Design of Wind-solar and Pumped-storage Hybrid Power Supply System

Ruisheng Lil, Bingxin Wul, Xianwei Lil,Fengquan Zhoul,Yanbin Li2

1, Dept. ofXJ GROUP CORPORATION, Xuchang,461000,China 2, Dept. of Electronics and Information, Zhongyuan University of Technology,

Zhengzhou,450007,China

Email:wubingxincc@163.com

Abstract-To overcome the inherent defects in wind-solar hybrid system: power generation and electricity load's imbalance because of uncertainty of resources. this article aiming at XJ Group's project design of wind-solar hybrid power supply system, by way of pumped-storage to replace the battery of wind-solar hybrid power supply system, this method can effectively overcome above problems. Wind-solar and pumped-storage hybrid power supply system can reasonable configuration system capacity according to the user's electricity load and resource condition, can ensure system reliability of power supply and reduce the cost of power generation system. Wind-solar and pumped-storage hybrid power supply system greatly suited for plain and the of southern China region with relatively adequate wind energy and solar energy, establish the power system in this region will obtain a very good economic benefits and social effects of energy conservation.

Keywords-wind-solar hybrid; pumped-storage; intelligent electric grid; photovoltaic cell

I INTRODUCTION

The exploitation of wind energy and solar energy accord with a country developing new energy development trend, has a certain trend of the times and the economic value. But both wind power and photoelectric system has a common defect, it is power generation and electricity load's imbalance because of uncertainty of resources. Both wind power and photoelectric system must through battery energy storage to stabilize power supply, however, the amount of generated energy a day greatly influenced by the weather, this can result in the system battery is in a long period of power loss state, which is also the main reason of causing battery's service life reduce. If the objective conditions permit, the method of using pumped-storage to replace the battery of wind-solar hybrid power supply system can effectively overcome above problems. This energy development mode has combined the tradition develop of hydropower, solar energy and wind energy, using the differences of three kinds energy in the space-time distribution to realize the complementary development. The mode not only applies to remote areas where network coverage is difficult, but also conducive to ecological environment protect in energy development. Wind-solar and pumped-storage hybrid power supply is a kind of clean and renewable energy, do not pollute the environment, there is no

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fuel transportation, waste disposal and other issues, construction cycle is short, operation management is convenient.

II THE MODEL OF WIND-SOLAR AND PUMPED-STORAGE

HYBRID POWER SUPPLY SYSTEM

Fig.! Schematic diagram of wind-solar and pumped-storage hybrid power

supply

Wind-solar and pumped-storage hybrid power supply system contains PV generation, wind power generation, pumping and hydropower and other subsystems. According to the solar energy distribution characteristics of site area, in the area both light radiation and radiation intensity is larger during the day, it is except morning and night, the periods of light during the day are more evenly distributed, daytime distribution regularity is similar. Then from PV generation material's photoelectric effect analysis, currently, effective power generation time bears a closer relationship with the sensitivity of optical materials and no significant relationship with capacity. Therefore, it could find the corresponding starting and ending point for power generation according to different light intensity distribution during the day approximate, the period between the two points is the time of photovoltaic materials can be sensitive to the light, but also is the effective work time of photocell in the daytime. The effective period of wind power generation is also effected by the local natural conditions, specific embodied in the each period's wind size and continued stability during the daytime, could find the corresponding starting and ending point for power generation according to similar approaches, then determine the effective working days of wind turbine generator. Furthermore pumping systems affected by the impact of water source and available water supply. Water power of this system can constitute a self-circulation system

through pumping unit, external water mainly used as supplement water source, the system demand for water is lower.

Wind-solar and pumped-storage hybrid power supply system is composed by wind-solar generation system and pumped-storage system, permanent magnet synchronous generator under the action of the wind, after the rectifier control in PWM converter, sent the electricity produced to the DC bus system. At the same time, in the photovoltaic cell panels and the joint action of Boost Rectifier, DC electrical is also transported to the DC bus system. Till then, the electricity we get is DC. This part of the electricity used for two parts, one part directly supply power to ZhengZhou financial college power system under the action of grid-connected inverter, the other part power stored through the inverter and pumped-storage system, put this part of the electrical power into the power grid when the power load is lager to reduce the load of power grid.

III SPOTLIGHT TRACKING PV POWER METHOD

A. Spotlight tracking system structure diagram In the photovoltaic power system, this paper adopts the

method of spotlight tracking to generate. Spotlight tracking PV module is the core of the system components, mainly for sun collection, aggregation and transformation, mainly constituted by the primary and secondary light-gathering convergent component parts, solar receiver, radiator, and mechanical components, shown as fig.2. Primary light-gathering components is mainly complete optical first gathering, system's condensation multiple is accord with the light-gathering components; structural framework is the installation vector of all components, secondary light-gathering components complete further optical gathering. Solar receiver is solar cells through specific encapsulate, it can complete PV transformation, while the receiver have certain protection design, avoid battery damage affect whole module's power output, below of the solar receiver connect with radiator. The spotlight tracking photo voltaic power system could make the best use of solar energy, reduce PV power system's material and save cost. The materials of spotlight tracking PV power demonstration system is gallium arsenide,it is the best selection of solar panels materials on the market, in line with the application of low carbon materials in Copenhagen.

Fres nell---+",t---?'\7-:;:::=t-J I lens

str ture

cCievc4===ril-__ -.J

Fig.2 Schematic diagram of focusing system

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B. PV system efficiency calculation Grid-connected PV power system's overall efficiency

is component with PV array efficiency, inverter efficiency and AC grid-connected efficiency.

1) PV array efficiency 171

PV array efficiency171 is the ratio of PV array's actual DC power output and nominal power when solar radiation intensity is lOOOW/m2.The loss of PV array in the energy conversion process including: matching component loss, surface dust occluded loss, non-usable solar radiation loss, temperature effect, maximum power point tracking accuracy, DC circuit losses and so on, take efficiency of 85% calculation.

2) Inverter efficiency 172

Inverter efficiency 172 is the ratio of inverter's AC power and DC input power, take inverter efficiency of 95% calculation.

3) System overall efficiency 17 total

17lolal = 171 X 172 X 173 = 85% X 95% X 95% =

77%

IV PUMPED-STORAGE SYSTEM

Pumped-storage power station complement with wind-solar, their respective characteristic determines the complementary operation can get more benefit, using solar energy or wind power generation, without battery and direct drive pumps executing variable interval pumped-storage, then use the stored water to achieve a stable supply of electricity. This energy development mode has combined the tradition develop of hydropower, solar energy and wind energy, using the differences of three kinds energy in the space-time distribution to realize the complementary development. The mode not only applies to remote areas where network coverage is difficult, but also conducive to ecological environment protect in energy development. Pumped-storage system has superior performance in the voltage of stable system, so energy storage part's design of the power system adopts pumped storage, instead of battery energy storage.

In all sorts of energy in the grid, hydropower has good peak load regulation performance, can improve the power status of thermal power units in power grid, Reducing harmful gases (C02, etc.) emissions, not only improve the quality of electric power grid, but also improve local environment. At the same time can make use of valley electricity (residual electricity) pumping, power generation during peak hours, can not only peak shaving and valley filling, but also can frequency modulation and accident standby, has the functions of energy storage conversion and improve the optimization in the power system.

A.

V HARDWARE CIRCUIT DESIGN

Rectifier circuit design Rectifier circuit using single-phase full-controlled

bridge rectifier circuit, shown as fig.3, thyristorVTl and VT4 composed a pair of bridge-arm, VT2 and VT3 composed another arm of the bridge. In the positive half-cycle of U2, that is a-point potential higher than b-point potential, if none of the four thyristor conduction, the load current is zero, then the DC bus voltage of input is also zero, VTl and VT4 series withstand voltage U2. If the leakage resistance of VTl and VT4 equal, then each of them bear half of the U2.

:J T '----t--l

Fig.3 single-phase full-controlled bridge rectifier circuit

The average rectified voltage can be calculated according to the diagram:

Ud=.!.r.fl u sinmtd(mt)=2.fl u,.I+cosa=O.9U

l+cosa ,, ' ,, 2 '2

When a =0, Ud = UdO = 0.9U2 When a =180

(1)

The shift range of a are 180. Current average output to the DC bus system:

I = Ud = 2.[iU2 .l+cosa =O.9U2 .l+cosa (2) d R 1rR 2 R 2 In the selection of the transistor, the transformer

capacity, wire cross sectional area, and so on, need to consider the heating problem, therefore consider the RMS current. The RMS current flowing through thyristor is:

1 r(.flU.)' U 1 . "-a IVT= - --'smmt d(mt)= d -sm2a+--2" R v2R 2" "

(3)

I Transformer secondary current RMS 2 is equal to output DC current RMS I:

1 r(.flU,. )'d() u, 1 . "-a (4) Id=I,= - --smmt mt =- -sm2a+--" R R 2" "

404

It can be calculated from the formula, when do not taking into account the loss of transformer, the capacity of

" . .

d S = U2 xI2 translormer IS reqUlre as .

B. Grid-connect inverter design 1) Inverter main circuit design

L

Grid system

Fig.4 Grid-connect inverter design diagram

As the figure shown, inverter DC input is generally the low-voltage DC-DC bus voltage obtained through the BOOST boost Transformation, in general the amplitude of it is about 400V and the voltage fluctuation range is not large. In figure 4, in the grid system the inductance L between the inverter and the grid is used for straining higher harmonic current of grid circuit and balancing the voltage difference between grid-connected inverter and fundamental power. The design of inductance circuit is the key to the smooth operation of whole grid-connected inverter control strategy. The circuit's aberration rate and volume is smaller, its centralized control is quite simple. 2) Inverter control circuit and software process

I Current-voltage detection I Grid voltage

zerocrossing detection

Grid voltage detection

Given power

Fault alarm

Fig.S Grid-connected inverter control diagram

Grid-connected inverter control unit mainly through external detection circuit and the corresponding software algorithm to achieve the request. Through the controller to collect and display grid electric current and voltage, using PWM control algorithm to control inverter. In order to achieve a friendly man-machine interface control, using real-time communication method with the host computer, facilitate users to real-time monitoring, where the control and protection part of BOOST can separated from inverter part. However, because DSP resource is rich, we can use the same

DSP to deal with it. In this article, the core controller of grid-inverter system is a new high-speed digital signal processor TMS320F2812. Its dominant frequency is 150MHz, with 18k on-chip SRAM, 128k zero-wait RAM, 128k on-chip Flash memory, 16-channel 12bit A / D, 16-channel PWM and other functional. As TMS320F2812 is rich in on-chip resource with 16-channel 12bit A / D, using IS61LV51216 with ISSI512K word capacity, 3.3 V power supply, low power, faster data access, can meet the need of real-time data access, bring convenience to the system design.

According to the selected mode DSP controller bootstrap loading programs, jump to master program entrance, execute related variables, control registers initialized setting and sine table initialization, and so on. Then enable interrupts in need, start the timer, loop fault detection and protection and wait for the interruption. Mainly includes three parts: Periodic interrupt timer subroutine, A / D sampling subroutine and data processing algorithms and capture unit. The main program flow chart was shown in Figure 6.

EV A inlerruput 1---- SCI inlerruput

Fig.6 Grid-connected inverter main program diagram

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VI CONCLUSION

This article aiming at the wind-solar power supply system, using pumped-storage to replace the battery of wind-solar hybrid power supply system, can effectively overcome the inherent defects in wind-solar hybrid system. Wind-solar and pumped-storage hybrid power supply system can reasonable configuration system capacity according to the user's electricity load and resource condition, can ensure system reliability of power supply and reduce the cost of power generation system. This paper puts forward a few advantage of wind-solar and pumped-storage hybrid power supply system: adopts spotlight tracking photovoitaic power system, gives the system's rectifiers and grid-connected inverter's structure design and software flowchart design. Wind-solar and pumped-storage hybrid power supply system reflects the trend of development of new energy, has a very good market prospect.

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