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The series resonant DC/DC converter with an isolation transformer and bridge mode inverter input junction, at its operation in the Buck case, is investigated, at that input DC supply circuit comprises the qZ (quasi-Z) link as impedance source. Operation at such Buck case can be provided under different inverter bridge control methods. Recommended by the literature sources, is the method of control...
Nowadays, the inverter technology is widely used in household appliances. This technology may generate disturbance in the frequency range within 9–150 kHz due to its frequency switching. In the shared low voltage network, many appliances can be connected and operated simultaneously causing the interaction between appliances. The disturbance produced by appliance may influence the working performance...
The paper presents four asymmetrical pulse width modulation techniques for three-phase impedance source converters operating at high switching frequencies. The concept behind all proposed methods is to introduce single-phase shoot-trough states and reduce commutation currents of fast-switching SiC MOSFETs. All techniques are explained and verified by means of Saber simulations and laboratory experiments...
A novel Lyapunov function based decentralized control method is proposed for three-phase parallel connected inverters system within islanded micro-grid. A proper voltage regulation and excellent power sharing performance can be well ensured even under unknown line impedance and unbalanced LC filter parameters. Moreover, high reliability and robustness can be guaranteed since no inter-communication...
A dynamic model it is proposed to analyze the stability and the steady-state response of islanded parallel connected inverters controlled by a droop control strategy. The proposed state space model allows to analyze the effects of the virtual impedance loop over the system stability boundaries. Furthermore, it enables to establish a compromise relationship between voltage regulation and the circulating...
In this paper, the inverter control strategy based on Virtual Synchronous Generator (VSG) is analyzed and the power loops of VSG are explained. Then the eigenvalue method of small-signal modeling is used to prove the stability of the VSG. The key parameters including inertial coefficient, exciting coefficient, drooping coefficient and the virtual impedance were analyzed by the eigenvalues and sensitivity...
The performance of reactive power sharing in an islanded microgrid is significantly affected by feeder impedance, mismatch parameters and unbalanced local load. To reduce the negative impact of mismatched link impedance on reactive power sharing, the adaptive virtual impedance strategy for voltage compensation is proposed with paralleled inverters in an islanded mode. The on-line adaptive control...
In modern electric traction drives, on-line monitoring offers the advantage to decrease maintenance cost and increase the reliability. Especially, the electrical insulation is one of the most vulnerable components of an ac machine. Fast switching of the inverter results in high output voltage slew rates increasing the stress on the insulation as well as the rate of deterioration. The described stator...
In previous work, the authors proposed an active common-mode filter (ACF) that is able to reduce the radiated noise from power cables connected to power converters and evaluated its radiated noise reduction effect by using an oscillator as a common-mode (CM) noise source. In this paper, this ACF is applied to a motor drive system fed by a PWM inverter, and the attenuation characteristics of the CM...
In this paper, an advanced droop control using a multinomial model for operating the parallel-connected uninterruptible power supply (UPS) inverters is proposed. To control the parallel inverters without any physical communications, the control method using a P/Q droops is conventionally used. The conventional method droops voltage and frequency using the monomial model. In conventional droop control,...
In order to ensure three-phase grid-connected inverter output voltage symmetry under unbalanced grid voltage, an improved control strategy is proposed in this paper. The proposed control strategy includes power, voltage and current three loops. The complex coefficient-filter (CCF) is used to obtain the positive and negative sequence of unbalance output voltage and current during the grid faults. By...
Three phase inverters, which are widely used in motor drive systems, produce high level electromagnetic interference (EMI). To evaluate EMI performance in the design phase is of great importance. In this paper, computer-aided time-domain simulation, which is straightforward and convenient is used followed by fast Fourier transform (FFT) approach. The simulated common mode (CM) and differential mode...
Under the condition of low short circuit capacity and high grid impedance of weak grid, the grid voltage is easily fluctuated due to the load change, affecting the power quality of the grid. In view of this problem, firstly, this paper analyzes the principle of the grid-connected voltage change caused by the load change. Secondly, an improved voltage-power control method (PQ-U) for three-phase grid-connected...
In this paper the conducted emissions generated by an inductive power transfer (IPT) system composed of an array of magnetically coupled stranded-wire resonators and powered by an H-bridge inverter (operating at a resonant frequency of 147kHz) are assessed for arrays with different numbers of resonators, different termination impedances and for a constant power of 5W absorbed by the termination impedance...
In the paper a simple stability-equivalent single- inverter system is proposed to analyze the stability of the complex multi-inverter system. Investigation shows that the harmonic resonance even instabilities will be triggered with the increase of the paralleled inverter quantities or the grid inductance due to the interaction between the inverter admittance and the grid admittance. From the perspective...
The high line impedance and load fluctuations of weak grid can easily lead to grid voltage fluctuations and other issues. In order to make the grid-connected PV inverter have strong robustness and improve the dynamic response speed, the active power control method of PV inverter based on passive theory is proposed. Firstly, the control strategy of the power outer loop is given, and the Euler-Lagrange...
For a wireless power transfer system, when the transmission distance is long, the power is low in the case of low coupling coefficient. In order to solve this problem, a new compensate topology of primary side based on parallel T-type structure is proposed. The circuit structure and impedance characteristics of the system are analyzed, the compensation circuit can be used to make the primary side...
This paper presents a broadband Doherty power amplifier (DPA) design with two continuous Class-F-1 matching circuit eliminating offset line in carrier way to increase the bandwidth and efficiency. By employing this compact and highly efficient design method, a DPA working at 2.0 GHz∼2.6 GHz is designed and implemented for verification. With continuous wave (CW) measurements, the experimental results...
In this paper, proposed an adaptive droop control method using estimated the line impedance in real time and compensate for the mismatch in voltage drops across line impedance, to enhance reactive power sharing accuracy in island microgrids. The block of line parameter estimation using the current and voltage parameters in the microgrid and estimation algorithm recursive least squares method (LSM)...
In this paper, a reactive power sharing strategy that uses droop controller combined with virtual impedance and estimating the voltage drop due to the line impedance to improve significantly improves the reactive power control and sharing accuracy. Because of, with a given minimum allowable voltage of system, the voltage droop slope cannot be made arbitrarily large, so this paper presents a better...
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