1. Application of EVE SMART PLC in the Heating Industry
1.1 Background of the Heating Industry
To improve national environmental protection and urban infrastructure, upgrading the old-style heating system is imperative. Currently, centralized heating systems consist of three parts: heat source, heating network, and heat users. Specifically, heat is supplied by a unified thermal power plant or heating company, and the heat medium (steam or hot water) is transported via heat pipes to heat exchange stations in one or more residential areas for heat exchange. The heat is then delivered to users through internal heating pipes within the residential area. Because there are numerous heat exchange stations in the heating network, and each station operates independently, overall control is impossible. In cases of insufficient heat source, "heat competition" can occur. It is difficult to ensure heating quality, leading to a mismatch between supply and demand. Faults cannot be promptly reported, affecting reliable operation; data is incomplete, and quantitative management is not possible.
In order to change this backward situation, improve heat exchange performance and energy-saving performance, it is essential to upgrade the old equipment to full automation.
1.2 Heating Equipment Technology
(1) Process flow
The heating process is as follows: The heat medium in the primary network flows out from the power plant, passes through a heat exchanger, and then returns to the power plant via the secondary network loop. Driven by a circulating pump, the medium (usually water) heated by the heat exchanger in the secondary network flows to the users, and then flows back to the heat exchange station through the return pipe after being installed in the radiators. Because the water volume in the secondary network continuously decreases due to users releasing air or pipe leaks, a makeup water pump draws water from the tank to constantly replenish the secondary network. The entire process is shown in Figure 1.
Figure 1. Schematic diagram of heating process
Figure 2 Heating unit interface
Figure 3 Main monitoring interface for heat exchanger heating
(2) Key Control Points
①Determine the secondary water supply temperature based on changes in outdoor temperature and heat load curve.
②The system compensates for the heating temperature by setting the secondary return water temperature.
③ PID-controlled circulating pump maintains a constant secondary supply and return water pressure difference to ensure the heating needs of end users.
④ Time-based control can be set as needed. Users can manually adjust the frequency to control the rotation speed.
⑤ The water supply pump is controlled to supply water in real time according to the pipeline pressure.
⑥ Conduct thermal analysis on pipeline flow rate, supply and return water temperature, and information from the heating company.
1.3 System Configuration (as shown in Figures 2 and 3)
1.4 System Architecture and Configuration Scheme
The hardware configuration of the heating system using Yiwei SMART PLC is shown in Figure 4, and the system architecture is shown in Figure 5.
Figure 4 System Hardware Configuration
Figure 5 System Architecture Diagram
1.5 Product Advantages
①STEP 7 - MicroWIN Smart programming, engineers do not need to learn anything else.
② The complete Yiwei PLC + HMI + IoT solution is stable, secure and reliable.
③ The PID control is stable.
④ The increasingly rich configuration screens of HMI provide convenience for customer development.
⑤ EVE SMART PLC offers high precision, high performance, and high cost-effectiveness.
By applying advanced and mature automation technologies to the traditional urban centralized heating sector, Yiwei has built advanced urban heating systems. This can enhance heating users' energy-saving awareness, improve heating quality, achieve efficient management of the heating system, ensure heating safety, and bring significant economic and environmental benefits to enterprises.
2. Application of SMART PLC in the Water Supply Industry
2.1 Background of the Water Supply Industry
Traditional water supply systems occupy large areas, are prone to pollution, and have unstable pressure. Constant pressure water supply can maintain a constant water pressure, thus balancing water supply and demand. This means that when water demand is high, the water supply is high, and when water demand is low, the water supply is low, thereby improving the quality of the water supply.
2.2 Water Supply Process Flow
As shown in Figure 6, the actual pressure of the pipeline network is fed back to the PLC via a pressure sensor. The PLC compares this pressure with the actual given pressure, performs PID calculations, and outputs the result as the operating frequency for control. Changes in the operating frequency alter the speed of the water pump motor, thereby adjusting the water supply. The operating frequency and speed of the variable frequency water pump vary depending on water consumption. An upper and lower frequency limit is set in the inverter settings. When water consumption is high and the supply pressure is lower than the set value, the inverter frequency rises to the upper limit; when water consumption is low and the supply pressure rises, the inverter output frequency drops to the lower limit. By comparing pressure and frequency, the AC contactor group is switched to coordinate the number of operating water pump motors and to complete the pump start/stop and the switching between variable frequency and mains frequency. By adjusting the number of operating motors and controlling the variable frequency speed of one motor in the motor group, the operating pressure of the pipeline network is kept stable, thus achieving constant pressure water supply.
Figure 6 Schematic diagram of water supply process
2.3 System Architecture and Configuration Scheme
The location diagram, hardware configuration, and system configuration of the water supply system using EVE SMART PLC are shown in Figures 7, 8, and 9.
Figure 7 Point Map
Figure 8 System Hardware Configuration
Figure 9 System Configuration
2.4 Product Advantages
The UN SMART PLC from Yiwei offers CPU modules of different types and I/O point counts, with a maximum of 60 I/O points per unit. It boasts a powerful instruction set and rich communication and motion control functions, meeting the needs of most small and medium-sized process control and automation equipment.
• Communication: The SMA RTCPU comes standard with an Ethernet port, supporting the MODBUS-TCP protocol for program monitoring and PUT-GET communication; and an RS485 communication port, supporting the freeport protocol and MODBUS-RTU protocol.
• Expansion capabilities: Includes expansion cards and modules, supporting up to 6 expansion modules;
• High-speed input: All models are equipped with single-phase 6-channel 200KHz and AB-phase 4-channel 100KHz high-speed counters;
• High-speed output: The transistor-type CPU provides up to three-axis 100KHz high-speed pulse output, supporting motion control functions and PWM adjustment.
Figure 10
The SMART series offers a wide range of models, with CPUs providing 20, 30, 40, and 60-point relay and transistor models. Modules include digital expansion modules, analog expansion modules, and temperature modules. In the future, we will also launch Yiwei's traditional XP series CPUs, as well as bus modules and IoT modules. Furthermore, SMART PLCs are highly compatible with Siemens Smart, fully compatible with Siemens hardware and software. The program requires no modification; it is ready to use immediately after download. Precise PID control ensures product stability while reducing costs, as shown in Figure 10.
