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Converter system that does both dc–dc conversion and dc–ac conversion in a single stage is called a single-stage converter system (SSCS). Compared to a two-stage converter, SSCS is more efficient and compact in size. In this paper, a grid-connected SSCS (GCSS) system for photovoltaic (PV) applications is presented. This GCSS transfers power from PV to grid while tracking maximum power point (MPP) continuously. The proposed system has several desirable features such as low switching loss, high gain, and compact size that makes this GCSS suitable for PV systems, where the PV system output voltage is low and varies with time. Design of the presented GCSS components with necessary equations and derivation of both current control loop and voltage control loop required for operation are given. Proposed GCSS is simulated using MATLAB/SIMULINK. Detailed simulation and experimental results are given to verify the efficacy of the proposed GCSS. [ABSTRACT FROM AUTHOR]

This paper proposes an improved performance interactive distribution static compensator (DSTATCOM) to address the limitations of conventional current control mode (CCM) and voltage control mode (VCM) operations. The proposed interactive scheme provides smooth transfer of modes of operation while remaining connected in the distribution system. In normal operation, the DSTATCOM operates in CCM to make source currents balanced, sinusoidal, and at a unity power factor. During voltage disturbances, the CCM operation cannot improve load voltage. In that case, DSTATCOM operation is changed to VCM, which maintains a constant voltage across the sensitive loads. Hence, this interactive DSTATCOM ensures continuous, flexible, and robust operation of the load. Moreover, the filter current requirements are reduced in the proposed scheme, which reduces the losses in the filter and feeder, improves inverter efficiency, and requires a reduced-rating inverter for sag mitigation. The principle of operation and control for both operating modes is analyzed. The detailed process of the flexible transfer between the two modes is derived. Deadbeat predictive control algorithms for CCM as well as VCM operation are developed for fast operation during mode transfers. The performance of the proposed scheme is validated by both simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper presents a predictive voltage control scheme for the effective control of a transformerless dynamic voltage restorer (TDVR). This control scheme utilizes the discrete model of a voltage source inverter and an interfacing filter for the generation of the switching strategy of inverter switches. Predictive voltage control algorithm-based TDVR tracks the reference voltage effectively and maintains load voltages sinusoidal during various voltage disturbances as well as load conditions. Moreover, this scheme does not require any linear controller or modulation technique. Simulation and experimental results are presented to verify the performance of the proposed scheme. [ABSTRACT FROM PUBLISHER]

This paper presents a dual voltage source inverter (DVSI) scheme to enhance the power quality and reliability of the microgrid system. The proposed scheme is comprised of two inverters, which enables the microgrid to exchange power generated by the distributed energy resources (DERs) and also to compensate the local unbalanced and nonlinear load. The control algorithms are developed based on instantaneous symmetrical component theory (ISCT) to operate DVSI in grid sharing and grid injecting modes. The proposed scheme has increased reliability, lower bandwidth requirement of the main inverter, lower cost due to reduction in filter size, and better utilization of microgrid power while using reduced dc-link voltage rating for the main inverter. These features make the DVSI scheme a promising option for microgrid supplying sensitive loads. The topology and control algorithm are validated through extensive simulation and experimental results. [ABSTRACT FROM PUBLISHER]

This paper proposes an improved hybrid distribution static compensator (DSTATCOM) topology to address some practical issues such as power rating, filter size, compensation performance, and power loss. An $LCL$ filter has been used at the front end of a voltage source inverter (VSI), which provides better switching harmonics elimination while using much smaller value of an inductor as compared with the traditional $L$ filter. A capacitor is used in series with an $LCL$ filter to reduce the dc-link voltage of the DSTATCOM. This consequently reduces the power rating of the VSI. With reduced dc-link voltage, the voltage across the shunt capacitor of the $LCL$ filter will be also less. It will reduce the power losses in the damping resistor as compared with the traditional $LCL$ filter with passive damping. Therefore, the proposed DSTATCOM topology will have reduced weight, cost, rating, and size with improved efficiency and current compensation capability compared with the traditional topology. A systematic procedure to design the components of the passive filter has been presented. The effectiveness of the proposed DSTATCOM topology over traditional topologies is validated through both simulation and experimental studies. [ABSTRACT FROM PUBLISHER]

Loads connected to a stiff source cannot be protected from voltage disturbances using a distribution static compensator (DSTATCOM). In this paper, a new control-algorithm-based multifunctional DSTATCOM is proposed to operate in voltage control mode under stiff source. This scheme provides fast voltage regulation at the load terminal during voltage disturbances and protects critical loads. In addition, during normal operation, the generated reference load voltages allow control of the source currents. Consequently, DSTATCOM injects reactive and harmonic components of load currents to make source power factor unity. Simulation and experimental results are presented to verify the efficacy of the proposed control algorithm and multifunctional DSTATCOM. [ABSTRACT FROM PUBLISHER]

This paper proposes a new algorithm to generate reference voltage for a distribution static compensator (DSTATCOM) operating in voltage-control mode. The proposed scheme exhibits several advantages compared to traditional voltage-controlled DSTATCOM where the reference voltage is arbitrarily taken as 1.0 p.u. The proposed scheme ensures that unity power factor (UPF) is achieved at the load terminal during nominal operation, which is not possible in the traditional method. Also, the compensator injects lower currents and, therefore, reduces losses in the feeder and voltage-source inverter. Further, a saving in the rating of DSTATCOM is achieved which increases its capacity to mitigate voltage sag. Nearly UPF is maintained, while regulating voltage at the load terminal, during load change. The state-space model of DSTATCOM is incorporated with the deadbeat predictive controller for fast load voltage regulation during voltage disturbances. With these features, this scheme allows DSTATCOM to tackle power-quality issues by providing power factor correction, harmonic elimination, load balancing, and voltage regulation based on the load requirement. Simulation and experimental results are presented to demonstrate the efficacy of the proposed algorithm. [ABSTRACT FROM AUTHOR]

The unified power quality conditioner (UPQC) is a custom power device, which mitigates voltage and current-related PQ issues in the power distribution systems. In this paper, a UPQC topology for applications with non-stiff source is proposed. The proposed topology enables UPQC to have a reduced dc-link voltage without compromising its compensation capability. This proposed topology also helps to match the dc-link voltage requirement of the shunt and series active filters of the UPQC. The topology uses a capacitor in series with the interfacing inductor of the shunt active filter, and the system neutral is connected to the negative terminal of the dc-link voltage to avoid the requirement of the fourth leg in the voltage source inverter (VSI) of the shunt active filter. The average switching frequency of the switches in the VSI also reduces, consequently the switching losses in the inverters reduce. Detailed design aspects of the series capacitor and VSI parameters have been discussed in the paper. A simulation study of the proposed topology has been carried out using PSCAD simulator, and the results are presented. Experimental studies are carried out on three-phase UPQC prototype to verify the proposed topology. [ABSTRACT FROM PUBLISHER]

Voltage imbalance in capacitors is a well-known problem in compensator topologies which use two or more capacitors. This imbalance may exist even if the load does not contain any dc component, due to practical factors. However, when the load contains a dc part, the voltage imbalance problem becomes critical. In this paper, a two-quadrant chopper has been used to regulate the capacitor voltages in a two-capacitor compensator structure. Two different control strategies for the two-quadrant chopper to equalize the voltage of the capacitors have been proposed. The strategies are validated through detailed simulation studies. Experiments have also been carried out to validate the hysteresis control of chopper. [ABSTRACT FROM AUTHOR]