Rating requirements of a unified power quality conditioner (UPQC) for voltage ride through capability enhancement

The problem of voltage ride through capability of fixed speed wind generation as a result of voltage sags is examined by means of a simulation study. The role of a Unified Power Quality Conditioner (UPQC), which provides both shunt and series compensation, in enhancing the ride through capability is investigated under both full and partial voltage restoration. Results of a study to identify the minimum rating requirements to ensure stability are presented

Rating Requirements of the UPQC to Integrate the FSIG Type Wind Generation to the Grid

The ability of wind generation to remain connected to the grid in the event of system faults and dynamic reactive power compensation are two aspects of grid integration, which have received particular attention. The wind driven, fixed-speed induction generator (FSIG) on its own fails to fulfil these requirements of grid integration. The application of a unified power quality conditioner (UPQC) to overcome the grid integration problems of the FSIG is investigated. The role of the UPQC in enhancing the fault ride-through capability of the generator is also investigated under both full and partial terminal voltage restoration. A realistic estimation of the rating requirements of UPQC for this type of application is carried out. A general principle is presented to choose the most practical and economical rating of the UPQC. The performance comparison of a UPQC and a static synchronous compensator to aid fault ride-through capability of a 2 MW FSIG under Irish grid code requirements has been carried out and the UPQC is found to be more economical in relation to device rating

Optimising the rating of the UPQC for applying to the fault ride through enhancement of wind generation

The unified power quality conditioner (UPQC) is a combination of a shunt and a series compensator cascaded via a DC link capacitor which works on the combined principle of active filtering and dynamic voltage restoration. Therefore, the UPQC can be a potential solution to the grid integration problems associated with fixed speed wind generators including reactive power compensation and fault ride through capability. The hardware design of the UPQC can be made more cost effective by proper selection of the rating of the individual compensators of the UPQC. It is shown in the paper that the application of a fixed capacitor can lower the cost of the UPQC further, without compromising the performance. The fixed capacitor shares the reactive power load with the shunt compensator and the overall rating of the UPQC is reduced. The proposed scheme also helps in reducing the power loss occurring in the power electronic switches as current conduction of the switches is reduced. Simulation results are provided in the paper to support the theory

A new configuration and control of doubly fed induction generator (UPQC-WG)

The paper presents detailed simulation based analysis and investigation on grid code compliance of a new configuration of a 2 MW doubly fed induction generator. The converters of DFIG are connected and controlled to function like a unified power quality conditioner (UPQC). One of the converters is connected in series with the stator terminals and acts to maintain the stator voltage at a predetermined value. It can also transfer power to or from the rotor side converter through the common DC link. The other converter is connected to the rotor like a conventional DFIG and is controlled to maintain appropriate rotor currents to establish the operating point based on the input mechanical torque and reactive power set point at the grid connection. The generator performs satisfactorily under steady state and grid fault condition both in the super and sub synchronous speed range. The newly designed machine is Irish grid code compliant

Rating requirements of a unified power quality conditioner (UPQC) for voltage ride through capability enhancement

The problem of voltage ride through capability of fixed speed wind generation as a result of voltage sags is examined by means of a simulation study. The role of a Unified Power Quality Conditioner (UPQC), which provides both shunt and series compensation, in enhancing the ride through capability is investigated under both full and partial voltage restoration. Results of a study to identify the minimum rating requirements to ensure stability are presented

Effects of age, stage of disease, and educational level on cognitive dysfunction in non-demented idiopathic Parkinsonism: A preliminary report

Background: Parkinsonism is known to be associated with clinically significant impairments on an array of cognitive deficits. The degree of impairment is dependent not only on the course of the disease, but also on other bio-social factors. The objective of the present study was to examine the cognitive dysfunction in non-demented idiopathic Parkinson′s disease (IPD) in relation to age, stage of disease, and educational level in a sample in Kolkata, India. Materials and Methods: The sample consisted of 51 (42 males, 9 females) right-handed patients suffering from non-demented IPD, of age between 40 and 82 years. Data were collected during on-phase medication by using the Kolkata Cognitive Screening Battery. Data were analyzed using means, standard deviations, and multivariate analyses of variance (MANOVA). Results and Conclusion: The patients with IPD were impaired in comparison to the available normative data in almost all aspects of cognitive functioning and higher order mental processes. With increasing age, the patients showed greater impairment in delayed memory and recognition task. Patients of more severe stage showed greater impairment in MMSE, delayed recall, and information. Those with lower education had more impaired visuoconstructional ability, information, comprehension, similarities, and arithmetic

Development of laboratory prototype of a 12kVA digital shunt active filter

The paper reports the development of a laboratory prototype of a fully digital DSP controlled 12 kVA Shunt Active Filter (ShAF) capable of compensating for non-linear, unbalanced load and reactive power. A fully digital controller is implemented for the reference generation and the current control purposes. The delay problem in digital current controller is overcome by application of a fast DSP, a compact controller and proper flow of control steps in the DSP software. A Phase Locked Loop (PLL)-less software grid synchronization method has been proposed for the effective operation of the ShAF under the grid frequency variation. The source current THD has been improved from 15.8% to 4.45%. The control features, experimental setup, and results are presented in the paper

Development of a 12 kVA DSP-Controlled Laboratory Prototype UPQC

This paper reports the development of a laboratory prototype of a fully digital DSP-controlled 12-kVA unified power quality conditioner (UPQC), capable of compensating for both the supply voltage and the load current imperfections. A fully digital controller based on the TMS320F2812 DSP platform is implemented for the reference generation as well as control purposes. The delay problem in the digital controller is overcome by application of a fast DSP, a compact control technique and proper flow of control steps in the DSP software. A phase-locked loopless software grid synchronization method has been implemented for the effective operation of the UPQC under conditions of grid frequency variation. A sequence-based compensation strategy has been developed to compensate for balanced and unbalanced sags while accommodating the fact that the voltage injection capability of the UPQC is limited. The prototype UPQC power circuit, control features, and control algorithm along with experimental results are presented in this paper

Sequence analysis based DSP controller for dynamic voltage restorer (DVR)

The paper examines the behaviour of a dynamic voltage restorer (DVR) under balanced/unbalanced supply voltage sag condition, and restricted DVR injection capability (e.g. limited to 50% of the supply voltage injection). Sequence components of the supply voltage are extracted to generate the reference injected voltage for the DVR. The control determines the maximum possible positive sequence injection within the capacity of the compensator to achieve balanced voltage conditions at the load terminals. The control is verified through simulation and experimentation. The control algorithm has been implemented in a TI320F2812 fixed point DSP and the effectiveness of the controller is verified in a three-phase, 10kVA DVR laboratory prototype. In a three-phase, 240 V system, balanced sag and sag with magnitude and phase unbalance have been created, which is successfully compensated by the DVR with the proposed controller