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Conducted Emission of Photovoltaic Grid-Connected Inverter-Technical Requirements for Artificial Power Network

Release time:

2023-08-03 15:43

Source:

　　1. Preface

The rapid development and prominent market position of domestic photovoltaic inverter manufacturers have brought significant synergy to the development of my country's photovoltaic inverter industry. Local manufacturers, mainly Huawei and Sungrow, have continued to make breakthroughs in the photovoltaic inverter market. It has been sold in batches to more than 150 countries and regions such as Germany, Italy, Australia, the United States, Japan, and India. With the growth of photovoltaic installed capacity, China's local manufacturers to speed up technology and product upgrades, and gradually narrow the distance between international manufacturers, domestic manufacturers of photovoltaic inverter market share gradually increased, it is expected that the future of China's manufacturers will continue to accelerate to the international market layout penetration.

With the rapid development of domestic photovoltaic inverter manufacturers, the share of export volume is gradually increasing, and the product quality requirements will be higher and higher. The photovoltaic inverter-related testing industry must also continuously improve its own testing capabilities and testing levels to protect the quality of Chinese products. escort.

This article focuses on the domestic and EU EMC certification standards for photovoltaic grid-connected inverters and the technical requirements for conductive emission artificial power supply networks.

　　2. Domestic and EU photovoltaic grid-connected inverter EMC standard

2.1 domestic EMC standards

At present, the main industry standard of domestic photovoltaic grid-connected inverter is NB/T32004-2018 "Technical Specification for Photovoltaic Grid-connected Inverter"

Scope of application: The standard is applicable to photovoltaic grid-connected inverters connected to PV source circuit voltage not exceeding 1500V DC and AC output voltage not exceeding 1000V. The pre-installed photovoltaic grid-connected inverter device with integrated step-up transformer connected to the power grid with voltage level of 35kV and below can be implemented by reference.

Inverter classification: according to the access voltage level is divided into class a inverter and class B inverter,

Class A: refers to photovoltaic inverters used in photovoltaic power stations connected to the grid through voltage levels of 35kV and above, or connected to the public grid through voltage levels of 10kV and above.

Class B: refers to the photovoltaic inverter used in the photovoltaic power generation system connected to the power grid through 380V voltage level and connected to the user side of the power grid through 10kV and below voltage level.

Conduction Emissions of Class B Inverter (DC Power Port Limits) See Figure 1

Figure 1 NB/T32004-2018 Class B Inverter Conducted Emission-DC Port Limits

2.2 EU EMC standards

China's photovoltaic inverter is mainly used for export, due to the differences in the world grid system and grid policy differences, resulting in photovoltaic grid-connected inverter test certification involves many standards, in the world has not yet formed an authoritative and unified certification standards.

The European Union has not yet separately regulated the EMC certification requirements for photovoltaic grid-connected inverter equipment, so the testing standards for photovoltaic grid-connected inverter equipment exported to the European Union are all general standards.

EU photovoltaic grid-connected inverter EMC certification standards (see Figure 2):

Figure 2 EU photovoltaic grid-connected inverter EMC certification standards

EN/IEC 61000-6-3 Conducted Emission-DC Port Limits (see Figure 3)

Figure 3 EN/IEC 61000-6-3 Conducted Emission-DC Port Limits

3. Introduction to Conducted Emission-Artificial Power Network

Technical requirements of EMC standard for 3.1 DC port artificial power network

Photovoltaic grid-connected inverter conduction emission test port: DC input port, AC output port and telecommunications, network port. This article mainly introduces the DC input port, as shown in the red line part of Table 3: The technical parameters of the DC artificial power supply network are shown in Chapter 4.7 of the CISPR16-1-2 (see Figure 4)

Fig. 4 CISPR 16-1-2 4.7 Chapter-Technical Parameters of DC Artificial Power Network

3.2 PVDC8301 DC artificial power network

3.2.1 Design principle

Figure 5 PVDC8301 DC artificial power supply network

The circuit of the photovoltaic inverter may generate ripple current on the DC side of the inverter. Most of these ripple currents are proportional to the power frequency and can be radiated as magnetic fields through cables and photovoltaic power generation modules, and may cause significant interference.

The PVDC8301 is specially designed for measuring various interference voltages on the DC side of the photovoltaic inverter (see Figure 6 for the schematic diagram). Three interference test modes are provided as follows:

① Mode A or B: Measure the common-mode interference voltage (asymmetric interference voltage) of a conductor at port "A" or "B" to reference ground.

② Common mode (CM): Measure the common mode interference voltage (asymmetric interference voltage) of a pair of conductors at ports "A" and "B" to the reference ground.

③ Differential mode (DM): Measure the differential mode interference voltage (symmetrical interference voltage) between the two conductors of port "A" and "B"

Fig.6 Schematic diagram of PVDC8301 DC artificial power supply network

3.2.2 Main technical indicators:

Frequency range: 150kHz - 30MHz

Maximum continuous current: 200 A (fan on)

Maximum short-time current: 250A(15 minutes)

Maximum voltage (DC):1500V

Common mode impedance:(150 /-30) Ω (switch position: CM,A,B)

Differential mode impedance:(150 /-30) (switch position: DM)

Phase:(0 /-40)°

Insertion loss:>20dB

Longitudinal conversion loss:>26dB

Divider coefficient: typical value 20 ( /-3) dB (10:1)

EUT connectors: airfoil terminals

Weight: about 30kg

Dimensions (chassis width x height x depth):448 x 295 x 600mm

The PVDC8301 DC artificial power supply network produced by SCHWARZBECK manufacturers can fully meet the requirements of Figure 3 :EN/IEC 61000-6-3 conducted emission test and Figure 4:CISPR 16-1-2 4.7 chapter manual power supply network technical parameters.

3.2.3 Difference between DC and AC port artificial power network

Photovoltaic grid-connected inverter AC output conduction emission test, the market mainly uses the NNLK8129 V-AMN artificial power supply network produced by SCHWARZBECK manufacturers.

Figure 7 NNLK8129

The differences are as follows:

① Different test voltage ports: NNLK8129 test AC port, PVDC8301 test DC port

② Different impedance: NNLK8129 impedance is 50Ω,PVDC8301 impedance is 150Ω

③ Different interference modes: NNLK8129 can only test the common mode interference voltage (asymmetric interference voltage) of one conductor to the reference ground, PVDC8301 can test three interference modes.

4. Photovoltaic grid-connected inverter EMC laboratory conducted emission test

Figure 8 Century Huize EMC Laboratory conducted emission layout of photovoltaic grid-connected inverter

Century Huize (Suzhou) Testing Technology Co., Ltd. can meet the testing requirements of grid-connected or off-grid photovoltaic inverters below 200kW. For the testing requirements that the output voltage of high-power photovoltaic grid-connected inverters can reach up to 800V, our company uses transformers to convert the output voltage of photovoltaic inverters into grid voltage to complete grid connection.

It has DC1500V and 210kW bidirectional DC power supply, dedicated PVDC8301 for conduction and emission DC port of photovoltaic inverter and artificial power supply network NNLK8129 AC port, which can meet the test requirements of domestic and international standards for photovoltaic inverters.

I hope everyone can basically understand the domestic and EU EMC certification standards and conducted emission test equipment for photovoltaic grid-connected inverters through this article.

Century Wisdom (Suzhou) Testing Technology Co., Ltd

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