Traditional voltage source inverter (VSI) and current source inverter (CSI) technology has advanced to the new Z-source inverter (ZSI) with a built-in impedance network, with modification to the traditional pulse width modulated (PWM) signal. Modified PWM signal accommodates the shoot-through (ST) signal (which would destroy the traditional inverters) in order to buck or boost the DC input voltage from a value between zero and infinity. The unique impedance network of passive elements, which gives a single-stage conversion, needs to be understood in detail in order to design a ZSI. The study compares traditional inverters against the ZSI and discusses the detailed operation modes involved. Circuit calculations, self-boost phenomenon, ST, inductor and capacitor design calculations, boost control methods and device selection procedures are discussed. Photovoltaic source (PV) being one of the most promising DC sources of the future, a design example involving PV and all the circuit calculations along with matching simulation results, are provided in this study.

In this paper, an alternative control method is proposed to improve the harmonic suppression efficiency of the active power filter in a distorted and an unbalanced power system to compensate for the perturbations caused by the unbalanced non‐linear loads. The proposed method uses a self‐tuning filter (STF) to process the grid voltage in order to provide a uniform reference voltage to obtain the correct angular position of the phase locked loop. Moreover, the required compensation currents are obtained by implementing another STF in the transformed set of currents in order to separate the fundamental and the harmonic currents. This allows the calculation of a precise reference current for the unbalanced, the non‐linear and the variable load conditions. The proposed control method gives an adequate compensating current reference even for a non‐ideal voltage and unbalanced current conditions. The real‐time control of the filter under the distorted and the unbalanced power system is developed in an RT‐LAB real‐time platform. The results obtained in the software‐in‐the‐loop configuration are presented to verify the effectiveness of the proposed control technique.

The future electricity network must be flexible, accessible, reliable, and economic according to the worldwide smartgrid initiative. This is also echoed by the Sustainable Energy Authority of Ireland (SEAI) and European Electricity Grid Initiative (EEGI). In order to facilitate these objectives and to reduce green house gas (GHG) emission, research on various configurations of microgrid (μG) system is gaining importance, particularly with high penetration of renewable energy sources. Depending on the resource availability, geographical locations, load demand, and existing electrical transmission and distribution system,μG can be either connected to the grid or can work in an autonomous mode. Storage can also be a part of theμG architecture. This paper presents a critical literature review of variousμG architectures. The benefits of grid-connected or isolatedμG with storage have also been identified.

A new proposal for the placement, integration, and control of unified power quality conditioner (UPQC) in distributed generation (DG)-based grid connected/autonomous microgrid/microgeneration (μG) system has been presented here. The DG converters (with storage) and the shunt part of the UPQC Active Power Filter (APF_sh) is placed at the Point of Common Coupling (PCC). The series part of the UPQC (APF_se) is connected before the PCC and in series with the grid. The dc link can also be integrated with the storage system. An intelligent islanding detection and reconnection technique (IR) are introduced in the UPQC as a secondary control. Hence, it is termed as UPQC_μG-IR. The advantages of the proposed UPQC_μG-IR over the normal UPQC are to compensate voltage interruption in addition to voltage sag/swell, harmonic, and reactive power compensation in the interconnected mode. During the interconnected and islanded mode, DG converter with storage will supply the active power only and the shunt part of the UPQC will compensate the reactive and harmonic power of the load. It also offers the DG converter to remain connected during the voltage disturbance including phase jump.

This study introduces a sliding mode control (SMC) strategy for three-phase dynamic voltage restorers (DVRs) with 12-switch voltage source inverter (VSI). The compensating voltage references needed in the SMC strategy are generated by an adaptive notch filter (ANF) which exhibits excellent performance under grid voltage anomalies such as voltage sags, swells, unbalanced and distorted grid voltage conditions. The consequence of using ANF eliminates the use of phase lock loop (PLL) or frequency lock loop (FLL) and low pass filter (LPF) which makes it distinguishable from the existing reference signal generation solutions. In addition, the use of SMC strategy with its attractive properties makes the control implementation simple. Theoretical results are supported by simulation results as well as real-time laboratory results over a range of grid voltage anomalies. These results show that the proposed control strategy not only offers an excellent dynamic response independent from the parameter variations and disturbances, but also compensates the voltage sags, swells and harmonics on the load terminals under the defined limits of the IEEE-519 standard.

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 loop-less 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.