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PDF Power Quality Issues in Distributed Generation

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These unique properties of power electronic converters are closely related to both the improvement of power quality and its deterioration. This book covers several selected aspects of electrical power quality issues commonly encountered during grid integration processes of today's renewable energy sources.

Distributed Generation and Its Impact on Power Quality in Low-Voltage Distribution Networks

Introduction

One of the crucial examples is the standard characteristics cosφ (P) of the power factor in relation to the active power levels generated. To reveal the purpose of the work, a case study of the investigation of the power quality in the real photovoltaic (PV) system, connected to the TU power systems, is presented.

Power quality issues in the integration process of distributed generation with electrical networks

  • Summary

Inverter-based power generation units are predisposed to implement power factor characteristics depending on the active power output cosφ (P) [10, 43]. The short-circuit power coefficient Rk is used in testing emission limits in the EMC standard [32, 34].

Figure 1. General relations between emission limits, system disturbances level, compatibility level, and equipment im‐
Figure 1. General relations between emission limits, system disturbances level, compatibility level, and equipment im‐

Field measurement case study results

  • Calculation of short circuit condition in PCC
  • Estimation of influence of the investigated PV system on power quality parameters in PCC
  • Verification of the influence of the investigated PV system on power quality parameters in PCC using real measurement

The influence of the investigated PV system on the voltage level in the PCC depends on the adjustment of cosφ (P). A class A power quality recorder was installed at the PCC to analyze the impact of the PV system on power quality concerns using field measurement data.

Figure 7. The diagram of interconnection of the investigated PV system with the LV network and its short circuit equivalent.
Figure 7. The diagram of interconnection of the investigated PV system with the LV network and its short circuit equivalent.

Summary

The presented results provide an overall estimate due to the accuracy of the average class of DC current measurement. Comparisons of the measured power quality parameters with their calculated equivalent show similarity in the 95% range of the data.

Author details

The measurement procedure allows the verification of the real impact of the investigated DG on the power quality in the PCC, however, the task is not easy due to the problems of separating the required impact from the measurement background. One of the proposed approaches is to correlate the changes of the investigated power quality parameters with the activities of the investigated DP, eg, energy production.

It should be noted that not every power quality can be accurately estimated by calculation. Distributed generation and its impact on power quality in low voltage distribution networks http://dx.doi.org.

Applications of Switch-Mode Rectifiers on Micro-grid Incorporating with EV and BESS

  • System configuration
  • DC Micro-grid
  • EV PMSM Drive
  • BESS

In a DC microgrid or distributed power system, the DC sources and energy storage devices must be connected to its common DC link using suitable DC/DC converter [36,37]. Each device is connected to the common DC bus via a bidirectional DC-DC boost buck converter. The output of the flywheel system can be connected directly to the micro-grid common DC bus for its voltage boosting capability.

The interconnected operations from the EV to the microgrid and BESS are also conductive.

Proof Corrections Form

Final Chapter Title

Furthermore, the programmed current can be sent back to the supply network; (ii) G2M operation: the single-phase SMR is formed to allow the utility supply to the microgrid for energy support or to allow the battery to supplement. EV can also perform the G2V/V2G operations via its own schemes or via microgrid interface converters (G2M+M2V)/(V2M+M2G). The battery bank and the SC bank are integrated into the common DC link, respectively via an interleaved and a standard two-way front-end DC/DC converter.

And the SC bank is connected to the battery bank through a diode, so that the recovered regenerative braking energy in SC can be automatically charged to the battery.

Author details Scientific Title: Mr

It mainly consists of a grid-connected DC microgrid, an EV PMSM drive with G2V/V2H/V2G functions, and a grid-connected BESS. By proper arrangement, the G2V charging and V2H/V2G discharging operations are applicable using the integrated converters and converters formed by the embedded motor components. A single-phase boost SMR and a three-phase boost SMR are formed to charge the battery bank through the two-way interlaced buck DC/DC converter with satisfactory line-drawn power quality from the mains.

The DC link voltage (400 V) is set from the 96 V battery bank via a two-cell bidirectional DC/DC interleaved converter.

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Classification of SMRs

  • Schematics
  • Control methods

From the viewpoints of schematic and control approaches, the SMRs can be categorized as follows. The SMR schemes can be categorized into: (i) Single-phase or three-phase, the three-phase SMR being a natural choice for the plants with larger ratings; (ii) Non-insulated or insulated, normally, the latter type of SMR has lower energy conversion efficiency; (iii) Buck, boost, or goat/. As for the buck and buck/boost SMRs, the input layer pass filter is required for the inherently discontinuous current; (iv) Single or multi-stage; (v) One-quadrant or multi-quadrant: the multiple-quadrant SMR has reverse power flow capability from DC side to AC source to achieve the regenerative braking of an SMR-fed AC motor drive; (vi) Hard switching or soft switching; (vii) Standard or bridgeless: the bridgeless SMR has slightly greater efficiency for the reduced diode voltage drop; (viii) Single module or interleaved multi-module: the interleaved SMR can have the advantages of rating enlargement, higher reliability due to redundancy, and smaller current and voltage ripples.

Low-frequency control: for the single-phase boost SMR, only v-loop is needed and only one switching per half AC cycle is applied.

Single-Phase SMRs

  • Operation and schematics
  • Some key issues

Except for the Cuk SMR, input filtering is still required for the other two types of buck/boost SMR. From a control point of view, a simple voltage follower control scheme can be used for these buck/boost SMRs operating in DCM. An input filter is required for the buck/boost SMR due to the discontinuous input current.

The voltage follower control scheme with no internal current loop can be applied for the buck/boost SMR in DCM operation due to its inherent PFC capability.

Figure 3. Some typical single-phase boost SMR circuits: (a) standard SMR; (b) bridgeless SMR; (c) CFPP isolated SMR;
Figure 3. Some typical single-phase boost SMR circuits: (a) standard SMR; (b) bridgeless SMR; (c) CFPP isolated SMR;

Three-phase SMRs

  • Operation and schematics
  • Derated characteristics of a PMSG followed by different AC-DC converters

Neutral-point clamped (NPC) three-phase standard SMR: The three-level NPC three-phase SMR is shown in Fig. For the Vienna SMR and three-phase six-switch standard SMR with satisfactory current mode control, the three-phase line drawn currents are balanced without harmonics. Some typical three-phase boost SMR circuits: (a) 3P1SW SMR; (b) Bridgeless three-phase DCM SMR; (c) Three-stage Viennese SMR; (d) Three-phase standard SMR with six switches; (e) NPC three-phase standard SMR.

The three-phase Vienna SMR is a good candidate to be the followed interface converter of the PMSG from the following compromised considerations: (i).

Figure 5. Some key issues of single-phase boost SMRs.
Figure 5. Some key issues of single-phase boost SMRs.

SMR operations and performances

  • Wind IPMSG based micro-grid

Depreciated characteristics of a PMSG with different AC-DC followed converters and control modes of operation. The derated characteristics of a wind PMSG followed by different AC-DC converters and operating control modes are shown in Fig.

System Components

Control Schemes

Experimental Results

  • Grid-connected BESS

9(a), and the differential mode (DM) and common mode (CM) control schemes of the 1P3W inverter are depicted in Fig. 12(b) and 12(c) are the control schemes of the 3P1SW SMR and LLC resonant DC /DC converter in the developed plug-in energy harvesting system. Measured (vac, iac, iac*, iac') of the bridgeless single-phase boost SMR formed using the nested compo‐.

Power quality problems in distributed generation 72. vb, ib) of the developed charging system is shown in fig.

Figure 9. Control schemes of the developed wind IPMSG based DC micro-grid system: (a) IPMSG with followed Vien‐
Figure 9. Control schemes of the developed wind IPMSG based DC micro-grid system: (a) IPMSG with followed Vien‐

Control Schemes of Three-phase SMR

  • Conclusions

Schematic and control scheme of the established SMR-based three-phase battery charger: (a) schematic; (b) control scheme. Similarly, the results show the good performance of the established three-phase charger based on SMR. On a reluctance motor drive with a three-phase single-phase rectifier on the front.

Design and experimental investigation of a three-phase high power density high efficiency unity power factor PWM (VIENNA) rectifi‐.

Figure 19. Schematic and control scheme of the established three-phase SMR based battery charger: (a) schematic; (b) control scheme.
Figure 19. Schematic and control scheme of the established three-phase SMR based battery charger: (a) schematic; (b) control scheme.

A Comprehensive Modeling and Simulation of Power Quality Disturbances Using MATLAB/SIMULINK

Modeling approach

  • Line fault model
  • Induction motor starting model
  • Transformer energizing model
  • Capacitor bank energizing model
  • Lightning impulse model
  • Single phase nonlinear load model
  • Three-phase nonlinear load model
  • Electric arc furnace model

The voltage drop at the 0.4 kV bus propagates upstream through the transformer to the 11 kV power bus. Voltage drop RMS waveform caused by starting a 75 kW (100 hp) induction motor at a supply of 0.4 kV. Instantaneous waveform of voltage drop caused by starting a 75 kW (100 hp) induction motor at a supply of 0.4 kV.

It is used to simulate voltage sag caused by transformer inrush current and core saturation during energization.

Figure 1. Line fault Simulink model.
Figure 1. Line fault Simulink model.

Conclusion

2] McGranaghan M, Santoso S (2007) Challenges and Trends in Analyzes of Electric Power Quality Measurement Data, EURASIP Journal on Advances in Signal Process‐. 5] Patne NR, Thakre K L (2007) Stochastic estimation of voltage drop due to power system faults by using PSCAD/EMTDC software as a simulation tool, Jour‐. 8] Ntombela M, Kaberere KK, Folly KA, Petroianu A I (2005) An investigation of the capabilities of MATLAB Power System Toolbox for small signal stability analysis in Power Systems, IEEE PES Conference and Exposition.

A comprehensive modeling and simulation of power quality disturbances using MATLAB/SIMULINK http://dx.doi.org.

An Application of Simple and Compact Genetic Algorithms for Estimating Harmonic Components

  • Problem description
  • Algorithms
    • Simple genetic algorithm
    • Compact genetic algorithm
  • Methodology
  • Results
    • Estimation of the harmonic components using the proposed methodologies
    • Observation of the mean error
    • Observation of the number of evaluations
    • Observation of the standard deviation
  • Discussions

The mean error values, number of evaluations and standard deviation were obtained from the mean of the 4 waveforms. Figures 10, 11 and 12 show graphs of the mean error in the number of individuals given the tournament size of 2, 8 and 32 individuals. Figures 13, 14 and 15 show graphs of the number of evaluations in the number of individuals given the tournament size of 2, 8 and 32.

Figures 16, 17 and 18 show graphs of the standard deviation in the number of individuals given the tournament size of 2, 8 and 32.

Figure 1. Pseudocode of SGA.
Figure 1. Pseudocode of SGA.

Acknowledgements

It is important to emphasize that when using a population size of 100 and a tournament size of 2 individuals, CGA manages to achieve a lower error than SGA with the same configuration. For the CGA, with a tournament size of 2 and a population size of 100, the resulting waveform was closer to the reference waveform than for the SGA with a tournament size of 8 and a population size of 500. It was also noted that for a population size of 100 and a tournament size of 2 , the number of evaluations of both CGA and SGA was very close.

Makram, “A digital recursive measurement scheme for online detection of power system harmonics,” IEEE Transactions on Power Delivery, vol.

A Distributed Web-Based System for Temporal and Spatial Power Quality Analysis

Measurement point structure

In this way it is possible to record and analyze the trend of the electricity grid immediately after the voltage returns and determine the duration of the interruption. Starting from the samples of the signal si, a multi-harmonic least squares algorithm is performed to estimate the frequency (ω^). We use the variance σr2 of the residual for the detection of the presence of interharmonics and transients.

The algorithm used for parameter estimation is multiharmonic least squares fitting.

Figure 1. Block scheme of the PQ measurement device.
Figure 1. Block scheme of the PQ measurement device.

Server

As an indicator for the presence of some non-harmonic disturbances (interharmonics, subharmonics, transients, etc.), the software calculates the variance of the residuals defined as the difference between the obtained samples and the model-based reconstructed signal. If the deviation is over a selected threshold determined based on the SNR (signal-to-noise ratio) of the acquisition map, the associated record will be analyzed a second time by a remote machine in more detail. So if a monitoring point is added, a directory (and its subdirectories) will be added to the server directories.

This website provides temporal and spatial analysis of the values ​​obtained by the monitoring system and retrieves information from the database and stored binaries.

Web interface

  • Temporal analysis web page
  • Harmonic spectrum window
  • Three-phase analysis window
  • Residual analysis window
  • Spatial analysis page

Clicking on the "Spectrum" button at the bottom of the time analysis page opens a new window. The bottom two graphs show the symmetrical component (positive, negative and zero sequence) obtained by Fortescue transformation of the R-S-T phasors. The bar at the top of the window allows you to select the harmonic order to view.

The height of the cylinders is proportional to the value of a registered parameter (selectable in the form on the right).

Figure 6. The figure shows the main page of the web site. The control bar on the top allows the selection of the meas‐
Figure 6. The figure shows the main page of the web site. The control bar on the top allows the selection of the meas‐

Conclusions

A system for monitoring the quality of electricity over an Ethernet network, based on an embedded system, production and distribution of electricity. Web-based multi-channel power quality monitoring system for large grid, power system management and control. Rome, the first example of perceived power quality: A telecommunications perspective.

In: Proceedings of International Conference on Renewable Energies and Power Quality (ICREPQ April 2011; Las Palmas de Gran Canaria, Spanje.

Hình ảnh

Figure 1. General relations between emission limits, system disturbances level, compatibility level, and equipment im‐
Figure 2. Laboratory setup for emission and immunity tests for DC-supplied inverters IEC/TR 61000-3-15 [35].
Figure 2. Laboratory setup for emission and immunity tests for DC-supplied inverters IEC/TR 61000-3-15 [35].
Figure 4. Standard characteristic cosφ (P) for the generation unit within the range of maximum apparent power S Emax
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