PFC Cuk Converter Fed BLDC Motor Drive

 

ABSTRACT:

This paper deals with a power factor correction (PFC) based Cuk converter fed brushless DC motor (BLDC) drive as a cost effective solution for low power applications. The speed of the BLDC motor is controlled by varying the DC bus voltage of voltage source inverter (VSI) which uses a low frequency switching of VSI (electronic commutation of BLDC motor) for low switching losses. A diode bridge rectifier (DBR) followed by a Cuk converter working in discontinuous conduction mode (DCM) is used for control of DC link voltage with unity power factor at AC mains. Performance of the PFC Cuk converter is evaluated in four different operating conditions of discontinuous and continuous conduction mode (CCM) and a comparison is made to select a best suited mode of operation. The performance of the proposed system is simulated in MATLAB/Simulink environment and a hardware prototype of proposed drive is developed to validate its performance over a wide range of speed with unity power factor at AC mains.

KEYWORDS:

  1. CCM
  2. Cuk converter
  3. DCM
  4. PFC
  5. BLDC Motor
  6. Power Quality

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 image001

Fig. 1. A BLDC motor drive fed by a PFC Cuk converter using a current multiplier approach.

 image002

 Fig. 2. A BLDC motor drive fed by a PFC Cuk converter using a voltage follower approach.

 EXPECTED SIMULATION RESULTS:

 image003

Fig.3. Simulated performance of BLDC motor drive with Cuk converter operating in CCM

image004

Fig. 4. Simulated performance of BLDC motor drive with Cuk converter operating in DICM (Li).

image005

Fig. 5. Simulated performance of BLDC motor drive with Cuk converter operating in DICM (Lo).

 image006

 Fig. 6. Simulated performance of BLDC motor drive with Cuk converter operating in DCVM.

 CONCLUSION:

A Cuk converter for VSI fed BLDC motor drive has been designed for achieving a unity power factor at AC mains for the development of low cost PFC motor for numerous low power equipments such fans, blowers, water pumps etc. The speed of the BLDC motor drive has been controlled by varying the DC link voltage of VSI; which allows the VSI to operate in fundamental frequency switching mode for reduced switching losses. Four different modes of Cuk converter operating in CCM and DCM have been explored for the development of BLDC motor drive with unity power factor at AC mains. A detailed comparison of all modes of operation has been presented on the basis of feasibility in design and the cost constraint in the development of such drive for low power applications. Finally, a best suited mode of Cuk converter with output inductor current operating in DICM has been selected for experimental verifications. The proposed drive system has shown satisfactory results in all aspects and is a recommended solution for low power BLDC motor drives.

REFERENCES:

[1] J. F. Gieras and M. Wing, Permanent Magnet Motor Technology- Design and Application, Marcel Dekker Inc., New York, 2002.

[2] C. L. Xia, Permanent Magnet Brushless DC Motor Drives and Controls, Wiley Press, Beijing, 2012.

[3] Y. Chen, Y, C. Chiu, C, Y. Jhang, Z. Tang and R. Liang, “A Driver for the Single-Phase Brushless DC Fan Motor with Hybrid Winding Structure,” IEEE Trans. Ind. Electron., Early Access, 2012.

[4] S. Nikam, V. Rallabandi and B. Fernandes, “A high torque density permanent magnet free motor for in-wheel electric vehicle application,” IEEE Trans. Ind. Appl., Early Access, 2012.

[5] X. Huang, A. Goodman, C. Gerada, Y. Fang and Q. Lu, “A Single Sided Matrix Converter Drive for a Brushless DC Motor in Aerospace Applications,” IEEE Trans. Ind. Electron., vol.59, no.9, pp.3542-3552, Sept. 2012.

 

2016-17 IEEE Electrical Projects List

Electrical engineering is a field of engineering that generally deals with the study and application of electricity, electronics, and electro magnetism. This field first became an identifiable occupation in the later half of the 19th century after commercialization of the electric telegraph, the telephone, and electric power distribution and use. Subsequently, broad casting and recording media made electronics part of daily life. The invention of the transistor, and later the integrated circuit, brought down the cost of electronics to the point they can be used in almost any household object.

Electrical engineering has now subdivided into a wide range of sub fields including electronics, digital computers, power engineering, tele communications, control systems, radio-frequency engineering, signal processing, instrumentation, and microelectronics. Many of these sub disciplines overlap and also overlap with other engineering branches, spanning a huge number of specializations such as hardware engineering, power electronics, electro magnetics & waves, microwave engineering, nanotechnology, electro chemistry, renewable energies, mechatronics, electrical materials science, and many more.

Electrical engineers typically hold a degree in electrical engineering or electronic engineering. Practicing engineers may have professional certification and be members of a professional body. Such bodies include the Institute of Electrical and Electronics Engineers (IEEE) and the Institution of Engineering and Technology (professional society) (IET).

Electrical engineers work in a very wide range of industries and the skills required are likewise variable. These range from basic circuit theory to the management skills required of a project manager. The tools and equipment that an individual engineer may need are similarly variable, ranging from a simple voltmeter to a top end analyzer to sophisticated design and manufacturing software.

 

2016-17-project-list

2016-17 IEEE Electrical Projects list

Active Power Factor Correction for Rectifier using Micro-controller

 

ABSTRACT:

Industrialization increases the use of inductive load and hence power system loses its efficiency. Rigid occurrence of mains rectification circuits and the day by day increase in electronics consumers inside the electronic devices enhances the cause of mains harmonic distortion. Power is very precious in the present technological revolution and thus it requires to improve the power factor with a suitable method.This paper presents the simulation and the experimental results for active power factor correction system. Closed loop circuit is simulated in MATLAB using PI controller. The system has been implemented in MATLAB/SIMULINK environment.

 

KEYWORDS:

 

  1. Micro-controller
  2. Power factor correction system
  3. DC-DC boost converter
  4. Total harmonic distortion (THD)
  5. PI controller

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. Circuit diagram of active power factor correction system

EXPECTED SIMULATION RESULTS:

 image002

Fig. 2. Input voltage of conventional converter in PSIM software

image003

Fig. 3. Output voltage of conventional converter in PSIM software

image004

Fig. 4. Output and input current waveform of conventional converter in PSIM software.

image005

Fig. 5. Input current waveform at 15kHz in PSIM software

image006

Fig. 6  Input voltage waveform at 15 kHz in PSIM software.

image007

Fig. 7 . Output voltage waveform at 15kHz in PSIM software.

image008

Fig. 8. Input current waveform in PSIM software.

image009

Fig. 9. Input voltage waveform in PSIM software

image010

Fig. 10. Output voltage waveform in PSIM software.

image011

Fig. 11. Firing pulse for MOSFET IRF640 captured in DSO.

image012

Fig. 12. Input current and voltage waveform captured in DSO.

CONCLUSION:

Analog firing circuit designing makes circuit complex and also it requires the maintenance. Employing microcontroller instead reduces all its disadvantages thus being economical. It is easier to design with precision output. It was very interesting and absorbing to design AC-DC converter in the power electronics laboratory using power MOSFET IRF640.The design is adequate for many purposes. These improvements have been tested in principle, but some detailed work remains to be done in this area. This research work can be extended for the speed control of the motor using PI controller or fuzzy logic controller, Maximum Power Point Tracking (MPPT) using this circuit can be studied later on.

 REFERENCES:

[1] B.K.Bose, “Modern power electronics and AC Drives”, PHI,2001 .

[2] P.C.Sen, “Power Electronics”, Tata McGraw Hill Publishers, 4th edition, 1987.

[3] N.Mohan, T.M.Undeland, W.P.Robbins, “Power Electronics: Converters application and Design”, New York: Wiley, 3rd edition, 2006.

[4] Mohammed E. El-Hawary, “Principles of Electric Machines with Power Electronic Applications”, Wiley India, 2nd edition, 2011.

[5] Gayakwad, “Operational Amplifier”, Prentice Hall of India, 2009.

 

 

 

Power Management Strategy for a Multi-Hybrid Fuel Cell/Energy Storage Power Generation Systems

 

 ABSTRACT:

This paper depicts a new configuration for modular hybrid power conversion systems, namely, multi-hybrid generation system (MHGS), and parallel connection at the output, such that the converter of each unit shares the load current equally. This is a significant step towards realizing a modular power conversion system architecture, where smaller units can be connected in any series/parallel grouping to realize any required unit specifications. The supercapacitor (SC) as a complementary source is used to compensate for the slow transient response of the fuel cell (FC) as a main power source. It assists the Fe to meet the grid power demand in order to achieve a better performance and dynamic behavior. Reliable control of the proposed MHGS with multiple units is also a challenging issue. In this paper, a simple control method to achieve active sharing of load current among MHGS modules is proposed. The simulation results verify the performance of the proposed structure and control scheme.

KEYWORDS:

  1. Multi-hybrid generation system (MHGS)
  2. Fuel cell (FC)
  3. Dc/dc converter
  4. Supercapacitor (SC)
  5. Average load sharing (ALS)

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

 image001

Figure 1. Configuration of the FC/SC hybrid system.

 CONTROL SYSTEM:

 image002

Figure 2. Proposed control strategy of hybrid FC/SC power conversion

.EXPECTED SIMULATION RESULTS:

 image003

Figure 3. Dynamic response of MHGS, (a) load active power, (b) output power of hybrid units, (c) FC stack and SC module power of first hybrid umt, and (d) FC stack and SC module power of second hybrid unit.

image004

Figure 4. Output waveform of (a) dc bus voltage, and (b) dc bus current.

image005

Figure 5. Waveforms of unit’s (a) hydrogen input flow, (b) hydrogen partial pressure, and (d) oxygen partial pressure.

CONCLUSION:

This paper proposes a comprehensive and effective multihybrid FC/SC power generation system structure and control strategy. The detailed model of the modular FC/SC hybrid system which includes an FC stack as a main power source and an SC as a complementary source is presented. In order to balance power sharing among the units, average load sharing technique is used. Elimination of outer voltage loop of ALS technique enhances reliability and reduces the complexity of the control structure. To show the superior dynamic behavior and power sharing of the proposed MHGS, results for two parallel hybrid systems are provided. The presented analysis and the simulation results offer a valuable structure with an effective control strategy to enhance power quality and management. These performances allow the integration MHGS into complex distributed generation systems such as microgrids.

REFERENCES:

[1] P. Chiradeja and R. Ramakumar, “An approach to quantify the technical benefits of distributed generation,” IEEE Trans. Energy Convers., voL 19,no. 4,pp. 764-773,Dec,2004.

[2] B. Wojszczyk, R. Uluski, and F. Katiraei, ‘The role of distributed generation and energy storage in utilities of the future,” in Proc. IEEE PES Gen. Meet., 2008, pp. 1-2.

[3] K. Rajashekara, “Hybrid fuel-cell strategies for clean power generation,” IEEE Trans. Ind Appl., voL 41, no. 3, pp. 682-689, May/Jun. 2005.

[4] 1. M. Carrasco, L. G. Franquelo, 1. T. Bialasiewicz, E. Galvan, R. C. PortilloGuisado, M. A M. Prats, 1. L Leon, and N.Moreno-Alfonso, “Power-electronic systems for the grid integration of renewable energy sources: A survey,” IEEE Trans. Ind Electron., voL 53, no. 4, pp. 1002- 1016, Jun. 2006.

[5] Z. Jiang, and R. A Dougal, “A compact digitally controlled fuel cell/battery hybrid power source,” IEEE Trans. Ind Electron., voL 53, no. 4,pp. 1094-1104,Jun. 2006.

Performance Analysis of P&O and Incremental Conductance MPPT Algorithms Under Rapidly Changing Weather Conditions

 

ABSTRACT:

In this paper, the comparative analysis of two maximum power point tracking (MPPT) algorithms namely Perturb and Observe (P&O) and Incremental conductance (InC) is presented for the Photo-Voltaic (PV) power generation system. The mathematical model of the PV array is developed and transformed into MATLAB/Simulink environment. This model is used throughout the paper to simulate the PV source characteristics identical to that of a 20 Wp PV panel. The MPPT algorithms generate proper duty ratio for interfacing dc-dc boost converter driving resistive load. The performances of these algorithms are evaluated at gradual and rapidly changing weather conditions where it is observed that InC method tracks the rapidly changing insolation level at a faster rate as compared to P&O. Depending upon the prevailing environmental conditions the MPPT algorithms finds a unique operating point to track the maximum available power. The algorithms find a fixed duty ratio by comparing the previous power, voltage and current thereby optimizing the power output of the panel. The main objective is to compare the tracking capability and stability of the algorithms under different environmental situations on par with other real world tests.

KEYWORDS:

  1. Maximum Power Point Tracking (MPPT)
  2. Photovoltaic (PV)
  3. DC-DC Boost Converter
  4. Perturb & Observe (P&O)
  5. Incremental Conduction (InC)

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 image001

Fig. 1. PV Panel Interfaced with Boost Converter for MPP Tracking

 EXPECTED SIMULATION RESULTS:

 image002

 Fig. 2. Experimental Measured PV Characteristics

 image003

 Fig. 3. Experimental Results showing Source Voltage, Load Voltage and Duty Ratio

image004

Fig. 4. Performances of P&O and InC under slowly changing climatic conditions (a) Irradiations Levels (b), (c) & (d) Duty ratio (e) Panel Voltage (f) Panel Power (g) Oscillations in Duty by the algorithms

image005

Fig. 5. Performances of P&O and InC under rapidly changing climatic conditions (a) Insolations (b)& (c) Duty ratio (d)&(e) Panel Voltage (f) Panel Power

 CONCLUSION:

The presented studies in this paper were the comparative analysis of two MPPT algorithms, Perturb & Observe and Incremental Conductance and conducted through boost converter. The simulation results prove positively that the P&O and the Incremental Conductance MPPTs reach the intended maximum power point. In the slowly changing whether both algorithms perform without significantly changes. It has observed that the Incremental Conductance reaches at the MPP three times faster than P&O in all cases and shows better performance for rapid changes and a better stability when the MPP is achieved. It has observed that P&O shows oscillations around the MPP when it reaches in steady state position which results in some power loss. But in case of InC there are no additional oscillations at steady state condition. However the P&O MPPT are mostly used in practice due to their simplicity. The originality and the specificity of the presented results obtain during this research reside in the fact that external parameters as irradiation and fixed temperature were introduced, at first as linear functions (ramp input) and, at second as random (step input) ones describing more closely the actual applicative conditions. The effect of the changing weather on the voltage and power of the PV panel according to change in MPP has shown in the results section.

REFERENCES:

[1] Tariq, J. Asghar, “Development of an Analog Maximum Power Point Tracker for Photovoltaic Panel”, PEDS. International Conference on, 2005, vol. 1, no., pp. 251, 255.

[2] H. Al-Bahadili, H. Al-Saadi, R. Al-Sayed, M.A.-S. Hasan, “Simulation of maximum power point tracking for photovoltaic systems”, Applications of Information Technology to Renewable Energy Processes and Systems (IT-DREPS), 1st International Conference & Exhibition on the , 2013, vol., no., pp. 79,84.

[3] Lu Yuan, Cui Xingxing, “Study on maximum power point tracking for photovoltaic power generation system”, Computer Science and Information Technology (ICCSIT), 3rd IEEE International Conference on, 2010, vol. 9, pp. 180,183.

[4] G. Walker, “Evaluating MPPT converter topologies using a MATLAB PV model”, Journal of Electrical & Electronics Engineering, 2001, Australia, IEAust, vol. 21, No. 1, pp. 49-56.

[5] Beriber, D.; Talha, A, “MPPT techniques for PV systems,” Power Engineering, Energy and Electrical Drives (POWERENG), 2013 Fourth International Conference on, vol., no., pp.1437, 1442, 13-17 May 2013.

New Control Strategy for Three-Phase Grid-Connected LCL Inverters without a Phase-Locked Loop

 

ABSTRACT:

 The three-phase synchronous reference frame phase-locked loop (SRF-PLL) is widely used for synchronization applications in power systems. In this paper, a new control strategy for three-phase grid-connected LCL inverters without a PLL is presented. According to the new strategy, a current reference can be generated by using the instantaneous power control scheme and the proposed positive-sequence voltage detector. Through theoretical analysis, it is indicated that a high-quality grid current can be produced by introducing the new control strategy. In addition, a kind of independent control for reactive power can be achieved under unbalanced and distorted grid conditions. Finally, the excellent performance of the proposed control strategy is validated by means of simulation and experimental results.

KEYWORDS:

1.Control strategy

2.Grid-connected inverters

3. Instantaneous power control scheme

4.LCL filter

5.Positive-sequence voltage detector

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. Block diagram of the control system with LCL filter.

 EXPECTED SIMULATION RESULTS:

 image002

 Fig. 2. Simulation results of the proposed control system. (a) Generated current reference signals. (b) A-phase grid voltage and three-phase current. (c) Actual active and reactive powers.

image003

Fig. 3. Experimental results of the positive-sequence voltage detector under actual grid operating conditions. (a) Utility voltage and the detected positive-sequence signals. (b) Harmonic spectrum of the utility voltage. (c) Harmonic spectrum of the detected positive-sequence signals.

image004

Fig. 4. Experimental results of a step in the reactive power reference. (a) A-phase grid voltage and three-phase current. (b) A-phase grid voltage and A-phase current.

 CONCLUSION:

A new control structure for three-phase grid-connected voltage source inverters (VSI) with an LCL-filter is proposed. By using the instantaneous power control scheme and the proposed positive-sequence voltage detector, the current reference can be indirectly generated, which avoids the complex PLL. The effectiveness of the proposed system for three-phase grid-connected VSIs is demonstrated via simulation results, which show a significant improvement in both the steady state and transient behavior. The same behavior is experimentally verified. The fast dynamic response to a reference step is not affected by the inclusion of additional control loops. Good performance is guaranteed even under unbalanced and distorted grid voltages.

REFERENCES:

[1] X. Wang, J. M. Guerrero, F. Blaabjerg, and Z. Chen, “A review of power electronics based microgrids,” Journal of Power Electronics, Vol. 12, No. 1, pp. 181-192, Jan. 2012.

[2] S. Peng, A. Luo, Y. Chen, and Z. Lv, “Dual-loop power control for single-phase grid-connected converters with LCL filters,” Journal of Power Electronics, Vol. 11, No. 4, pp. 456-463, July. 2011.

[3] F. Blaabjerg, R. Teodorescu, M. Liserre, and A. V. Timbus, “Overview of control and grid synchronization for distributed power generation systems,” IEEE Trans. Ind. Electron., Vol. 53, No. 5, pp. 1398-1409, Oct. 2006.

[4] R. Inzunza, T. Sumiya, Y. Fujii, and E. Ikawa, “Parallel connection of grid-connected LCL inverters for MW-scaled photovoltaic systems,” in Proc. IEEE IPEC, pp. 1988-1993, 2010.

[5] T. Noguchi, H. Tomiki, S. Kondo, and I. Takahashi, “Direct power control of PWM converter without power-source voltage sensors,” IEEE Trans. Ind. Appl., Vol. 34, No. 3, pp. 473-479, Mar./ Jun. 1998.

Integrating Hybrid Power Source Into an Islanded MV Microgrid Using CHB Multilevel Inverter Under Unbalanced and Nonlinear Load Conditions

 

ABSTRACT:

This paper presents a control strategy for an islanded medium voltage microgrid to coordinate hybrid power source (HPS) units and to control interfaced multilevel inverters under unbalanced and nonlinear load conditions. The proposed HPS systems are connected to the loads through a cascaded H-bridge (CHB) multilevel inverter. The CHB multilevel inverters increase the output voltage level and enhance power quality. The HPS employs fuel cell (FC) and photovoltaic sources as the main and supercapacitors as the complementary power sources. Fast transient response, high performance, high power density, and low FC fuel consumption are the main advantages of the proposed HPS system. The proposed control strategy consists of a power management unit for the HPS system and a voltage controller for the CHB multilevel inverter. Each distributed generation unit employs a multiproportional resonant controller to regulate the buses voltages even when the loads are unbalanced and/or nonlinear. Digital time-domain simulation studies are carried out in the PSCAD/EMTDC environment to verify the performance of the overall proposed control system.

KEYWORDS:

  1. Cascaded H-bridge (CHB) multilevel inverter
  2. Fuel cell (FC)
  3. Hybrid power source (HPS)
  4. Multiproportional resonant (multi-PR)
  5. Photovoltaic (PV)
  6. Supercapacitor (SC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. Single-line diagram of MV microgrid consisting of two DG units.

image002

Fig. 2. Proposed structure of the hybrid FC/PV/SC power source.

EXPECTED SIMULATION RESULTS:

image003

Fig. 3. Microgrid response to unbalanced and nonlinear load changes in feeder F1 . (a) and (b) Instantaneous real and reactive powers of feeders.

image004

Fig. 4. Microgrid response to the unbalanced and nonlinear load changes applied to feeder F1 ; positive-sequence, negative-sequence, and harmonic components of loads currents at (a) feeder F1 and (b) feeder F2 .

 image005

Fig. 5. Dynamic response of DG units to unbalanced and nonlinear load changes applied to feeder F1 . (a) and (b) Real and reactive power components of DG units.

image006

Fig. 6. Microgrid response to the unbalanced and nonlinear load changes applied to feeder F1 ; positive-sequence, negative-sequence, and harmonic currents of (a) DG1 and (b) DG2 .

image007

Fig. 7. (a) Instantaneous current waveforms, (b) five-level-inverter output voltage, and (c) voltage waveforms of each phase of DG1 ’s CHB inverter due to the nonlinear load connection to feeder F1 .

image008

Fig. 8. (a) Instantaneous current waveforms, (b) five-level-inverter output voltage, and (c) voltage waveforms of each phase of DG1 ’s CHB inverter due to the single-phase load disconnection from feeder F1 .

image009

Fig. 9. (a) Voltage THD and (b) VUF at DG1 ’s terminal.

image010

Fig. 10. Voltages of dc links for DG1 ’s units.

image011

Fig. 11. Dynamic response of DG1 to load changes; currents of FC stacks and PV units for each HPS. (a) Phase a, (b) phase b, and (c) phase c.

image012

Fig. 12. Dynamic response of DG1 to load changes; average current of SC module of each HPS. (a) Phase a, (b) phase b, and (c) phase c.

 

CONCLUSION:

This paper presents an effective control strategy for an islanded microgrid including the HPS and CHB multilevel inverter under unbalanced and nonlinear load conditions. The proposed strategy includes power management of the hybrid FC/PV/SC power source and a voltage control strategy for the CHB multilevel inverter. The main features of the proposed HPS include high performance, high power density, and fast transient response. Furthermore, a multi-PR controller is presented to regulate the voltage of the CHB multilevel inverter in the presence of unbalanced and nonlinear loads. The performance of the proposed control strategy is investigated using PSCAD/EMTDC software. The results show that the proposed strategy:

1) regulates the voltage of the microgrid under unbalanced and nonlinear load conditions,

2) reduces THD and improves power quality by using CHB multilevel inverters,

3) enhances the dynamic response of the microgrid under fast transient conditions,

4) accurately balances the dc-link voltage of multilevel inverter modules, and

5) effectively manages the powers among the power sources in the HPS system.

 REFERENCES:

[1] H.Zhou,T. Bhattacharya,D.Tran,T. S. T. Siew, and A. M. Khambadkone, “Composite energy storage system involving battery and ultracapacitor with dynamic energymanagement in microgrid applications,” IEEE Trans. Power Electron., vol. 26, no. 3, pp. 923–930, Mar. 2011.

[2] W. S. Liu, J. F. Chen, T. J. Liang, and R. L. Lin, “Multicascoded sources for a high-efficiency fuel-cell hybrid power system in high-voltage application,” IEEE Trans. Power Electron., vol. 26, no. 3, pp. 931–942, Mar. 2011.

[3] A. Ghazanfari, M. Hamzeh, and H. Mokhtari, “A control method for integrating hybrid  power source into an islanded microgrid through CHB multilevel inverter,” in Proc. IEEE Power Electron., Drive Syst. Technol. Conf., Feb. 2013, pp. 495–500.

[4] IEEE Recommended Practice for Electric Power Distribution for Industrial Plants. ANSI/IEEE Standard 141, 1993.

[5] IEEE Recommended Practices and Requirements for Harmonic Control in Electrical Power System. IEEE Standard 519, 1992.

 

Distributed Generation System Control Strategies in Microgrid Operation

 

ABSTRACT:

Control strategies of distributed generation (DG) are investigated for different combination of DG and storage units in a microgrid. This paper develops a detailed photovoltaic (PV) array model with maximum power point tracking (MPPT) control, and presents real and reactive power (PQ) control and droop control for DG system for microgrid operation. In grid-connected mode, PQ control is developed by controlling the active and reactive power output of DGs in accordance with assigned references. In islanded mode, DGs are controlled by droop control. Droop control implements power reallocation between DGs based on predefined droop characteristics whenever load changes or the microgrid is connected/disconnected to the grid, while the microgrid voltage and frequency is maintained at appropriate levels. This paper presents results from a test microgrid system consisting of a voltage source converter (VSC) interfacing with a DG, a PV array with MPPT, and changeable loads. The control strategies are tested via two scenarios: the first one is to switch between grid-connected mode and islanded mode and the second one is to change loads in islanded mode. Through voltage, frequency, and power characteristics in the simulation under such two scenarios, the proposed control strategies can be demonstrated to work properly and effectively.

KEYWORDS:

  1. Distributed generation
  2. PV
  3. Microgrid
  4. Droop control
  5. PQ control

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. Schematic of the microgrid.

CONTROL SYSTEM:

image002

Fig. 2. Schematic of the PQ control.

image003

Fig. 3. Schematic of the droop control.

 EXPECTED SIMULATION RESULTS:

 image004

Fig. 4. PQ control under grid-connected mode.

image005

Fig. 5. Droop control for switching modes.

image006

Fig. 6. Droop control for varying load.

 

CONCLUSION:

In this paper a detailed PV model with MPPT, and PQ and droop controllers is developed for inverter interfaced DGs. The use of PQ control ensures that DGs can generate certain power in accordance with real and reactive power references. Droop controller is developed to ensure the quick dynamic frequency response and proper power sharing between DGs when a forced isolation occurs or load changes. Compared to pure V/f control and master-slave control, the proposed control strategies which have the ability to operate without any online signal communication between DGs make the system operation cost-effective and fast respond to load changes. The simulation results obtained shows that the proposed controller is effective in performing real and reactive power tracking, voltage control and power sharing during both grid-connected mode and islanded mode. To fully represent the complexity of the microgrid, future work will include the development of hierarchical controllers for a microgrid consisting of several DGs and energy storage system. The function of primary controller is to assign optimal power reference to each DG to match load balances and the secondary controllers are designed to control local voltage and frequency.

REFERENCES:

Barsali, S., Ceraolo M., Pelacchi, P., and Poli, D. (2002). Control techniques of dispersed generators to improve the continuity of electricity supply. IEEE Conf., Power Engineering Society, vol.2, pp.789-794.

Cai, N., and Mitra J. (2010). A decentralized control architecture for a microgrid with power electronic interfaces. IEEE conf., North American Power Symposium, pp. 1-8.

Chen, X., Wang, Y.H., and Wang, Y.C. (2013). A novel seamless transferring control method for microgrid based on master-slave configuration. IEEE Conf., ECCE Asia, pp. 351-357.

Cho, C. H., Jeon, J.H., Kim, J.Y., Kwon, S., Park, K., and Kim, S. (2011). Active synchronizing control a microgrid. IEEE Trans., Power Electron., vol. 26, no. 12, pp. 3707-3719

Choi, J.W. and Sul, S.K. (1998). Fast current controller in three-phase AC/DC boost converter using d-q axis crosscoupling. IEEE Trans., Power Electron., vol.13, no.1, pp. 179-185.

Review and Comparison of Step-Up Transformerless Topologies for Photovoltaic AC-Module Application

ABSTRACT:

This paper presents a comprehensive review of step-up single phase non isolated inverters suitable for ac-module applications. In order to compare the most feasible solutions of the reviewed topologies, a benchmark is set. This benchmark is based on a typical ac-module application considering the requirements for the solar panels and the grid. The selected solutions are designed and simulated complying with the benchmark obtaining passive and semiconductor components ratings in order to perform a comparison in terms of size and cost. A discussion of the analyzed topologies regarding the obtained ratings as well as ground currents is presented. Recommendations for topological solutions complying with the application benchmark are provided.

KEYWORDS:

  1. AC-module
  2. Photovoltaic(PV)
  3. Step-up Inverter
  4. Transformerless

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

image001

Fig.1 Block diagram of a two stage topology for an ac module

STEP-UP TRANSFORMERLESS INVERTERS:

image002

Fig 2 Boost converter and full bridge inverter

Time sharing boost converter with full bridge inverter

Fig 3 Time sharing boost converter with full bridge inverter

Parallel resonant soft switched boost converter and full bridge inverter

Fig 4 Parallel resonant soft switched boost converter and full bridge inverter

Parallel input series-output bipolar dc output converter and full bridge inverter

Fig 5 Parallel input series-output bipolar dc output converter and full bridge inverter

Boost converter and half bridge inverter

Fig 6 Boost converter and half bridge inverter

Boost converter and neutral point clamped inverter

Fig 7 Boost converter and neutral point clamped inverter

Series combined boost and buck boost and half bridge inverter

Fig 8 Series combined boost and buck boost and half bridge inverter

Center-tapped coupled inductor converter with bipolar output and half bridge inverter

Fig  9 Center-tapped coupled inductor converter with bipolar output and half bridge inverter

Single inductor bipolar output buck-boost converter and half bridge inverter

Fig 10 Single inductor bipolar output buck-boost converter and half bridge inverter

 Boost + FB integrated and dual grounded

Fig  11 Boost + FB integrated and dual grounded

Block diagram of a pseudo-dc-link topology for an ac module

Fig 12 Block diagram of a pseudo-dc-link topology for an ac module

Buck-boost DCM converter and unfolding stage

Fig 13 Buck-boost DCM converter and unfolding stage

Noninverting buck-boost DCM converter and unfolding stage

Fig 14 Noninverting buck-boost DCM converter and unfolding stage

Switched inductor buck boost DCM converter and unfolding stage

Fig 15 Switched inductor buck boost DCM converter and unfolding stage

 Boost buck time sharing converter and unfolding stage

Fig 16 Boost buck time sharing converter and unfolding stage

Block diagram of a single stage topology for an ac module

Fig 17 Block diagram of a single stage topology for an ac module

Universal single stage grid connected inverter

Fig 18 Universal single stage grid connected inverter

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Fig 19 Integrated boost converter

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Fig 20 Differential boost converter

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Fig 21 Boost inverter with improved zero crossing.

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Fig 22 Integrated Buck boost inverter

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Fig 23 Buck Boost inverter with extended input voltage range

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Fig 24 Differential buck boost inverter

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Fig 25 Two sourced anti parallel buck boost inverter

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Fig 26 Single stage full bridge buck boost inverter

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Fig 27 Buck boost based single stage inverter

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Fig 28 Switched inductor buck boost based single stage inverter

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Fig 29 Single inductor buck boost based inverter

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Fig 30 Doubly grounded single inductor buck boost based inverter

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Fig 31 Single inductor  buck boost based inverter with dual ground

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Fig 32 Three switch buck boost inverter

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Fig 33 Coupled inductor buck boost inverter

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Fig 34 Impedance-admittance conversion theory based inverter

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Fig 35 Single phase Z source inverter

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Fig 36 Semi quasi Z source inverter with continuous voltage gain

 

CONCLUSION:

In this paper, a comprehensive review of single phase non isolated inverters for ac module applications is presented. Both the grid connection and the solar panel requirements are analyzed emphasizing the leakage current regulation as it is a main concern in non isolated PV grid connected inverters. In order to compare the most suitable solutions of the reviewed topologies under the same specifications, a benchmark of a typical ac module application is set. These solutions have been designed and simulated, obtaining ratings for the passive and the semiconductor components. These ratings are used for the topology comparison in terms of size and cost. Furthermore, detailed simulations of representative topologies have been performed using semiconductor and inductor models to estimate the efficiency of the reviewed solutions. As a result of the comparison, the required voltage boost necessary for the connection to the European grid is difficult to achieve with transformerless topologies, but it is adequate for U.S. requirements. Two stage topologies, including the solution with dual grounding capability that theoretically avoids the ground leakage currents, are the preferred option for the set benchmark in which switching frequency for the dc-dc stage is set twice than for the dc-ac one. The two stage combination of a step-up dc-dc converter and a step-up inverter should be considered. In addition, the analyzed pseudo-dc-link approaches are an alternative solution in terms of size and cost. Furthermore, ground currents are expected to be low in these solutions because of the line frequency interface and weighted efficiency is the highest due to the flat behavior of the efficiency with the output power. The analyzed single stage topologies have higher cost than the other analyzed solutions and control is expected to be more complex to avoid dc current injection. In addition, DCM operation mode allows smaller solutions, including a solution with dual ground capability, but efficiency is lower due to the high RMS currents.

 

Performance Enhancement of Actively Controlled Hybrid DC Microgrid Incorporating Pulsed Load

 

ABSTRACT:

In this paper, a new energy control scheme is proposed for actively controlled hybrid dc microgrid to reduce the adverse impact of pulsed power loads. The proposed energy control is an adaptive current-voltage control (ACVC) scheme based on the moving average measurement technique and an adaptive proportional compensator. Unlike conventional energy control methods, the proposed ACVC approach has the advantage of controlling both voltage and current of the system while keeping the output current of the power converter at a relatively constant value. For this study, a laboratory scale hybrid dc microgrid is developed to evaluate the performance of the ACVC strategy and to compare its performance with the other conventional energy control methods. Using experimental test results, it is shown that the proposed strategy highly improves the dynamic performance of the hybrid dc microgrid. Although the ACVC technique causes slightly more bus voltage variation, it effectively eliminates the high current and power pulsation of the power converters. The experimental test results for different pulse duty ratios demonstrated a significant improvement achieved by the developed ACVC scheme in enhancing the system efficiency, reducing the ac grid voltage drop and the frequency fluctuations.

 KEYWORDS:

  1. Hybrid dc microgrid
  2. Energy control system
  3. Pulse load
  4. Supercapacitor
  5. Active hybrid power source

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

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 Fig. 1. Schematic diagram of the hybrid dc microgrid under study

EXPECTED SIMULATION RESULTS:

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Fig. 2: Experimental test results of ACVC and CACC technique during constant pulse load operation.

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 Fig. 3: Experimental test results of CACC method and ACVC technique when pulse load frequency changes from 0.1-Hz to 0.2-Hz and its duty ratio increased from 20% to 40%.

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Fig. 4: Variation of the normalized average dc bus voltage and the kv in the proposed ACVC technique when pulse load frequency changes from 0.1-Hz to 0.2-Hz and its duty ratio increased from 20% to 40%.

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Fig. 5: Experimental test results of CACC method and ACVC technique when pulse load changed from 2-kW to 3-kW.

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Fig. 6: Hybrid DC microgrid performance comparison when ACVC, LBVC and IPC methods are utilized.

CONCLUSION:

In this paper, a new energy control scheme was developed to reduce the adverse impact of pulsed power loads. The proposed energy control was an adaptive current-voltage control (ACVC) scheme based on the moving average current and voltage measurement and a proportional voltage compensator. The performance of the developed ACVC technique was experimentally evaluated and it was compared to the other common energy control methods.

The test results showed that the ACVC scheme has a similar performance with the continuous average current control (CACC) method during a constant pulsed power load operation. However, the transient response of the ACVC technique during pulse load variation was effectively improved and it prevented any steady state voltage error or dangerous over voltage.

Also, the performance of the developed ACVC technique was compared with the limit-based voltage control (LBVC) and instantaneous power control (IPC) methods for different pulse rates and duty ratios. The comparative analysis showed that although the maximum dc bus voltage variation in the case of ACVC scheme was higher than the IPC and LBVC methods, the proposed ACVC technique required smaller power capacity of the converter and energy resources. Moreover, the developed ACVC method effectively eliminated the power pulsation of the slack bus generator and frequency fluctuation of the interconnected AC grid while the ac bus voltage drop was well reduced. Additionally, the efficiency analysis for different pulse duty ratios showed that the developed ACVC method considerably improved the efficiency of the system since the maximum current of the converter was reduced and the converter was operating at a relatively constant value.

 REFERENCES:

[1] M. E. Baran and N. R. Mahajan, “DC Distribution for industrial systems: opportunities and challenges,” IEEE Trans. on industrial applications, vol. 39, no. 6, pp. 1596-1601, November/December 2003.

[2] M. Farhadi, A. Mohamed and O. Mohammed, “Connectivity and Bidirectional Energy Transfer in DC Microgrid Featuring Different  Voltage Characteristics,” Green Technologies Conference, 2013 IEEE, vol., no., pp.244-249, 4-5 April 2013.

[3] D. Salomonsson, L.Soder, A. Sannino, “An Adaptive Control System for a Dc Microgrid for Data Centers,” Industry Applications Conference, 2007. 42nd IAS Annual Meeting. Conference Record of the 2007 IEEE, vol., no., pp.2414,2421, 23-27 Sept. 2007.

[4] M. Falahi, B K.L. utler-Purry and M. Ehsani, “Reactive Power Coordination of Shipboard Power Systems in Presence of Pulsed Loads,” Power Systems, IEEE Transactions on, vol.28, no.4, pp.3675-3682, Nov. 2013.

[5] M. Farhadi, and O. Mohammed, “Realtime operation and harmonic analysis of isolated and non-isolated hybrid DC microgrid,” Industry Applications Society Annual Meeting, 2013 IEEE , vol., no., pp.1,6, 6-11 Oct. 2013.