AN3095 datasheet(6/55 Pages) STMICROELECTRONICS

6 / 55 page

System description

AN3095

6/55

Doc ID 16555 Rev 3

System description

A general description of the system is shown in Figure 2 with a block scheme representing

hardware implementation.

Figure 2.

Block scheme of hardware implementation

It consists of 5 boards as listed below:

●

Main power board

●

Multi-output power supply board

●

Control and signal conditioning board

●

Output sensing and relay board

●

Input current sensing board.

The system may be completed by adding two additional boards with input and output EMI

filters which, at the moment, are not included in the final prototype.

The main power board is a dual-stage converter using DC-DC to adapt voltage levels and

impedance from the PV array and a sinusoidal PWM DC-AC to perform grid connection at

230 Vrms and 50 Hz, [see References 3]. Gate driving circuitry, input and output voltage

sensors of the DC-DC converter, as well as high frequency (HF) transformers, are also

placed on the power board. The principle reason for using a HF transformer is the galvanic

isolation provided between the PV module and the grid, to minimize the risk of hazardous

operations on the PV side caused by a fault on the grid side; voltage step-up and also

interruption of the resonance path formed by the parasitic capacitances to ground of the PV

array and the inductance of the LCL filter. Another advantage is the elimination of high

common mode currents allowing the use of unipolar pulse-width modulation for the inverter

with a consequent reduction in current harmonic content compared to bipolar pulse-width

modulation, [see References 4, 5].

Both the multi-output power supply board and control board are connected to the main

power board by means of a 34-pin connector. In this way, the connection/disconnection of

the ancillary boards is very easy and allows the separation of debug and characterization.

AN3095 Datasheet(PDF) 6 Page - STMicroelectronics