HARSVERT-VA Series Speed ​​Sensorless Vector Control High Voltage Variable Frequency Speed ​​Control System (End)

Section III HARSVERT-VA Series Features and Applications

In the previous two series of articles, the background knowledge of the HARSVERT-VA series of speed-sensorless vector control high voltage variable frequency speed control products was introduced—the basic principles of digital signal processor (DSP) and vector control. This article will introduce HARSVERT-VA. The technical features and applications of the series.
First, HARSVERT-VA series high voltage variable frequency speed control system structure
HARSVERT-VA series high voltage variable frequency speed control system adopts multi-level technology of power unit series, which is a high-voltage source inverter. The Frequency Converter is mainly composed of phase-shifting transformer, power module and controller. General field applications are also supplemented by bypass cabinets, switch cabinets, etc.
The inverter input side uses multiple phase-shifting transformers to achieve isolation and harmonic cancellation. No need for power factor compensation, harmonic suppression device, multi-pulse rectifier technology makes the frequency converter side harmonics can meet the IEEE519-1992 standard and GB/T14549-93 standards.
The inverter output uses multiple power unit phase-shift PWM waveform outputs in series to obtain multi-level high voltage, achieving lower output voltage harmonics, common-mode voltage and dv/dt. No need for additional output filter device, will not cause damage to the motor insulation, bearings, can directly drive ordinary squirrel cage, wound asynchronous motor and synchronous motor.

Taking a 10kV system as an example, Fig. 1 is a schematic diagram of a system structure of a frequency converter. Among them, the DSP controller, the new integrated computer and the PLC together constitute the control and signal processing system of the frequency converter. The three divisions and coordination of each other, so that the Frequency control system to obtain the best control performance.

II. Overview of HARSVERT-VA Series

Due to the use of high-performance DSP chips and new integrated computers, HARSVERT- is based on the HARSVERT-A series of products that are perfectly harmonic, highly reliable, have a wide range of power/voltage levels, and have flexible control interfaces. VA series of speed sensorless vector control high voltage variable frequency speed control products can realize more powerful and high performance high voltage and large capacity AC drive control. At present, the performance indicators of HARSVERT-VA series speed sensorless vector control products are: speed range 100:1, steady state speed accuracy 0.5%, dynamic torque response time less than 200ms, start torque 150% rated torque, basically reach International advanced level.

At present, HARSVERT-VA series high voltage variable frequency speed control system has the following functions:

Constant voltage ratio control

The most significant feature of this type of control is simple and easy to use, and it has become the motor control method used by most inverter manufacturers in China. For most applications where torque response and control accuracy are not high, such as fan and pump loads, it can meet general application requirements.

Sensorless vector control

Without installing complicated and difficult to maintain speed measuring devices, HARSVERT-VA series inverters only need to detect the output three-phase voltage and two-phase currents, and can perform the flux and torque solution of the asynchronous motor according to the pre-automatically measured motor model. Coupled control to start and run low speed and high torque loads.

Speed ​​closed-loop vector control

In situations where the speed accuracy and torque response requirements are higher, the installation of speed sensors can further improve the control accuracy of the HARSVERT-VA series of speed closed-loop vector control inverters.

Automatic tuning of motor parameters

To achieve vector control, it is necessary to detect the stator and rotor resistance and inductance parameters of the motor. HARSVERT-VA series inverters can automatically perform motor blocking test and no-load test on asynchronous motors to realize automatic tuning of motor parameters.

However, it should be noted that the motor shaft and load must be disengaged before the motor parameters are automatically adjusted. Also, during the measurement, the motor must be rotated several times, so no manual work can be performed on the motor.

High-voltage power-down recovery automatic restart

In some user's applications, the high-voltage power grid that supplies power to the inverter may experience a short-term voltage drop or loss. In order to minimize the impact on normal production, the HARSVERT-VA series can be used when the high voltage power supply recovers within the set time limit. Automatically quickly identify and track the current motor speed and resume normal operation.

If the power loss exceeds the set time limit, the inverter will automatically enter the standby state.

Rotation start

If the motor is dragged and even reversed by the load, the inverter can identify the tracking motor speed and drag the load to the set frequency operation.

Single module bypass function

HARSVERT-VA series inverter adopts the single-module bypass method. The new control algorithm ensures the maximum output capacity while ensuring the balance of the output three-phase line voltage, and does not affect the production operation as much as possible.

The bypass of the same level is easy to implement and the algorithm is simple. The domestic inverter manufacturers generally adopt the same-grade bypass method. Compared with the same-grade bypass, the single-module bypass algorithm is more complex and has certain difficulty in implementation, but it can maximize the output capacity of the inverter.

Taking a 5-stage series inverter as an example, assuming no unit bypass, the maximum line voltage output capability of the system is 100%. The following table shows the comparison of the maximum line voltage output capability in the two bypass modes.

Synchronous motor frequency control and automatic excitation control function

HARSVERT-VA series inverters can be used for synchronous motor speed control, and have a closed-loop output power factor control function, can automatically adjust the excitation current, so that the synchronous motor runs at the user set power factor.

Up to ten power cell series

According to the need, HARSVERT-VA series inverters can realize series 4-10 power units in series, voltage levels cover 3-11kV, and the power level of the drive motor can reach 5000kW.

Real-time display and monitoring of system status variables

Including: input side and output side voltage, current, active power, reactive power, power factor, motor speed, multi-point temperature indication, inverter status, and so on.

In addition to displaying commonly used voltage, current, power temperature and other parameters, the monitoring interface also has a software oscilloscope function that can be used for on-site debugging and monitoring.

With perfect motor and frequency converter protection, try to ensure continuous and reliable operation of the equipment

Industrial touch screen multilingual monitoring interface

Historical records, including fault alarm records, operation event records

Built-in PLC, flexible switching, analog I/O interface expansion, process variable PID adjustment

Supports various industrial fieldbus communication protocols, such as Profibus, Modbus, etc.

Third, the application of HARSVERT-VA series products

Because HARSVERT-VA series products have rich functions and flexible motor control methods, they can adapt to most high- and low-end high-voltage and large-capacity AC speed control applications. Can be widely used in power, metallurgy, petrochemical, municipal water supply and other industries, such as fans, pumps, compressors, and so on. Can also adapt to low speed and high torque load or need to start the heavy load occasions, such as ball mill, conveyor, and so on.

HARSVERT-VA series of automatic excitation function is more suitable for synchronous motor applications.

Complemented by the upcoming power feedback unit, the HARSVERT-VA series can also provide excellent control performance for energy-feedback loads such as mine hoists, winches, and more.

Fourth, compatibility with HARSVERT-A series products

HARSVERT-A series products are upgraded to HARSVERT-VA series. In order to use with the new control system, the newly designed voltage measurement circuit must be used, and the control box of HARSVERT-A series should be replaced with a DSP control box. And in the integrated computer man-machine interface monitoring software, select DSP control interface, and related parameter settings. The PLC program is fully compatible.

V. Conclusion

With more and more sets of HARSVERT-VA series of speed sensorless vector control high voltage variable frequency speed control systems in various operating conditions on-site stable operation, more and more users gradually realized the advanced nature and use of HARSVERT-VA series products. Convenience. This also marks China's independent intellectual property rights of high-performance speed sensorless vector control high-voltage large-capacity variable frequency speed control system - HARSVERT-VA series products truly side by side in foreign technology leader. We are looking forward to HARSVERT-VA series of speed sensorless vector control AC variable frequency speed control system can contribute more to our country's industrial electrical automation.