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This paper proposes a new type of voltage swell/sag compensator based on single-phase Z-source AC/AC converter. The proposed topology employs a pulse width modulation (PWM) Z-source AC/AC converter along with a transformer. A commutation strategy to drive the AC/AC converter is employed to realize snubberless operation. Circuit analysis is provided. Simulation and experimental results at 20% voltage...
This paper presents a control system based on a repetitive controller to compensate key power-quality disturbances, namely voltage sags, harmonic voltages and voltage imbalances, using a dynamic voltage restorer (DVR). The control scheme deals with all three disturbances simultaneously within a specified bandwidth. The control structure contains a feed-forward term to improve the transient response...
The present paper addresses the control of doubly fed induction generators under unbalanced voltage sags considering the converter limits. A control strategy is proposed by choosing certain current reference values in the positive and negative sequences so that the torque and the DC voltage are kept stable during such unbalanced sags considering the converter limits.
This paper investigates the interactions which arise between grid connected photovoltaic inverter systems and the electrical grid. In particular, it considers the effect of grid voltage harmonics and grid impedance on the current control performance of grid connected inverter systems. In these photovoltaic inverter systems it is usual to control unity power factor, sinusoidal, current into the grid...
This paper deals with shunt active power filtering for power quality improvement under unfavourable non-linear load and source conditions. A simple hybrid control strategy is used, based on a numerical integrator proportional (IP) DC bus controller combined with a phase-locked loop (P.L.L.) output to generate reference currents. A second analogue current controller is developed to insure- three phase...
The aim of this paper is to propose an over current limitation and voltage control strategy for a grid connected inverter with a LC output filter used in distributed generation and in case of voltage sag. This strategy relies on the control of LC output filter voltage with a resonant controller. This controller has to control current and load voltage throughout voltage sag. Generally, resonant controller...
Grid codes are being revised to include additional requirements for renewable energy, as the installed power increases. Therefore it is needed to develop control systems that are able to fulfil those new requirements, which usually include the ability to operate under unbalanced grid voltages without polluting the grid, among others. This paper presents a three-phase inverter for connection of photovoltaic...
This paper presents a fast on-load tap changing regulator used to correct unbalanced voltages. This regulator uses the semi natural commutation in order to improve the response. The proposed topology injects the voltage in only phase in order to balance the three phase system.
Reliability and power quality are two aspects of motor drives which have been gaining the attention of the industry. In fact, as the processes increased in number and complexity, the criticality of each component also increased. This paper proposes the usage of a PWM rectifier to accomplish a fault-tolerant motor drive with optimal performance and power quality. The system uses a hardware reconfiguration,...
Mainly due to historical and convenience reasons, for power levels up to several kVA electric utilities provide power distribution typically uses 1-phase a.c. feeders, despite a 3-phase supply would be technically preferable permitting for instance to use more efficient and compact induction motors, 3-phase rectifiers providing lower output ripple etc. This paper deals with a simple converter able...
Configurations of combined series and shunt active filters, also known as unified power quality conditioners (UPQCs), are designed for simultaneous compensation of voltage and current harmonics and imbalances. Sometimes, compensation of voltage sag/swell is also included as additional functionality of the UPQC. Traditionally, the shunt active filter of the UPQC behaves as a controlled current source...
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