**Abstract:** This paper presents the application of the ABB ACS-510 frequency converter in a thermal network and introduces a Modbus-based control method for managing the inverter. The system is designed to improve energy efficiency, reduce operational costs, and enhance the overall performance of the heating station. By implementing variable frequency drives (VFDs) for circulation and makeup pumps, the system achieves precise control over water flow and pressure, contributing to better temperature regulation and energy conservation.
**Keywords:** Inverter, load control, Modbus, thermal network, energy saving
**1. Introduction**
Heating networks play a crucial role in urban infrastructure by providing efficient and environmentally friendly heating solutions. As a key component of these systems, the thermal station directly influences user comfort and energy consumption. Ensuring energy efficiency and safe operation at the thermal station is essential for both economic and environmental reasons. This paper explores how the integration of ABB ACS-510 frequency converters can significantly enhance the performance of thermal stations.
**2. Project Overview**
The Harbin Airport Development Zone includes 120 central heating stations, covering an area of approximately 5.7 million square meters. The total heat load is around 10,000 J/H, with a design water temperature range of 130°C to 70°C. The system uses hot water heating, with the primary and secondary networks connected through heat exchangers. Two circulating pumps and one makeup pump are controlled using ABB ACS-510 frequency converters, which help automate and optimize the system’s operation, leading to significant energy savings.
**3. System Composition**
A typical thermal station consists of several key components: a heat exchanger, a control panel, circulation and makeup pumps, and communication lines. The control system is primarily based on a Schneider PLC, which collects and processes data from various sensors. This data is then transmitted to the dispatch center via ADSL. Based on the indoor temperature and outdoor conditions, the system adjusts the secondary water supply temperature and flow rate to maintain optimal heating levels.
**4. Functionality of the Thermal Station**
After heat exchange in the primary network, hot water is distributed through the secondary network to end users. The station’s operation is optimized to meet city heating standards while minimizing energy consumption. Two methods are used: quality control, which adjusts the flow of primary water to regulate secondary temperature, and quantity control, which varies the pump speed to manage flow. Combining these approaches results in a more efficient and cost-effective heating system. The use of VFDs reduces energy consumption by up to 30%, while balancing the system further improves efficiency by 20–30%.
**5. Circulating Pump Control**
The ABB ACS-510 is well-suited for square load applications due to its low cost and built-in Modbus communication capabilities. It allows for remote control of the inverter, including starting, stopping, and adjusting the motor speed. The inverter's operational parameters are sent to the PLC via Modbus, which then transmits the data to the dispatch center. This setup simplifies installation, reduces wiring, and improves system reliability. Two 37 kW circulation pumps are used, with one as a backup. The inverter is configured to operate in a delay mode for smooth transitions between pumps.
**6. Makeup Pump Control**
The makeup pump also uses an ABB ACS-510 frequency converter, though it is set to address "3" on the Modbus bus. Unlike the circulation pump, the makeup pump is the last device on the bus and is controlled by the PLC through register "4003" to maintain constant pressure in the secondary network. This ensures stable water pressure and prevents system imbalances.
**7. Conclusion**
The integration of ABB ACS-510 frequency converters in the thermal station has proven to be highly effective in reducing energy consumption and improving system performance. The use of Modbus communication not only enhances control accuracy but also reduces the need for additional hardware, lowering both initial investment and maintenance costs. The successful implementation of this system demonstrates the potential of VFDs in modern heating networks and highlights their value for future projects.
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