STATCOM-Based Voltage Regulator for Self-Excited Induction Generator Feeding Nonlinear Loads

ABSTRACT:

This paper deals with the performance analysis of a static compensator (STATCOM)-based voltage regulator for self-excited induction generators (SEIGs) supplying nonlinear loads. In practice, a number of loads are nonlinear in nature, and therefore, they inject harmonics in the generating systems. The SEIG’s performance, being a weak isolated system, is very much affected by these harmonics. The additional drawbacks of the SEIG are poor voltage regulation and that it requires an adjustable reactive power source with varying loads to maintain a constant terminal voltage. A three-phase insulated-gate-bipolar transistor- based current-controlled voltage source inverter working as STATCOM is used for harmonic elimination, and it provides the required reactive power for the SEIG, with varying loads to maintain a constant terminal voltage. A dynamic model of the SEIG–STATCOM feeding nonlinear loads using stationary d−q axes reference frame is developed for predicting the behaviour of the system under transient conditions. The simulated results show that SEIG terminal voltage is maintained constant, even with nonlinear balanced and unbalanced loads, and free from harmonics using STATCOM-based voltage regulator.

KEYWORDS:

1.      Harmonic elimination

2.       Load balancing

3.       Nonlinear loads

4.       Self-excited induction generator (SEIG)

5.       Static compensator (STATCOM)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Schematic diagram of proposed scheme of SEIG–STATCOM system

CONTROL SYSTEM:

Fig.2 Control scheme of SEIG–STATCOM system.

EXPECTED SIMULATION RESULTS:

Fig. 3. Voltage buildup of SEIG and switching in STATCOM.

Fig. 4. Waveform of three-phase SEIG–STATCOM system supplying diode rectifier with resistive load change from no load, to three-phase (22 kW), to one-phase (15 kW), to three-phase (22 kW) loads, and to no load.

Fig. 5. Waveform of three-phase SEIG–STATCOM system supplying diode rectifier with capacitive filter and resistive load change from no load, to three-phase (15 kW), to one-phase (24 kW), to three-phase (15 kW) loads, and to no load.

Fig. 6. Waveforms of three-phase SEIG–STATCOM system supplying diode rectifier with capacitive filter and resistive load change from no load, to three-phase (15 kW), to three-phase (22 kW), to three-phase (15 kW) loads, and to no load.

Fig. 7. Waveforms of three-phase SEIG–STATCOM system supplying thyristorized rectifier with resistive load change from no load, to three-phase (18 kW) at 60◦ firing angle, to no load.

CONCLUSION:

It has been observed that the developed mathematical model of a three-phase SEIG–STATCOM is capable of simulating its performance while feeding nonlinear loads under transient conditions. From the simulated results, it has been found that the SEIG terminal voltage remains constant, with the sinusoidal feeding of the three-phase or single-phase rectifiers with resistive and with dc capacitive filter and resistive loads. When a single-phase rectifier load is connected, the STATCOM balances the unbalanced load currents, and the generator currents and voltage remain balanced and sinusoidal; therefore, the STATCOM acts as a load balancer. The rectifier-based nonlinear load generates the harmonics, which are also eliminated by STATCOM. Therefore, it is concluded that STATCOM acts as voltage regulator, load balancer, and harmonic eliminator, resulting in an SEIG system that is an ideal ac power-generating system.

REFERENCES:

[1] C. Grantham, D. Sutanto, and B. Mismail, “Steady state and transient analysis of self-excited induction generator,” Proc. Inst. Electr. Eng., vol. 136, no. 2, pp. 61–68, Mar. 1989.

[2] K. E. Hallenius, P. Vas, and J. E. Brown, “The analysis of saturated selfexcited asynchronous generator,” IEEE Trans. Energy Convers., vol. 6, no. 2, pp. 336–341, Jun. 1991.

[3] M. H. Salama and P. G. Holmes, “Transient and steady-state load performance of a stand-alone self-excited induction generator,” Proc. Inst. Electr. Eng.—Electr. Power Appl., vol. 143, no. 1, pp. 50–58, Jan. 1996.

[4] L. Wang and R. Y. Deng, “Transient performance of an isolated induction generator under unbalanced excitation capacitors,” IEEE Trans. Energy Convers., vol. 14, no. 4, pp. 887–893, Dec. 1999.

[5] S. K. Jain, J. D. Sharma, and S. P. Singh, “Transient performance of threephase self-excited induction generator during balanced and unbalanced faults,” Proc. Inst. Electr. Eng.—Generation Transmiss. Distrib., vol. 149, no. 1, pp. 50–57, Jan. 2002.

Simulation and Control of Solar Wind Hybrid Renewable Power System

ABSTRACT:

The sun and wind based generation are well thoroughly considered to be alternate source of green power generation which can mitigate the power demand issues. This paper introduces a standalone hybrid power generation system consisting of solar and permanent magnet synchronous generator (PMSG) wind power sources and a AC load. A supervisory control unit, designed to execute maximum power point tracking (MPPT), is introduced to maximize the simultaneous energy harvesting from overall power generation under different climatic conditions. Two contingencies are considered and categorized according to the power generation from each energy source, and the load requirement. In PV system Perturb & Observe (P&O) algorithm is used as control logic for the Maximum Power Point Tracking (MPPT) controller and Hill Climb Search (HCS) algorithm is used as MPPT control logic for the Wind power system in order to maximizing the power generated. The Fuzzy logic control scheme of the inverter is intended to keep the load voltage and frequency of the AC supply at constant level regardless of progress in natural conditions and burden. A Simulink model of the proposed Hybrid system with the MPPT controlled Boost converters and Voltage regulated Inverter for stand-alone application is developed in MATLAB.

KEYWORDS:

1.      Renewable energy

2.      Solar

3.      PMSG Wind

4.       Fuzzy controller

5.       P&O

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Block diagram of PV-Wind hybrid system

EXPECTED SIMULATION RESULTS:

Figure 2. PV changing irradiation level

Figure 3. Output voltage for PV changing irradiation level

  

Figure 4. Wind speed changing level

Figure 5. Output current wind

Figure 6. Output Voltage wind

Case 1 : PI voltage regulated inverter

Figure 7. Output voltage for inverter

Figure 8. Power generation of the hybrid system under varying wind speed and irradiation

Case 2 : fuzzy logic voltage regulated inverter

Figure 9. Output voltage for inverter

Figure 10. Power generation of the hybrid system under varying wind speed and irradiation

CONCLUSION:

Nature has provided ample opportunities to mankind to make best use of its resources and still maintain its beauty. In this context, the proposed hybrid PV-wind system provides an elegant integration of the wind turbine and solar PV to extract optimum energy from the two sources. It yields a compact converter system, while incurring reduced cost.

The proposed scheme of wind–solar hybrid system considerably improves the performance of the WECS in terms of enhanced generation capability. The solar PV augmentation of appropriate capacity with minimum battery storage facility provides solution for power generation issues during low wind speed situations.

FLC voltage regulated inverter is more power efficiency and reliable compared to the PI voltage regulated inverter, in this context FLC improve the effect of the MPPT algorithm in the power generation system of which sources solar and wind power generation systems.

REFERENCES:

[1] Natsheh, E.M.; Albarbar, A.; Yazdani, J., "Modeling and control for smart grid integration of solar/wind energy conversion system," 2^nd IEEE PES International Conference and Exhibition on Innovative Smart Grid Technologies (ISGT Europe),pp.1-8, 5-7 Dec. 2011.

[2] Bagen; Billinton, R., "Evaluation of Different Operating Strategies in Small Stand-Alone Power Systems," IEEE Transactions on Energy Conversion, vol.20, no.3, pp. 654-660, Sept. 2005

[3] S. M. Shaahid and M. A. Elhadidy, “Opportunities for utilization of stand-alone hybrid (photovoltaic + diesel + battery) power systems in hot climates,” Renewable Energy, vol. 28, no. 11, pp. 1741–1753, 2003.

[4] Goel, P.K.; Singh, B.; Murthy, S.S.; Kishore, N., "Autonomous hybrid system using PMSGs for hydro and wind power generation," 35^th Annual Conference of IEEE Industrial Electronics, 2009. IECON '09, pp.255,260, 3-5 Nov. 2009.

[5] Foster, R., M. Ghassemi, and A. Cota, Solar energy: renewable energy and the environment. 2010, Boca Raton: CRC Press.

A Combination of Shunt Hybrid Power Filter and Thyristor-Controlled Reactor for Power Quality

ABSTRACT:

This paper proposes a combined system of a thyristor-controlled reactor (TCR) and a shunt hybrid power filter (SHPF) for harmonic and reactive power compensation. The SHPF is the combination of a small-rating active power filter (APF) and a fifth-harmonic-tuned LC passive filter. The tuned passive filter and the TCR form a shunt passive filter (SPF) to compensate reactive power. The small-rating APF is used to improve the filtering characteristics of SPF and to suppress the possibility of resonance between the SPF and line inductances. A proportional–integral controller was used, and a triggering alpha was extracted using a lookup table to control the TCR. A nonlinear control of APF was developed for current tracking and voltage regulation. The latter is based on a decoupled control strategy, which considers that the controlled system may be divided into an inner fast loop and an outer slow one. Thus, an exact linearization control was applied to the inner loop, and a nonlinear feedback control law was used for the outer voltage loop. Integral compensators were added in both current and voltage loops in order to eliminate the steady-state errors due to system parameter uncertainty. The simulation and experimental results are found to be quite satisfactory to mitigate harmonic distortions and reactive power compensation.

KEYWORDS:

1.      Harmonic suppression,

2.      Hybrid power filter

3.      Modeling

4.      Nonlinear control

5.      Reactive power compensation

6.      Shunt hybrid power filter and thyristor-controlled reactor (SHPF-TCRcompensator)

7.      Thyristor-controlled reactor (TCR)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Basic circuit of the proposed SHPF-TCR compensator.

EXPECTED SIMULATION RESULTS:

                                  Fig. 2. Steady-state response of the SHPF-TCR compensator with harmonic generated load.

Fig. 3. Harmonic spectrum of source current in phase 1. (a) Before compensation.

(b) After compensation.

Fig. 4. Dynamic response of SHPF-TCR compensator under varying distorted

harmonic type of load conditions.

Fig. 5. Dynamic response of SHPF-TCR compensator under the harmonic and reactive power type of loads.

Fig. 6. Harmonic spectrum of source current in phase 1. (a) Before compensation. (b) After compensation.

Fig. 7. Steady-state response of the SHPF-TCR compensator with harmonic produced load.

CONCLUSION:

In this paper, a SHPF-TCR compensator of a TCR and a SHPF has been proposed to achieve harmonic elimination and reactive power compensation. A proposed nonlinear control scheme of a SHPF-TCR compensator has been established, simulated, and implemented by using the DS1104 digital realtime controller board of dSPACE. The shunt active filter and SPF have a complementary function to improve the performance of filtering and to reduce the power rating requirements of an active filter. It has been found that the SHPF-TCR compensator can effectively eliminate current harmonic and reactive power compensation during steady and transient operating conditions for a variety of loads. It has been shown that the system has a fast dynamic response, has good performance in both steady-state and transient operations, and is able to reduce the THD of supply currents well below the limit of 5% of the IEEE-519 standard.

REFERENCES:

[1] A. Hamadi, S. Rahmani, and K. Al-Haddad, “A hybrid passive filter configuration for VAR control and harmonic compensation,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2419–2434, Jul. 2010.

[2] P. Flores, J. Dixon, M. Ortuzar, R. Carmi, P. Barriuso, and L. Moran, “Static Var compensator and active power filter with power injection capability, using 27-level inverters and photovoltaic cells,” IEEE Trans. Ind. Electron., vol. 56, no. 1, pp. 130–138, Jan. 2009.

[3] H. Hu, W. Shi, Y. Lu, and Y. Xing, “Design considerations for DSPcontrolled 400 Hz shunt active power filter in an aircraft power system,” IEEE Trans. Ind. Electron., vol. 59, no. 9, pp. 3624–3634, Sep. 2012.

[4] X. Du, L. Zhou, H. Lu, and H.-M. Tai, “DC link active power filter for three-phase diode rectifier,” IEEE Trans. Ind. Electron., vol. 59, no. 3, pp. 1430–1442, Mar. 2012.

[5] M. Angulo, D. A. Ruiz-Caballero, J. Lago, M. L. Heldwein, and S. A. Mussa, “Active power filter control strategy with implicit closedloop current control and resonant controller,” IEEE Trans. Ind. Electron., vol. 60, no. 7, pp. 2721–2730, Jul. 2013.

Offshore Wind Farms - VSC-based HVDC Connection

ABSTRACT:

Due to significantly higher and more constant wind speeds and the shortage of suitable sites for wind turbines on the land, offshore wind farms are becoming very attractive. The connection of the large offshore wind farms is possible with HVAC, classical HVDC and Voltage Source Converter (VSC based) HVDC technology. In this paper their main features will be given. From the economical and technical viewpoint, the type of connection depends on the size of the wind farm and on the distance to the connection point of the system.

As very promising technology, especially from the technical viewpoint, the focus of this paper will be put on the VSC-based HVDC technology. Its main technical features as well as its model will be detailed. At the end, obtained simulation results for different faults and disturbances for one offshore wind farm connected with VSC-based HVDC technology will be presented.

KEYWORDS:

1.      HVDC

2.      IGBT

3.      Offshore wind farm connection

4.       PWM

5.      Requirements

6.       Stability

7.       VSC

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Principal scheme of VCS-based HVDC connection

EXPECTED SIMULATION RESULTS:

Fig. 2. Active and reactive power at the connection point during reactive power control

Fig. 3. Active and reactive power at the wind farm side during reactive power control

Fig. 4. Active power, reactive power and voltage at system and wind farm side in case of single phase short circuit near to the connection point - 100ms

Fig. 5. Active power, reactive power and voltage at system and wind farm side in case of single phase short circuit at the wind farm side - 100ms

CONCLUSION:

The connection of an offshore wind farm depends primarily on the amount of power that has to be transmitted and the distance to the connection point.

Primarily due to comparatively small size and short distance to the connection point as well as due to its lower costs and experience, all actual offshore wind farms and those planned to be installed are still using/plan to use HVAC connection.

The advantages of using a HVDC solution are more significant with increase of the distance and power.

The VSC-based HVDC technology is due to its technical advantages like: active and, especially, reactive power control (voltage control), isolated operation, no need for an active commutation voltage etc. very good solution for an offshore wind farm connection. Performed simulation and their results of simulated faults and disturbances show that the technical requirements can be fulfilled.

REFERENCES:

[1] European Wind Energy Association. (2004). Wind Energy – The Facts. [Online]. Available: http://www.ewea.org

[2] Global Wind Energy Council. (2004). [Online]. Available: http://www.gwec.net

[3] F.W. Koch, I. Erlich, F. Shewarega, and U. Bachmann, "Dynamic interaction of large offshore wind farms with the electric power system", in Proc. 2003 IEEE Power Tech Conf., Bologna, Italy, vol. 3, pp. 632-638.

[4] J.G. Slootweg and W.L. Kling, "Is the Answer Blowing in the Wind?", IEEE Power and Energy Magazine, vol. 1, pp. 26-33, Nov./Dec. 2003.

[5] Wind Energy Study 2004. [Online]. Available: http://www.ewea.org