CN105207270A - Method for coordinating and controlling power of inverter capable of improving out-of-limit of photovoltaic grid connected voltage - Google Patents

Abstract

The invention discloses a method for coordinating and controlling power of an inverter capable of improving out-of-limit of photovoltaic grid connected voltage and relates to the technical field of devices or methods of adjusting electrical variable. The method comprises the following steps: (1) the voltage US at a grid connected point during the operation of a photovoltaic grid connected voltage inverter is detected in real time, wherein the voltage upper limit Umax of the photovoltaic grid connected point is a known quantity; (2) if US is equal to or smaller than Umax, the inverter sends active power PPV in an MPPT control mode; (3) if US is greater than Umax, the inverter starts the power coordination control mode to maintain the voltage of the grid connected point at the voltage upper limit Umax. With adoption of the method, the voltage outputted by the photovoltaic inverter is enabled to respond to the voltage change of the grid connected point in real time, the active power and the reactive power of the photovoltaic inverter are dynamically distributed, the voltage of the photovoltaic grid connected point is enabled to maintain at the voltage upper limit or the voltage lower limit, the quit operating times of the inverter are reduced, and photovoltaic power generation is enabled to have the remarkable and flexible voltage regulating capacity.

Description

Improve the inverter power control method for coordinating of grid-connected voltage out-of-limit

Technical field

The present invention relates to the device or method and technology field that regulate electric variable, particularly relate to a kind of inverter Reactive-power control control method preventing grid-connected voltage out-of-limit.

Background technology

Along with becoming increasingly conspicuous of problem of energy crisis, regenerative resource is more subject to the favor of people, and especially clean, pollution-free, resource distribution is wide, exploit solar energy easily.Photovoltaic generation increases rapidly in the world as a kind of form of efficiency utilization solar energy.Grid-connected can also can be grid-connected after step-up transformer at low-pressure side direct grid-connected.Photo-voltaic power supply makes original single supply radial structure become many power supply architectures after being incorporated to power distribution network, change original direction of tide and size, and along with the raising of photovoltaic permeability, the grid-connected impact on distribution network voltage is increasing.The out-of-limit problem of grid-connected point voltage is caused after needing solution grid-connected.The existing technical way improving distribution network voltage out-of-limit has: transformer on-load voltage regulating, Capacitor banks compensate, active filter (APF) compensates, static reacance generator (SVG) compensates, these technological means need to increase hardware and drop into, and are not suitable for the power distribution network of all access photovoltaics.

Summary of the invention

Technical problem to be solved by this invention is to provide a kind of inverter Reactive-power control control method preventing grid-connected voltage out-of-limit, the grid-connected point voltage change of the voltage real-time response that described method can make photovoltaic DC-to-AC converter export, the active power of dynamic assignment photovoltaic DC-to-AC converter and reactive power, ensure that grid-connected point voltage maintains its upper limit or following all the time, reduce inverter number of times out of service, make that photovoltaic generation possesses significantly, pressure regulation ability flexibly.

For solving the problems of the technologies described above, the technical solution used in the present invention is: a kind of inverter power control method for coordinating improving grid-connected voltage out-of-limit, is characterized in that described method comprises the steps:

1) photovoltaic combining inverter detects and the voltage U at site place in running in real time _s, the upper voltage limit U at grid-connected some place _maxfor known quantity;

2) if U _s≤ U _maxtime, inverter sends active-power P with MPPT control model _pV;

3) if U _s> U _maxtime, inverter startup power coordination control model, makes grid-connected point voltage maintain upper voltage limit U _maxplace.

Further technical scheme is: power coordination control model specifically comprises the steps:

If U _s> U _maxtime, inverter startup power coordination control model, and the active-power P recording that current inverter sends _pV, now inverter send reactive power Q ' _pVfor

$Q_{PV}^{\′}=-\sqrt{S_{PV}^2-P_{PV}^2}---\left(1\right)$

The active-power P that inverter is sent _pVthe reactive power Q that the inverter calculated with formula (1) sends ' _pV, reactive power reference input value meritorious as inverter subsequent time, carries out PQ control to inverter;

Detect subsequent time grid-connected inverters point voltage U _sif be no more than the upper voltage limit U at grid-connected some place _max, then inverter keeps present mode to run, in the process, if the active-power P that current inverter sends _pVcontinue to increase, then according to formula (1) reduce the reactive power Q that sends ' _pV;

If grid-connected point voltage U _sstill the upper voltage limit U at grid-connected some place is exceeded _max, now reduce the active-power P that inverter sends _pV, simultaneously according to formula (1) increase the reactive power Q that sends ' _pV;

As Q ' _pVno longer for time negative, when namely needing inverter really to send reactive power, if now grid-connected point voltage gets over the upper limit, then only reduce the active-power P sent _pV, make grid-connected point voltage maintain upper voltage limit U _maxplace.

Further technical scheme is: the reactive power that inverter can utilize is

$Q_{PV}=\sqrt{S_{PV}^2-P_{PV}^2}---\left(2\right)$

Work as Q _pVduring > 0, inverter sends reactive power, and now grid-connected point voltage will raise more, and therefore absorbing reactive power answered by inverter, namely sends negative reactive power

$Q_{PV}^{\′}=-\sqrt{S_{PV}^2-P_{PV}^2}---\left(3\right)$

By current P _pVwith the Q ' that formula (3) calculates _pV, reactive power reference input value meritorious as inverter subsequent time, carries out PQ control to inverter.

Further technical scheme is: inverter active power reduction Δ P _pVdefining method as follows:

The active-power P that inverter sends _pV, reactive power Q _pVactive-power P is consumed with load _l, reactive power Q _lmeet following relation

$U_O=U_S+\frac{(P_L-P_{PV})R+(Q_L-Q_{PV})X}{U_S}---\left(4\right)$

In formula (4): R is the line resistance connecting photo-voltaic power supply, X is the line reactance connecting photo-voltaic power supply, U _ofor distribution network voltage;

Can be obtained by formula (4):

(U _O-U _S)U _S＝(P _L-P _PV)R+(Q _L-Q _PV)X(5)

When after starting power cooperation control pattern, if grid-connected point voltage U _sstill get over the upper limit, then send active-power P at inverter _pVunder, drop to upper voltage limit U for making grid-connected point voltage _max, the active-power P that inverter should send ' _pVmeet

(U _O-U _max)U _max＝(P _L-P′ _PV)R+(Q _L-Q _PV)X(6)

Simultaneous formula (5) and formula (6) can obtain the active power reduction Δ P of inverter _pVfor

${\mathrm{\ΔP}}_{PV}=-(P_{PV}-P_{PV}^{\′})=-\frac{(U_S-U_O)U_S-(U_{max}-U_O)U_{max}}{R}---\left(7\right)$

The active-power P that inverter should send ' _pVfor

P′ _PV＝P _PV+ΔP _PV(8)

The beneficial effect adopting technique scheme to produce is: the reactive power that described method only need regulate photovoltaic combining inverter to input and active power value, effectively can solve grid-connected some place voltage out-of-limit problem, also site place voltage is made to maintain the upper limit or following of grid-connected point voltage all the time, without the need to extra hardware, cost is low, control principle is simple, effectively can reduce inverter number of times out of service, make that photovoltaic generation possesses significantly, pressure regulation ability flexibly, thus improve grid-connected performance, make effectively run between photovoltaic generation and power distribution network.

Accompanying drawing explanation

Fig. 1 is a kind of single grid-connected access distribution network system structure chart;

Wherein: 1, photovoltaic module 2, inverter 3, power distribution network.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only a part of embodiment of the present invention, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Set forth a lot of detail in the following description so that fully understand the present invention, but the present invention can also adopt other to be different from alternate manner described here to implement, those skilled in the art can when without prejudice to doing similar popularization when intension of the present invention, therefore the present invention is by the restriction of following public specific embodiment.

The invention discloses a kind of inverter power control method for coordinating improving grid-connected voltage out-of-limit, the reactive power that described method only need regulate photovoltaic combining inverter to input and active power value, effectively can solve grid-connected some place voltage out-of-limit problem, also site place voltage is made to maintain the upper limit or following of grid-connected point voltage all the time, without the need to extra hardware, cost is low, control principle is simple, effectively can reduce inverter number of times out of service, photovoltaic generation is made to possess significantly, pressure regulation ability flexibly, thus improve grid-connected performance, make effectively run between photovoltaic generation and power distribution network.

Starting inverter carries out grid-connected, at the invertor operation initial stage, runs, namely only send active-power P with MPPT control model _pV.Inverter detects grid-connected point voltage U in real time _s, and record the current active-power P sent _pVand reactive power Q _pV(when not sending reactive power, Q _pVbe 0).Distribution network voltage U _o, connect the line reactance X of photo-voltaic power supply and the upper voltage limit U at grid-connected some place _maxfor known quantity.

(1) if U _s≤ U _maxtime, inverter sends active power with MPPT control model.

(2) if U _s> U _maxtime, inverter startup power coordination control model, and the active-power P recording that current inverter sends _pV.Under normal circumstances, P _pV< S _pV, therefore the reactive power that inverter can utilize can be obtained be

$Q_{PV}=\sqrt{S_{PV}^2-P_{PV}^2}---\left(1\right)$

Work as Q _pVduring > 0, inverter sends reactive power, and now grid-connected point voltage will raise more, and therefore absorbing reactive power answered by inverter, namely sends negative reactive power.

$Q_{PV}^{\&prime;}=-\sqrt{S_{PV}^2-P_{PV}^2}---\left(2\right)$

By current P _pVwith the Q ' that formula (1) calculates _pV, reactive power reference input value meritorious as inverter subsequent time, carries out PQ control to inverter.

Detect subsequent time grid-connected inverters point voltage, if be no more than upper voltage limit, then inverter keeps present mode to run.In the process, if active-power P _pVcontinue to increase, then reduce the reactive power sent according to formula (1).

If grid-connected point voltage gets over the upper limit, now reduce the active-power P sent _pV, increase according to formula (1) reactive power sent simultaneously.

As Q ' _pVno longer for time negative, when namely needing inverter to send reactive power, if now grid-connected point voltage gets over the upper limit, then only reduce the active-power P sent _pV.

Active-power P _pVreduction Δ P _pVdetermined by following:

Inverter sends active-power P _pV, reactive power Q _pVactive-power P is consumed with load _l, reactive power Q _lmeet following relation

$U_O=U_S+\frac{(P_L-P_{PV})R+(Q_L-Q_{PV})X}{U_S}---\left(3\right)$

Can be obtained by formula (3)

(U _O-U _S)U _S＝(P _L-P _PV)R+(Q _L-Q _PV)X(4)

When after starting power cooperation control pattern, if grid-connected point voltage still gets over the upper limit, then send active-power P at inverter _pVunder, drop to upper voltage limit U for making grid-connected point voltage _max, the active-power P that inverter should send ' _pVmeet

(U _O-U _max)U _max＝(P _L-P′ _PV)R+(Q _L-Q _PV)X(5)

The active power reduction that simultaneous formula (4) and formula (5) can obtain inverter is

${\mathrm{\&Delta;P}}_{PV}=-(P_{PV}-P_{PV}^{\&prime;})=-\frac{\left(U_S-U_O\right)U_S-\left(U_{\max }-U_O\right)U_{\max }}{R}---\left(6\right)$

The active-power P that inverter should send ' _pVfor

P′ _PV＝P _PV+ΔP _PV(7)

Wherein, U _ofor distribution network voltage, U _sfor grid-connected point voltage, R be connect the line resistance of photo-voltaic power supply, X is the line reactance, the S that connect photo-voltaic power supply _pVfor photovoltaic is to power distribution network injection capacity, P _pVfor active power, Q that photovoltaic sends to power distribution network _pVfor reactive power, P that photovoltaic sends to power distribution network _lfor the active power that load consumes, Q _lfor the reactive power that load consumes.

Claims (4)

1. improve an inverter power control method for coordinating for grid-connected voltage out-of-limit, it is characterized in that described method comprises the steps:

1) photovoltaic combining inverter detects and the voltage U at site place in running in real time _s, the upper voltage limit U at grid-connected some place _maxfor known quantity;

2) if U _s≤ U _maxtime, inverter sends active-power P with MPPT control model _pV;

3) if U _s> U _maxtime, inverter startup power coordination control model, makes grid-connected point voltage maintain upper voltage limit U _maxplace.

2. the inverter power control method for coordinating improving grid-connected voltage out-of-limit as claimed in claim 1, is characterized in that power coordination control model specifically comprises the steps:

If U _s> U _maxtime, inverter startup power coordination control model, and the active-power P recording that current inverter sends _pV, now inverter send reactive power Q ' _pVfor

The active-power P that inverter is sent _pVthe reactive power Q that the inverter calculated with formula (1) sends ' _pV, reactive power reference input value meritorious as inverter subsequent time, carries out PQ control to inverter;

Detect subsequent time grid-connected inverters point voltage U _sif be no more than the upper voltage limit U at grid-connected some place _max, then inverter keeps present mode to run, in the process, if the active-power P that current inverter sends _pVcontinue to increase, then according to formula (1) reduce the reactive power Q that sends ' _pV;

If grid-connected point voltage U _sstill the upper voltage limit U at grid-connected some place is surmounted _max, now reduce the active-power P that inverter sends _pV, simultaneously according to formula (1) increase the reactive power Q that sends ' _pV;

As Q ' _pVno longer for time negative, when namely needing inverter really to send reactive power, if now grid-connected point voltage gets over the upper limit, then only reduce the active power sent, make grid-connected point voltage maintain upper voltage limit U _maxplace.

3. the inverter power control method for coordinating improving grid-connected voltage out-of-limit as claimed in claim 2, is characterized in that: the reactive power that inverter can utilize is

Work as Q _pVduring > 0, inverter sends reactive power, and now grid-connected point voltage will raise more, and therefore absorbing reactive power answered by inverter, namely sends negative reactive power

By current P _pVwith the Q ' that formula (3) calculates _pV, reactive power reference input value meritorious as inverter subsequent time, carries out PQ control to inverter.

4. the inverter power control method for coordinating improving grid-connected voltage out-of-limit as claimed in claim 2, is characterized in that inverter active power reduction Δ P _pVdefining method as follows:

The active-power P that inverter sends _pV, reactive power Q _pVactive-power P is consumed with load _l, reactive power Q _lmeet following relation

In formula (4): R is the line resistance connecting photo-voltaic power supply, X is the line reactance connecting photo-voltaic power supply, U _ofor distribution network voltage;

Can be obtained by formula (4):

(U _O-U _S)U _S＝(P _L-P _PV)R+(Q _L-Q _PV)X(5)

When after starting power cooperation control pattern, if grid-connected point voltage U _sstill get over the upper limit, then send active-power P at inverter _pVunder, drop to upper voltage limit U for making grid-connected point voltage _max, the active-power P that inverter should send ' _pVmeet

(U _O-U _max)U _max＝(P _L-P′ _PV)R+(Q _L-Q _PV)X(6)

Simultaneous formula (5) and formula (6) can obtain the active power reduction Δ P of inverter _pVfor

The active-power P that inverter should send ' _pVfor

P′ _PV＝P _PV+ΔP _PV(8)。