CN2800285Y - Line power frequency parameter tester - Google Patents

Abstract

The utility model relates to a line power frequency parameter tester, which comprises a three-phase electric output end, a test power supply with three-phase output, a measuring part for measuring parameters on the three-phase electric output end; the test power output end and the three-phase The electrical output terminal is connected; the test power supply is a test power supply that outputs a three-phase variable-frequency alternating current of sinusoidal pulse width modulation waves. The test power supply adopts a three-phase variable frequency AC test power supply that can output sinusoidal pulse width modulation waves. The characteristic of the frequency conversion test is to change the frequency of the current signal injected into the test line. The test frequency is different from the power frequency (the output frequency is 50Hz). Therefore, the volume of the test power supply part is greatly reduced, so that the volume of the line power frequency parameter tester is also greatly reduced, the weight is greatly reduced, and it is easy to carry.

Description

A Line Power Frequency Parameter Tester

technical field

The utility model relates to the technical field of high voltage, in particular to testing equipment for testing line power frequency parameters.

Background technique

Line power frequency parameter measurement equipment is a measurement equipment for measuring parameters such as positive sequence open circuit, positive sequence short circuit, zero sequence open circuit, zero sequence short circuit, and line direct resistance of high voltage lines. Line power frequency parameter measurement equipment is generally composed of a test power supply and a measurement part.

During the line power frequency parameter test, because the line under test is affected by adjacent lines or other outgoing lines of the substation, there is current and voltage interference on the line with the same frequency as the system (power frequency 50Hz), in order to offset the interference caused by this Influence, the test power supply needs to increase the injected power frequency current or increase the test voltage to improve the signal-to-noise ratio, and the large test current and high test voltage will inevitably lead to a large test power supply part of the measurement equipment. For example, the existing line power frequency parameter test equipment often uses a three-phase voltage regulator and a 10kV distribution transformer as the test power supply. The test equipment is heavy and heavy, and it needs to be transported by truck and loaded and unloaded by a crane on site. This brings great inconvenience to the field test work, and also brings hidden dangers to the safe operation of the substation and the personal safety of operators.

The current transmission corridor is becoming more and more compact, and the power frequency interference (electrostatic induction and electromagnetic induction) during parameter measurement is becoming increasingly severe. It is more difficult to achieve interference suppression by greatly improving the signal-to-noise ratio, and it will bring greater impact to the measurement results. The error also increases the requirement for the capacity of the test power supply.

In addition, the power frequency parameter measurement part of the existing line is generally a pointer electrical instrument (such as: ammeter, voltmeter, etc.), which requires manual reading, and the reading is highly random, which affects the result of parameter measurement.

Contents of the invention

The technical problem to be solved by the utility model is to provide a line power frequency parameter tester, which is small in size, light in weight and easy to carry.

The technical solution adopted by the utility model to solve the problems of the technologies described above is:

A line power frequency parameter tester, which includes a three-phase electrical output terminal, a test power supply with three-phase output, and a measurement part for measuring parameters on the three-phase electrical output terminal; the test power output terminal is connected to the three-phase electrical output terminal ; The test power supply is a test power supply of a three-phase variable-frequency alternating current outputting sinusoidal pulse width modulation waves.

In the above solution, the circuit for testing the power supply includes in sequence from the input end to the output end:

The AC-DC conversion part used to convert the mains power into DC power,

DC-DC conversion part for converting direct current into direct current,

The DC-AC frequency conversion conversion part of the three-phase frequency conversion AC power used to convert the DC power into a sinusoidal pulse width modulation wave.

In the above solution, a three-phase isolated transformer output part is provided between the test power output terminal and the three-phase electrical output terminal.

In the above scheme, a three-phase output filtering part is provided between the output terminal of the test power supply and the three-phase electrical output terminal.

In the above solution, the tester also includes a control power supply for supplying DC power to the inside of the tester.

In the above solution, the tester also includes a three-phase sinusoidal pulse width modulation control module that is provided to the power module of the DC-DC conversion part as a switch control signal.

In the above solution, the tester also includes an online programmable circuit for controlling the control power supply.

In the above solution, the measurement part includes an industrial computer, a voltage sensor, and a current sensor; the output terminals of the voltage sensor and the current sensor are input into the industrial computer through signal modulation and A/D conversion.

In the above solution, the voltage sensor and the current sensor include three phase voltage sensors and current sensors, one mutual inductance voltage sensor and current sensor, one direct resistance voltage sensor and current sensor.

In the above scheme, the output frequency of the test power supply is 52.5Hz.

Compared with the prior art, the utility model line power frequency parameter tester has the following advantages:

1. The test power supply adopts a three-phase variable frequency AC test power supply that can output sinusoidal pulse width modulation waves. The characteristic of the frequency conversion test is to change the frequency of the current signal injected into the test line. The test frequency is different from the power frequency (the output frequency is 50Hz). It can remove the influence of power frequency interference, therefore, the volume of the test power supply part is greatly reduced, so that the volume of the line power frequency parameter tester is also greatly reduced, the weight is greatly reduced, and it is easy to carry.

2. The test power supply includes: AC-DC conversion part, DC-DC conversion part, DC-AC frequency conversion conversion part, the circuit design is simple, and the volume is small.

The function of the AC-DC conversion part (AC to DC rectification conversion part) is to realize the rectification conversion of the system mains (220V AC power supply) into a fixed output DC power supply; the function of the DC-DC conversion part (DC to DC conversion part) is Realize the rectification and transformation of the unstable DC power supply for voltage stabilization processing, and transform the voltage to a stable amplitude suitable for the output requirements; the function of the DC-AC frequency conversion conversion part (DC to AC frequency conversion conversion part) is to realize the voltage stabilization The power supply is inverted into a three-phase AC power supply whose output is a sinusoidal pulse width modulated wave.

3. There is a three-phase isolation transformer (output part) between the output terminal of the test power supply and the three-phase electrical output terminal, which can realize the output of the sinusoidal pulse width modulation wave into a sinusoidal waveform with a certain degree of smoothness through LC filtering.

4. The output part of the three-phase isolation transformer can electrically isolate the output of the previous stage from the measured object, and at the same time perform voltage amplitude conversion according to the design requirements, and use the leakage inductance of the transformer by connecting filter capacitors in parallel at the output stage further filtering.

5. The control power conversion module can provide the internal DC power required for the tester to work.

6. The measurement part includes industrial computer, voltage sensor, and current sensor; the output terminals of the voltage sensor and current sensor are input into the industrial computer through signal modulation and A/D conversion, so as to realize the measurement and operation of multiple voltages, current amplitudes, and phases.

The line power frequency parameter tester of the utility model can independently complete the line power frequency parameter measurement work.

Description of drawings

Fig. 1 is the structural block diagram of the utility model circuit power frequency parameter tester embodiment

Figure 2 is a functional block diagram of the test power supply

Figure 3 is the circuit schematic diagram of the test power supply

Figure 4 is a structural block diagram of the measurement part

Figure 5 is a schematic diagram of the PID link

Figure 6 is a schematic diagram of sinusoidal pulse width modulation waveform generation

Detailed ways

As shown in Figure 1, the utility model patent includes three-phase (A phase, B phase, C phase) electrical output terminals, a test power supply with three-phase output, and a measurement part for measuring parameters on the three-phase electrical output terminals 1. Provide the control power supply of DC power supply to the tester, and the online programmable circuit for controlling the control power supply (on-line programming module control); the output terminal of the test power supply is connected to the three-phase electrical output terminal; Phase conversion frequency (output frequency 52.5Hz) alternating current test power supply.

As shown in Figure 2, the circuit of the test power supply includes in turn from the input end to the output end: the AC-DC conversion part (AC to DC rectification conversion part) used to convert the mains power (220V single-phase AC power supply) into DC power, The DC-to-DC conversion part (DC to DC conversion part) for converting direct current into direct current, and the DC-AC frequency conversion conversion part (DC to AC frequency conversion part) for converting direct current into three-phase variable frequency alternating current of sinusoidal pulse width modulation wave ).

As shown in Figure 4, the measurement part includes industrial computer and sensor circuit (voltage sensor, current sensor); the output terminals of voltage sensor and current sensor are input by switching control module, signal modulation, A/D conversion (multi-channel data acquisition module) The industrial computer controls the core circuit.

As shown in Figure 3, the circuit of the power supply is tested. The design of the AC to DC rectification conversion part (Part A) is relatively simple. The input single-phase AC 220V power supply passes through the rectification bridge to obtain a DC rectification power supply. The load characteristics of this rectification power supply are very good. The difference is that it cannot be used to directly provide the DC to AC (C part) frequency conversion part, so the intermediate conversion link of the DC to DC (B part) conversion part is set.

The DC to DC conversion part converts the input into a stable DC power supply with a specific voltage output. It is an automatic control system with a feedback link. It consists of four main parts: IPM high-frequency chopping, high-frequency intermediate transformer, high-frequency rectification, high-frequency frequency filtering.

The DC to AC frequency conversion part is the most critical part of the variable frequency power supply. The setting of the frequency and the adjustment of the output voltage are all realized through this joint. Although there are not many power components in this part, it is very important. The harmonics of the power supply Multiple performance indicators such as wave content and frequency stability are determined by the design of this part.

The rectifier bridge composed of D1-D4 and the main electrolytic capacitor C1 can be selected according to the ordinary rectifier circuit. In the actual circuit, the rectifier bridge is KBPC3510 rectifier bridge. C1 uses three 680uF high-frequency electrolytic capacitors connected in parallel. The equivalent resistance and equivalent series inductance value are the important reasons for the high-frequency current to cause the electrolytic capacitor to heat up. The selection of C2 is the same as that of C1.

T1-T4 are IGBT devices, which are integrated in one package. In industrial production, the overheating and partial overcurrent protection detection circuits are integrated into a module, which is called an IPM intelligent module. When selecting an IPM module, consider its maximum withstand peak current and maximum turn-off surge voltage peak value. In practical applications, a specially designed buffer circuit is connected in parallel at both ends of the module as voltage protection to reduce the maximum surge peak value. T5-T8 The selection is the same as T1-T4.

The rectifier tubes D5-D8 are different from ordinary rectifier diodes. They work in the state of high-frequency current, and the fast recovery tubes with short reverse recovery time and soft recovery characteristics must be selected within the current tolerance range, and corresponding buffer circuits are used to reduce the voltage. Mutation spikes.

Inductor L and capacitor C2 form a filter circuit, and its value should be selected according to the crossover frequency and filter effect of the system. The inductor core is made of ferrite, a high magnetic permeability material. (remove below)

Considering the above principles, the selected parameters after calculation are as follows:

The inverter intelligent module uses Mitsubishi PM30CSJ060 (30A/600V);

D5-D8 use IXYS company DSEI60-10A fast recovery tube;

C1 and C2 respectively use three 680uF Hitachi high-frequency electrolytic capacitors in parallel;

L selects 1.5mH/8A/30KHz ferrite intermediate frequency inductor.

In the control part, the core is the PWM chopper module of the DC to DC link and the SPWM sine wave pulse width modulation module of the DC to AC link. The former realizes voltage conversion and voltage stabilization functions, and the latter realizes DC/AC conversion and frequency modulation and voltage regulation Function; the design of the fault protection circuit is a reliable guarantee for the safe operation of the system.

The PWM chopper control circuit is composed of the updated product SG3525A of the PWM special chip SG3524 and peripheral circuits. Compared with SG3524, many performances and functions of this chip have been improved: under-voltage lockout and slow start circuits have been added, pulse width modulation comparators and error amplifiers have been improved, and the anti-interference performance has been greatly enhanced, and the switching frequency can be as high as 200KHz. Excellent PWM dedicated chip.

PWM chopper control works in a closed-loop feedback system. For a constant load under AC voltage, it is roughly equivalent to the situation of a constantly changing load under constant voltage. This is a severe test for the dynamic stability of the power control system. The control parameters need to track the changes of the output all the time, and the open-loop control system cannot meet this requirement. In order to ensure the stability and dynamic quality of the output voltage, a feedback link and a series correction link are introduced to form a closed-loop automatic control system. The accuracy and characteristics of the feedback link directly control the quality of the system, and the measuring components of the feedback link are required to have high measurement accuracy, stable characteristics, and responsive performance. The role of the series correction link is to make the deviation operate according to a certain law to improve the dynamic quality or steady-state performance of the system. The PID (proportional, integral, differential) regulator in this test power supply is such a series correction device. As shown in Figure 5, the PID regulator is composed of proportional, integral and differential circuits.

Tests have shown that only PI regulation cannot meet the requirements of system performance at all, and its output voltage waveform will produce corresponding distortion with the magnitude of the output current. The greater the output current at a certain point of the waveform, the farther the voltage waveform at this position is from the standard sine wave ( This position is at the peak and valley of the waveform in a purely resistive load). For this reason, a differential link is added on the basis of proportional integral control. Although the complexity of the circuit is increased, the dynamic performance of the system can be improved. Here, we use an operational amplifier to implement the PID function.

During the commissioning, it was found that the complexity and sensitivity of the dynamic parameters of the single-phase AC power supply far exceeds that of the DC power supply, and the parameters of the PID link must be carefully and repeatedly adjusted on the basis of calculations to obtain satisfactory results.

SPWM is the English abbreviation of sine wave pulse width modulation. The function of the inverter unit is to convert direct current into alternating current. In order to obtain a standard sine wave at the output, it is necessary to control the inverter unit with certain rules. This process is called sine pulse width modulation. The sine wave pulse width modulation inverter is to convert the output into a series of high-frequency pulses of equal amplitude and whose width changes according to the sine law (as shown in Figure 6). These pulses are integrated, and the effect is equivalent to a sine wave. If the output Adding a filter to filter out high-frequency components can result in a smooth sine wave.

The key to realizing the SPWM inverter is to obtain the driving signal that changes according to the law, that is, the sinusoidal pulse width modulation signal (SPWM). There are many ways to get the SPWM signal. From the circuit form generated, it is nothing more than analog mode, digital mode, and digital-analog hybrid mode. No matter which method is used, their principles are the same, that is, by comparing the standard sine wave ( Modulating wave) and the instantaneous value of high-frequency triangular wave (carrier) to obtain a series of pulse signals, of course, the obtained series of pulses cannot be directly used as the driving signal of the switch, but must also go through dead zone protection, distribution processing and so on. Figure XX shows its modulation principle, and due to space limitations, the principle will not be described here.

Earlier, some companies made this part of the function into a special three-phase SPWM chip HEF4752. With the development of technology, this chip has been eliminated. At present, it is popular to use high-speed single-chip microcomputer or industrial computer to realize it, but the design is complex and the development cycle is long; we found in the investigation process that the British MITEL company has launched a new chip SA866AE for motor speed regulation. We are investigating this After careful analysis of this product, it was successfully applied to the design of the test power supply. This solution only needs a piece of SA866AE chip packaged in PLCC32 and a serial EEPROM packaged in DIP8 package. The area of the SPWM core composed of these two chips is less than 2 square centimeters on the printed board, which is compact and practical. This solution not only has the function of generating SPWM waves, but also integrates functions such as signal distribution, dead zone control, pulse cancellation, and fault monitoring. It should be an excellent and practical SPWM solution.

As shown in Figure 2, a three-phase isolation transformer output part, a three-phase AC output filter part, and a fault detection and alarm circuit are arranged between the output terminal of the test power supply and the three-phase electrical output terminal.

The function of the fault detection and alarm circuit is to detect faults such as output overload, short circuit, and power device overcurrent during the working process of the power supply in real time, and turn off the power supply control signal and give a fault alarm prompt. The fault protection types of the fault detection and alarm circuit in the embodiment of the utility model include: output overvoltage protection, output overcurrent protection, overload protection, IPM overcurrent protection, DC arm overvoltage protection, and DC arm overcurrent protection. value, first turn off the drive circuit of the IPM.

The embodiment of the utility model also includes a three-phase sinusoidal pulse width modulation control module and an online programmable circuit provided to the power module of the DC-DC conversion part as a switch control signal.

The function of the three-phase sinusoidal pulse width modulation control module is to generate a series of unequal-width square wave signals of a certain fundamental frequency according to the measurement requirements, and provide them to the IPM power module as a switch control signal.

The function of the FPGA large-scale online programmable circuit is to realize the logic needed to control the power supply.

As shown in FIG. 4 , the voltage sensor and the current sensor include three phase voltage sensors and current sensors, one mutual inductance voltage sensor and current sensor, and one direct resistance voltage sensor and current sensor.

Claims (10)

1. A line power frequency parameter tester, which includes a three-phase electrical output terminal, a test power supply with three-phase output, a measurement part for measuring parameters on the three-phase electrical output terminal; the test power output terminal and the three-phase electrical output Terminal connection; It is characterized in that: the test power supply is a test power supply of three-phase variable-frequency alternating current outputting sinusoidal pulse width modulation waves. 2. The tester according to claim 1, characterized in that: the circuit for testing the power supply sequentially includes from the input end to the output end: The AC-DC conversion part used to convert the mains power into DC power, DC-DC conversion part for converting direct current into direct current, The DC-AC frequency conversion conversion part of the three-phase frequency conversion AC power used to convert the DC power into a sinusoidal pulse width modulation wave. 3. The tester according to claim 1, characterized in that: a three-phase isolation transformer output part is provided between the test power output terminal and the three-phase electrical output terminal. 4. The tester according to claim 1, characterized in that a three-phase output filtering part is provided between the output terminal of the test power supply and the three-phase electrical output terminal. 5. The tester according to claim 1, characterized in that the tester further comprises a control power supply for supplying DC power to the inside of the tester. 6. The tester according to claim 2, characterized in that the tester further comprises a three-phase sinusoidal pulse width modulation control module which is provided to the power module of the DC-DC conversion part as a switch control signal. 7. The tester as claimed in claim 5, characterized in that the tester further comprises an online programmable circuit for controlling the power supply. 8. The testing instrument according to claim 1, characterized in that: the measuring part includes an industrial computer, voltage sensor, and current sensor; the output terminals of the voltage sensor and current sensor are input into the industrial computer through signal modulation and A/D conversion. 9. The tester according to claim 8, wherein the voltage sensor and the current sensor include three phase voltage sensors and current sensors, one mutual inductance voltage sensor and current sensor, one direct resistance voltage sensor and current sensor. 10. The tester according to claim 1, wherein the test power supply has an output frequency of 52.5Hz.

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