Conference Paper

Analysis of DC-Link capacitor losses in three-level neutral point clamped and cascaded H-Bridge voltage source inverters

Univ. of Southampton, Southampton, UK
DOI: 10.1109/ISIE.2010.5637820 Conference: Industrial Electronics (ISIE), 2010 IEEE International Symposium on
Source: IEEE Xplore


Loss estimation is a critical aspect of inverter design. The present work investigates the losses occurring in the DC-link capacitors of the three-phase three-level Neutral Point Clamped and Cascaded H-Bridge inverter topologies, by performing a harmonic analysis of the capacitor currents. Results are verified by simulations. Their analysis reveals the advantage of the NPC inverter.

Download full-text


Available from: Suleiman Sharkh, Apr 13, 2015
  • Source
    • ", [16], transistors in Fig. 4 connected to the output nodes (V LX(A,B) ) are fast-switching devices, whereas switches connected to the DC-link V DD , V MID and GND voltages are the slow-switching devices. Idealized switched-mode simulation of the DC/AC inverter from Fig. 4 is shown in Fig. 5. Here, we can see that during the first half-period Φ = H, the output voltage Fig. 5 "
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a topology of a single-phase floating full-bridge three-level PWM power inverter suitable for high-voltage / high-power DC-AC conversion. High power efficiency is obtained thanks to the slow (50/60Hz) biasing of the H-bridge power supply terminals, allowed by a particular arrangement and control of two complementary active neutral point clamped (ANPC) voltage source converters. As result, the main PWM switching voltage as well as the maximum drain-source voltage V DSS of related transistors are reduced to one-half of the input V DD voltage. This is allowed by the internally generated and accurately balanced middle-node voltage V DD /2. Consequently, advantageous r DS(on) of the low-voltage transistors, along with reduced switching PWM voltage result in considerable decreasing of power losses in whole output power range. This paper introduces the main concept of the floating H-bridge topology, and presents in detail the circuit realization. The performances are demonstrated on 450V DC /230V AC 2kW power inverter exhibiting 98.6% peak efficiency and realized in very small 100x60x30mm 3 volume. Index term—high voltage DC/AC power inverter, (A)NPC full-bridge power inverter, non-isolated power inverter. Single-phase NCP power inverter.
    Full-text · Article · Sep 2015 · IEEE Transactions on Power Electronics
  • [Show abstract] [Hide abstract]
    ABSTRACT: Nowadays, the three-level neutral point clamped (3L-NPC) inverter has become more attractive among multilevel inverters topologies, especially in transformerless grid connected photovoltaic systems. Due to the unbalance between the two DC load-side capacitor voltages, the development and improvement of such topology were important topics in recent studies. New structures were derived focusing on better distribution of losses, increasing efficiency, decreasing the switching devices losses and the conduction losses. For this reason, seven derived topologies are discussed in this paper and compared among the conventional inverter. In addition, a part of this study focuses on modifying modulation techniques in order to comply with the neutral point fluctuation problem. Several carrier-based PWM and space vector modulation techniques are considered, discussed and compared.
    No preview · Conference Paper · Apr 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Cascaded H-bridge (CHB) inverters used in high-voltage variable frequency drives are usually composed of several power cells. Each power cell consists of a three-phase uncontrolled rectifier as its input stage and a single-phase inverter as its output stage. It is difficult to obtain the analytical expression of the dc-link capacitor current because of both the nonlinear characteristics of the uncontrolled rectifier and the low-frequency harmonics caused by the single-phase inverter. On the other hand, exact analysis of the capacitor current is important for dc-link capacitor selection. This paper proposes an analytical method for calculating the capacitor current. Considering both the input current of the inverter and the output current of the rectifier, an approximately linear equivalent circuit model is established. According to the proposed equivalent circuit model, the analytical expressions of the harmonic spectrum and the root mean square value of the capacitor current are derived. The capacitor ripple voltage is further estimated. Applicable conditions of the proposed method are also presented. This method may be useful when designing dc-link capacitors of power cells in CHB inverters. Simulation and experimental results show that the proposed method can achieve good accuracy in the continuous conduction mode.
    No preview · Article · Dec 2014 · IEEE Transactions on Power Electronics
Show more