Deepak Divan

A three-phase soft-switched high power density DC/DC converter for high power applications

The authors present three DC/DC converter topologies suitable for high-power-density high-power applications. All three circuits operate in a soft-switched manner, making possible a reduction in device switching losses and an increase in switching frequency. The three-phase dual-bridge converter proposed is seen to have the most favorable characteristics. This converter consists of two three-phase inverter stages operating in a high frequency six-step mode. In contrast to existing single-phase AC-link DC/DC converters, low RMS current ratings are obtained for both the input and output filter capacitors. This is in addition to smaller filter element values due to the higher-frequency content of the input and output waveforms. The use of a three-phase symmetrical transformer instead of single-phase transformers and a better utilization of the available apparent power of the transformer (as a consequence of the controlled output inverter) significantly increase the power density attainable.<<ETX>>

Control of parallel connected inverters in stand-alone AC supply systems

A scheme for controlling parallel connected inverters in a stand-alone AC supply system is presented. A key feature of this scheme is that it uses only those variables which can be measured locally at the inverter, and does not need communication of control signals between the inverters. This feature is important in high reliability uninterruptible power supply (UPS) systems, and in large DC power sources connected to an AC distribution system. Real and reactive power sharing between inverters can be achieved by controlling two independent quantities at the inverter: the power angle and the fundamental inverter voltage magnitude.<<ETX>>

The resonant DC link converter-a new concept in static power conversion

A novel approach to realizing efficient high-performance power converters is presented. The concept of a resonant DC link inverter has been proposed and realized with the addition of only one small inductor and capacitor to a conventional voltage source inverter circuit. The proposed technology is capable of switching almost an order of magnitude faster than state-of-the-art voltage source inverters at significantly improved efficiencies using the same family of devices. The topology is especially suitable for high-power applications using gate turn-off devices. A 4.5 kW inverter has been fabricated and tested extensively in the laboratory, and the superior characteristics of the resonant DC link topology have been verified. >

Pseudo-resonant full bridge DC/DC converter

This paper proposes a new dc/dc converter topology which combines the ease of control and wide range of conventional dc/dc converters, with low switching losses, low dv/dt and low EMI that is typical of zero voltage switched resonant converters. Consequently, the ratings of these components are substantially lower than for similarly rated resonant topologies. Operation at very high frequencies is possible and is shown with the fabrication of a 200 watt, 1 MHz dc/dc converter.

Dynamic sag correctors: cost effective industrial power line conditioning

Voltage sags, transients, and momentary interruption of power together constitute 92% of the PQ problems encountered by typical industrial customers. The series-parallel connected dynamic sag corrector (DySC) provides statistically significant protection at greatly reduced cost. The DySC is rated 1.5 kVA 1-phase to 2000 kVA 3-phase and features a patented single stage power conversion circuit with minimal stored energy. A unique circuit allows operation with opened upstream circuit breaker. The paper presents a detailed discussion of DySC operating principles and validation of performance. It also provides conditions under which this new category of product can be applied.

A Distributed Static Series Compensator System for Realizing Active Power Flow Control on Existing Power Lines

Flexible AC transmission systems (FACTS) devices can control power flow in the transmission system to improve asset utilization, relieve congestion, and limit loop flows. High costs and reliability concerns have restricted their use in these applications. The concept of distributed FACTS (D-FACTS) is introduced as a way to remove these barriers. A new device, the distributed static series compensator (DSSC), attaches directly to existing HV or EHV conductors and so does not require HV insulation. It can be manufactured at low cost from conventional industrial-grade components. The DSSC modules are distributed, a few per conductor mile, to achieve the desired power flow control functionality by effectively changing the line reactance. Experimental results from a prototype module are presented, along with examples of the benefits deriving from a system of DSSC devices

Power line sensornet - a new concept for power grid monitoring

Significant work has been done on the sensing of utility assets. Most proposed approaches have been based on the principle of using few relatively expensive sensors and wireless communication links to provide a sample of data on the status of the power line. This paper introduces the concept of a distributed power line sensornet (PLS) as an alternative approach to realizing cost-effective power grid monitoring. By way of an example a distributed sensor module is proposed that can be clipped on to an existing power line and have the following four core functions: continuously monitoring critical line parameters in the immediate vicinity of the sensor; estimating the line status and identifying incipient faults in a changing environment; operating as a node of the sensornet communication system; power and fault management while allowing sensing and communication functions. Details of implementation and system impact are presented in the paper, along with simulation results

A new architecture for offshore wind farms

Offshore wind farms using HVDC links can be positioned a large distance from shore, opening up new opportunities for wind generation. Conventional approaches using 60 Hz generators and transformers are not appropriate in such applications, as they are heavy and result in expensive and complex installation and maintenance issues. This paper proposes an alternative architecture for such wind farms, using permanent magnet generators, medium frequency transformers and simple power converters to realize a compact and light system. It is possible that in the long term, the proposed approach may prove attractive for land-based wind farms as well.

Design considerations for charge equalization of an electric vehicle battery system

Charge equalization for series connected battery strings has important ramifications on battery life. It enhances the uniformity of the battery cells and hence improves the life of the battery as a whole. A new charge equalization technique for a series string of battery cells has been recently proposed by the authors. The basic technique utilizes a simple isolated DC-to-DC power converter with a capacitive output filter along with a multi-winding transformer. The possibility of integrating the trickle charge function with the charge equalization function is potentially very attractive, as it can lead to an efficient and low cost implementation.<<ETX>>

Charge equalization for an electric vehicle battery system

Charge equalization for series connected battery strings has important ramifications on battery life. It enhances the uniformity of the battery cells and hence improves the life of the battery as a whole. A new charge equalization technique for a series string of battery cells has been recently proposed by the authors. The basic technique utilizes a simple isolated dc-to-dc converter with a capacitive output filter along with a multiwinding transformer. The possibility of integrating the trickle charge function with the charge equalization function is potentially very attractive, as it can lead to an efficient and low cost implementation.