http://finalyearprojects.net

Checking delivery availability...

background-sm
Search
3
10 10 Updates found with power quality improvement using four leg three level npc inverter

Updates found with 'power quality improvement using four leg three level npc inverter'

Page 1 1

Updates found with ''

 ELECTRONICS  ABSTRACTHYBRID ENERGY STORAGE SYSTEM MICRO GRIDS INTEGRATION FOR POWER QUALITY IMPROVEMENT USING FOUR LEG THREE LEVEL NPC INVERTER AND SECOND ORDER SLIDING MODE CONTROL Introduction:-            Increasing penetration of DG is changing management of the grid from centralized to decentralized schemes, creating several challenges that must be carefully addressed in order to keep the electrical grid’s proper operation. High penetration of renewable energy can lead to stability and power quality issues due to the stochastic nature of RES, such as wind and solar energy.          The micro grid concept, which can be defined as a small scale weak electrical grid that is able to operate both in connected and islanded mode, has been extensively studied as a solution for RES integration. The weak nature of a micro grid implies the use of an Energy Storage System (ESS) to increase RES penetration and insure its stability.Proposed system:-              A second order sliding mode controller is proposed for the power flow control of a HESS, using a Four Leg Three Level Neutral Point Clamped (4-Leg 3LNPC) inverter as the only interface between the RES/HESS and the microgrid. The use of a 4-Leg 3L-NPC power converter topology to interface a RES with a HESS in a microgrid context has been investigated. By adding the fourth leg to a 3L-NPC converter and using a new DC side control strategy it is possible to reach both fast and efficient DC power sharing between the two ESSS and the RES, and at the same time improve the AC side power quality. The main contribution lays in the DC power flow controller which allows HESS power flow control and DC current harmonics suppression.             A three-dimensional space vector modulation and a sequence decomposition based AC side control allows the inverter to work in unbalanced load conditions while maintaining a balanced AC voltage at the point of common coupling. DC current harmonics caused by unbalanced load and the NPC floating middle point voltage, together with the power division limits.Advantages:-•	Improved power quality.•	 Better stability.Applications:-•	Power conversion applications.
IEEE 2017-2018 POWER ELECTRONICS ABSTRACTHYBRID ENERGY STORAGE SYSTEM MICRO GRIDS INTEGRATION FOR POWER QUALITY IMPROVEMENT USING FOUR LEG THREE LEVEL NPC INVERTER AND SECOND ORDER SLIDING MODE CONTROL Introduction:- Increasing penetration of DG is changing management of the grid from centralized to decentralized schemes, creating several challenges that must be carefully addressed in order to keep the electrical grid’s proper operation. High penetration of renewable energy can lead to stability and power quality issues due to the stochastic nature of RES, such as wind and solar energy. The micro grid concept, which can be defined as a small scale weak electrical grid that is able to operate both in connected and islanded mode, has been extensively studied as a solution for RES integration. The weak nature of a micro grid implies the use of an Energy Storage System (ESS) to increase RES penetration and insure its stability.Proposed system:- A second order sliding mode controller is proposed for the power flow control of a HESS, using a Four Leg Three Level Neutral Point Clamped (4-Leg 3LNPC) inverter as the only interface between the RES/HESS and the microgrid. The use of a 4-Leg 3L-NPC power converter topology to interface a RES with a HESS in a microgrid context has been investigated. By adding the fourth leg to a 3L-NPC converter and using a new DC side control strategy it is possible to reach both fast and efficient DC power sharing between the two ESSS and the RES, and at the same time improve the AC side power quality. The main contribution lays in the DC power flow controller which allows HESS power flow control and DC current harmonics suppression. A three-dimensional space vector modulation and a sequence decomposition based AC side control allows the inverter to work in unbalanced load conditions while maintaining a balanced AC voltage at the point of common coupling. DC current harmonics caused by unbalanced load and the NPC floating middle point voltage, together with the power division limits.Advantages:-• Improved power quality.• Better stability.Applications:-• Power conversion applications.
Send Enquiry
Read More
 ELECTRONICS PROJECT TITLES Hybrid Energy Storage System MicroGrids Integration For Power Quality Improvement Using Four Leg Three Level NPC Inverter and Second Order Sliding Mode ControlAbstract— Rising demand for distributed generation based on Renewable Energy Sources (RES) has led to several issues in the operation of utility grids. The microgrid is a promising solution to solve these problems. A dedicated energy storage system could contribute to a better integration of RES into the microgrid by smoothing the renewable resource’s intermittency, improving the quality of the injected power and enabling additional services like voltage and frequency regulation. However, due to energy/power technological limitations, it is oftennecessary to use Hybrid Energy Storage Systems (HESS). In this paper, a second order sliding mode controller is proposed for the power flow control of a HESS, using a Four Leg Three Level Neutral Point Clamped (4-Leg 3LNPC) inverter as the only interface between the RES/HESSand the microgrid. A three-dimensional space vector modulation and a sequence decomposition based AC side control allows the inverter to work in unbalanced load conditions while maintaining a balanced AC voltage at the point of common coupling. DC current harmonics caused by unbalanced load and the NPC floating middle pointvoltage, together with the power division limits are carefully addressed in this paper. The effectiveness of the proposed technique for the HESS power flow control is compared to a classical PI control scheme and is proventhrough simulations and experimentally using a 4 Leg 3LNPC prototype on a test bench.CONTACT:GANESAN.P+91 9865862045+91 8903410319
IEEE 2017 - 18 POWER ELECTRONICS PROJECT TITLES Hybrid Energy Storage System MicroGrids Integration For Power Quality Improvement Using Four Leg Three Level NPC Inverter and Second Order Sliding Mode ControlAbstract— Rising demand for distributed generation based on Renewable Energy Sources (RES) has led to several issues in the operation of utility grids. The microgrid is a promising solution to solve these problems. A dedicated energy storage system could contribute to a better integration of RES into the microgrid by smoothing the renewable resource’s intermittency, improving the quality of the injected power and enabling additional services like voltage and frequency regulation. However, due to energy/power technological limitations, it is oftennecessary to use Hybrid Energy Storage Systems (HESS). In this paper, a second order sliding mode controller is proposed for the power flow control of a HESS, using a Four Leg Three Level Neutral Point Clamped (4-Leg 3LNPC) inverter as the only interface between the RES/HESSand the microgrid. A three-dimensional space vector modulation and a sequence decomposition based AC side control allows the inverter to work in unbalanced load conditions while maintaining a balanced AC voltage at the point of common coupling. DC current harmonics caused by unbalanced load and the NPC floating middle pointvoltage, together with the power division limits are carefully addressed in this paper. The effectiveness of the proposed technique for the HESS power flow control is compared to a classical PI control scheme and is proventhrough simulations and experimentally using a 4 Leg 3LNPC prototype on a test bench.CONTACT:GANESAN.P+91 9865862045+91 8903410319
Send Enquiry
Read More
 ELECTRONICS ABSTRACT QUASI CASCADED H-BRIDGE FIVE-LEVELBOOST INVERTERIntroduction:-         Multilevel inverters have recently received many attentions from researchers due to their advantages over the conventional three-level pulse-width modulation (PWM) inverters. The advantages of the multilevel inverters are as follows: improved quality output waveforms with lower total harmonic distortion (THD), smaller filter size and lower electromagnetic interface (EMI). Three general multilevel inverter topologies are: flying capacitors, neutral point clamped (NPC), and cascaded H-bridge (CHB) inverters. Among these topologies, the CHB inverter has unique advantages in modularity and its contribution of high power. These advantages make the CHB inverter an attractive option for many applications such as uninterruptible power supplies.Existing system:-            The conventional two-stage CHB boost-five-level inverter (CHB-BFLI). Two capacitors, two boost inductors, two diodes, ten switches, one filter inductor and a resistive load are utilized in the conventional CHB-BFLI. The boost DC-DC converter is used to control the DC-link voltage on each H-bridge circuit.            Both the top and bottom switches in the same leg cannot be switched on simultaneously because the DC-link capacitor is connected to each leg in parallel. And a dead-time between two switches in the leg must be used to avoid short circuit in the DC source.Proposed system:-            Novel single-stage quasi-cascaded H-bridge five-level boost inverter (qchb-FLBI) is proposed . The proposed inverter consists of two separate DC sources, two quasi-boost inverter (qBI) modules and an inductor filter connected to the resistive load in series. Each qBI module contains one capacitor, one boost inductor, four switches and two diodes. A phase-shifted sinusoidal  pulse-width modulation (PS-SPWM) strategy for the proposed QCHB-FLBI. For module 1, two control voltages, -vcontrol and vcontrol are compared to a high-frequency triangle voltage, Vtri1, to produce control signals for the S1 and S2 switches. The proposed five-level inverter has the advantages over the cascaded H-bridge quasi-Z-source inverter (CHB-qzsi) in cutting down passive components. In the CHB-qZSI, the operating frequency of the inductors is twofold the switching frequency. Therefore, the high-frequency current ripple on inductors of the proposed qCHB-FLBI is a half that of the CHB-qZSI.Advantages:-•	Five-level output voltage with boost voltage ability, •	reduction in a number of passive components •	And shoot-through immunity.Applications:-•	High power conversion applications.
IEEE 2017-2018 POWER ELECTRONICS ABSTRACT QUASI CASCADED H-BRIDGE FIVE-LEVELBOOST INVERTERIntroduction:- Multilevel inverters have recently received many attentions from researchers due to their advantages over the conventional three-level pulse-width modulation (PWM) inverters. The advantages of the multilevel inverters are as follows: improved quality output waveforms with lower total harmonic distortion (THD), smaller filter size and lower electromagnetic interface (EMI). Three general multilevel inverter topologies are: flying capacitors, neutral point clamped (NPC), and cascaded H-bridge (CHB) inverters. Among these topologies, the CHB inverter has unique advantages in modularity and its contribution of high power. These advantages make the CHB inverter an attractive option for many applications such as uninterruptible power supplies.Existing system:- The conventional two-stage CHB boost-five-level inverter (CHB-BFLI). Two capacitors, two boost inductors, two diodes, ten switches, one filter inductor and a resistive load are utilized in the conventional CHB-BFLI. The boost DC-DC converter is used to control the DC-link voltage on each H-bridge circuit. Both the top and bottom switches in the same leg cannot be switched on simultaneously because the DC-link capacitor is connected to each leg in parallel. And a dead-time between two switches in the leg must be used to avoid short circuit in the DC source.Proposed system:- Novel single-stage quasi-cascaded H-bridge five-level boost inverter (qchb-FLBI) is proposed . The proposed inverter consists of two separate DC sources, two quasi-boost inverter (qBI) modules and an inductor filter connected to the resistive load in series. Each qBI module contains one capacitor, one boost inductor, four switches and two diodes. A phase-shifted sinusoidal pulse-width modulation (PS-SPWM) strategy for the proposed QCHB-FLBI. For module 1, two control voltages, -vcontrol and vcontrol are compared to a high-frequency triangle voltage, Vtri1, to produce control signals for the S1 and S2 switches. The proposed five-level inverter has the advantages over the cascaded H-bridge quasi-Z-source inverter (CHB-qzsi) in cutting down passive components. In the CHB-qZSI, the operating frequency of the inductors is twofold the switching frequency. Therefore, the high-frequency current ripple on inductors of the proposed qCHB-FLBI is a half that of the CHB-qZSI.Advantages:-• Five-level output voltage with boost voltage ability, • reduction in a number of passive components • And shoot-through immunity.Applications:-• High power conversion applications.
Send Enquiry
Read More
TRONICS ABSTRACT:A FAMILY OF FIVE-LEVEL DUAL-BUCK FULL-BRIDGE INVERTERS FOR GRID-TIED APPLICATIONS ABSTRACT:                         The demand for renewable generation has increased significantly over the past years because of the consideration on fossil fuel shortage and greenhouse effect. Among various types of renewable generation, photovoltaic generation, wind generation, and fuel cells have been widely utilized, and the grid-tied inverters are key elements in renewable generation systems to interface the renewable sources and the utility grid. Therefore, they should be careful designed to achieve high efficiency and high power density.EXISTING SYSTEM:	A five-level H-bridge inverter topology was proposed by introducing a neutral point clamped bi-directional switch (NPC branch) based on the conventional full-bridge inverter. Compared with the DNPC five-level inverter topology, the FCC five-level inverter topology, and the ANPC five-level inverter topology, the number of power devices in the new five-level H-bridge inverter has been reduced significantly. Therefore, for the low-voltage (less than 1000 V) applications, this five-level H-bridge inverter topology is a better option than conventional multilevel inverter topologies. It is regarded as one of the best solutions for grid-tied inverters. The issue of neutral point (NP) potential balancing was discussed as well, and the NP potential self balancing of two capacitors was considered to be automatically realized. However, the NP potential self-balancing of five-level full-bridge inverters is related to the modulation index. PROPOSED SYSTEM:	A three-level DBFBI can be combined with a two-level half-bridge inverter by employing the topology generation rule #2. The nodes of the threelevel DBHBI, P1, N1, and O1, are connected to the nodes P2, N2, and O2, respectively. The node of the three-level DBHBI O1 is disconnected from thenode of the utility grid n1. The node of the two-level half-bridge inverter O2 is disconnected from the node of the utility grid n2. Then, the nodes n1 and n2 are connected to each other. The redundant capacitors Cdc1 and Cdc2 and the redundant inductor L3 are removed. Therefore, the NPC five-level DBFBI topology can be derived from the two generation rules mentioned above. Compared with the three-level DBFBI topology, there are two additional switches and two additional diodes in the proposed NPC five-level DBFBI topology.  ADVANTAGES:•	fast switching•	low switching loss •	resistive conduction voltage drop•	no reverse recovery problem occurs in the freewheeling mode
IEEE 2016 POWER ELECTRONICS ABSTRACT:A FAMILY OF FIVE-LEVEL DUAL-BUCK FULL-BRIDGE INVERTERS FOR GRID-TIED APPLICATIONS ABSTRACT: The demand for renewable generation has increased significantly over the past years because of the consideration on fossil fuel shortage and greenhouse effect. Among various types of renewable generation, photovoltaic generation, wind generation, and fuel cells have been widely utilized, and the grid-tied inverters are key elements in renewable generation systems to interface the renewable sources and the utility grid. Therefore, they should be careful designed to achieve high efficiency and high power density.EXISTING SYSTEM: A five-level H-bridge inverter topology was proposed by introducing a neutral point clamped bi-directional switch (NPC branch) based on the conventional full-bridge inverter. Compared with the DNPC five-level inverter topology, the FCC five-level inverter topology, and the ANPC five-level inverter topology, the number of power devices in the new five-level H-bridge inverter has been reduced significantly. Therefore, for the low-voltage (less than 1000 V) applications, this five-level H-bridge inverter topology is a better option than conventional multilevel inverter topologies. It is regarded as one of the best solutions for grid-tied inverters. The issue of neutral point (NP) potential balancing was discussed as well, and the NP potential self balancing of two capacitors was considered to be automatically realized. However, the NP potential self-balancing of five-level full-bridge inverters is related to the modulation index. PROPOSED SYSTEM: A three-level DBFBI can be combined with a two-level half-bridge inverter by employing the topology generation rule #2. The nodes of the threelevel DBHBI, P1, N1, and O1, are connected to the nodes P2, N2, and O2, respectively. The node of the three-level DBHBI O1 is disconnected from thenode of the utility grid n1. The node of the two-level half-bridge inverter O2 is disconnected from the node of the utility grid n2. Then, the nodes n1 and n2 are connected to each other. The redundant capacitors Cdc1 and Cdc2 and the redundant inductor L3 are removed. Therefore, the NPC five-level DBFBI topology can be derived from the two generation rules mentioned above. Compared with the three-level DBFBI topology, there are two additional switches and two additional diodes in the proposed NPC five-level DBFBI topology. ADVANTAGES:• fast switching• low switching loss • resistive conduction voltage drop• no reverse recovery problem occurs in the freewheeling mode
Send Enquiry
Read More
 ELECTRONICS ABSTRACTA NEW SIX-SWITCH FIVE-LEVEL ACTIVE NEUTRAL POINT CLAMPED INVERTER FOR PV APPLICATIONSIntroduction:-           Multilevel inverters have received increased attention in both academia and industry nowadays as one of the optimal solutions of power conversion for medium- and high power applications. For medium-power application, the motivation for the use of multilevel inverters is to reduce the switch voltage stress as well as the output filter size.           They also have the advantages of improved output quality, lower total harmonic distortion (THD), lower common-mode voltage, and lower electromagnetic interference in contrast to their two-level counterparts. Furthermore, the multilevel inverters have possibility to achieve higher efficiency over the conventional inverters due to the use of low-voltage drop devices, leading to their low-voltage application such as photovoltaic (PV) cells.Existing system:-         The NPC-type multilevel inverters generate the voltage levels from the neutral point voltage by adopting the clamping diodes. However, when voltage levels increase, more clamping diodes, active semiconductor switches, and dc-link capacitors are needed.            Excessive number of clamping diodes is connected in series to block the higher voltage, thus producing more conduction losses and generating reverse recovery currents that affect the switching losses of other devices. The dc-link voltage balancing problem is another issue for higher levels NPC inverters.             As another type of classic multilevel inverters, the FC inverter produces the required output voltage levels by summing the FC- and dc-link voltages. The increased number of capacitors in higher levels leads to complex control method to balance the voltages of both dc-link capacitors and FCs. The higher switching frequency to keep the capacitors properly balanced and capacitors maintenance costs result in the less industrial penetration of FC type.Dis-advantages:-•	More cells are needed.•	Capacitors maintenance costs result in the less industrial penetration of FC type.Proposed system:-           A novel six-switch five-level active NPC (6S-5L-ANPC) inverter provides an acceptable compromise between cost and performance inverter topology has been proposed. As compared with the conventional 5L-ANPC inverter, it requires only six switches for a single phase, a reduction from eight switches. The specific modulation strategy of 6S-5L-ANPC inverter under reactive power operation has been proposed.                The 6S-5L-ANPC inverter consists of eight switching states that generate five-level voltage levels at the output based on capacitor voltages. The output current is defined as iout. Vout represents the output voltage level.  Eight different switching states (state A to H) and current paths (the red line shows the active current path while the green line represents the reactive power path).Advantages:-•	The efficiency of the proposed 6S-5L-ANPC inverter is higher.•	 Its conduction loss is lower.Applications:-•	High-power factor applications.
IEEE 2017-2018 POWER ELECTRONICS ABSTRACTA NEW SIX-SWITCH FIVE-LEVEL ACTIVE NEUTRAL POINT CLAMPED INVERTER FOR PV APPLICATIONSIntroduction:- Multilevel inverters have received increased attention in both academia and industry nowadays as one of the optimal solutions of power conversion for medium- and high power applications. For medium-power application, the motivation for the use of multilevel inverters is to reduce the switch voltage stress as well as the output filter size. They also have the advantages of improved output quality, lower total harmonic distortion (THD), lower common-mode voltage, and lower electromagnetic interference in contrast to their two-level counterparts. Furthermore, the multilevel inverters have possibility to achieve higher efficiency over the conventional inverters due to the use of low-voltage drop devices, leading to their low-voltage application such as photovoltaic (PV) cells.Existing system:- The NPC-type multilevel inverters generate the voltage levels from the neutral point voltage by adopting the clamping diodes. However, when voltage levels increase, more clamping diodes, active semiconductor switches, and dc-link capacitors are needed. Excessive number of clamping diodes is connected in series to block the higher voltage, thus producing more conduction losses and generating reverse recovery currents that affect the switching losses of other devices. The dc-link voltage balancing problem is another issue for higher levels NPC inverters. As another type of classic multilevel inverters, the FC inverter produces the required output voltage levels by summing the FC- and dc-link voltages. The increased number of capacitors in higher levels leads to complex control method to balance the voltages of both dc-link capacitors and FCs. The higher switching frequency to keep the capacitors properly balanced and capacitors maintenance costs result in the less industrial penetration of FC type.Dis-advantages:-• More cells are needed.• Capacitors maintenance costs result in the less industrial penetration of FC type.Proposed system:- A novel six-switch five-level active NPC (6S-5L-ANPC) inverter provides an acceptable compromise between cost and performance inverter topology has been proposed. As compared with the conventional 5L-ANPC inverter, it requires only six switches for a single phase, a reduction from eight switches. The specific modulation strategy of 6S-5L-ANPC inverter under reactive power operation has been proposed. The 6S-5L-ANPC inverter consists of eight switching states that generate five-level voltage levels at the output based on capacitor voltages. The output current is defined as iout. Vout represents the output voltage level. Eight different switching states (state A to H) and current paths (the red line shows the active current path while the green line represents the reactive power path).Advantages:-• The efficiency of the proposed 6S-5L-ANPC inverter is higher.• Its conduction loss is lower.Applications:-• High-power factor applications.
Send Enquiry
Read More
 ELECTRONICS ABSTRACTA FAMILY OF NEUTRAL-POINT-CLAMPED CIRCUITS OF SINGLE-PHASE PV INVERTERS: GENERALIZED PRINCIPLE AND IMPLEMENTATIONIntroduction:-             The grid-connected photovoltaic (PV) inversion system, high efficiency, high performance, and low cost are the three main targets pursuing. Traditionally, a line-frequency or high-frequency transformer is employed in the PV inverter to isolate the grid from the PV source to attenuate the common mode Leakage current and step up the output voltage. However, the transformer will unavoidably reduce the operational efficiency and increase the system cost and size. Therefore, the transformer less PV inverters is now attracting much more attention.                The main problem of transformer less PV Inverter is that it has no galvanic isolation and then the common mode leakage current can flow through the parasitic capacitor between ground and PV array, which will threaten people safety and cause other severe problems. To attenuate the common-mode leakage current in transformer less inverter, the most effective solution is to keep the common-mode voltage constant.Existing system:-            Several single-phase topologies have been proposed to maintain the common-mode voltage constant as half of dc-bus voltage, for example, H5, HERIC, and H6 topologies. However, the common-mode voltage is indeed variable during the freewheeling stage because of the potential variation induced by charging and discharging the switch junction capacitance.           Thus, the leakage current still exists in the common-mode circuit. Besides, few neutral-point-clamped (NPC) circuits have been proposed to effectively clamp the common-mode voltage to be half of dc-bus voltage during the whole fundamental period. These NPC topologies are mainly applicable in the transformer less PV generation systems with the required low-level leakage current.                 These inverters can use the auxiliary switches and diodes to provide the additional freewheeling path to make the common-mode voltage constant during the whole fundamental period in theory. However, because of the charging and discharging of switch junction capacitances between the freewheeling modes and the energy transferring modes, the common-mode voltage is indeed not constantDis-advantages:-•	Leakage loss.•	Common-mode voltage is indeed not constant.Proposed system:-          Two types of NPC single-phase PV inverters are proposed by using the unidirectional and bidirectional clamping circuits. The specific NPC circuits in single-phase PV inverters, where two types of single-phase NPC inverters are fully analyzed. Doing so, the common-mode voltage of single phase inverter can be effectively maintained constant as half of dc-link voltage.                 Two unidirectional clamping Circuits should be combined together to form a bidirectional freewheeling path. Using the unidirectional clamping circuits, which make up a type of NPC single-phase inverters, where two kinds of unidirectional clamping circuits. For cases, where the grid voltage is distorted, the common mode behaviors of the presented NPC inverters will not be influenced, because the fundamental frequency and the low order harmonics’ frequencies of grid voltage are far smaller than the switching frequency. When the output power factor is not unity, the presented NPC inverters can still work properly with the constant common-mode voltage obtained, which can be concluded by specifically analyzing the freewheeling modes.Advantages:-•	The freewheeling behaviour can still effectively maintain the common-mode voltage constant.•	High efficiency and low loss.Applications:-•	Grid applications.
IEEE 2017-2018 POWER ELECTRONICS ABSTRACTA FAMILY OF NEUTRAL-POINT-CLAMPED CIRCUITS OF SINGLE-PHASE PV INVERTERS: GENERALIZED PRINCIPLE AND IMPLEMENTATIONIntroduction:- The grid-connected photovoltaic (PV) inversion system, high efficiency, high performance, and low cost are the three main targets pursuing. Traditionally, a line-frequency or high-frequency transformer is employed in the PV inverter to isolate the grid from the PV source to attenuate the common mode Leakage current and step up the output voltage. However, the transformer will unavoidably reduce the operational efficiency and increase the system cost and size. Therefore, the transformer less PV inverters is now attracting much more attention. The main problem of transformer less PV Inverter is that it has no galvanic isolation and then the common mode leakage current can flow through the parasitic capacitor between ground and PV array, which will threaten people safety and cause other severe problems. To attenuate the common-mode leakage current in transformer less inverter, the most effective solution is to keep the common-mode voltage constant.Existing system:- Several single-phase topologies have been proposed to maintain the common-mode voltage constant as half of dc-bus voltage, for example, H5, HERIC, and H6 topologies. However, the common-mode voltage is indeed variable during the freewheeling stage because of the potential variation induced by charging and discharging the switch junction capacitance. Thus, the leakage current still exists in the common-mode circuit. Besides, few neutral-point-clamped (NPC) circuits have been proposed to effectively clamp the common-mode voltage to be half of dc-bus voltage during the whole fundamental period. These NPC topologies are mainly applicable in the transformer less PV generation systems with the required low-level leakage current. These inverters can use the auxiliary switches and diodes to provide the additional freewheeling path to make the common-mode voltage constant during the whole fundamental period in theory. However, because of the charging and discharging of switch junction capacitances between the freewheeling modes and the energy transferring modes, the common-mode voltage is indeed not constantDis-advantages:-• Leakage loss.• Common-mode voltage is indeed not constant.Proposed system:- Two types of NPC single-phase PV inverters are proposed by using the unidirectional and bidirectional clamping circuits. The specific NPC circuits in single-phase PV inverters, where two types of single-phase NPC inverters are fully analyzed. Doing so, the common-mode voltage of single phase inverter can be effectively maintained constant as half of dc-link voltage. Two unidirectional clamping Circuits should be combined together to form a bidirectional freewheeling path. Using the unidirectional clamping circuits, which make up a type of NPC single-phase inverters, where two kinds of unidirectional clamping circuits. For cases, where the grid voltage is distorted, the common mode behaviors of the presented NPC inverters will not be influenced, because the fundamental frequency and the low order harmonics’ frequencies of grid voltage are far smaller than the switching frequency. When the output power factor is not unity, the presented NPC inverters can still work properly with the constant common-mode voltage obtained, which can be concluded by specifically analyzing the freewheeling modes.Advantages:-• The freewheeling behaviour can still effectively maintain the common-mode voltage constant.• High efficiency and low loss.Applications:-• Grid applications.
Send Enquiry
Read More
STRACT  2016-2017 EFFECTIVE VOLTAGE BALANCE CONTROL FOR BIPOLAR-DC-BUS FED EV CHARGING STATION WITH THREE-LEVEL DC-DC FAST CHARGER The development of high-power charging stations with fast chargers is a promising solution to shorten the charging time for electric vehicles (EVs). The neutral-point-clamped (NPC) converter based bipolar-dc-bus fed charging station brings manymer its, but it has inherent voltage balance limits. To solve this issue, a voltage balance control (VBC) method based on a new modulation together with three-level (TL) dc-dc converter based fast charger is proposed. Additionally, an effective VBC coordination between the TL dc-dc converter and NPC converter is formulated. Through the proposed VBC coordination, the controllable balancing region is extended so that additional balancing circuits are eliminated. Meanwhile, the grid-side currents quality is improved as the NPC converter has more      free Dom to control currents. The low-frequency voltage fluctuations in dcbuses are removed because the TL dc-dc converter performs most of the balancing tasks. Faster VBC perturbation performance is achieved due to higher available balancing current at TL dc-dc converter side. In addition, the voltage balance limits of both the TL dc-dc converter and the NPC converter are explored. The voltage balancing performances are compared when VBC is located at different sides. Simulation and experimental results are provided to verify the proposed VBC and the VBC coordination.
POWER ELECTRONICS ABSTRACT 2016-2017 EFFECTIVE VOLTAGE BALANCE CONTROL FOR BIPOLAR-DC-BUS FED EV CHARGING STATION WITH THREE-LEVEL DC-DC FAST CHARGER The development of high-power charging stations with fast chargers is a promising solution to shorten the charging time for electric vehicles (EVs). The neutral-point-clamped (NPC) converter based bipolar-dc-bus fed charging station brings manymer its, but it has inherent voltage balance limits. To solve this issue, a voltage balance control (VBC) method based on a new modulation together with three-level (TL) dc-dc converter based fast charger is proposed. Additionally, an effective VBC coordination between the TL dc-dc converter and NPC converter is formulated. Through the proposed VBC coordination, the controllable balancing region is extended so that additional balancing circuits are eliminated. Meanwhile, the grid-side currents quality is improved as the NPC converter has more free Dom to control currents. The low-frequency voltage fluctuations in dcbuses are removed because the TL dc-dc converter performs most of the balancing tasks. Faster VBC perturbation performance is achieved due to higher available balancing current at TL dc-dc converter side. In addition, the voltage balance limits of both the TL dc-dc converter and the NPC converter are explored. The voltage balancing performances are compared when VBC is located at different sides. Simulation and experimental results are provided to verify the proposed VBC and the VBC coordination.
Send Enquiry
Read More
 ELECTRONICS ABSTRACT A SINGLE-PHASE TRANSFORMER LESS INVERTER WITH CHARGE PUMP CIRCUIT CONCEPT FOR GRID-TIED PV APPLICATIONS Introduction:- The photovoltaic (PV) power systems have become very popular among the renewable energy sources, because they generate electricity with no moving parts, operate quietly with no emissions, and require little maintenance. Distributed grid-connected pvs are playing an increasingly role as an integral part of the electrical grid. However, due to the large stray capacitors between the PV panels and the ground, PV systems suffer from a high common mode (CM) current, which reduces the system efficiency and may cause safety issues like electric shock. In order to eliminate the leakage currents, transformers are commonly used in the PV system to provide galvanic isolation. However, it possesses undesirable properties including large size, high cost, and weight with additional losses. Thus, eliminating the transformer is a great benefit to further improve the overall system efficiency, reduce the size, and weight. Existing system:-               Topologies based on H6 are proposed to eliminate the leakage current of the grid-tied PV application. These inverters consist of six power switches and some diodes for disconnecting the dc side from the grid. These topologies are more costly than the FB inverter, because they use extra switches and diodes. Another disadvantage of these topologies is lower efficiency due to the current that circulates through three power switches at the same time. Several high efficient new H6 transformer less inverters are proposed to achieve lightweight and also lower cost. They have the capability of reactive power injection to the grid. The leakage current is not totally eliminated in these topologies, which is the main disadvantage of them. Dis-advantages:- •	Leakage losses. •	Less efficiency Proposed system:-            A new transformerless inverter based on charge pump circuit concept, which eliminates the leakage current of the grid-connected PV systems using a unipolar sinusoidal pulse width modulation (SPWM) technique. In this Solution, the neutral of the grid is directly connected to the negative terminal of the charge pump circuit, so the voltage across the parasitic capacitor is connected to zero and the leakage current is eliminated. The charge pump circuit is implemented to generate negative output voltage.             There is not any limitation on the modulation strategy of the proposed inverter because the leakage current is eliminated by the circuit topology. The proposed topology consists of only four power switches, so the cost of the semiconductors is reduced and the power quality is improved by three-level output voltage in order to reduce the output current ripple. During operation of the proposed inverter, the current flows through two switches; thus, the conduction loss is also lower. The used dc voltage of the proposed inverter is the same as the FB inverter (unlike NPC, ANPC, and half-bridge (HB) inverters). The proposed inverter is capable of delivering reactive power into grid too.Advantages:-•	The charge pump circuit has no active device and it has a lower cost for grid-tied applications.•	The capacitor of the proposed inverter charges every switching cycle, which reduces the size of the required capacitor with the switching frequency.Applications:-•	Grid applications.
IEEE 2017-2018 POWER ELECTRONICS ABSTRACT A SINGLE-PHASE TRANSFORMER LESS INVERTER WITH CHARGE PUMP CIRCUIT CONCEPT FOR GRID-TIED PV APPLICATIONS Introduction:- The photovoltaic (PV) power systems have become very popular among the renewable energy sources, because they generate electricity with no moving parts, operate quietly with no emissions, and require little maintenance. Distributed grid-connected pvs are playing an increasingly role as an integral part of the electrical grid. However, due to the large stray capacitors between the PV panels and the ground, PV systems suffer from a high common mode (CM) current, which reduces the system efficiency and may cause safety issues like electric shock. In order to eliminate the leakage currents, transformers are commonly used in the PV system to provide galvanic isolation. However, it possesses undesirable properties including large size, high cost, and weight with additional losses. Thus, eliminating the transformer is a great benefit to further improve the overall system efficiency, reduce the size, and weight. Existing system:- Topologies based on H6 are proposed to eliminate the leakage current of the grid-tied PV application. These inverters consist of six power switches and some diodes for disconnecting the dc side from the grid. These topologies are more costly than the FB inverter, because they use extra switches and diodes. Another disadvantage of these topologies is lower efficiency due to the current that circulates through three power switches at the same time. Several high efficient new H6 transformer less inverters are proposed to achieve lightweight and also lower cost. They have the capability of reactive power injection to the grid. The leakage current is not totally eliminated in these topologies, which is the main disadvantage of them. Dis-advantages:- • Leakage losses. • Less efficiency Proposed system:- A new transformerless inverter based on charge pump circuit concept, which eliminates the leakage current of the grid-connected PV systems using a unipolar sinusoidal pulse width modulation (SPWM) technique. In this Solution, the neutral of the grid is directly connected to the negative terminal of the charge pump circuit, so the voltage across the parasitic capacitor is connected to zero and the leakage current is eliminated. The charge pump circuit is implemented to generate negative output voltage. There is not any limitation on the modulation strategy of the proposed inverter because the leakage current is eliminated by the circuit topology. The proposed topology consists of only four power switches, so the cost of the semiconductors is reduced and the power quality is improved by three-level output voltage in order to reduce the output current ripple. During operation of the proposed inverter, the current flows through two switches; thus, the conduction loss is also lower. The used dc voltage of the proposed inverter is the same as the FB inverter (unlike NPC, ANPC, and half-bridge (HB) inverters). The proposed inverter is capable of delivering reactive power into grid too.Advantages:-• The charge pump circuit has no active device and it has a lower cost for grid-tied applications.• The capacitor of the proposed inverter charges every switching cycle, which reduces the size of the required capacitor with the switching frequency.Applications:-• Grid applications.
Send Enquiry
Read More
Page 1 1