DC traction power substation using eighteen-pulse rectifier transformer system

<span lang="EN-US">Twelve-pulse rectification system had been widely integrated in today’s DC traction power sub-station (DC-TPSS). This configuration had successfully mitigated low order harmonic distortion. As some research findings had confirmed that the dc voltage and current ripple factors may further minimize by increasing the number of rectification pulses to 18, 24, or 36. This paper had presented a simulation study to investigate the prospect of implementing an eighteen-pulse rectification system in a DC-TPSS. The theory of phase-shifting transformer used to produce an 18-pulse rectifier is presented with simulation verification. Simulation result shows that 3.69% of grid current distortion index is recorded without installing any filters. In addition, the dc voltage and current ripple may also be further reduced for about 30% compared to a conventional twelve-pulse rectification system.</span>

Voltage Rise Regulation with a Grid Connected Solar Photovoltaic System

Renewable Distributed Generation (RDG), when connected to a Distribution Network (DN), suffers from power quality issues because of the distorted currents drawn from the loads connected to the network over generation of active power injection at the Point of Common Coupling (PCC). This research paper presents the voltage rise regulation strategy at the PCC to enhance power quality and continuous operation of RDG, such as Photovoltaic Arrays (PVAs) connected to a DN. If the PCC voltage is not regulated, the penetration levels of the renewable energy integration to a DN will be limited or may be ultimately disconnected in the case of a voltage rise issue. The network is maintained in both unity power factor and voltage regulation mode, depending on the condition of the voltage fluctuation occurrences at the PCC. The research investigation shows that variation in the consumer’s loads (reduction) causes an increase in the power generated from the PVA, resulting in an increase in the grid current amplitude, reduction in the voltage of the feeder impedance and an increase in the phase voltage amplitude at the PCC. When the system is undergoing unity power factor mode, PCC voltage amplitude tends to rises with the loads. Its phase voltage amplitude rises above an acceptable range with no-loads which are not in agreement, as specified in the IEEE-1547 and Southern Africa grid code prerequisite. Incremental Conduction with Integral Regulator bases (IC + PI) are employed to access and regulate PVA generation, while the unwanted grid current distortions are attenuated from the network using an in-loop second order integral filtering circuit algorithm. Hence, the voltage rise at the PCC is mitigated through the generation of positive reactive power to the grid from the Distribution Static Compensator (DSTATCOM), thereby regulating the phase voltage. The simulation study is carried out in a MATLAB/Simulink environment for PVA performance.

A Real-Time Harmonic Extraction Approach for Distorted Grid

Harmonic interference is a major hazard in the current power system that affects power quality. How to extract harmonics quickly and accurately is the premise to ensure the sustainable operation of power system, which is particularly important in the field of new energy power generation. In this paper, a harmonic extraction method based on a time-varying observer is proposed. Firstly, a frequency estimation algorithm is used to estimate the power grid current frequency, which can estimate the frequency in real time. Then, applying the zero-crossing detection method to convert the frequency into a phase variable. Finally, using the phase variable and integral current signal as input, a observer is modeled to extract each order harmonic component. The proposed method is evaluated on a FGPA test platform, which shows that the method can extract the harmonic components of the grid current and converge within 80 ms even in the presence of grid distortions. In the verification case, the relative errors of the 1st, 5th, 7th and 11th harmonics are 0.005%, −0.003%, 0.251% and 0.620%, respectively, which are sufficiently small.

An Improved Strategy for High-Efficiency Multistage PV Module Using MPPT Technique

Renewable energy supplies are renewable energy sources that are of great benefit to the world today. Among the most commonly used renewable energy resources, solar energy is used to produce electricity, clean water supplies, respectively in every area of our lives. Photovoltaic cell transforms solar energy into electricity type, which includes solar cells. Some MPPT systems have been suggested to obtain optimum efficiency out of this system under different weather conditions. For an efficient operation and power extracted from a PV module, an MPPT is necessary. To improve the accuracy of the Solar Panel, a variety of approaches are used, the most common of which is MPPT or P&O. The basic goal of full power point tracking is to interpret the voltage and current from the solar panel, measure the power, and then display the power to its limit. Multi-stage DC-DC converter manages MPPT, and PWM controls grid current from Inverter. The inverter circuit provides all the activities in a single phase that involve MPPT and grid current power. In this proposed work, the DC / AC converter will be intended to ensure the system's safe interconnection and procedure and to retain the utility grid's power quality, so both MPPT techniques will be analyzed, established and contrasted via a converter to convert the highest energy from PV to the grid.