Intelligent processing method for dynamic harmonics of inductive load

Abstract

The application provides a kind of inductive load dynamic harmonic intelligent processing method, computer according to production process, before load needs to start, according to the compensation value of pre-compensation, control signal is sent to PLC, PLC sends analog signal to silicon controlled trigger SCR-Y3 according to control signal through analog module EM235CN, opens a group of bidirectional silicon controlled rectifier conduction angle;PMC53 multifunctional instrument transmits acquisition data to computer, and computer is compensated according to the power factor if the value read after exceeds 0.92 more than the compensation value of pre-compensation, equipment starts after a minute;After the equipment starts, the power factor is reduced to 0.92 below, and the compensator switches a group of capacitors again, so that the current power factor is greater than or equal to 0.92;If the power factor is greater than or equal to 0.92 after the equipment starts, the compensation cabinet does not switch other group capacitors again.The application makes up the defect of excessive compensation current in later compensation, weakens the impact on power grid, protects the silicon controlled rectifier from being damaged, and can reduce the loss and improve the equipment utilization.

Description

Technical Field

[0001] This invention relates to a high-load equipment startup processing technology, and more particularly to a method for intelligent processing of dynamic harmonics in inductive loads. Background Technology

[0002] Current methods for handling dynamic harmonics from inductive loads often employ compensation to improve the power factor of the power grid. This involves using contact-type or contactless reactive power compensation controllers. If the target value is not reached after a single-loop compensation, the next loop is activated. However, both contactless and contact-type compensation methods are susceptible to rapid power factor changes due to sudden load shifts. This can lead to excessive compensation current due to full-contact or full-angle conduction, impacting capacitors or triacs, potentially causing damage to the triac or capacitors.

[0003] To improve the power factor of the power grid, reduce losses in power transformers and transmission lines, increase power supply efficiency, and improve the power supply environment, it is necessary to rationally select compensators to minimize network losses and improve power grid quality. Therefore, it is imperative to develop and design a dynamic harmonic intelligent processing method for inductive loads. Summary of the Invention

[0004] This invention aims to solve the problem of excessive compensation current damaging bidirectional thyristors in current harmonic compensation methods, and thus provides a dynamic harmonic intelligent processing method for inductive loads. To achieve the above-mentioned objectives, this invention provides a method for intelligent processing of dynamic harmonics in inductive loads. The circuit connection is as follows: a current transformer is connected to a PMC53 multifunction meter; a computer is connected to the P1 interface of a PLC and interfaces 9 and 10 of the PMC53 multifunction meter; the current transformer is used to collect the line current value and transmit it to the PMC53 multifunction meter; the PMC53 multifunction meter transmits the collected data to the computer; the computer sends a control signal to the PLC based on the read data signal; the PLC is equipped with an extended analog module EM235CN, which is connected to a SCR-Y3 triac; the PLC receives and sends the control signal, converts it into an analog signal through the EM235CN, and then sends it to the SCR-Y3; the SCR-Y3 is connected to bidirectional triacs K1, G1, K2, and G2 to control the conduction angle of the triacs; the bidirectional triacs are connected to capacitors for compensating the electrical circuit. The specific method for intelligent dynamic harmonic handling of inductive loads is as follows: (1) Input the production process flow and the power factor of the load to be started into the computer. The PMC53 multi-function instrument calculates the current power factor and then transmits it to the computer. (2) The computer reads the current circuit power factor value of the PMC53 multifunction meter and calculates the power factor after starting the load; if the power factor after starting the load is lower than 0.92, pre-compensation needs to be started; the compensation value of pre-compensation = 0.92 - power factor after starting the load; (3) According to the production process, the computer sends a control signal to the PLC based on the pre-compensation value before the load needs to be started. The PLC sends an analog signal to the SCR-Y3 thyristor trigger through the analog module EM235CN based on the control signal, and opens a set of bidirectional thyristor conduction angles. (4) The PMC53 multi-function instrument transmits the collected data to the computer. The computer reads the compensated power factor. If the value exceeds 0.92, which is greater than the pre-compensation value, the equipment will start after one minute. After the equipment starts, if the power factor drops below 0.92, the compensator will switch on another group of capacitors to make the current power factor greater than or equal to 0.92. If the power factor is greater than or equal to 0.92 after the equipment starts, the compensation cabinet will not switch on other groups of capacitors.

[0005] Furthermore, the computer, PLC, and multi-functional instrument PMC53 communicate using the RTU protocol and RS485.

[0006] Further, the power factor after the load is started = 1 - (1 - power factor value of the load to be started) - (1 - power factor value of the current circuit).

[0007] The advantages of this invention are as follows: (1) In response to the increase in the power factor in the existing power grid, we have adjusted the compensation method. We have adopted the method of early compensation, which interferes with the power grid in advance to improve the power factor. This method makes up for the defect of excessive compensation current in the later compensation, reduces the impact on the power grid, and protects the thyristor from damage.

[0008] (2) The control system can be expanded externally. This control system adopts the RTU protocol. Any equipment or detection unit that complies with this protocol can be added to this system. The physical method adopts the 485 communication method. This system can be networked through a computer, and can be remotely controlled, detected, warned, and remotely input into the process flow. It can also be expanded to establish a cloud network system, etc.

[0009] It can automatically adjust and compensate for the power factor based on the status of the equipment to be put into use, and has self-learning capabilities. No additional manual intervention is required, demonstrating the intelligence of this equipment. This system adopts a closed-loop feedback system, and the core detection system is the PMC53 multi-function instrument, which features simple wiring and strong anti-interference capabilities.

[0010] (3) Improve equipment utilization. With the same active power, by improving the power factor, the load current can be reduced, and the power distribution equipment through which the power is transmitted to the load increases its power reserve to meet the needs of load growth. If the system is already overloaded, the output reactive current will be reduced due to the improved power factor, preventing the system from operating under overload and thus maximizing the potential of the existing equipment. Because improving the power factor can reduce the active power loss of usable electrical equipment by 20%-45%, the equipment capacity can be increased without adding equipment.

[0011] (4) Improve power supply quality. Improving power supply quality can increase the power factor, reduce the current in the line, reduce the voltage drop, maintain a reasonable voltage range, and improve power supply quality.

[0012] (5) Reduce power loss in the line. Improving the power factor can reduce power loss in the line. From the active power calculation formula, the current I = P / UCOSφ can be derived. When U and P are constant, the current I is inversely proportional to COSφ, that is, I∞1 / COSφ. This means that under the same active power output from the power source, the lower the power factor, the greater the power loss in the transmission line. Therefore, reducing power loss in the line can improve the efficiency of the transmission line, thereby saving energy and reducing electricity costs. Attached Figure Description

[0013] Figure 1 This is the circuit schematic of the compensator of the present invention; Figure 2 This is a flowchart of the compensation method of the present invention. Detailed Implementation

[0014] To better understand the purpose, structure, and function of this invention, the following detailed description of a method for intelligent processing of dynamic harmonics in inductive loads is provided in conjunction with the accompanying drawings.

[0015] Reference Figure 1 The intelligent method for dynamic harmonic processing of inductive loads is based on Figure 1 The circuit consists of current transformers TA1 and TA2, used to collect line current values. These current transformers are connected to a PMC53 multifunction meter, which transmits the collected data to a computer. The specific circuit connections and signal flow are as follows: (1) The computer connects to the P1 interface of the PLC and the 9 and 10 interfaces of the multi-function instrument PMC53. The PMC53 multi-function instrument transmits the collected data to the computer. The computer sends control signals to the PLC based on the data signals it reads. The computer, PLC, and multi-function instrument PMC53 communicate using the RTU protocol and the communication method is RS485. (2) The PLC is equipped with an extended analog signal module EM235CN. The analog signal module EM235CN is connected to the SCR-Y3 thyristor trigger. The PLC receives and sends control signals, converts them into analog signals through the analog signal module EM235CN, and then sends them to the SCR-Y3 thyristor trigger. (3) The SCR-Y3 triac trigger is connected to bidirectional triacs K1, G1, K2, and G2 to control the conduction angle of the triacs; (4) A bidirectional thyristor is connected to a capacitor to compensate for the electrical circuit.

[0016] Reference Figure 1 and Figure 2 The specific method for intelligent handling of dynamic harmonics in inductive loads is as follows: The production process flow and the power factor of the load to be started are input into the computer, and the PMC53 multifunction instrument calculates the current power factor and then transmits it to the computer.

[0017] The computer reads the current circuit power factor value of the PMC53 multifunction meter and calculates the value of the following formula: Power factor after load startup = 1 - (1 - power factor of the load to be started) - (1 - power factor of the current circuit) If the power factor is below 0.92 after the load is started, pre-compensation needs to be initiated.

[0018] The pre-compensation value = 0.92 - power factor after load start-up.

[0019] According to the production process, the computer sends a control signal to the PLC before the load needs to be started. The PLC then sends an analog signal to the SCR-Y3 thyristor trigger via the analog module EM235CN, which turns on a set of bidirectional thyristors and makes the capacitors connected to them run in parallel in the current circuit, thereby compensating for the electrical circuit.

[0020] The PMC53 multifunction meter transmits the collected data to the computer. Based on the compensated power factor, if the value exceeds 0.92 (which is greater than the pre-compensation value), the computer will start the equipment after one minute. Once the power factor drops below 0.92 after startup, the compensator will switch on another group of capacitors to bring the current power factor back to or above 0.92. If the power factor remains above or above 0.92 after startup, the compensation cabinet will not switch on or off any other groups of capacitors.

[0021] Test case The following uses an air compressor as an example to illustrate the specific application of this invention. The previous method involved starting an air compressor with a power of 400 kW and a power factor of 0.89. After the equipment was operational, the power factor was observed to drop below 0.92. The compensation cabinet then began compensation, sequentially opening the conduction angle of each group of thyristors to allow capacitors to be connected in parallel to the current circuit. Once the compensation factor reached 0.92, the compensation cabinet stopped connecting other groups of capacitors, maintaining the current operation. However, sequentially opening the compensation cabinet could cause excessive current, damaging the thyristors, burning out fast-acting fuses, and in severe cases, damaging the capacitors.

[0022] The processing method of this invention is as follows: When the compressor is put into operation, its power factor of 0.89 is pre-input into the computer. The computer, based on the current power grid usage, load power factor, and other comprehensive data, raises the power factor in advance to be equal to or greater than 0.95. The equipment starts up one minute later. If the power factor drops below 0.92 after the equipment starts up, the compensator switches another group of capacitors to bring the current power factor to be greater than or equal to 0.92. If the power factor is greater than or equal to 0.92 after the equipment starts up, the compensator cabinet will not switch any other groups of capacitors.

[0023] In summary, advance compensation results in less current than delayed compensation. This is because the grid load current is low when the equipment is not running, so the current absorbed by the inductive load in the grid when the capacitor is switched on is also very small. However, once the compressor motor is running, the grid load current rises sharply, and the current when switching the capacitor on and off will be very high. This high current can easily damage the thyristor and fast-acting fuse.

Claims

1. A method for intelligent processing of dynamic harmonics in inductive loads, wherein the circuit connection is as follows: a current transformer is connected to a PMC53 multifunction meter; a computer is connected to the P1 interface of a PLC and the 9 and 10 interfaces of the PMC53 multifunction meter; the current transformer is used to collect the line current value and transmit it to the PMC53 multifunction meter; the PMC53 multifunction meter transmits the collected data to the computer; the computer sends a control signal to the PLC based on the read data signal; the PLC is equipped with an extended analog module EM235CN, which is connected to a SCR-Y3 triac; the PLC receives and sends the control signal, converts it into an analog quantity through the EM235CN, and then sends it to the SCR-Y3; the SCR-Y3 is connected to bidirectional triacs K1, G1, K2, and G2 to control the conduction angle of the triacs; the bidirectional triacs are connected to capacitors for compensating the electrical circuit. Its features are: The specific method for intelligent dynamic harmonic handling of inductive loads is as follows: (1) Input the production process flow and the power factor of the load to be started into the computer. The PMC53 multi-function instrument calculates the current power factor and then transmits it to the computer. (2) The computer reads the current circuit power factor value of the PMC53 multifunction meter and calculates the power factor after starting the load; if the power factor after starting the load is lower than 0.92, pre-compensation needs to be started; the compensation value of pre-compensation = 0.92 - power factor after starting the load; (3) According to the production process, the computer sends a control signal to the PLC based on the pre-compensation value before the load needs to be started. The PLC sends an analog signal to the SCR-Y3 thyristor trigger through the analog module EM235CN based on the control signal, and opens a set of bidirectional thyristor conduction angles. (4) The PMC53 multi-function instrument transmits the collected data to the computer. The computer reads the compensated power factor. If the value exceeds 0.92, which is greater than the pre-compensation value, the equipment will start after one minute. After the equipment starts, if the power factor drops below 0.92, the compensator will switch on another group of capacitors to make the current power factor greater than or equal to 0.

92. If the power factor is greater than or equal to 0.92 after the equipment starts, the compensation cabinet will not switch on other groups of capacitors.

2. The intelligent method for dynamic harmonic processing of inductive loads according to claim 1, characterized in that: The computer, PLC, and multi-function instrument PMC53 communicate using the RTU protocol and RS485.

3. The intelligent method for dynamic harmonic processing of inductive loads according to claim 1, characterized in that: The power factor after starting the load = 1 - (1 - power factor of the load to be started) - (1 - power factor of the current circuit).

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