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This paper presents the design of a current control system for a single-phase grid-tied inverter equipped with a LCL grid-side filter, which is suitable for inverter DC current component suppression. For that purpose, a proportional-resonant (PR) controller of principal harmonic current component has been designed. This is followed by the design of DC current component estimator based on second-order...
Unpredictable power quality (PQ) events such as, balanced and unbalanced voltage sag/swell, frequency shift, phase jump and harmonic distortions in the utility grid voltage drastically affects the performance of a grid interfaced distributed generation (DG) systems due to unreliable synchronization. This paper presents adaptive synchronization based dq-current control technique for three-level NPC...
This paper presents an FPGA-based adaptive predictive control scheme for single-phase T-type NPC inverter in applications to microgrids with high efficiency and robust performance. Predictive control is applied for current regulation to achieve fast dynamic response with low total harmonic distortion (THD). Implementation of a grid inverter with minimum inductor will result nonlinear inductance due...
This paper presents a control method for current controlled voltage source inverter (CC-VSI) with output L filter. The new algorithm determines the optimum duty cycle for each modulation period. The duty cycle minimizes assumed quality function. The quality function is the integral of the absolute value of the difference between the reference waveform and the waveform resulting from the differential...
The distributed generation (DG) should supply continuous power to local critical load, even in the condition of utility outage. This paper proposes a novel seamless transfer control strategy, which combines indirect current control and droop control. A microgrid structure of multi-masters and multi-slaves is also proposed, which based on the master-slave control and droop control. The master DGs are...
The inverter with critical loads should be able to provide critical loads with a stable and seamless voltage during control mode change as well as clearing time. The indirect current control has been proposed for providing stable voltage with critical load during clearing time and seamless control mode transfer of inverters. However, the islanding detection is difficult since with the indirect current...
This study proposes an enhanced current control strategy to eliminate DC and harmonic current at the output current of three-phase grid-connected inverters caused by DC offset and scaling error in grid voltage measurement. The proposed current controller designed in the stationary (α-β) reference frame is developed with a proportional integral (PI) plus three resonant controllers where the resonant...
A digital zero-voltage switching(ZVS) current control method which is suitable for full-bridge or half-bridge inverter is proposed in this paper to achieve high power density, low cost and high conversion efficiency. The digital current control scheme is realized by DSP TMS320F28035 and does not demand complex algorithm, or extra analog circuits. Furthermore, ZVS is achieved by inductor current operating...
This paper proposes a seamless transfer control strategy for bi-modal grid-connected (GC) power conditioning system (PCS). The load can be supplied the power continuously, regardless of the grid states. The PCS should be operated in two modes. One is the GC mode and the other is stand-alone (SA) mode. A current control loop and a feed-forward voltage control loop are used to control the grid current...
This paper describes new model predictive control for high performance current control system of PMSM. The current control system based on FCS-MPC decides an inverter output voltage directly by searching. In a principle, this type controller can use not only PWM drive but also overmodulation and square wave drive[1]. However, conventional current control based on FCS-MPC is inferior to PWM modulated...
The active filtering and regeneration systems used in active DC traction substations must allow the natural transition from filtering to regeneration mode and vice versa. In the both operation modes, active filtering and regeneration, the grid current must be sinusoidal. Consequently, the magnitude of the fundamental network current is necessary in the control part, in order to generate the reference...
This paper presents the operation of a grid-tied photovoltaic power generator considering a two stages configuration for active power injection. A Neutral Point Clamped Inverter (NPC Inverter) was used for the DC-AC conversion and a DC-DC Boost converter complemented the system configuration. The control system includes the following loops: a maximum power point tracking algorithm, a DC bus voltage...
This paper presents a control scheme for a three-phase grid-connected photovoltaic (PV) system operating in a grid connection and isolated grid mode. Control techniques include voltage and current control of grid-connected PV inverters. In the grid-connected mode, the grid controls the amplitude and frequency of the output voltage of the PV inverter. The inverter operates in the current control mode...
There has been a gradual increase in generation of power from renewable energy resources interfaced to existing utility grid to increase its reliability. Tapping of these resources is done in multiple ways like standalone wind generators or photovoltaic plants, microgrids etc. Interfacing DC sources like photovoltaic cells, battery, fuel cells with AC systems requires tie line inverter with robust...
This paper presents a method for estimating the electrical angle of the rotor for permanent-magnet synchronous motors (PMSMs) in model predictive current control (MPCC) so that an encoder is removed for high reliability and low system costs. In our approach, an estimator of the electrical angle of the rotor is introduced in the MPCC. The effectiveness of the proposed method is verified through simulations...
Parallel connected systems constructed by connecting existing power converters in parallel have low costs and can provide large short term output. They can also be easily constructed if the allotment of the converters' output current can be controlled to different values. In this type of construction, however, it is important to reduce the cross current that flows between the converters. This paper...
This paper presents the current control for the vibration torque reference of an Interior Permanent Magnet Synchronous Motor (IPMSM) to avoid output voltage saturation of the inverter under the reduction of copper losses. The candidates of the current operating points are obtained by dividing constant torque curve. The operating point of the smallest current without voltage saturation are selected...
A deadbeat predictive current control (DPCC) algorithm for PMSM drive system basing on disturbance compensation is proposed in this paper. First, a stator current and disturbance observer (SCDO) is presented to simultaneously predict future value of stator current and track system disturbance caused by parameter mismatch in real time. Based on this SCDO, a composite control method combining the DPCC...
This paper proposes a cascade voltage/current control method (vector control) for a three-phase inverter for grid connected applications. The study mainly focuses on the innovative control law based on the flatness properties for a three-phase inverter with output LC filter. Utilizing the flatness principle, we propose simple solutions to the control and stabilization problems. The effectiveness of...
Single-phase inverter suffers from double-frequency power ripples in the input side transferred there from the ac-side. To mitigate this ripple, two types of power decoupling approaches can be applied: passive power decoupling and active power decoupling. We present a technique of passive power decoupling realized by modifying the control strategy. The main idea is to produce the time-varying shoot-through...
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