Showing papers by "ABB Ltd published in 2010"

VSC-HVDC Transmission with Cascaded Two-Level Converters

Abstract: SUMMARY The two-level converter valve together with series-connected press-pack insulated-gate bipolar transistors (IGBTs) is a reliable and proven technology for transmission-scale converters. This has been put to use in a further development of high-voltage dc (HVDC) transmission employing voltage-source converters (VSCs). A cascaded two-level (CTL) converter consisting of several smaller two-level building blocks, also called cells, enables the creation of a nearly sinusoidal output voltage from the converter. The development of the CTL is the subject for this paper. Using technology modules developed and refined during the last 15 years, it has been possible to create a converter that addresses and solves many of the limitations of VSC-HVDC transmission while retaining all operational functionality. The technology is scalable up to the highest transmission voltages. Losses are reduced to roughly 1% per converter through a combination of methods. A method for removing the need for external protective equipment and circuitry in the valves is presented. The main control of the converter has been reused, although the control bandwidth, i.e., the speed, has been further improved.

Discrete-Time Current Regulator Design for AC Machine Drives

Abstract: This paper analyzes the behavior of discrete-time current regulators for ac machines operating at high ratios of fundamental-to-sampling frequencies, a situation common for high-speed automotive drives and large-traction drives. At high ratios of fundamental-to-sampling frequencies, highly oscillatory, or unstable, response can occur if the current regulator design does not properly incorporate the effects of the discrete nature of the controller, including delays between the sampling of signals and the application of the voltage commands through pulse-width modulation (PWM). This paper investigates these issues for different design methods and current regulator topologies. As part of this investigation, a simple discrete-time domain ac machine model is developed that includes the delays associated with PWM. This model is then used to design a discrete-time domain version of the complex vector PI current regulator that demonstrates improved response compared with the other regulators studied. Simulation and experimental results are provided to compare the performance, stability, and robustness of the current regulators analyzed.

Investigation of Hybrid EMI Filters for Common-Mode EMI Suppression in a Motor Drive System

Abstract: This paper begins with an analysis of the common-mode (CM) noise in a motor drive system. Based on the developed CM noise model, two cancellation techniques, CM noise voltage cancellation and CM noise current cancellation, are discussed. The constraints and impedance requirements for these two cancellation methods are investigated. An active filter with a feedforward current cancellation technique is proposed, implemented, and tested, and techniques to improve the performance of active filters are explored. It is found that due to the limitations of speed, power loss, and gain bandwidth of active filters, active electromagnetic interference (EMI) filters are not good at suppressing high di/dt or high amplitude noise current. Hybrid filters that include a passive filter and an active filter are proposed to overcome the shortcomings of active filters. Hybrid EMI filters are investigated based on the impedance requirements and frequency responses between the passive and active filters. The experiments show that the proposed active filter can greatly reduce noise by up to 50 dB at low frequencies (LFs), and therefore, the corner frequency of the passive filter can be increased considerably; as a result, the CM inductance of the passive filter is greatly reduced. The power loss of the proposed active EMI filter can be well-controlled in the experiments.

Demand Response Architecture: Integration into the Distribution Management System

Abstract: Demand Response (DR) refers to actions taken by the utility to respond to a shortage of supply for a short duration of time in the future. DR is one of the enablers of the Smart Grid paradigm as it promotes interaction and responsiveness of the customers and changes the grid from a vertically integrated structure to one that is affected by the behavior of the demand side. In Principle, it is possible to perform DR at the substation level for the customers connected to the feeders downstream or at the demand response service provider (aggregator) for the customers under its territory. This would allow for an area based solution driven mostly by the financial aspects as well as terms and conditions of the mutual agreements between the individual customers and the utility. However, as the penetration of DR increases, incorporating the network model into the DR analysis algorithm becomes necessary. This ensures the proper performance of the DR process and achieves peripheral objectives in addition to achieving the target demand reduction. The added value to the DR algorithm by incorporating the model of the distribution network can only be realized if the engine is developed as an integrated function of the Distribution Management System (DMS) at the network control center level. This paper focuses on the demand response architecture implemented at the DMS level and discusses some practical considerations associated with this approach

Cost-efficient drilling using industrial robots with high-bandwidth force feedback

Abstract: Here we present a method for high-precision drilling using an industrial robot with high-bandwidth force feedback, which is used for building up pressure to clamp-up an end-effector to the work-piece surface prior to drilling. The focus is to eliminate the sliding movement (skating) of the end-effector during the clamp-up of the end-effector to the work-piece surface, an undesired effect that is due to the comparatively low mechanical stiffness of typical serial industrial robots. This compliance also makes the robot deflect due to the cutting forces, resulting in poor hole position accuracy and to some extent in poor hole quality. Recently, functionality for high-bandwidth force control has found its way into industrial robot control systems. This could potentially open up the possibility for robotic drilling systems with improved performance, using only standard systems without excessive extra hardware and calibration techniques. Instead of automation with expensive fixtures and precise machinery, our approach was to make use of standard low-cost robot equipment in combination with sensor feedback. The resulting sliding suppression control results in greatly improved hole positioning and quality. The conceptual idea behind the force control is useful also in many other robotic applications requiring external sensor feedback control.

Enabled by high power electronics - Energy efficiency, renewables and smart grids

Abstract: The global demand for electrical energy is growing continuously, at double the growth rate of primary energy consumption. A clear transition to more electric energy systems is mandatory as energy efficiency from primary fuel to the enduser and the integration of renewables are the future key challenges. This transition to more electrical energy systems requires the transformation of today's electric power system to a smarter future grid. High power electronics is the key technology to build the next generation of the more electrical energy systems to support the major trends in energy efficiency, renewables integration and smart grid. High power electronics will continue to innovate itself due to the substantial improvement of conventional silicon devices and their packaging technologies reaching higher junction temperature and voltage levels. New wide band-gap material with substantial application benefit will enter niche markets. Multiple new multi-level topologies will change high power electronics fundamentally to support energy efficiency and the direct connection of standard power equipment. Energy efficiency is the most important topic: A real step change in regards of efficient use of primary energy is needed. Energy efficiency requires focus on efficient electrical power generation including mandatory use of waste heat, hybrid and pure electrical transportation and increased industrial process efficiency. We need to create an energy-efficient culture - from primary energy to end user -supported by global regulations. As energy as such will increase in value, efficient use will get attractive. The fast transition to more renewables energy sources is the other important topic. The energy of fifty hours of sunshine hitting the earth is equivalent to the energy stored in coal reserves globally. Therefore the future dominant role of the most important renewables, i.e. solar and wind, is actually unquestionable. The question mark lies on the speed of the transition. Especially solar power, as simple technology in the application, will develop much faster than expected. Its speed in the last years has always exceeded expectations. The same is valid for wind power since more than a decade. Again this important change needs to be supported by strong global regulations to achieve speed and competitiveness in the market place in this transition phase. And last but not least: To harvest all the investments done in our AC grids, the transition to a smarter grid is mandatory. Such a smart grid will be based on two key ingredients: Intelligence and High power electronics. Intelligence will allow a better utilization of existing assets and will increase the stability margin of the conventional AC grid. High power electronics will mainly add new DC grids and AC Var sources at the transmission and distribution level, serving as backbones and additional stability pillars to existing AC grids.

A Novel Approach to Interarea Oscillation Damping by Unified Power Flow Controllers Utilizing Ultracapacitors

Abstract: This paper discusses a novel approach for damping interarea oscillations in a bulk power network using multiple unified power flow controllers (UPFCs) utilizing ultracapacitors, also known more generally as electrochemical capacitors (ECs). In this paper, a new control is introduced to mitigate interarea oscillations by directly controlling the UPFCs' sending and receiving bus voltages that better utilizes the stored energy in the ECs. The results of this controller are compared with and without ECs. The proposed control provides better interarea oscillation mitigation when applied to multiple UPFCs in the 118-bus IEEE test system.

A review of the commercial brain-computer interface technology from perspective of industrial robotics

Abstract: Research on brain-computer interface (BCI) began in the 1970s. Great efforts in neuroscience, robotics and computer sciences have spent by many research groups to develop BCI technologies and its applications. Recently, the commercial brain-computer interface devices are emerging in gaming industry. These devices translate the electrical biosignals of a brain directly into computer commands and take advantage of total immersion into game play. This article summarizes the recent progress of brain-computer interface technologies from industrial robotics perspective and presents the evaluation of the new BCI commercial products. Then it discusses the potential applications of non-invasive commercial brain-computer interfaces to industrial robot system.

An extended friction model to capture load and temperature effects in robot joints

Abstract: Friction is the result of complex interactions between contacting surfaces in a nanoscale perspective. Depending on the application, the different models available are more or less suitable. Available static friction models are typically considered to be dependent only on relative speed of interacting surfaces. However, it is known that friction can be affected by other factors than speed. In this paper, static friction in robot joints is studied with respect to changes in joint angle, load torque and temperature. The effects of these variables are analyzed by means of experiments on a standard industrial robot. Justified by their significance, load torque and temperature are included in an extended static friction model. The proposed model is validated in a wide operating range, reducing the average error a factor of 6 when compared to a standard static friction model.

An Integrated EMI Choke for Differential-Mode and Common-Mode Noise Suppression

Abstract: This letter presents a novel integration approach for the electromagnetic interference choke. A low-permeability differential-mode (DM) choke is placed within the open window of the common-mode (CM) choke. Both chokes share the same winding structure. With the proposed approach, the footprint of inductors is greatly reduced, and high-DM inductance can be achieved. First, small-signal measurement is carried out to demonstrate the design concept and the symmetry of the proposed structure. Then large-signal experimental results verify the attenuation characteristics, as well as the thermal performance.

Method for controlling single-phase dc/ac converters and converter arrangement

Abstract: A method is disclosed for controlling single-phase DC/AC converters, along with a converter arrangement having at least two single-phase DC/AC converters. A controller is provided which can control the at least two single-phase DC/AC converters, and an isolation transformer, wherein outputs of the at least two single-phase DC/AC converters are cascade-connected with each other and an input of the isolation transformer. The controller is configured to control the at least two single-phase DC/AC converters to deliver power from their inputs to their outputs by turns.

A Shoot-Through Protection Scheme for Converters Built With SiC JFETs

Abstract: The SiC JFET is an attractive semiconductor device due to its superior switching performance and high-temperature operating capability. Its shoot-through protection remains a challenge due to the limited practical knowledge existent on this device and due to its inherent normally on nature. Addressing this limitation, this paper presents a novel shoot-through protection scheme in which a bidirectional switch, compounded by a Si insulated-gate bipolar transistor (IGBT) and a relay,is embedded into the dc-link midpoint in order to detect and clear shoot-through faults, taking advantage of the well-known desaturation protection schemes of IGBTs to protect SiC JFETs. This paper describes in detail the proposed protection mechanism and its circuit design, presenting as well the experimental results that verified the effectiveness of the proposed scheme using, first, Si MOSFETs and second, a 10-kW ac-ac converter system using SiC JFETs.

Laser Doppler Vibrometry Measures of Physiological Function: Evaluation of Biometric Capabilities

Abstract: A novel approach for remotely sensing mechanical cardiovascular activity for use as a biometric marker is proposed. Laser Doppler Vibrometry (LDV) is employed to sense vibrations on the surface of the skin above the carotid artery related to arterial wall movements associated with the central blood pressure pulse. Carotid LDV signals are recorded using noncontact methods and the resulting unobtrusiveness is a major benefit of this technique. Several recognition methods are proposed that use the temporal and/or spectral information in the signal to assess biometric performance both on an intrasession basis, and on an intersession basis where LDV measurements were acquired from the same subjects after delays ranging from one week to six months. A waveform decomposition method that utilizes principal component analysis is used to model the signal in the time domain. Authentication testing for this approach produces an equal-error rate of 0.5% for intrasession testing. However, performance degrades substantially for intersession testing, requiring a more robust approach to modeling. Improved performance is obtained using techniques based on time-frequency decomposition, incorporating a method for extracting informative components. Biometric fusion methods including data fusion and information fusion are applied to train models using data from multiple sessions. As currently implemented, this approach yields an intersession equal-error rate of 6.3%.

Method and control system for scheduling load of a power plant

Abstract: The present invention relates to a method for optimizing load scheduling for a power plant having one or more generation units. The method comprises the steps of analyzing the operating state of one or more components of generation units in terms of one or more risk indices associated with one or more components of generation units; updating the objective function that reflects the state of one or more components of generation units; solving the objective function to optimize schedule of the one or more generation units and operating state of one or more components of generation units; and operating the one or more generation units at optimized schedule and operating state. The invention also relate to a control system for scheduling load of a power plant having one or more generation units. The control system comprises an optimizer having a single objective function for optimizing load scheduling which includes maintenance scheduling and for optimally controlling processes of the one or more generation units. The optimizer utilizes a plant model component and a failure model component for load scheduling optimization.

Cooling module for cooling electronic components

Abstract: The present invention relates to the cooling of power electronic components, in particular to a cooling module comprising a condenser and to a power module comprising the cooling module as well as to a method for cooling electric and/or electronic components. A cooling module (100) with a condenser (1) having at least one panel (11) is provided for cooling electric and/or electronic components. Two sheets (114, 115) of the panel are attached to one another by a process involving roll-bonding such that a conduit (113) is formed between the two sheets (114, 115). The conduit (113) is extending in a direction of a plane formed by the sheets (114, 115). A coolant (5) is present in the conduit (113). Cooling may be provided by evaporating the coolant (5) at an evaporation section of the panel (11) and by condensing the coolant (5) at a condensing section of the panel (11). A heat load may be transferred from a heat source (3) such as an electric and/or electronic component to a heat receiving unit (2, 2A, 2B). The heat receiving unit (2, 2A, 2B) is adapted to transfer the heat load to the panel (11) which transfers the heat load to an ambient by a thermal carrier (4) such as air (4).

Fault protection of hvdc transmission lines

Abstract: A protection system (200) for high voltage direct current, HVDC, transmission lines is provided. The protection system comprises a direct current, DC, bus (201), means (202) for connecting an HVDC transmission line to the bus, at least one DC circuit breaker (203, 204) arranged for disconnecting the transmission line from the bus upon reception of a trip signal, current (211) and voltage sensors (212), an inductor (213) arranged such that the current through the transmission line passes the inductor, and a fault detection unit (220). The fault detection unit is arranged for assessing, on the basis of current and/or voltage measurements, whether a fault exists on the transmission line, and sending, if a fault is detected on the transmission line, a trip signal to the circuit breaker. The additional inductance limits the rise in fault current and facilitates a selective fault detection. Further, a method of fault protection for an HVDC transmission line is provided.

Method and apparatus for transformer diagnosis

Abstract: A transformer diagnosis apparatus and method which can advantageously be used for on-line diagnosis of a transformer, and by which transformer properties may be monitored and/or determined. The diagnosis method includes collecting, for at least two different transformer loads, measurements of a current being indicative of the transformer load, as well as measurements of at least one further transformer AC signal. The method further includes deriving, from the collected measurements, at least two values of a quantity which depends on a transformer property as well as on transformer load; and determining, from the derived values, a set of coefficient(s) of a relation for how the quantity is expected to vary with transformer load. The method further includes using the determined coefficient(s) in performing a diagnosis of the transformer.

Smart power grid security: A unified risk management approach

Abstract: Power grid information security and protection has aspects of both Industrial Control Systems (ICS) as well as Information Technology (IT) Systems. Although both ICS and IT systems require information security services to combat malicious attacks, the specifics of how these services are used for the power grid depend upon appropriate risk assessment and risk control. Distinct types of attacks targeting ICS and IT systems as well as different performance requirements of these systems determine a specific priority order of the security services implemented for each system.

HVDC VSC (HVDC light) transmission - operating experiences

Abstract: SUMMARY High Voltage Direct Current (HVDC) with Line Commutated Converters (LCC) was developed and put in commercial operation already in the 1950’s, with mercury arc valve technology. In the 1970’s, HVDC applications evolved with the introduction of thyristor based valves, which have over the years proven highly reliable, and well studied in Cigre’s collected statistics and sessions. HVDC’s typical applications are long-distance “bulk-power” transmission inter-connectors and long submarine cable systems. The development of power electronics technology resulted in the mid 1990’s of a new type of valves for the HVDC converters based on transistors (e.g. utilising Insulated-gate Bipolar Transistor, IGBT), called Voltage Source Converter, VSC.

Method and control device for controlling power flow within a dc power transmission network

Abstract: The invention relates to a method (80) for controlling power flow within a DC power flow within a DC power transmission network (1) comprising two or more interconnected converter stations (10 a , 10 b , 10 c , 10 d , 10 e ). The method (80) comprises the steps of: establishing a common feedback signal (U d,common , Ũ d'common ) to the converter stations, the common feedback signal (U d,common , Ũ d',common ) being based on an overall voltage level in the DC transmission, power network (1); providing, in the converter stations, a control signal (S 1 , S 2 , S 3 , S 4 ) based on the common feedback signal (U d,common ) and a drooped error signal (P e, droop , U e, droop ); and controlling the power flow within the DC power transmission network (1) towards set operating points ( U d ref , PCC ref by using the control signal (S 1 , S 2 , S 3 , S 4 ). The invention also relates to a control device ( 18 a , 18 b , 18 c , 18 d , 18 e ) and computer program products.

Re-defining the reactive power dispatch problem in the context of competitive electricity markets

Abstract: This study proposes a novel reactive power dispatch model that takes into account both the technical and economical aspects associated with reactive power dispatch in the context of the new operating paradigms in competitive electricity markets. The main objective of the proposed model is to minimise the total amount of dollars paid by the system operator to the generators for providing the required reactive power support. The real power generation is decoupled and assumed fixed during the reactive power dispatch procedures; however, because of the effect of reactive power on real power, a re-schedule in the real power generation is allowed within given limits. The 32-bus CIGRE benchmark system is used to illustrate the proposed reactive power dispatch technique. The developed model is generic in nature and designed to be adopted by system operators in any electricity market structure, as demonstrated by its application to Ontario's grid considering its market rules for reactive power payments.

Thermoelectric energy storage system having an internal heat exchanger and method for storing thermoelectric energy

Abstract: A thermoelectric energy storage system (TEES) and method for converting electrical energy into thermal energy to be stored and converted back to electrical energy with an improved round-trip efficiency are disclosed. The TEES comprises a working fluid circuit for circulating a working fluid through a first heat exchanger (18) and a second heat exchanger (20),a thermal storage medium circuit for circulating a thermal storage medium, the thermal storage medium circuit having at least one hot storage tank (24) coupled to a cold storage tank (22) via the first heat exchanger (18). The arrangement maximises the work performed by the cycle during charging and discharging for a given maximum pressure and maximum temperature of the working fluid. Advantageously, this maximises the round-trip efficiency of the system.

Process optimization method and system for a power plant

Abstract: A method and system for optimizing load scheduling for a power plant having one or more power generator units is provided. The method and corresponding system involves detecting an event indicative of a need for adapting one or more constraints for an objective function used in load scheduling. On such detection, the objective function is analysed to determine adaptive constraint values for the one or more constraints for optimally solving the objective function. These adaptive constraint values are used to solve the objective function and the solution of the objective function with the one or more adapted constraint values is used to operate the one or more power generation units of the power plant.

Robotic picking of parts from a parts holding bin

Abstract: A robot system (10) for picking parts (41) from a bin (40) use the image from one or more cameras (38) to determine if the robot gripper (24) has picked one part or more than one part and uses one or more images from one or more cameras (38) to determine the position / orientation of a picked part. If the robot (12) has picked more than one part from the bin (40) then an attempt is made to return the excess picked parts to the bin (40). The position / orientation of a picked part that does not meet a predetermined criteria is changed.

A hybrid distribution transformer with ac & dc power capabilities

Abstract: A hybrid transformer is provided that includes an electromagnetic transformer and an AC-AC converter with a DC bridge. The AC-AC converter is operable to keep the input voltage and current of the hybrid transformer substantially in phase and to reduce fluctuation in the output voltage of the hybrid transformer in the event of an increase or decrease in the input voltage.

Method and arrangement for tracking the maximum power point of a photovoltaic module

Abstract: A method and apparatus of tracking the maximum power point of a photovoltaic module. The method includes measuring an output voltage of the photovoltaic module, determining an output voltage of the inverter connected to the photovoltaic module, and measuring output current of the inverter connected to the photovoltaic module. A variable relating to energy of the capacitor is defined using the measured PV module output voltage, and a second harmonic component is extracted from the defined variable. A second harmonic component of the module output power is estimated using the defined variable, measured output current of the inverter, and the determined output voltage of the inverter. The estimated and extracted second harmonic components are multiplied, and a DC component is extracted from the product. A control signal for controlling the inverter connected to the photovoltaic module is formed by using the extracted DC component in a PI algorithm.

Integrated voltage and var optimization process for a distribution system

Abstract: The method determines the optimal settings for the controllable taps u t of voltage regulating transformers and the capacitor bank switches u c in a distribution network. Var optimization is calculated with the controllable tap settings u t fixed at an initial value, or the best value found so far, to output an optimized set of control settings u c . Voltage optimization is calculated with the control settings u c fixed at the best solution found so far, to output an optimal set of control settings u t . Using an objective function, system performance is evaluated using the optimal set of control settings u t and u c and repeating the steps until either the control values u t and u c do not change from one iteration to the next, the objective function value does not change or if the new objective function value is greater than the last. The control values u t and u c are then output to a distribution control system.