CN114237075A - Electromagnetic switch closing control method capable of intelligently identifying load - Google Patents
Electromagnetic switch closing control method capable of intelligently identifying load Download PDFInfo
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Abstract
The invention relates to a switching-on control method of an electromagnetic switch capable of intelligently identifying a load, which comprises the following steps: step S1, analyzing the relation between the contact closing phase angle and the load power factor angle and the inrush current; step S2, acquiring the optimal switching-on phase angle for suppressing inrush current under different loads of the electromagnetic switch based on the relation between the switching-on phase angle of the contact and the load power factor angle as well as the inrush current; s3, performing closing experiment simulation on loads with different power factor angles by using a circuit simulation model of the electromagnetic switch contact loop to obtain the first current half-wave time of inductive loads and capacitive loads under different power factor angles, and sorting data into a line graph; and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line graph and the initial closing first current half-wave time of the electromagnetic switch, and controlling the electromagnetic switch based on the optimal closing phase angle for suppressing the inrush current under the corresponding load obtained in the step S2. The invention can effectively realize that the electromagnetic switch does not need to be replaced when the load changes, so that the electromagnetic switch can effectively inhibit the inrush current when controlling different loads.
Description
Technical Field
The invention relates to the field of intelligent control of electromagnetic switches, in particular to a closing control method of an electromagnetic switch capable of intelligently identifying a load.
Background
With the rise of new energy fields such as solar energy, wind power and the like, the market has higher and higher requirements on switching appliances, wherein the electromagnetic switch taking the single chip microcomputer as a control core can perform dynamic optimization control on attraction, holding and breaking in the whole process, and has wide application prospect. Under the background of development of a smart power grid and an internet of things, control objects of an electromagnetic switch are not simplified any more, when a load is inductive or capacitive, inrush current which exceeds normal current by several times may be generated when the electromagnetic switch is switched on, and damage to primary equipment, misoperation of a protection device and the like may be caused by excessive inrush current.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a method for controlling closing of an electromagnetic switch capable of intelligently identifying a load, so that the electromagnetic switch does not need to be replaced when the load changes, and the electromagnetic switch can effectively suppress an inrush current when controlling different loads.
In order to achieve the purpose, the invention adopts the following technical scheme:
a switching-on control method for an electromagnetic switch capable of intelligently identifying a load comprises the following steps:
step S1, analyzing the relation between the contact closing phase angle and the load power factor angle and the inrush current;
step S2, acquiring the optimal switching-on phase angle for suppressing inrush current under different loads of the electromagnetic switch based on the relation between the switching-on phase angle of the contact and the load power factor angle as well as the inrush current;
s3, performing closing experiment simulation on loads with different power factor angles by using a circuit simulation model of the electromagnetic switch contact loop to obtain the first current half-wave time of inductive loads and capacitive loads under different power factor angles, and sorting data into a line graph;
and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line graph and the initial switching-on first current half-wave time of the electromagnetic switch, and controlling the electromagnetic switch based on the optimal switching-on phase angle for suppressing inrush current under the corresponding load obtained in the step S2 to realize inrush current-free switching-on under different loads.
Further, the step S1 specifically includes:
when the control object of the electromagnetic switch is a resistance-capacitance load, the contact is equivalent to an ideal switch, the resistance-capacitance load is equivalent to a resistor R and a capacitor C, a contact loop is simplified to an ideal circuit for controlling the resistance-capacitance load for the ideal switch under an alternating current power supply, and a corresponding circuit differential equation in a closing process is as follows, wherein ucIs the capacitor voltage, Um is the power supply voltage amplitude, and alpha is the switch-on initial phase angle
The conversion of the differential equation reduces the circuit current in the closing process as follows, wherein,
is the load power factor angle of the circuit;
as can be seen from the analysis formula (2), the influence of the transient component is most obvious at the initial stage of switching on, and the transient component gradually approaches zero with the lapse of time; the method has the advantages that the transient component is always zero by controlling the initial phase angle alpha of the switch-on, so that the purpose of eliminating the inrush current is achieved, namely, the condition of eliminating the inrush current by the resistance-capacitance load is as follows:
similar to the derivation of the resistance-capacitance load, the equivalent approximate analysis is carried out on the contact loop of the resistance-capacitance load, and the differential equation is as follows:
simplifying a differential equation of the resistance-inductance load, wherein the circuit current in the closing process is as follows:
similarly, for the purpose of eliminating the inrush current, the transient process should be controlled to be zero, and the condition for eliminating the inrush current by the resistive load is as follows:
further, the step S2 is specifically:
the method comprises the steps of utilizing a circuit simulation model of an electromagnetic switch contact loop to carry out closing experiment simulation on loads with different power factor angles, and recording the first half-wave time t of contact current after closingbb＝tb-ta；taTo start the closing moment of the current, tbThe first zero-crossing point moment of the closed current;
at an initial closing phase angle alpha0When the angle is 45 degrees, recording the first current half-wave time of the inductive load and the capacitive load under different power factor angles, sorting the data into a line graph, and analyzing to obtain the first current half-wave time corresponding to different loads; reading out the power factor angle of the load through a line graph
And then the corresponding optimal closing phase angle is adjusted.
Further, the deviation of the load power factor angle identified in step S2 requires further judgment of the inrush current suppression condition, when the rc load and the rc load are adjusted to the optimal closing phase angle, the transient component of the current should be zero, and the current formula in the closing process is simplified to obtain the current expression in the absence of inrush current as follows
And based on the analysis of the formula, the current half-wave time of the resistance-capacitance load and the resistance-inductance load is obtained when the optimal switching-on phase angle for eliminating the inrush current is adjusted.
Further, the step S4 is specifically: when the power supply of the coil control loop is normal, a power-on preparation signal is marked as t0, then the voltage zero point of the contact loop is detected, and when t is1After the zero point of the contact voltage is detected, the operation time delay program is started, and the time delay t is delayedd＝t2-t1，t3Is the inherent operating time of the contactor, t4The time t5 is the time of completion of closing, which is the voltage zero point before the time of completion of closing.
Compared with the prior art, the invention has the following beneficial effects:
1. when the load changes, the electromagnetic switch does not need to be replaced, so that the electromagnetic switch can effectively identify the load when controlling different loads, and the control strategy is intelligently adjusted, so that the intelligent load-adjusting system can better adapt to the market with more and more diversified loads;
2. according to the invention, after the load type and the power factor angle are identified, the zero point of the contact voltage is detected during closing, the action delay of the electromagnetic switch is set, so that the contact voltage phase during closing is the optimal closing phase angle, and the closing inrush current is effectively inhibited.
Drawings
FIG. 1 illustrates a first half-wave time of contact current after closing in an embodiment of the present invention;
FIG. 2 illustrates a first half-wave time of contact current under different loads at a fixed 45 degree closing in one embodiment of the present invention;
FIG. 3 is a timing diagram illustrating control operations according to an embodiment of the present invention;
fig. 4 is a flow chart of phase angle adjustment according to an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
Referring to fig. 1, the present invention provides a closing control method for an electromagnetic switch capable of intelligently identifying a load, including the following steps:
step S1, analyzing the relation between the contact closing phase angle and the load power factor angle and the inrush current;
step S2, acquiring the optimal switching-on phase angle for suppressing inrush current under different loads of the electromagnetic switch based on the relation between the switching-on phase angle of the contact and the load power factor angle as well as the inrush current;
s3, performing closing experiment simulation on loads with different power factor angles by using a circuit simulation model of the electromagnetic switch contact loop to obtain the first current half-wave time of inductive loads and capacitive loads under different power factor angles, and sorting data into a line graph;
and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line graph and the initial switching-on first current half-wave time of the electromagnetic switch, and controlling the electromagnetic switch based on the optimal switching-on phase angle for suppressing inrush current under the corresponding load obtained in the step S2 to realize inrush current-free switching-on under different loads.
In this embodiment, step S1 specifically includes:
when the control object of the electromagnetic switch is a resistance-capacitance load, the contact can be equivalent to an ideal switch, the resistance-capacitance load is equivalent to a resistor R and a capacitor C, a contact loop is simplified to an ideal circuit for controlling the resistance-capacitance load for the ideal switch under an alternating current power supply, and a corresponding circuit differential equation in a closing process is as follows, wherein ucThe voltage is the capacitor voltage, Um is the power voltage amplitude, and alpha is the initial phase angle of switch closing.
The circuit current of the closing process can be obtained by converting and simplifying the differential equation, wherein,
is the load power factor angle of the circuit.
As can be seen from the analysis formula (2), the influence of the transient component is most significant at the time of initial closing, and the transient component gradually approaches zero with the passage of time. By controlling the initial closing phase angle alpha, the transient component can be zero, so that the purpose of eliminating the inrush current is achieved, namely the condition of eliminating the inrush current by the resistance-capacitance load is as follows.
Similar to the derivation of the resistance-capacitance load, the equivalent approximation analysis is performed on the contact loop of the resistance-capacitance load, and the differential equation is as follows.
The differential equation of the resistance-inductance load is simplified, and the circuit current of the closing process is as follows.
Similarly, for the purpose of eliminating the inrush current, the transient should be controlled to zero, and the condition for eliminating the inrush current by the resistive load is as follows.
And obtaining the optimal closing phase angle under the resistance-capacitance load and the resistance-inductance load by the deduction, and analyzing the load identification in the next step.
In this embodiment, step S3 specifically includes:
utilizing a circuit simulation model of a contact loop to perform closing experiment simulation on loads with different power factor angles, and recording the first half-wave time of contact current after closing, as shown in figure 1, taTo start the closing moment of the current, tbFor the first zero-crossing moment of the closed current, half-wave time tbb＝tb-ta。
At an initial closing phase angle alpha0At 45 deg., the first current half-wave times of inductive and capacitive loads at different power factor angles are recorded and the data are arranged into a line graph as shown in fig. 2 below. When the switch is switched on under the phase angle, the first half-wave time of the current of the pure resistive load is 7.5 ms. The current of the inductive load lags behind the voltage, the first half-wave time of the current is more than 7.5ms, the current of the capacitive load just reverses, and the first half-wave time of the current is less than 7.5ms due to the current leading the voltage. From this feature, the nature of the load can be identified. While the load property is identified, the power factor angle of the load can be read through a line graph
And then the optimal closing phase angle is adjusted.
In the actual closing process, errors may be caused by factors such as data acquisition, so that the load power factor angle identified through the above steps has a deviation, and the suppression condition of the inrush current needs to be further judged. When the resistance-capacitance load and the resistance-inductance load are adjusted to the optimal closing phase angle, the transient component of the current should be zero, the current formula of the closing process is simplified, and the current expression without inrush current can be obtained as follows.
From the above analysis, when the optimal closing phase angle for eliminating inrush current is adjusted, the half-wave time of the current of the resistive-capacitive load and the half-wave time of the current of the resistive-inductive load should be 5ms and 10ms, respectively, which is the standard time without inrush current. The closer to the inrush current-free standard time, the better the inrush current suppression condition is, and the inrush current suppression condition of the load can be determined according to the situation.
In the present embodiment, the control timing of the electromagnetic switch is represented by t when the power supply of the coil control circuit is normal as shown in fig. 30Sending a power-on preparation signal, then starting to detect the voltage zero point of a contact loop, and when t1After the zero point of the contact voltage is detected, the operation time delay program is started, and the time delay t is delayedd＝t2-t1，t3The contactor proper operation time is t4, which is the voltage zero point before the closing completion time, and t5, which is the closing completion time.
And (3) arranging the phase angle adjusting step into a flow chart, considering factors such as actual sampling errors and the like as shown in the following figure 4, when the difference value between the half-wave time and the corresponding standard time without inrush current is within 0.2ms, considering that the inrush current is fully inhibited, and finishing the adjustment.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.
Claims (5)
1. A control method for closing an electromagnetic switch capable of intelligently identifying a load is characterized by comprising the following steps:
step S1, analyzing the relation between the contact closing phase angle and the load power factor angle and the inrush current;
step S2, acquiring the optimal switching-on phase angle for suppressing inrush current under different loads of the electromagnetic switch based on the relation between the switching-on phase angle of the contact and the load power factor angle as well as the inrush current;
s3, performing closing experiment simulation on loads with different power factor angles by using a circuit simulation model of the electromagnetic switch contact loop to obtain the first current half-wave time of inductive loads and capacitive loads under different power factor angles, and sorting data into a line graph;
and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line graph and the initial switching-on first current half-wave time of the electromagnetic switch, and controlling the electromagnetic switch based on the optimal switching-on phase angle for suppressing inrush current under the corresponding load obtained in the step S2 to realize inrush current-free switching-on under different loads.
2. The electromagnetic switch closing control method for intelligently identifying the load according to claim 1, wherein the step S1 specifically comprises:
when the control object of the electromagnetic switch is a resistance-capacitance load, the contact is equivalent to an ideal switch, the resistance-capacitance load is equivalent to a resistor R and a capacitor C, a contact loop is simplified to an ideal circuit for controlling the resistance-capacitance load for the ideal switch under an alternating current power supply, and a corresponding circuit differential equation in a closing process is as follows, wherein ucIs the capacitor voltage, Um is the power supply voltage amplitude, and alpha is the switch-on initial phase angle
The conversion of the differential equation reduces the circuit current in the closing process as follows, wherein,
is the load power factor angle of the circuit;
as can be seen from the analysis formula (2), the influence of the transient component is most obvious at the initial stage of switching on, and the transient component gradually approaches zero with the lapse of time; the method has the advantages that the transient component is always zero by controlling the initial phase angle alpha of the switch-on, so that the purpose of eliminating the inrush current is achieved, namely, the condition of eliminating the inrush current by the resistance-capacitance load is as follows:
similar to the derivation of the resistance-capacitance load, the equivalent approximate analysis is carried out on the contact loop of the resistance-capacitance load, and the differential equation is as follows:
simplifying a differential equation of the resistance-inductance load, wherein the circuit current in the closing process is as follows:
similarly, for the purpose of eliminating the inrush current, the transient process should be controlled to be zero, and the condition for eliminating the inrush current by the resistive load is as follows:
3. the electromagnetic switch closing control method for intelligently identifying the load according to claim 1, wherein the step S2 specifically comprises:
the method comprises the steps of utilizing a circuit simulation model of an electromagnetic switch contact loop to carry out closing experiment simulation on loads with different power factor angles, and recording the first half-wave time t of contact current after closingbb＝tb-ta；taTo start the closing moment of the current, tbThe first zero-crossing point moment of the closed current;
at an initial closing phase angle alpha0When the power factor angle is 45 degrees, recording the first current half-wave time of the inductive load and the capacitive load under different power factor angles, sorting the data into a line graph, and analyzing to obtain the first current half-wave time corresponding to different loads; reading by means of a line graphPower factor angle of load
And then the corresponding optimal closing phase angle is adjusted.
4. The method of claim 1, wherein the load power factor angle identified in step S2 has a deviation, and further judgment on the suppression of inrush current is required, when the rc load and the rc load are adjusted to the optimal switching phase angle, the transient component of current should be zero, and the current formula of the switching process is simplified to obtain the current expression without inrush current as follows
And based on the analysis of the formula, the current half-wave time of the resistance-capacitance load and the resistance-inductance load is obtained when the optimal switching-on phase angle for eliminating the inrush current is adjusted.
5. The electromagnetic switch closing control method for intelligently identifying the load according to claim 1, wherein the step S4 specifically comprises: when the power supply of the coil control loop is normal, a power-on preparation signal is marked as t0, then the voltage zero point of the contact loop is detected, and when t is1After the zero point of the contact voltage is detected, the operation time delay program is started, and the time delay t is delayedd＝t2-t1，t3Is the inherent operating time of the contactor, t4The time t5 is the time of completion of closing, which is the voltage zero point before the time of completion of closing.
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