Design, Assembly and Testing of Modular Multilevel Converter with Multicarrier PWM Method

Abstract

Reliable electrical power is a milestone for modern society and economy. Multilevel power converters represent a potential breakthrough in employing switching converters for flexible ac transmission system and custom power application. This paper present the design and realization of the prototype of a 1,5 kW mono phase 5-level cascaded inverter with PWM modulation. The prototype has been tested and the output waveforms have been investigated. The results conflrm the goodness of these devices in synthesizing a desired ac voltage from several level of dc voltage with a good control of the frequency, the voltage output (including phase angle) and the active reactive power flow.

Review of technologies for DC grids – power conversion, flow control and protection

“…Without dedicated active or passive countermeasure, the MMC arm or common-mode currents may contain some parasitic components such as 2 nd order harmonic current that could increase semiconductor losses and cell capacitor voltage ripple. The main attributes and drawbacks of MMCs are [20][21][22][23][24][25][26][27]:…”

“…Without dedicated active or passive countermeasure, the MMC arm or common‐mode currents may contain some parasitic components such as second‐order harmonic current that could increase semiconductor losses and cell capacitor voltage ripple. The main attributes and drawbacks of MMCs are [20–27]: The MMC generates sinusoidal output voltages, with near‐zero harmonics and extremely low‐voltage stresses (d v /d t ) on the interfacing transformer; thus, ac filters and phase interfacing reactors are not needed. Besides the known attributes of conventional VSCs {xx], the circuit structure of the MMC permits the power rated and dc operating voltage of VSC‐HVdc links to be increased to a level comparable with that of conventional of line commutated converter (LCC)‐HVdc links; and internal fault management, which is necessary for continued operation during cell failure (cell capacitors or switching devices). Moreover, the use of distributed cell capacitors in MMCs reduces the first peak (or transient component) of the let‐though currents that may flow in the DCCB before its opening; thus, allowing DCCB design requirements to be relaxed. …”

“…Fig. 1 shows the modular multilevel converter [20][21][22][23][24][25][26][27]. Each phase-leg of the MMC comprises of upper and lower arms, and each arm consists of 'N' cascaded cells such as in Fig.…”

FPGA‐based implementation for improved control scheme of grid‐connected PV system with 3‐phase 3‐level NPC‐VSI

“…The 2DoF-PI provides an extra parameter for faster and smoother set-point tracking as well as better noise-rejection 11 which enhances the flexibility of the control structure unlike that in 1DoF-PI. A 5-level-cascaded multilevel topology has been investigated in Balzani et al 17 and Luchetta et al, 18 but the control circuit complexity increases with the increase in levels and also the capacitor voltage unbalancing problem has not been investigated. The derivative term is realized using a derivative gain along with a low pass filter that aids in attenuation of high frequency noise.…”

“…The Flying capacitor attributes modular structure and finds comparatively less industrial significance. A 5-level-cascaded multilevel topology has been investigated in Balzani et al 17 and Luchetta et al, 18 but the control circuit complexity increases with the increase in levels and also the capacitor voltage unbalancing problem has not been investigated. Details related to the various modulation techniques used like the Phase-Shifted, Level-Shifted, Space Vector PWM, and Selective harmonic elimination have been discussed in Rodriguez et al 19 Various topologies of multilevel converters and their specific applications and drawbacks have been presented in Leon et al 20 Reviewing the work reported, it can be concluded that the 3-level NPC stands to be a popular configuration owing to its lesser number of devices and capacitors that aids in attaining capacitor voltage balancing which is otherwise difficult in its higher level counterparts.…”