Compatibility Analysis of 20kW Solar Battery with Power Grid

　　I. Core Influencing Factors of Compatibility

　　(I) Technical Parameter Matching

　　Voltage Matching: The rated voltage of the power grid is usually 220V (single-phase) or 380V (three-phase) (in line with China's low-voltage distribution network standards). A 20kW solar battery system needs to convert its DC output to AC consistent with the grid voltage through an inverter, and the voltage fluctuation range must comply with GB/T 19939-2005 Technical Requirements for Grid-Connected Photovoltaic Systems, i.e., the voltage deviation shall not exceed ±7%.

　　Frequency Synchronization: The grid frequency is fixed at 50Hz. The inverter of the solar battery system must be equipped with a frequency tracking function to ensure that the output frequency is synchronized with the grid. The frequency deviation shall be controlled within ±0.5Hz (under normal operation) or ±1Hz (under fault transient state) to avoid grid-connected protection tripping due to frequency imbalance.

　　Power Factor Control: The power grid requires that the power factor of grid-connected photovoltaic systems be between 0.8 (leading) and 0.9 (lagging) (in accordance with DL/T 1194-2012 Terms for Power Quality). A 20kW system needs to meet the grid's dynamic requirements for power factor through the reactive power regulation function of the inverter to avoid affecting the stability of the grid voltage.

　　(II) Requirements for Grid-Connected Equipment

　　Inverter Selection: A grid-connected inverter with a rated power matching that of the 20kW solar battery bank shall be selected (usually a 20-25kW inverter, with 10%-20% power redundancy reserved). In addition, the inverter must pass national certifications (such as CNC certification) and be equipped with core functions including overvoltage protection, overcurrent protection, and islanding effect protection (in accordance with GB/T 20046-2019 Technical Requirements for Grid-Connected Photovoltaic Inverters), so as to quickly disconnect from the grid in case of grid faults and ensure grid safety.

　　Metering and Protection Devices: A bidirectional electric energy meter that complies with grid specifications shall be configured (for metering the electricity fed into the grid and the electricity drawn from the grid). Meanwhile, overcurrent protectors, leakage protectors, and surge protectors shall be installed to prevent damage to grid lines and equipment caused by faults of the solar battery system.

　　II. Prerequisites for Compatibility

　　(I) Evaluation of Grid Acceptance Capacity

　　A 20kW solar battery system belongs to a small and medium-sized distributed photovoltaic project. It is necessary to submit a grid-connection application to the local power grid company (such as State Grid Corporation of China, China Southern Power Grid) in advance, and the power grid company will evaluate the capacity of the distribution network at the connection point (e.g., transformer load rate, line current-carrying capacity). If the load rate of the transformer at the connection point is too high (e.g., exceeding 80%) or the line capacity is insufficient, the distribution network may need to be upgraded (e.g., transformer capacity expansion, conductor replacement) before grid connection.

　　Sharing the same power distribution circuit with other high-harmonic loads (such as electric welders, frequency converters) shall be avoided to prevent harmonic superposition from affecting the power quality of the grid. If necessary, a harmonic filtering device shall be configured in the solar battery system.

　　(II) Compliance with Policies and Regulations

　　It is necessary to comply with local distributed photovoltaic grid-connection policies, such as the Notice of the National Energy Administration on Issuing the Interim Measures for the Administration of Distributed Photovoltaic Power Generation Projects, and complete processes including project filing and approval of grid access plans to ensure that the grid-connection behavior is legal and compliant.

　　Some regions have additional requirements for distributed photovoltaic grid connection (e.g., restrictions on grid-connection voltage levels, selection of electricity consumption modes for the power fed into the grid: full grid feed-in, self-consumption with surplus power fed into the grid). It is necessary to communicate and confirm with the power grid company in advance to avoid compatibility issues caused by non-compliance with policies.

　　III. Compatibility Risks and Countermeasures

　　(I) Common Risks

　　Islanding Effect: If the islanding protection function of the inverter fails, the solar battery system will still supply power to the local grid when the main grid is cut off, which may endanger the safety of maintenance personnel or cause voltage and frequency shocks when the grid is restored.

　　Voltage Overlimit: If the 20kW system is connected to a distribution network with long lines and low load, the photovoltaic output may cause the voltage at the end of the line to rise (exceeding 1.07 times the rated voltage), triggering grid protection tripping.

　　(II) Countermeasures

　　Conduct regular maintenance on the inverter, and test the effectiveness of functions such as islanding protection and overvoltage protection to ensure reliable operation in case of faults.

　　If there is a risk of voltage overlimit, dynamic reactive power compensation devices such as SVG (Static Var Generator) or STATCOM (Static Synchronous Compensator) can be configured in the system, or an "active power control" strategy can be adopted to adjust the output power of the solar battery system according to changes in grid voltage.

Read recommendations:

Lithium-ion Batteries for Energy Storage Inverters

Portable Power Station with Solar and Multiple Output Ports for Electronics

PB600EU

1000w solar power station

PB600US