Interpretation of the application of VFD (Variable-frequency Drive) in the heat exchange station of the heating system

Using frequency conversion technology and automatic control technology to transform the heating and heat exchange system of some heat exchange stations, and integrate the technology into the newly installed heat exchange stations to achieve the purpose of saving energy, reducing consumption, improving system performance, and adjusting heat load.

1. Due to the shortage of energy and the continuous progress of science and technology, the scientific management of energy consumption in enterprises is an obvious sign to measure whether the management of enterprises is scientific, especially for large energy-consuming households such as our heating industry, scientific management of energy consumption, energy saving, It is a problem that must be solved at present. The power company is a heating service unit in Qinhuangdao Economic and Technological Development Zone. The heating area is increasing year by year. The number of heat exchange stations has grown from a dozen in the past to 40 to 50 now, and the number is still increasing. It turns out that the heating equipment of more than a dozen heat exchange stations adopts the traditional power frequency start-up and operation (operating at one speed). This system not only has a large impact on the power grid and affects the life of mechanical equipment, but also cannot adjust the circulating water volume and consumes less energy. big. How can the heating equipment of the new heat exchange station save energy? worth considering. In view of this situation, the company's leadership team made a research decision to pay close attention to energy consumption management, invest funds in technical transformation of old equipment, and integrate frequency conversion technology and automatic control technology into the new heat exchange station. After use, the energy saving effect is significantly improved.

2. The composition and working principle of the heating system of the heat exchange station Usually the heat exchange station has one or several sets of heating and heat exchange units. Each unit is composed of heat exchanger, circulating water pump, decontamination device, various valves, primary and secondary pipe networks and some thermal instruments.

The heat exchange unit sends the return water of the secondary pipe network to the heat exchanger and the circulating water of the primary pipe network through the circulating pump for heat exchange, and then sends it to the user for heating. The heating return water is sent to the heat exchanger through the circulating pump for heat exchange. And so on. If the circulating water leaks during the circulation process, the water replenishment system will automatically start, automatically track the change of the pressure of the secondary return pipe, and finally maintain the balance of the system.

It can be seen that the working process of the heating and heat exchange system is a continuous energy transfer process of heat exchange. Here, the circulating water system is the main transmission medium of energy.

3. The principle of frequency conversion energy-saving transformation of the original heat exchange station heating and heat exchange electrical equipment The original system is to provide power for circulating water through the motor to drive the quantitative circulation pump. The motor is directly connected to the mains and has been running at power frequency, so the output flow of the circulating pump cannot change with the change of the heating load, but always maintains a constant flow. When it is necessary to adjust the heating load to adjust the flow, it is usually adjusted manually by opening a large valve or closing a small valve. Since the temperature is a lagging parameter, the adjustment cycle is long and difficult to adjust. Moreover, additional losses are generated on the valve, which wastes a lot of energy.

The frequency conversion transformation of the circulating water system is based on the above reasons. The modified system can adjust the output flow of the circulating pump by controlling the speed of the circulating pump motor in a timely and appropriate manner through the VFD (Variable-frequency Drive) according to the outdoor temperature sensor and the PLC controller to meet the heating load requirements. This minimizes the energy consumption of the motor throughout the load and change process. Furthermore, the application of VFD (Variable-frequency Drive) can also improve the power factor of the system, reduce the reactive power loss of the motor, and improve the power supply efficiency and power supply quality. To sum up, it is not difficult to see that the frequency conversion energy-saving transformation of the original heating and heat exchange system can bring huge energy-saving effects.

4. Frequency conversion energy-saving transformation plan for heating and heat exchange electrical equipment of the original heat exchange station When the frequency conversion transformation of the original system is carried out, in order to ensure safety and reliability, the electric control equipment of the original system should not be changed as much as possible. In addition, the operating circuit of the circulating pump motor is retained, and the control circuit is added to ensure that users can easily switch between power frequency and variable frequency operation.

VFD (Variable-frequency Drive) adopts ABBACS-400 series. This kind of VFD (Variable-frequency Drive) has its unique features of energy saving and consumption reduction, frequency conversion speed regulation, programmable multi-operation modes, and perfect protection functions.