GB/T 29319-2024Technical requirements for connecting photovoltaic power system to distribution network (English PDF)

1 Scope

The document lays down the technical requirements for active power, reactive power and voltage, fault ride-through, operational adaptability, power quality, starting and stopping, relay protection, power forecasting, electrical energy metering, communication and information, and simulation model and parameters where a photovoltaic power system is connected to a distribution network, together with the content of grid connection testing and evaluation.

It applies to the connection, commissioning and operation of new, rebuilt and extended photovoltaic power systems connected three-phase at a voltage level of 10 kV and below. Photovoltaic power systems fitted with energy storage may follow it for reference.

2 Normative references

The national standards cited are GB/T 12325 on supply voltage deviation, GB/T 12326 on voltage fluctuation and flicker, GB/T 13955 on the installation and operation of residual current operated protective devices, GB/T 14285 on relay protection and automatic safety devices, GB/T 14549 on harmonics in public supply networks, GB/T 15543 on three-phase voltage unbalance, GB/T 15945 on power system frequency deviation, GB/T 17215.321 on static meters for active energy of classes A, B, C, D and E, GB/T 19862 on general requirements for power quality monitoring equipment, GB/T 24337 on interharmonics in public supply networks, GB/T 32826 on modelling of photovoltaic power systems, GB/T 32892 on models and parameter testing of photovoltaic power systems, GB/T 33982 on relay protection for distributed resources connected to the grid, and GB/T 40595 on primary frequency regulation of grid-connected power sources.

The power industry standards cited are DL/T 448 on the technical management of electrical energy metering devices, DL/T 614 on multi-function watt-hour meters, DL/T 634.5101 and DL/T 634.5104 on telecontrol equipment and systems transmission protocols, DL/T 645 on the communication protocol of multi-function watt-hour meters, and DL/T 698.45 on the object-oriented data exchange protocol of electrical energy information acquisition and management systems.

3 Terms and definitions

The terms and definitions given in GB/T 12325 and GB/T 40595 apply, together with the following.

3.1 photovoltaic (PV) power generation system: a power generation system that converts solar radiant energy into electrical energy through the photovoltaic effect of solar cells.

3.2 point of common coupling: the point at which the photovoltaic power system connects to the public supply network.

3.3 point of connection: for a photovoltaic power system with a step-up station, the high voltage side busbar or node of that station; for one without, the output collecting point of the photovoltaic power system. A note refers to Annex A for illustrations of the point of connection and the point of common coupling.

3.4 response time: in a control process, the time from receipt of a control instruction or detection of the change in the state quantity that triggers the control action until the actual output of the observed variable first reaches 90 % of the difference between the control target value and the initial value. The source is given as GB/T 40289-2021, 3.13.

4 Active power

4.1 Active power control. A photovoltaic power system connected at the 10(6) kV voltage level shall be able to receive and execute active power control instructions automatically, with a control error whose absolute value is not greater than 1 % of the rated active power and a response time not greater than 5 s. A photovoltaic power system connected at the 380 V voltage level shall be able to receive and execute active power control instructions automatically.

4.2 Primary frequency regulation. A photovoltaic power system connected at the 10(6) kV voltage level shall have primary frequency regulation capability. Where the power system frequency deviation goes outside the primary frequency regulation dead band, the change in active power is calculated by formula (1), whose legend gives delta Pt as the change in active power of the photovoltaic power system in megawatts (MW), kf as the active frequency regulation coefficient, ft as the power system frequency in hertz (Hz), fN as the rated power system frequency in hertz (Hz), and PN as the rated active power of the photovoltaic power system in megawatts (MW).

The active frequency regulation coefficient and the dead band are fixed by the power system dispatching body according to the frequency regulation characteristics of the power system connected to, the coefficient preferably taking a value from 10 to 50 and the dead band preferably +/- 0.02 Hz to 0.06 Hz. Where the power system frequency is above 50 Hz, the limiting amplitude by which the photovoltaic power system reduces active power should be not less than 10 % of rated active power. Where the power system frequency is below 50 Hz, a photovoltaic power system fitted with energy storage shall increase active power, the limiting amplitude of the increase being preferably not less than 6 % of rated active power. The lag time of the primary frequency regulation response shall be not greater than 1 s, the response time not greater than 5 s and the settling time not greater than 15 s, and the active power regulation deviation once primary frequency regulation is steady shall not exceed +/- 1 % of rated active power.

5 Reactive power and voltage

The reactive output range of the photovoltaic inverter shall be dynamically adjustable within the rectangle shown in Figure 1, whose key gives P as the per unit active power of the photovoltaic inverter and Q as its per unit reactive power. The figure itself is a diagram and its coordinates are not reproduced in the extracted text.

The photovoltaic power system shall have several reactive power control modes, among them reactive voltage control, constant power factor control and constant reactive power control. It shall be able to take part in regulating the voltage at the point of connection, preferably by adjusting its own reactive power and active power. The power factor at the point of connection shall be continuously adjustable within the range 0.95 leading to 0.95 lagging.

6 Fault ride-through

6.1 Low voltage ride-through. Where a power system fault causes the voltage at the point of connection to dip, the photovoltaic power system shall have the low voltage ride-through capability of Figure 2: where the voltage dips to zero it shall run on without disconnection for 150 ms; where it dips to 20 % of nominal voltage it shall run on for 625 ms; and where it dips to between 20 % and 85 % of nominal voltage it shall run on within the shaded area of Figure 2. Table 1 gives the assessment voltage for low voltage ride-through under different fault types in three rows: for a three-phase short circuit fault, the line voltage at the point of connection; for a two-phase short circuit fault, the line voltage at the point of connection; and for a single-phase earth short circuit fault, the phase voltage at the point of connection.

A photovoltaic power system connected at the 10(6) kV voltage level shall have dynamic reactive support capability during low voltage ride-through. For a symmetrical fault, where the voltage at the point of connection falls below 85 % of nominal voltage the reactive current injected into the network shall be the sum of the reactive current output I0 in normal operation before the dip and the dynamic reactive current increment delta It, the increment being calculated by formula (2), whose legend gives delta It as the injected dynamic reactive current increment in amperes (A), K1 as the dynamic reactive current proportional coefficient, Ut as the per unit voltage at the point of connection and IN as the rated current of the photovoltaic power system in amperes (A). The coefficient K1 may be fixed according to the actual condition of the power system and should take a value from 1.5 to 3. The rise time of the dynamic reactive current shall be not greater than 30 ms. During the voltage dip the greatest reactive current output shall be not less than 1.1 times the rated current of the photovoltaic power system. From the moment the voltage at the point of connection recovers to 85 % of nominal voltage, the system shall withdraw the dynamic reactive current increment within 30 ms.

For an unsymmetrical fault, where the positive sequence component of the voltage at the point of connection lies between 60 % and 85 % of nominal voltage, the positive sequence reactive current injected into the network shall be the sum of the positive sequence reactive current output before the dip and the positive sequence dynamic reactive current increment, and the negative sequence reactive current drawn from the network shall be the difference between the negative sequence reactive current output before the dip and the negative sequence dynamic reactive current increment; the two increments are calculated by formula (3), whose legend gives the injected positive sequence dynamic reactive current increment and the absorbed negative sequence dynamic reactive current increment in amperes (A), the dynamic positive sequence and negative sequence reactive current proportional coefficients, the per unit positive sequence and negative sequence voltage components at the point of connection, and IN as the rated current of the photovoltaic power system in amperes (A). The two proportional coefficients may be fixed according to the actual condition of the power system and should be not less than 1.0. The rise time of the dynamic reactive current shall be not greater than 30 ms, and during the dip the greatest reactive current output shall be not less than 1.1 times the rated current. Where the positive sequence voltage component at the point of connection falls below 60 % of nominal voltage, the photovoltaic power system should inject positive sequence dynamic reactive current into the network and draw negative sequence dynamic reactive current from it, according to the actual control capability of the photovoltaic inverter and the dynamic reactive compensation device and the network conditions at the point of connection, and without aggravating the voltage unbalance at the point of connection.

A photovoltaic power system connected at the 380 V voltage level shall not reduce active current during low voltage ride-through. Where a photovoltaic power system has not disconnected during low voltage ride-through, its active power shall recover quickly once the fault is cleared, the rate of recovery preferably being not less than 30 % of installed capacity per second.

6.2 High voltage ride-through. Where a power system fault causes the voltage at the point of connection to rise, the photovoltaic power system shall have the high voltage ride-through capability of Figure 3: where the voltage rises to between 125 % and 130 % of nominal voltage it shall run on without disconnection for 500 ms; where it rises to between 120 % and 125 % it shall run on for 1 s; and where it rises to between 110 % and 120 % it shall run on for 10 s. A photovoltaic power system connected at the 10(6) kV voltage level shall have dynamic reactive support capability during high voltage ride-through: where the voltage at the point of connection lies between 110 % and 130 % of nominal voltage, the reactive current injected into the network shall be the difference between the reactive current output I0 in normal operation before the rise and the dynamic reactive current increment delta It, the increment being calculated by formula (4), whose legend gives delta It as the injected dynamic reactive current increment in amperes (A), K3 as the dynamic reactive current proportional coefficient, Ut as the per unit voltage at the point of connection and IN as the rated current of the photovoltaic power system in amperes (A). The coefficient K3 may be fixed according to the actual condition of the power system and should be not less than 1.5. The rise time of the dynamic reactive current shall be not greater than 30 ms. During the voltage rise the greatest reactive current output shall be not less than 1.1 times the rated current. From the moment the voltage recovers to 110 % of nominal voltage, the system shall withdraw the dynamic reactive current increment within 30 ms.

6.3 Consecutive low voltage ride-through. The photovoltaic power system shall be able to withstand at least two consecutive low voltage ride-through events; the interval between two adjacent events may be fixed according to the reclosing time of the outgoing line and of the power system connected to, and should take a value from 0.2 s to 2 s. The response characteristics and support capability of each low voltage ride-through shall meet 6.1.

7 Operational adaptability

7.1 Voltage adaptability. Where the voltage at the point of connection lies between 85 % and 110 % of nominal voltage, the photovoltaic power system shall be able to run on normally and continuously. Where it falls below 85 % or exceeds 110 % of nominal voltage, the system shall meet 6.1 and 6.2.

7.2 Frequency adaptability. The frequency adaptability of the photovoltaic power system shall meet Table 2, which sets a running requirement against each power system frequency range. Below 46.5 Hz the requirement depends on the lowest frequency at which the photovoltaic power system and the reactive compensation device are allowed to run. From 46.5 Hz up to 47 Hz, the system shall be able to run for at least 5 s each time the frequency falls below 47.0 Hz and stays above 46.5 Hz. From 47.0 Hz up to 47.5 Hz, at least 20 s each time the frequency falls below 47.5 Hz and stays above 47 Hz. From 47.5 Hz up to 48.0 Hz, at least 60 s each time the frequency falls below 48 Hz and stays above 47.5 Hz. From 48.0 Hz up to 48.5 Hz, at least 5 min each time the frequency falls below 48.5 Hz. From 48.5 Hz to 50.5 Hz inclusive, continuous running. Above 50.5 Hz up to 51.0 Hz, at least 3 min each time the frequency rises above 50.5 Hz and stays below 51 Hz, with a system connected at the 10(6) kV voltage level able to execute a power reduction instruction from the power system dispatching body, and photovoltaic power systems in a stopped state not allowed to connect. Above 51.0 Hz up to 51.5 Hz, at least 30 s each time the frequency rises above 51.0 Hz and stays below 51.5 Hz, with the same dispatch and no-connection provisions. Above 51.5 Hz the requirement depends on the highest frequency at which the photovoltaic inverter and the reactive compensation device within the system are allowed to run.

The photovoltaic power system shall run on without disconnection within the following ranges of rate of change of frequency: within a 0.5 s sliding window, an absolute rate of change not greater than 2 Hz/s; within a 1 s sliding window, not greater than 1.5 Hz/s; and within a 2 s sliding window, not greater than 1.25 Hz/s. The relation between sliding window and rate of change of frequency is shown in Figure 4.

7.3 Power quality adaptability. Where the voltage fluctuation and flicker at the point of connection meet GB/T 12326, the harmonics meet GB/T 14549, the interharmonics meet GB/T 24337 and the three-phase voltage unbalance meets GB/T 15543, the photovoltaic power system shall be able to run normally.

8 Power quality

8.1 The voltage deviation caused at the point of common coupling by the connection of the photovoltaic power system shall meet GB/T 12325.

8.2 The voltage fluctuation and flicker caused at the point of common coupling shall meet GB/T 12326.

8.3 The harmonic current injected by the photovoltaic power system into the point of common coupling shall meet GB/T 14549, the permissible harmonic current injected by the system at its point of connection being apportioned by the ratio of the installed capacity of the photovoltaic power system to the total capacity of generating and supply equipment with a harmonic source at that point of common coupling. Interharmonics caused at the point of common coupling shall meet GB/T 24337.

8.4 The voltage unbalance caused at the point of common coupling shall meet GB/T 15543.

8.5 The direct current component injected into the point of common coupling shall not exceed 0.5 % of the alternating current rated power of the system.

8.6 Monitoring and mitigation. The point of common coupling of a photovoltaic power system connected at the 10(6) kV voltage level shall be fitted with a class A on-line power quality monitoring device meeting GB/T 19862, and the monitoring data kept for at least one year. The point of common coupling of a system connected at the 380 V voltage level should be fitted with an on-line power quality monitoring device meeting GB/T 19862 or with equipment having an on-line power quality monitoring function, and the monitoring data kept for at least one year. Where the power quality indices of the photovoltaic power system fail to meet the requirements, power quality mitigation equipment shall be installed.

9 Starting and stopping

The change in power quality caused by starting and stopping the photovoltaic power system shall meet clause 8. The voltage and frequency at the point of connection on starting shall meet GB/T 12325 and GB/T 15945, failing which the system shall not start. A photovoltaic power system connected at the 10(6) kV voltage level shall reconnect only after receiving a connection instruction from the grid dispatching body.

10 Relay protection

10.1 General requirements. Protection of the photovoltaic power system shall be reliable, selective, sensitive and fast acting, and shall meet the relevant requirements of GB/T 14285 and GB/T 33982. A photovoltaic power system connected at the 10(6) kV voltage level shall have, at the point of connection, a switching device that is easy to operate, can be locked out, has a visible break, has an earthing function and can break fault current. A system connected at the 380 V voltage level shall have, at the point of connection, a switch that is easy to operate, has a visible break indication and can break fault current.

10.2 Line protection. For a photovoltaic power system connected at the 10(6) kV voltage level, current protection may be used at both ends of the connecting line, with a directional element added where needed. Where the operating current setting and the time coordination cannot meet the requirements of reliability and selectivity, distance protection or longitudinal current differential protection should be used.

10.3 Under and over voltage protection of the photovoltaic power system shall meet 6.1 and 6.2.

10.4 Frequency protection of the photovoltaic power system shall meet 7.2.

10.5 Anti-islanding protection. A photovoltaic power system connected at the 10(6) kV voltage level shall be fitted with an independent anti-islanding protection device. A system connected at the 380 V voltage level may achieve anti-islanding protection either through an independent device or through the inverter. The operating time of anti-islanding protection shall be not greater than 2 s, and the protection shall coordinate with the line and automatic safety device protection on the network side. Anti-islanding protection shall coordinate with the fault ride-through requirements, fault ride-through taking priority over anti-islanding protection.

10.6 Residual current protection. The setting, operating current and breaking time of the residual current protection of a photovoltaic power system connected at the 380 V voltage level shall meet the relevant requirements of GB/T 13955.

11 Power forecasting

A photovoltaic power system connected at the 10(6) kV voltage level shall report medium term power forecasting data for 0 h to 240 h, short term data for 0 h to 72 h and ultra short term data for 15 min to 4 h. For short term forecasting made the day before, the monthly mean accuracy shall be not less than 85 % and the monthly mean qualification rate not less than 85 %; for ultra short term forecasting at the fourth hour, the monthly mean accuracy shall be not less than 90 % and the monthly mean qualification rate not less than 90 %.

12 Electrical energy metering

Before the photovoltaic power system is connected the metering points shall be fixed: a system that feeds all its output to the grid shall have a generation metering point at the property demarcation point, and a system for own use with surplus fed to the grid shall have metering points at the property demarcation point and at the photovoltaic point of connection. Each metering point shall carry one meter, the arrangement meeting DL/T 448.

The meter shall be a static multi-function meter whose technical performance meets GB/T 17215.321 and DL/T 614. It shall have at least bidirectional active energy metering, four quadrant reactive energy metering and event recording, carry a standard communication interface and be able to communicate locally or remotely. The meter communication protocol shall meet DL/T 645 or DL/T 698.45, and the data acquisition interval should be not greater than 15 min.

Before connection the electrical energy metering device shall have completed the relevant testing, installation and commissioning.

13 Communication and information

A photovoltaic power system connected at the 10(6) kV voltage level shall exchange data in both directions with the grid dispatching body, over a wireless private network, a wireless virtual private network or an optical fibre private network, the communication protocol conforming to DL/T 634.5104 and DL/T 634.5101. A system connected at the 380 V voltage level should use RS485, power line carrier, a public wireless network or a similar means. Where wireless communication is used, information and communication security measures shall be taken.

A photovoltaic power system connected at the 10(6) kV voltage level shall provide the following information in real time: analogue quantities, being the voltage, current, active power, reactive power and power factor at the point of connection; state quantities, being the running state of the inverter, the state of the switchgear and other equipment at the point of connection, faults and similar information; energy quantities, being generated energy, energy fed to the grid and energy taken from the grid; power regulation data, being the in-service or out-of-service state of active and reactive regulation, the upper and lower regulation limits, the reactive voltage control mode, and abnormality and alarm signals; power forecasting data; and power quality monitoring data.

A photovoltaic power system connected at the 380 V voltage level shall upload at least the current, voltage, active power, reactive power, generated energy and grid connection state at the point of connection, the data upload interval preferably being not lower than 15 min.

14 Simulation model and parameters

A photovoltaic power system connected at the 10(6) kV voltage level shall provide the transient models and parameters of the photovoltaic generating units, the reactive compensation device, the collection and step-up system and the control system. Those transient models shall meet GB/T 32826 and shall be validated by the method laid down in GB/T 32892. Such a system shall also provide a short circuit current calculation model. A photovoltaic power system connected at the 380 V voltage level shall provide the model, parameters and instruction manuals of the main equipment interfacing with the grid.

15 Grid connection testing and evaluation

Before the photovoltaic power system is connected to the grid, the type test reports of the photovoltaic inverter and other main equipment shall be reviewed. A system connected at the 10(6) kV voltage level shall provide a grid connection test report within six months of starting grid-connected operation. Where the photovoltaic inverter or other main equipment within the system is changed, an equipment test report shall be provided again.

Grid connection testing and evaluation shall cover at least active power control and primary frequency regulation testing, reactive voltage regulation capability testing, fault ride-through capability testing or evaluation, power quality testing, operational adaptability testing or evaluation, and safety and protection function testing.

Annex A Examples of the point of connection and the point of common coupling (informative)

A.1 The point of connection of a photovoltaic power system, shown in Figure A.1, is the point at which the system connects to a network, and that network may be either the public network or a user network.

A.2 The dashed box in Figure A.1 is the user network, which connects to the public network through the point of common coupling C. Within the user network are two photovoltaic power systems, connected to the user network at points A and B; A and B are both points of connection but neither is a point of common coupling. At point D a photovoltaic power system connects directly to the public network, and D is both a point of connection and a point of common coupling. The figure itself is a diagram and is not reproduced in the extracted text.