Statement on the SMT String Configuration Requirements

Author: Simon

2023-10-07 14:46

1.  Overview

This document is the configuration recommendation of GoodWe SMT series: GW30/36K-MT and GW50/60KS-MT, which are mainly used in residential or C&l projects.

In order to ensure high conversion efficiency and service life of the inverter, the strings need to be configured according to the design principles required in this document.

 

2.  PV module Configuration

2.1 PV Module Series Design Principles

For SMT series models, the following string design requirements are proposed, while fulfilling four conditions:

(1) The maximum Voc of the string is lower than the maximum input voltage of the inverter (≤1100V).

(2) The MPPT voltage of PV modules connected in the series is within the inverter full load MPPT voltage range (510V~860V).

(3) The voltage difference between different MPPTs is less than 120V.

(4) When the inverter is connected to multiple strings, the strings should be dispersed into each MPPT as far as possible.

2.2 PV module Basic Parameters

Currently, the mainstream specifications of the modules are 540W~560W, etc. The technical parameters of each module are shown in Table 1:

Table 1: Common Module Parameters

2.3 Design of modules in series

2.3.1 Modules series number calculation

Assuming that the ambient temperature is -25℃~40℃, the module is selected as 182mm series 550W, the calculation result is shown as below:

Table 2: 550W Module String Design

2.4 Introduction of MPPT Terminal Access Methods

(1) 3 MPPT (SMT 30/36K)

A. The 1-1-1 access method. (Total 3 strings: 3 strings are connected to 3 MPPTs).

For example, the number of PV panels in a 3-way string is 18 (connected to MPPT1); 18 (connected to MPPT2); and 18 (connected to MPPT3).

Fig. 1: 1-1-1 Access Methods

B. The 2-1-1 access method. (Total 4 strings: 2 strings with high string voltage are connected to the same MPPT, and the two strings with low voltage are connected to one of the other 2 MPPTs).

      For example, the number of PV panels in a 4-way string is 17, 17 (connected to MPPT1); 18 (connected to MPPT2); 16 (connected to MPPT3).

Fig. 2: 2-1-1 Access Methods

C. The 2-2-1 access method. (Total 5 strings: the lowest voltage string is connected to one of the last MPPTs).

For example, the number of PV panels in a 5-way string is 18, 18 (connected to MPPT1); 17, 17 (connected to MPPT2); and 16 (connected to MPPT3).

Fig. 3: 2-2-1 Access Methods

(2) 5 MPPT (SMT 50K)

A. The 1-1-1-1-1 access method. (Total 5 strings: 5 strings are connected to 5 MPPTs).

  For example: the number of PV panels for a 5-way string is 18 (connected to MPPT1); 18 (connected to MPPT2); 18 (connected to MPPT3); 18 (connected to MPPT4); 18 (connected to MPPT5).

Fig. 4: 1-1-1-1-1-1 Access Methods

B. The 2-1-1-1-1 access method. (Total 6 strings: the 2 highest voltage strings are connected to the first MPPT, and the other 4 strings are connected to other 4 MPPTs).

      For example: the number of PV panels for a 6-way string is 18, 18 (connected to MPPT1), 18 (connected to MPPT2), 18 (connected to MPPT3), 18 (connected to MPPT4), and 18 (connected to MPPT5).

 

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