The Xindashida AS800 High-Voltage Variable Frequency Drive in Applications for Fan and Pump Systems in the Power Industry
2025-06-03
The Xindashida AS800 High-Voltage Variable Frequency Drive in Applications for Fan and Pump Systems in the Power Industry
Project Background
The Shanghai Laogang Renewable Energy Utilization Center incinerates 3,000 tons of municipal solid waste per day. Equipped with advanced flue gas treatment systems and power-generation equipment, it is one of the largest municipal solid-waste treatment facilities in Asia—and also among those with the highest environmental standards. Construction of the project began in August 2010 and was completed and put into trial operation in May 2013. After commissioning, the facility will be able to process 1 million tons of municipal solid waste annually while generating approximately 250 million kilowatt-hours of electricity each year, with about 200 million kilowatt-hours fed into the grid annually. The slag remaining after waste incineration will be comprehensively reused—for purposes such as landfill cover material, brick production, and road base construction.
This article takes this project as an example to introduce the application characteristics of the AS800 high-voltage variable frequency drive in fan and pump applications within the power industry, and provides detailed explanations of the on-site process, the technical features of the VFD, and its practical application results.
Customer needs
Process Pain Points of Circulating Water Pumps
In a circulating water pump system, the circulating water pump enables the recycling of water resources. Hot water exiting the condenser is sent to the cooling tower, where it releases its heat to the atmosphere and cools down. Afterward, the cooled water is pressurized by the circulating water pump and returned to the condenser to cool the exhaust steam from the low-pressure cylinder. Since the system water level remains essentially stable, the head developed by the circulating water pump also stays relatively constant. In other words, the amount of water pumped determines the power consumption of the circulating water pump.
Due to fluctuations in unit load and external environmental conditions, vacuum levels are constantly changing. Therefore, it is necessary to promptly adjust the circulating water flow rate to ensure the safe and economical operation of the unit. During normal winter operation, running one circulating water pump at low speed is sufficient to meet the unit’s cooling requirements. However, during seasons with large temperature variations and under conditions of significant load changes, even with the pump’s dual-speed adjustment capability—high and low speeds—cannot guarantee that the unit operates in an economically optimal manner, leading to high plant power consumption and elevated generation costs. Consequently, it is essential to implement variable-frequency control for the pumps.
Pain Points in Boiler Processes of Waste-to-Energy Plants
The boiler system of a waste-to-energy plant includes a primary air fan system and an induced draft fan system. During actual operation, the primary air fan system primarily extracts combustible gases from the waste storage pit and directs them into the waste incinerator. The combustion process generates heat that is supplied to the boiler, producing steam which drives a steam turbine to generate electricity. At the same time, this system prevents gas leakage (as the gas contains toxic substances). In practical applications, these systems are critical equipment, and their operational reliability must be ensured. The induced draft fan system creates negative pressure in the furnace during power generation, drawing away exhaust gases. This system also has a significant impact on the overall power generation process; a shutdown of the induced draft fan could lead to boiler flameout.
Waste-to-Energy Plant Boiler Process Flow
Xinshida Solution
Proposal Description
Based on the operational requirements of the on-site load and considering that the failure of the frequency converter should not affect production and ensure the system continues to operate normally, the system must be equipped with a power-frequency bypass. When the frequency converter malfunctions, the motor can be switched over to run at power frequency. The one-to-one automatic bypass solution is suitable for applications where ease of operation is desired or where, in the event of a fault during variable-frequency operation, the system can automatically switch back to power-frequency operation.
To ensure that production is not affected after the frequency converter is taken offline and to maintain normal system operation, the system must be equipped with a power-frequency bypass. When the frequency converter fails, the motor can be switched over to operate at power-frequency. The three contactors shown in Figure 2 are installed in the bypass cabinet. To prevent reverse power flow back to the output terminals of the frequency converter, KM2 and KM3 are naturally mechanically interlocked. When KM1 and KM2 are closed and KM3 is open, the motor operates in variable-frequency mode; when KM1 and KM2 are open and KM3 is closed, the motor runs at power-frequency.
Primary circuit of the variable frequency system
Scheme advantages
● Ideal drive for mechanical systems: The high-frequency harmonic components contained in the output current of the AS800 high-voltage variable frequency drive are extremely small, so the resulting pulsating torque has negligible influence on the shaft system, thereby reducing motor vibration.
● Multiple curve selection options: Since internal mixers are multi-stage transmission mechanisms, different machines exhibit varying characteristics. Therefore, multiple curve algorithms are provided to meet the diverse process requirements of different machinery.
● Meet the load requirements of on-site pumps and the need for rapid dynamic response during braking operations.
● Adjust the water flow by regulating the motor speed with a frequency converter, ensuring that the motor’s output power is essentially proportional to the water demand. This keeps the motor operating at high efficiency at all times, achieving significant energy savings.
● The system is equipped with an automatically controlled bypass cabinet, which can provide sufficient contacts for the furnace front operator’s console.
● The system features two control loops—one for variable frequency and one for line frequency—and includes a single-module bypass function, enhancing the redundancy of the inverter.
● Ensures that the motor’s current rises smoothly during startup and loading, with absolutely no impact; enables soft stopping of the motor, thereby avoiding damage caused by inrush currents and helping to extend the service life of the equipment.
● By using a phase-shifting rectifier transformer, harmonic currents on the grid side are significantly suppressed. Voltage superposition is achieved through cascading multi-level H-bridge power modules, resulting in an almost perfect high-voltage sinusoidal output that can directly drive high-voltage motors without the need for any additional filters.
● The motor operates at a high efficiency level with a high power factor, reducing reactive power losses and saving substantial amounts of electrical energy.
Measured output current waveform diagram from the field
On-site AS800 High-Voltage Variable Frequency Drive
Scheme Composition
We are using 13 units of the Xindada AS800 series high-voltage variable frequency drives, including 4 units for primary air fans, 6 units for feedwater pumps, and 3 units for circulating water pumps.
Associated products
AS800 High-Voltage Frequency Converter
Project Results
● Improved energy efficiency
Compared with traditionally controlled fans and pumps, energy savings are the most practical and meaningful advantage of using frequency converters to control these devices. Adjusting the rotational speed of fans and pumps according to the actual demand for raw materials on-site represents an economically efficient operating condition.
Based on the analysis of the on-site operational conditions, the energy savings achieved by installing variable-frequency drives at the site—compared to the energy consumption without such drives—exceed 20%, bringing significant economic benefits to users.
● Reduced operating costs
The operating costs of conventional fan and pump systems consist of three components: procurement costs, maintenance costs, and energy costs. Among these, energy costs account for approximately 60% of the total operating costs of fans and pumps. By reducing energy costs—and further minimizing the impact on equipment due to variable-frequency starting—the volume of maintenance and repairs will also decrease accordingly, leading to a substantial reduction in overall operating costs.
● The service life of fans and pumps is extended.
The frequency converter starts the fan and pump from 0 Hz, and its acceleration time can be adjusted to reduce the impact on the electrical and mechanical components of the fan and pump during startup, thereby enhancing system reliability and extending the service life of the pump. Moreover, variable-frequency control helps minimize current fluctuations during unit startup—a phenomenon that can affect power grid performance and the operation of other equipment. The frequency converter effectively reduces the peak value of the starting current to the lowest possible level.
● Lower operating noise
According to the operational requirements of fans and pumps, after the variable-frequency speed control retrofit, the motor’s operating speed has significantly slowed down, thereby effectively reducing the noise generated during the operation of the fans and pumps.
