Solar Panel Connection Tips

Solar panels installed on different sunny surfaces (such as horizontally on the roof and vertically on the wall) may have significant differences in power generation efficiency and output characteristics (voltage, current) due to the large differences in lighting angles. When connecting inverters, it is necessary to design them reasonably according to their characteristics to avoid mutual influence. The specific analysis is as follows:

1、 The problem of direct series/parallel connection

1. The risk of direct serial connection

In a series circuit, the total current is equal to the minimum current of each component, and the total voltage is the sum of the voltages of each component.

-If there is a large difference in lighting between the roof panel and the wall panel (such as the roof panel having strong noon light and high current; the wall panel may have low current due to angle issues), the overall current will be "pulled down" by the wall panel with low current after being connected in series, resulting in the roof panel's power generation potential not being fully utilized and the total power significantly decreasing.

-In extreme cases (such as one side being obscured by shadows), excessive current differences may cause "hot spot effects" and damage components or inverters.

2. Risk of direct parallel connection

In a parallel circuit, the total voltage is equal to the minimum voltage of each component, and the total current is the sum of the currents of each component.

-If there is a large voltage difference between the two (such as high voltage when the roof panel is illuminated strongly and low voltage when the wall panel is illuminated), the total voltage after parallel connection will be "pulled down" by the low-voltage components, and the excess voltage of the high-voltage components will form a circulating current through the circuit, causing energy loss, component heating, and even burning of the wiring terminals.

2、 Reasonable access methods and technical means

1. Independently connect different MPPT channels of the same inverter

Mainstream inverters, especially string inverters, are typically equipped with multiple independent MPPT (Maximum Power Point Tracking) channels.

-Operation: Connect the rooftop solar panel string to one MPPT channel of the inverter, and connect the wall mounted solar panel string to another MPPT channel.

-Principle: Each MPPT channel can independently track the maximum power point of the corresponding component string, without being affected by another string. Even if there is a large difference in voltage and current between the two, they can still operate at their optimal state, with a total power of the sum of the two strings.

-Advantages: No need for additional equipment, strong compatibility, and is the most commonly used solution.

2. Use micro inverters or power optimizers

-Micro inverter: Each (or every few) solar panel is equipped with a micro inverter, which directly converts DC to AC and connects it in parallel to the power grid. Each board works independently, completely avoiding mutual influence.

-Power Optimizer: Connected in series between each board and the inverter, it adjusts the voltage/current of each board in real time to match the output characteristics of the entire series of components, and then connects to the MPPT channel of the inverter. Suitable for scenarios with a large number of components and complex installation conditions.

-Advantages: Maximize the power generation efficiency of each board, especially suitable for situations with large differences in lighting, but the cost is relatively high.

3. Design component string parameters grouped by orientation

If only one MPPT channel can be shared, it is necessary to try to make the voltage and current ranges of the two series components as close as possible (such as by adjusting the number of series connections).

-For example, 72 pieces of roof panels are connected in series (with higher voltage), and 60 pieces of wall panels are connected in series (with slightly lower voltage), so as to control the voltage difference between the two within ± 10% and reduce the mismatch loss during parallel/series connection (to be calculated based on specific parameters).

3、 The consequences of improper use

1. Severe decrease in power generation efficiency: Series/parallel mismatch can result in a total power output far below the sum of two separate series, with a potential loss of up to 30% of the generated electricity.

2. Equipment damage risk: Circulation and hot spot effects may cause component cracking, junction box burnout, and even trigger inverter overcurrent protection, resulting in system shutdown.

3. Shorten lifespan: Long term non optimal working conditions can accelerate component aging (such as uneven battery cell decay), inverter component loss, and reduce the overall lifespan of the system.

summary

It is strictly prohibited to directly connect solar panels with different orientations in series/parallel to the same MPPT channel. The optimal solution is to use multiple MPPT channels of the inverter for independent connection. If conditions are limited, micro inverters or power optimizers can be used. The core principle is to allow component strings with large differences in lighting conditions to work independently and do their best, avoiding mutual interference.