An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> This paper presents system modeling, modified space vector PWM implementation (MSVPWM), and control system design of a Z-source converter. For an electrical analysis of the fuel cell powered systems, the fuel cell system is modeled by an R-C circuit including its voltage-current polarization characteristics. A discrete-time state space equation is given to implement digital control and a space vector pulse-width modulation technique is modified to realize the shoot-through zero vectors that boost the dc-link voltage. Three discrete-time controllers and an asymptotic observer are designed. <s> BIB001 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> This paper investigates the modulation schemes of three-level multiphase Z-source inverters with either two Z-source networks or single Z-source network connected between the DC sources and inverter circuitry. With the proper offset added for achieving both desired four-leg operation and optimized harmonic performance, the proposed modulation schemes of four-leg three-level Z-source inverters can satisfy the expected buck-boost operation under unbalanced modulation conditions. Except of the modulation complexity hidden in the four-leg inverters, five-phase three-level Z-source inverters show totally different modulation requirement and output performance. For clearly illustrating the detailed modulation process, time domain analysis instead of the traditional multi-dimensional space vector demonstration is assumed which reveals the right way to insert shoot-through durations in the switching sequence with minimal commutation count. Lastly, the theoretical findings are verified in Matlab/PLECS simulation and experimentally using constructed laboratory prototypes. <s> BIB002 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> Z-source neutral-point-clamped (NPC) inverter has recently been proposed as an alternative three-level buck-boost power conversion solution with an improved output waveform quality. In principle, the designed Z-source inverter functions by selectively “shooting through” its power sources, coupled to the inverter using two unique Z-source impedance networks, to boost the inverter three-level output waveform. Proper modulation of the new inverter would therefore require careful integration of the selective shoot-through process to the basic switching concepts to achieve maximal voltage-boost, minimal harmonic distortion, lower semiconductor stress and minimal number of device commutations per switching cycle. To date, the theoretical background on Z-source NPC modulation has not been fully established, and it is the theme of this paper to propose a number of enhanced voltage-boost pulse-width modulation (PWM) strategies for controlling the Z-source NPC inverter. While developing the PWM techniques, attention has been devoted to carefully derive them from a common generic basis for improved portability, easier implementation, and most importantly, assisting readers in understanding all concepts that have been presented. The presented strategies are also comparatively evaluated to identify their individual advantages and disadvantages, which are subsequently summarized in a comprehensive reference table. Lastly, simulation and experimental results are included for validating the performances and practicalities of the presented modulation schemes. <s> BIB003 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> This paper presents a three-level ac-dc-ac Z-source converter with output voltage buck-boost capability. The converter is implemented by connecting a low cost front-end diode rectifier to a neutral-point-clamped inverter through a single X-shaped LC impedance network. The inverter is controlled to switch with a three-level output voltage, where the middle neutral potential is uniquely tapped from the star-point of a wye-connected capacitive filter placed before the front-end diode rectifier for input current filtering. Through careful control, the resulting converter can accurately produce the correct volt-sec average at its output, while simultaneously achieving inductive voltage boosting. More interestingly, these performance features are achieved with no increase in the number of semiconductor commutations, and hence no increase in switching losses. The proposed converter therefore offers a low cost alternative to sensitive applications that need to ride-through frequent input voltage sags. For confirming the converter performance, experimental testing using a constructed laboratory prototype is performed with its captured results presented in a later section of the paper. <s> BIB004 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> This paper presents a novel space vector pulse width modulation (SVPWM) technique for three phase Z-source inverter. The proposed modified SVPWM has an additional shoot-through state for boosting the dc link voltage of the inverter beside active and zero states. The shoot-through states are evenly assigned to each phase within zero state. So zero voltage period is diminished for generating a shoot-through time, and active states are unchanged. Simulation and experimental results are presented to demonstrate the new features. <s> BIB005 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> This paper presents a hybrid PWM strategy for Z-source NPC converter. The technique combines the space-vector PWM with the ease of implementation of a triangular-comparision PWM. Such strategy reduces the effort of the algorithm calculation. The introduction of the distribution ratio in this technique, allows the development of a systematic approach for implementation of either conventional or any modified vector strategies, even including the shoot-through inherent of Z-source inverter. Also, the paper proposes a simple software algorithm to generate the hybrid modulation for the Z-source NPC inverter. Simulated and experimental results demonstrate the validity of the proposed method. <s> BIB006 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> Three existing and one extended space vector modulations (SVMs) for the three-phase Z-source/quasi-Z-source inverter (ZSI/qZSI) are investigated. The different switching control patterns, the available maximum shoot-through duty ratio, the maximum voltage stress across the switch versus voltage gain, and efficiency are compared in detail. A total average switch device power taking into account the shoot-through current stress is proposed to evaluate the total stress of power switches. Simulation and experimental results of the prototyped qZSI verify the theoretical analysis. The six parts of shoot-through time intervals will reduce the inductor current ripples, and improve the qZSI efficiency. Also, the maximum voltage stress and total average switch power will benefit from the shoot-through division. However, the division method impacts these performances of qZSI. <s> BIB007 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods are compared in terms of theoretical complexity and performance, when applied to the respective switching topologies. Further, this paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response. <s> BIB008 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> A single stage Z-source Neutral-Point-Clamped (NPC) inverter for buck-boost conversion is considered as a better alternative for the two-staged energy conversion in traditional inverters. The Dual Z-Source Network (DZSN) uses two distinct X-shaped impedance networks to connect two individual dc sources to the inverter circuit. The output voltage boosting can be achieved by selectively shooting-through the power sources in the dual networks. This study proposes a novel modulation method for integrating the shoot-through state to the traditional inverter switching. The performance of the proposed modulation method for DZSN is examined utilising attributes which include, voltage boosting, switching losses, efficiency, etc. In addition, this study also deals with non-ideal DZSN, where the circuit resistance and their respective voltage drops are considered. The presented modulation method uses a single carrier signal which is compared with two sets of sinusoidal reference signals to establish the switching. The theoretical findings of the proposed modulation method are verified using Matlab/Simulink and PSIM software. Moreover, an experimental NPC prototype was built and the results for the different values of modulation index are presented, which validate the applicability of proposed modulation method. <s> BIB009 </s> An Overview of Carrier-based Modulation Methods for Z-Source Inverter <s> Reference disposition modulation method <s> A single-impedance network consists of two inductors and capacitors connected in an X-shape to provide single-stage energy conversion. This structure eliminates the need for two-stage energy conversion that is currently employed in traditional converters. A dual-impedance network includes two individual sets of inductors and capacitors connected in parallel. This network possesses the flexibility of using two different sources as inputs to meet the load demand. In order to provide voltage boosting, the switching must be performed selectively to shoot-through (ST) the power sources. A modified modulation method has been implemented to introduce the ST for switching. The modified modulation method shares the operating principle with the in-phase disposition modulation method for multilevel inverters. However, the reference signals are dispositioned via the modified modulation method rather than employing carrier disposition via the traditional modulation methods. Therefore, the circuit analysis of a dual-impedance network is evaluated whose switching is achieved by a modified modulation method for an ideal condition. The simulations are carried out using the MATLAB/PSIM environment and the results are presented. <s> BIB010
This modulation method, which is proposed in BIB009 , uses two reference signals and one carrier signal, in contrary to the aforementioned carrier-based techniques. The two reference signals are level shifted with respect to each other, which when compared to the single carrier signal, provide switching sequence for the N-ST of the inverter. The ST states are introduced using two modified signals that are incorporated using the MCBC method. These modified signals along with reference disposition technique provide switching signals to the inverter. Similar to I-PD LSPWM, the boosting of the voltage in this method is attained by using the N-ST and the combination of LST and UST. V c2 ) are compared to trigger the switches S x2 and S x2′ where x= a, b, c. The circuit enters into the UST state when the upper modified signal (which is equal to or greater than the peak value of the first set of reference signals) is lower than the carrier signal. Similarly, the circuit enters into the LST state when the lower modified signal (which is equal to the lower peak value of the second set of reference signals) is greater than the carrier signal. As discussed earlier, during the N-ST states, switching follows a pattern identical to that of the traditional carrier-based PWM, with the exception that the two reference signals and the carrier signal are compared. The analysis of ideal and nonideal condition of the circuits using RD LSPWM is presented in BIB010 BIB009 . As shown in Fig. 10 , it can be surmised that during the ST states, at least one of the switches in a single-phase leg remains 'off' during all the period. This proves that the voltage boosting by RD LSPWM is achieved by a combination of UST and LST. As the FST states are avoided by this technique, this concludes that the RD LSPWM results in less commutation per switching cycle when compared to POD LSPWM. However, the ST duty ratio is not constant, and this may introduce additional voltage stress on the switching devices. Therefore, based on this analysis, the ST state in two-level and FST, UST and LST states in three-level ZSIs ensure the output voltage boosting of the ZSI. Although FST can be used for boost operation, gating 'on' all inverter switches leads to 'volt-sec error' in the inverter output. Therefore, this state should be avoided. POD LSPWM uses FST states solely, whereas the other two techniques use a combination of UST and LST to perform the inverter operation. Hence, the latter two multi-carrier-based techniques may be considered for the three-level ZSI. A summary of the carrier-based modulation methods for the two-level and multilevel ZSI are tabulated in Table 3 . FST, full shoot through; I-PD LSPWM, in-phase disposition level shifted pulse width modulation; LST, lower shoot through; MBC, maximum boost control; MCBC, maximum constant boost control; POD LSPWM, phase opposition disposition level shifted pulse width modulation; PWM, pulse width modulation; RD LSPWM, reference disposition level shifted pulse width modulation; SBC, simple boost control; UST, upper shoot through; ZSI, Z-source inverter. In addition to the SPWM techniques, Space Vector PWM (SVPWM) techniques are introduced for the two-level BIB005  BIB001 BIB007 and three-level BIB002 BIB004 BIB006 ZSIs. The ST states for the voltage boosting are introduced in the null states of the traditional inverter. Similar to SPWM, the insertion of ST states in any switching cycle remains crucial and needs proper attention. This is to ensure minimum commutation of the switches and the corresponding switching losses. As the focus of the article is the carrier-based comparison methods, further discussion of SVPWM falls beyond the scope of this article. However, the reviews provided in BIB003 and BIB008 may be helpful for the readers to gain a further understanding of the SVPWM techniques for the three-level ZSI.