AN4070 datasheet(6/53 Pages) STMICROELECTRONICS

6 / 53 page

System description

AN4070

6/53

Doc ID 022934 Rev 1

The system is powered up by an auxiliary power supply which generates a +15 V and a +5

V bus from the input voltage using an L4951 integrated circuit and few external components.

The startup voltage of the auxiliary power supply is 18 V while the maximum voltage is 55 V.

The STM32F103xx supply voltage is scaled down from the +5 V bus using a low drop linear

regulator. Five feedback signals are used by the microcontroller in order to fully control the

system. In particular, a voltage transformer and a Hall effect sensor are used to sense grid

voltage and current, respectively. Two resistive voltage dividers are used to sense the DC-

DC converter input and output voltage. Since the microcontroller is supplied from the input

side of the system, the high voltage bus feedback signal is opto-isolated to ensure galvanic

isolation between the input and the output of the system. Finally, the input current generated

by the PV module is sensed using a simple current shunt resistor. These five feedback

signals are sampled at 17.4 kHz using the STM32F103xx 12-bit A-D converters.

The control strategy is based on a standard perturb and observe (P&O) MPPT algorithm to

adapt the input system impedance to the PV module electrical characteristics, while it uses

DQ axes control to ensure that MIC generated current and voltage are able to cope with grid

characteristics. The main system specifications are summarized in Table 1.

Table 1.

Summary of main electrical specifications

Parameter

Value

Vin (nominal input voltage)

35.8 V

Vin_max (maximum input voltage)

55 V

Vin_min (minimum input voltage)

18 V

MPPT range

20 V to 40 V

Iin (nominal input current)

7.6 A

Imax (max. input current)

11 A

DC-DC output voltage nominal

380 V

DC-DC max. output voltage

450 V

Vout AC

230 V, 50 Hz - 240 V, 60 Hz

Iout (nominal)

1.1 A (230 V AC) / 1.06A (240 V AC)

Power factor

0.98 @ full load

Nominal output power

250 W

DC-DC switching frequency

35 kHz

DC-AC switching frequency

17.4 kHz

AN4070 Datasheet(PDF) 6 Page - STMicroelectronics

AN4070 Datasheet(HTML) 6 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53

Datasheet Download

Link URL