used as the weakest bus identification as well as a frequency security indicator. This approach will help to determine the bus with the worst deviation, which helps to analyse the system disturbance, takes proper control action to prevent frequency failure, and most importantly, observes consumer frequency. The approach is applied to the WSCC 9 bus test system to show the feasibility of the method.
This paper proposes a new formulation for the multi-objective optimal power flow (MOOPF) problem for meshed power networks considering distributed generation. An efficacious multi-objective fuzzy linear programming optimization (MFLP) algorithm is proposed to solve the aforementioned problem with and without considering the distributed generation (DG) effect. A variant combination of objectives is considered for simultaneous optimization, including power loss, voltage stability, and shunt capacitors MVAR reserve. Fuzzy membership functions for these objectives are designed with extreme targets, whereas the inequality constraints are treated as hard constraints. The multi-objective fuzzy optimal power flow (OPF) formulation was converted into a crisp OPF in a successive linear programming (SLP) framework and solved using an efficient interior point method (IPM). To test the efficacy of the proposed approach, simulations are performed on the IEEE 30-busand IEEE 118-bus test systems. The MFLP optimization is solved for several optimization cases. The obtained results are compared with those presented in the literature. A unique solution with a high satisfaction for the assigned targets is gained. Results demonstrate the effectiveness of the proposed MFLP technique in terms of solution optimality and rapid convergence. Moreover, the results indicate that using the optimal DG location with the MFLP algorithm provides the solution with the highest quality.
We developed a personal blood pressure monitoring system for patients with hypertension or hypotension. The system can be used to measure a patient's blood pressure at home and to transmit the data automatically to a hospital database via the Internet. The accuracy of blood pressure readings using the system was assessed by comparison with readings from a standard digital sphygmomanometer in four subjects. The measurement error for the systolic readings was 1.7-2.7% and for the diastolic readings 2.7-3.2%. The system therefore appears to be a promising means of assessing blood pressure remotely.