A quasi-Z-source active neutral point clamped inverter topology employingsymmetrical/unsymmetrical boost modulation control scheme for renewableenergy resources

Rehan MAJEED, Danial SALEEM, M. Imtiaz HUSSAIN, Muhammad Talha GUL, Muhammad Rehan USMAN, Salman MAJEED
2019 Turkish Journal of Electrical Engineering and Computer Sciences  
This paper proposes a bipolar quasi-Z-source active neutral point clamped inverter (QZS-ANPCI) topology. It acts as a buck/boost inverter (3-phase, 3-level) to integrate renewable energy resources under their fluctuating DC voltages. We propose a symmetrical/unsymmetrical boost modulation control technique to mitigate the DC-link unbalance voltage problem in an ANPC inverter. This worthwhile control technique exploits voltage-current closedloops on AC and DC sides to regulate the desired
more » ... the desired parameters. Moreover, the constant boost control (CBC) modulation has provided a switching sequence that generates a symmetrical/unsymmetrical full shoot-through (FST) state for boosting input DC voltage in the proposed inverter. Detailed loss and efficiency analysis is carried out to show its superior performance under the proposed scheme. Furthermore, the total harmonic distortion (THD) of the proposed QZS-ANPCI meets IEEE Standard-519. Simulink/MATLAB (MathWorks, USA) and PSIM (Powersim, USA) software programs are used to simulate the proposed topology. To verify the theoretical proposals and simulation results, we have developed an experimental prototype setup (1 kW). Both simulation results and experimental data show satisfactory agreement and support the theoretical postulates. Key words: Z-source inverter, quasi-z-source inverter, buck/boost inverter, neutral point clamped inverter, active neutral point clamped inverter integrated with the conventional inverter. It contains capacitors (C) and inductors (L) as passive components. Due to its inherent characteristics, classical converters, such as DC-DC, AC-DC, DC-AC, and AC-AC, can have buck/boost ability working together with the same impedance [3] . An improved form of the ZSI is the QZSI to overcome its problems. There are four distinct QZSI topologies for RERs. These topologies have various advantages, such as a continuous input current, lower component ratings, reduced component count, reduced input source stress, and simplified control strategies compared to the conventional ZSI [4]. There are many pulse-width modulation (PWM) techniques for ZSIs. These techniques include simple boost control (SBC), maximum boost control (MBC), constant boost control (CBC), and developed space-vector pulse width modulation (SVPWM) control. The conventional ZSI topologies have employed modulations in different research works [5, 6]. The most popular multilevel inverter developed to overcome the limitations of VFIs is the neutral point clamped inverter (NPCI). This is because it has lower voltage stresses, switching losses, conduction losses, switching frequency, and THD than those of 2-level inverters [7, 8] . Therefore, it has many applications at medium voltage levels. Furthermore, the authors of [9] applied the z-source impedance concept in NPCI. Also, the works in [10, 11] derived a Z-source NPCI structure to decrease the number of passive components and also proposed a modulation scheme. Due to improved performance of the quasi-Z-source impedance, the works in [12, 13] presented a proposed single-phase quasi-Z-source NPCI and its modulation scheme. To overcome the drawbacks of the traditional Z-source NPCI, the work in [14] also presented two transformer-based z-source NPCI structures. Recently, Yu [15] demonstrated a simulation-based proposed quasi-Z-source NPCI topology with reduced capacitor voltage. Another research study in [16] proposed an LC-switched NPCI topology to reduce the number of passive components. This topology multilevel inverter uses a symmetrical boosting control method (FST). Furthermore, the authors of [17] proposed a 3-level boost PFC converter and control scheme to improve voltage imbalance and zero current distortion. They can feed to linear loads as well as nonlinear loads nonsymmetrically. The authors of [18] developed a PFC rectifier-based multilevel boost converter using a nonsymmetrical active capacitive divider structure. This structure reduces the switching losses and uses a smaller inductor. Also, 4-level operation is achieved instead of 3-level converter operation with the same number of components . Another research study implemented a single voltage source-based DC-link capacitors voltage balancing technique for NPC inverters using an inductor boost topology [19] . This used a single source-based simple DC-DC boost stage at the NPCI input. Recent studies have explored new multilevel boost topologies and control strategies to provide improved performance. The work in [20] developed a single-phase modified quasi-Z-source cascaded hybrid inverter (5level). This uses a greater number of components and uses only a symmetrical boosting technique for a single input source. This is a cascaded topology with a greater number of components. Moreover, a dual-T-type seven-level boost ANPC topology, proposed in [21], provides a scheme for balancing the voltage of floating capacitors (FCs). This scheme feeds to a 3-phase load using a single input source. This converter topology is two-staged dual T-type and increases the complexity. For recent control techniques, the work in [22] proposed a PWM strategy for a cascaded H-bridge inverter to cope with unbalanced DC input sources. This study does not have a voltage boosting stage in cascaded topology. In the same way, the SVPWM technique proposed in [23] can balance neutral point voltage in a low voltage T-type NPC inverter. It generates nonsymmetrical shoot-through states to deal with input voltage
doi:10.3906/elk-1811-168 fatcat:dyrvwmvvj5a7vgxhift2kbxmy4