Household photovoltaic grid-connected power generation systems - Part 2-5: Design

Standardize system access design

Residential grid-connected photovoltaic system-Part 2-5:Design specifications-grid connection

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August 26, 2022

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Household photovoltaic grid-connected power generation systems - Part 2-5: Design specification - system access design

1 range

2 Normative reference files

State Electricity Regulatory Commission Decree No. 5 Power secondary system safety protection provisions

3 Terms and Definitions

3.1

4. Universal requirements

4.1 Access Adaptability

4.1.1 Grid voltage range

4.1.2 Power frequency range

4.2 Starting and Stopping

4.3 Power Quality

4.3.1 Harmonics and interharmonics

4.3.2 Voltage deviation

4.3.3 Voltage fluctuation and flicker

4.3.4 DC component

4.3.5 Three-phase voltage Unbalance

4.4 Security and Protection

4.4.1 Anti-island protection

4.4.2 Residual Current Protection

4.4.3 Voltage and frequency protection

4.4.4 Short Circuit Protection

4.4.5 Isolation and switching

4.4.6 Reverse Power Protection

4.5 Electric Energy Measurement

4.6 Communication

4.7 Power factor adjustment

4.8 Security Identifier

5 Requirements for grid-connected equipment

5.1 Inverter Connection Requirements

5.2 Adding Cages to the System

5.2.1 Requirements for grid-connected interface Circuit breakers

5.2.2 Requirements for over and under voltage protection and automatic reclosing

5.2.3 Requirements on Lightning Protection and Surge Protection

5.2.4 Requirements for Obvious Disconnect Points

5.2.5 Grounding Requirements

6 Grid-connected access mode

6.1 Overview

6.2 Full Internet Access

6.3 Connecting to the Internet for Self-use and Surplus power

6.4 All for personal use

Household photovoltaic grid-connected power generation systems - Part 2-5: Design specification - system access design

1 range

This document specifies the basic requirements to be followed for household photovoltaic grid-connected power generation systems to be connected to the grid.

This document applies to access users with 220V or 380V voltage class built in residential fixed buildings, structures and ancillary places

For household photovoltaic grid-connected power generation system of side grid or public grid, the single point access capacity of 220V voltage class should not exceed 8kW,380V

Voltage level The single-point access capacity should not exceed 400kW. This document does not apply to photovoltaic systems with energy storage, concentrating photovoltaic systems and BiPVs

The system.

2 Normative reference files

The contents of the following documents constitute the essential provisions of the documents through normative references in the text. Where, note the date of the citation

Only the version corresponding to that date applies to this document: the reference document without noting the date, its latest version (including all amendment orders)

Suitable for wood files.

GB/T 2297 Terms for solar photovoltaic energy systems

GB 2894 Safety marks and guidelines for their use

GB/T 12325 Power quality Power supply voltage deviation

GB/T 12326 power quality voltage fluctuation and flicker

GB/T 13955 Residual current action protection device installation and operation

Low-voltage switchgear and controlgear - Part 2: Circuit breakers

GB/T 14549 Power quality Public grid Harmonics

GB/T 15543 Power quality Three-phase voltage imbalance

GB/T 24337 Power quality Intergrid harmonics

GB/T 29319 photovoltaic power generation system access to the distribution network technical regulations

GB 50054 Specification for design of low-voltage distribution

GB 50057 Code for design of lightning protection for buildings

GB/T 50065 Design specification for grounding of AC electrical devices

NB/T 32004 Technical specification for grid-connected photovoltaic inverters

NB/T 42142 Technical specification for photovoltaic grid-connected micro inverters

DL/T 448 electric energy metering device technical management regulations

DL/T 645 Multifunctional watt-hour meter communication protocol

State Electricity Regulatory Commission Decree No. 5 Power secondary system safety protection provisions

3 Terms and Definitions

The terms and definitions defined in GB/T 2297 and the following apply to this document.

3.1 point of interconnection(POI) Output summary point of the PV power generation system.

gird-connected box Gird-Connected box is used to connect the photovoltaic power station and the power distribution device of the power grid between the AC output side of the inverter of the photovoltaic power generation system and the connecting point or load.

point of connection point of conmon coupling(PCC) where photovoltaic (power generation or electricity consumption) is connected to the public power grid.

3.4 islanding

A state in which the part of the grid containing load and power continues to operate in isolation from the main network. Islands can be divided into unplanned islands and planned islands.

Note: Unplanned island refers to an unplanned and uncontrolled island. Planned island refers to the occurrence of planned islands according to pre-configured control policies.

3.5 anti-islanding Anti-islanding Prevents unplanned islanding.

4. Universal requirements

4.1 Access Adaptability

4.1.1 Grid voltage range

The grid voltage of photovoltaic power generation system is between 85% and 110% nominal voltage.

4.1.2 Power frequency range

The grid connection frequency of the photovoltaic power generation system is within the range of 49.5Hz ~ 50.2Hz.

4.2 Starting and Stopping

The startup, shutdown and restoration of the photovoltaic power generation system shall meet the requirements of GB/T 29319.

4.3 Power Quality

4.3.1 Harmonics and interharmonics

After the photovoltaic power generation system is connected to the power grid, the sub-harmonics and inter-harmonics of the connecting point should meet the requirements of GB/T 14549 and GB/T 24337.

4.3.2 Voltage deviation

After the photovoltaic power generation system is connected to the power grid, the voltage deviation of the connecting point should meet the requirements of GB/T 12325.

4.3.3 Voltage fluctuation and flicker

After the photovoltaic power generation system is connected to the power grid, the voltage fluctuation and flicker of the connecting point shall meet the requirements of GB/T 12326.

4.3.4 DC component

The amount of DC current injected by the PV system into the common connection points should not exceed 0.5% of its AC current rating.

4.3.5 Three-phase voltage Unbalance

The three-phase voltage unbalance of 0.4kV system caused by the access of photovoltaic power generation system should meet the requirements of GB/T 15543.

4.4 Security and Protection

4.4.1 Anti-island protection

The photovoltaic power generation system should have the ability to quickly monitor the island and disconnect from the power grid immediately, and the anti-island protection action time should not be more than 2s.

4.4.2 Residual Current Protection

The photovoltaic power generation system shall have the function of residual current detection and protection, and shall meet the relevant requirements of GB13955, GB50054, NB/T32004, etc.

4.4.3 Voltage and frequency protection

4.4.3.1 Voltage protection

When the grid connection voltage of the photovoltaic power generation system is within the voltage range specified in Table 1, the power supply to the grid shall be stopped within the corresponding time.

Table 1 Protective action time requirements for abnormal voltage at connecting point of photovoltaic power generation system

Junction voltage (V)

Protective action time (s)

U<50% un="">

The maximum switching time does not exceed 0.2

Un 50% Un acuities were U < 85%

The maximum switching time does not exceed 2.0

Un 85% or less U Un 110% or less

Continuous operation

Un 110% or less U Un 135% or less

The maximum switching time does not exceed 2.0

U 135% or greater Un

The maximum smell time is not more than 0.2

Note 1:Un refers to the rated voltage of the grid at the connecting point of the photovoltaic power generation system

Note 2: The maximum switching time refers to the time between the occurrence of abnormal state and the stop of power supply to the grid

4.4.3.2 Frequency Protection

When the connecting point frequency of the photovoltaic power generation system exceeds the operating range of 49.5Hz to 50.2Hz, the power supply to the grid should be stopped within 0.2s.

4.4.4 Short Circuit Protection

The photovoltaic power generation system shall be equipped with short circuit protection for the power grid. When the power grid is short circuit, the overcurrent of the inverter shall be no more than 150% of the rated current, and the photovoltaic power generation system shall be disconnected from the power grid within 0.1s.

4.4.5 Isolation and switching

Manual and automatic circuit breakers should be installed in parallel cages connected to the photovoltaic power generation system and the power grid.

4.4.6 Reverse Power Protection

When the photovoltaic power generation system works in the grid-connected mode without countercurrent, it should be equipped with reverse power protection. When the reverse current is detected to exceed 5% of the rated output, the photovoltaic power generation system should automatically reduce the output within 0.5s to 2s or disconnect the photovoltaic power generation system from the grid.

Restoration of grid connection

After the system is disturbed, the photovoltaic power generation system is not allowed to connect to the grid before the grid voltage and frequency return to the normal range, and after the system voltage frequency returns to the normal range, the photovoltaic power generation system needs to go through an adjustable delay time, the delay time can be set to 20s-5min, set by the local power grid dispatching organization.

4.5 Electric Energy Measurement

4.5.1

Before the photovoltaic power generation system is connected to the power grid, the on-grid power quantity and the metering point of the grid power quantity should be specified. The power measurement point of the photovoltaic power generation system shall be located at the property right boundary between the photovoltaic power generation system and the power grid, and the property right boundary shall be determined according to the relevant regulations of the State. The on-grid electricity should be measured independently, and the configuration and technical requirements of the energy metering device installed at the metering point should meet the relevant requirements of DL/T 448.

4.5.2

The power metering device shall adopt a single-phase (three-phase) power meter with an accuracy of no less than 0.5S for active power and 2.0 for reactive power. At the same time, it shall have the functions of current, voltage, quantity and other information collection and three-phase current unbalance monitoring. It shall be equipped with a standard communication interface, capable of local communication and remote communication through the power information collection terminal. The energy meter communication protocol conforms to DL/T 645. The collection information of electricity meters shall be connected to the collection system of electricity consumption information of power users of the administrative department of the power grid and used as the basis for electricity energy measurement and price subsidies.

4.6 Communication

4.6.1

Information security protection measures should be taken: the collection and transmission of grid-connected operation information should meet the requirements of the State Electricity Regulatory Commission Decree No. 5 and other relevant system standards. It is advisable to upload information such as power generation, current, voltage, and power.

4.6.2

Electricity meters should be equipped with electricity information collection terminals, which can be connected to the existing collection system to realize remote transmission of electricity information to relevant departments.

4.7 Power factor adjustment

The power factor of photovoltaic power generation system should be adjustable from 0.95 ahead to 0.95 behind.

4.8 Security Identifier

The connecting points of photovoltaic power generation system should be marked conspicuously. Signs should indicate "warning" and other suggestive words and symbols. The shape of the sign,

Color, size and height shall comply with GB 2894.

5 Requirements for grid-connected equipment

5.1 Inverter Connection Requirements

The photovoltaic inverters used in the photovoltaic power generation system shall pass the testing or certification of the competent institutions and meet the requirements specified in NB/T 32004 and NB/T 42142.

5.2 Adding Cages to the System

5.2.1 Requirements for grid-connected interface Circuit breakers

5.2.1.1 A circuit breaker that is easy to operate, has clear breaking indication and is capable of breaking fault current shall be installed in the parallel cages.

5.2.1.2 The circuit breaker must have quick short-circuit break, remote trip, and meet the requirements of GB/T 14048.2 and GB/T 10963.1.

5.2.1.3 You are advised to use a circuit breaker that has the power and load terminal reverse connection capability. If a circuit breaker that does not have the power terminal reverse connection capability is used, the power terminal should be connected to the power grid side.

5.2.1.4 Miniature or plastic-case circuit breakers should be used.

5.2.1.5 The breaking capacity of the circuit breaker should be selected based on the level of short circuit current at the grid-connected interface with a certain margin.

5.2.2 Requirements for over and under voltage protection and automatic reclosing

And the cage should be installed with over and under voltage protection equipment, which has the function of loss of voltage trip, undervoltage trip, over voltage trip and voltage closing. The loss of voltage trip setting should be set at 20%Un, undervoltage trip setting should be set at 20%Un ~ 70%Un, over voltage trip setting should be set at 135%Un, trip should be in 1s action, The detected voltage setting value should be set to more than 85%Un, and the detected voltage closing should be operated within 10s ~ 60s.

5.2.3 Requirements on Lightning Protection and Surge Protection

5.2.3.1 A surge protection device must be installed inside the cage to protect the load device from the surge overvoltage. The specific model shall be determined according to the site conditions.

5.2.3.2 A circuit breaker or fuse should be installed before a surge protector whose breaking capacity must be greater than the maximum short circuit current.

5.2.4 Requirements for Obvious Disconnect Points

The photovoltaic power generation system should be installed on the grid-connected bus, which is easy to operate, suitable for mechanical locking and has an obvious disconnect point.

To ensure the safety of power facilities maintenance personnel.

5.2.5 Grounding Requirements

The surge protection devices must be grounded properly, and the grounding resistance must meet the requirements of GB 50065 and GB50057.

6 Grid-connected access mode

6.1 Overview

According to the different consumption modes of the photovoltaic power generation system, the photovoltaic power generation system can be connected to the distribution network in three ways: full access to the grid, self-generated and self-used surplus power to the grid, and all self-used.

(Press: 220V grid-connected <8kw,380v grid-connected <400kw>http://linkqi.cn)

6.2 Full Internet Access

In this access mode, all the electricity generated by the photovoltaic power generation system is countercurrent to the public grid. The power generation of photovoltaic power generation system and the power consumption of users are measured separately. The full access mode shall comply with the requirements in Figure 1. See Appendix A for the description of network points and common connection points.

wps1.jpg

Figure 1. Schematic diagram of full Internet access

6.3 Connecting to the Internet for Self-use and Surplus power

In this access mode, the electricity generated by the photovoltaic power generation system is preferentially supplied to the power load, and the remaining electricity is countercurrent to the public grid.

Countercurrent electricity and user electricity consumption are measured by bidirectional smart meters. The network access modes of self-use and surplus power should meet the requirements in Figure 2. For details about the network points and common connection points, see Appendix A.

wps1.jpg

Figure 2. Schematic diagram of network access for self-use and surplus power

6.4 All for personal use

In this access mode, all the electricity generated by the photovoltaic system is consumed by the user's electricity load, and the power shortage is supplemented by the public grid. The PV system has no electricity flowing upstream into the public grid. All self-use access modes shall comply with the requirements in Figure 3, and the description of network points and common connection points is shown in Appendix A.

wps3.jpg

Figure 3.