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A neutral point voltage-balancing control algorithm is proposed for a neutral-point-clamped (NPC) three-level photovoltaic (PV) grid-connected inverter. The mathematical model of the neutral point current was deduced. The influence on the neutral point voltage for discontinuous pulse width modulation(DPWM) methods was analyzed. Comparison of the error between feedback neutral point voltages and the...
A novel Z-source dual-bridge matrix converter (ZSDBMC) topology and its control strategy are proposed to overcome two main drawbacks of conventional matrix converters: low immunity to abnormal input voltage disturbance and low voltage transfer ratio. The boost voltage characteristic of Z-source network is utilized to improve the system voltage transfer ratio and make it immune to abnormal input voltage...
A novel generalized method of discontinuous pulse width modulation (DPWM) strategies such as DPWM0, DPWM1, DPWM2, DPWM3, DPWMMAX and DPWMMIN usually called as DPWMx is proposed in this paper to minimize the switching loss for three-phase voltage source inverters. Six sectors are re-carved up into twelve ones. Analyzing and summarizing all kinds of conventional DPWMx strategies, come to a conclusion...
To solve the problems of large flux and torque ripples and inconstant switching frequency in direct torque control (DTC) for permanent magnet synchronous motors (PMSM) and to eliminate speed sensor since it deteriorates system reliability and increases the cost of system, a novel speed sensorless DTC method based on space vector modulation (SVM) is proposed in this paper. This method is based on the...
A novel digital phase-locked-loop (DPLL) method is proposed for single-phase grid-connected power generation systems in this paper. It consists of a grid voltage feed-forward network and a fictious instantaneous power feedback correction network. The fundamental signal of the grid voltage is extracted by a digital Butterworth filter to generate a unity sine reference signal for the feed-forward network,...
The unitary power factor control for distributed grid-connected power generation systems is considered in this paper, i.e., the fundamental-frequency positive-sequence components are extracted from the utility voltages under unbalanced and distorted conditions and output currents of the grid-connected power inverter are always in phase with the corresponding positive-sequence voltages. The extracted...
The single-mode overmodulation strategy of matrix converter is put forward for the lower voltage transfer ratio. Single-mode overmodulation strategy and its effect on increasing voltage transfer ratio are analyzed theoretically, and the simulation model of the strategy is set up. Theoretical analysis and simulation results show that the proposed strategy can make the voltage transfer ratio rise to...
In order to solve the stability problem caused by the parameter mismatch of filter inductance for a conventional predictive current control, a predictive current control method based on on-line parameter estimation of filter inductance is proposed in this paper. The average filter inductance value is calculated in each cycle of grid voltage by means of the average inductance model and phase-locked-loop...
As the conventional matrix converter has the drawback of low voltage ratio (max. 0.866), a novel matrix converter called z-source matrix converter is proposed, According to the topology of the different main circuits, they are called z-source indirect matrix converter (ZSIMC) and z-source direct matrix converter (ZSDMC). The basic configuration of the new topology and their fundamental principle are...
In general, the active frequency drift (AFD) method is used to detect the islanding phenomenon for the distributed grid-connected power system. However, when the angle of the current disturbance matches with the load angle in the range of the non-detecting zone (NDZ), AFD method cannot identify the islanding. In order to solve the above problem, an improved AFD method based on the alternate current...
This paper introduced a simple but effective three-level SVPWM algorithm. On the basis of this algorithm, a simple neutral-point balancing and narrow-pulse elimination algorithm without current sensor is proposed, and dead time is compensated in the algorithm also. The result of test verified that this algorithm is simple to be carried out, harmonics in output waveform are small, neutral-point potential...
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