外文翻译原文-一种控制光伏系统最大功率点的方法.pdf

See discussions, stats, and author profiles for this publication at: A Maximum Power Point Control Photovoltaic System Conference Paper July 2010 DOI: 10.1109/MED.2010.5547824 Source: IEEE Xplore CITATIONS 3 READS 80 2 authors, including: Rachid El Bachtiri Universit Sidi Mohamed Ben Abdellah 31 PUBLICATIONS 93 CITATIONS SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately. Available from: Rachid El Bachtiri Retrieved on: 25 April 2016 A Maximum Power Point Control Photovoltaic System M. Salhi, and R. El-Bachtiri Abstract A maximum power point tracking control (MPPT) is used for a photovoltaic (PV) system in order to maximize the output power irrespective of the temperature and irradiation conditions and of the load electrical characteristics. In this paper, we consider a photovoltaic panel supplying a battery. For maximizing its output power, we have used a boost DC/DC converter controlled by a PI regulator. The synthesis of this regulator parameters has been achieved by using Bode method. For having a transfer function of the system, we have used a small signal modeling. Theoretical and simulated results are presented. Experimental results are conclusive. KeywordsPhotovoltaic systems, maximum power point tracking, Boost dc/dc converter, PI regulator. I. INTRODUCTION photovoltaic generator has a nonlinear behaviour. The typical power-voltage and current-voltage characteristics of photovoltaic panel are shown in Fig. 1. The product of PV output voltage and current has a maximum value at a point called Maximum Power Point “MPP”. For the best utilization, the photovoltaic panel must operate at its MPP. However, the PV system operating point shifts out of MPP due to solar irradiation, cell temperature or load changes. When a maximum power point tracking “MPPT” regulator is inserted between the PV system and the load, it forces the system to operate at its MPP under all conditions, resulting in improved efficiency 1. Many MPPT regulators use a microcontroller or a personal computer for implementing sophistical algorithms 2-5, or even neural networks 6. These systems ensure very high performances. However they are very expensive and often need a separated, stable power supply for its operation; therefore they are only suitable for high power applications 7. Another algorithm is based on the searching of operating point which verifies . 0=VP Since the sign of “VP ” gives the direction of MPPT searching; it is possible to determine the maximum power operating by continuous measurement of power and voltage. In recent years, many MPPT applications based on this searching algorithm have been presented 8. In 9 and 10, an analog MPPT control-system is proposed, where a boost DC/DC converter is handed for having “V out I” equals zero Fig. 3, where out I is the DC/DC converter output current. In this method, in order to reduce the complexity of the Manuscript received January 13, 2010. M. Salhi is member of LESSI Laboratory in Faculty of Sciences Dhar Mehraz (FSDM), Fez, Morocco. R. El-Bachtiri is a professor in High School of Technology, Fez, Morocco. system, the battery is considered as a constant voltageEand the converter is assumed to be ideal. So, the output power b Pof DC/DC converter equals the PV output power .P A similar work is proposed in 11, that the battery is considered as a constant voltage in series with a constant resistance . b R This work is improved in 12 by taking into account the losses in the DC/DC converter, particularly, the switch losses in the MOSFET transistor. In this paper, we reconsider works proposed in 9-12 for experimental implementation. A block diagram of the proposed system is shown in Fig 3(a). A boost DC/DC converter is used to interface the PV output to the battery in order to track the maximum power point of the PV module. For That the MPPT controller must keep “VP” equals zero. What is possible with action on the duty cycle ()10 according to solar irradiation and temperature .T Duty cycle is the one of a signal generated by the PI regulator. For synthesizing the parameters of this regulator, we have developed a transfer function for the system using a small signal model. The PI regulator coefficients p K and i Kare obtained by frequency synthesis. The synoptic scheme of the proposed method is shown in Fig. 3(b). With measurements of the PV panel voltage and current, the output power is calculated and derived with respect to voltage in order to obtain the dVdP who is compared to zero. The resulting difference signal (error signal) is used as an input signal to the PI regulator which delivers a control signal GS V for the boost DC/DC. II. THEORETICAL STUDY The power electronic converter is a boost converter inserted between the PV generator and the battery Fig. 2(a). It is controlled by a signal with a duty cycle ) 10(that gives the ratio between the input and the output voltage when the conduction is continuous. The transistor is ON during Tand OFF during the rest of the period (i.e., T)1 (). The diode state, in continuous conduction mode is complementary of the transistor one. The inductance is charged through the transistor, and it is discharged, output through the diode, in the battery. If the chopping frequency is enough higher than the system characteristic frequencies, we can replace the converter with an equivalent continuous model. We will consider so the mean values, over the chopping period, of the electric quantities Fig. 2(b). A 18th Mediterranean Conference on Control and in block (converter + battery), equations (8-11) are used. The proposed controller circuit that forces the system to operate at its optimal operating point under variable temperature and irradiation conditions is shown in Fig. 7. Fig. 6. Block diagram for system simulation IsolRsh V IRs IsolRsh V IRs 0.0004 A/Kshort-circuit current temperature coefficient at Isc KI 55 Wmaximum powerPmax 17.4 Vmaximum power voltage Vmpp 3.15 Amaximum power current Impp 3.45 Ashort-circuit current Isc 21.7 Vopen-circuit voltage Vo 25 Ccell temperatureT ValueQuantity Symbol 0.0004 A/Kshort-circuit current temperature coefficient at Isc KI 55 Wmaximum powerPmax 17.4 Vmaximum power voltage Vmpp 3.15 Amaximum power current Impp 3.45 Ashort-circuit current Isc 21.7 Vopen-circuit voltage Vo 25 Ccell temperatureT ValueQuantity Symbol Y(s)0 + - PIG0(s) (s) (s) Y(s)0 + - PIG0(s) (s) (s) P V MPPT Control-system I V P converter + battery Temperature (T) V T I PV module Irradiation () P V MPPT Control-system I V P converter + battery Temperature (T) V T I PV module Irradiation () 1581 Fig. 7. Block diagram for MPPT tracker circuit. IV. PROPOSED SYSTEM Block diagrams of the proposed system are shown in Fig. 2(a) and Fig. 3(b). DC/DC converter consists of a RFP50N06 power MOSFET rated at 60V 50A .022. 0= DSon RThe flyback diode D is a fast-switching diode. The input inductor is wound around a ferrite-core with air-gap to prevent saturation that might be caused by a large DC current component value. DC/DC converter output is connected to two 12V/85Ah battery. The MPPT control-system consists of the PI regulator circuit, comparators and PV output power processing circuit. The later circuit uses the AD633JN integrated circuit for product and dividing signals. For a higher accuracy, a Hall- effect sensor is used to pick up the PV output current. The PV output voltage is collected by a differential circuit. The oscillator circuit used to obtain duty cycle is based on NE555 integrated circuit. V. RESULTS AND DISCUSSION A. Theoretical results PI controller gain and integral time constant obtained by frequency synthesis using Bode method are respectively 01. 0= p K and ms i K i T8 . 1)1(=9. The boost inductance choice is 1=LmH, and the choice of input capacitance is 7 . 4=CmF 16. For different values of irradiation and temperature T, the computation of the theoretical optimum quantities of PV output voltage mpp V and power mpp Pare assembled in table II. TABLE II THEORETICAL QUANTITIES Vmpp AND Pmpp FOR DIFFERENT VALUES OF IRRADIATION “ AND TEMPERATURE “T“. Fifteen kilohertz switching frequency is used. B. Simulation results Simulations were made to illustrate the response of the controlled system to temperature and solar irradiance rapid change. For this purpose, the irradiance and the temperature T, which are initially 100 W/m2 and 298.18 K, are switched, at 0.02 s and 0.05 s, to 1000 W/m2 and 320.18K respectively Fig. 8(a) and (b). And vice versa Fig. 9(a) and (b). , i.e., the solar irradiance changes from 1000 W/m2 to 100 W/m2 at 0.02 s and the temperature changes from 320.18 K to 298.18 K at 0.05 s. Optimum values of PV output power and voltage obtained by simulations are assembled in table III. Locking table II and table III, it is clear, on one hand that the average PV output power and voltage are very close to their optimal values Vmpp and Pmpp. And, on the other hand, the values obtained by simulation coincide with those obtained by programming. Simulations of the MPPT behaviour show that the system is stable. Oscillations around the computed optimal operating point are due to the switching action of the DC/DC converter. TABLE III SIMULATED QUANTITIES Vmpp AND Pmpp FOR DIFFERENT VALUES OF IRRADIATION “ AND TEMPERATURE “T“. C. Experimental results A prototype of the MPPT system has been developed using the above-described method and tested in the laboratory. The boost DC/DC converter, consisting of a MOSFET transistor, a fast switching diode, and an input inductor, has been carried out. Not having a material for measuring irradiation , in order to perform experience, we have proceeded as follows: In a dark room (no wind nor daylight), we have used LMP EJH 24V - 250 W overhead projector to give out the light to the PV array for a given temperature T1 (285 K) and irradiation 1. In these conditions (1 and T1 are supposed unvarying), we have measured, on one hand, the open-circuit voltage o V (= 19.5 V) and the Short-circuit current sc I(=80.5mA). On the other hand, we have achieved a series of measurements of PV output current and voltage by varying a load. Results of measurements are used to plot the PV power-voltage characteristic in order to determine the optimal operating point “MPP1” corresponding to irradiation 1 and temperature T1 Fig. 10. Values of (W/m2) and T (K)Vmpp(V)Pmpp(W) = 100 and T = 298.18 = 1000 and T = 298.18 = 1000 and T = 320.18 = 100 and T = 320.18 14.25 17.39 15.65 12.31 4.393 54.80 48.61 3.715 Values of (W/m2) and T (K)Vmpp(V)Pmpp(W) = 100 and T = 298.18 = 1000 and T = 298.18 = 1000 and T = 320.18 = 100 and T = 320.18 14.25 17.39 15.65 12.31 4.393 54.80 48.61 3.715 Values of (W/m2) and T (K)Vmpp(V)Pmpp(W) = 100 and T = 298.18 = 1000 and T = 298.18 = 1000 and T = 320.18 = 100 and T = 320.18 14.25 17.41 15.66 12.31 4.396 54.83 48.64 3.549 Values of (W/m2) and T (K)Vmpp(V)Pmpp(W) = 100 and T = 298.18 = 1000 and T = 298.18 = 1000 and T = 320.18 = 100 and T = 320.18 14.25 17.41 15.66 12.31 4.396 54.83 48.64 3.549 Alpha P dP/dt MATLAB 1/(dV/dt) dV/dt V PI regulator - + Function Ground (dP/dV) Alpha P dP/dt MATLAB 1/(dV/dt) dV/dt V PI regulator - + Function Ground (dP/dV) 1582 First, we have connected the PV module to the input of DC/DC converter and we have connected the output of the DC/DC converter to the battery. After that, we have used the output signal VGS provided from the MPPT control-system Fig. 12 to control the gate of MOSFET transistor. The MPPT tracker led operating point to reach its optimal value “MPP1”. Experimental results are shown in Fig. 10, Fig. 11(a) and (b), and Fig. 12. Using the power-voltage characteristic for = 1 and T = T1 Fig. 10, PV optimal voltage and optimal corresponding power to The MPP1 are: 12 1 = mpp VV and 6 .717 1max =P mW. Measured corresponding current is 8 .59 1 = mpp ImA. Using the MPPT tracker, we have obtained an optimal operating point corresponding to the maximum power voltage Fig. 11(a) 5 .12 2 = mpp VV and the maximum power current Fig. 11(b) 59 2 = mpp I mA. So, the maximum corresponding power is 5 .737 2max =P mW. Fig. 8. Variation of: (a) PV output power and (b) PV output voltage for a step change on irradiation and temperature from 100 W/m2 to 1000 W/m2 and 298.18 K to 320.18 K respectively. These results show that the use of the proposed MPPT control increases the PV output power, voltage, and current like 2.77 %, 4% and 1.36 % respectively. VI. CONCLUSION The PV system output power can be maximized using MPPT control system. It consists of a power converter to interfacing the PV output to the load, driven by a control unit to extract the maximum power from a PV generator. A low- cost MPPT system for battery charging has been developed and tested. The power converter is a boost dc/dc converter. Its controlled by a PI regulator. This PI regulator has been synthesized by frequencial synthesis using Bode method. For a given temperature T and solar irradiance , we have calculated the corresponding optimal values Vmpp and Pmpp. Experimental and simulation results show that the proposed method was able to track the maximum power point for a given temperature T and irradiance. Our proposed MPPTs charge controller is easier and cheaper to build. Fig. 9. Variation of: (a) PV output power and (b) PV output voltage for a step change on irradiation and temperature from 1000 W/m2 to 100 W/m2 and 320.18 K to 298.18 K respectively. PV output voltage (V) 00.020.040.060.080.1 0 5 10 15 20 25 Time (s) (b) PV output voltage (V) 00.020.040.060.080.1 0 5 10 15 20 25 Time (s) (b) 00.020.040.060.080.1 -30 -20 -10 0 10 20 30 40 50 60 Time (s) PV output power (W) (a) 00.020.040.060.080.1 -30 -20 -10 0 10 20 30 40 50 60 Time (s) PV output power (W) (a) 00.020.040.060.080.1 -20 -15 -10 -5 0 5 10 15 20 25 Time (s) PV output voltage (V) (b) 00.020.040.060.080.1 -20 -15 -10 -5 0 5 10 15 20 25 Time (s) PV output voltage (V) 00.020.040.060.080.1 -20 -15 -10 -5 0 5 10 15 20 25 Time (s) PV output voltage (V) (b) 00.020.040.060.080.1 -50 -40 -30 -20 -10 0 10 20 30 40 50 Time (s) PV output power (W) (a) 00.020.040.060.080.1 -50 -40 -30 -20 -10 0 10 20 30 40 50 Time (s) PV output power (W) 00.020.040.060.080.1 -50 -40 -30 -20 -10 0 10 20 30 40 50 Time (s) PV output power (W) (a) 1583 Fig. 10. Power-voltage characteristic for irradiation 1 and temperature T1. Fig. 11. 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