Asymmetric Cascaded H-bridge Inverter Research Articles

Novel Modulation Scheme for Balancing Power Distribution Among Modules in Nine-Level Asymmetric Cascaded H-Bridge Inverter

When the conventional hybrid frequency (HF) modulation strategy applies to the asymmetric cascaded H-bridge (ACHB) inverter with dc voltage in a ratio of 1:1:2, there are uneven problems of switching loss in low-voltage cells and output power over all operating cells. Thus, a modified HF based on a dual-layer power balance (MHF-DPB) modulation strategy was presented. First, step modulation was still applied to a high-voltage cell on the basis of the conventional method, but improved level-shifted pulsewidth modulation (LS-PWM) was applied to two low-voltage cells. Subsequently, the power balance between high-voltage and low-voltage cells was controlled by adjusting the conduction angles of the power switch and then the carriers of the two low-voltage cells were rotated periodically in order to realize the two low-voltage cells’ power balance. The proposed method can not only realize the power balance of cascaded cells, but also distribute the switching loss of two low-voltage cells equally. In the meantime, it reduced the total switching loss of the inverter. Finally, it was validated by simulation and experimental results.

Electric Boat Propulsion System Using Multilevel Converter Based on ANN Controller

In this system, we use a Multi-level inverter to power an electric boat propulsion system powered by PV Panels. The eleven-level inverter is used to supply power to multi-level switching cells of the inverter which drives the AC motor.It is an Asymmetrical Cascaded H-bridge Inverter. A Multi Carrier PWM signal is given based on Multi Carrier Modulation Technique to obtain equal steps in the eleven-level output. A Sepic converter is used which allows adjustment of a range of DC voltages to provide a constant voltage output. It is a DC converter that basically regulates the voltage from the PV Panel and all subtractive and additive combinations of DC input levels can be obtained in the output signal. ANN controller is applied forming an efficient closed loop system that is involved in the elimination of harmonics in PWM inverters.It reduces the overall Total Harmonic distortion. The system consists of optimized PI based MPPT that ensures efficient PV power generation.

Selective Harmonic Elimination Technique With Control of Capacitive DC-Link Voltages in an Asymmetric Cascaded H-Bridge Inverter for STATCOM Application

In this paper, the selective harmonic elimination (SHE) technique is introduced for a cascaded H-bridge-based static VAR compensator (CHB-STATCOM) with unequal capacitive dc-link voltages. The asymmetric topology allows increasing the number of voltage levels while keeping the converter losses low. Moreover, reactive power control is realized by using the decoupled current control, and the voltage of individual capacitors is controlled by the help of SHE modulation. Mathematical equations are derived for synthesizing the multilevel ac waveform and regulation of dc-link voltages for a CHB inverter with an arbitrary number of H-bridge cells. Then, to verify the theoretical claims, simulation and experimental results are provided for a three-phase CHB inverter with two H-bridge cells in each phase.

Multifunctional Control Strategy for Asymmetrical Cascaded H-Bridge Inverter in Microgrid Applications

A multifunctional control strategy for a single-phase asymmetrical cascaded H-bridge multilevel inverter (ACHMI), suitable for microgrid systems with nonlinear loads, is presented. The primary advantage of ACHMI is to produce a staircase output voltage with low harmonic content utilizing unequal dc voltages on the individual H-bridge cells. In a grid-connected mode of operation, the control strategy of the ACHMI is based on the conservative power theory, providing selective disturbing current compensation besides injecting its available energy. In autonomous mode of operation, two different control methods along with a damping resistor in the filter circuit are developed for regulation of the ACHMI instantaneous output voltage in a variety of load conditions. The first method is a single-loop voltage control scheme without the need of any current measurement. The second one is a multiloop voltage control scheme with a load current feedforward compensation strategy and preservation of the grid-connected current control scheme. The steady-state response and stability of both voltage control schemes are analyzed, and based on the application requirement, the control schemes are implemented individually. The effectiveness of each control strategy is experimentally verified using a hardware-in-the-loop setup with the control algorithm implemented in the TMSF28335 DSP microcontroller.

An asymmetric cascaded H-Bridge inverters for generating 12-sided polygonal space vector diagrams for Motor drives

A new topology of asymmetric cascaded H-Bridge inverter is presented in this paper. It consists of two cascaded H-bridge cells per phase. They are fed from isolated dc sources having a dc bus ratio of 1:0.366. Out of many space vectors possible from this circuit, only those are chosen that lie on 12-sided polygons. Thus, the overall space vector diagram produced by this circuit consists of multiple numbers of 12-sided polygons. With a proper PWM timing calculations based on these selected space vectors, it is possible to eliminate all the 6n ± 1, (n = odd) harmonics from the phase voltage under all operating conditions. The switching frequency of individual H-Bridge cells is also substantially low. Extensive experimental results have been presented in this paper to validate the proposed concept.