Papers by Keyword: Three-Level

Abstract: The realization method of the explosion-proof three-level frequency conversion equipment for coal mine is introduced in this paper. The frequency conversion equipment uses diode clamped three-level inverter unit topology structure, it overcomes some disadvantages of two-level converter that harmonic content of voltage output is higher, electromagnetic interference is serious and on-off loss is higher. The frequency conversion equipment is suitable for coal mine high voltage and large power devices such as draught fan, pumps and belt conveyers.

Abstract: A novel three-phase three-level inverter circuit with asymmetrical legs is proposed. The new prototype is very effective and efficient for improving the quality of the inverter output voltage. Firstly, the structural parts of the inverter are briefly described, then switching strategy and operational principles of the proposed inverter are explained and operational topologies are given. The proposed topology reduces the number of switches, losses, installation area and converter cost. Finally, the simulation and experimental results are provided to validate the effectiveness and advantages of the proposed configuration.

Abstract: To adapt to the requirements of the charging and discharging of the lithium battery, the paper presents a three-level based bidirectional energy storage converter topology.It has strong adaptability and can manage the charge and discharge of multi-series and parallel battery module. The mathematical model of the converter is analyzed, and the two operation modes of the converter control strategy are studied; Analysis the feed-forward decoupling control of three-level rectifier, and the variable scale factor is used to control midpoint potential. The simulation results demonstrate the feasibility of the design.

Abstract: This paper analyzes the mathematical model of the three-level PWM rectifier in the three-phase stationary coordinate system and the two-phase synchronous rotating coordinate system. On this basis, the synchronous PI current double closed-loop decoupling control strategy is used to eliminate the impact between the d-q axis and relieve independent control of two axes. In order to simplify the complexity of the vector synthesis, the three-level space vector modulation (SVPWM) algorithm is studied. Transform the three-level space reference vector synthesis to the two-level. The mathematical model of the theoretical analysis are verified with Matlab/Simulink. The simulation result demonstrates that the design method is reasonable and effective, which makes the PWM rectifier excellent dynamic and static performance.

Abstract: In this research, a high-voltage direct current zero voltage switching (ZVS) PWM half-bridge converter is proposed. The parameters of the converter as follows: the input voltage is up to 4000V;the output voltage is 600V.The new ZVS PWM TL converter has neutral point clamping diodes and flying capacitor. This research is going to analyze the working principle of circuit witch thus realizing the zero voltage switching and the circuit parameters selection. Moreover, circuits simulation is carried out by MATLAB to verify the reliability and feasibility of this DC/DC converter topology.

Abstract: According to the active circulating current existing in the three-phase three-level modular photovoltaic grid-connected system, an equivalent model of the active circulating current is built on the basis of the topology and control of the modular system, and the exciting source and the impedance are analyzed in detail. One kind of current-sharing loop is proposed. The error between the average reference current and the feedback current with PI controller is added to the output of the DC voltage loop. Thus the impedance of the active circulating current is enhanced within low frequency range and the active circulating current is reduced effectively. Lastly, A 10kW three-phase three-level modular photovoltaic grid-connected system is built, and experimental results demonstrate the correctness of the model analysis and reduction methods.

Abstract: An equivalent model is established for zero-sequence circulating current (ZSCC) in three-phase three-level modular photovoltaic grid-connected system, and ZSCC is classified by frequency into high-frequency and low-frequency components. A parallel solution based on improved LCL filter is proposed to reduce high frequency component of ZSCC, and the low-frequency component of ZSCC can be reduced by using the ZSCC controller. The ZSCC model analysis and reduction methods are verified by experimental results based on a 10 kW three-phase three-level modular photovoltaic grid-connected system.

Abstract: Three-level is widely applied in the high-power medium-voltage system and in which SVPWM algorithm is the key part. While the three-level algorithm can be simplified into two-level space-vector modulation algorithm based on reference voltage decomposition, it makes the application that active area vector on three-level to be a probability. It breaks the three-level allocation time down into two-level and the inherent relationship between the active area vector and the traditional SVPWM algorithm is analyzed. Non-midline current direction detection method is used in neutral point potential control of active area vector method for three-level. Simulation and experimental results verify the availability of the novel methodology.

Abstract: Brushless doubly-fed machine (BDFM) is a new type of AC induction motor.It has a good applicable prospect as the variable frequency motors or the variable speed constant frequency generators. Although the advantage of the three-level inverter, there are also some problems of neutral point voltage balance in this method such as the unbalance of neutral point voltage. And the traditional principle of Three-level inverter space vector pulse width modulation method is to estimate the sectors and calculating a lot of trigonometric functions. To solve these problems, a novel method for the virtual space vector concept in G-H coordinate system is presented in this paper. The method proposed can omit the judging process of the sectors, reduce the calculating burden, and maintain the balance of neutral-point voltage between capacitances within a certain index modulation. The results of simulation are given to validate the improved virtual space vector modulation.

Abstract: Compared to the traditional dual Z-source inverter, Z-source inverter with a signal X-shaped LC impedance network has advantages of lower cost and an easier modulating algorithm. Based on the three-level single Z-source inverters, this paper proposed a suitable SVPWM scheme, which include vector region judgment, send order determine, and synthetic time calculation. It is available to achieve inductive voltage boosting by inserting the shoot-through vectors appropriately, while simultaneously provide a good performance on output with a correct volt-second average. The theoretical concepts discussed are verified by simulation results.