## 4 Results
### Off-Grid Operation--Dynamic Parameters during Load Power Changes  
Tests in transient states during load power change--switching on and off the load--were carried out. The following values were measured: load phase current (to determine the moment of load power change), load phase voltage, battery voltage and current, and DC bus voltage. The tests were carried out in two variants: (1) without changing the generator operating point and; (2) with changing the rotational speed of the generator in order to adjust the generated power to the load power and reduce the battery current.  
3.1 Parameter Measurements in the DC Circuit, Operation without Power Control of the Induction Generator  
During operation without power control of the induction generator, any change in load power is balanced by the battery. The battery charging current was limited to 40 A and the discharge current to 150 A.  
Switching on the 9.5 kW Load  
The battery current was initially set at 40 A, charging with a power of approx. 2 kW. The generator works with a constant power of approx. 4 kW. The surplus power from the generator is redirected to the resistor using the PC3.2 converter. The battery current, load current, DC bus voltage, and battery voltage waveforms are shown in Figure 25.  
After switching on the receiver, the battery current changed the direction of flow (discharge) and stabilized at a value of approx. 120 A, after rebuilding the voltage in the DC circuit (710 V). The time taken to restore the DC voltage was approx. 600 ms.  
Switching off the 9.5 kW Load  
The battery current is initially set to 0 A. The generator power is also 0. Waveforms of the battery current, load current, DC bus voltage, and battery voltage are shown in Figure 26.  
Figure 25: Turning on a 9.5 kW load in off-grid mode, with constant generator power: (**a**) current and voltage waveforms; (**b**) enlarged fragment of waveforms from Figure 25a during load switching. (**a**)—load phase current; (**b**)—battery current; (**c**)—DC bus voltage; (**d**)—battery voltage. Source: author’s development.  
After the receiver, the battery current increased to approximately 40 A (maximum charging value). Then, the PC3.2 converter turned on, redirecting the surplus power to the resistor and stabilizing the DC link voltage to a value of approx. 730 V.  
3.2 Measurements of Parameters in the DC Circuit, Operation with Power Control of the Induction Generator  
The power control of the induction generator was carried out by controlling its rotational speed. In this mode, the drive motor operates with a constant torque. The speed control system is designed to control the battery current. After the load power, the set value of the rotational speed changes, which corresponds to a battery current of 0 A. The rotational speed is represented in the figures below by the waveform of the generator current, on which the frequency change is visible.  
Waveforms of the voltages and currents during the switching on and off of a 5.5 kW load are shown in Figure 27. Before starting the test, the generator speed controller set the rotational speed for which the battery current was approx. 0 A. Then, after changing the load power, the controller set the rotational speed for which the battery current was approx. 0 A again. The tests made it possible to set the parameters of the regulator in such a way that the time of re-establishing the set value of the battery current was approx. 2 s.