Common Mode EMI Research Articles

Modeling and Analysis of New Multilevel Inverter for Solar Photovoltaic Power Plant

Solar photovoltaic (PV) power plant is an effective way to utilize the renewable energy sources. EMI is one of the major concerns in PV power plant. Typically, the multilevel inverters are used in high voltage PV power plant. However, the conventional multilevel inverters require more semiconductors, which complicate the circuit structure and control algorithm. In this paper, a novel five-level inverter is introduced for the high voltage PV power plant applications. The model of the inverter is analyzed. With the redundant switching states, a new modulation strategy is proposed to reduce the common-mode voltage and EMI. The proposed approach is able to eliminate the common-mode voltage; meanwhile it has the capability of balancing the capacitor voltages. The cosimulation tests with the Matlab/Simulink and S-function are carried out. The results verify the effectiveness of the proposed method.

Shielding-Cancelation Technique for Suppressing Common-Mode EMI in Isolated Power Converters

In an isolated power converter, the interwinding capacitance of the transformer is the critical coupling path for the generating of common-mode (CM) noise. The shielding technique, for the purpose of blocking the electric coupling between the adjacent windings, has been widely used to deal with the CM noise. For the transformer with a single shielding layer, the displacement current that flows between the shielding layer and its adjacent windings still causes CM noise. In this paper, the shielding-cancelation (SC) technique is proposed by combining the shielding technique and the winding cancelation method together: The shielding layer is adjusted to have the same turns number and winding direction with its adjacent windings. In this way, the $dv/dt$ on the interwinding capacitance is always zero; thus, the CM noise can be effectively suppressed. A flyback converter prototype is built in the laboratory, and the performance of the SC technique on suppressing the CM noise is verified by experiments.

Erratum to “On Common-Mode and RF EMI in a Low-Voltage DC Distribution Network” [Sep 14 2583-2592

Regretfully, in the above paper [ibid., vol. 5, no. 5, pp. 2583-2592, Sep. 2014], there were in-text errors referring to color in black and white figures. The corrected text is presented here.

High frequency current probes for common-mode impedance measurements of power converters under operating conditions

Two current probes are designed with the appropriate magnetic material in order to make impedance measurements in High Frequency (HF) using the Current Injection Method (CIM). These probes are then used to measure the common-mode impedance of power converters in real-operating conditions. The characterization of this impedance is required for a correct EMI filter design. In this paper, a simple formulation of the probe transfer impedance, based on S-parameters, is proposed. These probes allow improving the accuracy of impedance measurements in a wide frequency range, up to 100 MHz. The measured impedances of the power converter are then applied in the design of the common mode EMI filter under real operation conditions. The obtained insertion losses of the filter are finally compared with those measured under 50 Ω – 50 Ω.

EMI Reduction in DC-Fed Electric Drives by Active Common-Mode Compensator

A novel common-mode (CM) EMI active filter for dc-fed motor drives is proposed. The active filter performs both the compensation of the CM voltage at the motor input and the mitigation of the leakage high-frequency CM currents, thus increasing the drive reliability and the vehicle electromagnetic compatibility (EMC). The filter scheme is based on a voltage feedback action and also includes a feed-forward action by exploiting a suitably estimated CM current. An optimized design of the CM voltage detection/injection systems is implemented. Moreover, the active filter is supplied by a smaller voltage than the dc link value; this permits a more performing amplifier to be used. The active filter behavior is analyzed theoretically and its performance is assessed by experiments. The realized prototype shows a good efficiency and compactness.

Operational Amplier Gain-Bandwidth Product Enhancement Technique for Common-mode Active EMI Filter Compensation Circuits

In this paper, the operational amplier (op-amp) gain-bandwidth product (GBP) enhancement technique for common-mode (CM) active EMI lter compensation circuits is proposed. To evaluate the proposed concept, the CM reduction performance of active EMI lters with: voltage canceling, current canceling, and closed-loop techniques, is chosen to be veried. The design procedures of enhanced op-amp GBP of CM active EMI lters are also provided. Finally, the CM reduction performances of the proposed approach are compared and veried experimentally. From the experimental results, it can be concluded that the proposed approach can improve the CM reduction performance of conventional active EMI lters from about 5 dBuV up to 20 dBuV at a certain frequency range.

Low-Common Mode Voltage H-Bridge Converter with Additional Switch Legs

H-bridge converter with additional switch legs (HA converter) and its offspring circuit are proposed in this paper with the intent to reduce the common mode noise. The proposed topology connects grounds of the input and output terminals, which gives zero common mode current in the ideal case. The operation of the proposed circuit is flexible and allows for the circuit to be capable of both ac–dc and dc–ac conversions. The proposed topology is especially advantageous when it is applied to the photovoltaic power conditioning system in dc distribution system or stand-alone power system because they include large stray capacitances and are prone to common mode EMI. In this paper, a 4-switch HA (HA4S) converter for both ac–dc rectification and dc–ac inversion is derived from the proposed HA converter as the implementation example. The experimental results based on the proposed and the conventional prototype circuits prove that the HA4S converter outperforms the conventional counterparts.

The TAIPEI Rectifier—A New Three-Phase Two-Switch ZVS PFC DCM Boost Rectifier

A new, three-phase, two-switch, power-factor-correction (PFC) rectifier that can achieve less than 5% input-current total harmonic distortion (THD) and features zero-voltage switching (ZVS) of all the switches over the entire input-voltage and load ranges is introduced. The proposed rectifier also offers automatic voltage balancing across the two output capacitors connected in series, which makes it possible to use downstream converters designed with lower voltage-rated component that offer better performance and are less expensive than their high-voltage-rated counterparts. In addition, the proposed rectifier also exhibits low common-mode EMI noise. The performance of the proposed rectifier was evaluated on a 2.8-kW prototype with a 780-V output that was designed to operate in 340-520-VL-L, RMS input-voltage range.

An Embedded Common-Mode Suppression Filter for GHz Differential Signals Using Periodic Defected Ground Plane

A novel low-cost filter design for common-mode noise suppression in high-speed differential signals is proposed. It is realized by periodically etching the dumbbell-shape defected ground structure (DGS) to perturb the return current of the common- mode noise. A transmission-line model for the proposed structure is also developed with good agreement to the full-wave simulation and measurement result. It is found that over 20 dB suppression of common-mode noise can be achieved over a wide frequency range from 3.3 to 5.7 GHz with 3 cascaded DGS cells, while the differential signals still keep good signal integrity in eye-pattern observation. The common-mode current, which generally results in common-mode EMI, on the attached input/output cable is also proved to be efficiently suppressed (15 dB in average) within the stopband by the proposed filter.