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Electrical Configuration of Photovoltaic Systems

Release time:

2026-04-24

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Abstract

Driven by the global energy transition and carbon neutrality goals, photovoltaic systems, as the core platform for clean energy, rely on the rationality of their electrical configuration to directly determine power generation efficiency, operational stability, and life-cycle economic performance. This paper systematically outlines the key technical considerations and practical implementation pathways for the electrical configuration of photovoltaic systems across four dimensions: selection of core equipment, system topology design, safety protection systems, and intelligent upgrades.

I. Core Equipment Selection: Balancing Efficiency and Reliability

The core equipment of a photovoltaic system includes photovoltaic modules, inverters, transformers, and cables, and their selection must balance technical performance with site-specific suitability.

1. Photovoltaic Modules

The current mainstream technology landscape is highly diversified: monocrystalline silicon modules, with conversion efficiencies exceeding 22%, dominate the high-end market and are well suited for distributed projects in areas with limited land availability; polycrystalline silicon modules, offering efficiencies of 15%–18% at lower costs, lead the large-scale ground-mounted power plant segment; thin-film modules, such as cadmium telluride, excel in low-light conditions and can be custom-designed for building façades; a notable example is the “photovoltaic–storage–direct–flexible” system at the Shenzhen Institute of Building Research’s Future Building, where thin-film modules deliver 30% higher energy output compared with silicon-based counterparts. Bifacial, double-glass modules further boost power generation through rear-side gains of 5%–30%, delivering particularly strong performance in high-reflectivity environments such as snowy or sandy terrains.

2. Inverter

Central inverters are well suited for large-scale power plants with uniform module layouts; however, they feature a limited number of MPPT trackers and are highly sensitive to shading. String inverters, by contrast, employ multiple independent MPPT trackers to optimize each string individually, which can boost power generation efficiency by 5%–8% in complex terrains such as mountainous solar farms. For example, a 100 MW photovoltaic power plant in Yanbian Prefecture, Jilin Province, uses 50 kW string inverters equipped with four MPPT trackers that independently track strings oriented in different directions, resulting in a 12% increase in annual energy output compared with a central inverter solution. In addition, smart inverters integrate features such as PID protection and reactive power compensation, which can reduce system losses by more than 3%.

3. Transformers and Cables

Transformer selection must match the grid voltage level: oil-immersed transformers, owing to their superior protection performance and lower cost, are widely used in outdoor substations, while dry-type transformers are suitable for indoor applications or settings with stringent fire-protection requirements. Cable selection should comprehensively consider current-carrying capacity, voltage rating, and environmental adaptability: on the DC side, photovoltaic-specific cables (such as PV1-F) are employed, whose weather resistance and UV stability can ensure a service life of 25 years; on the AC side, YJY23 armored cables are chosen based on the installation environment, with particular attention paid to ensuring burial depth exceeds the frost line in cold regions.

II. System Topology Design: From Serial Connection to Intelligent Networking

The electrical topology of a photovoltaic system directly affects energy transmission efficiency and fault-tolerant capability, and must be flexibly designed based on the project scale and site-specific conditions.

1. String-level optimization

In traditional string-based configurations, a failure of a single module can cause the entire string to shut down. Modern systems mitigate this by incorporating string optimizers or deploying smart shutdown technologies, enabling module-level monitoring and rapid shutdown. For instance, the 17.23 MW BIPV project at Henan Wanda Aluminum employs a “one optimizer per module” design, reducing power losses caused by shading from 15% to below 3%.

2. DC-side voltage matching

The number of modules connected in series must fall within the inverter’s MPPT voltage range (e.g., 80 V to 600 V), while also accounting for the increase in open-circuit voltage at low temperatures. For example, in a project in Jilin that uses 270 W polycrystalline silicon modules, the open-circuit voltage of a string reaches 980 V under the extreme low-temperature condition of −37.5°C, necessitating a reduction in the number of modules per string—from 24 to 22—to ensure voltage safety.

3. Grid-connection architecture on the AC side

Distributed projects typically employ a “string inverter + AC combiner box” configuration to simplify installation and reduce losses; larger power plants, by contrast, tend to use a “central inverter + packaged transformer” solution, with 1,000 kVA or 1,600 kVA packaged transformers used to step up the voltage and isolate individual units. The 50 MW solar-plus-storage project in Dengkou, Inner Mongolia, innovatively adopts a 1,500 V system, reducing DC-side losses by 40% and cable costs by 15%.

III. Security Protection System: From Passive Defense to Proactive Early Warning

The safety configuration of photovoltaic systems must encompass three key dimensions: lightning protection and grounding, overload protection, and intelligent monitoring.

1. Lightning Protection and Grounding System

Lightning rods and surge protective devices (SPDs) provide dual protection: a primary SPD (10/350 μs waveform) is installed at the top of the module mounting structure to divert direct lightning current, while a secondary SPD (8/20 μs waveform) is deployed on the AC side of the inverter to limit induced overvoltages. The grounding grid adopts a composite structure consisting of horizontal grounding conductors (flat steel) and vertical grounding electrodes (angle steel), with a grounding resistance requirement of ≤4 Ω; in arid regions, this can be reduced to 10 Ω through the use of soil resistivity-reducing agents.

2. Electrical Protection Devices

On the DC side, DC circuit breakers and fuses are installed, with rated currents sized to accommodate 1.25 times the string’s maximum short-circuit current; on the AC side, smart circuit breakers are employed, integrating overload, short-circuit, and earth-fault protection functions. The 5,200 kW project at Fujian Huayu Weaving utilizes a full-link encrypted monitoring system that achieves fault location accuracy within 3 meters and reduces response times to the millisecond level.

IV. Intelligent Upgrading: From Data Acquisition to the Energy Internet

With the increasing integration of digital twin and AI technologies, photovoltaic systems are evolving from standalone power-generation units into intelligent energy nodes.

1. Intelligent Monitoring Platform

The SCADA system is used to collect component voltage, current, and environmental parameters in real time, which are then combined with an LSTM neural network to predict the power generation curve. In China Tower’s forest fire prevention project, 254 monitoring stations have been deployed, and PowerCatcher technology has been employed to achieve a maximum power point tracking (MPPT) efficiency exceeding 99%, resulting in an 18% increase in annual power generation.

2. Energy Management System (EMS)

The Energy Management System (EMS) achieves coordinated optimization of power generation, energy storage, and electricity consumption by integrating meteorological data, electricity price information, and equipment status. For example, an integrated solar–storage–charging project in an industrial park in Jiangsu Province employs a hierarchical EMS architecture: the upper layer uses deep reinforcement learning models to forecast daily power generation and load demand; the middle layer leverages edge computing nodes to dynamically adjust energy storage charging and discharging strategies in real time; and the lower layer controls flexible loads such as charging stations and air-conditioning units. During summer peak-demand periods, this system utilizes stored energy and surplus photovoltaic power to meet 80% of the park’s electricity needs, reducing procurement costs by 25%; in winter, it charges batteries during off-peak nighttime hours and provides low-cost charging services for electric vehicles during the day, resulting in a 12% increase in annual overall revenue. In addition, the EMS’s bidirectional communication capability with the grid dispatch system enables the project to participate in demand response programs, allowing it to rapidly curtail 500 kW of load during grid peak-shaving periods and earn ancillary service compensation. As virtual power plant (VPP) technology matures, future EMS solutions will further integrate distributed photovoltaic systems, energy storage, and interruptible loads, leveraging blockchain technology to facilitate cross-regional energy trading. This will drive the evolution of photovoltaic systems from a “self-generation and self-consumption” model to a “prosumer” model, providing critical support for the development of a new-type power system.

Key words:

Principle of Capacitor Compensation

How to Extend the Lifespan of Electrical Equipment

Hunan Chengyuan Electrical CO.,LTD

Electrical Configuration of Photovoltaic Systems