Study and control of bipolar lvdc grid with dc symmetrical component method ijaerdv05i0126509

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International Journal of Advance Engineering and Research Development Volume 5, Issue 01, January -2018

STUDY AND CONTROL OF BIPOLAR LVDC GRID WITH DC SYMMETRICAL COMPONENT METHOD 1

Dr. CHANDRASHEKHAR REDDY S, 2G SARITHA, 3P RAMBABU 1

2

Professor, Department of EEE, CJIT, Yeshwanthapur, Warangal, T.S, India.

Assistant Professor, Department of EEE, CJIT, Yeshwanthapur, Warangal, T.S, India.

3 M.Tech Student, Department of EEE, CJIT, Yeshwanthapur, Warangal, T.S, India.

ABSTRACT: The power distribution network is going to be modified towards the long run, good Grid owing to hyperbolic number of put in renewable power generation units to fulfil the tightened environmental regulation. The control of the long run good Grid is going to be difficult due to the hyperbolic variety of renewable power generation units that are variable in nature, and at the same time, the purchaser's are extremely keen about uninterruptable, prime quality power provide. The Smart Grid management is intensively studied. It may be finished that the management could be easier and therefore the grid operation a lot of reliable if the AC grid would be replaced by DC grid. However, the elaborate energy efficiency analysis of the DC grid isn't completely studied. The potency and total period of time prices are the key parameters once the network house owners contemplate the future grid structure.

Keywords: Active damping, bipolar dc distribution, common mode, differential mode, symmetrical component 1. INTRODUCTION: This thesis addresses the factors that have an effect on the energy potency of the low voltage DC (LVDC) distribution network from power physical science perspective. The facility loss models for the converters and their AC filters are developed and verified by measurements. The impact on the converter topology, used power semiconductor switches, AC filter style and electrical device core material, DC network configuration, customer behavior, the necessity of DC voltage reconciliation in the bipolar DC network in addition because the grounding problems to fulfill the electrical safety standards are treated. For facilitating the look of price effective LVDC distribution networks, the whole power losses of the network with totally different configurations are evaluated and compared. It is unconcealed that the used filter electrical device core material has a vital impact on the facility losses of the LVDC distribution network. The electrical device core material having low high-frequency power loss characteristics, such as amorphous alloy, is usually recommended. The LVDC distribution network ought to be grounded to reduce the power losses whenever it's attainable in step with the native safety standardization and grounding conditions. The three-level government agency converters connected to 1500 VDC ought to be accustomed minimize the facility losses. The grid-frequency isolation electrical device is that the main power loss supply if the galvanic isolation is needed to isolate the ungrounded LVDC distribution network and also the grounded client electrical installations. In this case, the very best energy potency is achieved by using two- or three-level converters connected to 750 VDC if the DC cable's length is a smaller amount than 600 m. Otherwise; slightly higher energy potency is achieved by mistreatment three-level converters connected to 1500 VDC. Therefore, voltage transformation quantitative relation of the isolation the transformer should be 800V/400V rather than 400V/400V. Moreover, the potency of the facility converters is increased by mistreatment assails MOSFETs rather than conventional IGBTs as power semiconductor switches. The dc symmetrical part methodology is introduced for the analysis and management of bipolar dc distribution systems below asymmetrical operation. This methodology is an extension of the classical symmetrical part theory in three-phase ac power systems. As associate degree example, an increased common-mode voltage regulation theme is represented.

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 01, January-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406

Fig.1.1.Bipolar LVDC power distribution system.

2. PREVIOUS STUDY: It suppresses common-mode LC resonance by adding active damping management, and reduces common-mode impedance to enhance power quality and voltage stability. DC power delivery is return quality recently once it absolutely was quickly defeated by its ac opponent a century past. The foremost vital development was found in high voltage dc (HVDC) transmission systems, attributable to its advantage in power capacity and controllability over ac transmission lines. Now the trend of dc is increasing to rock bottom a part of the electrical provider chains, from transmission to distribution systems. It’s foretold that dc distribution may facilitate to accommodate the next penetration of renewable distributed generators (DGs), increase power capacity and quality, and supply larger resilience against power surge and irregular masses. The exploration of dc distribution technologies begins at the bottom voltage level. The main reason is that the relative maturity of low-tension dc (LVDC) electrical equipment, including power electronic converters and dc circuit breakers. Primary dc distribution systems are initially deployed for communication power provides, with a rated voltage of only forty-eight V [3]. This can be followed by transportation power systems, like those in additional electrical aircraft and ships. Correspondingly, the dc voltage level is scaled up to many hundred volts to handle the extended power vary. The most recent dc distribution initiatives are reaching for residential applications in inexperienced buildings and electric vehicle charging stations.

3. BIPOLAR LVDC DISTRIBUTION CONVERTER: The distribution converter is that the power hub of the complete LVDC grid. During this section, the converter topologies suitable for bipolar LVDC distribution area unit in short summarized. They’re the physical basis for the theoretical derivation in succeeding sections. The most straightforward approach to creating a converter with bipolar dc output is to use 2 cascaded voltage supply converters (VSCs), as shown in Fig. This topology essentially contains 2 freelance voltage sources and therefore permits freelance operation of the positive and negative poles. However, 2 separated converters area unit required in such a configuration, along with 2 isolated windings within the distribution transformer. This could lead to raised size and value. Bipolar dc voltage may be no heritable by one VSC with some modifications. As an example, the neutral line of the electrical device will be connected to the mid-point of the dc output capacitors, as represented in Fig. The current within the neutral line will be regulated to balance the dc aspect voltage. Sadly, the neutral line current might contain important dc part during this case that ought to be strictly restricted to forestall transformer saturation. So as to forestall the neutral line dc current, an additional bridge will be used, which is devoted to voltage equalization by actively redistributing the currents.

Fig.3.1. VSC with neutral line connected to dc mid-point.

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 01, January-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406 4. SIMULATION RESULTS:

Fig.4.1.Simulation Circuit.

Therefore, the most output voltage supported the Space Vector theory is one.15OM/ON times as massive as that of the standard curving modulation. This explains why, with SVPWM, we have a lot of economical use of the provision voltage than with the curving PWM method. Machine equations area unit reborn within the rotor flux frame. Rotor flux is popping in synchronous speed but during a completely different angle than stator coil flux, if there's a sinusoidal excitation. Selecting daxis on the rotor flux, q part is going to be zero. This truth simplifies the equations considerably. This methodology is extremely like DC machine's independent excitation wherever flux is that the operation of field current and torsion is in proportion with flux and rotor current. The most downside of vector management the method is flux axis angle calculation wherever is completed by measuring the flux in 2 points with ninety degrees displacement and so angles area unit calculated victimization the resulted from fluxes or estimating in relevance rotor speed.

Fig.4.2.Output Voltage.

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International Journal of Advance Engineering and Research Development (IJAERD) Volume 5, Issue 01, January-2018, e-ISSN: 2348 - 4470, print-ISSN: 2348-6406

Fig.4.3.Output Current.

5. CONCLUSION: The dc symmetrical element technique provides a useful tool for the analysis and management of bipolar LVDC distribution systems. It decomposes a bipolar dc grid into decoupled differential- mode and common-mode networks, thereby facultative separated and simplified investigation of every mode. Supported this technique, the enhanced common-mode voltage regulation theme shows advantageous performances in damping the common-mode LC resonance to enhance power quality and voltage stability.

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