CN105591382A - Network source coordination power control method of isolated photovoltaic direct current microgrid - Google Patents

Abstract

The present invention discloses a network source coordination power control method of an isolated photovoltaic direct current microgrid. The network source coordination control is realized through adoption of each current transformer and multi-source regulation potential in a system. A storage battery side employs a constant direct current voltage control, and the power vacancy of the photovoltaic direct current microgrid is compensated through charging and discharging; when the direct current of the photovoltaic direct current microgrid is fluctuated (|[Delta]Udc|>=0.02pu), the storage battery side is switched from the constant direct current voltage control to a direct current voltage-active power droop control and controls the operation of the microgrid. When the load is too large to lead to the SOC of the storage battery is not larger than 40% or IB>=IBmax, a convertor station L-VSC at the load side is switched from the constant power control to the active power-direct current voltage droop control, and the direct current voltage is prevented from dropping through changing the load characteristics. When the load too small to lead to the SOC of the storage battery is not less than 80%, a photovoltaic power generation system is switched from a maximum power tracking mode to a droop control mode to ensure the balance of the system power, avoid surplus direct current network power and enhance the bearing capability of the system for the active disturbance.

Description

The net source coordinating power control method of the micro-electrical network of a kind of isolated photovoltaic DC

Technical field

The present invention relates to a kind of net source coordinating power control method, especially a kind of isolated micro-electrical network of photovoltaic DCNet source coordinating power control method, belong to power control technology.

Background technology

Under the dual-pressure of environmental pollution and energy crisis, solar energy generation technology has become power electronicsThe study hotspot of industry. Under the promotion of Power Electronic Technique and energy storage technology, DC micro-electric net will obtain soonSpeed development. DC micro-electric net with its be convenient to control, reliability is high, loss is little etc., and advantage will become remote mountain villageMain electric power-feeding structure with following family.

The micro-electrical network of photovoltaic DC can be isolated influencing each other between each end electrical network, be conducive to system receive have betweenThe new forms of energy of having a rest property, randomness, but system is disturbed in the unbalanced situation of constant power, the multiterminal change of currentBetween standing, need to control by coordination, share the imbalance power of DC network, strengthen system operation reliability.After during from network operation, photovoltaic DC micro-electric net is disturbed, for want of power support of upper strata electrical network, so moreNeed the inner each end current conversion station of micro-electrical network to give full play of the controlled advantage of multiterminal power, and can be according to installation ratioThe power generation characteristics of heavy higher photo-voltaic power supply, further excavates the adjustable potentiality of photovoltaic generation power, and thenJointly participate in, under power adjusting, effectively improving the safe operation of DC micro-electric net at many current conversion stations and many power supplysAbility.

Summary of the invention

The technical problem to be solved in the present invention is to provide the net source coordinating power of the micro-electrical network of a kind of isolated photovoltaic DCControl method.

The present invention adopts following technical proposals:

A net source coordinating power control method for the micro-electrical network of isolated photovoltaic DC, comprises the following steps:

When exchanging the major network micro-electrical network of described photovoltaic DC that makes out of service when from net pattern, battery adoptsConstant DC voltage control, by discharging and recharging the power shortage of the micro-electrical network of the described photovoltaic DC of compensation; When described lightThe DC voltage fluctuation of volt DC micro-electric net | Δ U_dc| when >=0.02pu, described battery is switched under DC voltageHang down and control, control the operation of the micro-electrical network of photovoltaic DC, its droop characteristic U_{dc_B}-I_{dc_B}For

$U_{dc\_B}=U_{dc\_B}^{*}-k_B{I}_{dc\_B}---\left(1\right)$

Wherein: k_BFor the sagging coefficient that battery side DC/DC current conversion station adopts, k_B＝0.02/I_{dc_max}，I_{dc_max}For the maximum of dc bus side curent change, U^* _{dc_B}And U_{dc_B}Be respectively the reference of dc bus side voltageValue and actual value, I_{dc_B}For dc bus side current value.

The net source coordinating power control method of the described micro-electrical network of isolated photovoltaic DC also comprises load-side current conversion stationL-VSC power control mode switch step:

As SOC≤40% or the I of battery_B≥I_{B_max}Time, I_BAnd I_{B_max}Represent respectively accumulator cell charging and dischargingThe actual value of electric current and maximum, load-side current conversion station L-VSC by determine power control be switched to active power-The droop control of DC voltage, its droop characteristic P_{dc_L}-U_{dc_L}For:

$P_{dc\_L}=P_{dc\_L}^{*}-k_L\·(U_{dc\_L}-U_{dc\_L}^{*})---\left(2\right)$

Wherein, k_LFor the sagging coefficient of load-side current conversion station L-VSC, U^* _{dc_L}For load end DC voltage U_{dc_L}Reference value. P^* _{dc_L}For load end active-power P_{dc_L}Reference value;

The sagging coefficient k of described load-side current conversion station L-VSC_LFor:

k_L＝0.05/P_{L_max}(3)

Wherein, P_{L_max}For the peak power regulated quantity of load-side.

The net source coordinating power control method of the described micro-electrical network of isolated photovoltaic DC, also comprises photovoltaic generation systemThe power control mode switch step of system:

When SOC >=80% of battery, described photovoltaic generating system is just switched to by maximal power tracing patternDroop control pattern, its droop characteristic P_{dc_PV}-U_{dc_PV}For:

$P_{dc\_PV}=P_{dc\_PV}^{*}-k_{PV}\·(U_{dc\_PV}-U_{dc\_PV}^{*})---\left(4\right)$

Wherein, k_PVFor the sagging coefficient of described photovoltaic generating system, U^* _{dc_PV}For photovoltaic end DC voltageU_{dc_PV}Reference value. P^* _{dc_PV}For load end active-power P_{dc_PV}Reference value;

The sagging coefficient k of described photovoltaic generating system_PVFor:

k_PV＝0.1/P_{PV_max}(5)

Wherein, P_{PV_max}For the peak power regulated quantity of photovoltaic end.

The beneficial effect that adopts technique scheme to produce is:

1, the present invention, in the time of the micro-electrical network emergent power disturbance from off the net, coordinates MTDC transmission system and is ensureing respectivelyWhen the end electrical network quality of power supply, jointly participate in power adjusting. Many by utilizing in each end current transformer and systemThe adjusting potentiality of power supply, realize net source and coordinate to control, and ensure to greatest extent the power of microgrid inside under each operating modeStablizing of balance and DC bus-bar voltage, the ability to bear of enhancing system to meritorious disturbance.

2, the present invention is according to DC voltage fluctuation, by energy storage device release energy, load side current conversion station changesThe droop control of power demand and photovoltaic system, makes system without communicating by letter with current conversion station, for direct current network providesMeritorious support, has increased the ability that system is born imbalance power fast, has improved system run all right.

3, the present invention takes into full account the margin of power of each end current conversion station and the safe life of each power supply, adopts direct currentThe size that should detect self SOC and electric current when voltage droop control ensures micro-electric power netting safe running, prevents from holdingBattery excessively discharges and recharges, and extends its service life, also by starting the association of load side current conversion station and photo-voltaic power supplyRegulation and control system, utilizes to greatest extent photovoltaic generation power, and guarantees the power-balance of DC micro-electric net.

Brief description of the drawings

Fig. 1 is flow chart of the present invention;

Fig. 2 is battery side constant DC voltage control flow chart of the present invention;

Fig. 3 is battery side DC voltage droop control flow chart of the present invention;

Fig. 4 is that load side of the present invention is determined active power control flow chart;

Fig. 5 is load side active power-DC voltage droop control flow chart of the present invention;

Fig. 6 is the maximal power tracing control flow chart of photovoltaic system of the present invention;

Fig. 7 is active power-DC voltage droop control flow chart of photovoltaic system of the present invention.

Detailed description of the invention

Below in conjunction with the drawings and specific embodiments, the present invention is further detailed explanation.

Embodiment 1:

As shown in Figure 1-Figure 3, the net source coordinating power control method of the micro-electrical network of a kind of isolated photovoltaic DC, bagDraw together following steps:

When exchanging the major network micro-electrical network of described photovoltaic DC that makes out of service when from net pattern, battery adoptsConstant DC voltage control, by discharging and recharging the power shortage of the micro-electrical network of the described photovoltaic DC of compensation; When described lightThe DC voltage fluctuation of volt DC micro-electric net | Δ U_dc| when >=0.02pu, described battery is switched under DC voltageHang down and control, control the operation of the micro-electrical network of photovoltaic DC, its droop characteristic U_{dc_B}-I_{dc_B}For

$U_{dc\_B}=U_{dc\_B}^{*}-k_B{I}_{dc\_B}---\left(1\right)$

Wherein: k_BFor the sagging coefficient that battery side DC/DC current conversion station adopts, k_B＝0.02/I_{dc_max}，I_{dc_max}For the maximum of dc bus side curent change, U^* _{dc_B}And U_{dc_B}Be respectively the reference of dc bus side voltageValue and actual value, I_{dc_B}For dc bus side current value.

In the time that photovoltaic micro-grid system major network is out of service, now grid-connected transverter loses the control to DC voltageMake and use. When the DC voltage fluctuation of the micro-electrical network of described photovoltaic DC | Δ U_dc| when >=0.02pu, battery just byFree charge and discharge mode is switched to voltage droop control, and as shown in Figure 1, stable DC voltage, maintains microgridInterior power-balance.

Embodiment 2:

As shown in Fig. 1 and Fig. 4-Fig. 5, the difference of the present embodiment and embodiment 1, is described isolated lightThe net source coordinating power control method of volt DC micro-electric net also comprises the control of load-side current conversion station L-VSC powerPattern switch step:

As SOC≤40% or the I of battery_B≥I_{B_max}Time, I_BAnd I_{B_max}Represent respectively accumulator cell charging and dischargingThe actual value of electric current and maximum, load-side current conversion station L-VSC by determine power control be switched to active power-The droop control of DC voltage, its droop characteristic P_{dc_L}-U_{dc_L}For:

$P_{dc\_L}=P_{dc\_L}^{*}-k_L\·(U_{dc\_L}-U_{dc\_L}^{*})---\left(2\right)$

Wherein, k_LFor the sagging coefficient of load-side current conversion station L-VSC, U^* _{dc_L}For load end DC voltage U_{dc_L}Reference value. P^* _{dc_L}For load end active-power P_{dc_L}Reference value;

The sagging coefficient k of described load-side current conversion station L-VSC_LFor:

k_L＝0.05/P_{L_max}(3)

Wherein, P_{L_max}For the peak power regulated quantity of load-side.

In the time that system operates in from net pattern, battery control DC voltage, if battery discharging provides powerBe not enough to make up the difference between photovoltaic and bearing power, will make the DC/DC transverter of battery fullWith, Shu goes out electricity Liu Clamp-on position at I_{B_max}. Meanwhile, consider the unsuitable over-discharge in service life of battery, because ofThis, as SOC≤40% or the I of battery_B≥I_{B_max}Time, need load-side current conversion station L-VSC by determining meritRate control is switched to the droop control of active power-DC voltage, change of load demand, and by fast cutback,Avoid DC voltage to fall.

Embodiment 3:

As shown in Fig. 1 and Fig. 6-Fig. 7, the difference of the present embodiment and embodiment 2 is, described isolated lightLie prostrate the net source coordinating power control method of DC micro-electric net, also comprise the power control mode of photovoltaic generating systemSwitch step:

When SOC >=80% of battery, described photovoltaic generating system is just switched to by maximal power tracing patternDroop control pattern, its droop characteristic P_{dc_PV}-U_{dc_PV}For:

$P_{dc\_PV}=P_{dc\_PV}^{*}-k_{PV}\·(U_{dc\_PV}-U_{dc\_PV}^{*})---\left(4\right)$

Wherein, k_PVFor the sagging coefficient of described photovoltaic generating system, U^* _{dc_PV}For photovoltaic end DC voltageU_{dc_PV}Reference value. P^* _{dc_PV}For load end active-power P_{dc_PV}Reference value;

The sagging coefficient k of described photovoltaic generating system_PVFor:

k_PV＝0.1/P_{PV_max}(5)

Wherein, P_{PV_max}For the peak power regulated quantity of photovoltaic end.

In the time that system operates in from net pattern, battery control DC voltage, L-VSC active power-Under the droop control of DC voltage, electrical network internal power is still serious superfluous, causes DC voltage to raise, and needsAdjust photovoltaic system generated energy, reduce photovoltaic transmission power. But too small when load, cause bearing power to be less thanWhen power that photovoltaic generating system sends, charge in batteries just moves back after battery SOC reaches 80%Go out operation, the power that now photovoltaic system sends is greater than bearing power, and DC voltage constantly raises, Wu FabaoCard DC voltage stability. Therefore, need photovoltaic generating system to be switched to and to fall power by maximal power tracing patternOperational mode, ensures direct current micro-grid system internal power balance, maintains DC voltage stability. Photovoltaic end is according to straightThe variation of stream voltage, by DC voltage/active power droop control, adjusts the active power that photovoltaic end sends.

Claims (3)

1. a net source coordinating power control method for the micro-electrical network of isolated photovoltaic DC, is characterized in that: compriseFollowing steps:

When exchanging the major network micro-electrical network of described photovoltaic DC that makes out of service when from net pattern, battery adoptsConstant DC voltage control, by discharging and recharging the power shortage of the micro-electrical network of the described photovoltaic DC of compensation; When described lightThe DC voltage fluctuation of volt DC micro-electric net | Δ U_dc| when >=0.02pu, described battery is switched under DC voltageHang down and control, control the operation of the micro-electrical network of photovoltaic DC, its droop characteristic U_{dc_B}-I_{dc_B}For

$U_{dc\_B}=U_{dc\_B}^{*}-k_B{I}_{dc\_B}---\left(1\right)$

Wherein: k_BFor the sagging coefficient that battery side DC/DC current conversion station adopts, k_B＝0.02/I_{dc_max}，I_{dc_max}For the maximum of dc bus side curent change, U^* _{dc_B}And U_{dc_B}Be respectively the reference of dc bus side voltageValue and actual value, I_{dc_B}For dc bus side current value.

2. the net source coordinating power control method of the micro-electrical network of isolated photovoltaic DC according to claim 1,It is characterized in that: also comprise load-side current conversion station L-VSC power control mode switch step:

As SOC≤40% or the I of battery_B≥I_{B_max}Time, I_BAnd I_{B_max}Represent respectively accumulator cell charging and dischargingThe actual value of electric current and maximum, load-side current conversion station L-VSC by determine power control be switched to active power-The droop control of DC voltage, its droop characteristic P_{dc_L}-U_{dc_L}For:

$P_{dc\_L}=P_{dc\_L}^{*}-k_L\·(U_{dc\_L}-U_{dc\_L}^{*})---\left(2\right)$

Wherein, k_LFor the sagging coefficient of load-side current conversion station L-VSC, U^* _{dc_L}For load end DC voltage U_{dc_L}Reference value. P^* _{dc_L}For load end active-power P_{dc_L}Reference value;

The sagging coefficient k of described load-side current conversion station L-VSC_LFor:

k_L＝0.05/P_{L_max}(3)

Wherein, P_{L_max}For the peak power regulated quantity of load-side.

3. the net source coordinating power control method of the micro-electrical network of isolated photovoltaic DC according to claim 2,It is characterized in that: the power control mode switch step that also comprises photovoltaic generating system:

When SOC >=80% of battery, described photovoltaic generating system is just switched to by maximal power tracing patternDroop control pattern, its droop characteristic P_{dc_PV}-U_{dc_PV}For:

$P_{dc\_PV}=P_{dc\_PV}^{*}-k_{PV}\·(U_{dc\_PV}-U_{dc\_PV}^{*})---\left(4\right)$

Wherein, k_PVFor the sagging coefficient of described photovoltaic generating system, U^* _{dc_PV}For photovoltaic end DC voltage U_{dc_PV}Reference value. P^* _{dc_PV}For load end active-power P_{dc_PV}Reference value;

The sagging coefficient k of described photovoltaic generating system_PVFor:

k_PV＝0.1/P_{PV_max}(5)

Wherein, P_{PV_max}For the peak power regulated quantity of photovoltaic end.