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Grid-connected inverter is an important part of the grid-connected system. Compared with the traditional L or LC filter, LCL filter has a better high-frequency harmonic attenuation performance. However, LCL filter has resonant peak, which has a great influence on the stability of the system. This paper first analyzes the effect of passive damping method on the resonance peak; then a double closed-loop...
Energy storage technology is an important measure for power output of new energy generation system. T-type three-level structure is adopt as the topology of energy storage inverter. Mathematical model of grid-connected operation in ABC coordinate system and dq coordinate system is built. A double closed loop control strategy of which inner loop current and outer loop power control is proposed. The...
H-bridge cascaded inverter can be used for harmonic compensation in medium and high voltage systems. As the equivalent switching frequency is high, L-type filter is commonly used for H-bridge cascaded inverter. Meanwhile, considering device safety and filtering effect, inductance value of L filter is large. When the command current contains harmonics, especially high harmonics, large connecting inductance...
DC capacitor voltage imbalance is an inherent problem limited the further development of multi-level Neutral Point Clamped (NPC). In this paper, a new hybrid control method based on Space Vector Pulse Width Modulation (SVPWM) for five-level NPC at high modulation index and high power factor is presented. By choosing appropriate switching pattern in lower modulation index sectors and collocating different...
Digital-physical hybrid real-time simulation is considered to be an advanced method for future power system simulation. However, the physical interface will inevitably exist DC component, which causes negative effects on practical applications, such as degradation of simulation performance, damage to physical equipment, etc. A novel DC component elimination control strategy for the digital-physical...
Voltage deviations of dc-link capacitors are the main problem of multilevel diode-clamped converters (DCC). In this paper, a novel carrier-based voltage balance method is proposed to balance the dc-link capacitors of five-level DCCs. The proposed method is characterized by injecting proper zero-sequence voltages in the modulation signals of carrier-based modulators. The effects of the injected zero-sequence...
The voltage source inverters operating in islanded microgrid are used as sources of power similar to synchronous generators (SG) in conventional power system. Unlike synchronous generators, these inverters neither have a natural droop (P-f and Q-V) characteristics nor rotational inertia. The electrical time constant is much lesser than mechanical time constant and hence the load changes will show...
This paper presents the application of a robust nonlinear optimal controller for regulating the active and reactive power in a grid-connected three-phase inverter, which includes an LCL filter to mitigate the total harmonic distortion. The optimal control law is derived from the Hamilton-Jacobi-Bellman equation for state-dependent coefficient factorized nonlinear systems. An integral control term...
This paper presents a voltage control strategy for a DC load powered by a three phase inverter connected to a Permanent Magnet Synchronous Generator (PMSG). The DC load consists of a DC capacitor in parallel with the inverter and the unknown current load. The control strategy is designed based on Simple Adaptive Control (SAC) technique. The structure is a cascade controller designed in rotor reference...
This paper proposed an unequal zero voltage vector distribution modulation strategy to suppress the zero-sequence current of five-phase open-winding fault-tolerant fractional-slot concentrated-winding interior-permanent-magnet (FTFSCW-IPM) motor driving system with common DC bus. Compared with the conventional eliminating common-mode voltage vectors modulation strategy, this method can well suppress...
This paper presents a high-power-density high-power-factor GaN-based two-stage electrolytic-free offline LED driver. The LED driver achieves high power density through the use of a hybrid film-ceramic stacked switched capacitor (SSC) energy buffer, and a comprehensive optimization methodology that evaluates various converter topologies and designs, and minimizes overall system volume while maintaining...
The open-ended winding configuration allows feeding an electric motor from two sides. If one of them is connected to an inverter closed on a floating capacitor, operating as an active power filter, it is possible to obtain several benefits over the traditional configuration, such as an extended field weakening speed range and a lower current ripple. However, the additional converter causes switching...
This paper proposes a multilevel open-end six-phase motor drive. The system is composed of six isolated three-leg inverters and is adequate for high-power systems with voltage rating restrictions. The system model and a simple space vector pulse-width modulation (PWM) based on three similar individual planes are presented. Specific voltage vector application sequences that reduce the stator voltages...
In automotive testing systems, effective and efficient control strategies are required to control the induction motor drives so that fast torque response and low torque ripple can be obtained. The fast torque response can be obtained by using predictive current control (PCC) due to its high bandwidth over a wide speed range; and the torque ripple can be reduced by using open-end winding induction...
With the improvement in the power electronic technologies, medium voltage dc (MVDC) electrical distribution systems are being considered for on-shore and off-shore applications. These future MVDC electrical distribution systems are expected to provide the possibility of easy interfacing of the renewable energy sources, improving the dynamics of the system and also help in reducing the carbon footprint...
The accurate and fast detection of the grid voltage attributes (e.g. frequency and amplitude) are gaining more attention in microgrids due to the new stringent amendments to the microgrid standards. In this paper, two novel observer based techniques are introduced; one for estimating the frequency and another for the amplitude of the grid voltage. The proposed observer techniques offer superior performance...
This paper presents a technique to balance inductor currents of parallel-operated unipolar-PWM inverters. Firstly, the problem of unbalanced currents in parallel-operated unipolar-PWM inverters is defined and analyzed in the paper. Secondly, a technique to eliminate unbalanced currents is proposed. The proposed technique only requires one more current sensor in an inverter module rather than changing...
Input current of a Current Fed Switched Inverter (CFSI) contains the switching frequency component (75 kHz) and a second harmonic component of line frequency (100 Hz) apart from the DC part. In prior designs, the second harmonic component was suppressed by increasing the size of passive components (inductor or capacitor), which makes the inverter implementation bulky. This paper presents a control...
Large-scale penetration of power electronic based systems demands the need for sophisticated control algorithms. Conventional current control techniques may not give the required dynamic performance for modern power electronic systems. This paper designs an online supplementary adaptive dynamic programming (ADP) controller based on neural networks which improves the dynamic performance of a conventional...
Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids...
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