Solar ener­gy is devel­op­ing at a rapid pace and not with­out rea­son is con­sid­ered by many as the ener­gy of the future. We con­tin­ue to acquaint read­ers with the basic prin­ci­ples of oper­a­tion of sys­tems that gen­er­ate elec­tric­i­ty from solar ener­gy.

One of the main ele­ments of such sys­tems is the bat­tery. But oth­er devices are no less impor­tant — pow­er con­trollers and invert­ers. In this arti­cle, we will dis­cuss the fea­tures of pow­er con­trollers and invert­ers used in solar ener­gy.

  • Invert­er design

  • The main char­ac­ter­is­tics of the invert­er

  • Fea­tures of solar invert­er

  • Why you need a pow­er con­troller

  • Track­ing the max­i­mum pow­er of the solar pan­el

  • Ener­gy of the future

Why do we need these devices? The fact is that the cur­rent gen­er­at­ed by pho­to­volta­ic cells is con­stant, and most house­hold elec­tri­cal appli­ances are pow­ered by alter­nat­ing cur­rent. The task of con­vert­ing direct to alter­nat­ing cur­rent is solved by the invert­er. And the pow­er con­troller allows you to ensure that the per­for­mance of the pho­to­cells is close to max­i­mum.

Invert­er design

The invert­er, along with the bat­tery, is a “manda­to­ry” ele­ment of solar ener­gy sys­tems. Invert­ers are used to con­vert DC to AC.

Inverter with LCD indicator SibKontakt IS1-24-2000

Invert­er with LCD indi­ca­tor SibKon­takt IS1-24–2000

The main com­po­nents of invert­ers are switch­ing or switch­ing ele­ments. Depend­ing on their con­di­tion, direct cur­rent from a source, for exam­ple, from a solar pan­el, goes to the load (con­sumer) either through one or the oth­er cir­cuit. The switch­ing ele­ments are con­stant­ly switch­ing, alter­nat­ing the direc­tion of the cur­rent in each switch­ing sequence.

Popular Models

Invert­er SibKon­takt 24V/3000W

Cur­rent con­vert­ers: all mod­els

Semi­con­duc­tor switch­es (main­ly tran­sis­tors) are com­mon­ly used as the switch­ing ele­ment. In prac­tice, MOS­FETs (MOS­FETs) are wide­ly used in invert­ers with out­put pow­er up to 5 kW. High­er pow­er sys­tems typ­i­cal­ly use insu­lat­ed gate bipo­lar tran­sis­tors (IGBTs). IGBT tran­sis­tors are rapid­ly replac­ing the once pop­u­lar thyris­tors from high-volt­age fre­quen­cy con­ver­sion cir­cuits and make it pos­si­ble to cre­ate pulsed sec­ondary pow­er sup­plies with qual­i­ta­tive­ly bet­ter char­ac­ter­is­tics.

Schematic diagrams of single-phase and three-phase inverter

Schemat­ic dia­gram of a sin­gle-phase invert­er (left) and a three-phase invert­er (right)

The sim­plest invert­er gen­er­ates square wave alter­nat­ing cur­rent. The prin­ci­ple of oper­a­tion of such an invert­er is shown below (cre­at­ing a square wave AC sig­nal, the direc­tion of cur­rent flow is marked in red).

This invert­er can be used to sup­ply cur­rent to sim­ple devices such as coil heaters, but is not suit­able for most more com­plex house­hold appli­ances because it caus­es sig­nif­i­cant har­mon­ic dis­tor­tion. More com­plex types of invert­ers oper­ate on a sim­i­lar prin­ci­ple, but give the con­sumer a sig­nal with a shape close to the clas­si­cal sinu­soidal.

There are many invert­er designs on the mar­ket today that are capa­ble of deliv­er­ing AC from sim­ple square waves to near-per­fect sine waves. “Advanced” invert­ers in the con­ver­sion process use many stages of switch­ing to cre­ate as smooth a wave as pos­si­ble, and the fil­ters installed in them allow you to get a reg­u­lar sine wave.

Inverter Sequence for Creating a Square Wave

Invert­er Sequence for Cre­at­ing a Square Wave

The main char­ac­ter­is­tics of the invert­er

Sin­gle-phase invert­ers are usu­al­ly installed in sys­tems with low ener­gy con­sump­tion, such as in pri­vate homes. Three-phase invert­ers are typ­i­cal­ly used in high capac­i­ty solar instal­la­tions that serve mul­ti­ple house­holds or oth­er ener­gy con­sumers. Such high pow­er solar instal­la­tions usu­al­ly have addi­tion­al trans­form­ers to increase the volt­age trans­mit­ted through the net­work.

One of the main char­ac­ter­is­tics of the invert­er is its pow­er. The pow­er of the invert­er is deter­mined by the pow­er of the pho­to­cells that gen­er­ate direct cur­rent from solar ener­gy. Oth­er impor­tant char­ac­ter­is­tics are the AC volt­age at the out­put of the invert­er and its fre­quen­cy. For a solar sys­tem to work prop­er­ly, the out­put volt­age and fre­quen­cy must always remain sta­ble, and the device itself must with­stand a lim­it­ed time over­load and high inrush or peak cur­rents.

Batteries in solar energy
Bat­ter­ies in solar ener­gy
Heat pumps for heating your home Heat pumps for heat­ing your home

Infor­ma­tion about what kind of over­load and for how long the invert­er can with­stand is entered in the device pass­port. It should be remem­bered that the input and out­put of the invert­er must be gal­van­i­cal­ly iso­lat­ed.

Anoth­er impor­tant para­me­ter of the invert­er is its effi­cien­cy. Invert­er effi­cien­cy is a mea­sure of the ener­gy loss in an invert­er when it con­verts direct cur­rent to alter­nat­ing cur­rent. It is defined as the ratio of use­ful out­put pow­er to input pow­er.

As you can see, the invert­er is capa­ble of a lot, but it is not with­out flaws. Per­haps the main one is that an ordi­nary sim­ple invert­er pumps out the ener­gy stored by the bat­tery, even if the con­sumer does not need it, sim­ply because of its design fea­tures. This reduces the over­all effi­cien­cy of the solar sys­tem. There­fore, in large sys­tems, “sleep mode” invert­ers are used, equipped with spe­cial sen­sors that pre­vent “idle” loss­es. Such a sen­sor detects whether the load needs to be ener­gized and only then acti­vates the invert­er. Oth­er­wise, the invert­er qui­et­ly “sleeps” and does not steal ener­gy from the bat­tery.

It should be not­ed that the tech­nolo­gies for the pro­duc­tion of solar sys­tems are pro­gress­ing at an unprece­dent­ed pace. And today, invert­ers are avail­able on the mar­ket that have an effi­cien­cy of 95%, and the best exam­ples can pro­vide even 98% effi­cien­cy.

Fea­tures of solar invert­er

As already not­ed, pho­to­volta­ic solar sys­tems gen­er­ate direct elec­tric cur­rent, and the invert­er con­verts it into alter­nat­ing cur­rent, which is used in most mod­ern house­hold appli­ances and sys­tems.

Mod­ern invert­ers used in solar ener­gy pro­duce a sine wave of alter­nat­ing cur­rent at the out­put and are designed for high load pow­er up to hun­dreds of kilo­watts. But this is not all — unlike sim­ple elec­tron­ic invert­ers, solar invert­ers pro­vide con­sumers with many addi­tion­al ones. For exam­ple, they allow you to mea­sure ener­gy con­sump­tion, mon­i­tor this con­sump­tion, con­fig­ure and pro­tect the solar ener­gy sys­tem.

There are sev­er­al ways to imple­ment solar sys­tems. So, solar ener­gy sys­tems can be designed as grid or off-grid (local) sys­tems. Off-grid sys­tems are designed to oper­ate inde­pen­dent­ly of the exter­nal elec­tri­cal net­work, while grid sys­tems can sup­ply the gen­er­at­ed elec­tric­i­ty to the pub­lic grid. Net­worked sys­tems, in turn, may have ener­gy stor­age sys­tems in the form of bat­ter­ies that can be used for back­up pow­er, or have no ener­gy stor­age and be pow­ered at night from the gen­er­al net­work. But invert­ers are a manda­to­ry com­po­nent in all types of solar sys­tems.

solar power system

solar pow­er sys­tem

Ener­gy in an off-grid solar sys­tem flows in dif­fer­ent direc­tions. For exam­ple, dur­ing the day­time, elec­tric­i­ty is gen­er­at­ed by solar pan­els, and cur­rent flows from them. If there is not enough sun­light, the load can be pow­ered by both pan­els and bat­ter­ies, or only by bat­ter­ies — for exam­ple, at night.

Why you need a pow­er con­troller

The pow­er con­troller is a reg­u­lat­ing device that ensures that the bat­ter­ies in the sys­tem are not over­charged or under­charged. Recall that the work “not in mode” is bad for the “health” of the bat­ter­ies and reduces their ser­vice life, as well as degrades per­for­mance.

Inverter SibKontakt SibVolt 40110 110V/4000W

Invert­er SibKon­takt Sib­Volt 40110 110V/4000W

If you install a pow­er con­troller between the solar pan­el and bat­ter­ies, this will sig­nif­i­cant­ly increase the life of the bat­ter­ies, ensur­ing opti­mal per­for­mance.

Depend­ing on the ener­gy state of the solar pan­els, the pow­er con­troller will send the elec­tric­i­ty gen­er­at­ed by them either to users, or to charge the bat­tery, or to the gen­er­al net­work. It must be remem­bered that the volt­age of the bat­ter­ies is not sta­ble and is auto­mat­i­cal­ly adjust­ed depend­ing on the type of bat­tery, its cur­rent con­di­tion and tem­per­a­ture, while the volt­age in the home net­work must be con­stant, with­out jumps. This is the prob­lem that the pow­er con­troller solves.

Anoth­er impor­tant task of the solar con­troller is to pro­vide pro­tec­tion and safe­ty. This is espe­cial­ly impor­tant for grid sys­tems where the local solar sys­tem is con­nect­ed to the pub­lic grid. In this case, the pow­er con­troller must syn­chro­nize the volt­age and fre­quen­cy gen­er­at­ed by the local sys­tem with the para­me­ters of the gen­er­al net­work. It must also ensure the sta­bil­i­ty of the local sys­tem when dis­con­nect­ed from the pub­lic net­work dur­ing fail­ures.

Popular Models

Refrig­er­a­tion con­trollers Carel ir33

Tem­per­a­ture con­trol device Aries UKT38-Sch4

Automa­tion for air cur­tains Veza

Con­trollers: all mod­els

Seri­ous secu­ri­ty issues could arise if the local solar sys­tem con­tin­ues to feed pow­er into the grid even though it is no longer in use. This can be dan­ger­ous for ser­vice per­son­nel who may acci­den­tal­ly touch a pow­er cable that they think is dead. The pow­er col­lec­tor allows you to detect such a sit­u­a­tion in time and dis­con­nect the solar sys­tem from the exter­nal net­work.

Track­ing the max­i­mum pow­er of the solar pan­el

Max­i­mum pow­er point track­ing (MPPT) is a very spe­cif­ic pow­er con­troller para­me­ter in solar sys­tems. Solar ener­gy sys­tems gen­er­ate dif­fer­ent amounts of ener­gy dur­ing the day, which depends on the inten­si­ty of the light falling on the solar cells. The MPPT method allows each time to find that state (or a point, since this state can be rep­re­sent­ed on a graph), in which the pho­to­cells pro­vide max­i­mum pow­er gen­er­a­tion. The MPPT con­troller con­stant­ly mon­i­tors the cur­rent and volt­age sup­plied by the solar pan­el, mul­ti­plies their val­ues ​​and deter­mines the cur­rent-volt­age ratio at which the pow­er of this pan­el will be max­i­mum. The proces­sor inte­grat­ed in the con­troller simul­ta­ne­ous­ly mon­i­tors the charge state of the bat­tery (fill­ing, sat­u­ra­tion, equal­iza­tion, sup­port) and, based on this, deter­mines what cur­rent should be sup­plied to the bat­tery.

Maximum power point

Max­i­mum pow­er point

The main goal of the MPPT method is to con­trol the load, depend­ing on the pow­er state of the solar pan­el, in order to pro­vide the most effi­cient pow­er trans­fer from the solar pan­els.

Ener­gy of the future

Today, there is every indi­ca­tion that our gen­er­a­tion will indeed be the last to use fos­sil fuels to gen­er­ate elec­tric­i­ty, so every­one should know the basic prin­ci­ples used in renew­able ener­gy sys­tems, because. their future. This is nec­es­sary for the cor­rect choice of solu­tions for pro­vid­ing ener­gy to your home.

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