Research on Interference of AC Power Output Indicator of Diesel Generator
In the diesel generator set control circuit, an LED indicator is often used as an AC power output indicator. The electromagnetic environment of the diesel generator set is complicated, the control cable and the power cable are arranged in the same control cabinet crosswise or in parallel, and the cable is long. For example, after the diesel generator set generates electricity, a magnetic field will form on the periphery of the power cable when the current passes through The change in power forms an electric field on the power cable, which is the induced voltage. The induced voltage is usually between 5 and 2 () V. Due to the poor anti-interference performance of the LED indicator and the low working voltage, the induced voltage causes the diesel generator set to dim the AC power output indicator LED when the output is not closed, which directly affects the operation of the diesel generator set. Judge and take further action. 1 LED Introduction LED is commonly known as light emitting diode. The key part is the semiconductor wafer. It is composed of two types of semiconductors, one is a P-type semiconductor and the other is an N-type semiconductor. These two semiconductors together form a P-N junction. When the wire current passes through the light-emitting diode, the electricity will be directed from the N area to the P area. In the P area, the electricity is combined with the vacancy, and light energy will be emitted to make the light-emitting diode bright. Received: 2018—05—15 About the author: Jiang Jiyun (1985-1), male, -T- '~ g9, is mainly engaged in the research and development of electronic assembly technology and industrial automation. Zhang Yanjing (1983), male, assistant engineer, mainly engaged in electronic assembly technology and equipment management. LED lights have the advantages of using low voltage power, low energy consumption, strong applicability, high stability, short response time, no pollution to the environment, multi-color light emission, high brightness, low heat, long service life and so on. Light-emitting diodes have low energy consumption. The operating voltage of normal light-emitting diodes is 2 to 3.6V, and the power is small, not greater than 0.1W. 2 Generation of induced voltage (1) Alternating magnetic field induction generators, powered power cables, current transformers, capacitors, etc. all have strong alternating magnetic fields around them. According to the principles of Faraday's law of electromagnetic induction, Cables under alternating magnetic field forces are induced to form induced voltages. Detect the induced voltage of the AC power output indicator of the diesel generator set. When the induced voltage reaches 2.6V, the LED of the AC power output indicator will glow, causing the AC power output indicator to indicate incorrectly. (2) Leakage current generated by the power filter capacitor to the ground The power filter is used in diesel generator sets to suppress common mode interference and differential mode interference generated by AC output power. An X capacitor and a Y capacitor are configured in the power filter. The X capacitor is used to eliminate differential mode interference, and the Y capacitor is used to eliminate common mode interference. However, the Y capacitor in the power filter will cause the leakage current of the diesel generator set to increase. This increases the grounding requirements for diesel generator sets. If the grounding is poor, the leakage current will cause a voltage difference. Once the voltage difference reaches the light-emitting threshold voltage of the AC power output indicator LED, the LED will emit light, causing the AC power output indicator. False indication. (3) Interference from non-linear devices 2 () Vol. 35 No. 7 through-cable electric shuttle on July 25, 18] I: Telecom PowerTechnology Ju 1.25, 2018, Vo 1.35 No. 7 In a permanent magnet inverter diesel generator set, the inverter has the function of converting intermediate frequency AC to DC and then DC to power frequency AC. The inverter is equipped with AC and DC mutual conversion devices, as well as some rectifier and filter devices. These devices are non-linear devices and will cause electromagnetic interference to other devices in the permanent magnet inverter diesel generator set. In addition, the inverter uses the SPWM pulse width modulation calculation method, which will generate higher harmonic groups of the switching frequency response. The high carrier frequency and the high-speed switching of the field-controlled switching device will cause serious electromagnetic interference. Other components in the diesel generator set generate electromagnetic interference. (4) Interference between cables due to inductive capacitance In a diesel generator, the power cable and the control cable cross each other, resulting in the formation of capacitance between adjacent parallel cables. If the cable is relatively short, the resulting capacitance is small and will not affect it; if the cable is relatively long, the capacitance formed between the cables will generate an induced voltage. When the induced voltage is close to the LED lighting threshold voltage of the AC power output indicator, The LED will illuminate, causing the AC power output indicator to indicate incorrectly. 3 Solutions According to the analysis of the control circuit of the diesel generator set and the experience of electromagnetic compatibility design, the measures taken to solve the problem of LED interference of the AC power output indicator of the diesel generator set are: (1) Use anti-interference LED indicators with high trigger voltage The lamp is directed at the problem of the incorrect indication of the AC output indicator of the diesel generator set. After discussion with the indicator manufacturer, the use of a high trigger voltage and strong anti-interference indicator can solve this problem. The internal circuit of this kind of indicator light has been improved. It has an additional threshold circuit than the ordinary indicator light, which increases the threshold voltage of the LED, so that the threshold voltage of the LED is increased from 3.6V to 30V in principle. Interference problem of genset AC output indicator. (2) The series resistance on the indicator light is based on the law of conservation of energy. The induced electromotive force on the indicator light is the power source electromotive force of the indicator light. The full circuit formula is: E / (R + r) where E is the power supply emf and the unit is Volts (V); R is the load resistance; r is the internal resistance of the power supply. The internal resistance r of the power supply is zero and the lamp resistance is R. A resistor R is connected in series with the AC power output indicator, then: R — R1 + R2 I— E / (Rl + R2) U 1—R 1 According to the formula, A resistor is connected in series with the power output indicator to divide the voltage, which can effectively reduce the induced voltage of the indicator LED. However, if the resistance is larger, the divided voltage obtained by the resistance will be larger, and the current through the resistance will be smaller. If the resistance is too large, it will affect the normal lighting of the AC power output indicator. Therefore, when solving practical problems, you should Select a suitable resistor according to the actual induced voltage of the AC power output indicator. (3) Line isolation and adjustment of diesel generator set control principle. The auxiliary contact of the output contactor or the normally open contact of the intermediate relay that is closed synchronously with the output switch is used to isolate the interfering component circuits and reduce the components. Mutual coupling and induction. Figure 1 is the schematic diagram of the AC power output switching on and off and output indication control of the diesel generator set. Using the control principle of Figure 1 (a), during the test, the AC output contactor KM1 is not closed, and the AC power output indicator HL1 will appear And HL2 slightly bright case. Power generation (a) control schematic diagram 1 KM l (b) control schematic diagram 2 Figure 1 The schematic diagram of the AC power output switching on and off and output indication control of the diesel generator set adopts the line isolation method, as shown in Figure 1 (b). One end of the AC power output indicator HL2 is isolated from the AC power output indicator HL1 by the normally open auxiliary contact of the AC power output contactor KM1. After adjusting the principle, after testing, when the AC output contactor KM1 is not closed, the AC power output indicators HI1 and HL2 will not light up. (4) Use shielded wire for the cable shielding wire, shielded cable for the cable, and single-core shielded and twisted-pair shielded cable for the multi-core cable. The shielding layer of the shielded cable should be effectively and reliably grounded to avoid induced voltage on the cable. . (5) Reliable grounding and reasonable grounding can eliminate the interference source caused by the ground potential difference caused by the leakage current generated by the power filter's ground capacitance. 4 conclusions In the diesel generator set control system, the induced voltage is universal and there are many interference factors. When solving the interference problem of the AC power output indicator, you should first locate the cause of the interference according to the actual situation, take measures according to local conditions, and comprehensively consider the resolution measures according to the actual reasons. You can use one or more of the resolution measures in this article to implement effective countermeasures. Interference to ensure the normal indication of the AC power output indicator of the diesel generator set. (Continued on page 14) July 25, 2018, Vol. 35, No. 7 Dispatching Power. 潦 Tech Teleom PowerTechnology Ju 1.25, 2018, Vo 1.35 No. 7 4 Simulation of the effect of disordered charging on the distribution network For large-scale disordered charging loads, the charging load calculation method based on Monte Carlo simulation is first used to consider the charging load when the penetration rate of electric vehicles is 5, 1 () and 15 The graph is then added to the background load separately. Now assume that each household owns a car. For a random load point, the load curve after taking into account the charging load of the electric vehicle will be recorded in steps of 3 () rain. Then, for each type of permeability, the day will be divided into 48 time points for recording. . The impact of large-scale application of electric vehicles on the load curve is shown in Figure 4. Time / ll Figure 4 The total load curve of the community under different penetration rates of electric vehicles. It can be seen from Figure 4 that after the electric vehicles are connected, the electricity load of the distribution network in the community will be raised as a whole, and the electricity will be used from 17:00 to 23:00. The load increase is obvious, which is caused by the user's usage habits, because this time is exactly the peak period of work. In this way, not only is there no way to cut peaks and fill valleys for the original load, but it greatly increases the fluctuation of the load. Therefore, it is important to study the simultaneous rate of electric vehicle charging load when considering the distribution network planning. 5 Conclusions By investigating the driving habits of private cars and simulating the rules of car use, this paper fits the daily mileage mileage probability distribution chart and the daily driving end time probability distribution chart to obtain the average charging load curve of a single electric vehicle. The Luo simulation method obtains the charging load curves of multiple electric vehicles. (Continued from page 10) References: [12 Qin Zenghuang. Electrical Engineering (Volume 1) Electrical Engineering Technology (Fifth Edition) [M]. Beijing: Higher Education Press, 2000. E2] Qu Dan. Anti-interference measures of PLC control system in power plant FJ]. Northeast Electric Power Technology, 2006, 27 (2): 47-48.  Lu Xiaodong, Zhu Wenjuan, Shi Ping. Research on the indicator interference of motor control circuit indicator _J]. Electrotechnical Technology, 2009, (08): 63. [43 Zhou Lixiang. Improvement of indicator circuit [J]. Rural Electrician, 1999, (() 6): 34 · 14 · By constructing the actual distribution network structure, consider the charging load simulation of electric vehicles under different penetration rates. The simulation results show that in the disorderly charging mode, the higher the penetration rate of electric vehicles, the larger the peak-to-valley difference in the load curve of the power grid. Therefore, it will affect the reliability, economy, and safety of the substation and distribution network operation. To adversely affect the operation and maintenance of the power system. Therefore, when considering the analysis of the load characteristics of the city network for the development of electric vehicles, it is important to study the simultaneous rate of electric vehicle charging loads.