I. Overview

The solar photovoltaic power station is primarily composed of photovoltaic battery arrays, collection boxes, low-voltage DC cabinets, inverter cabinets, AC low-voltage cabinets, and step-up transformers, with the generated AC power directly connected to the grid. To meet the needs of power parameter detection at each stage, Acrel has launched the AGF series photovoltaic collection devices, the ACR10R series anti-reverse current monitoring devices, the APQM series online power quality monitoring devices, as well as collection boxes and grid-connection cabinets. These are applied in collection boxes, DC lightning protection cabinets, and AC cabinets, and are monitored centrally through the Acrel-2000 V8.0 photovoltaic power generation monitoring system.

APV Smart Photovoltaic String Box

In a large-scale photovoltaic power generation system, a vast number of photovoltaic battery modules are required to be connected in series and parallel to achieve the necessary voltage and current values for high efficiency. The APV series intelligent photovoltaic combiner box primarily serves to perform primary collection of the input from the photovoltaic array, reducing the wiring needed to connect the array to the inverter, optimizing the system structure, and enhancing reliability and maintainability. While providing surge protection for the collection, the APV series intelligent photovoltaic combiner box also offers functionalities such as current measurement of the photovoltaic cells, monitoring the operating status of the solar panels within the array, battery voltage, total collection power, branch power, collection box surge protector status collection, DC circuit breaker status collection, relay contact output, and selectable interfaces for wind speed, temperature, and radiometer sensors. The device is equipped with a standard RS485 interface, which can upload measured and collected power data and equipment status to the monitoring system.

Product Features

Compliant with the CGC/GF 037: 2014 technical specification for photovoltaic array combiner boxes.

The product boasts an IP65 protection rating, meeting both indoor and outdoor installation requirements.

Hall sensor utilized, isolated measurement, input of 16 channels.

Introducing photovoltaic-specific fuses with DC 1kV withstand voltage and selectable breaking current.

Optional voltage measurement function, measuring DC voltage up to 1kV.

Optional external sensor input interface, capable of monitoring radiation, temperature, wind speed, etc.

Equipped with an RS485 communication interface, utilizing ModBus-RTU communication protocol.

Multiple power supply options (DC24V, AC/DC220V, DC1000V, DC1500V) available, suitable for residential rooftop solar panels or photovoltaic power station applications.

Customizable with photovoltaic-specific DC circuit breakers, DC fuses, lightning protection devices, and other components from domestic and international brand manufacturers, tailored to customer requirements.

AGF-MxxT Series DC Current Collection Device

The AGF-MxxT series perforated photovoltaic string collector is specifically designed for intelligent photovoltaic string boxes. It is used to monitor the operating status of battery panels in the photovoltaic array, measure group and string currents, collect the status of lightning arresters within the string box, and collect the status of DC circuit breakers. The device features an RS485 interface to upload measured and collected data as well as equipment status.

In accordance with the CNCA/CTS 0001-2011A technical specifications for photovoltaic stringing equipment design, it features the following:

A single current input is made via a piercing method, with a capacity of 20A. The piercing method allows for easy installation and high safety.

2. With 3-way switch status monitoring, it can monitor the status of surge protectors and circuit breakers within the collection box.

3. Features an internal temperature measurement function, enabling real-time monitoring of the internal temperature to ensure electrical safety.

4. Features a DC 1500V bus voltage measurement function.

5. On-site display/LCD display head for convenient debugging and maintenance.

6. Equipped with RS485 interface and Modbus-RTU protocol, it uploads monitoring data to the backend system.

AGF-AE or ACR10R Series Reverse Flow Monitoring Devices

4.1 Introduction

As the photovoltaic industry expands, certain areas are experiencing saturation in the capacity of village-level transformers and industrial transformers, compared to the installed capacity of photovoltaic projects. Grid companies are requiring newly constructed photovoltaic grid-connection systems to be irreversible power generation systems, meaning that electricity generated by the photovoltaic grid-connection systems should be consumed locally, and any excess electricity is not permitted to be sent back to the upper grid via low-voltage distribution transformers.

Photovoltaic inverters, when converting DC electricity from photovoltaic panels into AC, introduce DC components and harmonics, resulting in unbalanced three-phase currents and uncertain output power. Currently, there are no effective mitigation measures in place. Consequently, when power is fed into the public grid, harmonic pollution occurs, leading to voltage fluctuations and flickering. If numerous such power sources feed into the grid, it can severely degrade the quality of electrical power. Therefore, these photovoltaic power generation systems must be equipped with anti-reverse current facilities to prevent the occurrence of reverse power.

4.2 Reverse Flow Monitoring Device Principle

Principle of Reverse Current Monitoring Device: Install a reverse current electric meter or current sensor at the grid connection point. When current flow to the grid is detected, a signal is sent to the inverter via 485 communication. The inverter then reduces its output power until the reverse current output is zero, thereby achieving reverse current prevention. Depending on the system voltage level, photovoltaic systems can be categorized into single-phase reverse current prevention systems and three-phase reverse current prevention systems.

The Ankoer AGF-AE/ACR10R series meters, as critical components for reverse current detection, utilize high-performance MCUs and high-precision measurement chips to achieve real-time detection of voltage, current, power, and energy. Data refresh rates are as fast as 250ms, meeting the real-time control requirements for inverter reverse current detection. Inverters adjust power in real-time by reading the power magnitude and direction from the AGF-AE/ACR10R series meters, achieving reverse current detection functionality.

4.3 Reverse Flow Device Selection Plan

APQM Series Online Power Quality Monitoring Equipment

5.1 Overview

Electrical energy quality is used to indicate the degree of excellence or poor quality of electrical energy, encompassing both voltage quality and frequency quality. Voltage quality is further divided into amplitude and waveform quality, usually measured by indicators such as voltage deviation, voltage fluctuations and flicker, and negative sequence voltage coefficient (degree of unbalance in three-phase voltage), to assess the amplitude of voltage. Waveform quality is measured by the voltage sine wave distortion rate. Frequency quality is evaluated by frequency deviation. Voltage quality issues can be categorized into two types: steady-state disturbances, which include voltage deviation, three-phase imbalance, flicker, and harmonic problems; and transient disturbances, which include transient overvoltage, sudden voltage drops, sudden voltage rises, and instantaneous power supply interruptions. In terms of frequency of occurrence and the level of harm to electrical equipment, modern electrical energy quality issues primarily involve sudden voltage drops, harmonics, voltage unbalance, and flicker.

The APQM series of online power quality monitoring devices is a new generation of embedded online power quality monitoring products, which our company has independently designed and developed based on the research and summary of the characteristics and practical experience of power quality monitoring devices both domestically and internationally. It strictly adheres to the relevant technical standards promulgated by the state. The series meets the requirements of the newly issued national power quality standards for the measurement and processing of various indicators.

5.2 Technical Features:

Our embedded + DSP technology ensures high-performance processing while enhancing system reliability. The entire unit features no heating or vibration components, guaranteeing long-term stable operation.

■ Excellent sampling circuit and signal synchronization technology ensure complete synchronization of all channels, with independent operation and no interference between channels. The sampling speed is fast and the accuracy is high.

To ensure data storage reliability, a large capacity storage space is adopted.

■ Equipped with 100M industrial Ethernet and RS485 communication capabilities, supports common communication protocols; locally generates PQDIF data format files and uploads them to an FTP server, facilitating integration into power quality monitoring networks.

Our system allows for flexible addition and expansion of communication protocols, data types, and setting parameters based on user requirements. Users can conveniently monitor and set power quality conditions remotely through a web browser, significantly enhancing maintenance efficiency and reducing costs.

5.3 Feature Description:

Acrel-2000V8.0 Photovoltaic Power Generation Monitoring System

6.1 Overview

The Acrel-2000 V8.0 Photovoltaic Power Generation Monitoring System is a software platform developed by Ankorui for building photovoltaic power generation systems. It provides real-time monitoring and remote parameter settings for inverters and grid-connected equipment in buildings with power capacities ranging from tens of kilowatts to megawatts. It allows for quick grasp of the power station's operation through various types of charts and data, featuring data statistics, power generation efficiency, weather condition monitoring, and fault alarms to ensure the reliable and stable operation of building photovoltaic power generation systems.

6.2 Refer to Standards

CGC/GF002-2010 "Photovoltaic String Box Technical Specification"

GB/T 2887-2011 "General Specifications for Computer Sites"

GB 50797-2012 "Code for Design of Photovoltaic Power Stations"

GB/T 31366-2015 "Technical Requirements for Monitoring Systems of Photovoltaic Power Stations"

6.3 Network Diagram

6.4 Photovoltaic Power Generation Monitoring System Software Function

6.4.1 Main System Operation Screen

The monitoring system provides a functional selection interface and offers real-time monitoring and display of the on-site environment of the photovoltaic array, including outdoor temperature values, humidity percentages, light intensity, and surface temperature values of the array.

6.4.2 Convergence Monitoring System Interface

The monitoring system can real-time divide and monitor the charging voltage and current of each photovoltaic array, as well as battery voltage and temperature, and it will display abnormality and issue alarm alerts for fault points.

6.4.3 Inverter Monitoring Display

The monitoring system can plot voltage-time and power-time curves, real-time current curves on the DC side input, and AC side inverter output current curves. It also collects and displays daily electricity generation and other electrical parameters.

6.4.4 Event Record Monitoring Screen

The monitoring system can record various events at photovoltaic power generation sites, such as communication collection anomalies, switch position changes, and operation logs. Time records support type-based queries, and settings for limit alarms can be modified.

6.4.5 Curve and Bar Chart Analysis Interface

The monitoring system can generate monthly and annual bar charts for the power generation of photovoltaic power generation, converting it into carbon dioxide and sulfur dioxide emission reduction values. It also allows for viewing trend curves of solar radiation intensity and wind speed changes.

Author's Bio:

Zhang Lingling, female, Bachelor's degree in Electric Power System and Automation, specializing in research on microgrid energy efficiency management solutions for enterprises.

Email: 2880956073@qq.com, Phone: N/A, QQ: 22880956073