Correction method of zero-crossing switching time of intelligent capacitor

Abstract

The invention proposes a correction method for the zero-crossing switching time of an intelligent capacitor, and belongs to the technical field of capacitor switching. The closing action time sequence and the disconnection action time sequence of a relay at different temperatures are stored in a main control chip; the main control chip obtains a reactive compensation signal according to power grid operation data and a reactive compensation algorithm, and the reactive compensation signal drives the relay to close or disconnect to switch in or out of the capacitor; the closing action time sequence of the relay is corrected by using the closing action error compensation; the disconnection action time sequence of the relay is corrected by using the disconnection action error compensation; the influence of external factors on the closing action time and the disconnection action time of the relay is effectively eliminated, the zero-crossing switching of the capacitor is guaranteed to the greatest extent, the closing inrush current and the disconnection arc are effectively reduced, and the operation safety and service life of the capacitor and the relay are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of capacitor switching, in particular to a method for correcting the zero-crossing switching time of an intelligent capacitor. Background Art

[0002] Low-voltage reactive power compensation is an essential technology for improving power quality in low-voltage power distribution systems. Most existing technologies use capacitors to achieve reactive power compensation, which is achieved by collecting and calculating grid parameters and switching capacitors through switch control circuits.

[0003] At present, the most widely used reactive power compensation device in 380V distribution network is low-voltage intelligent capacitor, which is low in cost and favored by customers. There are two main types of switching elements used in low-voltage intelligent capacitors: one is a composite switch composed of thyristor and relay, and the other is a synchronous switch directly composed of contactor or relay. The former is more expensive, and the thyristor has poor overcurrent and overvoltage capabilities and is easy to be destroyed. The latter has the advantages of low cost, small inrush current, long life, etc., and the control is relatively complex. Synchronous switches are widely used in intelligent capacitors due to their low cost, high voltage level, high power and other advantages.

[0004] The opening and closing time of contactors and relays is dispersed and affected by factors such as production process, operating voltage, grid frequency, ambient temperature, and mechanical loss status. In order to ensure that the voltage of the smart capacitor is closed at zero crossing and the current is disconnected at zero crossing, it is necessary to compensate the action time of the synchronous switch online. The patented "Low-voltage Contact Switch Adaptive Zero Crossing Switching Driver" (patent number: CN201410311664.X) adjusts the switching delay time in real time according to the feedback of the relay opening and closing time to compensate for the change in the relay action time. This can only compensate for the error caused by mechanical loss under the same working environment. In fact, the difference between two consecutive relay action times due to mechanical loss is negligible, and other factors affect the relay action time. The patent "Intelligent capacitor with online adaptive zero-crossing switching correction" (patent number: CN201410781858.6) uses a closing and closing detection module to detect the closing and closing moments of the magnetic latching relay, and uses a single-chip microcomputer to correct the closing and closing driving moments of the magnetic latching relay. Its principle is actually similar to that of patent CN201410311664.X, which also adjusts the switching delay time in real time based on the feedback of the relay's opening and closing moments to compensate for the change in the relay's action time. The above method may be feasible in laboratory verification, but in actual industrial environment applications, it not only cannot solve the problem of the dispersion of the relay's action time, but also brings greater uncertainty errors.

[0005] In engineering applications, the switching of capacitors for reactive power compensation changes with the load. Generally, the capacitors are closed and operated when the inductive loads such as engineering motors start running and cause reactive power shortages. When the production line stops at the factory, the capacitors are shut down. The ambient temperature changes when the capacitors are switched on and off, and there may be large differences, especially in the north and plateau areas. Therefore, in the short term, the capacitor switching switch is most affected by temperature and less affected by mechanical losses.

[0006] Therefore, it is necessary to solve the dispersion problem of relay action time and consider a variety of factors comprehensively, so as to truly realize the online adaptive zero-crossing switching correction of the relay. Summary of the invention

[0007] In view of this, the present invention proposes a correction method for the zero-crossing switching time of an intelligent capacitor, and provides a capacitor zero-crossing switching technology based on comprehensive factors, which is mainly used for the voltage zero-crossing synchronous input and current zero-crossing synchronous exit of a low-voltage capacitor.

[0008] The technical solution of the present invention is implemented as follows: a correction method for the zero-crossing switching time of an intelligent capacitor, characterized in that: the correction method includes: recording the closing action time and the opening action time of the relay at different temperatures, obtaining a closing action time sequence according to the measured closing action time, and obtaining a disconnection action time sequence according to the measured disconnection action time; and storing the closing action time sequence and the disconnection action time sequence in a main control chip; real-time monitoring of power grid operation data, the main control chip obtains a reactive compensation signal according to the power grid operation data and a reactive compensation algorithm, and the reactive compensation signal drives the relay to close or open to put in or withdraw the capacitor to achieve reactive compensation; when putting in the capacitor, the closing action time of the relay at the real-time ambient temperature of the closing is obtained from the closing action time sequence by using a linear interpolation method, and the power grid voltage cycle minus the closing action time is obtained to put in Delay time, after the voltage first crosses zero point and delays the input delay time, the main control chip sends a relay closing command, the relay executes the closing action, completes the input of the capacitor, and the relay closing action error is fed back from the relay closing moment, and the closing action error is used to correct the relay closing action time series; when exiting the capacitor, the disconnection action time of the relay at the real-time ambient temperature of the disconnection is obtained from the disconnection time series using a linear interpolation method, and the exit delay time is obtained by subtracting the disconnection action time from the grid voltage cycle. After the voltage first crosses zero point and delays the exit delay time and a quarter of the voltage cycle, the main control chip sends a relay disconnection command, the relay executes the disconnection action, completes the exit of the capacitor, and the relay disconnection action error is fed back from the relay disconnection moment, and the disconnection action error is used to correct the relay disconnection action time series.

[0009] On the basis of the above technical scheme, preferably, the method for obtaining the closing action time series and the opening action time series is as follows: the temperature is in the range of -20°C to 60°C, starting from -20°C, the closing action time and the opening action time of the relay are tested several times every 5°C to obtain the average closing action time and the average opening action time at the corresponding temperature; the average closing action time values ​​obtained by testing at different temperatures are combined into a closing action time series, and the average opening action time values ​​obtained by testing at different temperatures are combined into a opening action time series.

[0010] Based on the above technical scheme, preferably, the real-time data of the power grid includes power grid voltage, power grid current, power grid active power, power grid reactive power, power grid power factor and power grid frequency, and the main control chip executes a reactive compensation algorithm according to the reactive power and power grid power factor of the power grid to decide whether to put capacitors into operation or withdraw capacitors.

[0011] On the basis of the above technical solution, preferably, when the capacitor is put into operation, the main control chip obtains the grid frequency and the real-time ambient temperature of the closing, and obtains the closing action time of the relay under the real-time ambient temperature of the closing according to the closing action time series by using the linear interpolation method, and obtains the relay input delay time according to the grid frequency and the closing action time, wherein the grid frequency is f, the real-time ambient temperature of the closing is t, and the closing action time is The input delay time is τ,

[0012] On the basis of the above technical solution, preferably, the main control chip detects the first grid voltage zero crossing point, and immediately starts the first timer and the first timer. The first timer has a delay, and the delay of the first timer is the input delay time τ. After the first timer expires, the main control chip sends a closing pulse, controls the relay to close, and inputs the capacitor.

[0013] On the basis of the above technical solution, preferably, the time when the first timer records the closing moment of the relay is t cp The next grid voltage zero crossing time is According to t cp and The closing action error δT is obtained, The closing action error δT is used to correct the closing action time series of the relay.

[0014] On the basis of the above technical solution, preferably, when exiting the capacitor, the main control chip obtains the grid frequency and the real-time ambient temperature of the disconnection, and obtains the disconnection action time of the relay under the real-time ambient temperature of the disconnection according to the disconnection action time sequence by using the linear interpolation method, and obtains the exit delay time of the relay according to the grid frequency and the disconnection action time, wherein the grid frequency is f, the real-time ambient temperature of the disconnection is t', and the disconnection action time is and the exit delay time is τ',

[0015] On the basis of the above technical solution, preferably, the main control chip detects the first grid voltage zero crossing point, immediately starts the second timer and the second timer, the second timer has a delay, and the delay of the second timer is the exit delay time of After the second timer expires, the main control chip sends a disconnection pulse to control the relay to complete the disconnection and exit the capacitor.

[0016] On the basis of the above technical solution, preferably, the time when the second timer records the disconnection moment of the relay is t cp ' and the next grid voltage zero crossing time According to t cp 'and The disconnection error δT' is obtained. The disconnection action error δT' is used to correct the disconnection action time series of the relay.

[0017] On the basis of the above technical solution, preferably, at the closing real-time temperature t, the closing action time corresponding to the closing action time series is The closing action error is δT, and the corrected closing action time is At the disconnection real-time temperature t, the disconnection action time corresponding to the disconnection action time series is: The disconnection action error is δT', and the corrected disconnection action time is

[0018] The method for correcting the zero-crossing switching time of the intelligent capacitor of the present invention has the following beneficial effects compared with the prior art:

[0019] The present invention comprehensively considers various factors that affect the relay action time, establishes the relay closing action time sequence and the disconnection action time sequence at different temperatures, obtains the corresponding relay closing action time or disconnection action time according to the real-time ambient temperature, and simultaneously utilizes the closing action error and the disconnection action error of the relay to correct the closing action time sequence and the disconnection action time sequence of the relay, effectively eliminating the influence of external factors on the closing action time and the disconnection action time of the relay, ensuring the zero-crossing switching of the capacitor to the greatest extent, effectively reducing the closing inrush current and the disconnection arcing, and greatly improving the operating safety and service life of the capacitor and the relay. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 It is a structural schematic diagram of the zero-crossing switching circuit of the intelligent capacitor of the present invention;

[0022] Figure 2 The present invention is a logic block diagram of a method for correcting the zero-crossing switching time of an intelligent capacitor. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] like Figure 1 and Figure 2 As shown in the figure, the correction method of the zero-crossing switching time of the intelligent capacitor is:

[0025] The method for obtaining the closing action time series is as follows:

[0026] When the temperature is within the range of -20℃~60℃, starting from -20℃, the closing action time of the relay is tested 20 times at 5℃ intervals to obtain the average closing action time at the corresponding temperature; the average closing action time values ​​obtained from tests at different temperatures are combined into a closing action time series.

[0027] The method for obtaining the disconnection action time series is as follows:

[0028] When the temperature is within the range of -20℃~60℃, starting from -20℃, the disconnection action time of the relay is tested 20 times at 5℃ intervals to obtain the average disconnection action time at the corresponding temperature; the average disconnection action time values ​​obtained from tests at different temperatures are combined into a disconnection action time series.

[0029] The above-mentioned closing action time sequence and opening action time sequence are both stored in the main control chip, which is convenient for retrieving the closing action time and opening action time at different temperatures.

[0030] Since the reliable operating temperature of the capacitor is between -20℃ and 60℃, the technical solution measures the closing action time series and the opening action time series of the relay within this temperature range. In this experiment, the applicant conducted 20 experiments at each temperature to obtain the closing action time or the opening action time and then calculated the average value. If more reliable data is to be obtained, the number of experiments can be increased and the temperature interval can be shortened.

[0031] The closing action time and the opening action time are obtained by linear interpolation at the closing real-time ambient temperature and the opening real-time temperature:

[0032] In the technical solution, the closing action time is obtained at the closing real-time temperature or the opening action time is obtained at the opening real-time temperature by using the linear interpolation method. At this time, taking the closing action time series as an example, when the closing real-time temperature is t, if you want to obtain the closing action time The temperature in the closing action time series is t 1 Closing action time The temperature in the closing action time series is t 2 Closing action time where t 1 ≤t <t 2 ,at this time The process of obtaining the disconnection action time using the linear interpolation method according to the disconnection action time series is similar and will not be described in detail here.

[0033] The real-time grid data includes grid voltage, grid current, grid active power, grid reactive power, grid power factor and grid frequency. The main control chip executes a reactive compensation algorithm according to the grid reactive power and grid power factor to obtain a reactive compensation signal. The reactive compensation signal drives the relay to close or open to put the capacitor in or out, thereby realizing reactive compensation.

[0034] When putting capacitors into operation:

[0035] The main control chip obtains the grid frequency and the real-time ambient temperature of the closing, and uses the linear interpolation method to obtain the closing action time of the relay under the real-time ambient temperature of the closing according to the closing action time series. The relay input delay time is obtained according to the grid frequency and closing action time. The grid frequency is f, the real-time ambient temperature of the closing is t, and the closing action time is The closing delay is τ,

[0036] The main control chip detects the first grid voltage zero crossing point and immediately starts the first timer and the first timer. The first timer has a delay, and the delay time of the first timer is the input delay time τ. When the first timer expires, the main control chip immediately sends a closing pulse to control the relay to close and input the capacitor.

[0037] The capacitor is put into operation and the action is completed in one go. In order to further improve the accuracy of the capacitor voltage zero-crossing operation, we introduced the closing action error correction closing action time series.

[0038] Among them, the calculation method of closing action error is as follows:

[0039] The first timer records the time when the relay is closed as t cp and the next grid voltage zero crossing time is According to t cp and The closing action error δT is obtained, The closing action error δT is used to correct the closing action time series.

[0040] The correction method of closing action time is as follows:

[0041] The real-time ambient temperature of closing is t, and the closing action time in the closing action time series is The closing action error is δT, and the corrected closing action time is

[0042] The corrected closing action time is used during the next capacitor input process, and the accuracy of capacitor input is further improved.

[0043] When exiting the capacitor:

[0044] The main control chip obtains the grid frequency and the real-time ambient temperature of the disconnection, and uses the linear interpolation method to obtain the disconnection action time of the relay under the real-time ambient temperature according to the disconnection action time sequence, and obtains the exit delay time of the relay according to the grid frequency and the disconnection action time. The grid frequency is f, the real-time ambient temperature of the disconnection is t', and the disconnection action time is and the exit delay time is τ',

[0045] The main control chip detects the first grid voltage zero crossing point and immediately starts the second timer and the second timer. The second timer has a delay. The delay of the second timer is After the second timer expires, the main control chip sends a disconnection pulse to control the relay to complete the disconnection and exit the capacitor.

[0046] The capacitor is exited and the action is completed in one time. In order to further improve the accuracy of the zero-crossing removal of the capacitor current, we introduce the disconnection action error correction disconnection action time sequence.

[0047] The second timer records the time when the relay disconnects as t cp ' and the next grid voltage zero crossing time According to t cp 'and The disconnection error δT' is obtained. The disconnection action error δT' is used to correct the disconnection action time series.

[0048] The correction method of disconnection action time is as follows:

[0049] The real-time ambient temperature of disconnection is t', and the disconnection action time in the disconnection action time sequence is The disconnection action error is δT', and the corrected disconnection action time is

[0050] The accuracy of capacitor withdrawal is further improved by utilizing the corrected disconnection action time during the next capacitor withdrawal process.

[0051] Figure 1 In the system, the temperature detection circuit is used to obtain the real-time ambient temperature, the zero-crossing detection circuit is used to detect the voltage zero-crossing point, and the cross-collection metering chip obtains the grid voltage, grid current, grid active power, grid reactive power, grid power factor and grid frequency;

[0052] The opening and closing control circuit controls the closing and opening of the relay, and the switch state detection circuit is used to detect the closing and opening of the relay.

[0053] The present invention comprehensively considers various factors that affect the relay action time, establishes the relay closing action time sequence and the disconnection action time sequence at different temperatures, obtains the corresponding relay closing action time or disconnection action time according to the real-time ambient temperature, and simultaneously uses the closing action error and the disconnection action error of the relay closing and disconnecting to correct the closing action time sequence and the disconnection action time sequence of the relay, effectively eliminating the influence of external factors on the closing action time and the disconnection action time of the relay, ensuring the zero-crossing switching of the capacitor to the greatest extent, effectively reducing the closing inrush current and the disconnection arcing, and greatly improving the operating safety and service life of the capacitor and the relay.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for correcting the zero-crossing switching time of an intelligent capacitor, characterized in that: The correction method comprises: Record the closing action time and the opening action time of the relay at different temperatures, obtain the closing action time sequence according to the measured closing action time, and obtain the opening action time sequence according to the measured opening action time; and store the closing action time sequence and the opening action time sequence in the main control chip; Real-time monitoring of grid operation data. The main control chip obtains reactive power compensation signals based on grid operation data and reactive power compensation algorithms. The reactive power compensation signals drive the relays to close or open to put capacitors in or out of the capacitors, thus achieving reactive power compensation. When the capacitor is put into operation, the closing action time of the relay under the real-time ambient temperature of the closing is obtained from the closing action time series by using the linear interpolation method, and the input delay time is obtained by subtracting the closing action time from the grid voltage cycle. After the input delay time is delayed at the first zero crossing point of the voltage, the main control chip issues a relay closing instruction, and the relay executes the closing action to complete the input of the capacitor, and the closing action error of the relay is obtained by feedback from the closing moment of the relay, and the closing action error is used to correct the closing action time series of the relay; When exiting the capacitor, the disconnection action time of the relay under the real-time ambient temperature of the disconnection is obtained from the disconnection time series by using the linear interpolation method, and the exit delay time is obtained by subtracting the disconnection action time from the grid voltage cycle. After the first voltage zero crossing delay of the exit delay time and a quarter of the voltage cycle, the main control chip issues a relay disconnection instruction, and the relay performs the disconnection action to complete the exit of the capacitor, and the relay disconnection action error is obtained by feedback from the relay disconnection moment, and the disconnection action error is used to correct the relay disconnection action time series; The real-time grid data includes grid voltage, grid current, grid active power, grid reactive power, grid power factor and grid frequency. The main control chip executes a reactive compensation algorithm according to the grid reactive power and grid power factor to decide whether to put in or out a capacitor. When the capacitor is put into operation, the main control chip obtains the grid frequency and the real-time ambient temperature of the closing, and obtains the closing action time of the relay under the real-time ambient temperature of the closing according to the closing action time sequence by using the linear interpolation method, and obtains the relay input delay time according to the grid frequency and the closing action time, wherein the grid frequency is f, the real-time ambient temperature of the closing is t, and the closing action time is The input delay time is τ, The main control chip detects the first grid voltage zero crossing point, and immediately starts the first timer and the first timer, the first timer has a delay, and the delay of the first timer is the input delay time τ. After the first timer expires, the main control chip sends a closing pulse to control the relay to close and input the capacitor; The time when the first timer records the closing moment of the relay is t cp and the next grid voltage zero crossing time is According to t cp and The closing action error δT is obtained, The closing action time series of the relay is corrected using the closing action error δT; When the capacitor is exited, the main control chip obtains the grid frequency and the real-time ambient temperature of the disconnection, and obtains the disconnection action time of the relay under the real-time ambient temperature of the disconnection according to the disconnection action time sequence by using the linear interpolation method, and obtains the exit delay time of the relay according to the grid frequency and the disconnection action time, wherein the grid frequency is f, the real-time ambient temperature of the disconnection is t', and the disconnection action time is and the exit delay time is τ', The main control chip detects the first grid voltage zero crossing point, and immediately starts the second timer and the second timer, the second timer has a delay, and the delay of the second timer is After the second timer expires, the main control chip sends a disconnection pulse, the control relay is disconnected, and the capacitor is withdrawn; The second timer records the time t of the relay disconnection moment cp ' and the next grid voltage zero crossing time According to t cp 'and The disconnection error δT' is obtained. The disconnection action time series of the relay is corrected using the disconnection action error δT'; At the closing real-time temperature t, the closing action time corresponding to the closing action time series is: The closing action error is δT, and the corrected closing action time is At the disconnection real-time temperature t, the disconnection action time corresponding to the disconnection action time series is: The disconnection action error is δT', and the corrected disconnection action time is 2. The method for correcting the zero-crossing switching time of the intelligent capacitor according to claim 1, characterized in that: The method for obtaining the closing action time series and the opening action time series is as follows: when the temperature is within the range of -20°C to 60°C, starting from -20°C, the closing action time and the opening action time of the relay are tested several times every 5°C to obtain the average closing action time and the average opening action time at the corresponding temperature; the average closing action time values ​​obtained by the tests at different temperatures are combined into a closing action time series, and the average opening action time values ​​obtained by the tests at different temperatures are combined into a opening action time series.

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