In this paper, the idea of operating an inverter to mimic a synchronous generator (SG) is motivated and developed. We call inverters that are operated in way synchronverters. Using synchronverters, well-established theory/algorithms used control SGs can still be power systems where significant proportion generating capacity inverter-based. describe dynamics, implementation, operation The real reactive delivered by synchronverters connected parallel as generators automatically shared using...

A synchronverter is an inverter that mimics synchronous generators, which offers a mechanism for power systems to control grid-connected renewable energy and facilitates smart grid integration. Similar other inverters, it needs dedicated synchronization unit, e.g., phase-locked loop (PLL), provide the phase, frequency, amplitude of voltage as references. In this paper, radical step taken improve self-synchronized by removing unit. It can automatically synchronize itself with before...

In this paper, the inherent limitations of conventional droop control scheme are revealed. It has been proven that parallel-operated inverters should have same per-unit impedance in order for them to share load accurately proportion their power ratings when is adopted. The controllers also generate voltage set-point inverters. Both conditions difficult meet practice, which results errors proportional sharing. An improved controller then proposed achieve accurate sharing without meeting these...

The concept of the virtual synchronous generator (VSG) is emerging as an attractive solution for controlling grid-connected inverter when renewable energy has a high penetration level into grid. This paper focuses on small-signal modeling and parameters design power loop VSG, points out that bandwidth should be far less than twice line frequency purpose avoiding VSG output voltage to severely distorted. Consequently, line-frequency-averaged model derived system analysis design. Based model,...

This paper proposes a robust control strategy for uncertain LTI systems. The is based on an uncertainty and disturbance estimator (UDE). It brings similar performance as the time-delay (TDC). advantages over TDC are: (i) no delay introduced into system; (ii) there are oscillations in signal; (iii) need of measuring derivatives state vector. stability LTI-SISO systems analyzed, simulations given to show effectiveness UDE-based with comparison made TDC.

In this paper, a current-control strategy is proposed for voltage-source inverters in microgrids. The main objective of the controller to inject clean sinusoidal current grid, even presence nonlinear/unbalanced loads and/or grid-voltage distortions. repetitive control technique adopted because it can deal with very large number harmonics simultaneously. consists an internal model and stabilizing compensator, which designed by using <i xmlns:mml="http://www.w3.org/1998/Math/MathML"...

Power systems are going through a paradigm change from centralized generation to distributed and further on smart grids. More more renewable-energy sources, electric vehicles, energy storage systems, so forth being connected power electronic converters. Moreover, the majority of loads expected connect grid converters as well. This article shows that these converters, either supply side or load side, can all be controlled behave like virtual synchronous machines (VSMs) possess dynamics...

Droop control is a well-known strategy for the parallel operation of inverters. However, droop changes its form inverters with different types output impedance, and so far, it impossible to operate inductive capacitive impedances in parallel. In this paper, shown that there exists universal principle impedance having phase angle between -(π/2) rad (π/2) rad. It takes resistive (R-inverters). Hence, robust controller recently proposed literature R-inverters actually provides one way implement...

In this paper, the uncertainty and disturbance estimator (UDE)-based robust control is applied to of a class nonaffine nonlinear systems. This systems very general covers large range However, such challenging because input variables are not expressed in an affine form, which leads failure using feedback linearization. The proposed UDE-based method avoids inverse operator construction, might result singularity problem. Moreover, assumption on term relaxed, only its bandwidth information...

Interactions between individually designed power subsystems in a cascaded system may cause instability. This paper proposes an approach, which connects virtual impedance parallel or series with the input of load converter so that magnitude phase converter's is modified small range frequency, to solve instability problem system. The requirements on (PVI) and (SVI) are derived, control strategies implement PVI SVI proposed. comparison general design procedure also discussed. Finally,...

Power systems are going through a paradigm change from centralized generation to distributed and further on smart grids. In this paper, it is shown that future power will be electronics based, instead of electric machines with huge number incompatible players the fundamental challenge behind how make sure these could work together maintain system stability. Then, lateral architecture based synchronization mechanism synchronous (SM), which has underpinned growth operation for over 100 years,...

In this paper, the idea of operating an inverter as a synchronous generator is developed after establishing model for generators to cover all dynamics without any assumptions on signals. The inverters which are operated in way called static (SSG). This means that well-established theory/device can still be used inverters, will dominate power generation future because increasing share distributed sources and renewable energy utilised. SSG regulated using well-known frequency voltage drooping...

In this paper, a cascaded current-voltage control strategy is proposed for inverters to simultaneously improve the power quality of inverter local load voltage and current exchanged with grid. It also enables seamless transfer operation mode from stand-alone grid-connected or vice versa. The scheme includes an inner loop outer loop, both controllers designed using <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i> <sup...

Abstract The control algorithm based on the uncertainty and disturbance estimator (UDE) is a robust strategy has received wide attention in recent years. In this paper, two‐degree‐of‐freedom nature of UDE‐based controllers revealed. set‐point tracking response determined by reference model, whereas robustness are error feedback gain filter introduced to estimate disturbances. It also revealed that dynamics system two filters, which one other design these filters decoupled frequency domain....

Bulky electrolytic capacitors, which are often needed in dc systems to filter out voltage ripples, considerably reduce power density and system reliability. In this paper, a ripple eliminator, is bidirectional buck-boost converter terminated with an auxiliary capacitor, adopted replace bulky capacitors systems. The ripples on the terminals (i.e., bus) can be transferred capacitor vary wide range. Moreover, average of controlled either lower or higher than dc-bus voltage, offers operational...

In this paper, the load and/or grid connected to an inverter is modeled as combination of voltage sources and current at harmonic frequencies. As a result, system can be analyzed each individual frequency, which avoids difficulty in defining reactive power for with different frequencies because it now defined frequency. Moreover, droop control strategy developed systems delivering constant source, instead source. This then applied develop controller so that right amount added reference...

A global parameter estimation method for a permanent magnet synchronous machines (PMSM) drive system is proposed, where the electrical parameters, mechanical and voltage-source-inverter (VSI) nonlinearity are regarded as whole formulated single optimization model. dynamic learning estimator proposed tracking VSI of PMSM by using self-learning particle swarm (DSLPSO). In DSLPSO, novel movement modification equation with exemplar strategy designed to ensure its diversity achieve reasonable...

The uncertainty and disturbance estimation (UDE)-based robust control strategy is able to achieve good performance by estimating compensating the in a system with filter having appropriate frequency characteristics. However, how systematically design reference UDE-based asymptotic tracking rejection still missing literature. In this paper, solved applying well-known internal model principle. conditions guarantee closed-loop stability are derived. Experimental results on servo presented as an...

Synchronverters are grid-friendly inverters that mimic conventional synchronous generators and play an important role in integrating different types of renewable energy sources, electric vehicles, storage systems, etc., to the smart grid. In this paper, improved synchronverter is proposed make sure its frequency voltage always stay within given ranges, while maintaining function original synchronverter. Furthermore, stability region characterized by system parameters analytically obtained,...

A dynamic particle swarm optimization with learning strategy (DPSO-LS) is proposed for key parameter estimation permanent magnet synchronous machines (PMSMs), where the voltage-source inverter (VSI) nonlinearities are taken into account in model and can be estimated simultaneously other machine parameters. In DPSO-LS algorithm, a novel movement modification equation variable exploration vector designed to effectively update particles, enabling swarms cover large areas of search space...

Instability problem is an important issue for dc/dc conversion cascaded systems (Cascaded system in short). Though most of the existing stabilization methods can stabilize whole very well, they may ignore their impacts on dynamic performance original system. Unfortunately, these are negative to some extent. Recently, adaptive-series-virtual-impedance (ASVI) control strategy has been reported address above problem. It not only via shaping load input impedance, but also reduce its impact...