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This article explores the impact of belt looseness on electrical and mechanical quantities of a system driven by an induction motor and a belt-pulley transmission. The effects of this defect, for example the belt slipping or the apparition of spectral signatures in some measurements, are first investigated under steady state operation. Transient state tests are then performed to analyse, in the time...
A design method based on the Diophan-tine equation is used for determining current controller parameters. The two main control objectives are: to put the closed loop poles in predefined locations;and to track the reference signal. The reference signal tracking problem is solved using the internal model principle. It introduces the reference generating polynomial into the controller design problem...
PI controllers are frequently implemented in cascaded converter system to control the DC-link voltage, because they can achieve zero steady state error. However the PI controller adds a pole at the origin point and a zero on the left half plane, and it increases the control system type number, and then the system is more difficult to control. This paper proposed a DC-link control method for the two...
Recently, the operation of a new class of three-phase differential-mode inverter have been proposed and their efficacy demonstrated using a discontinuous-modulation-scheme (DMS) based differential-mode Ćuk inverter (DMCI). DMS-based DMCI has a completely-modular topological configuration. To extend this modularity of the power stage to control implementation, one has to deal with the nonlinearity...
The boost inverter topology achieves both boosting and inversion in a single stage. Various controllers have been implemented on boost inverters to obtain stable operation. However, the double loop control strategy is the most appropriate because it provides good performance under nonlinear loads, abrupt load variations and transient short-circuit conditions. The double loop control strategy was introduced...
Microinverters mounted on each photovoltaic (PV) panels are gaining popularity due to their benefits such as incremented energy harvest and plug-play operation. This paper proposes a single-stage zeta microinverter for PV applications. The proposed topology is based on a high frequency (HF) transformer isolated zeta converter with a single low side switch on the primary side of transformer. The unique...
An adaptive carrier based sinusoidal pulse width modulation (SPWM) technique for cascaded h-bridge (CHB) multilevel converters is presented in this paper. The proposed technique enables the CHB topology to provide a symmetrical ac voltage from a set of time-variant input dc source voltages. Two alternative approaches, namely the single-carrier and dual-carrier algorithms, are described for implementing...
The grid-tied low voltage photovoltaics are expanded day by day. Aiming for a high penetration level, the Fault Ride Through Capability (FRTC) standard should be extended to these units as well. In this paper, the behavior of Single Phase Grid Connected PV Systems under faulty conditions is investigated. For this purpose, a SPWM controlled full bridge voltage source inverter is used. The proposed...
This paper proposes a linear quadratic regulator with integral action, ensuring fast dynamic response and resisting capability of voltage deviation from instantaneous reference grid voltage, to control the inverter voltage that can also be used in a microgrid. The proposed control strategy is based on a linear quadratic regulator, minimizing the cost function of the system, with integral action used...
One of the key operation of the grid-connected PV system is a fast and accurate control of the grid current, but the traditional proportional integral (PI) control of the grid current can not achieve this important goal because of its steady-state error. In addition, after the PV system is incorporated into the grid, the influence caused by grid inductance has a non-negligible effect on the damping...
In this paper we examine the amplitude and phase dynamics of power-electronic inverters in islanded microgrids that are controlled to emulate the dynamics of a class of weakly nonlinear Liénard-type oscillators. The general strategy of controlling inverters to emulate the behavior of Liénard-type oscillators is termed Virtual Oscillator Control (VOC), and it presents a compelling time-domain alternative...
This paper considers a collection of networked nonlinear dynamical systems, and addresses the synthesis of feedback controllers that seek optimal operating points corresponding to the solution of pertinent network-wide optimization problems. Particular emphasis is placed on the solution of semidefinite programs (SDPs). The design of the feedback controller is grounded on a dual ε-subgradient approach,...
In the near future, transmission grids will include an increasing share of directly connected voltage source converters. These systems should be able to support the utility grid autonomously. The present paper reviews the most popular approaches to address the challenge of proper load sharing amongst multiple parallel inverters applied to the utility grid case. Originally developed for Microgrid or...
Proportionate sharing of load changes in a microgrid without communication among the generators is a difficult problem. In this paper an exact power sharing algorithm is developed that uses an optimization-based technique to minimize the exchange of state information among the generators. To demonstrate the application of the developed framework we present simulation results for a system constructed...
The output voltage range of PV cells is widely influenced by the environment factors, such as temperature, solar radiation, etc. The lower output voltage of solar array can hardly meet the requirements for grid-connected operation of the system. To achieve high voltage gain and a steady ac output voltage in spite of the low dc input voltage, this paper presents a novel single-stage high gain current...
Six-step operation has many advantages in Permanent Magnet Synchronous Machine (PMSM) drives such as extended utilization range of the inverter output voltage. However, the error in the voltage modulation can be occurred when the PMSM runs at ultra-high speed (above 50krpm), that is, the ratio of the sampling frequency to the fundamental frequency (Fratio = fsamp/ffund) is small. In this paper, the...
In virtual vector control schemes for singlephase current-regulated voltage source inverters, a transient disturbance may be induced due to the time-delay in the virtual orthogonal signal. This disturbance deteriorates the dynamic current-tracking capability and power quality. A unified scalar model is developed to analyze the phenomenon. Based on this model, an improved control scheme with a pre-compensator...
The high grid impedance in weak grid will lead to small bandwidth of control system and poor control performance of PV inverter. To solve this problem, this paper presents a quasi-PRD control method which can increase the bandwidth and dynamic response speed of control system. At first, the quasi-PRD controller was applied to replace the traditional PI controller. Then, the two harmonic injection...
The interactions of more and more power electronics-interfaced power systems can worsen the power quality and the system stability in distribution networks. System stability can be addressed analyzing the source and load impedances at the interaction section and well-established approaches exist for DC and three-phase AC networks. Some papers focused also on single-phase AC systems, whose study is...
This paper proposes an optimal current control with linear quadratic regulators for 3-phase grid-connected inverters. Because the 3-phase current control is a multivariable control problem with multiple interconnected loops, the traditional control methods, like proportional-integral-derivative control and predictive control, have the difficulty in optimizing their parameters. The proposed control...
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