Induction motor under open-end winding fed by dual PV source for pumping application

Induction motor

Presented in Partial Fulfillment of the Requirements for the Degree of Master in Electrical Engineering
Sector: Electrotechnics. Specialty: Electrical Control
Realized By: Menzou Mohaned and Kobbi Mohammed EL-A. Supervisor: Dr. KHADAR Saad

In this work, we present a study on a system that uses PV solar energy to pump water for irrigation, along with an assessment of the cost of this application.

The pumping chain studied in our case, equipped with an MPPT control, uses an open-end stator winding induction motor (OESW-IM) and drives a centrifugal pump.

1. The utilization of an induction motor offers a superior alternative to commercial DC motor-based water pumping systems, aiming for improved efficiency, reliability, and cost-effectiveness.
2. The OESWIM is connected via three-phase inverters powered by independent DC-DC Boost converters and controlled by an MPPT algorithm.
3. The dual inverter drive is controlled by Backstepping control, which is based on the Lyapunov function, to ensure local stability of the system.
4. Simulation results demonstrate favorable performance in both transient and steady states. Additionally, an economic comparison among different water pumping methods highlights the cost per cubic meter of water, considering various influential factors. The findings suggest that the cost may vary based on location-specific parameters.
5. While our calculations provide insights into cost levels. The future is expected to witness price reductions in system components. The developed system holds great promise for deployment in isolated locations and for providing water access to poor communities.

General Introduction :

Global energy use in recent decades has been associated with industrial development. As we all know, non-renewable resources (fossil fuels) such as oil, coal, natural gas, or nuclear energy account for around 68% of global energy output. Recent research and projections warn that massive usage of these resources would inevitably deplete these reserves and endanger the ecosystem.

Algeria boasts one of the world’s largest solar reserves. Almost the majority of the national territory has more than 2000 hours of sunshine each year, with certain areas seeing up to 3900 hours. In the majority of the national area, the energy received daily on a horizontal surface of 1 m² is on the order of 5 kWh. Photovoltaic (PV) energy is pure and non-polluting, and its utilization provides an infinite supply of energy.

Given that water supply for agricultural purposes is still a daily problem for people living in Saharan areas. Solar pumping systems are especially well adapted for water delivery from wells or boreholes. PV pumping is one of the uses of PV solar energy in remote locations. This technology is still in development and has a gradually decreasing cost.

Energy production based on PV solar energy has significant potential among all available renewable energies. It is clean, inexhaustible, and available over a large part of the globe.

Chapter 1: Description and Modeling of a PV System Connected via DC-DC Converter

In the first general chapter, we start with the principle of PV conversion and the different topologies of PV systems. Then we will recall the constitution of a PVG and the modeling of a PV cell.

We first present taking into account the influence of the different climatic parameters, allowing us to determine the I-V and P-V characteristics as well as the influence of internal and external parameters.

Thereafter, we present a mathematical modeling of the boost DC-DC converter for an induction motor, which will play the role of an impedance adapter and whose duty cycle a MPPT algorithm generates.

1. Photovoltaic Generator:
2. Photovoltaic Module:
3. Simulation of PV Modules:
4. PV System Converter:
5. Control of the Boost DC-DC Converter.

Simulation of the PV System Connected via DC-DC Converter.

Two distinct climatic circumstances were evaluated in Figure a, which illustrate the irradiance and temperature at which the PV array is generated at various values. Figures b, and c show the PV characteristics respectively, when the temperature ranged from 25ºC to 40ºC and the irradiance ranged from 300W/m² to 1000W/m². We can see from the P=f(t) characteristic that the INC approach oscillates a lot more, which is approximately MPP. Another finding is that altering the insolation and temperature causes a change in the PV variables like the voltage, current, and power. It is also evident from the waveform simulation results provided in Figures shows that the value of voltage and power increases with increasing irradiance and temperature and decreases with their decrease.

Chapter 2: Modeling and Simulation of Motor-Pump

Numerous industrial and domestic applications depend heavily on water pumps and three-phase induction motor. Their widespread use is attributed to their high effectiveness to function in challenging conditions. It is possible to improve these components’ performance through modeling and simulation, leading to greater reliability and improved energy efficiency.

The second chapter contains the mathematical modeling of the three-phase induction motor (TPIM) and the centrifugal pump, presenting the advantages and disadvantages of the motor-pump assembly and its applications. The transformation matrix (stationary, rotor, and synchronous) for induction motors is also explained. Finally, we end our chapter with the TPIM Model simulation results in the stationary reference frame.

1. General information on water pumps:
2. Construction and Operation of a Centrifugal Pump:
3. Modeling of the Water Pump:
4. The Advantages and Disadvantages of Centrifugal Pumps:
5. Description of a Three-Phase Induction Motor:
6. Modeling of the Induction Motor:
7. Final Model for an induction motor.

Simulation Results:

Figure 10 represents an illustration or schematic of an Induction motor connected to a pump. The motor is responsible for converting electrical energy into mechanical energy, which drives the pump to move or circulate fluids.

Chapter 3: Open-End Stator Winding Induction Motor

Power electronics converters, especially voltage source inverters (VSI), are a critical component of today’s power system, allowing for growing renewable energy sources, high-efficiency motor drive systems, and a wide range of utility-level applications.

Research into novel topologies and control systems for high-performance applications is ongoing, to find cost-effective solutions that improve the efficiency and resilience of prior iterations. This chapter contributes by presenting a control technique for an open-end stator winding induction motor system.

The suggested control makes use of the intrinsic properties of the drive topology to automatically ensure the ideal rated motor power factor over the entire load and speed range of the machine, assuring energy savings while operating at high efficiency.

Chapter 3 provides an overview of why researchers have become interested in multilevel switch topologies in recent years, introducing types of multilevel switch topologies with different OESW Induction motor configurations.

Similarly, a space vector pulse width modulation (SVPWM) approach is provided to control the TPIM-OESW topology.

1. Multilevel Inverter Topology:
2. Types of Multilevel Converter Topologies:
3. Open-End Stator Winding Topology:
4. Advantages and Applications:
5. Control of Open-End Stator Winding Topology:
6. Schematic Circuit of an OESW Induction motor fed by a dual boost converter

Simulation Results:

 Figure 15, displaying the rotor speed, showcases the dynamic behavior of the motor. The plot's upward trend indicates an increasing speed over time. By examining the slope of the curve, it is possible to assess the acceleration or deceleration of the motor during different time intervals. Any irregularities or sudden changes in the speed profile might indicate issues such as load fluctuations or disturbances within the system.

 Figure 16, depicting the torque of the motor and the pump, is crucial for understanding the load characteristics and power requirements of the system. The plot showcases the torque values as a function of time. Peaks or spikes in torque indicate moments of high mechanical demand. Analyzing the correlation between torque changes and other variables, such as the speed from Figure 16, can provide insights into the motor's efficiency and the pump's performance. Figure 17 focuses on the stator current, including Isa and Isb. The plot offers a glimpse into the electrical behavior of the system during startup and normal operation. Isa provides information about the internal starting arrangement used within the motor to facilitate its starting process. 

Figure 18, which represents the hydraulic power, provides insights into the power output of the pump. Hydraulic power is a measure of the energy transferred by the fluid being pumped. This plot allows us to evaluate the efficiency and effectiveness of the pump in converting mechanical power from the motor into hydraulic power.

Chapter 4: Nonlinear Backstepping Control of the Proposed System

The 1990s saw the creation of backstepping, a potent control theory technique, by Petar V. Kokotovic and others.

Backstepping is based on the second method of the Lyapunov technique, a powerful tool for evaluating and identifying the prerequisites for the stability of various dynamic systems. The technique is flexible and effective for control system design because it does not require actual numerical solutions of differential equations but only the construction of an appropriate.

The fourth chapter introduces the backstepping nonlinear control theory (first and second steps) and its objective. In addition, this chapter discusses the backstepping control scheme along with the SVPWM technique to control the Dual PV source-based dual DC-DC Boost Converter fed by an induction motor OESW for Pumping applications.

1. An Overview of Nonlinear Control Strategies:
2. Objective of Nonlinear Control:
3. Description of Backstepping Control:
4. Backstepping Control Theory:
5. Backstepping Control of the OESW-Induction Motor:
6. Schematic Circuit Diagram of the Proposed System.

Performance under High Speed Operation:

 In this test, the studied motor is operated at the high speed operation with load torque (pump). The simulation results of non lineaire Backsepping with speed sensor are shown in Figure 20. The used reference speed consists of two phases ; the first phase varies linearly from zero to the value of the steady state (300 rad/s) which is reached in 0.4 sec. Whereas, the second phase it presents the steady state speed which is constant as shown in Figure 20. The reference rotor flux is fixed to 1Wb. Figure 20 shows the reference and the real rotor speed for proposed Backstepping control of the studied motor, it is noted that the real rotor speed follows perfectly its reference (300 rad/s) which is achieved very rapidly, with a very fast response. Also, the peak overshoot with Backstepping technique is eliminated compared to other control. The speed error is very small, this indicates that the proposed Backstepping control has good performance. While Figure 21 shows the developed electromagnetic torque by the studied motor. The electromagnetic torque of OESW-IM topology presents a good high dynamic with acceptable torque ripples and confirms the performances of the Backstepping control in terms of reduce overshoot, which proves the robustness of the proposed Backstepping control. Figure 22 shows the rotor. It’s observed that the rotor flux fellow the reference value of the rotor quickly (0.08 sec). This result proves that the full decoupling between the torque and flux is maintained. Besides, the three phase stator currents of the OESW-IM are shown in Figure 23, the steady state value is constant amplitude, where a sinusoidal waveform is obtained with reduced harmonic content owing to the application of SVM technique. Figure 24 shows the hydraulic power of the pumps.

Performance under Reverse Speed Operation:

Checking the robustness of the Backstepping control of the studied motor, it is nececearly to check it with speed sensor under reversal speed operation. Therefore, a reverse speed tests has been performed following the reference speed, which varies in two steps, from zero to 300 rad/sec and from 300 (rad/s) to -300 (rad/s) as shown in Figure 25. The reference and the real rotor speed for proposed Backstepping control of the studied motor are shown in Figure 25. It is found that the rotor speed follows the reference value without overshoot. The speed error rapidly converging to zero each sudden change of reference speed, this result demonstrates the high performance of the Backstepping control even during reversal speed operation. Furthermore, it is observed clearly in Figure 26 that the developed electromagnetic torque by the motor tracks the profile of the load torque along the imposed reference speed profile. However, during the transient steps of the speed, the developed torque recovers this based on the Backstepping control by increasing its value according to the occurred variation characteristics (time and range). From Figure 27, the three phase stator currents present sinusoidal waveforms during reversal-speed operation.

Chapter 5: Sizing of a PV Pumping System with a Comparative Study with Pumping by Electrical Network

Indeed, the development of dependable and efficient pumping systems is a realistic and inexpensive solution to the problem of surface water shortages in desert regions. In this chapter, we have given a three-method scaling application on a solar pumping system, addressing local demands in the Djelfa region. We point out that often, the worry of investment is a priority above the efficiency of the system. We will also analyze the effectiveness of the installation.

In the last chapter, a numerical application is presented to the dimensioning of the solar pumping system for the studied zone (DJELFA). After an explanation of the rules of choice for an energy system and all the parameters necessary for the design and dimensioning of our irrigation system. We ended this chapter with a comparative technical and economic study between the two energy sources for water pumping and the evaluation of the total cost of the system, as well as a cost comparison with a traditional pumping system power source, which is the electrical network, that allowed us to better see the advantages and disadvantages of each source.

1. Sizing Methods:
2. Component of the PV Pumping System:
3. Analysis of Results According to SONELGAZ:
4. Cost of the Installation with the Creation of a 1-Km MV Network (SONELGAZ):
5. Installation Cost Comparison Results

General Conclusion :

The photovoltaic effect and characteristics of PV modules are just a few of the topics covered in the introduction, which also describes and models a PV system connected via a DC-DC Converter.

Additionally, it provides a thorough analysis of boost DC-DC Converter control and goes into more detail about the converters used in PV systems. A general overview of water pumps and a description of an induction motor are covered.

The OESW-IM is the subject of the following discussion, which also covers its theory and different configurations.

The memory also includes a thorough economic analysis comparing the price per cubic meter of water for various pumping techniques. The study considers a number of variables that may affect costs and offers information on potential cost savings and efficiency gains offered by the OESW-IM system.

Before introducing the nonlinear Backstepping control for the suggested system, the thesis concludes with an overview of nonlinear control techniques and stability analysis methods. A thorough explanation of the Backstepping control theory and how it applies to the OESW-IM is provided. The memory concludes with simulation results that show how the suggested system performs under various operating circumstances.