2300 volts submersible pump dedicated inverter system
Abstract: After introducing many shortcomings of traditional power supply mode of submersible electric pump, this paper elaborates The advantages of frequency conversion power supply, and then gives the 2300V submersible pump inverter several special requirements and solutions. Keywords: inverter, submersible pump, low-pass filter, compensation voltage Abstract: Several disadvantages of the traditional power supply methods for latent oil electro-pump are given in this paper, and then some advantages of the inverting frequency power supply methods are described. This paper describes the proper characteristics and their solutions in 2300V inverter. Key words: inverter, latent oil I. INTRODUCTION It is the trend of the times to transform the existing oilfield production equipment by modern high-tech. It uses modern self-control technology and frequency conversion speed regulation technology to provide the submersible pump for oil field (hereinafter referred to as submersible pump) The ideal power is this technology change An important part of the process. Submersible pump voltage levels mostly 1140V and 2300V. Submersible pumps press placed 1000 to 3000 meters below ground level, the working environment is extremely harsh (high temperature, strong corrosion, etc.), the traditional power supply Way - full pressure, power frequency make it frequent failures, operating costs greatly increased. Submersible pump mentioned damage to the ground to repair, only one project costs up to 50,000 yuan, the value of 100,000 yuan on average put on the cable down 5 times Need to be replaced, the submersible pump must be repaired every 10 months on average once, the maintenance cost is about 80,000 yuan.Traditional power supply is harmful.For example: * The submersible pump runs at full speed, when the downhole fluid volume is not rich, it is easy to take the time, or even Resulting in dead wells, once the dead wells, the heavy losses. * Full pressure, power frequency work start current, impact torque, not only wasted electricity, but also have a great impact on motor life. * Oilfield supply voltage fluctuations, Motor under excitation or over excitation, the motor is burned from time to time. * A few kilometers downhole cable brings about 150 volts of line loss, as part of the loss can not be compensated, thus affecting the normal operation of the motor. Out, the traditional submersible pump power supply must be modified, the more ideal Power supply equipment should have the following special features: * Soft start * Convenient speed control, that is, variable frequency operation. Start-up time and operating speed can be arbitrarily set according to working conditions. * Unaffected by supply voltage fluctuations, and to compensate for cable line losses. The transmission must be a sine wave, or by the cable reflection, the voltage pulse superimposed, easy to burn the motor. * A variety of protection functions. * Convenient control, simple operation, clearly displayed. Obviously, meet these requirements must be none other than the inverter The market is easy to buy those fans for the fans, pumps are not suitable for those who drive, because the voltage level does not match, the output waveform is not sinusoidal, cable loss voltage can not be compensated. My company commissioned by the oil field successfully developed a 1140V, 30 ~ 100KW Submersible pump inverter series now bear the 2300 volts submersible pump dedicated inverter development task. Second, the development of special inverter submersible pump although different voltage levels, but the online operation of mostly 1140 volts and 2300 V industry useful 380-V class inverter with a special step-up transformer reported in this paper that this one high and one low-high program has inherent deficiencies, so that the step-down transformer step-down at low frequency is very Difficulties, the addition of the transformer has increased the cost of the product, the withstand voltage of the IGBT device is already higher now, the converter below 3000 volts does not need to ask to help the transformer, our company 1140V submersible electric pump has already operated normally in several fields, The effect is very good.This paper mainly introduces the performance and development of 2300V submersible pump dedicated inverter.The technical specifications of the inverter are as follows: Three-phase input: 2300V, 50Hz Three-phase output: Rated voltage is 2300V, capacity 110kW Frequency range 2HZ ~ 50HZ continuously adjustable voltage loss on the cable can be properly compensated. Output waveform: sine control, protection with the ordinary inverter. This article only the technical characteristics of the inverter system is briefly described as follows: (and 380V Universal Frequency The same part of the device will not repeat them.) 1, the choice of the main circuit and power devices In the PWM voltage 380V inverter, the general use of two-level circuit.If the two-level circuit to achieve the output of 2300V is bound to use expensive high voltage In order to reduce the power device voltage requirements and reduce the output voltage of the harmonic components, the design uses three-level circuit. The main circuit diagram shown in Figure 1. The main circuit shown in the three-level part The circuit, called the "NeturalPointClamped-Npc" mode, can not only output higher voltage, but also reduce output harmonic and voltage change rate (dv / dt). The good waveform is one of the goals of this design. The power switching device in the figure uses the Siemens dual-cell IGBT module (1700V, 200A). After rectification, two large capacitors are connected in series to form a filter. The connection point of the two capacitors is the center point of the circuit Level.) With a three-level circuit structure, 3300V IGBT module can achieve 2.3KV inverter output, but we are familiar with the supplier 3300V IGBT module is not available, only scheduled, because the task is tight, had to use 1700V Dual unit modules in series as a unit to use, so the cost will be lower, just take this opportunity to study the device in series dynamic pressure equalization problem, the IGBT symbol in Figure 1.It is a simplified representation of double cell series .IGBT power devices Of the main series to solve the problem of pressure equalization, steady-state pressure is relatively easy, the two series of two tubes are the same module within the device, manufacturing processes and ambient temperature are basically the same, so do not take too many measures should be the main fine On the dynamic pressure on.After screening, the design of the voltage sharing circuit shown in Figure 2. Equal voltage circuit shown by the resistor R1, R2, capacitor C, diode D. Resistor R1 play the role of static voltage, R2, C, D are the same as the ordinary snubber circuit, the main purpose here is to start the role of pressure equalization. Equalization process is mainly done by the capacitor C. Series two IGBT, the switching speed will not be exactly the same, but will be slightly There is a difference between the voltage on the capacitor C under static conditions the same value in the switching process, the voltage on the capacitor can not be abrupt changes forced the two IGBT voltage drop does not occur due to the switching process in the two IGBT The effect caused by the inconsistency of current is compensated by the charge and discharge of capacitor C. The process of dynamic voltage equalization shows that the better the switching performance of the two IGBTs is, the better the voltage sharing effect is; the larger the value of capacitor C is, the better the voltage equalizing effect is. However, too large C value will cause excessive power dissipation on R2 P = 1 / 2CV2f, V is the transition voltage of a single IGBT, to limit the power dissipation on R2, should be as small as possible the capacitance C Value and take a lower modulation frequency f.2, the choice of carrier frequency to improve the carrier frequency to improve the waveform, low noise, good , But the carrier frequency increases, will increase the switching loss, so the choice must weigh the pros and cons, the device carrier frequency selected 3.4KHZ, select this value takes into account the output LC low-pass filter inductor core weight factor.3 , The steady input voltage of the input voltage after rectification, DC bus voltage filter to Uo said that there is a voltage sensor, the output voltage Ut is proportional to the bus voltage Uo, the Ut value sent to the microcontroller to make Uo Ut value corresponding to the rated value is 1, Ut> 1 when the grid voltage fluctuates upwards, Ut4 fluctuates when the grid voltage fluctuates downward. Obtaining the sine wave of the output terminal The voltage type inverter outputs three-phase SPWM wave, that is, the width is sinusoidal Distributed rectangular pulse wave.This wave is sent directly to the motor, the motor is an inductive load, so you can get an approximate sinusoidal drive current.From the inverter to the submersible pump there are a few kilometers of cable, if the PWM wave Directly on the cable input, due to long-term effect motor side will be several times the peak value of the rated voltage impact, the motor is likely to be burned.Therefore, three-phase low-pass LC filter is necessary, the filter circuit shown in Figure 3 As shown, The design of the cut-off frequency of about 1 / 3.5 of the carrier frequency, cable loss compensation submersible pumps on the V / F curve and no special requirements, the frequency down to 30HZ has no oil, in order to achieve soft start, the device The starting frequency is set at 2HZ, 50HZ corresponds to the rated output of 2300V, and the cable compensation voltage Vb is adjusted according to the specific situation of each well. The V / F curve is shown in Fig. 4. The size of Vb determines the starting performance of the motor, , Will make the starting current is too large, causing the loss increase, Vb is too small, can not get up.Vb small gradually increased, the output current will inevitably change accordingly, when the motor starts running, the current will be obvious Different.According to this idea we have compiled a software, called the compensation voltage adaptive process.If the software is very successful, each time you start do not have to manually adjust the current software needs to be further improved, so the prototype Still retains the manual adjustment of the potentiometer Third, the operation of 2300V submersible pump inverter has been successfully developed, the technical indicators are to meet the design value, with rated load is running well The steady-state series pressure pipe unbalance in 10 % Or less, move Voltage unbalance is seen within 15% of the oscilloscope. The voltage after the output filter is arbitrarily tuned over the entire range of the submersible pump, the waveforms are all sinusoidal (distortion is very small), the motor is In low speed, light load, the operation is also very smooth, uniform, without any pulsation, the motor speed and flexibility in the entire frequency range of convenience.
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