CN108667000B - Ferromagnetic resonance detection and suppression device for large photovoltaic power station - Google Patents
Ferromagnetic resonance detection and suppression device for large photovoltaic power station Download PDFInfo
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- CN108667000B CN108667000B CN201810427924.8A CN201810427924A CN108667000B CN 108667000 B CN108667000 B CN 108667000B CN 201810427924 A CN201810427924 A CN 201810427924A CN 108667000 B CN108667000 B CN 108667000B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
- H02H9/042—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage comprising means to limit the absorbed power or indicate damaged over-voltage protection device
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Abstract
A ferromagnetic resonance detection and suppression device for a large photovoltaic power station comprises an electromagnetic voltage transformer, a sampling voltage regulation module, a data processing module, a control system module and a switching value output module; the sampling voltage regulating module, the data processing module and the control system module are sequentially connected with the switching value output module; the opening triangle of the electromagnetic voltage transformer is connected with a damping resistor, the switching value output module is also connected with a fling-cut switch, and the fling-cut switch is connected with the damping resistor. The invention analyzes the voltage data of the power distribution network by sampling and conditioning the voltage of the PT secondary side and judging whether resonance occurs. If resonance occurs, the control signal is output to drive the switch action of the contactor through the communication with the ARM chip, so that the effective switching of the damping resistor is realized to complete the suppression of ferromagnetic resonance, resonance information is displayed on an LCD screen, and the resonance information is stored in an SD card and uploaded to an upper computer. The method has the advantages of high response speed, low cost, low power consumption, reliable operation and the like.
Description
Technical Field
The invention relates to a ferromagnetic resonance detection and suppression device, in particular to a ferromagnetic resonance detection and suppression device for a large photovoltaic power station based on a DSP (digital signal Processor) and ARM (Advanced RISC Machines) structure, and belongs to the technical field of new energy distributed power generation and transmission.
Background
At present, because of the limitation of factors such as equipment manufacturing technology and operation cost, the traditional electromagnetic voltage transformer (PT) is still widely adopted on a substation bus in a 35kV neutral ungrounded distribution network system to monitor the insulation state of electrical equipment. When the system runs normally, the three-phase voltage is basically balanced, and the displacement voltage of a neutral point is very small. However, in the electromagnetic energy transient conversion process caused by some switching operations or faults, the nonlinear excitation inductor of the PT works to a saturated state, and the inductive reactance is reduced. If the excitation inductance of the PT is matched with the ground capacitance parameter of the system (mainly, the ground capacitance of the outgoing line) to form a nonlinear resonance circuit, a ferromagnetic resonance phenomenon occurs, and further a ferromagnetic resonance overvoltage is generated. Since the ferroresonance depends on the grid structure, the operation mode, and the device characteristic parameters of the system, the system may have high-frequency, fundamental frequency, crossover resonance, or lower-frequency resonance.
In a large-scale photovoltaic grid-connected power generation system in China, a power supply line has the characteristic that an air-insulated overhead line is replaced by a solid-insulated cable line. With the increase of cable outlet loops and the increase of transmission distance, the capacitance-to-ground current of the system is multiplied. If the single-phase grounding capacitance current in a 35kV power grid is more than 10A, a neutral point grounding mode through an arc suppression coil is required to be adopted. However, the operation mode of the photovoltaic power station is flexible, and when the circuit is switched, the capacitance current of the system is often changed, so that the tuning mode of the arc suppression coil is influenced, and the arc cannot be effectively suppressed.
Under the background of large-scale photovoltaic infiltration, the risk of resonance overvoltage of a power distribution network is aggravated, and the accidents of fusing, explosion and even direct burning of a high-voltage fuse of a voltage transformer occur frequently; but also makes the cause of such accidents more complicated.
Therefore, the research on the ferromagnetic resonance detection of the large photovoltaic power station and the development of the resonance elimination device have important theoretical value and engineering practice significance for improving the safety stability and the power supply reliability of the power distribution network and enhancing the self-healing capacity of the power grid.
Disclosure of Invention
The invention aims to provide a ferromagnetic resonance detection and suppression device for a large photovoltaic power station, and a damping resistor is connected to a PT opening corner to increase the damping of resonance, so that the aim of effectively suppressing ferromagnetic resonance is fulfilled.
The technical scheme adopted by the invention for solving the technical problems is as follows: the utility model provides a large-scale photovoltaic power plant ferroresonance detects and suppression device, includes electromagnetic type voltage transformer, its characterized in that: the device also comprises a sampling voltage regulating module, a data processing module, a control system module and a switching value output module; the sampling voltage regulating module is connected with the data processing module, the data processing module is connected with the control system module, and the control system module is connected with the switching value output module; the opening triangle of the electromagnetic voltage transformer is connected with a damping resistor, the switching value output module is also connected with a fling-cut switch, and the fling-cut switch is connected with the damping resistor.
Further, the control system module is connected with an LCD screen and an SD card for storage, and is also connected with an upper computer through remote communication.
The sampling voltage regulating module has the main function of sampling and conditioning the voltage collected from the secondary side of the electromagnetic voltage transformer (PT for short) and converting the voltage into the level which can be received by an analog-to-digital conversion (ADC for short) pin of the data processing module (DSP for short), because the PT secondary side considers that the allowance is the bipolar voltage with the maximum effective value of 110V, and the ADC pin of the DSP connected with the output end of the sampling voltage regulating module can only process the unipolar voltage of 0-3.3V, the voltage sampled from the PT secondary side must be firstly converted into the range of 0-3.3V and then sent to the DSP for processing. Meanwhile, a link with an isolation function is needed to ensure that the field signal and the control system are not interfered with each other.
The data processing module has the main functions of completing A/D conversion of an input 0-3.3V direct current analog signal and data processing of the input signal, and analyzing and judging whether ferromagnetic resonance occurs or not on the basis.
The control system module mainly has the functions of acquiring an analysis result of the data processing module, sending a corresponding control signal to the switching value output module according to the analysis result, and simultaneously displaying the analysis result through an LCD screen, storing the analysis result through an SD card and uploading the analysis result to an upper computer through remote communication. The core part of the control system module selects S3C2440 as a control chip.
The method is applied to the suppression of ferromagnetic resonance of a large photovoltaic power station, and the voltage data of the power distribution network is analyzed and whether resonance occurs or not is judged by sampling and conditioning the voltage of the PT secondary side and utilizing the DSP to realize a fast Fourier algorithm. If resonance occurs, the control signal is output to drive the switching switch to act through communication with the ARM chip, so that effective switching of the damping resistor is achieved, ferromagnetic resonance is restrained, resonance information is displayed on an LCD screen, and the resonance information is stored in an SD card and uploaded to an upper computer. The invention has the advantages of high response speed, low cost, low power consumption, reliable operation and the like, and has good application prospect.
The invention is based on DSP and ARM microprocessor, utilizes DSP kernel high-efficiency mathematical operation and signal processing function to quickly judge the generation of ferromagnetic resonance, integrates the functions of inhibiting ferromagnetic resonance, LCD display, SD card storage and remote sending of relevant information to an upper computer into an ARM chip, and adopts an embedded solution scheme combining the strong mathematical operation capability of DSP and the integration and control capability of ARM.
The invention utilizes the twiddle factor W in DFT (discrete Fourier transform) algorithmN knThe method has symmetry and periodicity to detect the occurrence of ferroresonance, and synthesizes long-sequence DFTs step by step through short-sequence DFTs, namely, large-scale transformation is completed by utilizing a plurality of small easily-realized transformations to reduce the operation times and improve the operation speed.
Drawings
Fig. 1 is a structural diagram of a ferroresonance detection and suppression device system of a large photovoltaic power station.
Fig. 2 is a structural diagram of the sampling voltage regulating module of the present invention.
In the figure: 1-sampling voltage regulating module, 2-data processing module, 3-control system module, 4-switching value output module, 5-power supply module, 6-electromagnetic voltage transformer, 7-fling-cut switch, 8-second-stage voltage follower, 9-integrated operational amplifier, 10-direct current power supply, R1Sampling resistance, R2Voltage-dividing resistor, R3A resistance, R4resistance-B, R5resistance-C, R6resistance-D, R7-a current limiting resistor.
Detailed Description
The present invention will be further described below with reference to the accompanying drawings. As shown in fig. 1: the utility model provides a large-scale photovoltaic power plant ferroresonance detects and suppression device, includes electromagnetic type voltage transformer 6, its characterized in that: the device also comprises a sampling voltage regulating module 1, a data processing module 2, a control system module 3 and a switching value output module 4; the sampling voltage regulating module 1 is connected with the data processing module 2, the data processing module 2 is connected with the control system module 3, and the control system module 3 is connected with the switching value output module 4; the opening triangle of the electromagnetic voltage transformer 6 is connected with a damping resistor, the switching value output module 4 is also connected with a fling-cut switch 7, and the fling-cut switch 7 is connected with the damping resistor.
The control system module 3 is connected with an LCD screen and an SD card for storage, and the control system module 3 is also connected with a DM9000 network card and an Ethernet which is connected with an upper computer.
The device also comprises a power supply module 5, wherein the power supply module 5 is connected with the sampling voltage regulating module 1, the data processing module 2, the control system module 3 and the switching value output module 4 to provide working power supplies for the sampling voltage regulating module 1, the data processing module 2, the control system module 3 and the switching value output module 4. The device adopts a 24V contactor as a switching switch to control the switching-in and switching-off of the damping resistor at the triangular opening of the voltage transformer.
As shown in fig. 2: the sampling voltage regulating module comprises a first-stage voltage dividing element, a second-stage voltage follower and a third-stage voltage biasing element; the first stage voltage dividing element is composed of a sampling resistor R1And a voltage dividing resistor R2Composition, sampling resistance R1And a voltage dividing resistor R2One end of the sampling resistor R is respectively connected with the secondary side of the electromagnetic voltage transformer1And a voltage dividing resistor R2The other end of the first stage voltage follower 8 is connected with the second stage voltage follower; the third stage voltage bias element is composed of an A resistor R3B resistance R4C resistance R5D resistance R6A DC power supply 10 and an integrated operational amplifier 9, an A resistor R3And B resistance R4Are all connected with the cathode of the integrated operational amplifier 9, and an A resistor R3The other end of the resistor B is grounded, and a resistor B R4The other end of the C resistor R is connected with the output end of the integrated operational amplifier 95Connected with the second stage voltage follower 8, a DC power supply 10 and a D resistor R6Connection, C resistance R5And D resistance R6The other end of the integrated transporting and placing device 9 is connected with the integrated transporting and placing device; the output end of the integrated operational amplifier 9 is connected with a current-limiting resistor R7。
The primary voltage division element has the main functions of sampling and dividing the voltage of the PT secondary side and ensuring that the output voltage range is-1.5V. The second-stage voltage follower mainly plays a role in isolating the field signal of the power system from the device, and meanwhile, the amplitude of the signal is not changed. The third-stage voltage biasing element mainly has the function of converting bipolar voltage-1.5V output by the voltage follower into unipolar voltage of 0-3V so as to enable the bipolar voltage to be received by the DSP. Finally the signal passes through a current limiting resistor R7And sending the data to an ADC input pin of the DSP for further operation and processing.
The working process of the invention is roughly as follows: the secondary side of the electromagnetic voltage transformer outputs a bipolar voltage signal of 110V to the sampling and voltage regulating module 1, the sampling and voltage regulating module samples and conditions the voltage signal, the voltage signal is finally converted into a voltage signal of 0-3.3V and sent to an ADC input pin in the data processing module 2, data analysis and processing are carried out, an analysis result is sent to the control system module 3, the control system module uses a commercially available S3C2440 as a control chip, the analysis result is displayed through an LCD screen and stored in an SD card, the analysis result is transmitted to an upper computer through a DM9000 network card in remote communication such as Ethernet, and a corresponding control signal is sent to the switching value output module 4.
When ferromagnetic resonance occurs, the sampled secondary side voltage waveform of the PT is severely distorted, and a large amount of frequency division and high frequency harmonics may be generated. And DFT algorithm software arranged in the data processing module 2 analyzes the voltage waveform of the PT secondary side obtained by sampling to obtain a signal spectrum of the PT secondary side, so that a value of the total harmonic distortion THD is calculated by using the DSP. If THD is higher than the set normal value, ferromagnetic resonance is judged to occur, a control signal is output through a general purpose input/output (GPIO for short) port of the ARM, and a damping resistor is put into the PT opening triangle for a short time to eliminate resonance.
In order to facilitate accurate sampling of frequency division resonance, the number N of sampling points in each period of the DSP is selected to be 210=1024, M =10, thereby selecting the a/D sampling frequency of the DSPf1024 × 5=5.12 kHz.
Claims (5)
1. The utility model provides a large-scale photovoltaic power plant ferroresonance detects and suppression device, includes electromagnetic type voltage transformer, its characterized in that: the device also comprises a sampling voltage regulating module (1), a data processing module (2), a control system module (3) and a switching value output module (4); the sampling voltage regulating module (1) is connected to the data processing module (2), the data processing module (2) is connected to the control system module (3), and the control system module (3) is connected to the switching value output module (4); the opening triangle of the electromagnetic voltage transformer (6) is connected with a damping resistor, the switching value output module (4) is also connected with a fling-cut switch (7), and the fling-cut switch (7) is connected with the damping resistor;
the detection and suppression device detects the occurrence of ferromagnetic resonance by utilizing the symmetry and periodicity of a twiddle factor WNkn in a DFT algorithm, gradually synthesizes a long-sequence DFT through a short-sequence DFT, and completes large-scale transformation by utilizing a plurality of small transformations which are easy to realize so as to reduce the operation times and improve the operation speed;
the sampling voltage regulating module samples and conditions the voltage collected from the secondary side of the electromagnetic voltage transformer and converts the voltage into the level which can be received by an analog-to-digital conversion pin of the data processing module, because the PT secondary side considers that the allowance is bipolar voltage with the maximum effective value of 110V, and an ADC pin of a DSP connected with the output end of the sampling voltage regulating module can only process unipolar voltage of 0-3.3V, the voltage sampled from the PT secondary side must be firstly converted into the range of 0-3.3V and then sent to the DSP for processing, and meanwhile, a link with an isolation function is needed to ensure that a field signal and a control system are not interfered with each other.
2. The ferroresonance detection and suppression device for a large photovoltaic power plant of claim 1, wherein: the sampling voltage regulating module comprises a first-stage voltage dividing element, a second-stage voltage follower (8) and a third-stage voltage biasing element; the first-stage voltage division element consists of a sampling resistor (R1) and a voltage division resistor (R2), one ends of the sampling resistor (R1) and the voltage division resistor (R2) are respectively connected with the secondary side of the electromagnetic voltage transformer, and the other ends of the sampling resistor (R1) and the voltage division resistor (R2) are connected with the second-stage voltage follower (8); the third-stage voltage biasing element consists of an A resistor (R3), a B resistor (R4), a C resistor (R5), a D resistor (R6), a direct current power supply (10) and an integrated operational amplifier (9), wherein the A resistor (R3) and the B resistor (R4) are both connected with the negative electrode of the integrated operational amplifier (9), the other end of the A resistor (R3) is grounded, the other end of the B resistor (R4) is connected with the output end of the integrated operational amplifier (9), the C resistor (R5) is connected with the second-stage voltage follower (8), the direct current power supply (10) is connected with the D resistor (R6), and the other ends of the C resistor (R5) and the D resistor (R6) are connected with the integrated operational amplifier (9); the output end of the integrated operational amplifier (9) is connected with a current-limiting resistor (R7).
3. The ferroresonance detection and suppression device for large photovoltaic power plants of claim 2, wherein: the control system module (3) is connected with an LCD screen and an SD card for storage, and the control system module (3) is also connected with an Ethernet through a DM9000 network card and connected with an upper computer.
4. A large photovoltaic power plant ferroresonance detection and suppression apparatus as claimed in claim 1, 2 or 3, wherein: the device also comprises a power supply module (5), wherein the power supply module (5) is connected with the sampling voltage regulating module (1), the data processing module (2), the control system module (3) and the switching value output module (4).
5. The ferroresonance detection and suppression device for large photovoltaic power plants of claim 4, wherein: the control system module (3) uses a commercially available S3C2440 as a control chip; the switching switch (7) is a 24V contactor.
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