CN114237075B - Electromagnetic switch closing control method for intelligently identifying load - Google Patents
Electromagnetic switch closing control method for intelligently identifying load Download PDFInfo
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Abstract
The invention relates to an electromagnetic switch closing control method for intelligently identifying a load, which comprises the following steps: s1, analyzing the relation between a contact closing phase angle, a load power factor angle and a surge current; step S2, based on the relation between the contact closing phase angle and the load power factor angle and the surge current, obtaining the optimal closing phase angle for inhibiting the surge current under different loads of the electromagnetic switch; s3, performing switching-on experimental simulation on loads with different power factor angles by using a circuit simulation model of an electromagnetic switch contact loop, obtaining first current half-wave time of inductive loads and capacitive loads under different power factor angles, and arranging data into a line graph; and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line diagram 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 inhibiting 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 an electromagnetic switch closing control method for intelligently identifying loads.
Background
With the rising of new energy fields such as solar energy, wind power and the like, the requirements of the market on switching appliances are also higher and higher, wherein an electromagnetic switch taking a singlechip as a control core can perform overall process dynamic optimization control on suction, holding and breaking, and the application prospect is wide. Under the background of development of smart power grids and the Internet of things, control objects of the electromagnetic switch are not unified, when a load is inductive and capacitive, switching-on of the electromagnetic switch can be accompanied by surge current which exceeds the normal current by times, and excessive surge current can cause damage such as instability of a circuit, damage to primary equipment, misoperation of a protection device and the like, and the traditional random switching-on phase angle switching-on control scheme is difficult to meet higher and higher power quality requirements, so that a proper switching-on control strategy is selected to solve the problem.
Disclosure of Invention
Therefore, the invention aims to provide an electromagnetic switch closing control method for intelligently identifying loads, which does not need to replace an electromagnetic switch when the loads change, so that the electromagnetic switch can effectively inhibit inrush current when controlling different loads.
In order to achieve the above purpose, the invention adopts the following technical scheme:
an electromagnetic switch closing control method for intelligently identifying a load comprises the following steps:
s1, analyzing the relation between a contact closing phase angle, a load power factor angle and a surge current;
step S2, based on the relation between the contact closing phase angle and the load power factor angle and the surge current, obtaining the optimal closing phase angle for inhibiting the surge current under different loads of the electromagnetic switch;
s3, performing switching-on experimental simulation on loads with different power factor angles by using a circuit simulation model of an electromagnetic switch contact loop, obtaining first current half-wave time of inductive loads and capacitive loads under different power factor angles, and arranging data into a line graph;
and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line diagram 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, so as to realize no-inrush current closing under different loads.
Further, the step S1 specifically includes:
when the control object of the electromagnetic switch is a capacitive load, the contact is equivalent to an ideal switch, the capacitive load is equivalent to a resistor R and a capacitor C, and a contact loop is simplified to be an alternating current power supplyThe ideal switch of the lower ideal switch controls the ideal circuit of the capacitive load, and the corresponding differential equation of the circuit in the closing process is as follows, wherein u c Is capacitance voltage, um is power voltage amplitude, alpha is switch closing initial phase angle
The differential equation is reduced to obtain the circuit current of the closing process as follows, wherein,the load power factor angle of the circuit;
analysis formula (2) shows that the transient component has the most obvious influence at the initial time of closing, and the transient component gradually approaches zero along with the time; by controlling the initial phase angle alpha of the closing, the transient component is always zero, so that the purpose of eliminating the surge current is achieved, namely, the conditions of eliminating the surge current by the capacitive load are as follows:
similar to the derivation of the resistive load, the equivalent approximation analysis is performed on the contact loop of the resistive load, and the differential equation is as follows:
the differential equation of the resistive-inductive load is simplified, and the circuit current in the closing process is as follows:
similarly, in order to achieve the purpose of eliminating the inrush current, the transient process should be controlled to be zero, and the conditions for eliminating the inrush current by the inductive load are as follows:
further, the step S2 specifically includes:
by utilizing a circuit simulation model of an electromagnetic switch contact loop, carrying out switching-on experimental simulation on loads with different power factor angles, and recording the first half-wave time t of the contact current after switching-on bb ＝t b -t a ；t a To start the closing time of the current, t b The first zero crossing point moment of the closed current;
at an initial closing phase angle alpha 0 When the power factor angle is 45 DEG, recording the first current half-wave time of inductive load and capacitive load under different power factor angles, arranging the data into a line graph, and analyzing to obtain the first current half-wave corresponding to different loads; reading the power factor angle of the load through the line graphAnd then the corresponding optimal closing phase angle is adjusted.
Further, the load power factor angle identified in step S2 has a deviation, so that it is necessary to further determine the suppression condition of the inrush current, and when the resistive load and the resistive 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, so that the current expression in the absence of the inrush current is as follows
And based on the above analysis, the current half-wave time of the capacitive load and the inductive load is obtained when the optimal closing phase angle for eliminating the inrush current is adjusted.
Further, the step S4 specifically includes: when the power supply of the coil control loop is normal, the coil control loop is recorded as t0 to send out a power-on preparation signal, then the voltage zero point of the contact loop is detected, and when t 1 After detecting the contact voltage zero point at any time, entering an action delay program to delay time t d ＝t 2 -t 1 ，t 3 For the inherent action time of the contactor, t 4 And t5 is the closing completion time, which is the voltage zero point before the closing completion time.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, 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 can be intelligently adjusted, so that the load-changing control system can be better suitable for markets with more and more diversified loads;
2. after the type and the power factor angle of the load are identified, the zero point of the contact voltage is detected during closing, and the action delay of the electromagnetic switch is set, so that the phase of the contact voltage during closing is the optimal closing phase angle, and the closing inrush current is effectively restrained.
Drawings
FIG. 1 is a first half-wave time of a contact current after closing in an embodiment of the present invention;
FIG. 2 shows the first half-wave time of the contact current under different loads when a 45 DEG switch is closed, according to an embodiment of the present invention;
FIG. 3 is a control timing diagram according to an embodiment of the present invention;
FIG. 4 is a phase angle adjustment flow chart in an embodiment of the invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples.
Referring to fig. 1, the invention provides a method for controlling the closing of an electromagnetic switch for intelligently identifying a load, which comprises the following steps:
s1, analyzing the relation between a contact closing phase angle, a load power factor angle and a surge current;
step S2, based on the relation between the contact closing phase angle and the load power factor angle and the surge current, obtaining the optimal closing phase angle for inhibiting the surge current under different loads of the electromagnetic switch;
s3, performing switching-on experimental simulation on loads with different power factor angles by using a circuit simulation model of an electromagnetic switch contact loop, obtaining first current half-wave time of inductive loads and capacitive loads under different power factor angles, and arranging data into a line graph;
and S4, identifying the load type and the power factor angle of the electromagnetic switch based on the line diagram 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, so as to realize no-inrush current closing under different loads.
In this embodiment, step S1 specifically includes:
when the control object of the electromagnetic switch is a capacitive load, the contact is equivalent to an ideal switch, the capacitive load is equivalent to a resistor R and a capacitor C, the contact loop simplifies an ideal circuit for controlling the capacitive load for the ideal switch under the AC power supply, and a corresponding circuit differential equation in the closing process is as follows, wherein u c For capacitor voltage Um is the supply voltage amplitude and α is the switch closing initial phase angle.
The reduction of the differential equation yields the circuit current for the closing process as follows, wherein,is the load power factor angle of the circuit.
Analysis formula (2) shows that the influence of the transient component is most obvious when the switch is initially closed, and the transient component gradually approaches zero as time goes by, so that the influence of the transient component needs to be reduced as much as possible to eliminate the inrush current. By controlling the initial phase angle alpha of the closing, the transient component can be zero, so that the purpose of eliminating the surge current is achieved, namely the condition of eliminating the surge current by the capacitive load is as follows.
Similar to the derivation of the resistive load, the equivalent approximation analysis is performed on the contact loop of the resistive load, and the differential equation is as follows.
The differential equation of the resistive-inductive load is simplified, and the circuit current in the closing process is as follows.
Similarly, in order to achieve the purpose of eliminating the inrush current, the transient process should be controlled to be zero, and the condition of eliminating the inrush current by the inductive load is as follows.
By the deduction, the optimal closing phase angle under the capacitive load and the inductive load is obtained, and the next step of analysis of load identification is performed.
In this embodiment, step S3 specifically includes:
by utilizing a circuit simulation model of a contact loop, carrying out switching-on experimental simulation on loads with different power factor angles, recording the first half-wave time of the contact current after switching-on, and as shown in figure 1, t a To start the closing time of the current, t b For current after closingFirst zero crossing point moment, half wave time t bb ＝t b -t a 。
At an initial closing phase angle alpha 0 When=45°, the first current half-wave times of the inductive load and the capacitive load at different power factor angles were recorded, and the data were organized into a line graph as shown in fig. 2 below. When closing at this phase angle, the current of the purely resistive load has a first half-wave time of 7.5ms. The inductive load current lags behind the voltage, the first half-wave time of the current is more than 7.5ms, and the capacitive load is opposite, and the first half-wave time of the current is less than 7.5ms due to the current lead voltage. From this feature, the nature of the load can be identified. The power factor angle of the load can be read through the line graph while the nature of the load is identifiedAnd 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 steps has deviation, and the suppression condition of the inrush current needs to be further judged. When the capacitive load and the inductive load are regulated 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, so that the current expression without inrush current can be obtained as follows.
From the above analysis, when the optimal closing phase angle for eliminating the inrush current is adjusted, the current half-wave time of the resistive load and the resistive load should be 5ms and 10ms respectively, which are standard time without the inrush current. The closer to the surge-free standard time, the better the suppression condition of the switching-on surge is, and the surge suppression condition of the load can be judged according to the suppression condition.
In the present embodiment, the control timing of the electromagnetic switch is shown in FIG. 3, and is denoted as t when the power supply of the coil control loop is normal 0 Sending out a power-on preparation signal, then starting to detect the voltage zero point of the contact loop, when t 1 After detecting the contact voltage zero point at any time, entering an action delay program to delay time t d ＝t 2 -t 1 ，t 3 For the intrinsic operation time of the contactor, t4 is the voltage zero point before the closing completion time, and t5 is the closing completion time.
The phase angle adjusting step is arranged into a flow chart, as shown in the following fig. 4, when the half-wave time and the corresponding standard time difference without inrush current are within 0.2ms, the inrush current is considered to be fully suppressed, and the adjustment is finished in consideration of factors such as actual sampling errors.
The foregoing description is only of the preferred embodiments of the invention, and all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (3)
1. The electromagnetic switch closing control method for intelligently identifying the load is characterized by comprising the following steps of:
s1, analyzing the relation between a contact closing phase angle, a load power factor angle and a surge current;
step S2, based on the relation between the contact closing phase angle and the load power factor angle and the surge current, obtaining the optimal closing phase angle for inhibiting the surge current under different loads of the electromagnetic switch;
s3, performing switching-on experimental simulation on loads with different power factor angles by using a circuit simulation model of an electromagnetic switch contact loop, obtaining first current half-wave time of inductive loads and capacitive loads under different power factor angles, and arranging data into a line graph;
s4, identifying the load type and the power factor angle of the electromagnetic switch based on the line diagram 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, so as to realize no-inrush current closing under different loads;
the step S1 specifically comprises the following steps:
when the control object of the electromagnetic switch is a capacitive load, the contact is equivalent to an ideal switch, the capacitive load is equivalent to a resistor R and a capacitor C, the contact loop simplifies an ideal circuit for controlling the capacitive load for the ideal switch under the AC power supply, and a circuit differential equation in a corresponding closing process is as follows, wherein u c Is capacitance voltage, um is power voltage amplitude, alpha is switch closing initial phase angle
The differential equation is reduced to obtain the circuit current of the closing process as follows, wherein,the load power factor angle of the circuit;
analysis formula (2) shows that the transient component gradually approaches zero over time; by controlling the initial phase angle alpha of the closing, the transient component is always zero, so that the purpose of eliminating the surge current is achieved, namely, the conditions of eliminating the surge current by the capacitive load are as follows:
similar to the derivation of the resistive load, the equivalent approximation analysis is performed on the contact loop of the resistive load, and the differential equation is as follows:
the differential equation of the resistive-inductive load is simplified, and the circuit current in the closing process is as follows:
similarly, in order to achieve the purpose of eliminating the inrush current, the transient process should be controlled to be zero, and the conditions for eliminating the inrush current by the inductive load are as follows:
the step S2 specifically comprises the following steps:
by utilizing a circuit simulation model of an electromagnetic switch contact loop, carrying out switching-on experimental simulation on loads with different power factor angles, and recording the first half-wave time t of the contact current after switching-on bb ＝t b -t a ；t a To start the closing time of the current, t b The first zero crossing point moment of the closed current;
at an initial closing phase angle alpha 0 When the power factor is equal to 45 DEG, recording first current half-wave time of inductive load and capacitive load under different power factor angles, arranging data into a line graph, and analyzing to obtain first current half-wave time corresponding to different loads; reading the power factor angle of the load through the line graphAnd then the corresponding optimal closing phase angle is adjusted.
2. The electromagnetic switch closing control method of intelligent load identification according to claim 1, wherein the deviation of the load power factor angle identified in the step S2 is needed to further judge the suppression condition of the inrush current, when the resistive load and the inductive load are adjusted to the optimal closing phase angle, the transient component of the current should be zero, the current formula in the closing process is simplified, and the current expression in the no inrush current is obtained as follows
And based on the above analysis, the current half-wave time of the capacitive load and the inductive load is obtained when the optimal closing phase angle for eliminating the inrush current is adjusted.
3. The electromagnetic switch closing control method of the intelligent load identification according to claim 1, wherein the step S4 is specifically: when the power supply of the coil control loop is normal, the coil control loop is recorded as t0 to send out a power-on preparation signal, then the voltage zero point of the contact loop is detected, and when t 1 After detecting the contact voltage zero point at any time, entering an action delay program to delay time t d ＝t 2 -t 1 。
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