Tuyen D. Nguyen

Modulation Strategies to Reduce Common-Mode Voltage for Indirect Matrix Converters

Common-mode voltage (CMV) is responsible for overvoltage stress to the winding insulation and bearing damage of an ac motor. High dv/dt of CMV raises leakage currents, which can cause serious problems such as motor damage and electromagnetic noise to the equipment installed near the converter. This paper proposes two modulation strategies for indirect matrix converters that substantially eliminate CMV. The first method is developed by using the suitable couple of nonzero space vectors instead of zero space vectors in the inverter stage. The maximum voltage transfer ratio of this method is unaffected and remains 0.866. The second one, which is useful for low-voltage operation, is approached by choosing the medium and the lowest positive line-to-line input voltages in the rectifier stage to generate the dc-link voltage and by placing suitable zero space vectors in the inverter stage. In the second method, the maximum voltage transfer ratio is 0.5. Both methods can mitigate the peak value to 42%. In addition, while the first method provides the same performance to the conventional method, the second method can reduce significantly the harmonic components of line-to-line output voltage. Simulation and experimental results are shown to verify the effectiveness of the proposed methods.

A New SVM Method for an Indirect Matrix Converter With Common-Mode Voltage Reduction

A new space vector modulation (SVM) process for use in an indirect matrix converter (IMC) has been proposed in this paper to reduce the common-mode voltage (CMV) in a high voltage transfer ratio. The principles of selecting suitable active vectors and then properly arranging the switching sequence in the inverter stage of the IMC are described. The IMC with the new SVM method significantly reduces the peak-to-peak voltage of the CMV without any extra hardware. The new SVM method has some other advantages such as a lower total harmonic distortion of line-to-line output voltage and a reduced switching loss at the inverter stage through a minimum number of switching commutations as compared to the conventional reduced CMV-SVM method. The proposed modulation can be easily implemented in software without any additional hardware modifications. Both simulation and experimental results are shown to demonstrate that the new SVM method can generate good performance of the input/output waveforms and provide CMV reduction.

Dual Three-Phase Indirect Matrix Converter With Carrier-Based PWM Method

This paper proposes an indirect matrix converter (IMC) topology with dual three-phase outputs and its effective carrier-based pulse width modulation (PWM) method. The proposed IMC topology can independently supply ac power for two three-phase loads from a single three-phase ac power source. This converter consists of a rectifier stage used in traditional three-phase IMC and a five-leg inverter. Besides a proposed IMC topology, the carrier-based PWM method suitable for this converter is also introduced. The proposed PWM method is easily implemented by using only one symmetrical triangular carrier signal to generate the PWM signals for a rectifier and five-leg inverter. Proposed IMC topology features the advantages of conventional three-phase IMC, such as sinusoidal input/output current waveforms, controllable input power factor, and simple commutation at the rectifier stage. Analysis, simulation, and experimental results are provided to demonstrate the advantages of the proposed IMC topology with dual three-phase outputs and to validate the effectiveness of the applied modulation strategy.

An adaptive carrier-based PWM method for four-switch three-phase inverter

This paper proposes an adaptive carrier-based pulse width modulation (PWM) for four-switch three-phase inverter. The balanced output currents are guaranteed by this proposed method instead of voltage oscillations across two dc-link capacitors. The linear over-modulation can be easily obtained with this new approach. Simulation and experimental results are shown to validate the feasibility of the proposed method.

Development of a Three-to-Five-Phase Indirect Matrix Converter With Carrier-Based PWM Based on Space-Vector Modulation Analysis

This paper proposes an indirect matrix converter (IMC) topology to supply a five-phase load directly from three-phase ac power sources without bulky electrolytic capacitors and explains its operating principle. Using the emerging topology, which combines the five-leg inverter into the rectifier stage of the conventional IMC, the three-to-five-phase IMC topology reduces the number of power switches and results in a simpler commutation compared with the conventional three-to-five-phase direct matrix converter. In addition, a simple approach to realize the carrier-based pulsewidth modulation (CBPWM) method for a three-to-five-phase IMC is presented, and the proposed CBPWM method is analyzed based on the space-vector approach. As a result, the IMC with the proposed CBPWM method can be more easily implemented compared with IMCs with the space-vector PWM method. A three-to-five-phase IMC control platform is realized by coordinating a TMS320F28335 DSP (Texas Instruments) with an EPM7128SLC84-15 field-programmable gate array (Altera). The simulation and experimental results are provided to verify the effectiveness of the CBPWM strategy.

Carrier-based PWM technique for three-to-five phase indirect matrix converters

Nowadays, multi-phase machines drives are considered in many applications, particularly for medium and high power application. This paper focuses on the three-to-five phase indirect matrix converter topology and the carrier-based PWM technique. This converter has the same characteristics as a conventional three-to-three phase indirect matrix converter such as sinusoidal input/output current waveforms, unity input power factor, no intermediate capacitor, simple commutation. The outputs of this converter are five phases with variable amplitude and frequency to supply a five-phase load. The carrier-based PWM technique is also proposed in this paper to control the three-to-five phase indirect matrix converter with the maximum voltage transfer ratio up to 0.7886. The proposed modulation method is developed from the study of a five-phase two-level voltage source inverter control. The algorithm can be easily implemented without computational complexity. Simulation and experimental results show the feasibility of the three-to-five phase indirect matrix converter and the proposed modulation technique.

Carrier-based PWM method for four-leg very sparse matrix converter

The matrix converters are a good alternative to back-to-back converter in variable speed AC generation to supply energy to a stand-alone load or grid. In case of the unbalanced load, the four-leg matrix converter is required because this topology can effectively provide a path of neutral current. In this paper, a carrier-based PWM modulation is proposed to control the four-leg very sparse matrix converter. The proposed method has less computation complexity for digital signal processor. The algorithm uses only one carrier signal to generate PWMs for both rectifier stage and inverter stage control. The simulation and experimental results are provided to validate the feasibility of the proposed method.

Carrier Phase-Shift PWM to Reduce Common-Mode Voltage for Three-Level T-Type NPC Inverters

Common-mode voltage (CMV) causes overvoltage stress to winding insulation and damages AC motors. CMV with high dv/dt causes leakage currents, which create noise problems for equipment installed near the converter. This study proposes a new pulse-width modulation (PWM) strategy for three-level T-type NPC inverters. This strategy substantially eliminates CMV. The principle for selecting suitable triangle carrier signals for the three-level T-type NPC is described. The proposed method can mitigate the peak value of CMV by 50% compared with the phase disposition pulse-width modulation method. Furthermore, the proposed method exhibits better harmonic spectrum and lower root mean square value for the CMV than those of the reduced-CMV method on the basis of the phase opposition disposition PWM scheme with modulation index higher than 0.5. The proposed modulation can easily be implemented using software without any additional hardware modifications. Both simulation and experimental results demonstrate that the proposed carrier phase-shift PWM method has good output waveform performance and reduces CMV.

An approach of sparse matrix converter using Z-source network

This paper presents an approach of sparse matrix converter (SMC) using Z-source network. The SMC is implemented by connecting a controllable rectifier and the traditional inverter through a Z-source network. The Z-source can produce any desired output voltage by controlling the shoot-through time. Compare to the traditional three-phase SMC, the three-phase Z-source SMC has the same number of switches, however, this topology extends output voltage range. In this paper, the new modulation algorithm is applied for the rectifier stage to generate a constant local average dc-link voltage. The input power factor is nearly unity in the whole operating system. Analysis, simulation and experimental results are provided to demonstrate advanced features of three-phase Z-source SMC.

Adaptive Carrier-based PWM for a Four-Switch Three-Phase Inverter under DC-link Voltage Ripple Conditions

This paper proposes an adaptive carrier-based pulse width modulation (PWM) method for a four-switch three-phase (4S3P) inverter under dc-link voltage ripple conditions. The proposed method guarantees balanced output currents despite of the existence of the voltage oscillations across two dc-link capacitors. And also, this new approach achieves a linear over-modulation with calculation time reduction. Simulation and experimental results are given to validate the feasibility of the proposed method.