**6.2 Switch-Mode Rectifier based EV battery charger**

#### **6.2.1 System configuration**

A battery powered SRM drive for electric vehicle propulsion is shown in Fig. 23(a) (H.C. Chang & Liaw, 2009). In driving mode, the switches are set as: *Sm* → M and *Sd* → closed. The SRM (DENSEI company Japan) is rated as 4-phase, 8-6, 48V, 6000rpm, 2.3kW. The components , , *SDL b bb* and *Cd* in Fig. 23(a) form a DC/DC boost converter. The nominal battery voltage is *Vb* = ×= 12 4 48V , it is boosted and establishes the DC-link voltage with 48V 72V. ≤ ≤ *Vda* During demagnetization of each communication stroke, the winding energies can be directly sent back to the battery bank via the diodes 135 *DDD* , , and *D*<sup>7</sup> .

In charging mode, the switches in Fig. 23(a) are set as: *Sm* → C and *Sd* permanently off. With the insertion of off-board part, a buck-boost SMR based charger is formed and drawn in Fig. 23(b) with the employed embedded motor drive components being highlighted. The diode *De* is added to avoid the short circuit of battery when *Q*6 is turned on. The inductances of the first two motor windings are used as the input filter components during each half AC cycle. And the third motor winding inductance is employed as the energy storage component of the SMR.

The SMR control scheme shown in Fig. 23(b) consists of outer charging control scheme and inner current controlled PWM scheme. Initially, the battery is charged in constant current

Some Basic Issues and Applications of

SMR charger can be seen from the results.

power quality becomes worse.

= 0.85 (PI and robust feedback controls) *Wib*

**6.2.2 Performance evaluation** 

command \*

\* *Li*

*Li f kHz <sup>s</sup>* =12.5

Switch-Mode Rectifiers on Motor Drives and Electric Vehicle Chargers 283

The derivation of circuit component ratings and the implementation affairs of the SRM drive shown in Fig. 23(a) and Fig. 23(b) can be referred to (H.C. Chang & Liaw, 2009). Some results concerning charging mode are observed here. Under the constant current charging mode with *I I Lm c* = = 21.3A and switching frequency 12.5 *sf kHz* = , the measured *Li* and its

( *v I b b* = = 47.65V , 9.45A ). The close inductor current tracking control is observed from the results. Fig. 24(b) shows the corresponding AC source voltage *ac v* and current *ac i* (PF = 0.989, *THDi* = 4.23 %). Good line drawn waveform and power quality by the buck-boost

To observe the effects of switching frequency on the SMR control performance, Table 9 lists measured performance parameters corresponding to the switching frequencies of 12.5 , *sf kHz* = 15*kHz* , 7.5*kHz* and 2.5*kHz* ( 0.85 *Wib* = ). Some facts are observed from the results: (i) The current loop is normally operated at each switching frequency; and (ii) As the switching frequency becomes smaller, the inductor current will gradually become partial and then total discontinuous current mode (DCM) within the AC cycle. Accordingly, the

*Wib* = 0.85

10A

Fig. 24. Measured results of the buck-boost SMR based charger in constant-current charging

Variables 2 *.*5*kHz* <sup>7</sup>*.*5*kHz* <sup>12</sup>*.*5*kHz* <sup>15</sup>*kHz*

*Pac* (W) 579.7 563.4 547.8 560.6 *I ac* (A) 5.56 5.15 5.11 5.14 *Pb* (W) 388.4 427.3 453.3 459.4 *Vb* (V) 46.32 47.12 47.65 47.73 *I b* (A) 8.22 9.02 9.45 9.45

(%) 67.00 75.84 82.75 81.95 *PF* 0.972 0.981 0.989 0.991 (%) *iac THD* 10.02 7.84 4.23 4.04 Table 9. Measured power quality parameters of the buck-boost SMR based charger under

10A

100V

5ms (b)

*ac i*

*Li* by PI and robust controls

*ac v*

1ms (a)

( 0.85 *Wib* = , 12.5 *sf* = *kHz* ); (b) *ac v* and *ac i* (PF=0.989, *THDi* =4.23%)

mode at ( *v I b b* = = 47.65V , 9.45A ): (a) *Li* and \*

*sf*

η

different switching frequencies

*Li* by PI control and robust control ( *Wib* = 0.85) are shown in Fig. 24(a)

mode to let the batteries be charged under maximum current (0.25C/9.5A) until the condition of 52V ( 13V 4) *Vb* ≥ =× reaches. Then the charging enters constant voltage floating mode.

Fig. 23. A battery powered SRM drive with voltage boosting for electric vehicle propulsion: (a) system configuration; (b) schematic and control scheme of the formed on-board buckboost SMR based battery charger in idle status

#### **6.2.2 Performance evaluation**

282 Electrical Generation and Distribution Systems and Power Quality Disturbances

mode to let the batteries be charged under maximum current (0.25C/9.5A) until the condition of 52V ( 13V 4) *Vb* ≥ =× reaches. Then the charging enters constant voltage

> *ac v Cf*

*A*′

( ) 3 *i i L*

*i D*

> ( ) 6 *D*

> > (*D*) *De*

( ) 3 *i i L*

Σ

*i* ε

*b v*′

*Li*′

*W* (*s*) *ib*

*b i <sup>D</sup> i*

> A/D A/D *bv*

*Kic Kvc*

*Q*<sup>2</sup> *Q*<sup>4</sup>

Utility source

Off-board

*B*(*E*)

*Cb bv*

*Pcb*

control scheme

Current controller

*G* (*s*) *ib*

DSP TMS320F240

( ) *Q*6 *v pwm*

PWM

*ac i*

(a)

Buck/boost PFC charger

(ON) *Q*<sup>5</sup>

( ) 3 *L L*

*E*(*B*) *A*

*B*′

*D*5

*i*

*RL*

Test load

C

*C*

PMSG

*A*′

Test *<sup>Q</sup>*<sup>1</sup> *<sup>Q</sup>*<sup>3</sup> *<sup>Q</sup>*<sup>5</sup>

SRM and converter

floating mode.

−

On-boar

*ac v* +

> ∗ *<sup>b</sup> <sup>v</sup>* <sup>Σ</sup>

> > *b v*′

*<sup>v</sup> <sup>V</sup> <sup>b</sup> vb* ′ ′ <sup>≤</sup> <sup>52</sup>

boost SMR based battery charger in idle status

− *<sup>f</sup> <sup>C</sup>*

*i*

*Pac*

Battery bank

<sup>+</sup> *Cd*

M *Sm* C

*L*1

Voltage controller

<sup>Y</sup> *Ic* <sup>=</sup> 22.71*<sup>A</sup>*

*D*2

*<sup>I</sup>* <sup>=</sup> *<sup>G</sup>* (*s*) *cv*

N

Battery charging XINT

*D*<sup>1</sup> *D*<sup>3</sup>

*<sup>D</sup> ac*

Embedded components of SRM and converter

*L*2

*D*4

*Lm c I*

( ) 6 *S Q*

*ac v*

Reference signal generator

(b)

Fig. 23. A battery powered SRM drive with voltage boosting for electric vehicle propulsion: (a) system configuration; (b) schematic and control scheme of the formed on-board buck-

∗ *Li* Σ ∗ *L*1 *i*

∗ *Lc i*

*s*(*t*)

control scheme SMR current

<sup>y</sup>SRM and

*bS <sup>b</sup> v*

The derivation of circuit component ratings and the implementation affairs of the SRM drive shown in Fig. 23(a) and Fig. 23(b) can be referred to (H.C. Chang & Liaw, 2009). Some results concerning charging mode are observed here. Under the constant current charging mode with *I I Lm c* = = 21.3A and switching frequency 12.5 *sf kHz* = , the measured *Li* and its command \* *Li* by PI control and robust control ( *Wib* = 0.85) are shown in Fig. 24(a) ( *v I b b* = = 47.65V , 9.45A ). The close inductor current tracking control is observed from the results. Fig. 24(b) shows the corresponding AC source voltage *ac v* and current *ac i* (PF = 0.989, *THDi* = 4.23 %). Good line drawn waveform and power quality by the buck-boost SMR charger can be seen from the results.

To observe the effects of switching frequency on the SMR control performance, Table 9 lists measured performance parameters corresponding to the switching frequencies of 12.5 , *sf kHz* = 15*kHz* , 7.5*kHz* and 2.5*kHz* ( 0.85 *Wib* = ). Some facts are observed from the results: (i) The current loop is normally operated at each switching frequency; and (ii) As the switching frequency becomes smaller, the inductor current will gradually become partial and then total discontinuous current mode (DCM) within the AC cycle. Accordingly, the power quality becomes worse.

Fig. 24. Measured results of the buck-boost SMR based charger in constant-current charging mode at ( *v I b b* = = 47.65V , 9.45A ): (a) *Li* and \* *Li* by PI and robust controls ( 0.85 *Wib* = , 12.5 *sf* = *kHz* ); (b) *ac v* and *ac i* (PF=0.989, *THDi* =4.23%)


Table 9. Measured power quality parameters of the buck-boost SMR based charger under different switching frequencies

Some Basic Issues and Applications of

(a)

*PF* = 0.9981 *THDi* =5.220%

two charging current levels

**7. Conclusions** 

*ac v*

*ac i*

5ms

under steady-state charging current of *Ib* = 6A : (a) ( *ac v* , *ac i* ); (b) ( *<sup>b</sup> v* , *bi* )

η

constituted components are designed and implemented.

followed power stage, parallel opeartion to enlarge SMR ratings, etc.

Switch-Mode Rectifiers on Motor Drives and Electric Vehicle Chargers 285

50V

*b v*

1V

10A

5ms (b)

*b i*

5A 50V

Fig. 26. Measured results of the developed flyback SMR based auxiliary plug-in charger

*<sup>b</sup> I* 5A 6A *Pb* 265.28W 306.56W *Pac* 364.17W 415.98W

 72.85% 73.70% *PF* 0.9986 0.9981 *THDi* 3.742% 5.220%

Table 10. Measured results of the developed flyback SMR based auxiliary plug-in charger at

This article has presented the basic issues of switch-mode rectifiers for achieving batter performance. The schematic type and control scheme should be properly chosen according to the specific application and the desired operation characteristics. The considering issues include input-output relative voltage levels, operation quadrant, galvanic isoltation, phase number, DCM or CCM operation, voltage mode or current mode control, dynamic control requirement, etc. In power circuit establishment, the ratings of circuit components and the ripples of energy storage components should be analytically derived, and accordingly, the

As to the control affairs, the sensed inductor current and output voltage should be filtered with suited low-pass cut-off frequencies. Then the basic feedack controllers are designed considring the desired perfromance and the effects of comtaiminated system noises. If more stringent control requirements are desired. The simple advanced control, such as the robust tracking error cancellation controls (Chai & Liaw, 2007; Y.C. Chang & Liaw, 2009a), can further be applied. Other possible affairs lie in the digital control with properly chosen sampling intervals, random switching, the considrations of DC-link ripple effects on the

In this article, the applications of various SMRs to PMSM drive, SRM drive, electric vehicle plug-in battery charger and microgrid plug-in battery charger were presented. The
