BASIC COMPARISON AND EVALUATION OF FUNCTIONALITY AC-AC MATRIX CONVERTER CONCEPTS FOR HEV VEHICLE-PART I

The paper deals with the direct AC-AC propulsion system and compares two matrix converter concepts with fivephase traction induction motors (IM) for the hybrid electric vehicle (HEV) including electronic differential. The first one consists of [3x5] matrix converter and [3x1] active PWM rectifier (4Q-converter) for full power performance. The second one comprises one [3x5] matrix converter for full power and auxiliary [0x5] matrix converter for partial output power. Configurations of [3x5] + [0x5] MxC converters with five-phase motor(s) are not analyzed in available literature so far. The advantage of the proposed connection is in supposed higher efficiency of matrix converter then clasiccal VSI one. Part I deals with a theoretical study of converter concepts for hybrid electric vehicle. Based on simulation results the comparison and evaluation of the property and quality of the quantities of different type of the matrix powertrain are discussed in Part II.


Introduction
The mostly series HEV powertrains use front-end converter system with a DC-voltage interlink [1][2][3][4][5]. Since in-vehicle driving tests for evaluating performance and diagnostic functionalities of engine management systems are often time-consuming, expensive and not reproducible, simulation methods with HIL (hardware in the loop) or SIL (software in the loop) simulators allow to validate new hardware and software automotive solutions.
One of the important questions is the number of phases of the generator and/or traction motor, respectively. If the number of phases of the generator are smaller than three, so the power fluctuation in fictitious DC interlink is rather high [6][7]. Similarly, on the opposite, if the number of phases of the motor is just three (no more) then there is not possible to connect both traction motor to on one common direct traction converter [8][9][10][11][12][13], Figure 1.
Advantages and operation of a five-phase induction motor are described in [14], its operation under loss of one phase of a feeding source in [15].
Such a configuration of the AC/AC powertrain makes it possible both pure electric operating modes and/or pure engine mode, as well as hybrid mode: the vehicle is propelled by ICE engine and accu-battery energy in parallel operation [1].
Note, to provide of full autonomous HEV operation from accu-battery AB (i.e. traction one), the sizing of 4QC converter should be done for nominal traction power of two traction motors TM.
mode is using during the accelerating and ICE start-up/AB charging regime only. Structural schemes of AC/AC matrix converters (3x5 MxC, 0x5 MxC) are classical circuitry with three-phase input and five-phase output (3x5 MxC) or DC input and five-phase output (0x5 MxC), respectively. The structural schemes of MxC converter with indirect control [9,[16][17][18][19] used for simulation are shown in Figure 5.
Since the 4QC converter is omitted, the novel scheme of HEV powertrain, Figure 2 makes it possible the parallel operation of ICE and AB using 0x5 MxC converters. It gives a sophisticated solution making possible as parallel as the autonomous operation of ICE and AB.
Since it deals with parallel operation, such an HEV is series and parallel vehicle. The sizing of paralleling converter (4QC or 0x5 MxC) is then done just for the different power of traction motors and ICE, Figure 4. Practically, the parallel

Figure 5 Structural schemes of MxC converter with indirect control (FDC -is fictitious DC interlink with a) three-phase rectified voltage or with b) DC voltage) without filter and protection circuitry
Using this approach a space vector PWM can be used for IM control.

Clamping protection and filtering circuits
Compulsory parts of the matrix converter mentioned rarely are protection and filtering circuits [5,20]. Schematics of MxC propulsion drive with floating clamping protection and input filter is shown in Figure 6.

Designing input LC filter and clamping protection unit
The input filter is very important for MxC especially in the case of the non-harmonic input currents of MxC will be loaded with the synchronous generator by additional distortion power. Design of LC filter should be considered basically from the next points of view [20][21]: Filter operation at a basic mains frequency of the range 100 -200 Hz (output frequency of the synchronous generator) Filter combination behavior in the frequency domain (filter transfer function) The resonant frequency should be in a range between ten times the line frequency and one-half of the switching frequency, to avoid resonance problems in the lower and upper parts of the harmonic spectrum Passive damping must be sufficient to avoid oscillation, but losses cannot be so high as to reduce efficiency [5] Regarding the clamping unit: In generally, energy accumulated in coils is given by their inductances and the appropriate currents flowing through them.
The design procedure for both LC filter ( Figure 7) and clamping protection unit has been used by [20].
Modeling indirect control we get: where are modulating matrices with their elements where toi for output indexes , , , The total value of inductance should be less than 0.1 p.u. to limit the ac voltage drop during operation. Otherwise, a higher dc-link voltage will be required to guarantee current controllability, which will result in higher switching losses.
To design the LCL input filter the design procedure using [23] can be used.
Designing input LCL filter is needed for 4QC autonomous operation as charging of accu-battery by ICE/ SG unit or at starting-up the ICE/SG using accu-battery. To design the filter, some limits on the parameter values should be introduced [22][23] The capacitor value is limited by the decrease of the power factor at rated power (generally less than 5%). The power factor decrease can also be a function of the ac sensor position as discussed in [22].

Conclusion
Basically, using of [3x5] matrix converter drive with 5-phase motors brings: • higher efficiency against VSI front-end converter system • the possibility of independent control of 5-phase motors which is not possible with 3-phase motors.
Algorithm for ICE engine -generator assembly control consisting basically of three steps: • start-up of ICE engine to reach the idle speed, then • start-up of traction motor to demanded speed and continuously • setting-up of the ICE engine to adequate speed and power.
Hybrid operational mode of HEV powering. Parallel operation of ICE engine and traction accu-battery AB is possible using the novel scheme of HEV powertrain, Figure 4 makes it using 0x5 MxC converters. It gives