Search

Summary: Battery energy stored single‐phase quasi‐Z‐source inverter photovoltaic (BES‐qZSI‐PV) power system shows many advantages in comparison with other tri‐port inverter‐based PV power systems. However, the existing BES‐qZSI‐PV power system does not work at night or cloudy day because of its circuit limitation. This paper proposes a 24‐h operational BES‐qZS‐PV system by the following approaches: (1) the main power circuit is proposed for the day and night operation; (2) the detailed circuit models including the DC model and the second‐harmonics ripple model are built by considering scenarios of day and night operations; (3) the design method of quasi‐Z‐source network parameters is proposed to meet the requirement of day and night operations; and (4) the control strategy is proposed to achieve the high‐performance system operation all the time and seamless transition between day and night operation. After theoretical modeling and analysis, the built models are verified by comparing their calculation results with the circuit‐based simulation and experimental results. The proposed single‐phase BES‐qZSI‐PV power system is tested; experimental and simulation results are captured when the system operates in day, night, and transition to validate the proposed 24‐h operational BES‐qZSI‐PV system. [ABSTRACT FROM AUTHOR]

A quasi-Z-source three-to-single-phase matrix converter is proposed with low-frequency ripple power compensation. The employed impedance network between the source grid and the matrix converter extends the voltage gain; meanwhile, it has filtering function. Therefore, voltage step-up devices and an additional input filter are avoided. In addition, for a conventional three-to-single-phase matrix converter, input current of the source grid contains high harmonic components because of double-line-frequency pulsating power produced in single-phase side. A model predictive control-based ripple power compensation system is proposed in this paper to eliminate the low-order harmonic components from the three-phase input currents and voltages. Thus, the impedance parameters could be small in size and value. Simulation and experimental results verify the analysis and control of the proposed topology. [ABSTRACT FROM PUBLISHER]

The battery energy-stored quasi-Z-source (BES-qZS)-based photovoltaic (PV) power generation system combines advantages of the qZS inverter and the battery energy storage system. However, the second-harmonic ( \text2\omega ) power ripple degrades the system's performance and affects the system's design. An accurate model to analyze the \text2\omega ripple is very important. The existing models did not consider the battery, or assumed a symmetric qZS network with $L_{{1}}= L_{{2}}$ and $C_{{1}}= C_{{2}}$, which limits the design freedom and causes oversized impedance parameters. This paper proposes a comprehensive model for the single-phase BES-qZS-PV inverter system, where the battery is considered and there is no restriction of $L_{{1}}= L_{{2}}$ and $C_{{1}}= C_{{2}}$ . Based on the built model, a BES-qZS impedance design method is proposed to mitigate the \text2\omega ripple with asymmetric qZS network. Simulation and experimental results verify the proposed \text2\omega ripple model and impedance design method. [ABSTRACT FROM AUTHOR]

Through coupling the impedance network between the grid and the conventional indirect matrix converter (IMC), the LC-filter-integrated quasi-Z-source (qZS) IMC overcomes the 0.866 voltage gain limitation of the conventional IMC and also avoids the input filter that is required to mitigate current harmonics of the conventional qZS matrix converters. This paper further investigates the voltage boosting and LC filtering function of the LC-filter-integrated qZS IMC. The voltage gain, the filtering function, and qZS network parameters design are presented using a small-signal model and circuit analysis. Simulation and experimental results validate the built model, the voltage gain analysis, and the parameters design of this type of qZS IMC. The input current of the LC-filter-integrated qZS network is compared to the conventional Z-source and qZS IMCs to investigate the integrated LC filtering capability. The experimental results verify that the LC-filter-integrated qZS network provides the necessary filtering function. Thus, the traditional input filter can be eliminated, which reduces the cost, power loss, volume, and weight for the overall system, when compared with the other conventional topologies that require the input filter, even those with impedance-source networks. [ABSTRACT FROM PUBLISHER]

The second harmonic pulsating power flows through the dc side of a single-phase quasi-Z-source inverter (qZSI), which requires bulky capacitor banks and inductors to suppress low-frequency ripple of dc-link voltage and inductor currents in the passive ripple reduction way. However, the resultant huge qZS network seriously deteriorates the system reliability, efficiency, volume, weight, and cost. This paper proposes an active-filter-integrated single-phase qZSI to transfer low-frequency power ripple directly from ac load to active filter's ac capacitor, so that low-frequency power ripple does not present in dc side anymore and constant inductor currents and constant capacitor voltages are ensured. Thus, much small qZS impedance is employed to only smooth high-frequency ripple and active filter's capacitor supports ac voltage (large ripple allowed) with small capacitance. The operation principle, parameter design method, and modeling and control strategy of the proposed topology are investigated. Comparative evaluation, simulation, and experimental results verify the proposed new topology system. [ABSTRACT FROM PUBLISHER]

The active power filter (APF) that consists of a half-bridge leg and an ac capacitor is integrated in the single-phase quasi-Z-source inverter (qZSI) in this paper to avoid the second harmonic power flowing into the dc side. The capacitor of APF buffers the second harmonic power of the load, and the ac capacitor allows highly pulsating ac voltage, so that the capacitances of both dc and ac sides can be small. A model predictive direct power control (DPC) is further proposed to achieve the purpose of this new topology through predicting the capacitor voltage of APF at each sampling period and ensuring the APF power to track the second harmonic power of single-phase qZSI. Simulation and experimental results verify the model predictive DPC for the APF-integrated single-phase qZSI. [ABSTRACT FROM PUBLISHER]

A hybrid pulsewidth modulated single-phase quasi-Z-source grid-tie photovoltaic (PV) power system is proposed. The hybrid pulse-width modulation (HPWM) combines the pulse-width modulation (PWM) and the pulse-amplitude modulation (PAM). The PWM works when the ac output voltage is lower than the dc source voltage; otherwise, the PAM operates the single-phase quasi-Z-source inverter (qZSI). The HPWM leads to the reduction of power loss, and the quasi-Z-source capacitance and inductance. An effective control strategy is proposed for the new PV power system to manage the maximum power point tracking (MPPT) of PV panel, grid-tie power injection, and dc-link voltage. A grid-tie current controller, combining a repetitive controller and a proportional-resonant regulator, achieves strong harmonic suppression, fast dynamic, and zero tracking error. A 500-W prototype is built to verify the new system. Power loss estimation and impedance design are detailed. Experimental tests validate the HPWM, new PV power system with higher efficiency, and the related control method. [ABSTRACT FROM PUBLISHER]

An effective control method, including system-level control and pulsewidth modulation for quasi-Z-source cascade multilevel inverter (qZS-CMI) based grid-tie photovoltaic (PV) power system is proposed. The system-level control achieves the grid-tie current injection, independent maximum power point tracking (MPPT) for separate PV panels, and dc-link voltage balance for all quasi-Z-source H-bridge inverter (qZS-HBI) modules. The complete design process is disclosed. A multilevel space vector modulation (SVM) for the single-phase qZS-CMI is proposed to fulfill the synthetization of the step-like voltage waveforms. Simulation and experiment based on a seven-level prototype are carried out to validate the proposed methods. [ABSTRACT FROM PUBLISHER]