## 5 Experimentation
### Results and Discussions  
#### 5.2.1 Dynamic Response under Different Conditions  
\(\bullet\) Start-up process  
A serious over-voltage phenomenon can also exist during the starting process. Appropriate adjustments of the boost converter can be made to meet critical acceleration requirements under rated conditions. Figure 11 shows bus-voltage (red line) and phase A-current (blue line) waveforms of the normal mode and the manual boost mode (\(K_{1}=1\)) in the starting and stable running processes under rated conditions. Here, the duty cycle of the inverter was set to 50% and the scaling of the signals is 50 V and 50 A, respectively. It was found that the impact currents of the two modes during the start-up process existed but were acceptable due to dual closed-loop control. The bus-voltage of the steady state stabilized around 270 V under the normal state and 300 V under manual boost mode. A reasonable bus pump-up-voltage of about 22 V existed during each transient process, which was due to the abundant filter capacitance and appropriate absorbing capacitance. The start-up period of the manual boost state lasted 2.95 s, which was 36.4% faster than the 4.64 s of the normal state. Therefore, the proposed topology had the ability to improve the start-up performance under \(K_{1}=1\) control conditions. The fluctuations and spike signals of the waveforms existed because of the PWM mode voltage source. \(\bullet\) Speed adjustment process  
Figure 12 shows the actual speed (Feedback) curve tracking the expected speed (Given) from 0 to 12,500 rpm. The given speed waveform was set up in a stepped pattern, and feedback data points were collected every 0.5 s. It was found that the actual speed tracked the given speed very well, verifying the validity of the dual closed-loop control strategy. The accelerating process contained two stages: the normal stage, from 2500 to 7500 rpm without boost converter during \(\Delta t_{1}\), and the manual boost stage with converter from 7500 to 12,500 rpm during \(\Delta t_{2}\). Considering the time consumption by series  
Figure 11: Bus-voltage and phase-current waveforms in transient process. (**a**) Normal mode; (**b**) manual boost mode (\(K_{1}=1\)). communication, closed-loop interrupt routine, and other programs, \(\Delta t_{1}\) needed about 3.9 s. It is noted that \(\Delta t_{2}\) lasted about 1.8 s, which was much shorter than \(\Delta t_{1}\), indicating that the \(K_{1}=1\) control state could shorten the speed tracking response time during steady state. \(\bullet\) Abrupt load torque change process  
The machine's acceleration characteristic with load represents the load-disturbance resisting performance and affects the execution speed of the system. Figure 13 shows part of the machine's phase-current waveforms for the normal state and adjustment state (\(K_{2}=1\)) during the abrupt load torque change procedure from load No. 1 (1 N.m) to load No. 2 (3 N.m) under rated-voltage power supply. Here, the duty cycle of the inverter was set to 50%. It can be observed that the aptitude of the phase-current rose with load increase, while machine speed slowed down. The process of normal state under this large load variation situation lasted 2.1 s while the adjustment state lasted 1.4 s. The waveforms of these procedures were similar to the waveform of the start-up process. The phase peak current was about 25 A during the load torque change period. It took 32.15 ms for the phase peak current to rise from 25 to 50 A, as shown in Figure 13a. During actual operation, the boost circuit started to work under this impact load situation and \(K_{2}\) was set to \"1.\" This resulted in the period of the adjustment process being shortened. It took 22.92 ms for the phase peak current to rise from 25 to 50 A, as shown in Figure 13b, reflecting a relatively fast adjustment characteristic under the \(K_{2}=1\) state.