Application Of Omron Plc In Control System Of River Dam Gate

1 Preface

China's water resources are extremely uneven in geographical distribution. Generally speaking, there are more western regions and less eastern regions, and hydraulic resources are relatively concentrated in the southwest region, while the eastern region with economic development and large energy demand is extremely small. Therefore, in addition to the needs of the western power market, the development of western water resources is more important to consider the eastern market and implement the “Western Power East” strategy of hydropower. Omron But in the development of water resources, especially inland rivers In the dam control system, problems such as backward equipment, poor function and severe aging are still common. The corresponding system has large energy consumption, low efficiency, and faces technical transformation and maintenance problems. Many of the river dam gate control system equipment is backward and the automation level is low. Even a large proportion of manual operations, low efficiency, and the need for system upgrades to meet higher and more secure control requirements PLC

As a general-purpose industrial control computer, programmable controllers have been used from scratch in the past 40 years, their functions range from weak to strong, and their applications range from small to large PLCs. Today's programmable controllers are becoming mainstream control devices in industrial control. In order to play an increasingly important role in the world, this paper proposes an overall design scheme gate based on PLC and fieldbus control based on the specific situation of large-scale barrage gate control

The barrage consists of a 17-hole open-close gate with a span of approximately 300 m and a maximum opening of the gate of 1.7 m. The gate control room is 40m away from the dam's water surface. Due to the large geographical span, the gate control system is designed by bus distributed hierarchical control.

2 System Composition

The system adopts the distributed control mode of the bus and is divided into two levels: field control and centralized control. The bus uses OMRON's CompoBus/S fieldbus protocol, as shown in Figure 1.

Figure 1 System overview

The field level consists of a gate control cabinet (CPU adopts OMRON's CP1H series PLC) installed at each gate site, a total of 17 units. Its function is to realize manual control of the gate at the site, on-site collection and monitoring of water level, gate opening, gate operation status and error information, and complete real-time communication with the centralized control level, including: receiving control information, completing gate control Action, send the gate running status and error information for remote monitoring to the master station.

The centralized control level is controlled by a control cabinet (CPU using OMRON's CJ1G series PLC) installed in the gate control room. Its main function is to communicate with the subordinate system through CompoBus/S, process related data, send the running status and error information of the gate to the monitoring host, and receive the instruction of the monitoring host and then forward it downward.

The monitoring host receives and displays information such as gate opening degree and status through monitoring software (this system uses Kingview), alarms the error information, and can issue commands to control the operation of the gate and generate reports. The UPS power supply is used to power the two-stage control system during a power outage to ensure uninterrupted operation of the system.

3 System Configuration and Hardware Wiring

The number of input and output points of the single gate control cabinet at the field level is: DI=16, DO=6, AI=2 (first hole). The system's field control level CPU uses OMRON's CP1H series PLC with 40 input and output points. Since the No. 1 control cabinet will collect the water level, it adopts CP1H— XA40D with its own analog input and output module. This type of PLC has 4 points of analog input and 2 points of analog output. Its function has already been used for water level acquisition. Enough. The remaining control cabinets use CP1H— X40D without the in/out module. The communication is completed by the CP1H extended communication unit SRT21, and the communication slave node number is O. According to the PLC address assignment rule, the input address is ClO2 and the output address is ClO102.

The control cabinet CPU of the centralized control level uses CJ1G series PLC to expand two SRM21 master units, and their unit numbers are 0 and 2. According to the address allocation rule of CJ1G, the addresses are CfO2O00 and CfO202O, respectively. The two master units exchange data with the lower 8 and 9 slave units and communicate with the monitoring host. The monitoring host is connected to the CJ1G via an RS232 cable. Communication between the two-level systems is done using the OMRON fieldbus protocol CompoBus/S.

CompoBus/S communication mode can be divided into long-distance communication and high-speed communication. When the working mode is the long-distance communication mode, the transmission rate is 83.75Kbps and the transmission distance can reach 500m. When it is in the high-speed communication mode, the transmission rate is 750Kbps and the transmission distance is 100m. The communication mode is set by the DIP switch of the I/O connection unit. This system selects the long distance communication mode.

Since the implementation of the centralized control level is relatively simple, here is only the wiring diagram and software implementation of the PLC (first hole) of the field level control cabinet. The wiring schematic diagram of the field level control cabinet is shown in Figure 2.

The PLC provides 220VC power from the UPS power supply. The 0CH and 1CH of the PLC are input channels, and the 100CH and 101CH are output channels. The lower 8 bits of the 0CH channel, I: 0.00~I: 0.07, are connected to the rotary encoder to collect the gate opening state. The 0CH channel is high 4 bits for on-site gate control operation and other state collection of the system. In the 1CH (input) channel I: 1.08 for on-site/central control selection. I: 1.09 is to clear the error alarm bit. When the error is discharged, the input of I:1.09 causes the error message to be reset and the system can run. The latter two of the 1CH provide a protection for the operation of the gate.

The output of the output channel 100CH is the gate control signal and prompt and alarm information. IN1+ and IN1 in the figure are analog input channels. It is connected to the water level gauge. Since the CP1H series PLC provides a 24VDC power output, it can be used directly as a power source for the water level meter.

Figure 2     PLC Field Wiring Schematic

4 Software Design

The software of the No. 1 control cabinet is written as follows: The automatic control function of the system can be divided into field level control and centralized open/closed loop control. The program flow chart of its control is shown in Figure 3. The field control level has the highest priority because of the high safety and reliability required for gate control. When on-site control is selected, the centralized open/closed control is shielded. The PLC collects the rise, fall, and stop control input states of the field control cabinet, and performs the lifting and lowering operation of the gate. At this time, the opening information and operation status of the gate can be displayed and outputted on the text display on the local control cabinet, and simultaneously uploaded to the monitoring host for display. If an error occurs, an alarm is issued and the gate is stopped.

Figure 3  System Software Control Flow Chart

When W2.05 is reset, centralized open loop control is performed. The remote open loop control can click the up, down, and stop buttons on the control panel (the system uses the King of Configuration) to complete the remote control of the gate. When the up, down, and stop buttons are clicked, the host will set the storage bit of the centralized control level PLC, and transfer the set information to the distributed control level PLC through the CompoBus/S bus. The memory address is W2.00, W2. 01, W2.02. The CP1H performs gate operation based on the state of these three switching quantities. Considering that fast switching of up, down, and stop can cause errors, all interlocks must be used. When an error occurs, the gate must be stopped immediately regardless of the state of operation of the gate, and an alarm is issued until the error is discharged, and the fault alarm is cleared by the CP1H fault reset button (CIO1.09) and re-run.

The acquisition of the gate is obtained by an 8-bit incremental rotary encoder input. Its input channel is CIO0.00~CIO0.07. Since the encoder inputs the Gray code, it needs to be converted to BIN (in hexadecimal) data (storage and D20) using the Gray code conversion instruction (GRY). Since the encoder has only 8 bits, it is necessary to perform software acquisition calculation on the number of turns (D70) that the encoder has rotated. Finally, the running distance of the gate (D250) is calculated according to the number of turns D70 of the encoder and the value D20 of the encoder at this time. Its calculation formula is: D250=D70* single turn height + D20. Its flow chart is shown in Figure 4.

Figure 4  Gate opening collection subroutine

The water level sensor used in the system water level collection is a pressure type water level transmitter, and the output signal is a 4-20 mA current signal. Since the PLC has its own analog signal input channel, the standard current signal can be directly input into the PLC (the system adopts CIO200 and CIO201 respectively as the water level input channel before and after the gate), and it is not necessary to expand the A/D module. The analog signal automatically performs A/D conversion in the PLC analog input channel. The A/D conversion here uses linear transformation with a resolution of 1/6000 or 1/12000. The resolution is selected by the PLC. The error information during the operation of the gate mainly includes: the gate is stuck, the gate is stalled, and the upper limit of the rise caused by the excessive opening of the gate and the lower trap caused by the excessive drop. The collection of these error messages is relatively simple and will not be described in detail here.

5 Summary

Since the system was put into operation, significant benefits have been achieved, which are reflected in the following aspects:

(1) Improve the efficiency of equipment use. Through comprehensive automation of gate control, this scheme eliminates the previous manual observation and experience to realize the optimal operation of the river dam gate, reduces the damage rate of the main equipment, prolongs its service life and maintenance cycle, and saves spare parts consumption every year. At the same time, this program adopts real-time load control to improve the utilization rate of equipment, reduce the idling rate of equipment, and achieve energy saving of 3%~5%.

(2) Enhanced reliability and security. The design scheme realizes the interlock control, abnormal alarm and timely shutdown of the main equipment. The engineer station establishes an authorization to modify the relevant parameters, and the main control station operates in an authorized manner, which avoids equipment damage caused by human error, and enhances the safety and reliability of the system operation.

(3) Reduce the labor intensity of the employees. This design scheme realizes the remote monitoring of the centralized control room and can perform corresponding operations accordingly. The site only needs to patrol irregularly, which reduces the required quantity and labor intensity of the employees. Automatic control of the purpose of reducing staff and increasing efficiency