Mohamed A. Ismeil

A Powerful Finite Control Set-Model Predictive Control Algorithm for Quasi Z-Source Inverter

Today, a predictive controller becomes one of the state of the art in power electronics control techniques. The performance of this powerful control approach will be pushed forward by simplifying the main control criterion and objective function, and decreasing the number of calculations per sampling time. Recently, predictive control has been incorporated in the Z-source inverter (ZSI) family. For example, in quasi ZSI, the inverter capacitor voltage, inductor current, and output load currents are controlled to their setting points through deciding the required state; active or shoot through. The proposed algorithm reduces the number of calculations, where it decides the shoot-through (ST) case without checking the other possible states. The ST case is roughly optimized every two sampling periods. Through the proposed strategy, about 50% improvement in the computational power has been achieved as compared with the previous algorithm. Also, the objective function for the proposed algorithm consists of one weighting factor for the capacitor voltage without involving the inductor current term in the main objective function. The proposed algorithm is investigated with the simulation results based on MATLAB/SIMULINK software. A prototype of qZSI is constructed in the laboratory to obtain the experimental results using the Digital Signal Processor F28335.

Experimental studies on a single-phase improved switched inductor Z-source inverter

This paper presents an experimental work on improved SL Z-source inverter topology. Because of the limitations of classical Z-source inverter, the SL Z-source inverter has been proposed to increase the voltage gain and to reduce the voltage stress on the capacitors of the Z-network. The simulation and experimental results show that the improved SL Z-source inverter increases the boost factor, improves the voltage stress across the capacitors, and reduces the inrush current.

Modeling of non-ideal improved Switched Inductor (SL) Z-source inverter

Recently switching inductor Z-source inverter topology has been proposed to increase the boost factor. But the problem of stress on switch and capacitor is still remaining; hence an improved switched capacitor has been proposed to decrease the capacitor voltage stress. To design the control for this topology the transfer function is used. This paper presents the small signal analysis of the new topology; where, the state space averaging method is employed to achieve the transfer functions.

Experimental studies on a three phase improved switched Z-source inverter

This paper presents an experimental verification of the Improved Switched Inductor Z-Source Inverter (ISL-ZSI). The ISL-ZSI has been proposed to overcome the limitations of classical Z-Source Inverter (ZSI) such as lower voltage gain, higher capacitor voltage stress of Z-network and huge inrush current that appears in the case of traditional ZSI. In this paper, different aspects will be presented and analysed such as the PWM control, relationships of voltage boosting gain versus modulation index, voltage stress versus modulation index and output voltage/current. Those important points will be analyzed in detail and verified by simulation and experimentally.

A new switched-inductor quasi-Z-source inverter topology

This paper presents the study of a new switched-inductor quasi-Z-source inverter topology (SL-QZSI) with high boost voltage. The proposed topology is derived from the old quasi-Z-source inverters by replacing of the input side inductor by two additional inductors and three diodes. This inverter has several advantages, such as, lower component ratings, a common ground with the dc source, reduced capacitors voltage stress, reduced inductors current stress, reduced diodes current stress and simplified control strategies. On the other side, the presented topology of the switched-inductor quasi-Z-source inverter allows to avoid the problem faced in the classical topology of quasi Z-source inverters caused by the inrush current at start-up, on the same time a wide range of voltage gain can be achieved to fulfil the applications which require a large gain range, especially for motor controllers and renewable energy systems. Theoretical analysis of the proposed topology voltage boost under the maximum constant boost control methods with third harmonics injection is investigated in this paper. Where, simulation results are presented to verify the proposed concept and the theoretical analysis.

Single-phase self-synchronized synchronverter with current-limiting capability

In this paper, a single-phase self-synchronized inverter with current limiting capability without a dedicated synchronization unit is presented. It offers an approach for power systems to control distributed renewable energy sources. The proposed system has the capability to synchronize itself with the utility grid before connection and track the grid frequency after connection without a phase-locked loop (PLL). Moreover, it provides the synchronverter with a current limiting capability during grid disturbances.

Control of switched-inductor quasi Z-Source Inverter (SL-qZSI) based on model predictive control technique (MPC)

Model Predictive Control (MPC) becomes more prevalent in power converters due to its faster response in tracking the reference values of the controlled variables. In this paper, the MPC is applied on the Switched-Inductor quasi Z-Source Inverter (SL-qZSI) topology. The MPC modeling for the capacitor voltage, inductor current, and output load current of the topology are designed to predict their values in the future. These prediction values are compared with the reference values to compose the cost function and then the switching state is selected to achieve the minimum cost function. The validation of the modeling is investigated by simulation under MATLAB platform. Then, it is also confirmed by experimental work using a laboratory prototype.

Development of MPC algorithm for quasi Z-source inverter (qZSI)

This paper presents an improvement algorithm of Model Predictive Control (MPC) for the quasi Z-Source Inverter (qZSI) with a standalone system. The improved algorithm decreases number of the desired sensors from five into three, where it just needs two current sensors for measuring the AC currents, and another voltage sensor for capacitor voltage detection. The inductor current will be estimated according to the previous optimized state and the capacitor voltage value during this state. Moreover, the developed algorithm decreases the number of the calculations for the inductor current prediction. Thus, the total cost of the control system decreases; furthermore, the practical implementation for the algorithm is improved where short running time. The developed algorithm will be investigated with the theoretical analysis in addition to the simulation validation based on MATLAB/SIMULINK as environmental software.

Grid connection quasi Z-Source Inverter based on model predictive control with less sensors count

this paper presents Model Predictive Control (MPC) to tie three-phase quasi Z-Source Inverter (qZSI) to the utility grid. Regularly, to control the capacitor voltage in qZSI based on MPC, the inductor current is the key factor. Here, the proposed algorithm has the features of decreasing the number of sensors where the inductor current sensor is removed to improve the cost and foot print of the control implementation. The value of the inductor current is defined according to an estimation methodology that uses the previous optimized switching state and the capacitor voltage during this state. In addition, the proposed algorithm has the features of decreasing the number of iteration to improve the response of the control. The proposed technique has been explained in details over theoretical analysis and confirmed with the simulation results utilizing MATLAB/SIMULINK software. Additionally, experimental validation has been presented using the digital signal processor F28335 with hardware setup.

Single-phase virtual synchronous generator without a dedicated synchronization unit

In this paper, a single-phase self-synchronized inverter that mimics synchronous generators (Synchronverter) without a dedicated synchronization unit is investigated. It offers a mechanism for power systems to control distributed renewable energy sources. It can synchronize itself with the grid before connection and track the grid frequency very well after connection without a phase-locked loop (PLL). Removing the PLL from the single phase inverter improves the real power tracking performance, reduces the development cost and improves the software reliability.