Robert Smoleński Institute of Electrical Engineering University of Zielona Gora Conducted Electromagnetic Interference in Smart Grids Introduction Currently there is lack of the strict, established definition of the Smart Grid, furthermore, Smart Grid concepts presented by the individual authorities in the field of power systems differ significantly. On the basis of the literature study, the Smart Grid can be described as the power system that in a detail perspective should posses specific possibilities and characteristics. The grid should allow integration of the bigger amount of the energy ergy from renewable energy sources. The typical feature of this system is a high quality of electric energy, elimination of higher harmonics, voltage dips, sags and interruptions, tions, asymmetry of phase voltages. End-users perform in Smart Grids an active role, they are both users and producers of electric energy (Smart Buildings, Smart Cities). Smart Grid has to be ready for new challenges such as, for instance, nce, development of electric vehicles market (V2G). OUTLINE Introduction Introduction Power Electronic Interfaces in Smart Grids Standardized measurements of conducted EMI Conducted EMI issues in Smart Grids Shaping of the EMI characteristics in Smart Grids Compensation of interference sources inside of the Power Electronic Conclusions Introduction Introduction
Average Detector Level [dbuv] 110 100 90 Drive 1 (Level dbuv) Drive 2 (Level dbuv) Drive 3 (Level dbuv) Max Min 75% 25% 50% Max Min 75% 50% 25% Max 75% 50% 25% Min Average Detector Level [dbuv] 110 100 90 Drive 1&2 (Level dbuv) Drive 2&3 (Level dbuv) Drive 1&3 (Level dbuv) Drive 1&2&3 (Level dbuv) Max Max 75% 75% 50% 50% 25% 25% Min Max Min 75% 50% 25% Max 75% 50% 25% Min Main EMC issues in systems containing ing Power Electronics Interfaces: Connection of high emission power electronic converters to susceptible control and monitoring equipment that might cause immunity problems Aggregation of interferences caused by group of converters Spread of interferences over wide circuits Min 80 Drive 1 Drive 2 Drive 3 80 Drive 1&2 Drive 2&3 Drive 1&3 Drive 1&2&3 a.) b.) Box charts: a.) for single dirives, b.) for groups of drives EMC of the Smart Grid is Important Issue President of the SC1 Magnus Olofsson Director-General Swedish National Electrical Safety Board Power Electronic Interfaces in Smart Grids EMI couplings: -inductive -capacitive -by common impedance Source: EMC compliance club
Phase voltages and common mode voltage at the output of the 3-phase 3 inverter Bearing race damages caused by EDM currents Standardized measurements of conducted EMI Phase voltage and common mode current Standardized measurements of conducted EMI Originally principles of electromagnetic compatibility focused on assurance of the proper RTV signal reception. Therefore the usage of equipment that during EMC test simulate a typical RTV receiver seemed to be appropriate approach. The standard describe responses of the receiver for the selected signals: sinusoidal (continuous wave) of determined amplitude A, pulse (pulse train of amplitude A, duration ti, pulse repetition rate fr), noise (normal distribution of amplitude probability). CM voltage U CM, shaft voltage and CM current I CM, time-expanded expanded scale shaft voltage U S and EDM E current I B Main circuit diagram of the 4-quadrant 4 inverter drive system
Standardized measurements of conducted EMI Standardized measurements of conducted EMI The EMI receiver has to meet standard requirements concerning especially: pulse response, selectivity (band pass in individual frequency ranges, attenuation of intermediate frequency signals, attenuation of mirror frequencies and other unwanted responses), intermodulation effects, limitation of noises and internal unwanted signals (internal noises, continuous wave signals), shielding IF BW filter Standardized measurements of conducted EMI Superheterodyne receiver The block diagram of the typical EMI receiver Resolution of the EMI reciver scan Standardized measurements of conducted EMI Standardized measurements of conducted EMI Differences between EMI receiver and digital oscilloscope!!! The functional blocks of the typical EMI receiver The peak detector offers fastest possible sweep due to shortest time constant of the RC circuit The usage of the peak detector sweep is fast and easy way to compare obtained results with limit lines during engineering test, because peak detector values are always higher or equal to average and quasi-peak detectors indication!!! Peak detector diagram
Standardized measurements of conducted EMI Standardized measurements of conducted EMI The quasi-peak detection mode rely on utilization of the integration circuit of two different time constants in order to evaluate so-called annoyance factor. The charge rate of the quasi-peak detector is much faster than the discharge rate, thus the higher the repetition rate of the signal, the higher the output of the quasi-peak detector. Quasi-peak detector diagram LISN (Line Impedance Stabilization Network ) Standardized measurements of conducted EMI Standardized measurements of conducted EMI For average detection the peak detected signal must pass through a filter with a bandwidth much less than the resolution bandwidth. The filter averages the higher frequency components, such as noise, at the output of the envelope detector. Average detector diagram LISN (Line Impedance Stabilization Network ) Standardized measurements of conducted EMI What is the conducted EMI? What is LISN developed for? Standardized measurements of conducted EMI LISN (Line Impedance Stabilization Network ) Flow of the measured interference currents
Standardized measurements of conducted EMI Conducted EMI issues in Smart Grids LISN (Line Impedance Stabilization Network ) Scheme of four-quadrant frequency converter with AC generator Standardized measurements of conducted EMI Conducted EMI issues in Smart Grids LISN (Line Impedance Stabilization Network ) Conducted EMI spectra in CISPR A and CISPR B frequency ranges Conducted EMI issues in Smart Grids Conducted EMI issues in Smart Grids Conducted EMI spectrum for CISPR A frequency range
Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Conducted EMI issues in Smart Grids a.) b.) c.) Conducted EMI spectrum (drive without filters): a.) in neutral, b.) load, c.) generator Phase voltages and CM voltage at the input terminals of the converter Conducted EMI issues in Smart Grids Conducted EMI issues in Smart Grids EMI spreading equivalent circuit Electric grid scheme with designated measuring points Conducted EMI issues in Smart Grids Conducted EMI issues in Smart Grids CM current on the line side of the converter: (a) expanded form, (b) wide range time scale Box-and and-whisker plot of quasi-peak detector measurements for: (a) interface turned off, (b) interface turned on
Conducted EMI issues in Smart Grids Spectra of current in PE wire of power cable at transformer terminal for: (a) switched off converter, (b) switched on converter MV and LV electric grid scheme with designated measuring points Spectra of current in PE wire: (a) near converter, (b) in transformer station for switched-on converter, (c) in transformer station for switched-off converter Magnetic field strength on both sides of power transformer: (a) low voltage side (point A), (b) medium voltage side (point B) B CM impedance module of YAKY 4x25mm2 cable: 2.5m, 5m and 10m long Magnetic field measurement under overhead MV line
Increase of interference caused by converter under MV overhead lines: l a) 20 m away from station, b) 1500 m away from station Passage of common mode currents through virtual grounding point Conducted EMI issues in Smart Grids Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Scheme of four-quadrant frequency converter with AC generator Spectrum of CM currents on line and motor side Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Experimental arrangement Four-quadrant drive with passive input filter
Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development High emission in HF range Passage of common mode currents through virtual grounding point in drive with passive input filter Spectrum of CM currents on line and motor side (drive with input passive filter) Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Conducted EMI spectrum (drive with passive input filter) Spectrum of CM currents on line and motor side (drive with input and output passive filter) Conducted EMI spectrum (drive without filters and drive with passive input filter) Passage of common mode currents through virtual grounding point in drive with input and output passive filter
Conducted EMI generated by 4-quadrant 4 frequency converters and EMI filters development Aggregated EMI generated by group of 2-quadrant 2 asynchronous drives Conducted emission in both CISPR A and CISPR B ranges (drive with input and output passive filter) Phase current and CM current Aggregated EMI generated by group of 2-quadrant 2 asynchronous drives Measuring circumstances!!! Energy-efficient efficient fluorescent lamps story!!! Arrangement for measurements of conducted EMI generated by a group of converters with deterministic and random modulations Phase current (i( f ) and CM current (i( CM ) Aggregated EMI generated by group of 2-quadrant 2 asynchronous drives Aggregated EMI generated by group of 2-quadrant 2 asynchronous drives Main oscillatory modes of CM current in motor PE wire Spectrum of CM current on the line side
Aggregated EMI generated by group of 2-quadrant 2 asynchronous drives Spectrograms for inverter switching frequency: a.) one converter, b.) two converters, c.) three converters Conducted EMI spectra (CISPR A) measured using peak and average detectors for converters with random modulation: a) R1, b) R2, c) R3, d) R1&R2, e) R1&R3, f) R2&R3 Aggregated EMI generated by group of 2-quadrant 2 asynchronous drives Average Detector Level [dbuv] 110 100 90 Drive 1 (Level dbuv) Drive 2 (Level dbuv) Drive 3 (Level dbuv) Max Min 75% 25% 50% Max Min 75% 50% 25% Max 75% 50% 25% Min Average Detector Level [dbuv] 110 100 90 Drive 1&2 (Level dbuv) Drive 2&3 (Level dbuv) Drive 1&3 (Level dbuv) Drive 1&2&3 (Level dbuv) Max Max 75% 75% 50% 50% 25% 25% Min Max Min 75% 50% 25% Max 75% 50% 25% Min Min 80 Drive 1 Drive 2 Drive 3 80 Drive 1&2 Drive 2&3 Drive 1&3 Drive 1&2&3 a.) b.) Box charts: a.) for single dirives, b.) for groups of drives Spectra of aggregated interference (CISPR A) generated by three converters, measured using peak and average detectors for: a) deterministic modulation b) random modulation Conducted EMI spectra (CISPR A) measured using peak and average detectors for converters with deterministic modulation: a) D1, b) D2, c) D3, d) D1&D2, e) D1&D3, f) D2&D3 Conducted EMI spectra (CISPR B) measured using peak and average detectors for converters with deterministic modulation: a) D1, b) D2, c) D3, d) D1&D2, e) D1&D3, f) D2&D3
Conducted EMI spectra measured using peak and average detectors for converters with random modulation: a) R1, b) R2, c) R3, d) R1&R2, e) R1&R3, f) R2&R3 DC/DC converter carrier based PWM, and interference currents Spectra of aggregated interference (CISPR B) generated by three converters, measured using peak and average detectors for: a) deterministic modulation b) random modulation DC/DC converter carrier based PWM, and interference currents Box-and-whisker plots of average detector measurements for various drive configurations with deterministic and random modulations and filter: (a) IF BW = 200 Hz, (b) IF BW=9kHz
The k-th harmonic of the total interference current generated by N converters can be expressed by: FFT of EMI current generated by DC/DC converters with deterministic tic modulation: a) single converter, b) three converters of the same switching frequency, c) three converters of slightly different switching frequency Construction of vector representing the k th harmonic of the sum of interference generated by three identical DC/DC converters FFT of EMI current generated by DC/DC converters with random modulation: a) single converter, b) three converters 3D density function describing probability of vector Zk placement for: 5, 15 and 30 convertersm of interference generated by three identical DC/DC converters Box-and-whisker plots of waiting times for critical transmission errors in a system with two operated converters with deterministic (D1&2) and random (R1&2) modulations
0,8 0,6 0,4 8 6 4 Current [A] 0,2 0-0,2 Voltage [V] 2 0-2 -0,4-0,6-0,8 0 2E-6 4E-6 6E-6 8E-6 1E-5 1,2E-5 1,4E-5 1,6E-5 1,8E-5 2E-5 Time [s] -4-6 -8 0 2E-6 4E-6 6E-6 8E-6 1E-5 1,2E-5 1,4E-5 1,6E-5 1,8E-5 2E-5 Time [s] Interference current and RS-232 voltage signal Source: EMC compliance club Cables as close as possible Cables 4 cm away from each other Electron microscope story Impedance module of parasitic couplings between two cables Source: EMC compliance club Capacitor impedance module: a.) 3,3 nf, b.) 100 nf 10000 Impedamce module [Ω] 1000 100 10 1 0 cm 1 cm 2 cm 3 cm Impedance module [Ω] 100 10 1 0,1 0 cm 1 cm 2 cm 3 cm 0,1 0,01 10k 100k 1M 10M 30M Frequency [Hz] 0,01 10k 100k 1M 10M Frequency [Hz] Source: EMC compliance club
CM voltage in neutral point (U N ), bearing voltage (U W ) and CM current (I CM ) in system without filters Inductance increase cause damping factor decrease!!! CM voltage in neutral point (U N ), bearing voltage (U W ) and CM current (I CM ) in system without filters CM voltage in neutral point (U N ), bearing voltage (U W ) and CM current (I CM ) in system with line reactors
CM voltage in neutral point (U N ), bearing voltage (U W ) and CM current (I CM ) in system with CM choke CM voltage in neutral point (U N ), bearing voltage (U W ) and CM current (I CM ) in system with CM transformer EMC of 2-quadrant 2 frequency converters and EMI filters Source: S. Ogasawara, H. Akagi, Modelling and Damping of High-Frequency Leakage Currents in PWM Inverter-Fed AC Motor Drive Systems, IEEE Trans. on Ind. Appl. 32, 1105-1113 (1996) Influence of passive filters on CM current shape and its RMS value Influence of passive filters on spectrum of CM current
Influence of passive filters on shaft voltages CM voltage at neutral point of the output of inverter U det and CM voltage at the output of emitter follower U D 3D distributions of EDM currents in drive with different passive filters Voltage drop on gate resistor!!! Drive system with series active filter CM voltage at neutral point of the output of inverter U det and CM voltage at the output of emitter follower U D
Common mode voltage and shaft voltage in drive with series active filter Phase voltages on the series connected inductors (L fcm and L fdm ) and compensating voltage U D Inverter-fed system with passive CM voltage filter arrangement Line to line voltages at the output of the filter for inverter output frequency f inv =25 Hz and f inv =50 Hz Phase voltages on the series connected inductors (L fcm and L fdm ) and compensating voltage U D CM voltage at neutral point of star-connected load in system: a) without filter, b) with filter
CM currents in drive: a) without filter, b) with passive CM voltage filter Phase voltages and CM voltages at the output of two-level inverter Compensated CM voltage ucm and magnetizing current im for various inverter output frequencies: a) f inv =50 Hz, b) f inv =25 Hz, c) f inv =0 Hz Phase voltages and CM voltages at the output of three-level inverter Compensated CM voltage ucm and magnetizing current im for various inverter output frequencies: a) f inv =50 Hz, b) f inv =25 Hz, c) f inv =0 Hz Phase voltages and CM voltages at the output of four-level inverter
Amplitude [%] Amplitude [%] Passive CM filter with sinusoidal line-to-line voltages and CM choke saturation problems Modulation effect CM voltage in two-, three- and four level inverters Compensated CM voltage and magnetizing current for inverter output frequency: 50 Hz, 25 Hz and 0 Hz 3D space vector representation of the switching states of a two- and three-level inverter Placement of triangular carrier functions for modulations: a) PD, b) APOD, c) POD Compensation conditions in multilevel inverters with carrier-based sinusoidal modulations Compensation conditions in multilevel inverters with carrier-based sinusoidal modulations Two-level Three-level 1 P( t) = 1 2 t 2 FP i N U CM = Frequency [Hz] 2 1 ( t) = P( t) + N i N 2 ( t) = 2 3N 1 N k= 1 i= 1 H Asin 2π finv t + 2 kπ 3 Modulation index Amplitude [%] i FPRN ( t) 1 Frequency [Hz] Frequency [Hz] Modulation index Modulation index Four-level Maximum time integral values vs. the inverter output frequencies and the modulation indexes 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0
Frequency [Hz] Compensation conditions in multilevel inverters with carrier-based sinusoidal modulations Compensation conditions in multilevel inverters with carrier-based sinusoidal modulations a) b) c) Lowest level CM voltage and time t integral of CM voltage produced, by five-level inverter in worst case : : a) PD modulation, b) APOD modulation, c) POD modulation Theoretical evaluation and numerical analyses Compensation conditions in multilevel inverters with carrier-based sinusoidal modulations Proposed method of function root approximation and relative r error for different root determination methods a) b) c) Lowest level CM voltage and time integral of CM voltage produced, by five-level inverter for M=1: a) PD modulation, b) APOD modulation, c) POD modulation Compensation conditions in multilevel inverters with carrier-based sinusoidal modulations Amplitude [%] Amplitude [%] APOD PD Frequency [Hz] 20 Modulation index Amplitude [%] POD Modulation index 15 10 5 0 Frequency [Hz] Modulation index Maximum time integral values vs. the inverter output frequencies and the modulation indexes, for the five-level inverter, modulated using: a) PD, b) APOD, c) POD a) Fast charging station arrangement, b) fast charging terminal developed in cooperation with IEE
Compensator arrangement with CM choke in DC link (C AC1,2,3=20nF, C DC1,2=500nF, L f1,2,3=100mh) b. DC-link-to-ground voltage ripples and collector-emitter emitter voltages Simulation scheme of AC/DC/DC power electronic interface Intrference filtration Simulation scheme of AC/DC/DC power electronic interface Compensator arrangement with CM choke in DC link (C AC1,2,3 =20nF, C DC1,2 =5µF, L f1,2 =5mH) CM choke inductance 20 times smaller!!! DC-link-to-ground voltage ripples and collector-emitter emitter voltages DC-link-to-ground voltage ripples and collector-emitter emitter voltages Compensator arrangement with three-phase input CM choke (C AC1,2,3 =20nF, C DC1,2 =500nF, L f1,2,3 =100mH) Compensator arrangement with CM choke in DC link (C AC1,2,3 =20nF, C DC1,2 =5µF, L f1,2 =5mH) Experimental results b. High overvoltage 600 Without filter 600 With filter 400 400 200 200 DC-link-to-ground voltage ripples and collector-emitter emitter voltages Voltage [V] 0-200 Voltage [V] 0-200 -400-400 -600-600 0 100µ 200µ 300µ 400µ 500µ 0 100µ 200µ 300µ 400µ 500µ Time [s] Time [s] Level [dbµv] Level [dbµv] 130 130 120 x 120 100 + + ++++ 100 80 80 60 60 40 20 CISPR B 0 150k 300k 500k 1M 2M 3M 4M 6M 10M 30M Frequency [Hz] 40 20 CISPR B 0 150k 300k 500k 1M 2M 3M 4M 6M 10M 30M Frequency [Hz]
Power electronic interface with sinusoidal output filter CM current in the generator PE wire, IfCM current and magnetizing g current Voltages of DC buses, DC link voltage and CM voltage in stator windings neutral point (drive without filters) Compensator of DC link-to-ground voltage ripples with CM choke in DC link Voltages of negative DC bus and CM voltage in stator windings neutral point (drive with sinusoidal filter) Compensator of DC link-to-ground voltage ripples with three-phase input CM choke
Placement of triangular carrier functions for modulations: a) PD, b) APOD, c) POD