# An EV SRM Drive and Its Interconnected Operations Integrated into Grid, Microgrid, and Vehicle
## 3 EV SRM Drive
### Battery-Powered Varied DC-link Voltage SRM Drive  
#### 3.2.1 Battery Interface DC/DC Converter  
Figure 11a,b show the schematic and control scheme of the established interleaved boost/buck converter with two cells. The switching signals between the two cells are phase-shifted by 180\({}^{\circ}\). The interface DC/DC converter can be operated in the following modes:  
(a) Discharging mode. In the motor driving operation, the DC-link voltage \(v_{dc}\) is established from the battery voltage \(v_{b}\) in boost mode.  
Figure 11: Interleaved boost/buck converter: (a) power circuit; (b) control scheme.  
2. Charging mode. In the battery charging mode or regenerative braking mode, the power flow is from \(v_{dc}\) to \(v_{b}\). The bidirectional boost/buck converter is operated as a buck DC/DC converter. The power circuit and control scheme of the interface converter are specifically designed in boost mode. The designed components are also employed under buck mode, with the adequacy being verified. 1. Power circuit The ratings and the designed system parameters are as follows: 1. Ratings: \(V_{dc,\max}=550\) V, \(P_{dc}=2.2\) kW. 2. Battery bank: nominal voltage \(V_{b}=158.4\) V. 3 PWM switching frequency: \(f_{s}=20\) kHz. 4 DC-link capacitor: \(C_{dc}=1100\)\(\mu\)F/900 V. 5 Battery side capacitor: \(C_{b}=4700\)\(\mu\)F/400 V. 6 Energy storage inductors: \(L_{b1}=\)1.837 mH and \(L_{b2}=1.833\) mH at 20 kHz. 2. Control scheme. The control scheme shown in Figure 11b consists of an outer voltage loop and an inner current loop. The current command of each cell (\(i^{*}_{Lb1}\) and \(i^{*}_{Lb2}\)) is generated by the voltage controller \(G_{cv}(s)\). And the PWM control signal of the two cells (\(v_{cont1}\) and \(v_{cont2}\)) is yielded by the current controller \(G_{ci}(s)\). The two PWM control signals are compared with two sawtooth waves (\(v_{saw1}\) and \(v_{saw2}\)) phase-shifted by 180\({}^{\circ}\) to generate the switching signals. 1. Current controller 2. Feedback controller The compensated control characteristics of the current closed-loop gain are defined as having the crossover frequency at 1 kHz with a phase margin of 89.3\({}^{\circ}\). The designed controller is: \[G_{ci}(s)=K_{pi}+\frac{K_{ni}}{s}=0.7+\frac{50}{s}\] (13) 2. Feedforward controller The feedforward controller \(G_{ff}(s)\) added to yield-improved current tracking response is set as: \[G_{ff}(s)=1-\frac{v^{\prime}_{b}}{v^{*}_{dc}}\] (14) Through the feedforward controller, the duty ratio can be directly set to yield the desired \(v_{dc}\) from the sensed \(v^{\prime}_{b}\). 2. Voltage controller The compensated control characteristics of the voltage closed-loop gain are defined as having the crossover frequency at 20 Hz with the phase margin PM \(=90^{\circ}\). The designed voltage feedback controller is: \[G_{cv}(s)=K_{pv}+\frac{K_{iv}}{s}=10.0641+\frac{95.0929}{s}\] (15)  
Moreover, a robust controller with the weighting function \(W_{v}(s)\) is added. To enhance the dynamic response, the weighting function is set as:  
\[W_{v}(s)=0.6 \tag{16}\]