*4.3. Daily Power Profile of PV*

The ramping capability of the proposed PV-BES system can be utilized to shape the daily load profile. When the distributed PV generators are equipped with the proposed BES system, and properly commanded, the aggregated load profile can become much smoother with some desired ramp rates. This also enables peak-load reduction. To demonstrate these properties, two scenarios are studied in this section as follows.

**Scenario I**: Figure 19 shows the power profile of California ISO on 31 March 2019 [33] with the proposed PV-BES system. The BES charges and stores energy in the morning as the solar intensity increases and avoids sharp decline of net load. This stored energy is released in the evening when the PV generation declines and the load demand increases. Figure 19 shows the profile when both RUR and RDR of the PV-BES system are set at 1200 MW/h. With a total of 5000 MW, 19411 MWh BES systems, the ramp rate is reduced from 5300 MW/h to 2767 MW/h (almost 50%) and the peak load is reduced from 22580 MW to 18747 MW.

**Scenario II**: In Figure 20, the RUR is set at 1400 MW/h while the RDR is set at 1000 MW/h till 20:00 and changed to 3000 MW/h afterwards. The required BES is 5571 MW, 15201 MWh and the ramp rate of the net load is reduced to 2660 MW/h with peak load of 21535 MW.

The results are summarized in Table 5. This study concludes that by properly adjusting the RUR and RDR, both the steep ramp-up rate and the peak of the net load profile may be mitigated. The RUR and RDR may be optimally computed and supplied by a secondary controller through a low-bandwidth communication.


**Table 5.** Impact of ramp rate settings on daily power profile.

**Figure 20.** Shaping of Daily Load Profile: Scenario II.

#### *4.4. Experimental Results*

This section presents the results of a laboratory-scale implementation of the proposed system to evaluate its performance in a basic condition where all algorithms and controls are implemented in real time. The ability of the proposed approach to counter the PV disturbances (generated using an actual PV emulator hardware and other periphery circuits) is demonstrated. The results confirm feasibility of the proposed algorithms and controls. The details are presented throughout the section.

## 4.4.1. Experimental Setup

Figure 21 shows a low-power laboratory-scale experimental setup built to evaluate the performance of the proposed controller in response to the abrupt PV disturbances. An Agilent E4360A modular solar array simulator is used to emulate the PV and its disturbances. It is connected to a dc grid via a standard buck converter. A dc power supply in parallel with a local load models the dc grid. Another dc supply with a local load acts as a battery, and it is connected to the dc grid via a half-bridge converter for bi-directional power flow. The proposed control method is used and realized on the micro-controller to control the two converters.

Table 6 shows the system and control parameters. The control parameters for the PV system are designed to regulate the PV voltage to 20 V (maximum power point) using the method discussed in Section 4.1.1. For the BES system, the reference power calculation and the design of the power control parameters are done using the method in Section 3.3. We have ignored the SOC control and the ac system due to limitations in experimental setup.

**Figure 21.** Experimental setup.

**Table 6.** Experimental setup parameters.

