Solar Power System Design: PV Module Configuration and Electrical Design
Aug 27, 2026
The Solar Power System Design is a systematic engineering process involving multiple technical aspects, including photovoltaic (PV) module selection, array layout, main electrical connections, lightning protection, and grounding. A scientifically sound and reasonable design must take into account the solar resources, climate conditions, and site characteristics of the project location, while achieving a balance among safety, economic performance, and power generation efficiency. This article focuses on two core areas of Solar Power System Design design-module configuration and the electrical system-and summarizes key technical considerations and design standards to provide guidance for engineering practice.
Solar Power System Design
1. PV Module Selection
The basic principle for selecting PV modules is to choose mainstream module types that offer a high level of technical maturity and reliable operation, while also taking into consideration the natural environment surrounding the power station, construction conditions, and transportation logistics. The final selection should be based on a comprehensive evaluation to identify the PV modules with the best overall performance and the greatest suitability for the project.
2. Design of PV Array Operating Modes
PV arrays can be installed using one of three methods: fixed-tilt, adjustable-tilt, or tracking systems. The appropriate installation method should be selected through a techno-economic comparison based on factors such as solar radiation resources, climate conditions, operating environment, installed capacity, the area and characteristics of the installation site, load characteristics, and operation and management practices.
The layout configuration of the PV support structures should be selected appropriately to avoid stress concentration. Suitable cross-sections should be selected for each structural member according to the magnitude of the applied forces. Steel consumption should be minimized while ensuring that the strength of all structural members is fully utilized.
Throughout the design life, the PV support system must remain structurally safe and reliable and be capable of withstanding wind and snow loads as well as environmental effects. The feasibility of installation must also be considered so that the optimal project construction results can be achieved at the lowest possible cost. When designing and constructing a PV power station, the selection of the support structure type should be adapted to local conditions through a comprehensive evaluation. A comparison of different types of PV support structures is provided in table 1.
Table 2
| No. | Item | Fixed Support Structure |
Horizontal Single-Axis Tracking Structure |
Tilted Single-Axis Tracking Structure |
Dual-Axis Tracking Structure |
Fixed Adjustable-Tilt Support Structure |
| 1 | Wind Resistance and Civil Foundation |
Designed for the governing load case based on the local maximum wind speed to determine the wind resistance of the support structure | Wind resistance is the same as that of the fixed support structure; actual load-bearing requirements are lower than those of the fixed support structure | Wind resistance is the same as that of the fixed support structure; foundation requirements are higher than for the horizontal single-axis tracker but lower than for the fixed support structure | Wind resistance is the same as that of the fixed support structure; under the governing load case, foundation requirements are similar to those of the tilted single-axis tracker | Wind resistance is the same as that of the fixed support structure |
| 2 | Installation Requirements |
No moving parts; low installation-accuracy requirements and relatively simple installation | Moving parts are present; installation requires higher accuracy and is more complex than for the fixed support structure | Moving parts are present and a south-facing tilt is added; installation accuracy requirements are slightly higher and installation is slightly more complex than for the horizontal single-axis structure | Dual-axis tracking components and more moving parts; highest installation-accuracy requirements and most complex installation | Similar to the fixed support structure; the main beam is a moving component, but there are fewer moving parts than in tracking structures |
| 3 | Technical Maturity |
Simple system, widely used, and technically mature | Mature technology, with domestic applications at approximately the GWp scale | Tilted single-axis technology adds installation tilt; slightly less mature than the horizontal single-axis structure | Most complex technology; no large-scale application cases domestically or internationally | Highly mature technology |
| 4 | Applicable Latitude |
No restriction | Mid- to high-latitude regions | No restriction | No restriction | Low-latitude regions |
| 5 | Reliability | Simple and reliable | The quality and reliability of key drive and control equipment must be controlled; reliability is lower than that of the fixed support structure | Adding tilt makes operating conditions slightly more complex; reliability is slightly lower than that of the horizontal single-axis structure | Universal joints are prone to damage and the control system is complex, resulting in a much higher failure rate than single-axis tracking structures and low reliability | Reliability is close to that of the fixed support structure and higher than that of tracking structures |
| 6 | Land Area per MW |
Approximately 25 mu on flat terrain |
Approximately 30 mu; land area increases by approximately 15% |
40 mu; land area increases by approximately 50% |
50 mu; land area increases by approximately 100% |
Approximately 28 mu; land area increases by approximately 10% |
| 7 | Reference Unit Cost |
0.3–0.4 yuan/Wp |
Increase of 0.3–0.4 yuan/Wp compared with the fixed support structure |
Increase of 0.4–0.5 yuan/Wp compared with the fixed support structure |
Increase of 1.4–2.5 yuan/Wp compared with the fixed support structure |
Increase of 0.1–0.2 yuan/Wp compared with the fixed support structure |
| 8 | Power Generation Benefit |
Assumed at 100% | 110%–120% | 120%–125% | 130%–140% | 100%–110% |
| 9 | 25-Year O&M Cost Comparison |
Over 25 years, basically maintenance-free |
Over 25 years, compared with the fixed support structure, the main additions are routine inspection and lubrication of mechanical equipment | Over 25 years, slightly more complex than the horizontal single-axis tracking system | Over 25 years, the tracking system is the most complex and requires extensive training | Manual adjustment is required; adjustment is performed four times per year; operation is relatively simple |
3. Inverters and Combiner Boxes
The inverters used in PV power stations mainly include three types: central inverters, string inverters, and distributed inverters. The applicable scenarios for these three commonly used inverter types may be determined with reference to Table 2.
When selecting inverters, particular attention should be paid to the manufacturer's industry track record, after-sales service, future equipment upgrade costs, and upgrade redundancy. The inverter should be selected according to the actual site conditions and project requirements. Inverter models with high conversion efficiency should be given priority.
Table 2
| Technical Parameters | Central Inverter | String Inverter | Distributed Inverter |
| Applicable Scenarios | Suitable for scenarios with consistent module angles and relatively large project scales | Suitable for applications with significant differences in module angles or relatively small project scales | Suitable for scenarios with significant differences in module angles and relatively large project scales |
4. PV Array Layout of Solar Power System Design
The capacity ratio between the PV array and the inverters in a PV power station should be determined through a techno-economic comparison, taking into comprehensive consideration factors such as the PV array installation type, site conditions, solar energy resources, and various system losses. The ratio of the installed capacity of the PV array to the rated capacity of the inverter is recommended to comply with the following requirements:
Class I solar resource regions: should generally not exceed 1.2;
Class II solar resource regions: should generally not exceed 1.35;
Class III solar resource regions: should generally not exceed 1.5.
The design of the spacing between support structures primarily takes into account shadowing between adjacent structures. In the Northern Hemisphere, the optimum orientation for PV modules is due south. The minimum spacing should be determined according to the following criterion: from 9:00 a.m. to 3:00 p.m. solar time on the winter solstice, the projection of the front-row modules in the northward direction should not reach the lower edge of the modules in the rear row. In other words, there should be no shadowing in the north-south direction.
This criterion is based on the extreme operating condition of the winter solstice, when the solar elevation angle is at its lowest and shadows are at their longest. It ensures that system output is not affected by shading during any period of the year.
The design of the clearance between the PV modules and the ground-that is, the height of the lowest point of the modules above the ground-is mainly affected by factors such as the requirements for combined land use within the PV site, flood-control requirements, shading of the modules by surrounding obstacles, ground vegetation coverage, and "PV +" applications. When bifacial PV modules are used, power generation efficiency must also be taken into consideration.
The advantage of bifacial PV modules over monofacial modules is that the greater the amount of light received on the rear side, the greater the bifacial gain. The main factors affecting rear-side energy gain include ground albedo, support structure height, irradiance conditions, and row spacing. The resulting benefits vary with the seasons.
When determining the minimum clearance between the PV support structures and the ground, the above factors should be considered comprehensively, while safety and economic performance should be balanced as far as possible. Increasing the minimum height of the PV modules above the ground to an appropriate extent can improve power generation efficiency and increase energy yield to some degree. However, it also increases the costs of the support structures and foundations, thereby having a certain impact on the project's economic performance.
Electrical Design of Solar Power System Design
1. Main Electrical Connection
A PV power station consists of one or more power generation units. The main electrical connection determines how these generation units are interconnected and collected. After local step-up transformation, the power generated by each unit is collected and fed into the busbar of the step-up substation.
The voltage level of the step-up substation busbar should not only comply with the structure and long-term planning of the local power grid, but should also be determined by comprehensively balancing factors such as the capacity of the PV power station, initial construction investment, and operation and maintenance costs. Depending on the type of PV power station, common busbar voltage levels include 0.4 kV, 6 kV, 10 kV, and 35 kV.
The main electrical connection of the power station can be planned according to the construction schedule. If the power station is constructed and commissioned in a single phase and has only one grid-connection point, a single-busbar configuration can generally be adopted. If the power station is constructed and commissioned in phases, or has two or more grid-connection points, a sectionalized single-busbar configuration is generally more appropriate.
2. Power Distribution Equipment
The layout of the power distribution equipment should be selected after comprehensive consideration of factors such as the project's geographical location, local climate conditions, available site area, and altitude. The equipment may be installed indoors or outdoors depending on the specific conditions.
At present, 10–35 kV power distribution equipment in domestic PV power stations is generally installed indoors. Indoor armored, withdrawable, AC metal-enclosed switchgear is the primary configuration. In some regions, 10–35 kV power distribution equipment may also use sulfur hexafluoride (SF₆) gas-insulated metal-enclosed switchgear where this is technically and economically justified, particularly for protection against salt spray, enhanced insulation, or reduced land use.
In recent years, with the development of technology, prefabricated cabin-type power distribution equipment has become increasingly common. Switchgear stations can be prefabricated in factories and assembled modularly on site. This approach reduces on-site construction and commissioning work, shortens the construction period, saves energy, protects the environment, and reduces the land area required for the switchgear station. It may be given priority where technically and economically appropriate.
3. Lightning Protection and Grounding of Solar Power System Design
A main grounding grid that covers the entire PV field is normally installed within a PV power station. The outer boundary of the main grounding grid should generally correspond to the boundaries of the PV field and form a closed loop.
The main grounding grid consists of a network formed by connecting horizontal grounding conductors in the transverse and longitudinal directions to the module support structures. Vertical grounding electrodes should be evenly distributed along the edges and within the grounding grid. The foundations of the module support structures should also be used as natural grounding electrodes wherever possible.
The main grounding grid of a PV power station generally uses galvanized flat steel or round steel as the main grounding conductor. The grounding resistance of the main grounding grid in the PV field should not exceed 4 Ω.
For grounding between PV modules and their metal support structures, the most common method is to first establish a reliable connection between the metal frames of adjacent PV modules using copper conductors, and then connect both ends of each row of PV modules to the metal support structure.
For some rooftop PV projects where grounding copper conductors are inconvenient to install, metal connectors may be used as conductors between the modules and the support structures. When this method is adopted, the connectors should be fitted with stainless-steel washers capable of penetrating the protective aluminum-oxide film on the module frames, thereby ensuring good electrical continuity between the module frames and the metal support structures.
The module support structures may first be bonded equipotentially to adjacent support structures to form a grounding group, which is then connected to the grounding grid. To ensure reliability, each support-structure grounding group should be connected to the grounding grid at no fewer than two points. These connection points should be installed at both ends of each row of support structures.
A ring-shaped equipotential grounding grid should be installed around each local step-up transformer in the PV field and reliably connected to the main grounding grid of the PV field. When a local step-up transformer uses a box-type transformer with an integral metal enclosure, the enclosure should be reliably connected to the equipotential grounding grid at no fewer than two points. All exposed metal parts of the box-type transformer, including metal ladders, should also be connected to the grounding grid.
4. Cable Selection and Installation of Solar Power System Design
The cables installed between PV modules and string combiner boxes or string inverters in a PV power station are generally dedicated PV cables. Their resistance to ultraviolet radiation, weather resistance, flame-retardant performance, and other characteristics should comply with the requirements of current industry standards.
For distributed PV projects, cables used in building-integrated or building-mounted PV systems should have good flame-retardant performance. Copper conductors are generally selected because of their favorable electrical conductivity.
For utility-scale PV power stations, cables are usually distributed over a large area. Therefore, cables are generally installed using direct burial, in which case armored cables should be used. In particular, for projects where the land parcels occupied by the PV module areas are dispersed, 10 kV or 35 kV overhead lines may be used as collector circuits.
Because poles and towers within the PV array area may cast shadows on the PV modules, the shadow range of overhead lines should be calculated during line planning. The line layout should be coordinated with the PV array layout to minimize shading of the modules.
When determining the lengths of AC and DC cables in a PV system, both cable ampacity and system voltage drop should be taken into consideration. The AC voltage drop in a PV system should generally not exceed 3%, while the DC voltage drop should generally not exceed 2%.
If the voltage drop does not meet the applicable requirements, the cross-sectional area of the relevant cable should be increased, or the relative positions of the equipment should be adjusted to shorten the cable route and keep the voltage drop within the specified limits.
5. Monitoring System
PV power stations in China generally operate on an unmanned or minimally staffed basis. Some ground-mounted PV power stations have begun adopting remote monitoring to replace on-site staffed operation. During the design stage, the current phase of the project is normally treated as the primary consideration, while the preceding and subsequent phases are also taken into account. The system should be compatible with the levels of automation and operation and management adopted by the power station.
Most PV power stations in China use separate monitoring systems for the step-up substation or switchgear station and the PV array area. This approach has the advantage of requiring only a limited amount of information exchange between the step-up substation monitoring system and the PV monitoring system, making implementation relatively straightforward. However, it also has the disadvantage of low information utilization.
After the adoption of an intelligent monitoring system, a PV power station can achieve comprehensive data acquisition and panoramic monitoring of the entire facility. The system can establish vertical integration with major systems such as dispatching and production management systems, while also providing horizontal connectivity with the main automation equipment within the power station.
An intelligent monitoring system can also support functions such as economic operation decision-making, online diagnosis and automatic recovery, automatic inspection and fault analysis, and fault warning.
Conclusion
The Solar Power System Design requires comprehensive coordination across all stages, including module selection, array layout, electrical connections, cable installation, and monitoring systems. The optimal solution should be selected according to local conditions and project requirements. With the continuous advancement of PV technology and increasing levels of intelligence, system design is facing higher requirements as well as more possibilities. Scientific planning and detailed design are essential to ensuring the safe and stable operation of a power station and achieving strong economic performance.
