Power Management in PV-Battery-HydroBased Standalone Microgrid

ABSTRACT:

This paper proposes a high-efficiency two stage three-level grid-connected photovoltaic inverter. that work deals with the frequency regulation, voltage regulation, power management and load levelling of solar photovoltaic (PV)-battery-hydro based microgrid (MG). In this MG, the battery capacity is reduced as compared to a system, where the battery is directly connected to the DC bus of the voltage source converter (VSC). A bidirectional DC–DC converter connects the battery to the DC bus and it controls the charging and discharging current of the battery. It also regulates the DC bus voltage of VSC, frequency and voltage of MG.

The proposed system manages the power flow of different sources like hydro and solar PV array. However, the load levelling is managed through the battery. Battery with VSC absorbs the sudden load changes, resulting in rapid regulation of DC link voltage, frequency and voltage of MG. Therefore, the system voltage and frequency regulation allows the active power balance along with the auxiliary services such as reactive power support, source current harmonics mitigation and voltage harmonics reduction at the point of common interconnection. Experimental results under various steady state and dynamic conditions, exhibit the excellent performance of the proposed system and validate the design and control of proposed MG.

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

Fig. 1 Microgrid Topology and MPPT Control (a) Proposed PV-battery-hydro MG,

EXPECTED SIMULATION RESULTS:

Fig. 2 Dynamic performance of PV-battery-hydro based MG following by solar irradiance change (a) vsab, isc, iLc and ivscc, (b) Vdc, Ipv, Vb and Ib, (c) vsab, isa, iLa and ivsca, (d) Vdc, Ipv, Vb and Ib

Fig.3 Dynamic performance of hydro-battery-PV based MG under load perturbation (a) vsab, isc, Ipv and ivscc, (b) Vdc, Ipv, Vb and Ib, (c) vsab, isc, Ipv and ivscc, (d) Vdc, Ipv, and Vb

 CONCLUSION: 

In the proposed MG, an integration of hydro with the battery, compensates the intermittent nature of PV array. The proposed system uses the hydro, solar PV and battery energy to feed the voltage (Vdc), solar array current (Ipv), battery voltage (Vb) and battery current (Ib). When the load is increased, the load demand exceeds the hydro generated power, since SEIG operates in constant power mode condition.

This system has the capability to adjust the dynamical power sharing among the different RES depending on the availability of renewable energy and load demand. A bidirectional converter controller has been successful to maintain DC-link voltage and the battery charging and discharging currents. Experimental results have validated the design and control of the proposed system and the feasibility of it for rural area electrification.

REFERENCES:

[1] Ellabban, O., Abu-Rub, H., Blaabjerg, F.: ‘Renewable energy resources: current status, future prospects and technology’, Renew. Sustain. Energy Rev.,2014, 39, pp. 748–764

[2] Bull, S.R.: ‘Renewable energy today and tomorrow’, Proc. IEEE, 2001, 89, (8), pp. 1216–1226

[3] Malik, S.M., Ai, X., Sun, Y., et al.: ‘Voltage and frequency control strategies of hybrid AC/DC microgrid: a review’, IET Renew. Power Gener., 2017, 11, (2), pp. 303–313

[4] Kusakana, K.: ‘Optimal scheduled power flow for distributed photovoltaic/ wind/diesel generators with battery storage system’, IET Renew. Power Gener., 2015, 9, (8), pp. 916–924

[5] Askarzadeh, A.: ‘Solution for sizing a PV/diesel HPGS for isolated sites’, IET Renew. Power Gener., 2017, 11, (1), pp. 143–151

Direct Torque Control using Switching Table for Induction Motor Fed by Quasi Z-Source Inverter

ABSTRACT:

 Z-source inverters eliminate the need for front-end DC-DC boost converters in applications with limited DC voltage such as solar PV, fuel cell. Quasi Z-source inverters offer advantages over Z-source inverter, such as continuous source current and lower component ratings. In this paper, switching table based Direct Torque Control (DTC) of induction motor fed by quasi Z-Source Inverter (qZSI) is presented.

In the proposed technique, dc link voltage is boosted by incorporating shoot through state into the switching table. This simplifies the implementation of DTC using qZSI. An additional DC link voltage hysteresis controller is included along with torque and flux hysteresis controllers used in conventional DTC. The results validate the boost capability of qZSI and torque response of the DTC.

KEYWORDS:

  1. DTC
  2. QZSI
  3. DC-DC Converter
  4. DC Link Voltage
  5. Hysteresis Controller

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 

Fig. 1: Block Diagram for DTC using qZSI

EXPECTED SIMULATION RESULTS:

 Fig.2: Torque vs. Time

Fig. 3: Stator Phase ‘a’ Current

Fig. 4: Speed vs. Time

Fig. 5: DC Link Voltage

Fig. 6: Capacitor Voltage, VC1

 CONCLUSION:

 In this paper, direct torque control of induction motor fed by qZSI is presented. Dynamic torque response for step change obtained is 3 ms, which is needed for high performance applications. qZSI provides a single stage solution for drives with variable input DC voItage, instead of DC-DC converter cascaded with 3-leg inverter bridge.

This paper presents a solution for drives with lesser DC input voItage availability and also requiring very fast torque response. The results shows that by introducing shoot through state in switching table of direct torque control, DC link voItage in qZSI is boosted. The DC link voItage hysteresis controller uses the input and capacitor voItage for controlling DC link voItage. If there is any disturbance in input voItage, the reference for capacitor voItage will be changed accordingly to maintain the DC link voItage.

REFERENCES:

 [I] 1. Takahashi and Y. Ohmori, “High-performance direct torque control of an induction motor, ” IEEE Trans. Ind. Appl., vol. 25, no. 2, pp. 257-264, 1989.

[2] B.-S. Lee and R. Krishnan, “Adaptive stator resistance compensator for high performance direct torque controlled induction motor drives, ” in Industry Applications Conference, 1998. Thirty-Third lAS Annual Meeting. The 1998 IEEE, vol. I, Oct 1998, pp. 423-430 voLl.

[3] G. Buja and M. Kazmierkowski, “Direct torque control of pwm inverter-fed ac motors-a survey, ” IEEE Trans. Ind. Electron., vol. 51, no. 4, pp. 744-757, Aug 2004.

[4] F. Z. Peng, “Z-source inverter, ” IEEE Trans. Ind. Appl., vol. 39, no. 2, pp. 504-510, Mar 2003.

[5] F. Z. Peng, A. Joseph, J. Wang, M. Shen, L. Chen, Z. Pan, E. Ortiz-Rivera, and Y. Huang, “Z-source inverter for motor drives, ” IEEE Trans. Power Electron., vol. 20, no. 4, pp. 857-863, July2005.

An Improved Beatless Control Method of AC Drives for Railway Traction Converters

ABSTRACT:  

The traction converter consists of a single phase AC DC rectifier and a three phase DC AC invert er. Due to special structural characteristics of single phase rectifier, a fluctuating voltage component with the frequency twice of the grid’s, exists in DC link voltage. Fed by fluctuating DC link voltage, a beat phenomenon occurs in traction motor, and harmonic components appear in both stat or current and electromagnetic torque, especially when motor operates near the ripple frequency. In this paper, the mechanism and influence of fluctuating voltage are analyzed in detail. Based on modeling analysis of motor and switching function of invert er, a frequency compensation factor is derived in vector control of induction motor. Then an improved frequency compensation control method is proposed to suppress beat phenomenon without LC resonant circuit. Finally the simulation verifies the modified scheme.

KEYWORDS:

  1. Fluctuating DC voltage
  2. Beat phenomenon
  3. Vector control
  4. Beat less control

 SOFTWARE: MAT LAB/SIM U LINK

 BLOCK DIAGRAM:

 Fig. 1. F O C with frequency compensation for Induction Motor

 EXPECTED SIMULATION RESULTS:

 Fig. 2. Waves of stat or current and electromagnetic torque of traction Motor

Fig. 3. FF T of stat or current and electromagnetic torque before adding frequency compensation method

Fig. 4. FF T of stat or current and electromagnetic torque after adding traditional frequency compensation method

Fig. 5. FF T of stat or current and electromagnetic torque after adding improved frequency compensation method

 CONCLUSION:

 In high power traction converters, without LC filter circuit paralleled in DC link, a fluctuating voltage twice of the grid frequency contains in DC link voltage. This paper aims at adopting software control method to suppress beat phenomenon in traction motor caused by DC ripple voltage. According to theoretical analysis, output power of motor, DC link capacitor and power factor influenced the DC ripple voltage. Then, the aspect of switching function and motor model analyzed the influences of fluctuating voltage in detail. Based on above analysis, combining with rotor field oriented control of traction motor, the frequency of switching function is modified to suppress beat phenomenon. An improved frequency compensation control method is proposed. Simulation model is built to verify the proposed scheme. Finally, the drag experiment on a dynamo meter test platform verified the proposed control method.

REFERENCES:

[1] J. K l i ma, M. Ch  o mat, L. Sch re i e r, “Analytical Closed-form Investigation of P WM Invert er Induction Motor Drive Performance under DC Bus Voltage Pulsation,” I ET Electric Power Application, Vol. 2, No. 6, pp. 341–352, Nov, 2008.

[2] H. W. van d e r Bro e ck and H. C. S k u d e l n y, “Analytical analysis of the harmonic effects of a P WM AC drive,” in IEEE Transactions on Power Electronics, vol. 3, no. 2, pp. 216-223, Apr 1988.

[3] K Na k at a, T N a k a m a chi , K Na k am u r a, “A beat less control of invert er-induction motor system driven by a rippled DC power source,” Electrical Engineering in Japan, Vol.109, No.5, pp.122-131,1989.

[4] Z Sal am, C.J. Goodman, “Compensation of fluctuating DC link voltage for traction invert er driver,” Power Electronics and Variable Speed Drives, 1996. Sixth International Conference on (Conf. Pub l. No. 429), pp. 390-395, 1996.

[5] S. K o u r o, P. Le z an a, M. An g u lo and J. Rodriguez, “Multi carrier P WM With DC-Link Ripple Feed forward Compensation for Multilevel Invert er s,” IEEE Transactions on Power Electronics, vol. 23, no. 1, pp. 52- 59, Jan. 2008.

Improved Particle Swarm Optimization For Photovoltaic System Connected To The Grid With Low Voltage Ride Through Capability

 ABSTRACT:

 Grid connected photovoltaic (PV) system encounters different types of abnormalities during grid faults; the grid side inverter is subjected to three serious problems which are excessive DC link voltage, high AC currents and loss of grid-voltage synchronization. This high DC link voltage may damage the inverter. Also, the voltage sags will force the PV system to be disconnected from the grid according to grid code. This paper presents a novel control strategy of the two-stage three-phase PV system to improve the Low-Voltage Ride-Through (LVRT) capability according to the grid connection requirement. The non-linear control technique using Improved Particle Swarm Optimization (IPSO) of a PV system connected to the grid through an isolated high frequency DCeDC full bridge converter and a three-phase three level neutral point clamped DC-AC converter (3LNPC2) with output power control under severe faults of grid voltage. The paper, also discusses the transient behavior and the performance limit for LVRT by using a DC-Chopper circuit. The model has been implemented in MATLAB/SIMULINK. The proposed control succeeded to track MPP, achieved LVRT requirements and improving the quality of DC link voltage. The paper show

KEYWORDS:

  1. Particle swarm optimization
  2. Maximum power point tracking
  3. PV system
  4. High frequency isolated converter
  5. Low voltage ride through
  6. Grid

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 

Fig. 1. Block diagram of the PV system connected to the grid.

EXPECTED SIMULATION RESULTS:

Fig. 2. PV module characteristics (a) Current-voltage characteristics (b) power-voltage characteristics.

Fig. 3. Behavior of PV array under normal condition using IPSO.

Fig. 4. DC-link voltage under normal condition using IPSO.

Fig. 5. Behavior of PV array under normal condition using IC.

Fig. 6. DC-link voltage under normal condition using IC.

Fig. 7. Behavior of grid connected inverter system under normal operation.

 

Fig. 8. The grid voltage fault.

Fig. 9. Behavior of PV array under fault condition.

Fig. 10. DC-link voltage under fault condition.

Fig. 11. Behavior of grid connected inverter system under fault condition.

Fig. 12. Behavior of PV array with LVRT capability.

Fig. 13. DC-link voltage during a grid fault with LVRT capability.

Fig. 14. Behavior of grid connected inverter system with LVRT capability.

CONCLUSION:

Based on the existing grid requirements, this paper discussed the potential of a two-stage three-phase grid-connected PV system operating in grid fault condition. The power control method proposed in this paper is effective when the system is under grid fault operation mode. It can be concluded that the future three-phase grid-connected PV systems are ready to be more active and more “smart” in the regulation of power grid.

Non-linear robust control technique using IPSO control is implemented for MPPT of 100.7 kW PV system connected to the grid. Complete control of both active and reactive powers is implemented using Matlab/Simulink with complete simulation under severe faults of grid voltage. The results show superior behavior of the IPSO; it has a faster dynamic response and better steady-state performance than the traditional algorithm; IC method, thus improving the efficiency of the photovoltaic power generation system. The use of full bridge single phase inverter with a high frequency transformer which combines the advantages of 60 Hz technology and transformer- less inverter technology, achieved MPPT requirements with IPSO. Also, this system overcomes the drawbacks of DC-chopper parameters design.

Two loops of control for the utility-connected 3LNPC2 are implemented which improve the performance of inverter and reduces the harmonics in output voltage. This control, also, increases the power injected to the grid and consequently increases the total efficiency of the system. The results show that the DC chopper circuit is capable of reducing the DC-link voltage below threshold values during the fault and protect it from failure or damage. The IPSO is capable of tracking MPP with LVRT capability included.

An anti-wind up conditioned strategy is used in order to improve the quality on the DC link voltage during and after the grid fault. It succeeds to stop accumulation of the integral part during fault, which helps system to follow up pre-faults values rapidly after clearing the fault. Finally, simulated results have demonstrated the feasibility of the IPSO algorithm and capability of MPPT in grid-connected PV systems with LVRT enhancement.

REFERENCES:

[1] Ramdan B.A. Koad, Ahmed. F. Zobaa, Comparison between the conventional methods and PSO based MPPT algorithm for photovoltaic systems, Int. J. Electr. Electron. Sci. Eng. 8 (2014) 619e624.

[2] Ali Reza Reisi, Mohammad Hassan Moradi, Shahriar Jamas, Classification and comparison of maximum power point tracking techniques for photovoltaic system: a review, Renew. Sustain. Energy Rev. 19 (2013) 433e443.

[3] N.H. Saad, A.A. Sattar, A.M. Mansour, Artificial neural controller for maximum power point tracking of photovoltaic system, in: MEPCON’2006 Conference, II, El-MINIA, Egypt, 2006, pp. 562e567.

[4] Raal Mandour I. Elamvazuthi, Optimization of maximum power point tracking (MPPT) of photovoltaic system using artificial intelligence (AI) algorithms, J. Emerg. Trends Comput. Information Sci. 4 (2013) 662e669.

[5] Saeedeh Ahmadi, Shirzad Abdi, Maximum power point tracking of photovoltaic systems using PSO algorithm under partially shaded conditions, in: The 2nd Cired Regional Conference, Tehran, Iran, 14, 2014, pp. 1e7.

A Modified Three-Phase Four-Wire UPQC Topology With Reduced DC-Link Voltage Rating

 

ABSTRACT

The unified power quality conditioner (UPQC) is a custom power device, which mitigates voltage and current-related PQ issues in the power distribution systems. In this paper, a UPQC topology for applications with non-stiff source is proposed. The proposed topology enables UPQC to have a reduced dc-link voltage without compromising its compensation capability. This proposed topology also helps to match the dc-link voltage requirement of the shunt and series active filters of the UPQC. The topology uses a capacitor in series with the interfacing inductor of the shunt active filter, and the system neutral is connected to the negative terminal of the dc-link voltage to avoid the requirement of the fourth leg in the voltage source inverter (VSI) of the shunt active filter. The average switching frequency of the switches in the VSI also reduces, consequently the switching losses in the inverters reduce. Detailed design aspects of the series capacitor and VSI parameters have been discussed in the paper. A simulation study of the proposed topology has been carried out using PSCAD simulator, and the results are presented. Experimental studies are carried out on three-phase UPQC prototype to verify the proposed topology.

KEYWORDS

  1. Average switching frequency
  2. Dc-link voltage
  3. Hybrid topology
  4. Non-stiff source
  5. Unified power quality conditioner (UPQC)

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Equivalent circuit of proposed VSI topology for UPQC compensated system (modified topology).

 EXPECTED SIMULATION RESULTS

   

Fig. 2. Simulation results before compensation (a) load currents (b) terminal voltages.

Fig. 3. Simulation results using conventional topology. (a) DC capacitor voltages (top and bottom). (b) Source currents after compensation. (c) Voltage across the interfacing inductor in phase-a of the shunt active filter. (d) Shunt active filter currents. (e) Terminal voltages with sag, DVR-injected voltages, and load voltages after compensation.

   

Fig. 4. Simulation results with modified topology. (a) Voltage across series capacitor and load voltage in phase-a. (b) Inverter output voltage in leg-a of shunt active filter. (c) DC and fundamental values of voltage across series capacitor and inverter output voltage.

Fig. 5. Simulation results using modified topology. (a) DC capacitor voltages. (b) Source currents after compensation. (c) Voltage across the interfacing inductor in phase-a of the shunt active filter. (d) Shunt active filter currents. (e) Terminal voltages with sag, DVR injected voltages, and load voltages after compensation.

     CONCLUSION

A modified UPQC topology for three-phase four-wire system has been proposed in this paper, which has the capability to compensate the load at a lower dc-link voltage under nonstiff source. Design of the filter parameters for the series and shunt active filters is explained in detail. The proposed method is validated through simulation and experimental studies in a three-phase distribution system with neutral-clamped UPQC topology (conventional). The proposed modified topology gives the advantages of both the conventional neutral-clamped topology and the four-leg topology. Detailed comparative studies are made for the conventional and modified topologies. From the study, it is found that the modified topology has less average switching frequency, less THDs in the source currents, and load voltages with reduced dc-link voltage as compared to the conventional UPQC topology.

REFERENCES

[1] M. Bollen, Understanding Power Quality Problems: Voltage Sags and Interruptions. New York: IEEE Press, 1999.

[2] S. V. R. Kumar and S. S. Nagaraju, “Simulation of DSTATCOM and DVR in power systems,” ARPN J. Eng. Appl. Sci., vol. 2, no. 3, pp. 7–13, Jun. 2007.

[3] B. T. Ooi, J. C. Salmon, J. W. Dixon, and A. B. Kulkarni, “A three phase controlled-current PWM converter with leading power factor,” IEEE Trans. Ind. Appl., vol. IA-23, no. 1, pp. 78–84, Jan. 1987.

[4] Y. Ye, M. Kazerani, and V. Quintana, “Modeling, control and implementation of three-phase PWM converters,” IEEE Trans. Power Electron., vol. 18, no. 3, pp. 857–864, May 2003.

[5] R. Gupta, A. Ghosh, and A. Joshi, “Multiband hysteresis modulation and switching characterization for sliding-mode-controlled cascaded multilevel inverter,” IEEE Trans. Ind. Electron., vol. 57, no. 7, pp. 2344–2353, Jul. 2010.