System for balancing, by magnetic coupling, an association in series of elements for generating or storing electrical energy
View Patent ↗System for balancing an association in series of elements for generating and/or storing electrical energy has full bridge inverters (OPC 1 , OPC 2 , OPC N ), with two inverter arms connected in parallel between two end ports and with two switches (T h1 , T b1 ; T h2 , T b2 ) connected in series by a median point (P 11 , P 12 ) of the arm; a plurality of connectors for connecting the two end ports of each full bridge inverter to a respective element (CA 1 , CA 2 , CA N , PV 1 , PV 2 , PV N ) of said association in series; and a magnetic coupler (NM) formed by a magnetic core on which a plurality of windings (W 1 , W 2 , W N ) is formed, each winding connected to the median points of the arms of one of said inverters. A series of elements (CA 1 , CA 2 , CA N ) for electrochemical storage of electrical energy and a series of photovoltaic cells (PV 1 , PV 2 , PV N ) provided with such a balancing system are also disclosed.
1. A system for balancing a series association of elements for generating and/or storing electrical energy, the system being characterized in that it comprises:
a plurality of full-bridge inverters (OPC 1 , OPC 2 , OPC N ) each of which is constituted by two inverter arms connected in parallel between two end ports of the inverter, each inverter arm being constituted in turn by two switches (T h1 , T b1 ; T h2 , T b2 ) connected in series via a midpoint (P 11 , P 12 ) of the arm;
a plurality of connectors for connecting the two end ports of each full-bridge inverter to a respective element (CA 1 , CA 2 , CA N , PV 1 , PV 2 , PV N ) of said series association; and
a magnetic coupler (NM) formed by a magnetic core having a plurality of windings (W 1 , W 2 , W N ) wound thereon, each of said windings being connected to the midpoints of the arms of a respective one of said inverters.
2. A balancing system according to claim 1 , wherein a protection switch (T pi ) is connected in series with an end port of each inverter.
3. A balancing system according to claim 1 , wherein each of said elements of said series association is constituted by a parallel association of sub-elements, and wherein each protection switch (T pi 1 , T pi 2 , T pi 3 ) is connected in series between each of said sub-elements and an end port of the corresponding inverter.
4. A balancing system according to claim 1 , wherein a respective filter capacitor (C 1 , C 2 , C N ) is connected in parallel with each element of said series association, between the two end ports of the corresponding inverter.
5. A balancing system according to claim 1 , also including control means (MP) for generating control signals for controlling said inverters so as to balance said elements.
6. A balancing system according to claim 5 , also including measurement means (CC) for measuring the voltage across the terminals of each element of said series association, said control means being adapted to operate said inverters when the maximum voltage difference between two elements exceeds a first threshold, and until said difference drops below a second threshold.
7. A balancing system according to claim 6 , wherein said measurement means comprise a current sensor (CC) connected in parallel with a switch of an inverter, the control means being adapted to control each inverter in individual manner in order to store energy in magnetic form in the core of the magnetic coupler, and then to control the inverter fitted with said current sensor so as to discharge said energy in the form of an electric current directed through said sensor.
8. A balancing system according to claim 5 , wherein said control means are adapted to control a plurality of said inverters in synchronous manner, with a common duty ratio substantially equal to 0.5.
9. A balancing system according to claim 8 , wherein:
said control means are arranged to control a single one of said inverters, to form a master inverter; and
the switches of the other inverters of the system, form slave inverters which are controlled by the voltages that appear at the terminals of the respective windings as a result of the operation of said master inverter.
10. A balancing system according to claim 8 , wherein said control means are adapted to control said inverters in synchronous manner with an adjustable phase shift between the signals controlling the various inverters.
11. A balancing system according to claim 5 , wherein said control means are adapted:
to act over one half-cycle to control one or more inverters connected to one or more elements of said series association presenting a voltage greater than a reference value in such a manner as to store energy in magnetic form in the core of the magnetic coupler; and then
over a half-cycle, to control the inverter(s) connected to one or more elements of said series association presenting a lower voltage in such a manner as to discharge said magnetic energy; and
to repeat the above operations cyclically.
12. A balancing system according to claim 1 , wherein each inverter is monolithically integrated on a respective chip.
13. A balancing system according to claim 12 , wherein each of said chips also integrates close control means (CR1, CR2, CTP) for said switches, which are implemented in the form of power transistors.
14. A balancing system according to claim 12 , wherein said chips are made using CMOS technology.
15. A series association of elements (CA 1 , CA 2 , CA N ) for electrochemically storing electrical energy and including a voltage balancing system according to claim 1 .
16. A series association of photovoltaic cells (PV 1 , PV 2 , PV N ) including a balancing system according to claim 1 .