Complies with IEC 61000-4-13: Analysis of Harmonics, Interharmonics and Immunity to Grid Signals in AC Power Supply

Abstract

In modern power electronics environments, public power grids are no longer pure 50Hz or 60Hz sine waves. With the widespread adoption of switched-mode power supplies (SMPS), frequency converters, and grid-connected renewable energy equipment, the power grid is rife with various waveform distortions. IEC 61000-4-13 is a core international standard specifically for low-frequency immunity assessment of AC ports. This article will delve into the threats posed to equipment by harmonics, interharmonics, and grid signals, and analyze how engineers can utilize the Infineon Power RPS-5000 simulator, equipped with “four-quadrant simulation” and “energy recovery” capabilities, to accurately perform complex verifications required by regulations.

1. Physical Phenomenon Analysis: Who is Interfering with Your Power Grid?

IEC 61000-4-13 primarily defines and simulates three low-frequency physical phenomena that typically cause changes in waveform envelope, leading to instability in equipment operation:

Harmonics: Frequency multiples of the fundamental frequency (e.g., 180Hz/3rd, 300Hz/5th). These mainly originate from feedback generated by numerous nonlinear loads (e.g., LED drivers, computer power supplies) when discontinuously drawing current.

Interharmonics: Frequency components that are not integer multiples of the fundamental frequency. This type of interference is common in asynchronous motor drives, induction heating equipment, or photovoltaic (PV) inverters; its unpredictable frequency components are extremely difficult to completely filter out using conventional filters.

Mains Signaling: Specific superimposed signals (typically between 110Hz and 3kHz) used by power companies for remote equipment control or communication. Test equipment must verify whether the device under test (DUT) will mistake these signals for power interference, causing functional interruption.

2. Systemic Hazards: Why is “Compliance” the Cornerstone of Stability?

Power electronic products lacking immunity to IEC 61000-4-13, even if they operate at standard voltages, may still face the following high-cost risks in complex field environments:

Abnormal heat loss and shortened lifespan: The skin effect caused by high-order harmonics can lead to abnormal Joule heating in transformer coils, industrial motors, and power cables. Repeated transient interference can also cause cumulative stress on semiconductor components and electrolytic capacitors, resulting in a significant decrease in the product’s MTBF (Mean Time Between Failures).

Control logic failure: Severe waveform distortion can interfere with the circuit’s “zero-crossing detection.” This is fatal to SCR or microcontroller control systems that rely on precise phase control, potentially causing random MCU restarts, control logic shutdowns, or unstable outputs.

Communication interference and accidental activation protection: Strong interharmonics can overwhelm the effective signals of power line communication (PLC), and even cause malfunctions in leakage current devices (RCDs) or overcurrent protectors, leading to unexpected shutdowns.

3. Key Test Waveforms and Verification Objectives

To realistically reproduce imperfect power grid environments, IEC 61000-4-13 defines several highly challenging test waveforms:

Flat Curve: Simulates waveform clipping caused by excessive simultaneous charging of rectified loads in a power grid. This is used to verify the voltage sustaining capability and ripple suppression performance of the DC bus inside the device under test (EUT).

Over Swing: Simulates voltage overshoot waveforms generated when capacitors are switched or resonance occurs in a power system. This test directly challenges the insulation withstand capability of the equipment and the energy absorption limits of overvoltage protection components (such as varistors).

Frequency Sweep: Continuous spectrum injection in the range of 16Hz to 2.4kHz. This is equivalent to a “hearing test” of the product, designed to identify whether the internal filtering circuitry of the EUT generates destructive resonance at specific frequencies.

Meister Curve: Specifically used for immunity testing of master-side communication signals. The verification equipment maintains normal operation without misinterpretation when receiving communication commands from the power company.

4. Hardware Challenges of the Test Equipment: Key Technologies for Precision Simulation

According to regulations, AC power supply simulators performing this type of testing must overcome the following hardware hurdles:

Extremely Low Output Inductance: To simulate the transient switching of rapid voltage changes (1µs – 5µs), the output inductance of the test source must be below 100µH. Traditional power supplies, due to excessive inductive reactance, often cause distortion of the injected harmonic waveform, rendering the test results invalid.

Asynchronous Frequency Synthesis Capability: Interharmonics are not aligned with the fundamental frequency, requiring the equipment to have an independent digital signal processing (DSP) engine capable of simultaneously generating multiple asynchronous waveforms and perfectly superimposing them.

Four Quadrants and Back EMF Handling: When simulating a sudden voltage drop and the test object is an inductive load (such as a motor), the load will generate back electromotive force (Back EMF). If the test equipment does not have sink (energy absorption) capability, the output waveform will be severely distorted.

5. Infineon Power Solutions: RPS-5000 Ultimate Compliance Platform

The Infineon RPS-5000 series power supplies are designed to solve complex grid simulation needs, making them the perfect partner for your R&D and certification:

Comprehensive Software Support: Equipped with dedicated PowerVUE remote control software, it features built-in automatic test templates for IEC 61000-4-11, 13, 14, and 28 regulations. Engineers simply select the standard number, and the system automatically configures harmonic order, phase angle, and interharmonic frequency, significantly reducing development cycles.

SiC MOSFET Technology: Utilizing third-generation semiconductor technology, it achieves microsecond-level high slew rate, ensuring high realism in peak waveforms and switching transients.

Four-Quadrant Regenerative Function: The device boasts an energy feedback efficiency of over 90%. During high-power, long-duration burn-in tests or immunity tests, it can feed absorbed energy back to the grid, saving electricity costs and reducing laboratory ambient temperature.

Ultra-Low Voltage High Current Simulation: Supports maintaining high current output under extremely low voltage conditions, perfectly matching the dynamic testing scenarios of AI server power supplies (VRM/POL).

Conclusion

With the increasing popularity of “green energy grid connection” and “distributed power generation,” IEC 61000-4-13 verification has shifted from simply “obtaining certification” to “ensuring the survivability and competitiveness of products in harsh global power grids.” Through the high-precision simulation of the Infineon RPS-5000 series and the automated processes of PowerVUE, we not only assist you in obtaining market certification but also build a robust electrical immune system for your products, helping enterprises achieve stable, efficient, and sustainable development goals.