**3.1 BESS DC/DC converter control**

Batteries are frequently integrated to PV systems thanks to their special energy characteristics. Indeed, batteries have a high energy density, which ensure long time of stable operation. The charging time and number of cycles depend on the adopted technology.

The battery power flow is bidirectional. In discharge mode, the power is supplied by battery, and in charging mode, the power is absorbed by battery. For both modes, the state of charge limits should be respected to not affect the battery lifetime.

*Vc* ¼ *Vi* � *L*1*IL*1*s* (1) *Ic* ¼ *IL*<sup>1</sup> � *IL*<sup>2</sup> (2)

*Ic* (3)

(4)

(5)

*Vc* <sup>¼</sup> <sup>1</sup> *Cf s*

*IL*<sup>1</sup> *Vi* � *Vc*

*Vc IL*<sup>1</sup> � *IL*<sup>2</sup>

(*Vi* � *Vc*) is given by the following equation:

*Control Analysis of Building-Integrated Photovoltaic System*

*DOI: http://dx.doi.org/10.5772/intechopen.91739*

the current (*IL*<sup>1</sup> � *IL*2) is expressed as follows:

**Figure 5.**

**59**

**Figure 4.**

*LCL filter single-phase modeling.*

*Control of the PV DC/DC converter.*

Based on Eq. (3), the transfer function between the current *IL*<sup>1</sup> and the voltage

According to Eqs. (2) and (3), the transfer function between the voltage *Vc* and

¼ 1 *L*1*s*

<sup>¼</sup> <sup>1</sup> *Cf s*

The BESS incorporates a DC/DC power converter that manages battery operation modes according to the appropriate control. A cascade control is adopted, the inner loop regulates the battery current, and the external one regulates the DC-link voltage.

The switches *C*<sup>1</sup> and *C*<sup>2</sup> (**Figure 3**) are controlled individually. In case of battery charging, *C*<sup>1</sup> is controlled and in case of battery discharging, *C*<sup>2</sup> is controlled.

#### **3.2 PV DC/DC converter control**

The structure of the two-stage power conversion is adopted for the PV system; this configuration is commonly privileged in the majority of the PV systems. The difference with the conventional structure is that the *Vdc* regulation is ensured by the BESS. As to the control of the DC/DC converter, it aims to ensure Maximum Power Point Tracking (MPPT) (which corresponds to the peak point of the power versus the voltage curve). In the case of this study, the Perturbation and Observation (P&O) algorithm is applied. The inputs of the P&O algorithm are the solar radiation *G* and the temperature *T* as shown in **Figure 4**.

#### **3.3 DC/AC converter control**

#### *3.3.1 Modeling of the DC/AC converter*

The output of the DC/AC and the LCL filter are modeled in single phase as shown in **Figure 5**. According to this figure, the obtained results are expressed as follows:

*Control Analysis of Building-Integrated Photovoltaic System DOI: http://dx.doi.org/10.5772/intechopen.91739*

$$V\_c = V\_i - L\_1 I\_{L1} \text{s} \tag{1}$$

$$I\_c = I\_{L1} - I\_{L2} \tag{2}$$

$$V\_c = \frac{1}{C\_f s} I\_c \tag{3}$$

Based on Eq. (3), the transfer function between the current *IL*<sup>1</sup> and the voltage (*Vi* � *Vc*) is given by the following equation:

$$\frac{I\_{L1}}{V\_i - V\_c} = \frac{1}{L\_1 \mathfrak{s}} \tag{4}$$

According to Eqs. (2) and (3), the transfer function between the voltage *Vc* and the current (*IL*<sup>1</sup> � *IL*2) is expressed as follows:

$$\frac{V\_c}{I\_{L1} - I\_{L2}} = \frac{1}{C\_f s} \tag{5}$$

**Figure 4.** *Control of the PV DC/DC converter.*

**Figure 5.** *LCL filter single-phase modeling.*

The BESS incorporates a DC/DC power converter that manages battery operation modes according to the appropriate control. A cascade control is adopted, the inner loop regulates the battery current, and the external one regulates the DC-link voltage. The switches *C*<sup>1</sup> and *C*<sup>2</sup> (**Figure 3**) are controlled individually. In case of battery

The structure of the two-stage power conversion is adopted for the PV system; this configuration is commonly privileged in the majority of the PV systems. The difference with the conventional structure is that the *Vdc* regulation is ensured by the BESS. As to the control of the DC/DC converter, it aims to ensure Maximum Power Point Tracking (MPPT) (which corresponds to the peak point of the power versus the voltage curve). In the case of this study, the Perturbation and Observation (P&O) algorithm is applied. The inputs of the P&O algorithm are the solar

The output of the DC/AC and the LCL filter are modeled in single phase as shown in **Figure 5**. According to this figure, the obtained results are expressed as

charging, *C*<sup>1</sup> is controlled and in case of battery discharging, *C*<sup>2</sup> is controlled.

radiation *G* and the temperature *T* as shown in **Figure 4**.

**3.2 PV DC/DC converter control**

*Numerical Modeling and Computer Simulation*

**3.3 DC/AC converter control**

follows:

**58**

**Figure 3.**

*Control strategy of BESS.*

*3.3.1 Modeling of the DC/AC converter*

The transfer functions given by Eqs. (4) and (5) allow the deduction of the system block diagram given by **Figure 6**.
