Two-stage Matrix Converter Research Articles

A Sinusoidal Doubly Salient Electromagnetic Machine Drive Fed by Third-Harmonic Injection Two-Stage Matrix Converter With Integrated Injection Inductor

This manuscript studies a sinusoidal doubly salient electromagnetic machine (SDSEM) drive fed by third-harmonic injection two-stage matrix converter (3TSMC) with integrated injection inductor to improve the power density of the whole system. First, compared with the conventional matrix converter (MC), the 3TSMC suffers from larger volume due to the inductor in the harmonic current injection circuit. In the proposed system, the harmonic injection current is synthesized by the field current of SDSEM and the injection inductor is removed. Then, the control strategy is proposed to decouple the current injection control and field current control, which means that the harmonic current and the field current can be regulated flexibly. Finally, a prototype is built to evaluate the proposed system and control strategy. Furthermore, the proposed 3TSMC-fed drive with the corresponding control strategy is also suitable for the other DC-excited three-phase sinusoidal AC machines, such as wound rotor synchronous machines.

Control Scheme Based on Improved Odd-Harmonic Repetitive Control for Third-Harmonic Injection Two-Stage Matrix Converter

The third-harmonic injection two-stage matrix converter (3TSMC) not only inherits the advantages of the conventional two-stage matrix converter (TSMC), but also has simple modulation strategy and low switching losses. The injection current control is the key to achieving sinusoidal input currents of 3TSMC. The injection current reference consists of the third harmonic and its odd harmonics, making it difficult to obtain high control accuracy with a proportional integral (PI) controller. In this paper, a control scheme is proposed for the injection current of 3TSMC, which consists of an improved odd-harmonic repetitive controller (IORC), a PI controller and a feedforward controller. Compared with the conventional repetitive controller (CRC) and existing odd-harmonic repetitive controllers (ORC), the IORC has the highest gains and bandwidths at odd-harmonic frequencies, offering the proposed control scheme high control accuracy and fast transient response. The stability conditions of the system with the proposed control scheme are analyzed, and the design guidelines for the control parameters are provided on this basis. The experimental results demonstrate the effectiveness of the proposed control scheme.

Modulation Strategy for the 3TSMC to Suppress Mains Current Sector-Switching Distortions Under Capacitive Input Power Factor Angles

In this paper, a modulation strategy is proposed for the third-harmonic injection two-stage matrix converter (3TSMC) to suppress the mains current sector-switching distortions under capacitive input power factor angles. First, it is revealed that when the 3TSMC operates under non-unity input power factors, the injection current has control errors after sector switching, which cannot be completely solved by optimizing the controller. Second, the mechanism that the injection current control errors lead to the mains current distortions is analyzed, and the shapes of distortions are summarized. Then, a novel switching pattern is introduced for the input voltage selector (IVS) of the 3TSMC, which can weaken or even offset the distortions generated by the control errors under capacitive input power factor angles. The proposed modulation strategy inserts this switching pattern into the original switching sequence with a suitable duty cycle after sector switching, thus suppressing the distortions. Finally, experimental results are presented to verify the validity of the proposed modulation strategy.

Mains Current Distortion Analysis and Suppression Method for Third-Harmonic Injection Two-Stage Matrix Converter

Compared with the direct matrix converter and the two-stage matrix converter (TSMC), the third-harmonic injection TSMC (3TSMC) has significant advantages in the input reactive power control range and the maximum linear voltage transfer ratio. However, for nonunity input power factor operations and high-mains-frequency applications, there are input current distortions in the 3TSMC. Further analysis reveals that the actual injection current cannot track the reference without error in the conventional harmonic current injection circuit, resulting in the current distortions. Therefore, an improved circuit is proposed, which is based on the asymmetric H-bridge and does not need extra energy storage components or current sensors. The injection current in the improved circuit can follow the reference without error by injection current modulation, which means that the input current distortions are suppressed significantly. All theoretical considerations are verified by experimental results taken on a 3-kVA prototype.

Improved Third-Harmonic Injection Two-Stage Matrix Converter Topology Based on Decomposition Control of Injection Current

In this article, an improved topology of the third-harmonic injection two-stage matrix converter (3TSMC) is proposed, which not only ensures that the input reactive power control capability is independent of the voltage transfer ratio (VTR) and the load conditions but also achieves high-quality mains current waveforms. To solve the problem of injection current control error in nonunit input power factor operation of 3TSMC, the third-harmonic injection current is decomposed into the active and reactive components, which are, respectively, controlled by the original injection current control bridge arm and an additional bridge arm named reactive power control bridge arm (RB). The maximum current of the inductor of RB is equal to the absolute value of the required input reactive current amplitude and will not increase with the increase of the VTR. The design criteria of the inductor of RB are discussed. To ensure the closed-loop stability under two injection directions, the controller of the injection current reactive component is designed. The effectiveness of the proposed topology and control strategy is verified by the experimental results.

Harmonic Analysis and Attenuation Strategy for a Two-Stage Matrix Converter Fed by Dual-Inverter Based on Pulse Barycenter Method

Since the DC-link of the dual-inverter two-stage matrix converter (TSMC) has no energy storage element, its grid-side current waveform is closely related to the load-side condition. The conventional modulation strategy of the dual-inverter TSMC is only the stack of the double inverters, without considering the cooperation between both modulation strategies. Thus, the fluctuations in the grid-side currents synthesized by both load-side currents will be obvious. To solve this problem, this paper analyzes the effect of the current pulse position on the grid-side current waveform quality, and relevant relationship between the pulse position and current harmonics is obtained according to Fourier transform. On this basis, the harmonic attenuation strategy for the dual-inverter TSMC is proposed. In the proposed strategy, the grid-side current harmonic is reduced based on the optimal duty-cycle combination, obtained from the harmonic optimization problem. The simulation and experimental results are provided to verify that the theoretical analysis of grid-side current harmonic content is consistent with the actual condition, and the proposed modulation strategy can effectively reduce the grid-side current harmonic.

Vector Modulation-Based Model Predictive Current Control with Filter Resonance Suppression and Zero-Current Switching Sequence for Two-Stage Matrix Converter

This paper proposes a novel model predictive current control scheme for two-stage matrix converter. The switching frequency is kept constant by fixing the switching instant. The control strategy achieves to control source reactive power in the input side and output currents in the output side. In addition, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, a zero-current switching sequence is proposed and implemented to insure zero-current switching operations and reduce the switching losses. Furthermore, in order to suppress the input filter resonance, which is easier to be inspired by the model predictive control, compared with traditional control strategies, an innovative active damping technique is proposed and implemented. Finally, both simulation and experiment are implemented to verify the performance of the proposed strategy. The results demonstrate that the control system features both good steady and transient performance.

A Novel Predictive Control Method with Optimal Switching Sequence and Filter Resonance Suppression for Two-Stage Matrix Converter

This paper proposes a vector modulation-based model predictive current control strategy for a two-stage matrix converter. The switching frequency is kept constant by fixing the switching instantly. The control scheme controls the source reactive power on the input side and output currents on the output side. Besides, the advantage of the proposed strategy compared with conventional model predictive control is firstly proved using the principle of vector synthesis and the law of sines in the vector distribution area. Moreover, to ensure zero-current switching operations and reduce the switching losses, an optimal switching sequence is proposed and implemented. Furthermore, considering that the input filter resonance is easier to be inspired by the model predictive control, compared with conventional linear control strategies, an innovative active damping technique is proposed to suppress the input filter resonance. To assess the performance of the proposed method, simulation and experimental results are demonstrated, showing that the control system features both good steady-state and transient performance.

Mains Current Distortion Suppression for Third-Harmonic Injection Two-Stage Matrix Converter

The third-harmonic injection two-stage matrix converter (3TSMC) not only possesses the advantages of a TSMC, but also enhances the input reactive power control capability. Due to the input current deviation caused by the voltage ripple across the input filter capacitors, the mains currents of the 3TSMC are distorted at sector boundaries. To improve mains current quality, this article proposes a mains current distortion suppression method for a 3TSMC, which adds a prefilter to the output side of the input voltage selector to reduce the input current harmonics. As a result, the input filter capacitor voltage ripple and the input current deviation are reduced. The details of design of the prefilter are explained mathematically. To compensate for the dc-link voltage variation after topology improvement, an algorithm based on calculation of the voltage drops across the prefilter inductors is proposed, which can further improve the mains current performance. The feasibility of the proposed method is verified by simulation and experimental results.

Y-Source Two-Stage Matrix Converter and Its Modulation Strategy

Aiming at the defect of low voltage transfer ratio of two-stage matrix converter(TSMC), the proposed topology combines the Y-source network with the TSMC to form the Y-source two-stage matrix converter(YSTSMC) in this paper, and proposes its modulation strategy. The Y-source network is located in the dc-link of TSMC, and uses a tightly coupled inductor with three windings to transfer energy, which can increase voltage transfer ratio. Based on the mathematical model of the Y-source network, a small-signal model is established and dynamic analysis is performed. The analysis result of the impact of the output voltage of the rectifier stage on the output voltage of the system can be obtained. The space vector pulse width modulation (SVPWM) strategy is proposed to control YSTSMC, and according to the fluctuation of dc-link voltage, the modulation ratio of inverter stage is corrected in real time. By analyzing the voltage transfer ratio of YSTSMC, and the calculation expression of the maximum voltage transfer ratio is obtained. Finally, the experimental results are provided to verify the feasibility and validity of the proposed method.

Carrier‐based PWM control strategy for Z ‐source two‐stage matrix converter

In the Z -source two-stage matrix converter (ZSTSMC), the unique shoot-through state of the Z -source network can increase the voltage transfer ratio. Its maximum value can reach 4.33. In order to solve the complexity of space vector pulse width modulation (SVPWM) for ZSTSMC, a carrier-based PWM (CBPWM) control strategy is proposed. The duty ratios of the rectifier stage and inverter stage are calculated by the SVPWM method. A carrier is constructed and combined with duty ratios to produce regular modulation waves of rectifier stage and inverter stage. Then, the inserted mode of the shoot-through state is optimised by analysing. The position of its insertion is adjusted so that the expressions of the shoot-through modulation wave is simple and regular. And the number of modulation waves is reduced from 5 to 4. Next, the modulation waves are compared with a carrier to obtain pulse signals which are used to produce driving signals through logic operation. The ZSTSMC is controlled by this strategy to obtain three-phase symmetrical sinusoidal input and output waveforms. The proposed method is identical in output to the SVPWM method. Finally, the experimental results are provided to verify the feasibility and validity of the proposed method.

Carrier‐based PWM modulation strategy for dual‐output two‐stage matrix converter

In order to solve the complexity of the space vector pulse width modulation (SVPWM) strategy for dual-output two-stage matrix converter (DO-TSMC), this study proposes a carrier-based PWM (CBPWM) strategy. The topology of DO-TSMC is introduced, and the principle of alternating SVPWM between two groups of inverters is analysed. The inverter stage switching modulation sequence is optimized by reasonable selection and distribution of zero vectors. Based on the above analysis, according to the expressions of duty ratios and the carrier, the modulation waves of the rectifier stage and inverter stage are deduced. All the modulation waves are simple and regular, without trigonometric function calculations, and no sector judgments are required. The proposed CBPWM strategy is easily implemented by using only one symmetrical triangular carrier to generate the PWM signals for the rectifier stage and inverter stage. Furthermore, based on this strategy, a modified CBPWM strategy is proposed, which assigns the action time of each inverter according to the proportional coefficient. It can adjust the output voltage range of the two inverters flexibly. Finally, the experimental results are provided to verify the feasibility and validity of the proposed method.

Application Research of Chaotic Carrier Frequency Modulation Technology in Two‐Stage Matrix Converter

The harmonics of line to line voltage in two‐stage matrix converter (TSMC) with fixed carrier frequency had discrete and high values and produced powerful electromagnetic interference (EMI). In this paper, chaotic carrier frequency modulation technique (CCFMT) was applied in TSMC for the first time to spread sideband range and suppress harmonic peak value. Although this technique could suppress EMI, it would increase the probability of narrow pulses. In order to improve reliability, the rectifier in the two‐stage matrix converter uses PWM modulation with zero vector to extend the zero current commutation time, solves the narrow pulse problem, and simplifies the commutation process. At last, an experiment platform was designed and experimental results showed that harmonics of line to line voltage was efficiently suppressed.

Control method for the two‐stage matrix converter to enhance the linear voltage transfer ratio

The relatively low-linear voltage transfer ratio (VTR) is considered an intrinsic drawback of the conventional two-stage matrix converter (TSMC). However, the studies demonstrate that the linear VTR of the third-harmonic injection TSMC (3TSMC) can push this limit. After reviewing the operating principles and modulation strategy of 3TSMC briefly, the VTR characteristic of 3TSMC is analysed and a control method to enhance the linear VTR is proposed. With the developed method, the maximum linear VTR can break through the intrinsic limit and VTR > 0.866 can be achieved by regulating the input reactive power under arbitrary output conditions theoretically. Finally, simulations and experimental results verify the correctness of the theoretical analysis, and the comparison of 3TSMC and other TSMCs with improved VTR demonstrates the effectiveness of the proposed method.

Modelling and analysis of a NTVV-SVM based three-level twin-step matrix converter

Recently the tremendous advancement has been seen in the field of matrix converter topology. For high power drive applications, industries often need high power AC-AC converters like three level matrix converter because it is having the ability to generate a set of balanced sine waves for inputs as well as outputs. The three level matrix converters possess better output performance with reduced harmonic contents compared to all two-stage indirect matrix converters. In this matrix converter topology, the idea of neutral-point clamped-VSI is employed to the inversion step of the matrix converter circuitry. To control the power switches the gate signals are produced using NTVV based space vector modulation. To justify the theoretical study a complete model of a three-level twin-step matrix converter has been designed in Matlab/Simulink and its performances are analysed.

Series Z‐source and nine‐switch dual‐output inverter stage two‐stage matrix converter

Nine-switch dual-output inverter stage two-stage matrix converter (NS-TSMC) has been widely applied in dual AC motors drive system, while it has the shortcoming of low voltage transfer ratio. Based on the NS-TSMC, a modified topology, named as series Z-source and nine-switch dual-output inverter stage two-stage matrix converter (ZS-NS-TSMC), is proposed, in which the series Z-source network is connected between the rectifier stage and nine-switch dual-output inverter stage (NS-DOI). In the presented topology, a brief shoot-through vector is employed, which can improve the voltage transfer ratio. Other advantages of the series Z-source network, such as low voltage stress of Z-source capacitor, zero dead-time of NS-DOI and limiting inrush current at startup, are discussed in the study. Furthermore, the dual space vector modulation is presented, which can achieve the merits of unity input power factor, sinusoidal input and outputs. Besides, the sinusoidal outputs, the capability of boosting voltage and adjustable output voltage amplitude are also discussed by the mathematical proof. Finally, an experimental prototype is set up based on the controllers of TMS320F28069 (DSP) and EPM570 (CPLD), the results of which verify the feasibility and desired advantages of the proposed topology and modulation strategy.

Hybrid Modulation Strategy for Two-Stage Matrix Converter and its Application in Vector Control of Doubly Fed Induction Generator

A hybrid modulation strategy (HMS) for a two-stage matrix converter (TSMC) is presented in this paper. According to the variation of voltage transfer ratio, different combinations of modulation modes for rectifier-side converter (RSC) and inverter-side converter (ISC) of TSMC are adopted. Two different current space vector modulation methods are used for RSC to obtain maximum and minor DC voltages. The power loss of TSMC is reduced based on the minor DC voltage. In addition to the linear space vector modulation for ISC, an overmodulation method is presented in order to increase the voltage transfer ratio of TSMC. HMS ensures smooth switching between different modulation modes and makes the best use of the advantage of these modes. Finally, HMS is applied in the case where TSMC is used as an AC-excitation converter for doubly fed induction generator (DFIG) to achieve maximum power point tracking (MPPT). The simulation results confirm the accuracy and feasibility of HMS and the good performance of the MPPT operation of DFIG excited by TSMC.

Two-Stage Matrix Converter Based on Third-Harmonic Injection Technique

Due to the merits of sinusoidal input currents and excellent conversion efficiency, buck-type active third-harmonic injection converters have received increasing attention in recent years. However, three major problems of these converters still exist in theory and practice. First, the existence of the dc-link capacitor, utilized by early researchers, causes inrush transient and distorts the input currents. Second, in some specific situations, such as wind energy conversion system and flexible ac transmission system, these converters' capabilities of generating input reactive power need sufficient improvements. Third, proper selection of the third-harmonic injection inductor is the key challenge to implement these converters, since the inductor affects not only the current ripple but also the tracking performance of the third-harmonic current. To solve these problems, this paper studies the two-stage matrix converter with third harmonics injection and demonstrates that the dc-link capacitor can be removed by bidirectional implementation and proper control of the rectifier. Then, an algorithm enhancing the input reactive power capability is developed. Thus, sinusoidal input currents are achieved and the reactive power control range is extended significantly. Moreover, the design criteria of the third-harmonic injection inductor are discussed. Finally, the proposed method is verified by simulation and experimental results.

Comparative Study of 2-phase Low Frequency Triac Converter- and High Frequency Two-stage Matrix Converter Systems

The paper deals with comparison of the characteristics between two-phase electronic systems: DC/AC/AC high frequency two-stage converter system made of two single-phase matrix converters with variable orthogonal output and low frequency triac converter with phase-control supplied from AC network. Low frequency triacs or thyristor converters can be innovated using switches of semiconductor device s (IGBT). Design of two-stage DC/AC/AC high frequency converter with two-phase orthogonal output using single-phase matrix converter in half-bridge connection operated with the bipolar PWM is also introduced. Ill. 17, bibl. 10 (in English; abstracts in English, Russian and Lithuanian).

Distortion Analysis and Duty Ratio Correction Algorithm for Asymmetric Modulation of Two-Stage Matrix Converter

When applying the two-stage matrix converter (TSMC) to the aero variable-speed constant-frequency generation system, the high input frequency varying between 360 and 800 Hz becomes a great challenge to its control. One of the most commonly used modulation methods for TSMC is the dual space vector modulation (DSVM). Simulation and experiments show that despite its advantages such as simplicity and low switching loss, the asymmetric DSVM causes distortion both in the output voltages and input currents of the TSMC. In this paper, the conception of “pulse orthocenter” (PO) is introduced via a BUCK model, and the influence of PO's fluctuation upon the actual output is revealed. Based on the PO theory, the spectra of TSMC's output voltages and input currents are then analyzed, indicating that asymmetric modulation causes $3n\omega_{\rm in}\pm(3m\pm 1)\omega_{o}$ harmonics in the output voltages and $(3n\pm 1)\omega_{\rm in}$ harmonics in the input currents. In order to suppress these harmonics, a duty ratio correction (DRC) algorithm is proposed to improve the waveform quality without increasing switching loss. The DRC formula is provided and the available range of related parameters discussed. The correctness of distortion analysis is testified via simulation, and the validity and feasibility of the DRC algorithm is verified via experiments.