Ultra Sparse Matrix Converter Research Articles

Switching Strategy to Reduce Inductor Current Ripple and Common Mode Voltage in Quasi Z-Source Ultra Sparse Matrix Converter

This paper aims to reduce the ripple current in the inductor used in a Quasi Z-source Ultra Sparse Matrix Converter (QZSUSMC). The main limitations of the conventional Ultra Sparse Matrix Converter (USMC) are limited voltage gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(\leq 0.866)$</tex-math></inline-formula> and high common mode voltage (CMV). By integrating a quasi Z-source network in the DC link of USMC and providing a shoot-through (ST) state in a switching cycle, a voltage gain greater than unity can be achieved. Inductors are magnetised during the ST state and demagnetized during the nonshoot-through (NST) state. Hence with a proper arrangement of the ST and NST states, ripple in the inductor current can be minimised. In the proposed modulation, the total ST time is divided into six unequal parts and arranging them to minimize the inductor ripple current. in addition to it, proposed method also offers proper switching arrangements by using active vectors to attenuate peak-peak common mode voltage (CMV). As compared to the earlier reported methods, the proposed method produces a better inductor current ripple and a reduced peak of the CMV. Simulation and developed testing circuit results show the effectiveness of the proposed method.

A Novel ultra sparse matrix converter as a power transferring device for gearless wind energy conversion systems based on renewable energy applications

The most promising renewable resource in today's world is solar and wind, where the growth of wind energy is remarkable. A quasi Z source converter embedded with an ultra sparse matrix converter created here as a novel topology for gearless power transfer. Interfacing the wind energy generator with the existing grid, an ultra sparse matrix converter is constructed with a low number of power electronic semiconductor switches. A quasi Z source network has been introduced in front of the converter for boosting the voltage. A space vector modulation method is constructed to realize high compatibility and a minimized switching loss matrix converter. A design thinking approach has characterized the problem identification in wind energy conversion systems and its proposed solution. The simulation result depicts a high-performance proposed structure. Its control strategy provides a high boosting capacity voltage with gearless power transfer.

A New Type of Super-Sparse Matrix Converter with Γ Source and Its Characteristics Analysis

To solve the problem of low voltage transmission in ultra sparse matrix converter (USMC), a novel ultra sparse matrix converter (USMC) is proposed. The new USMC topology contains of a Γ source boost circuit in the DC link. By increasing the output voltage of DC link, the inverter stage can output higher voltage, thus widening the range of voltage transmission ratio. Furthermore, combined with the SVPWM modulation strategy, the voltage transfer ratio of the new USMC topology is derived, which lays a theoretical foundation for the application of USMC. Finally, Matlab / Simulink simulation results verify the correctness and feasibility of the topology.

Extended Range of Ultra Sparse Matrix Converter Using Integrated Switched Capacitor Network

Ultra sparse matrix converter (USMC) is known for ac-ac conversion with sinusoidal input currents, output voltages, and variable frequency operation. However, its operation is restricted for voltage gain up to 0.866 and load power factor angle up to 30° along with requirement of protection circuit for pulsating loads. This paper proposes switched capacitor USMC to overcome the restrictions of USMC with improved performance. Experimental results are provided to evaluate the converter capability and behavior under balanced and unbalanced input voltage conditions. Furthermore, the proposed converter is compared with the other counterparts.

High-Gain-Integrated Switched Capacitor Indirect Matrix Converter

An ultrasparse matrix converter (USMC) is a derived form of an indirect matrix converter having a less number of switches. Even though it has unidirectional power flow capability, it is a quite appropriate candidate for specific applications, such as wind-energy systems, electrohydrostatic actuators, variable speed drives, and so on. However, the gain of the converter is still limited irrespective of various topological and control strategy modifications. Unlike the previous propositions, this paper is primarily focused on the integration of a switched capacitor boost network within the USMC to enhance gain, by preserving the advantages of the USMC. For controlling the proposed converter, a modified space vector modulation technique is also presented in this paper. In order to explore the potential of the proposed converter, analytical expressions are derived. The theoretical findings are further verified using simulation and experimental results.

Modulation Techniques for Common-Mode Voltage Reduction in the Z-Source Ultra Sparse Matrix Converters

Common-mode voltage (CMV) is known as a major cause of premature motor failures. The form and amplitude of the CMV generated by any converter depends on both the circuit topology and modulation technique. Among single stage ac–ac converters employed in drive applications, the Z-source ultra sparse matrix converter (ZSUSMC) is a desirable choice due to reduced number of switches in its structure and voltage boosting capability. Based on these considerations, this paper aims to: 1) theoretically determine and compare the CMV of the ZSUSMC with four well-known impedance networks, namely, cascaded, switched-inductor, quasi, and series, in its structure and 2) propose modulation techniques for CMV reduction in the ZSUSMCs. To this end, first, it is shown that the ZSUSMC, depending on the impedance network used in its structure, provides more freedom to choose from redundant switching states compared to the ultra sparse matrix converter. Then, by taking advantage of this feature, novel modulation strategies that attenuate the CMV without affecting the boosting capability are developed. The proposed modulation schemes are based on avoiding the switching states most contributing to the CMV during a switching period. Through hardware-in-the-loop studies, the effectiveness of the proposed modulation strategies in reducing the CMV of the ZSUSMCs is verified.

A Multimode Space Vector Overmodulation Strategy for Ultrasparse Matrix Converter With Improved Fundamental Voltage Transfer Ratio

In order to increase fundamental voltage transfer ratio for ultrasparse matrix converter, a novel multimode space vector overmodulation strategy is proposed. First, the relationship among voltage transfer ratio (VTR), the output voltage harmonic distortion rate under three inverter modulation methods and the input current harmonic distortion rate under two rectifier modulation methods is analyzed. After that, according to minimum principle of output voltage and input current harmonics, the three overmodulation modes are divided: the output voltage minimum-phase-error, input current minimum-magnitude-error (MME), and output voltage MME overmodulation strategies are realized in overmodulation mode I, II, and III, respectively. The proposed multimode overmodulation strategy not only extends the maximum VTR to 1.05, but also reduces the output low-frequency harmonic voltage components of the overmodulation mode I and mode II. In addition, the harmonic components of output voltage and input current in overmodulation mode are analyzed by double Fourier integral transform method. Finally, the effectiveness of the proposed multimode overmodulation strategy and the correctness of harmonic analysis method are verified by experiments.

Improved Design and Space Vector Modulation of a Z-Source Ultrasparse Matrix Converter: Analysis, Implementation, and Performance Evaluation

Space vector modulation (SVM) of a Z-source ultrasparse matrix converter (ZSUSMC) can be realized by either using or not using a zero state in the space vector rectification. In this paper, these two modulation schemes are investigated for a cascaded ZSUSMC. It is demonstrated that the input current under the modulation scheme without a zero state is nonsinusoidal, and its harmonics content depends on the output and impedance network inductor currents. In addition, restrictions on operation of the ZSUSMC with low voltage gains are unveiled. Next, aiming at improving the input current quality and suppressing the harmonics content to an acceptable level, an approach for design of the cascaded Z-source network is proposed. Furthermore, an optimal switching pattern, which results in minimum possible number of changes in the switching states of the ZSUSMC, is developed. Using the developed switching pattern, an approach for digital implementation of the SVM schemes on a single conventional digital signal processor (DSP) without employing an additional field programmable gate array is proposed. Hardware-in-the-loop studies of the ZSUSMC modulated under the proposed SVM schemes are carried out to verify their digital implementation feasibility on a conventional single DSP, as well as effectiveness in producing high-quality input/output currents.

An In-Depth Investigation of a Z-Source Ultrasparse Matrix Converter in Buck and Boost Modes of Operation

Z-source networks are recently being employed to enhance the boosting capability of matrix converters. This paper concentrates on cascaded Z-source ultrasparse matrix converter (ZSUSMC), where the Z-source network is placed between the three-switch input rectifier stage and the six-switch output inverter stage. Two space vector modulation schemes, with and without a zero state in the rectifier stage modulation, are presented and their advantages and disadvantages are discussed. In addition, restrictions imposed on the converter operation in buck mode, which arise from unidirectional nature of the ultrasparse matrix converter, are discussed and a solution is proposed for offsetting those limitations. Furthermore, an optimal switching pattern, which results in minimum possible number of changes in the switching states as well as even distribution of the shoot-through state over the entire control period, is proposed. Also, common-mode voltages of the converter in all possible switching configurations are calculated. Hardware-in-the-loop studies of a ZSUSMC-based permanent magnet synchronous motor drive are carried out to evaluate the performance of the drive under the proposed modulation techniques. The obtained results are compared with a recent study and the superiority of the proposed method in terms of converter input/output current quality is demonstrated.

Direct Torque Control Strategy of PMSM Employing Ultra Sparse Matrix Converter

Matrix converter is a good choice for Permanent Magnet Synchronous Motor (PMSM) drives, because it has high power density and does not require dc-link energy storage. the disadvantages of conventional matrix converter is using 18 active switches, so it becomes expensive and the modulation method becomes more complicated than back to back converter. To minimize this problem, this paper proposes variable speed drive of PMSM using Ultra Sparse Matrix Converter (USMC) based on Direct Torque Control (DTC) methods. This converter uses only 9 active switches, making it cheaper than conventional matrix converter. DTC is designed based on Space Vector Modulation (SVM) to reduce torque and flux ripples due to the hysteresis control in conventional DTC. The simulation results show that DTC based SVM using USMC effectively controls the rotor speed with low torque and flux ripples.

Harmonic Spectrum of Output Voltage for Space Vector Pulse Width Modulated Ultra Sparse Matrix Converter

In a matrix converter, the frequencies of output voltage harmonics are related to the frequencies of input, output, and carrier signals, which are independent of each other. This nature may cause an inaccurate harmonic spectrum when using conventional analytical methods, such as fast Fourier transform (FFT) and the double Fourier analysis. Based on triple Fourier series, this paper proposes a method to pinpoint harmonic components of output voltages of an ultra sparse matrix converter (USMC) under space vector pulse width modulation (SVPWM) strategy. Amplitudes and frequencies of harmonic components are determined precisely for the first time, and the distribution pattern of harmonics can be observed directly from the analytical results. The conclusions drawn in this paper may contribute to the analysis of harmonic characteristics and serve as a reference for the harmonic suppression of USMC. Besides, the proposed method is also applicable to other types of matrix converters.

Space-Vector Overmodulation Strategy for Ultrasparse Matrix Converter Based on the Maximum Output Voltage Vector

In this paper, a space-vector overmodulation strategy for an ultrasparse matrix converter (USMC) is proposed. The maximum output voltage vector, which has the same phase as reference voltage, is derived accurately in space-vector modulation. According to the maximum output voltage vector, the overmodulation mode I and mode II are re-divided, the boundary voltage transfer ratio (VTR) of which is extended to 0.954, whereas the maximum VTR of USMC remains 1, and the low-order harmonic components are reduced effectively. The overmodulation strategies in both modes are realized, respectively, by the linear superimposed principle. In addition, the harmonic characteristics of output voltage in overmodulation mode are analyzed by the double Fourier integral transform method. It is shown that the output voltage contains not only $({\rm 6} z_{1}\pm 1) f_{\rm{out}}$ harmonics, but also ${\rm{\vert }} f_{\rm{out}} \pm 6 z_{2}f_{\rm{in}}{\rm{\vert }}$ and $\vert (6z_{1}\pm 1) f_{\rm{out}} \pm 6 z_{2}f_{\rm{in}}{\rm{\vert }}$ harmonics. The effectiveness of the proposed overmodulation strategy and the correctness of harmonic analysis method are verified by experiments.

Research on Linear Output Voltage Transfer Ratio for Ultrasparse Matrix Converter

Many existing research works of ultrasparse matrix converter (USMC) show that the maximum linear output voltage transfer ratio (MLO-VTR) is less than 0.866, however, this paper proves that based on space vector modulation, MLO-VTR for USMC can break the ultimate value. First, based on the condition that input power factor is one, the maximum output voltage within one carrier period and the maximum linear output voltage are derived. Further, the mathematical equations among MLO-VTR, the output/input frequency ratios, and the output voltage initial phase are also derived. After that, by solving the operating limits of the mathematical relationship of the MLO-VTR, we can obtain the maximum value of MLO-VTR under different output/input frequency ratios which can be more than 0.866. Finally, all of theoretical derivations are verified by experiments.

Harmonic suppression modulation strategy for ultra‐sparse matrix converter

This study presents two improved modulation strategies for ultra-sparse matrix converter to solve the problem of high total harmonic distortion (THD) under the circumstance of low-voltage transfer ratio. When the load power is low, the first strategy reselects the medium and the lowest positive line-to-line voltages to synthesise a lower dc-link voltage. Thus, the same output performances with the increased voltage transfer ratio will be achieved, and the THD of output voltage is decreased effectively. The second strategy is realised by rearranging the sequences of active vectors in rectifier stage and by adding suitable zero space vectors in inverter stage to widen pulses. Thus, the number of narrow pulses is decreased and the THD of output voltage then will be further reduced. Under the condition of normal operation of the load, both proposed strategies can improve the input and load currents without increasing the switching losses. The improved strategies are proposed for the application of AC motor speed regulation, and can be easily implemented in software with no need of any additional hardware modifications. Experimental results are given to verify the feasibility and effectiveness of the proposed strategies.

ENGLISH

2 ABSTRACT: Artificial Neural Networks (ANN) is introduced by McCulloch and Pitts in 1943. It is an interconnected group of nodes. Neural networks models in artificial intelligences are usually referred to as artificial neural network. A novel unity power factor battery charger conception based on an Ultrasparse Matrix Rectifier (USMR) with Artificial Neural Network (ANN) is presented in this paper. Ultrasparse matrix converter topology can be derived from Indirect converter topology having a reduced number of input switches. The circuit has only three switching components and low-energy- conversion loss. This reduces the cost and enhances the system's efficiency for high voltage battery. Thus, the proposed ANN controller improves the line power quality and delivers admissible output power to the battery. The charging method chosen is the Constant Current (CC) or Constant Voltage (CV) method. The ANN control and space vector modulation algorithms are implemented with the Digital Signal Processor.

Bidirectional output stage matrix converter applied to a distributed generation system

In this article a new bidirectional output stage ultra-sparse matrix converter (BOSUMC) is presented. This converter is designed for connecting a hybrid electrical system to a distributed generation network. The proposed converter comprises an input stage and an output stage with six bidirectional switches in such a way that both the input and output stages are linked with a DC link, which can be coupled to an electrolyser and a fuel cell. The converter allows the current to flow in both ways in its output stage, and if there is an excess of energy in the network, it can be transformed into electric direct current and later into hydrogen for its exploitation. For verifying the control algorithm of the BOSUMC, a laboratory prototype has been prepared using among other elements a Spectrum Digital eZdsp™ TMS320F2812 card.

Novel Three-Phase AC–AC Sparse Matrix Converters

A novel three-phase ac-ac sparse matrix converter having no energy storage elements and employing only 15 IGBTs, as opposed to 18 IGBTs of a functionally equivalent conventional ac-ac matrix converter, is proposed. It is shown that the realization effort could be further reduced to only nine IGBTs in an ultra sparse matrix converter (USMC) in the case where only unidirectional power flow is required and the fundamental phase displacement at the input and at the output is limited to plusmnpi/6. The dependency of the voltage and current transfer ratios of the sparse matrix converters on the operating parameters is analyzed and a space vector modulation scheme is described in combination with a zero current commutation method. Finally, the sparse matrix concept is verified by simulation and experimentally using a 6.8-kW/400-V very sparse matrix converter, which is implemented with 12 IGBT switches, and USMC prototypes.

Analytically Closed Calculation of the Conduction Losses of Three-Phase AC-AC Sparse Matrix Converters

For three-phase a.c.-a.c. power conversion a conventional matrix converter (CMC) or a d.c. side connection of a current DC link rectifier and a voltage d.c. link inverter comprising no energy storage components in the d.c. link could be employed. The combination of d.c. link converters does show a lower number of turn-off power semiconductors and, therefore, has been denoted as Sparse Matrix Converter (SMC) or Very Sparse Matrix Converter (VSMC). A limitation of the phase displacement of the current and voltage fundamentals at the input and at the output to ± π/6 does allow a further reduction of the system complexity, accordingly the respective topology has been introduced in the literature as Ultra Sparse Matrix Converter (USMC).In this paper a novel concept for the analytical calculation of the current stresses on the power semiconductors of the Sparse Matrix Converter Topologies (SMC, VSMC, and USMC) is proposed. As a comparison to a digital simulation shows, the analytical results do show a very good accuracy in a wide modulation range and for widely varying load current phase angle and widely varying ratio of output and mains frequency. Therefore, the analytical results provide an excellent basis for the dimensioning of the SMC, VSMC or USMC and/or for the determination of the rated output power and efficiency which could be achieved by employing given power transistors and diodes.