Goh Teck Chiang

Comparison of Two Overmodulation Strategies in an Indirect Matrix Converter

This paper discusses two overmodulation controls, namely, square wave and trapezoidal, in the indirect matrix converter (IMC) for motor drive application. The differences between these two modulations are analyzed based on the output-input voltage transfer ratio (VTR), the efficiency, and the current total harmonic distortions under two load conditions. Moreover, the performance is then improved by implementing four-step commutation methods in the primary side of the IMC. The validity of the proposed methods will be demonstrated through simulation and experimentally. The experimental results show that the VTR can be improved from 0.866 to 0.97 in the square wave modulation and 0.92 for the trapezoidal wave modulation in an induction motor drive system.

DC/DC Boost Converter Functionality in a Three-Phase Indirect Matrix Converter

An indirect matrix converter (IMC) connected with two input power sources is proposed: a gasoline generator as the main ac power supply and batteries as the secondary power source. The IMC is small in size because of having a dc-link part without an electrolytic capacitor. The dc-link part is utilized by connection with a boost-up chopper with batteries as a secondary input power source. Furthermore, the chopper connects to the neutral point of the motor and utilizes the leakage inductance of the motor as a reactor component. The proposed technique successfully further reduce the size of the converter by removing the boost reactor in the boost converter stage. The proposed converter is simulated and experimentally validated using a 750-W prototype and an induction motor driven with V/f control. The total harmonic distortion of the input and output currents are 4% and 3.7%, respectively, and the efficiency is 96%.

Beatless Synchronous PWM Control for High-Frequency Single-Pulse Operation in a Matrix Converter

In this paper, a beatless control that enables unity input power factor for the single-pulse operation in the matrix converter is proposed. The proposed method controls the output voltage to synchronize with the output current in terms of voltage-time product during the high output frequency operation. Following the proposed synchronous control method, the beat current is suppressed by approximately 1% at output frequency 1432 Hz. The experimental results also demonstrate that the input current waveform achieves sinusoidal waveform with unity power factor. In addition, the voltage transfer ratio of the matrix converter is improved from 0.866 to 0.955 in the high output frequency region. The maximum efficiency 96.4% is achieved at a 1.34-kW RL load.

Improvement of output voltage with SVM in three-phase AC to DC isolated matrix converter

This paper discusses and evaluates the performance of a 50-kVA three-phase AC to DC matrix converter. Comparing to the conventional converter, which consists of a PWM rectifier and an inverter, the matrix converter does not require a large reactor at the three-phase input side, and require no DC smoothing capacitor at the DC link part. A space vector modulation based on the virtual AC-DC-AC conversion with four-step commutation patterns is proposed for the converter. From the experimental results, the converter can obtain 2.49% THD on the input current and achieves approximately 91.4% efficiency at 40kW.

A three-port interface converter by using an indirect matrix converter with the neutral point of the motor

This paper proposes a new three-phase power system that is applicable in various motor drive systems including HEV. The main circuit is based on an Indirect Matrix Converter (IMC) and the neutral point connection of a motor is utilized by connecting to an additional DC/DC converter. The DC link part of the IMC connects a boost-up type DC/DC converter and batteries to perform as a secondary power source to drive the motor. In addition, the proposed control method can utilize the leakage inductance of a motor as a boost-up reactor which will replace a common reactor in a boost-up chopper. The proposed converter has been simulated and validated experimentally using a 750W-prototype that driven by an induction motor with V/f control. The total harmonic distortion (THD) of the input current is 4%, the THD of the output current is 3.7% and the efficiency is 96%.

Voltage transfer ratio improvement of an Indirect Matrix Converter by Single pulse modulation

This paper proposes two over modulation strategies for the Indirect Matrix Converter (IMC). These strategies aim to improve the output-input voltage transfer ratio of the converter and also maintain high efficiency. This paper will discuss the control method of the two modulations and also compare the total losses of the converter. The control method uses a triangular carrier comparison method which is a simple structure based on the concept of a non-linear amplitude control of a voltage source inverter (VSI) output voltage. The validity of the proposed method will be demonstrated with the simulation results and the experimental results. Loss analyses are included in the paper to evaluate the efficiency of the two proposed methods. Furthermore, a 1 kW prototype was tested and efficiency of 93.5% is obtained.

Loss analysis and design method for high efficiency matrix converter

This paper discusses loss analysis formulas to achieve high efficiency and high power density for matrix converter. In this paper, the conduction loss and the switching loss of the matrix converter are derived theoretically based on virtual AC-DC-AC control method. Then, the validity of the equations is confirmed in simulation and experiment. From the experimental results, the maximum efficiency is 97.9% with 2-phase modulation at rated power (Devices: MOSFET R6046FNZ). In addition, it is confirmed that the total loss error between the calculation and experimental result is 8.65%. Finally, the relationship between the efficiency and power density is discussed by a pareto front curve. The power density is calculated from the volume of the switching device, heat-sink, input inductor and filter capacitor. As the result, the efficiency and maximum power density in the matrix converter are 97.0% and 9.7 kW/dm3 when the switching frequency is set to 85 kHz.

Suppression method of rising DC voltage for the halt sequence of an inverter in the motor regeneration

In the power conversion system of electric vehicles, the inverter is shut down when the system fails in the cause of a drastic load change or other protection reasons. However, in the case if the inverter is shut down in regeneration mode, the DC link capacitor voltage is increased dramatically, which will potentially break the switching devices. In this paper, the authors propose a halt method to overcome the over voltage and over current problems in the case of system failure during the regeneration. The proposed method consists of two phases, in the phase I, the DC link capacitor voltage is controlled by charge and discharge switching patterns based on space vector of the inverter. Then, the phase II performs the short circuit operation in order to avoid the regenerating current from the motor flows into the DC link capacitor. The experimental results demonstrate that the DC link capacitor voltage is 80% lesser comparing to the conventional method. Furthermore, the circulating current can be suppressed by 46% from the proposed method.

Verification of parallel connected multiple motor drive system with numbers of permanent magnet synchronous motors

This paper discusses a multi-parallel drive system for permanent magnet synchronous motors PMSMs). This system proposes to use two different functions of inverter, a main inverter with V/f control to control the speed of all parallel connected PMSMs. Then, each of PMSM is individually connected with an auxiliary inverter. The auxiliary windings which are used in the auxiliary inverter are placed in the slots together with the conventional windings. In addition, implementation of the damping control in the auxiliary inverter is discussed and the stability analysis is evaluated in order to suppress the speed and torque vibrations which are caused from the resonance between the inertia moment and the synchronous reactance. The simulation and experimental results demonstrate the effectiveness of the proposed system. Moreover, the relationship between the damping gain and the output power of the auxiliary inverter is clarified. From the results, it can be confirmed that if the application that is required a slow response is applied in the auxiliary inverter, then the power capacity of the auxiliary inverter can achieve the smallest which is equivalent to 10% of the main inverter power capacity.

Optimal design of a matrix converter with a LC active buffer for onboard vehicle battery charger in single phase grid structure

This paper discusses a design approach of an isolated type of single phase power converter that uses a matrix converter (MC) with a LC active buffer for the on-board vehicle battery charger in PHEV/EV. The MC is advantaged in terms of size due to the lack of DC bus, where the electrolytic capacitor is not required as direct conversion of AC/AC is possible. However, in the case of single phase, the 50/60 Hz grid power will cause power fluctuation in the battery current due to the lack of smoothing capacitor in the matrix converter stage. In order to compensate the power fluctuation, a LC buffer that utilizes the center-tapped of transformer in the inverter (INV) stage has been discussed. As a result, the circuit features small size because a low volume of capacitor is achieved. Furthermore, switching loss in MC stage is greatly reduced because the switching devices can achieve ZVS (zero voltage switching) behavior by using a synchronize control. In this paper, first the tradeoff relationship between the capacitor volume and efficiency which is subjected to the voltage conditions is discussed. Then, a design flow chart that considers between the capacitor volume, isolated transformer and device losses are discussed accordingly. Finally, based on the design flow chart, an ultraslim thickness of prototype (203mm × 113mm × 10mm) was constructed and the results show a conversion efficiency of 92% at a power density of 4.36W/cc.