Application of DJSF1352 DC Energy Meter in a Photovoltaic Energy Storage System in Singapore

AC is more convenient and economical than DC when transmitting high voltage. However, in some application scenarios, the application of DC directly supplying DC loads can make circuit design simpler and more efficient. At present, DC power distribution can directly supply DC power through photovoltaics or batteries in photovoltaic + energy storage systems, and is also widely used in new energy power systems, such as solar street lights, DC air conditioners, 5G communication base stations, etc.

1. Project Overview

Singapore relies heavily on natural gas for power generation, but its own natural gas energy is not enough to support this huge natural gas consumption. 95% of natural gas energy needs to be obtained through pipeline transportation and liquefied natural gas supplied by sea from neighboring countries. Currently, Singapore is vigorously developing photovoltaic power generation + energy storage projects to achieve diversified power supply methods.

A household photovoltaic energy storage system customized by a Singaporean customer for home users uses our company's DJSF1352RN series DC energy meters and shunts to count and predict photovoltaic power generation, energy storage battery charging and discharging power, and optimize overall energy efficiency.

2. System Application

During the day, photovoltaic power generation supplies the load, and the excess power is used to charge the battery. At night, the battery supplies power to the load. In order to better demonstrate energy distribution, optimize overall efficiency and system reliability, the customer installed DJSF1352RN series DC energy meters on the photovoltaic power generation side and the battery energy storage side. The controller detects the power generation of the photovoltaic panels and the battery charging and discharging process in real time, and predicts the power generation of the photovoltaic panels. It dynamically adjusts the charging and discharging power and timing according to the detection and prediction data, effectively ensuring that the load can operate stably and reliably.

The overall system diagram is as follows:

Figure 1 Photovoltaic power generation + energy storage system diagram

3. Product Introduction

Figure 2 DJSF1352RN DC energy meter physical picture

DJSF1352-RN rail-mounted DC energy meter supports dual-channel DC input and is designed for telecom base stations, DC charging piles, solar photovoltaic and other applications. This series of meters can measure voltage, current, power, forward and reverse electric energy and other electrical parameters in the DC system. In actual use, this series of meters can not only measure the total electric energy, but also measure the electric energy within a specified time period. The data it detects can be displayed locally, and can also be connected to industrial control equipment and computers to form a measurement and control system.

4. Product Features

Guide rail installation

Measurement of electrical parameters such as voltage, current, and power

Forward and reverse active energy measurement

Historical electricity statistics for the last 12 months

 It has the functions of calendar, timing and leap year automatic conversion, and time adjustment. The clock error sent by broadcast shall not exceed 5 minutes, and time adjustment is not allowed within 10 minutes before or after midnight. Time adjustment is only allowed once a day.

 Two sets of rate time periods can be automatically switched through the preset time. Each rate time period can be set in at least two time zones throughout the year, and at least 10 time periods can be set within 24 hours.

RS-485 communication interface, using DL/T645-2007 communication protocol and Modbus-RTU protocol, RS485 communication rate can be set at 1200bps, 2400bps, 4800bps, 9600bps.

5. Technical parameters

Technical parameters Indicators

Input Nominal value Voltage input range Current input

DC 0-1000V

See the actual wiring diagram Shunt: 0-75mV;

Hall sensor: 0-20mA, 4-20mA, 0-5V, 0-10V, etc.

Overload 1.2 times can continue normal operation, 2 times can last for 1 second

Power consumption Voltage: ≤0.2VA, current ≤0.1VA

Accuracy level 1 or 0.5

Function Display 8-bit segment code LCD

Communication interface RS485 (two channels optional)

Communication protocol Modbus-RTU, DL/T 645-2007, DL/T 698

Switching quantity Switching quantity output 2-way relay output, 2A/30VDC or 2A/250VAC

Switch input 2-way dry contact input

Pulse output One second pulse output, one electric energy pulse output

See the display in SYS->PLUS in the instrument menu setting, for example: display 100, which means 100imp/kWH

Working power supply Voltage range AC/DC 85-265V or DC24V (±10%) or DC48V (±10%)

Power consumption ≤ 3W

Power frequency withstand voltage Power supply//voltage input//current input//relay output and switch input//communication//pulse output 3kV/1min

3kV/1min between power supply, relay output, voltage signal and current signal

2kV/1min between pulse output, communication and switch input

Impulse withstand voltage ±6KV

Insulation resistance ≥ 40MΩ

Average barrier-free working time ≥ 50,000h

Environment Temperature Normal working temperature: -25℃～+65℃; Extreme working temperature: -40℃～+70℃;

Storage temperature: -40℃～+80℃

Humidity ≤ 93% RH, no condensation, no corrosive gas

Altitude ≤ 2500m

6. Conclusion

At present, the household photovoltaic market in developed overseas regions is relatively mature, and on this basis, household energy storage is also entering the fast lane of development. According to statistics from IHS Markit, a third-party research and consulting agency, the average compound growth rate since 2016 has been as high as over 50%. At present, the household energy storage market is mainly concentrated in developed regions with relatively good development of household photovoltaics, such as Europe, Australia, Singapore, etc. Therefore, in overseas photovoltaic energy storage systems, the demand for DC metering is still in explosive growth.