SAE J 2894-1-2011 Power Quality Requirements for Plug-In Electric Vehicle Chargers.pdf

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5、 Quality Requirements for Plug-In Electric Vehicle Chargers RATIONALE The proliferation of nonlinear loads such as switching power supplies, variable frequency drives and battery chargers have led to a higher level of concern over the impacts of power quality. More precisely there are three major re

6、asons for these concerns: 1. Sensitive microprocessor based devices are more susceptible to power variances. 2. The increased number of non-linear devices has resulted in the rise of harmonics onto the power system leading to reduced system reliability.3. The vast networkability of devices has led t

7、o larger consequences from failure. Ultimately, the success of widespread plug-in electric vehicle (PEV) charging depends in major part to the reliability of both the electric grid and the charger. To meet the needs of PEV operators, PEV chargers must be sufficiently robust, reliable and cost effect

8、ive. In order to achieve this goal, vehicle and equipment manufacturers along with electric utility companies must understand the characteristics of the AC service to which the charger will be connected, as well as the impact chargers can have on service quality. The charger is the “conduit” through

9、 which energy moves from the AC line to the vehicles battery. For practical purposes, it is the charger that controls power quality. FOREWORD Designers and the vehicle manufactures that implement PEV battery chargers must understand the characteristics of the AC service to which the equipment will b

10、e connected if they are to develop products that are sufficiently robust, reliable and cost effective to satisfy the needs of the PEV owner. The charger designer and vehicle manufacturer must also understand that the battery charger can have a significant impact on the quality of the AC service to w

11、hich it is connected. The information presented in this Recommended Practice may be used by charger power supply designers, managers of charger development programs, and an electric utility. NOTE: This SAE Recommended Practice is intended as a standard practice and is subject to change to keep pace

12、with experience and technical advances SAE J2894-1 Issued DEC2011 Page 2 of 16 TABLE OF CONTENTS 1. SCOPE 32. REFERENCES 32.1 Applicable Documents 33. DEFINITIONS . 44. CHARGER POWER QUALITY PARAMETERS . 64.1 Displacement Power Factor 64.2 4.2 Power Conversion Efficiency 74.3 4.3 Total Harmonic Curr

13、ent Distortion 84.4 4.4 Current Distortion at Each Harmonic Frequency 94.5 Inrush Current . 95. CHARACTERISTICS OF THE AC SERVICE . 105.1 Voltage Range 115.2 Voltage Swell 115.3 Voltage Surge . 115.4 Voltage Sag . 115.5 Voltage Distortion 125.6 Momentary Outage . 125.7 Frequency Variation 125.8 Port

14、able (Self) Generation / Distributed Energy Resources . 126. CHARGING CONTROL 136.1 Utility Messaging . 136.2 Communication . 136.3 Cold Load Pickup 136.4 Load Rate (Soft Start) . 14APPENDIX A 15FIGURE 1 AC LINE VOLTAGE/LINE CURRENT PHASE RELATIONSHIP 6FIGURE 2 TYPICAL INPUT CIRCUIT 7FIGURE 3 COLD L

15、OAD PICK-UP the vehicle inlet and the coupler. The charge coupling is actually a take-apart transformer, the coupler comprising the transformer primary and the vehicle inlet housing the transformer secondary. 3.7 ON-BOARD CHARGER A charger located on the vehicle for the purpose of delivering DC ener

16、gy to the PEVs energy storage device. Typically requires an AC input from an external EVSE. 3.8 OFF-BOARD CHARGER A charger located externally to vehicle for the purpose of delivering DC energy to the PEVs energy storage device. Typically requires an AC input from the sites electrical infrastructure

17、. 3.9 DC CHARGING A method that uses a dedicated off-board direct current (DC) BEV or PHEV supply equipment to provide energy from an appropriate off-board charger to the BEV or PHEV in either private or public locations. 3.10 ELECTRIC VEHICLE SUPPLY EQUIPMENT (EVSE) The conductors, including the un

18、grounded, grounded, and equipment grounding conductors, the electric vehicle connectors, attachment plugs, and all other fittings, devices, power outlets, or apparatuses installed specifically for the purpose of delivering energy from the premises wiring to the electric vehicle. Charging cords with

19、NEMA 5-15P and NEMA 5-20P attachment plugs are considered EVSEs. 3.11 FREQUENCY VARIATION The normal range of variation of the AC line frequency. 3.12 MOMENTARY OUTAGE A complete loss of AC line voltage for a 12 Cycles (200 ms) or more. 3.13 VOLTAGE RANGE The normal range of variability of the AC li

20、ne voltage. Voltage Range is generally expressed as a “percent of nominal“ of the nominal value of line voltage varies regionally. SAE J2894-1 Issued DEC2011 Page 6 of 16 3.14 VOLTAGE SAG A reduction in the AC line voltage below the normal range of variability, typically of relatively short duration

21、, typically 30 to120 cycles (500 ms to 2000 ms). 3.15 VOLTAGE SURGE (TRANSIENT) A temporary increase in the AC line voltage far beyond the normal range of variability that is evidenced by a sharp brief discontinuity of the waveform, typically of very short duration (sub-cycle) 3.16 VOLTAGE SWELL A t

22、emporary increase in the AC line voltage of more than 10% of the normal range of variability at the power frequency, typically of relatively short duration of half a cycle to a few s (8ms 5000ms) 4. CHARGER POWER QUALITY PARAMETERS 4.1 Displacement Power Factor Total power factor is defined as the r

23、atio of real power in Watts to apparent power in Volt-Amps, and is expressed by the following formula: Displacement Power Factor = Real Power (kW) / Apparent Power (kVA) If voltage distortion is negligible, total power factor is equal to the product of displacement power factor and distortion power

24、factor. Displacement power factor, which is the ratio of real power to apparent power at the fundamental frequency (50Hz / 60 Hz), is a measure of the phase shift that occurs between line voltage and line current when the AC line is loaded with a linear load having reactive characteristics, such as

25、an AC motor. The line current is sinusoidal in shape, but either leads or lags the line voltage in phase (Figure 1). FIGURE 1 - AC LINE VOLTAGE/LINE CURRENT PHASE RELATIONSHIP Distortion power factor is the ratio of fundamental current to total rms current. The line current distortion is normally th

26、e result of non-linear loading of the AC line. Most switching power supplies, except those that incorporate active power factor correction, use full wave bridge rectifiers with capacitive input filters to perform AC to DC conversion from the line (Figure 2). The rectified AC peak charges the input c

27、apacitor to produce a DC voltage nearly equal to the peak line voltage. Because the capacitor is peak charged, the diodes in the bridge rectifier are reverse biased for most of the AC sine wave, forward biasing only near the peak of the line voltage where V(line) exceeds V(cap) + 2 x V(diode). The “

28、resulting currents are highly distorted from the ideal sine wave, and contain harmonics of the fundamental line frequency. SAE J2894-1 Issued DEC2011 Page 7 of 16 FIGURE 2 TYPICAL INPUT CIRCUIT Maintaining a high input power factor is important for two reasons. A. Maintaining a high power factor min

29、imizes reactive line current and harmonic currents of the fundamental line frequency. Because available power is limited by available line current which is in turn limited by the circuit breaker protecting the line, minimizing reactive and harmonic currents maximizes the line current which is actual

30、ly available for true power delivery. B. Minimizing reactive and harmonic currents minimizes heating of the AC service conductors for a specified delivered power. This permits optimal utilization of infrastructure and may eliminate the need to perform a service upgrade when EV battery chargers are i

31、nstalled. The recommended minimum values for total power factor are defined in Table 1 below. These values are specified for operation at the full rated output power of the charger. Recommended Displacement Power Factor Values AC Level 1 AC Level 2 DC 95% 95% 95% TABLE 1 - MINIMUM RECOMMENDED GUIDEL

32、INES FOR TOTAL POWER FACTOR 4.2 4.2 Power Conversion Efficiency Power conversion efficiency is a measure of how efficiently the charging equipment processes power from its input terminals to its output terminals. Power conversion efficiency can be measured over the total charging cycle or at any poi

33、nt in the charging cycle. Due to the typical battery charging profile, the charger efficiency will be greatly reduced at the “finishing off“ part of the chargingcycle, when minimal power is delivered. Efficiency is most important when the charger is delivering maximum power to the load because low p

34、ower conversion efficiency at full output may constitute a significant power loss. Power conversion efficiency is defined as a ratio of the charger input power to the charger output power per the following equation: SAE J2894-1 Issued DEC2011 Page 8 of 16 Power Conversion Efficiency (%) = DC Power (

35、kW) at Charger Output / AC Power (kW) at the Charger Input x 100 Full power efficiency is this ratio measured at the rated full power output of the charger. Because all power processing systems have loss, power efficiency is always less than 100%. Full power efficiency is important for two reasons.

36、A. An efficient charger reduces battery recharge time by optimally accessing energy from the AC line and delivering it to the battery. Since all electric services are current limited (therefore power limited) less wasted power equals greater power delivery to the battery which reduces charge time. B

37、. High power conversion efficiency is consistent with the underlying philosophy of emissions reduction. A highly efficient charger reduces the required energy production for a given energy transfer to the vehicle, thereby, reducing the pollutants produced by the energy production process.Recommended

38、 minimum values for power conversion efficiency are specified in Table 2. These values are specified at the full rated power of the charger into a resistive load. Note: System energy efficiency defines how the system uses the energy that the charger delivers. The charger cannot control how the syste

39、m uses energy. Therefore, it is not possible to specify system energy efficiency as a controlled parameter for a charger. Conversely, power conversion efficiency does not dictate how the system uses energy. It is a function of the design of the charger and therefore can be specified as a controlled

40、parameter for the charger. Recommended Full Power Conversion Efficiency AC Level 1 AC Level 2 DC 90% 90% 90% TABLE 2 - MINIMUM RECOMMENDED GUIDELINES FOR FULL POWER CONVERSION EFFICIENCY 4.3 4.3 Total Harmonic Current Distortion Periodic waveforms can be broken down into component sine waves which a

41、re referred to as harmonics of the fundamental wave form. These harmonic frequencies are integer multiples of the fundamental frequency of the periodic wave form. Each harmonic has a specific amplitude and phase with respect to the fundamental. The vector sum of all harmonics produces the original p

42、eriodic wave form. If the periodic waveform is a “pure“ sinusoid, then only the fundamental frequency is present. There are no harmonics. Any undesired departure from the purely sinusoidal wave shape is referred to as harmonic distortion. Total harmonic distortion (THD) is the root mean square of ea

43、ch individual harmonic distortion. It is desirable for any current drawn from the AC line to have a fundamental frequency equal to the line frequency (50/60 Hz) with no harmonic distortion. This is because only fundamental current contributes significantly to true power delivery. Harmonic currents d

44、o not contribute to true power because the product of the undistorted line voltage and the harmonic currents, averaged over one full cycle of the AC line, is always equal to zero. In short, harmonic currents that flow on the AC line contribute nothing to true power delivery. They simply heat the wir

45、e and, in so doing, waste energy. Harmonic currents can also cause distortion of the AC line voltage. This is dependent on the line impedance (l x R drops) and the presence of resonances due to the capacitances and inductances in the system. This distortion, if severe enough, may cause other equipme

46、nt connected to the line to malfunction or even sustain damage. SAE J2894-1 Issued DEC2011 Page 9 of 16 Institute of Electrical and Electronics Engineers (IEEE) 519 is a guide for utilities on limiting the amount of harmonic voltage and current distortion allowed on their system. The guide specifies

47、 that the total harmonic distortion of the voltage waveform for voltages below 69 kV should not exceed 5 percent. In addition, no individual voltage harmonic should exceed 3 percent. This guide also provides for harmonic current limitations for customers at the point of common coupling (where the cu

48、stomer interfaces with other customers on the utility system) based on the ratio of total load current to the available short circuit current. There are specific limits for individual as well as total harmonic currents as a percentage ofthe total load current. For practical purposes, this guideline

49、is applied only on large nonlinear loads. Since the guideline isbased on available short circuit current which varies at each location, it cannot be used as an equipment guideline. It does contain useful information explaining how harmonics are produced and how they effect other equipment. It also contains recommendations for limiting harmonic currents, and thus voltage distortion to safe levels for proper equipment operation. To m