INVT Medium Voltage VFD in Russia Kaliningrad Water Treatment Plant

Abstract: This paper describes INVT GD5000 medium voltage frequency drive in the Kaliningrad water treatment plant in Russia, and demonstrates in detail the site-frequency operation and the technology improvement and energy saving effect of the frequency conversion reformation.

Keywords: variable frequency, speed drive, constant pressure water supply, energy saving

1. Overview

With the development of electrical power technology, VFD drive has replaced the previous multi-pump switch and valve-regulated water supply. Starting current can be limited within the rated current, avoiding any impact on the electricity system. This paper introduces INVT Medium voltage VFD PID function in the water treatment system.

2. Applications

The Kaliningrad water supply plant is mainly responsible for the water supply of the three major districts in Kaliningrad and has three water supply stations in total: 1# 2# 3# three water pumping stations. Each water station has several pumps adopting the main pipe to supply with the PID function of INVT medium voltage VFD, the water supply system will perform a constant pressure water supply program.

3. Principles of constant pressure water supply

In practical engineering, the most widely used regulator control principle is proportional, integral and differential control, referred to as PID control, and also known as PID regulation. That is to control the control amount calculated by proportion, integration, and differentiation.

The closed-loop control diagram is as follows:

Closed-loop control diagram

4. Equipment selection and system configuration

Based on site characteristic of pumps, INVT installed two 6kV/500kW medium voltage VFD and a 6kV/250kW medium voltage frequency inverter from the GD5000 series for the three water pump stations on site. The main technical parameters are as follows:

Frequency inverter in operation

Motor under load

INVT GD5000 series high-voltage frequency inverters have a built-in PID function, they are flexible to operate. The control connection can adopt a variety of modes, including hard-wired mode and communication mode. According to the actual situation of the project site, the hard-wired mode was chosen; the frequency inverter was remotely controlled by the operation column; closed-loop and open-loop operation of the system could be selected by the control panel. The frequency inverter control interface and the remote operation column are shown in the following pictures:

According to the characteristics of the on-site pump and the users' water consumption changes, combined with the functional characteristics of the GD5000 series high-voltage frequency inverter, the PID-related parameters of the on-site frequency inverter are set as follows:

5. Energy-saving effect

Project completed on April 5, 2010. INVT medium voltage drives were put on use on April 8, and the on-site pumps were tested for electricity power saving on April 11 - April 13. The test data are as follows:

1) Pump in 1# water supply station:

According to the actual readings of the electricity meter and two days of electricity consumption at grid frequency and variable frequency, the energy-saving situation of the system was calculated. After frequency conversion reformation, the comprehensive energy-saving situation of 1# water supply station is:

Electricity power saved every day = 11160 - 8400 kWh  =  2760 kWh

Energy-saving rate  = （11160 - 8400）/21720 ×100%  =  24.73%

2) Pump in 2# water supply station:

According to the actual readings of the electricity meter and two days of electricity consumption at grid frequency and variable frequency, the energy-saving situation of the system was calculated. After frequency conversion reformation, the comprehensive energy-saving situation of 2# water supply station is:

Electricity power saved every day = 9360 - 6840 kWh = 2520 kWh

Energy-saving rate = （9360 - 6840）/9360 ×100% = 26.92%

3) Pump in 3# water supply station:

According to the actual readings of the electricity meter and two days of electricity consumption at grid frequency and variable frequency, the energy-saving situation of the system was calculated. After frequency conversion reformation, the comprehensive energy-saving situation of 3# water supply station is:

Electricity power saved every day = 5280 - 3720 kWh = 1560 kWh

Energy-saving rate = （5280 - 3720）/5280  ×100% = 29.55%

6. Advantages of Medium Voltage VFD

Aboveall, after installed INVT medium voltage drive, with advance PID Control, thewater treatment plant can improved process efficiency, and get a significantenergy saving rate, reduced maintenance cost. Details contact INVT to learnmore.

References:

1.Instructions for CH100 series high-voltage frequency inverter, Shenzhen INVT Electric, 2007