WO2018233882A1

WO2018233882A1 - Photovoltaic module, control circuit for a photovoltaic module and method for controlling a photovoltaic module

Info

Publication number: WO2018233882A1
Application number: PCT/EP2018/054159
Authority: WO
Inventors: Rainer Merz; Angelika NAUMANN; Timm CZARNECKI
Original assignee: Hochschule Karlsruhe
Priority date: 2017-06-23
Filing date: 2018-02-20
Publication date: 2018-12-27
Also published as: DE102017005966A1; EP3642955A1

Abstract

Disclosed is a photovoltaic module (10) comprising: a first module connection (12_1), a second module connection (12_2) and at least one cell line (14), at least one cell line (14) having n series-connected cell line portions (16_1..16_n); and comprising step-down converters (18_x) having two step-down converter inputs (20_x1, 20 x2) and one step-down converter switching device (24_x), the first step-down converter (18_1) having exactly one step-down converter output (22_11) connected to the first module connection (12_1) and the n-th step-down converter (18_n) having exactly one step-down converter output (22_n2) connected to the second module connection (12_2).

Description

"Photovoltaic module, control circuit for a photovoltaic module and method for

Control of a photovoltaic module "

description

The invention relates to a photovoltaic module, a control circuit for a photovoltaic module and a method for controlling a photovoltaic module. Photovoltaic modules are the main component of photovoltaic systems for converting solar radiation into electricity. In this case, photovoltaic systems usually consist of a plurality of photovoltaic strings, each having a plurality of photovoltaic modules connected in series. Photovoltaic modules in turn usually consist of a series circuit of individual solar cells, which are hermetically encapsulated, and are no longer accessible for repair. Commercially available photovoltaic modules have, for example, 60 series-connected solar cells. The series connection of the solar cells, with a voltage of only about 0.5 V, and the series connection of the photovoltaic modules add up to the voltage available at the photovoltaic system. In these photovoltaic modules, often 20 series-connected solar cells are combined into sub-cell strands and thus form three series-connected partial cell strands. The connections of the three partial cell strands are accessible in the photovoltaic module in each case for additional electrical shading. In the following, photovoltaic systems are also referred to as PV systems, photovoltaic systems as PV lines and photovoltaic modules as PV modules or modules.

The efficiency of PV modules depends significantly on their ability to respond to changing external conditions such as reduced solar radiation and Under normal operating conditions to have the lowest possible power loss. It is therefore desirable to increase the efficiency of PV modules by integrating a simple and inexpensive control circuit without having to change the standard layout of PV modules.

In conventional PV modules, each module generally has at least one freewheeling diode or bypass diode arranged in parallel therewith. Frequently, freewheeling diodes are arranged in parallel to all partial cell strings of a PV module. In the case of a fault, for example by shading or a failure of the module or a sub-cell string, the module or the Teiizellstrang can be bypassed via the freewheeling diodes and the bridged module or the bridged sub-cell strand provides no contribution to the output power. Thus, the affected PV string of a PV system can be operated even in case of failure of the module or the sub-cell strand.

In order to be able to achieve a contribution to the respective PV string power of a PV system in the case of partial shading, step-down converters are configured between the inputs of the entire PV module or between the inputs of each individual part cell string of the PV module in advanced PV modules instead of free-wheeling diodes. In the case of a configuration of buck converters between the inputs of each individual sub-cell strand of a PV module, however, the prior art has the problem that either the sub-cell strands have to be electrically separated from one another via the respective buck converters and therefore no standard PV modules are used can, or that the inputs and outputs of the buck converter must be galvanically isolated from each other. This results in each case a power reduction for the PV module, which depends on the efficiency of the buck converter.

It is therefore an object of the present invention to provide a PV module, a control circuit for a PV module, and a method of controlling a PV module, which increases the efficiency of a PV module and is also cost-optimized for a standard PV Module can be configured. This object is achieved by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims. Unless otherwise stated, in the context of the present description, the term "connection" is always understood to mean electrical connection. In the following, the connections of the buck converters, which are located on the side of the sub-cell strands or connected to the terminals of the sub-cell strands, are also referred to as buck-set inputs. Accordingly, the terminals of the buck converters, which are on the side of the PV module terminals or connected to the PV module terminals, are referred to as buck converter outputs. The terms "input" and "output" here do not refer to the operation of the buck converter, where the input voltage is greater than the output voltage, but only on their spatial arrangement.

One aspect for achieving the object relates to a PV module having a first module connection and a second module connection and at least one cell strand, wherein at least one cell strand comprises n partial cell strands connected in series with n≥ 2 and

where, for 1≤x≤n and

an x th in each case one x th

Buck converter with two buck converter inputs and a buck converter switching device is assigned,

wherein the xth buck converter is connected in parallel with the associated xth subcell string via the two buck converter inputs,

wherein the buck converter switching means of the x-th buck converter is activatable as long as a voltage dropping in the xth buck converter is less than or equal to a predetermined respective voltage limit, and

wherein the buck converter switching means of the xth buck converter is deactivatable as long as a voltage falling in the xth buck converter is greater than the predetermined respective voltage limit,

wherein the first buck converter has exactly one buck converter output connected to the first module terminal, and wherein the nth down-converter has exactly one buck converter output connected to the second module terminal.

The use of PV modules, in which the subcell cords continue to be connected in series by default, and the first and nth buck converters are only connected to one of the two module connections via their buck converter outputs, offers the advantage of optimizing the performance of the PV module to limit the optimization of the individual sub-cell strands. In this arrangement, it is possible to optimize the power of the entire PV module by supplying power from the first and n-th partial cell strings to the partial cell strings between the first and n-th partial cell strings.

For the purposes of the invention, a PV module is understood to mean that part of a solar power system or PV system in which solar radiation converts part of the solar radiation into electrical energy. The typical direct type of energy conversion from solar energy to electrical energy is called photovoltaic.

The components of the PV module are preferably mounted on a standard connection box. The connection box of the PV module can have two electrical contacts or module connections, to which an external load can be directly coupled or connected, or to which other PV modules can be connected or connected in series or in parallel to form a PV system. The two module connections are designed as anodes and cathodes and are preferably freely accessible at the connection box of the PV module for external connection. The PV module comprises at least one cell string, which is connected between the two module connections of the PV module. It is also possible a plurality of parallel cell strands between the Moduianschlüssen. At least one cell strand comprises at least two partial cell strands, but generally three or more partial cell strands, which are connected in series between the module connections. Each subcell line has an input terminal and an output terminal. Input terminal and output terminal are each connected to a node of the junction box of the PV module. In this case, the input terminal of the first sub-cell string of a cell string can be coupled to a first node and the output terminal can be coupled to a second node. The input terminal of the second subcell line may then be coupled in series with the output terminal of the first subcell line at the second node and the output terminal of the second subcell line at a third node. The input terminals of further sub-cell strings are then respectively coupled to the output terminal of the preceding sub-cell string at the associated node and the respective output terminals of the further sub-cell strings to the subsequent node. Overall, this results in n sub-cell strands for a cell strand n + 1 nodes of the connection box. The nodes of the junction box can be freely accessible for the coupling of other electrical circuits in addition to the sub-cell strands, thus circuits can also be retrofitted. However, it is not possible with standard modules to separate nodes in order to decouple partial cell strands from each other electrically. The partial cell strands usually consist of a series circuit of individual solar cells, which are hermetically encapsulated, and are no longer accessible for repair. Commercially available PV modules have, for example, a cell sträng with three Teiizelisträngen, each having 20 series-connected solar cells. By the series connection of the solar cells, each with a voltage of only about 0.5 V and the series connection of the sub-cell strands added in the example, the voltage to 30 V, which is available at the PV module.

In contrast to the conventional PV modules with free-wheeling diodes in parallel with the sub-cell strands, the PV module according to the invention has step-down converters parallel to the sub-cell strands. Each subcell line of the PV module is assigned a buck converter. Under a buck converter, also called down converter or step-down controller, the expert in electronics understands a form of switching DC-DC converter. The buck converters according to the invention each have two electrical input contacts or inputs and at least two electrical output contacts or outputs. In this case, only one electrical output contact is externally coupled in the first and nth buck converter. The electrical inputs and Outputs are each formed as anode and cathode.

An input of each buck converter, usually the input anode, is coupled to the input terminal of the respective associated sub-cell string at the node in question. The other input of each buck converter, usually the input cathode, is coupled to the output terminal of the respective associated sub-cell string at the respective node. Thus, the inputs of the buck converter are connected in parallel to the associated sub-cell string. In addition, the buck converters each have a buck converter switching device, which comprises one or more buck converter switches, wherein the buck converter switches are preferably designed as transistors. In this case, each buck converter via its buck converter switching device can be activated by a controller and deactivated by the buck converter switch the buck converter switching device depending on the operating state on and off or in other words closed and opened. Activatable means in this context that the buck converter switch the respective buck converter switching device not remain closed or open, but alternately opened and closed at short time intervals to adjust the output power of the respective buck converter to the affected cell strand. Preferably, the switching frequency of the buck converter switch in a range of 100 kHz to 1 MHz, ie a switching cycle duration between 1 microseconds and 10 microseconds. The respective buck converter, in particular the buck network switching device of the buck converter, after activation via a controllable buck converter switching device also again deactivated or is no longer activated when the buck converter switch the respective buck converter switching device remain closed or open. The activation of the respective buck converter switching device takes place in the event that the voltage within the step-down divider drops to or below a predetermined first threshold value. The drop in voltage within the buck converter is often caused by shading of the solar cells of the sub-cell strand, but can also be due to aging processes and defects in the solar cells of the sub-cell strand. By turning on and off the buck converter switch the Buck converter switching devices, the respective step-down converter starts to work, whereby its output current is increased. Usually, after the activation of the respective step-down converter during the shading case, a few hundred to several million switching cycles per second are performed on the step-down setting switches. The deactivation of the respective buck converter circuit means then takes place in the event that the voltage within the buck converter again rises above the predetermined first threshold value. The voltage within the buck converter increases again when the shading of the solar cells of the sub-cell strand is canceled.

The activation or deactivation of the respective buck converter usually takes place during the course of a day only for very few cycles, for example in each search for a maximum power point (MPP) for a cell string every 5 to 10 minutes. This results in a typical summer day with about 16 hours sunshine duration only about 200 alternations between activation and deactivation of the respective buck converter.

The number of buck converters connected to a partial cell string is 1, although multi-phase buck converters can also be used. The buck converters, which are assigned to the first sub-cell string and the n-th sub-cell string, ie the last sub-cell string in the series connection of sub-cell strings of at least one cell string, have exactly two outputs with an output anode and an output cathode. The number of outputs is therefore 2. Of the two outputs of these buck converters, in contrast to conventional PV modules, only one output is connected. The other output is not connected, or only via internal components of the Tiefse tzste Hers. Thus, this port is not externally coupled. The first step-down converter is preferably connected via its output anode to the first module connection or the module anode while the output cathode is not coupled. By contrast, the nth buck converter is preferably connected via its output cathode to the second module terminal or the module cathode while the output anode is not coupled. The output voltage between the anodes and cathodes of the outputs of the first and nth Tiefsetzsteliers is always smaller than the amount of input voltage at the buck converter.

In a preferred embodiment, for n is 3 and

and y the y-th buck converter a first buck converter output, which with the

the first module connection is connected and the y-th buck converter has a second buck converter output, which is connected to the second module terminal. In this embodiment, therefore, at least one cell string of the PV module is equipped with at least three sub-cell strands, and all buck converters that are not assigned to the first or nth sub-cell string of this cell string have at least one buck converter output, which is connected to the module anode and at least one Buck converter output connected to the module cathode. In this case, preferably at least one output anode of the respective buck converter is connected to the module anode and at least one output cathode of the respective buck converter is connected to the module cathode. The voltage between the anodes and cathodes of the outputs of the y-th buck converter is always greater than or equal to the amount of voltage between the anodes and cathodes of the inputs on the buck converter. In a further preferred embodiment, the buck converter inputs and the buck converter outputs of the xth buck converter are directly electrically connected to each other by internal circuitry within the xth buck converter. The internal circuit within the buck converter of the PV module thus has no galvanic isolation of buck converter inputs and buck converter outputs as in the buck converters of known PV modules. In the known PV modules, a galvanic isolation by a transformer in the buck converter is necessary because a performance optimization of the individual sub-strands based on the use of bidirectional DC-DC converters. The buck converters, which are assigned to the first sub-cell string and the n-th sub-cell string, have, for example, exactly one buck converter switch each for the buck converter switching device. Within the first Tiefsetzsteliers is here connected in series between the anode of the buck converter input and the anode of the buck converter output of the buck converter and an inductance or coil. In addition, a diode is connected in parallel with the associated subcell line. The diode is connected in the reverse direction, the anode of the diode at the cathode of the buck converter input and the cathode of the diode between Tiefsetzsteilerschalter and inductance is applied. In addition, the cathode of the buck converter input is usually connected directly to the cathode of the buck converter output. Within the n-th buck converter, between the cathode of the buck converter input and the cathode of the buck converter output, the buck converter shaiter and the inductor are connected in series. In addition, the anode of the diode is connected between the low-side I rsc ha I r and inductance, and the cathode of the diode is connected to the anode of the step-down converter input. In addition, the anode of the buck converter input is connected directly to the anode of the buck converter output. In addition, the first and nth step-down converters usually have a capacitance between the anode and the cathode of the step-down converter output, that is, parallel to the step-down converter outputs.

An output voltage is applied between the output anode and the output cathode at the buck converter outputs of the first and nth bucking stages of a cell string and can be measured by a voltmeter. Without shading, this output voltage is greater than the predetermined voltage limit for the respective buck converter and the Tiefsetsteilerschalter the buck converter remain disabled and permanently closed. The power loss due to the use of these two step-down converters without shading merely results from the ohmic losses at the inductances of these step-down converters. In the case of a drop in the output voltage to or below the predetermined voltage limit at these buck converters by shading the buck converter switching device of the buck converter is activated. In this case, in the case of the activated buck converter, a few hundred to several million switching cycles per second are carried out at the buck converter switch. This will transfer electrical energy from the connected voltage source to the connected load. For example, the two energy storage coil and capacitor can Allow the load to be supplied during the phases when the switch is open. The inductance of the coil keeps the higher input voltage of the load fem. The output can be adjusted by controlling the on and off times of the buck converter switch. This control is done, for example, by a regulator to keep output voltage or current at a desired value. During a turn-on time of the switch, for example, a load current flows through the coil and through the load and the diode blocks. During the switch-off phase of the switch, the energy stored in the coil is dissipated: the current through the load continues to flow, but now through the diode and out of the capacitor. The coil and the capacitor form a second order low pass in the example. The actual down conversion is achieved by filtering out the DC component from the square-wave voltage. The value of the DC component can be adjusted by the duty cycle. The affected buck converter is preferably operated in such a way that the output power of the sub-cell string is maximized and the current through the other sub-cell strings is not limited.

In the event that at least one cell strand of the PV module is equipped with at least three sub-cell strands, the buck converters which are assigned to the sub-cell strands between the first sub-cell strand and the n-th Teiizellstrang, for example, exactly two buck converter switch for the buck converter switching device, two Output anodes and two output cathodes. The number of buck converter switches is thus 2 and the number of outputs is 4. In these intermediate buckets, a first inductance is preferably arranged between the input anode and a first buck converter node. The first step-down switch is preferably coupled between the first step-down converter node and the module anode, and between the module cathode and the first step-down node, preferably a first diode is arranged in the reverse direction. In addition, a second inductance is preferably arranged between the input cathode and a second buck converter node. The second step-down switch is preferably coupled between the second buck converter node and the module cathode, and preferably between the second buck converter node and Moduianode is a second diode arranged in the reverse direction. In a further preferred embodiment, the y-th buck converter exclusively supplies the y-th subcell line with a step-down converter power unidirectionally, as long as the voltage which drops in the y-th step-down converter is less than or equal to the predetermined voltage limit value.

In the buck converters between the first and nth buck converters of a cell string, a voltage measurement is carried out in each case between the first buck converter node and the second buck network node. Without shading, this voltage is greater than the predetermined voltage limit for the respective buck converter and the buck converter switch the buck converter switching device remain disabled and permanently open. Thus, no current flows through the respective buck converter without shading, the current through the sub-cell string is identical to the module current and there is no additional power loss by using this buck converter. In the case of a drop in the voltage at or below the predetermined voltage limit to these buck converters by shading the buck converter switching device of the buck converter is activated. In this case, in the case of the activated buck converter, in each case a few hundred to several million switching cycles per second are performed on the two buck converter switching devices. As a result, electric power is unidirectionally transferred from the buck converter outputs through the buck converter to the associated subcell line.

In a further preferred embodiment, the first buck converter and the nth buck converter exclusively supply the buck converter power to the yth buck converter in a unidirectional manner. In this case, the first, the nth or both partial cell strands are in normal operation and deliver power via the associated buck converter to the buck converter of the shaded sub-cell string to increase its performance.

In a further preferred embodiment, the predetermined voltage limit of the xth buck converter has a value less than or equal to zero volts on and the x-th activated buck converter increases a partial cell strand performance of the x-th subcellular strand.

In a further preferred embodiment, the step-down converter switching device of the x-th buck converter, when activated, periodically switches in order to increase the partial cell strand power of the xth partial cell strand. In this way, the power of the shaded x-th sub-cell string can be suitably adjusted without limiting a cell-string current of the PV module. In a further preferred embodiment, the predetermined voltage limit of the xth buck converter in each case has a fixed voltage limit.

In a further preferred embodiment, the PV module comprises a buck converter control, by means of which the buck converter switching device of the xth buck converter is controlled in order to maximize a photovoltaic module power of the photovoltaic module and the buck converter control is formed with MPPT (Maximum Power Point Tracking). The MPPT can optimally adapt and maximize the output power of the xth sub-cell string during shading. In the interaction of the control of the buck converter switching devices of all buck converter with MPPT while the output power of the entire PV module is maximized.

In a further preferred embodiment, the buck converter switching devices of the first and the nth buck converter each have a buck converter switch, and the buck converter switching device of the y-th buck converter has a first and a second buck converter switch.

In a further preferred embodiment, a module current and a partial cell string current is monitored by the x-th sub-cell string and the buck converter switches of the first and n-th buck are closed and the buck-boost switches of the y-th buck are opened when the difference between the module current and the partial cell string current through the x-th partial cell strand falls below a predetermined x-th current limit for the x-th partial cell strand. The deviation between the module current and the partial cell phase current in each case represents a hysteresis, which can either be set or is predetermined by the minimum switch-off time of a transistor for the respective activated buck converter by the components. If the module current is approximately the same size as the partial cell strand current, then the partial cell strand is in normal operation without shading and activation of the buck converter is no longer necessary. In a further preferred embodiment, the predetermined current limit value for the x-th subcellular strand has a fixed current limit value or the deviation between module current and partial cell strand current is in a range of less than 1% up to a deviation of less than 10%. This may be, for example, a deviation between modulus flow and partial cell strand flow of 10%, preferably of 5% and particularly preferably of 1%.

In a further preferred embodiment, an xth capacitor is connected in parallel with the xth subcell line. In this case, the xth step-down converter usually has a capacitance between the anode and the cathode of the step-down converter input, that is to say in parallel with the step-down converter inputs. Due to the interaction of capacitors and inductors within the step-down converter, the output voltage of the respective step-down converter is made uniform, which has an advantageous effect on a trouble-free operation. In a further preferred embodiment, at least one cell strand of the PV module has three partial cell strands connected in series, and more preferably, the PV module has only one cell strand. With this configuration, the PV module can be implemented on a standard junction box for PV modules without modification. A further aspect for achieving the object relates to a control circuit having a plurality of buck converters for a PV module,

wherein the photovoltaic module has a first module connection and a second module connection Module connection and at least one cell strand,

where, for n ≥ 2 and

at least one cell strand has n partial cell strands connected in series;

where, for 1≤x≤n and an xth subcellular strand, one x-th each

wherein the first buck converter has exactly one buck converter output connected to the first module terminal, and

wherein the nth buck converter has exactly one buck converter output which is connected to the second module terminal. In a further preferred embodiment of the control circuit, the xth buck converter is designed to replace a free-wheeling diode of the xth sub-cell string of the PV module. The control circuit can thus be used as a retrofit kit for conventional PV modules with parallel freewheeling diodes to the Teilzeilsträngen. The contacts of the freewheeling diodes in a standard PV module for reconfiguration are accessible, the freewheeling diodes are removable and the control circuit can be used on the intended contacts.

A further aspect for achieving the object relates to the use of the control circuit as described above as a control circuit for a PV module. A further aspect for achieving the object relates to a method for controlling a photovoltaic module having at least one cell strand, wherein at least one Zeilstrang n series-connected partial cell strands with n≥ 3 and

where, for 1≤x≤n and an xth division line, one x-th

Buck converter is associated with a buck converter switching device,

the method comprising the steps of:

Activating the buck converter switching means of the xth buck converter as long as a voltage falling over the xth sub-cell string is less than or equal to a predetermined xth voltage threshold,

Deactivating the step-down divider circuit means of the xth step-down converter as long as the voltage dropping across the xth sub-line is greater than the predetermined x-th voltage limit, and

- Transmission of electrical power between a buck converter input and a buck converter output of the x-th buck converter by means of internal circuit via a direct electrical connection in the x-th buck converter.

Another aspect of solving the problem concerns a photovoltaic module! with a first module connection and a second module connection and at least one cell strand,

wherein at least one cell strand comprises n series connected partial cell strings (16_1..16_n) connected at n + 1 nodes and wherein the first node point at the beginning of the cell string and the η + 1th node point at the end of the cell string

Cell strand, with n ≥ 2 and

where, for 1≤x≤n-1 and

an x-th controllable half-bridge comprising two asynchronously switchable switching devices between the i-th node, with 1≤i≤x and iei, and the jth node, with x + 2≤j≤n + 1 and

of

Cell strand is connected and a half-bridge node between the two switching devices to the x + 1-th node of the cell strand is connected, wherein the first half-bridge for providing a target voltage on the associated first sub-cell strand is activated, as long as a voltage that drops in the first sub-cell strand, smaller or is equal to a predetermined respective voltage limit and the first half-bridge is deactivated, as long as a Voltage falling in the first Teilzeilstrang, greater than the predetermined respective voltage limit is, and

wherein the η-1-th half-bridge for providing a target voltage at the associated n-th sub-cell strand can be activated, as long as a voltage that drops in the n-th sub-cell strand is less than or equal to a predetermined respective voltage limit and the η-1-th half bridge can be deactivated is as long as a voltage that drops in the n-th sub-cell string is greater than the predetermined respective voltage limit. In addition to the use of PV modules, in which the series-connected partial cell strands of a cell strand are configured in parallel with buck converters, there is also the possibility to increase the efficiency of a PV module by parallel to the cell strand for n sub-cell strands n-1 half-bridges with two Switching devices are arranged, the half-bridge nodes are connected between the switching devices with the nodes between the sub-cell strands. With this arrangement, the potentials at the nodes between the sub-cell strands can be predefined with reduced power of one or more sub-cell strands, and thus also the voltages that drop at the sub-cell currents. The half bridges thus provide a balance function for the potentials between the Teiizellsträngen and it is spoken below for the arrangement of the half bridges of a balance circuit for the cell strand. By increasing the partial cell voltage, however, a reduced partial cell strand provides a lower partial cell current, which is compensated by equalizing currents across the respective half-bridge. The cell string current is thus reduced by the equalization currents and not brought directly to the desired value of the module output current as in the case of the arrangement with parallel buck converters. The conversion of the cell strand current to a desired photovoltaic string current takes place in the arrangement with half bridges in a subsequent step. The advantage of balancing the cell string results from a significant reduction of required components by eliminating the buck converter and also by a significant reduction in control effort. In the case of the arrangement of the balancing circuit, a partial cell strand capacitor and a partial cell strand voltage measuring device, which monitors the voltage at the partial cell strand, may be connected in parallel between the x th node and the x + 1 node of the cell strand for each of the n th cell strand of the cell strand natural number that is greater than or equal to 1 and less than or equal to n-1. Alternative voltage measurements, for example with a common reference node for calculating the partial cell voltages, are also possible. The voltages determined by the partial cell voltage measuring devices which drop across the partial cell strings are transmitted to a half-bridge control. A cell strand capacitor can be connected in parallel to the entire cell strand with its n series-connected partial cell strands.

Parallel to the entire cell strand or parallel to a part of the n partial cell strands, n-1 half bridges are connected. Each half bridge consists of two series-connected switching devices with a half-bridge node between the switching devices. The half-bridge node of the x-th half-bridge is connected to the x + 1-th node of the cell string. The input of the xth half-bridge is at the input of its first switching device and is connected to an ith node of the cell string, where i is again a natural number and is greater than or equal to 1 and less than or equal to x. The input of the xth half-bridge is thus connected to a node of the cell strand which is closer to the beginning of the cell strand than the node of the cell strand which is connected to the half-bridge node of the xth half bridge. The output of the xth half-bridge is at the output of its second switching device and is connected to a jth node of the cell string, where j is again a natural number and is greater than or equal to x + 2 and less than n + 1. The output of the xth half-bridge is thus connected to a node of the cell string which is closer to the end of the cell string than the node of the cell string which is connected to the half-bridge node of the xth half-bridge.

The switching devices of the half bridges each have at least one Switch on. These switches can be designed as transistors, for example. Typical switching frequencies, which are needed for the operation of the half-bridges, are here at 250 Hz to 1 MHz. Parallel to the respective switch of a switching device, a diode may be connected. The diodes are each arranged in the reverse direction and allow a regulated current flow through the switching device during the time of the switching operation. A half-bridge inductance can be arranged in each case between the half-bridge nodes of the half-bridges and the nodes between the partial cell strings. The half-bridges, in particular their respective switching devices, are each controllable via the half-bridge control.

The illumination-dependent current-voltage characteristic of each sub-cell string defines a sub-cell-string current for the sub-cell-line voltage. The cell strand voltage results from the series connection of the partial cell strands. In the event that a half-bridge is activated, a current flows through the corresponding half-bridge inductance. It follows from the node equations for the nodes between the sub-cell strands that the half-bridge inductor currents can control the sub-cell strands.

If the Teilzelispannung a sub-cell strand decreases, for example by shading below a specified voltage limit, the half-bridge control activates those half-bridges, which are arranged around the sub-cell string around. In partial cell strands at the beginning or at the end of the cell strand only one half-bridge is thus activated, while for the other partial cell strands two half-bridges are activated. The half-bridge controller controls switching devices of the half-bridges by specifying a setpoint voltage for the node between the respective sub-cell strings. The specification of the setpoint voltage is operated in the MPPT. The control is effected by periodic asynchronous switching of the respective switching devices with a pulse width modulated controlled signal with duty cycle

with the turn-on time TON of the respective switching unit with respect to the period of the half-bridge. This turns the

Set voltage at the respective node. The increased partial cell voltage causes in the shaded sub-cell strand a reduced partial cell extraneous current, but is compensated by the current through the half-bridge inductance.

In a preferred embodiment, for the xth half-bridge, the ith node of the cell strand is the first node of the cell strand and the jth node of the cell strand is the n + 1 node of the cell strand.

In this embodiment, the input of the x-th half-bridge is connected to the first node of the cell string and the output of the x-th half-bridge to the η + 1-th node of the cell string. Thus, all inputs of the n-1 half-bridges are connected to the first node of the cell string and all outputs of the n-1 half-bridges are connected to the n + 1 node of the cell string. Thus, all n-1 half-bridges can be individually and independently controlled by the half-bridge controller. When shading a partial cell strand only the activation of one or two half-bridges is necessary.

In a preferred embodiment, for the xth half-bridge, the ith node of the cell strand is the xth node of the cell strand and the jth node of the cell strand is the χ + 2nd node of the cell strand. In this embodiment, the input of the xth half-bridge to the xth node of the cell string, the half-bridge node of the xth half-bridge to the x + 1th node of the cell string, and the output of the xth half bridge to the χ + 2 -th node of the cell strand connected. The index of the three ports is incremented by one for the consecutive half-bridges. All inputs of the n-1 half-bridges are connected to a different node of the cell string and all outputs of the n-1 half-bridges are also connected to a different node of the cell string. The n-1 half-bridges are always jointly controlled by the half-bridge control. When one or more partial cell strands are shaded, equalizing currents thus flow through all half-bridge inductances of the n-1 half bridges.

In a preferred embodiment, for n ≥ 3 and 1≤k≤n / 2 and

all odd half bridges are connected in series in a first half-bridge string and all straight half-bridges are connected in series in a second half-bridge string. In the embodiment with the continuous indices of the terminals of the n-1 half-bridges, the half-bridges with the odd-numbered indices and the half-bridges with even indexes can be configured in each case to form a half-bridge line. Straight in this context means that the index of the xth half-bridge, which represents a natural number, is divisible by two. Accordingly, odd in this context means that when dividing the index of the xth half-bridge by two, a remainder of one remains.

When connecting the half-bridges to half-bridge strings, the output of the half-bridge with the lower index is connected to the input of the half-bridge with the higher index.

Since the target voltages to be provided at the respective half bridges require relatively low voltage values, the half-bridge strings can also be realized by programmable standard IC components, which in turn makes the balance circuit as a whole efficient and inexpensive.

In a preferred embodiment are for

the xth and the x + 1th half bridges can be activated to provide a setpoint voltage at the assigned x + 1st subcell line, as long as a voltage falling in the x + 1st subcell line is less than or equal to a predetermined respective voltage limit value and The x-th and the x + 1-th half-bridge can be deactivated as long as a voltage falling in the x + 1-th sub-cell string is greater than the specified respective voltage limit. The configuration of a balance circuit can be realized for cell strands with at least two partial cell strands. The number of partial cell strands of a cell strand is often at three partial strands, but is not limited thereto. Configurations with a significantly higher number of sub-cell strands, for example 10 to 100 partial cell strands are possible here. However, this also increases the control effort. With exactly two sub-cell strands for a cell strand, this results in only one half-bridge in the configuration. Both the first and the second sub-cell strand can be controlled via this half-bridge. In the case of more than two partial cell strands for a cell strand, the first and the last partial cell strands are in turn controlled by only one half bridge, all other partial cell strands are controlled by two half bridges.

In a preferred embodiment, the activatable half-bridges periodically switch their two switching devices asynchronously when activated in order to provide the setpoint voltages of the associated sub-cell strands.

Asynchronous switching of the switching means means that for the duration of time, the switch of the first switching device of the half-bridge

closed and the switch of the second switching device of the half-bridge is open and opened for the duration of time TOFFI = TON2 the switch of the first switching device of the half-bridge and the switch of the second switching device of the half-bridge is closed. If diodes are arranged in the switching device parallel to the switch, these diodes ensure that the current through the half-bridge can continue to flow, even if, during the change of state of the half-bridge from the state of the period to the state of the period TOFFI

none of the two switches for a negligible dead time Ττοτ is closed.

In a preferred embodiment, the photovoltaic module comprises a half-bridge control, by means of which the activatable half-bridges are activated and controlled, and

wherein the half-bridge control controls the target voltages of the associated sub-cell strands with maximum power point tracking, MPPT. The half-bridge control can be realized here as an independent circuit or as a programmable standard IC component. In a preferred embodiment, an x-th half-bridge inductance is connected between the half-bridge node of the x-th semiconductor bridge and the x + 1-th node of the cell string.

In a preferred embodiment, a cell string capacitor is connected between the first node and the η + 1-th node of the cell string.

In a preferred embodiment, for 2 ≦ y ≦ n-1 and y e i, a y-th sub-cell strand capacitor is connected in parallel with the y-th sub-row train. Due to the interaction of capacitors and inductors within the balancing circuit, the currents are made uniform by the half-bridge inductance of the respective half-bridge, which has an advantageous effect on trouble-free operation. In a preferred embodiment, the cell strand is connected to the first module connection and the second module connection at the first and the η-1-th node via a cell string setting converter.

In a preferred embodiment, the half-bridge controller controls the cell strand setting converter and the setpoint voltages of the associated partial cell strings with maximum power point tracking, MPPT, and supplies a desired photovoltaic string current as the output current of the cell string setting converter.

In a preferred embodiment, the cell string bottom converter comprises the following configuration:

an nth controllable half-bridge comprising two asynchronously switchable switching devices between the first node and the η + 1-th node the cell strand;

a node between the two switching devices, which is connected via a buck converter inductance to the first module terminal of the photovoltaic module;

a buck converter capacitor between the first module terminal and the second module terminal; and

- The η + 1-th node of the cell string, which is connected to the second module connection. The cell strand low converter adjusts the cell string current to the current that is specified at the module output for feeding into the photovoltaic string. The cell strand low-voltage converter consists of a half-bridge, a buck converter inductance and a buck converter capacitor. The half-bridge is arranged between the start and end nodes of the cell string parallel to the cell string and consists of two series-connected switching devices with a half-bridge node between the switching devices. The switching devices each have at least one switch. Here again, in each case a diode can be connected in parallel with the switch. The diodes are each arranged in the reverse direction. The buck converter inductance is arranged between the half-bridge node and the module connection, and the buck converter capacitor is arranged between the first module connection and the second module connection.

In order to maximize photovoltaic module performance, the half-bridge controller activates the half-bridge of the column transformer Ile rs and controls its switching devices by specifying the photovoltaic pole current in the MPPT. This is done by periodic asynchronous switching of the switching devices with a pulse width modulated controlled signal with duty cycle

with the turn-on time TONI from the first switching unit with respect to the period

the half bridge. Further MPP tracking capabilities measure the individual currents and optimize the performance of the sub-cell strands via known methods, such as the hill-climbing method or the analog based on the peak-detect circuit Method. In particular in combination with the patent DE 10 2011 1 1 1 255 B4, there are possibilities for communication-less partial cell string optimization and reliable avoidance of hot spots in PV modules and systems. A further aspect for achieving the object relates to a control circuit having a plurality of controllable half-bridges for a photovoltaic module,

wherein the photovoltaic module has a first module connection and a second module connection and at least one cell strand,

wherein, for n≥ 2 and at least one cell strand n connected in series

Teilzeilstränge, which are connected at n + 1 nodes and wherein the first node point at the beginning of the cell strand and the η + 1-th node is at the end of Zelistrangs;

where, for 1≤x≤n-1 and

an x-th controllable half-bridge comprising two asynchronously switchable switching devices between the i-th node, with 1 ≤ i ≤ x and

and the jth node, with x + 2≤j≤n + 1 and

of

Cell strand is connected and a node between the two switching devices is connected to the x + 1-th node of the cell strand, the first half-bridge for providing a target voltage on the associated first sub-cell strand can be activated as long as a voltage that drops in the first sub-cell string, smaller or is equal to a predetermined respective voltage limit value and the first half-bridge is deactivatable, as long as a voltage which drops in the first Teilzeilstrang, is greater than the predetermined respective voltage limit, and

wherein the η-1-th half-bridge for providing a target voltage at the associated n-th sub-cell strand can be activated, as long as a voltage falling in the n-th sub-cell strand is less than or equal to a predetermined respective voltage limit and the η-1-th half bridge can be deactivated is as long as a voltage that drops in the n-th sub-cell string is greater than the predetermined respective voltage limit.

In a preferred embodiment, the entirety of the n-1 half-bridges of Cell strand designed to replace a whole of freewheeling diodes of the cell strand of the photovoltaic module.

In this case, the entirety of the n-1 half-bridges is to be understood as meaning all components which are necessary in order to configure the half-bridges for the time sequence. This set of components represents a balancing circuit that compensates deviations of individual partial cell phase voltages from the setpoint.

Another application of the balance circuit are lithium-ion batteries dar. In a strand of n lithium-ion batteries, all cells are always exactly the same voltage. The control circuit then has the goal of preventing a falling below a discharge limit or the exceeding of a charging limit of the cell voltages. Such a control circuit is activated via a connected battery management system (BMS) or by independent voltage monitoring. An additional interlock signal provided by the half-bridge controller may serve to shut down the loader / unloader. In general, an identical division of a total voltage from n series-connected real sources / loads with voltage-dependent currents via the duty cycle half-bridges and x = 1 ... n-1 with the balance circuit

will be realized.

A further aspect for achieving the object relates to a method for controlling a photovoltaic module having at least one cell strand,

wherein at least one cell strand has n series-connected partial cell strands, with n≥ 2 and

where, for 1≤x≤n-1 and

an x-th controllable half-bridge comprising two asynchronously switchable switching devices is configured,

the method comprising the steps of:

Activating the first half-bridge to provide a setpoint voltage at the associated first sub-cell string, as long as a voltage that drops in the first part-cell strand is less than or equal to a predetermined respective voltage limit value, Deactivating the first half-bridge as long as a voltage falling in the first sub-cell string is greater than the predetermined respective voltage limit, and

Activating the η-1 th half-bridge to provide a target voltage at the associated n-th subcell line as long as a voltage falling in the n-th subcell line is less than or equal to a predetermined respective voltage limit,

- Disabling the η-1-th half-bridge, as long as a voltage that drops in the n-th sub-cell strand is greater than the predetermined respective voltage limit. In a further preferred embodiment, for n≥3 and that

Procedures following additional steps:

Activating the xth and the x + 1st half bridges to provide a target voltage at the associated x + 1st subcell line as long as a voltage falling in the x + 1th subcell line is less than or equal to a predetermined respective voltage limit

Deactivating the xth and x + 1th half bridges as long as a voltage falling in the x + 1th subcell line is greater than the predetermined respective voltage limit. For the above-mentioned aspects and in particular for preferred embodiments thereof, the statements made above or below regarding the embodiments of the respective other aspects also apply.

In the following, individual embodiments for solving the problem will be described by way of example with reference to the figures. In this case, the individual embodiments described have in part features which are not absolutely necessary in order to carry out the claimed subject matter, but which provide desired properties in certain applications. Thus, embodiments are also to be regarded as falling under the described technical teaching, which does not have all the features of the embodiments described below. Furthermore, in order to avoid unnecessary repetition, certain features will only be described in relation to individual ones below mentioned embodiments mentioned. It should be noted that the individual embodiments should therefore be considered not only in isolation, but also in a synopsis. Based on this synopsis, those skilled in the art will recognize that individual embodiments may also be modified by incorporating one or more features of other embodiments. It should be understood that a systematic combination of the individual embodiments having single or multiple features described with respect to other embodiments may be desirable and useful, and therefore should be considered and included within the scope of the specification.

Brief description of the figures

Figure 1 shows various simplified representations of PV modules, each with only one cell strand consisting of three sub-cell strands according to the prior art;

Figure 2 shows two simplified representations of the power flow within a PV module with shading of partial cell strands according to the present invention.

Figure 3 shows a simplified representation for retrofitting a

Control circuit in a PV module on a standard junction box according to a preferred embodiment of the present invention.

FIG. 4 shows a schematic circuit diagram of a first sub-cell string of a PV module with an associated buck converter. FIG. 5 shows a schematic circuit diagram of a central sub-cell string of a PV module with an associated buck converter. Figure 6 shows a schematic diagram of the entire circuit of a

PV module according to a preferred embodiment of the present invention. FIG. 7 shows a schematic circuit diagram of a cell strand with three

Sub-cell strands and a balance circuit for optimizing the Teilzellstrangleistungen.

FIG. 8 shows a schematic circuit diagram of a cell strand with five

Teilzeilsträngen and another embodiment of a

Balance circuit for optimizing the partial cell line performance.

Figure 9 shows a schematic diagram of the entire circuit of a

PV module according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE FIGURES FIGS. 1 to 8 relate by way of example to PV modules 10 with exactly one cell strand 14 divided into three partial cell strands 16_1, 16_2, 16_3. However, according to the present invention, the structural and functional features of these examples can also be transferred to PV modules with more than one cell strand, wherein at least one cell strand has more than two partial cell strands.

FIG. 1 shows simplified representations of PV modules 10 with in each case only one cell strand 14 according to the prior art. The cell strand 14 in each case has three partial cell strands 16_1, 16_2, 16_3. An output voltage V _{m is applied} to all PV modules 10 between their module terminals 12_1 and 12_2. Different measures for optimizing performance or for protection against thermal damage of the PV module in case of partial shading are shown. FIG. 1a shows a PV module! 10 without measures against partial shading or failure of one of the partial cell strands 16_1, 16_2 and 16__3. The partial cell strings 16_1, 16_2 and 16_3 are connected in series between the module connections 12_1 and 12_2 of the PV module. The output voltage V _{m of} the cell strand 14 or of the PV module 10 results from the sum of the voltages Vi, V2 and V3 at the partial cell strings 16_1, 16_2 and 16_3. In this case, the partial cell extruded currents h, I2 and at the partial cell strands 16 1, 16 2 and 16_3 all correspond to the module current Im. The modulatory current depends on the smallest of the partial cell extruded currents

, Thus, in the case of shading of a subcellular strand, the modulo flow Im is limited to the subcellular strand current of this subcellular strand. If one of the partial cell strands completely fails due to shading or interference, the entire cell strand 14 or the entire PV module 10 fails and no output power is provided at the PV module. Due to the limited output of the output power of unshaded sub-cell strands, the PV module can be thermally damaged during partial shading.

FIG. 1b shows a PV module 10 with subcell strands 16 1, 16_2 and 16_3 arranged in series with a freewheeling diode or bypass diode 40_1, 40_2 and 40_3 arranged in parallel in each case. In the event of a fault, for example due to shading or failure of one or more of the partial cell strands 16_1, 16_2 and 16_3, the affected partial cell strand can be bridged via the respective freewheeling diode. As an example, the partial cell strand 16_3 is disturbed and is bridged over the freewheeling diode 40_3. The partial cell strand 16_3 thereby fails completely and no longer delivers any output power. The output voltage Vm of the cell strand 14 or of the PV module 10 thus results approximately from the sum of the voltages Vi and V2 to the operating in normal operation partial cell strands 16 1 and 16 2. The partial cell extraneous currents and I2 to the partial cell strands 16_1 and 16 2 and the current at the freewheeling diode

In this case, if one of the partial cell strands 16_1, 16_2 and 16_3 fails due to shading or interference, then not all of the cell strand 14 or the entire PV module 10 fails.

FIG. 1 c shows a PV module 10, in which the serial coupling of the partial cell strands 16_1, 16 2, 16 3 and the PV module can not therefore be implemented on a standard connection box for PV modules. The partial cell strings 16_1, 16_2 and 16_3 are connected in parallel to the inputs of a respective buck converter 18_1, 18_2 and 18_3. The buck converter 18_1 is coupled via an output to the module terminal 12 1 and to a first output of the buck converter 18 2. A second output of the buck converter 18_2 is coupled to an output of the buck converter 18_3 and to the module terminal 12 2. The partial cell strings 16_1, 16_2 and 16_3 are each operated via the buck converters 18_1, 18_2 and 18_3. Without shading, the partial cell strands 16_1, 16_2 and 16_3 each deliver their maximum achievable output voltage to the respective step-down converter 18_1, 18_2 and 18 3. In the event of shading, the affected partial cell line is operated by the assigned step-down converter with MPPT and supplies a reduced output voltage VX.MPPT to the assigned output voltage step-down converter. Due to the occurrence of power loss within all buck converters 18_1, 18_2 and 18_3, a power reduction of the PV module occurs both in normal operation and in the event of shading. The power reduction is dependent on the efficiencies of the buck converters 18_1, 18_2 and 18_3.

FIG. 1d shows a PV module 10 with partial cell strands 16_1, 16_2 and 16_3 arranged in series. The partial cell strings 16_1, 16_2 and 16_3 are connected in parallel to the inputs of a galvanically separated DC-DC converter 18_1, 18_2 and 18_3. The galvanically isolated DC-DC converter 18 1, 18_2 and 18_3 are each coupled via a first output to the module terminal 12_1 and via a second output to the module terminal 12_2. The galvanically isolated DC-DC converter 18_1, 18_2 and 18_3 are based on bidirectional galvanically isolated DC-DC converters, each with a transformer for galvanic isolation of the input and output of the galvanically isolated DC-DC converter 18_1, 18_2 and 18_3. The partial cell strings 16_1, 16_2 and 16_3 are each operated via the galvanically isolated DC voltage converters 18_1, 18_2 and 18_3 for power optimization. Without shading, the partial cell strands 16_1, 16_2 and 16_3 each deliver their maximum achievable output voltage at the respective galvanically isolated DC-DC converter 18_1, 18_2 and 18_3. In the event of shading, the affected subcell line is operated by the associated galvanically isolated DC voltage converter with MPPT and provides a reduced output voltage at the subcell line. This results from the occurrence of

Power loss within all galvanically isolated DC-DC converter 18_1, 18_2 and 18 3, both in normal operation and in the event of shading a power reduction of the PV module. The power reduction depends on the efficiencies

the galvanically isolated DC-DC converter

and 18_3. In addition, the module current is reduced by the circuit. By the serial coupling of the partial cell strands

The PV module can be implemented on a standard connection box for PV modules. In this case, an external wiring between the strands is necessary.

FIG. 2 shows simplified representations of a PV module 10 with only one cell strand 14 according to the present invention and examples of the power flow within the PV module in the case of partial shading. The cell strand 14 has three series-arranged partial cell strands 16_1, 16_2, 16_3. An output voltage Vm is applied to the PV module 10 between the module connections 12_1 and 12_2. The partial cell strings 16_1, 16_2 and 16_3 are connected in parallel to the inputs of a respective buck converter 18_1, 18 2 and 18 3. The buck converter 18_1 is coupled via an output to the module terminal 12 1 and to a first output of the buck converter 18_2. A second output of the buck converter 18_2 is coupled to an output of the buck converter 18 3 and to the module terminal 12 2. The input and output of the buck converters 18_1, 18_2 and 18 3 are each not electrically isolated.

FIG. 2a shows the power flow of the PV module when the partial cell strand 16_1 is shaded at the beginning of the cell strand 14. The shading causes the partial cell strand current to sink below the module current Im and the buck converter 18_1 is activated.

In this case, the buck converter 18_1 operates by MPPT the sub-cell string 16_1 at the voltage

In the two inputs of the Tiefsetzstellers 18_1 on the one hand, the reduced partial cell extraneous current flows from the Teilzellstrang 16_1 and on the other hand

Electricity from the power line 16_2. In Tiefsetzstelier 18 1 is about

the switching cycle duration d with

the output current is set to the value of the modulo current Im. The performance on the partial cell strand 16_1 thus results in:

The performance of the entire PV module results in:

FIG. 2b shows the power flow of the PV module when the partial cell strand 16_2 is shaded between the partial cell strands 16_1 and 16_3. Due to the shading, the partial cell strand current drops below the module current and the buck converter 18 2

is activated. In this case, the buck converter 18_2 operates by MPPT the sub-cell string 16_2 at the voltage V2, MPP. The unshaded partial cell strands 16 1 and 16_3 lead via the outputs of the buck converters 18 1 and 18_3 the benefits and to the outputs of the buck converter 18 2 and

increase the power at the subcell line 16_2 via the current I2, LCMPP from the input of the buck converter 18_2. The performance on the partial cell strand 16_2 thus results in:

Partial cell string 16_2 can be operated at V2, MPP, without limiting the total module current Im. The performance of the entire PV module results in:

FIG. 3 shows a simplified representation for retrofitting a control circuit in a PV module of a standard connection box according to a preferred embodiment of the present invention. The PV module in the standard connection box comprises the module connections 12_1 and 12_2 and the nodes 28_1, 28 2, 28 3 and 28_4. By default, a divisional string 16_1, 16_2, 16_3 and a freewheeling diode 40_1, 40_2, 40_3 are each connected in parallel by default. When retrofitting, the free-wheeling diodes 40_1, 40_2 and 40_3 are first removed and the wiring between the module connection 12_1 and node 28_1 and between the module connection 12 2 and node 28_4 is interrupted. Thereafter, the buck converters 18 1, 18_2 and 18_3 are integrated into the standard connection box. For step-down converter 18_1, step-off converter output 22_1 1 is connected to module connection 12_1, step-down converter input 20_11 to node node 28_1, and step-down converter input 20_12 to node node 28 2. For buck converter 18_2, buck converter output 22 21 is connected to module terminal 12_1, buck converter output 22 22 is connected to module terminal 12 2, buck converter input 20_21 is connected to node node 28_2, and buck converter input 20_22 is connected to node node 28_3. For the buck converter 18_3, the buck converter output 22_32 is connected to the module terminal 12_2, the buck converter input 20_31 to the node pin 28_3 and the buck converter input 20 32 to the node pin 28_4. All electronic components of the retrofitted PV module are thus completely within the standard connection box and only the two module connections 12_1 and 12_2 lead to the outside for external connection. There is no need for additional external wiring between multiple retrofitted PV modules to build a PV system.

FIG. 4 shows a schematic circuit diagram of a first sub-cell string 16_1 of PV module 10 with associated buck converter 18_1. In this case, the first sub-cell string 16_1 and the buck-set input are connected in parallel between the nodes 28_1 and 28 2. In addition, the first buck converter output 22__11 is coupled to the module terminal 12_1. The buck converter 18_1 has a buck converter switching device 24_1 with exactly one buck converter switch 26_1, which is controlled by the buck converter control 36. Within the buck converter 18_1 is connected between the buck converter input 20_11, or the input anode, and the buck converter output 22 1 1, or the output anode, in series, the buck converter switch 26_1 and an inductance or coil 30_1. In addition, a diode 32_1 is connected in parallel with the associated subcell line 16_1. The Diode 32_1 is connected in the reverse direction, the anode of the diode 32_1 being applied to the step-down converter input 20_12 or the input cathode, and the cathode of the diode 32_1 being present between the step-down converter switch 26_1 and the inductor 30_1. In addition, the buck converter input 20_12 is connected directly to the buck converter output 22 12. In addition, between the buck converter inputs 20_1 1 and 20_12 a capacity 34_1 1 and between the buck converter outputs 22 1 1 and 22 12 a capacity 34_12 connected.

Between the buck converter outputs 22 1 1 and 22_12, an output voltage VIA is measured at the voltage measuring device 38_1. Without shading this output voltage VIA is greater than the predetermined voltage limit VIG for the buck converter 18 1 and the buck converter switch 26_1 remains disabled and permanently closed. In the case of a drop in the output voltage VIA by shading to or below the predetermined voltage limit VIG the buck converter switching device 24 1 is activated and performed a few hundred to several million switching cycles per second on Tiefsetzstellerschalter 26 1. The output voltage VIA or the output current Im can be adjusted by controlling the on and off times of the buck converter switch 26 1 with the buck converter control 36.

FIG. 5 shows a schematic circuit diagram of a middle sub-cell strand 16_2 of a PV module 10 with associated buck converter 18_2. In this case, the partial cell string 16_2 and the buck converter input are connected in parallel between the nodes 28_2 and 28_3. The buck converter 18_2 has two output anodes or step-down steplete outputs 22_21 and 22 23 and two output cathodes or buck converter outputs 22_22 and 22_24. In this case, the buck converter outputs 22_21 and 22_23 are coupled to the module terminal 12 2 as well as buck converter outputs 22 22 and 22_24 to the module terminal 12 2. Between the input anode or buck converter input 20_21 and a first buck converter node 42_21, a first inductor 30_21 is arranged. A first buck converter switch 26_21 is coupled between the first buck converter node 42 21 and the module terminal 12 1 and connected between the module terminal 12_2 and the first buck converter. node 42_21 is a first diode 32 21 arranged in the reverse direction. In addition, a second inductance 30 22 is arranged between the input cathode or step-down divider input 20_22 and a second step-down step node 42_22. A second buck converter switch 26_22 is coupled between the second buckle splitter node 42_22 and the module pad 12 2, and a second diode 32_22 is connected in the reverse direction between the second buckle splitter node 42_22 and the module terminal 12_1. Between the step-down divider input 20_21 and the step-down divider input 20_22, a capacitor 34_2 is connected in parallel to the part cell line 16_2.

A step-down converter voltage V2T is applied between the first step-down stepping node 42 21 and the second step-down stepping node 42_22 and is measured at the voltage measuring device 38_2. Without shading, the buck converter voltage V2T is greater than the predetermined voltage limit value V2G, and the buck converter switches 26_21 and 26_22 of the buck converter switching device 24_2 remain deactivated and permanently open. Thus, no current flows through the buck converter 18_2 without shading, the current h through the sub-cell strand 16_2 is identical to the module ström IM and there is no power dissipation at the buck converter 18 2. In the case of a sinking the buck converter voltage V2T at or below the predetermined voltage limit V2G the buck converter 18_2 by shading the buck converter switching device 24_2 is activated and a few hundred to several million switching cycles per second performed on the two buck converter switches 26 21 and 26_22. In this case, electrical power is unidirectionally transferred from the two normal-operating partial cell strings 16_1 and 16_3 to the buck converter output of the buck converter 18_2 and through the buck converter 18_2 to the associated partial cell string 16_2. The unidirectional transfer of power to the shaded partial cell string 16_2 can be achieved by controlling the input voltage. and OFF times of the buck converter switches 26_21 and 26 22 are set with the buck converter control 36.

FIG. 6 shows a schematic circuit diagram of the entire circuit of a PV module 10 with exactly one cell strand 14 divided into three serially coupled partial cell strands 16_1, 16_2, 16_3 according to a preferred embodiment of the present invention.

For the entire circuit of the PV module 10, the schematic diagram of the first partial cell string 16_1 with associated buck converter 18_1 of Figure 4 by serial connection of the second Teilzellstrangs 16_2 with associated buck converter 18_2 of Figure 5 at the node 28_2 continued and by connecting the third Teilzellstrangs 16_3 completed with associated buck converter 18_3 at node 28 3. The construction of the buck converter 18_3 represents an alternative to the construction of the buck converter 18_1 according to FIG. 4, with essentially the connections of the anodes and cathodes of the buck converter 18_1 being mirrored, with the exception of the reverse reverse direction of the diode 32_3. For the control of the entire circuit of the PV module, the three voltages VIA, V2T and V3A are detected by the voltage measuring devices 38_1, 38_2 and 38_3 and forwarded to the buck converter control 36. The buck converter control 36 then controls the four buck converter switches 26_1, 26_21, 26_22 and 26_3 with four control signals.

In contrast to known PV modules, which are based on optimizing the performance of the individual strings by means of bidirectional, galvanically isolated flux converters, the PV module power optimization circuit according to the invention utilizes the supply of power from unshaded sub-cell strings to shaded sub-cell strings. For the unidirectional power supply, a galvanic isolation by a transformer in the buck converter is not required.

FIG. 7 shows a schematic circuit diagram of a cell strand 14 with three series-connected partial cell strings 16_1, 16_2 and 16 3 and a balance circuit 70 for optimizing the partial cell string powers Pi, P2 and P3.

In this case, between the nodes 28_1 and 28_2 parallel to the partial cell strand 16_1 a Teiizellstrangkondensator 56_1 and a Teiizeilstrangspannungmessgerät 58 1 connected, which monitors the voltage Vi on the Teilzellstrang 16_1. Between the nodes 28_2 and 28_3 parallel to the partial cell strand 16_2 is accordingly a Teiizellstrangkondensator 56 2 and a Teiizellstrangspannungs- measuring device 58_2 and between the nodes 28_3 and 28 4 parallel to Teilzeilstrang 16_3 a Teiizellstrangkondensator 56_3 and a Teilzellstrang- voltage meter 58_3 is connected. The voltages determined by the partial cell voltage measuring devices 58 1, 58_ 2 and 58_ 3 which drop over the partial cell strings 16_ 1, 16_ 2 and 16_ 3 are transmitted to a half-bridge controller 52. Parallel to the cell strand 14 with its partial cell strands 16_1, 16_2 and 16_3, two half bridges 44_1 and 44_2 and one cell strand capacitor 60 are connected between the nodes 28_1 and 284. The half-bridge 44_1 consists of two series-connected switching devices 46_11 and 46_12 with a half-bridge node 50_1 between the switching devices. Accordingly, the half bridge 44 2 consists of two series-connected switching devices 46 21 and 46 22 with a half-bridge node 50_2 between the switching devices. The switching devices 46_11, 46_12, 46_21 and 46_22 each have a switch and a diode 48_11, 48_12, 48_21 and 48_22, which are connected in parallel. The diodes 48_11, 48_12, 48_21 and 48_22 are each arranged in the reverse direction. Between the half-bridge node 50_1 of the half-bridge 44_1 and the node 28_2 a half-bridge inductor 54_1 is arranged and between the half-bridge node 50_2 of the half-bridge 44 2 and the node 28_3 is a half-bridge inductance 54_2. The half-bridges 44_1 and 44_2, in particular their respective switching devices 46_11 and 46 12 and 46_21 and 46_22, are each controllable via the half-bridge controller 52.

The lighting-dependent current-voltage characteristic of the partial cell strings 16_1, 16_2 and 16_3 define a current h for each voltage Vi, a current b for V2 and a current b for V3. The cell strand voltage Vzst = V1 + V2 + V3 results from the series connection of the partial cell strings 16_1, 16_2 and 16_3. In the case that the half-bridge 44_1 is activated, a current flows through the half-bridge inductance 54_1. Accordingly, when the half-bridge 44_2 is activated, it flows through the half-bridge inductor 54_1. Inductance 54 2 a current IL2. From the node equations for the nodes 28_2 and 28_3 it follows that the currents IL ₁ and IL ₂ control the currents

can. If the partial cell voltage V3 falls below a defined voltage threshold V3G, for example due to shading of the partial cell strand 16_3, then the half-bridge controller 52 activates the half bridge 44_2 and controls its switching devices 46_21 and 46_22 by presetting a setpoint voltage V3S in the MPPT. This is done by periodic asynchronous switching of the switching devices 46_21 and 46 22 with a pulse width modulated controlled signal with duty cycle

with the turn-on time T0N.4e_.21 of switching unit 46_21 in relation to the period

the half-bridge 44_2. In this case, instead of the sunken partial cell voltage V3, the increased setpoint voltage V3S = Vzst * D2 at the node point 28_3 sets in and the partial cell voltage

* D2 drops in partial cell strand 16_3. The increased partial cell voltage Va.ypp causes in the shaded Teilzelistrang 16_3 a reduced Teilzellstrangstrom b, but which is compensated by the current IL2.

Asynchronous switching of the switching devices 46_21 and 46 22 means that for the duration of time, the switch of the switching device 46_21

closed and the switch of the switching device 46 22 is open and for the duration of time TOFF, 46_2I = TON, 46_22 the switch of the switching device 46_21 opened and the switch of the switching device 46_22 is closed. The diodes 48_21 and 48_22 thereby ensure that the current IL2 can continue to flow, even if in the change of state of the half-bridge 44_2 from the state of the period TON.46_2I = TOFF, 46_22 to the state of the period neither of the two switches for

a negligible dead time TTOT, 44 2 is closed.

When the partial cell voltage V2 at the partial cell strand 16_2 falls below a defined voltage limit V2G, the half-bridge controller 52 activates the half-bridges 44 2 and 44_1 and controls their switching devices 46_21 and 46_22 and 46_1 1 and 46_12 by presetting desired voltages Vss and V2S in the MPPT. For the half bridge 44 2, this is done as already described above. The half-bridge 44_1 becomes by periodically asynchronously switching the switching devices 46_11 and 46_12 with a pulse-width-modulated regulated signal with duty cycle

with the turn-on time TON, 46_H controlled by switching unit 46_1 1 relative to the period. This raises the node 28 2 the

Target voltage and at the node 28_3 the target voltage V3S = (Vzst

* D2) and the partial cell voltage drops in the

Teilzellstrang 16_2 from. The increased partial cell voltage

caused in the shaded sub-cell strand 16_2 a reduced partial cell strand current I2, but which is compensated by the current IL ₁ .

Asynchronous switching of the switching devices 46_11 and 46 12 again means that for the duration of time

the switch of the switching device 46_11 is closed and the switch of the switching device 46__12 is open and for the duration of time

the switch of the switching device 46_11 is opened and the switch of the switching device 46 12 is closed. The diodes 48_11 and 48_12 thereby ensure that the current IL _{1 can} continue to flow, even if the state change of the half-bridge 44_1 from the state of the period

to the state of the period neither

Switch is closed for a negligible dead time.

If the partial cell voltage V ₁ falls below a defined voltage threshold VIG, for example due to shading of the partial cell string 16_1, the half-bridge controller 52 in turn activates the half-bridge 44 1 and controls its switching devices 46_1 1 and 46_12 by presetting a nominal voltage Vis in the MPPT. This is done by periodic asynchronous switching of the switching devices 46_11 and 46_12 with a pulse width modulated controlled signal with duty cycle

with the turn-on time

of switching unit 46_11 in relation to the period

the half-bridge 44_1. It turns at the junction

the reduced setpoint voltage and the

Part cell voltage

falls off in the partial cell strand 16_1. The increased partial cell voltage

caused in the shaded sub-cell strand 16_1 a reduced Teilzellstrangstrom but by the current

is compensated.

When sinking one or more of the Teüzellspannungen Vi, V2 and V3 in the cell sträng 14 thus results in the cell string voltage through the series connection to:

According to the lighting-dependent current-voltage characteristics of the partial cell strands 16_1, 16_2 and 16_3, the cell current Izst results in:

Respectively to:

For the normalfail that all sub-cell strands are equally strongly illuminated and provide the same current, the currents I _L1 = I ₂ - I ₁ and IL ₂ = I ₃ - I ₂ over a period T ₄₄ j zuIL ₁ = 0 A and over a period T44_2 to IL2 = 0 A. For the normal fail can thus be dispensed with a switching of the half-bridges 44_1 and 44_2 and all switches remain off. The balance circuit 70 is then in an inactive state.

As an example of shading, the half-bridge controller 52 should now specify the duty cycles D ₁ and D ₂ with Di = 66% and D ₂ = 33%, that is, the setpoint voltages

Currents Li and IL2 caused. Thereupon, according to the characteristics of the partial cell strands 16 1, 16_2 and 16_3, the currents are established

and yield, according to the above-mentioned knot equations, the associated cell strand current Izst. For identical characteristics of the sub-cell strands and applies

Half-bridge inductors 54 1 and 54 2 are de-energized. For an exemplary shading of the sub-cell strand 16_2 should apply and the

Partial cell voltage remain unchanged from the normal case. Then follows

from the fact that the cell current Izst on a

the cell strand decreases and the cell strand output P decreases

emits. The same value results

FIG. 8 shows a schematic circuit diagram of a cell strand 14 with five series-connected partial cell strings 16_1, 16_2, 16_3, 16_4 and 16_5 of a further embodiment of a balance circuit 70 for optimizing the partial cell strand powers Ρι, P2, P3, P4 and P5.

In this case, a partial cell strand capacitor 56_1 and a Teilzeilstrangspannungsmessgerät 58_1 is connected between the nodes 28 1 and 28_2 parallel to the partial cell strand 16_1 connected, which monitors the voltage Vi on the partial cell strand 16_1. Between the nodes 28_2 and 28_3 parallel to the sub-cell strand 16_2 is accordingly a sub-cell strand capacitor 56_2 and a Teilzellstrangspannungs- measuring device 58 2, between the nodes 28_3 and 28_4 parallei to Teilzellstrang 16_3 a Teilzellstrangkondensator 56_3 and a Teilzellstrang- voltage meter 58_3, between the nodes 28 4 and 28_5 a partial cell strand capacitor 56_4 and a partial cell strand voltage measuring device 58_4 are connected in parallel with the partial cell strand 16_4 and a partial cell strand capacitor 56_5 and a partial cell strand voltage measuring device 58_5 are connected between the nodes 28_5 and 28_6 in parallel to the partial cell strand 16. The voltages determined by the partial cell voltage measuring devices 58_1, 58_2, 58 3, 58_4 and 58_5, which drop across the partial cell strings 16_1, 16_2, 16_3, 16_4 and 16_5, are transmitted to a half-bridge controller 52. Parallel to the cell strand 14 with its sub-cell strands 16_1, 16_2, 16_3, 16_4 and 16_5, a cell strand capacitor 60 is connected between the nodes 28_1 and 28_6.

The four partial cell strings 16_1, 16_2, 16_3, 16_4 and 16_5 are assigned four half bridges 44_1, 44_2, 44_3 and 44_4. The half bridges each consist of two series-connected switching devices 46_1 1 and 46_12, 46_21 and 46_22, 46_31 and 46_32 and 46_41 and 46 42. The switching devices each have one Switch and a diode (48_11, 48_12, 48_21, 48_22, 48_31, 48_32, 48_41 and 48_42), which are connected in parallel. The diodes are each arranged in the reverse direction. In contrast to the embodiment in FIG. 7, however, the half bridges are not all connected between the first node 28 1 and the sixth node 28 6 of the cell strand 14. Instead, the half-bridge 44_1 is connected between the first node 28_1 and the third node 28_3 of the cell string 14, and the half-bridge node 50_1 between the switching devices 46_11 and 46_12 is connected to the node 28_2 of the cell string 14 via the half-bridge inductor 54_1. The half-bridge 44 2 is connected between the second node 28 2 and the fourth node 28 4 of the cell string 14, and the half-bridge node 50_2 between the switching devices 46_21 and 46_22 is connected to the node 28_3 of the cell string 14 via the half-bridge inductor 54_2. Accordingly, the half-bridge 44_3 is connected between the third node 28_3 and the fifth node 28_5 of the cell string 14, and the half-bridge node 50_3 between the switching devices 46_31 and 46_32 is connected to the node 28_4 of the cell string 14 via the half-bridge inductor 54_3. The half-bridge 44_4 is connected between the fourth node 28_4 and the sixth node 28 6 of the cell string 14, and the half-bridge node 50_4 between the switching devices 46_41 and 46_42 is connected to the node 28_5 of the cell string 14 via the half-bridge inductor 54_4. In this case, the first half-bridge 44_1 and the third half-bridge 44_3 are connected in series to a first half-bridge line 68_1 via the node 28_3 of the cell string 14. The second half-bridge 44_2 and the fourth half-bridge 44_4 are in turn connected via the node 28_4 of the cell string 14 in series to a second half-bridge string 68_2.

The half-bridges 44_1, 44_2, 44_3 and 44_4, in particular their respective switching devices 46_1 1 and 46_12, 46_21 and 46_22, 46_31 and 46_32 and 46_41 and 46_42, are each controllable via the half-bridge controller 52.

The illumination-dependent current-voltage characteristics of the partial cell strings 16_1, 16_2, 16_3, 16_4 and 16_5 each define a current for the voltages Vi, V2, V3, V4 and V5. The cell-string voltage Vzst = V1 + V2 + V3 + V4 + V5 yields

itself from the series connection of the partial cell strands 16_1, 16_2, 16_3, 16_4 and 16_5. In the case that the half-bridge 44_1 is activated, a current flows through the half-bridge inductance 54_1

Correspondingly, when the half bridge 44_2 is activated, a current IL2 flows through the half bridge inductance 54_2, when the half bridge 44_3 is activated, a current IL3 flows through the half bridge inductance 54_3 and a current IL4 through the half bridge inductance 54_4 when the half bridge 444 is activated. It follows from the node equations for the nodes 28_2, 28_3, 28_4 and 28_5 that the currents I, LI _1, L2, IL3 and IL4 can control the currents.

For example, one or more of the sub-cell voltages decreases

Shading of the respective sub-cell strand below a specified voltage limit Vi, 2.3,4,5G, the half-bridge controller 52 activates all half-bridges 44_1, 44_2, 44_3 and 44_4 and controls their switching devices by specifying a respective target voltage Vi, 2,3,4,5s in MPPT. This is done by periodic asynchronous switching of the respective switching devices with a pulse width-modulated controlled signal with duty cycle

with the turn-on time

from the respective first switching unit with respect to the period of the half bridge 44_1, 2,3,4. there

instead of the sunken partial cell voltage Vi, 2, 3, 4, 5, the increased nominal voltage Vi, 2, 3, 4, 5 s is set at the respective node and the partial cell voltage

drops in the respective Teilzeilstrang. The increased partial cell tension

caused in each shaded sub-cell strand a reduced Teilzeilstrangstrom 11.2,3,4.5, but compensated by the currents

becomes.

FIG. 9 shows a schematic circuit diagram of the entire circuit of a PV module according to another preferred embodiment of the present invention. In this case, the circuit from FIG. 7 is supplemented by a cell strand setting plate 62 operated in the MPPT. Accordingly, the circuit from FIG. 8 can also be supplemented by a cell strand setting plate 62 operated in the MPPT. The cell strand subplacer 62 consists of a half bridge 44_3, a buck converter inductance 64 and a buck converter capacitor 66. The half bridge 44_3 is arranged between the nodes 28_1 and 284 parallel to the cell string 14 and consists of two series-connected switching devices 46_31 and 46_32 with a half-bridge node 50_3 between the switching devices. The switching devices 46_31 and 46_32 each have a switch and a diode 48_31 and 48_32, which are connected in parallel. The diodes 48_31 and 48_32 are each arranged in the reverse direction. The buck converter inductance 64 is arranged between the half-bridge node 50 3 and the module terminal 12_1 and the buck converter capacitor (66) between the first module terminal (12_1) and the second module terminal (12_2). The node 28_4 is connected to the module port 12 2.

In the example shown, the PV module 10 has only one cell strand 14. Thus, the PV string current Ipvst reduces to the current resulting from the cell string current Izst. For a plurality of cell strings, the photovoltaic string current Ipvst would have to be added from the resulting currents of the cell string currents. To maximize the photovoltaic module power PM = Ipvst * VM, the cell strand sinker 62 sets the cell string current Izst to the desired PV string current Ipvst at the module output 12 1. For this purpose, the half-bridge controller 52 activates the half-bridge 44_3 and controls its switching devices 46_31 and 46_32 by specifying the PV string current Ipvst in the MPPT. This is done by periodic asynchronous switching of the switching devices 46_31 and 46_32 with a pulse width modulated controlled signal with duty cycle

with the turn-on time

of switching unit 46_31 with respect to the period

the half-bridge 44_3. To get the maximum output power of the

PV module, the half-bridge controller 52 may sequentially vary the values of Di, D2 and D3 according to any algorithm for MPP search and maximize the voltage VM. Due to the logarithmic voltage curve of a Solar cell depending on the short-circuit current or the lighting, a simplified method with Di = 66% and D2 = 33% is conceivable in which the voltages apply and low mismatch losses in favor of a fast

Optimization and a minimum of control effort can be accepted. The intervention of the Baianc circuit 70 operates the sub-cell strands 16_1, 16_2 and 16_3 symmetrically and in combination with the cell strand foundation 62 in each case with voltages close to the MPP voltage of the sub-strands and

reliably prevents the formation of hotspots.

Claims

claims

1. photovoltaic module (10) having a first module connection (12_1) and a second module connection (12_2) and at least one cell strand (14),

wherein at least one cell strand (14) comprises n series-connected partial cell strands (16_1..16_n) with n ≥ 2 and

where, for 1 ί χ ί η and an x-th subcellular strand (16_x) each one

x-th buck converter (18_x) is associated with two buck converter inputs (20_x1, 20_x2) and a buck converter circuit means (24_x),

wherein the xth buck converter (18_x) is connected in parallel with the associated xth subcell train (16_x) via the two buck converter inputs (20_x1, 20_x2),

wherein the buck converter switching means (24_x) of the x-th buck converter (18_x) is activated as long as a voltage in the x-th

Down converter (18_x) drops, is less than or equal to a predetermined respective voltage limit (VXG), and

wherein the buck converter switching means (24_x) of the xth buck converter

(18_x) can be deactivated as long as a voltage (VIA, VnA, VyT) which drops in the xth step-down converter (18_x) is greater than the predefined respective voltage limit value (V _X G),

wherein the first buck converter (18_1) has exactly one buck converter output (22_11) which is connected to the first module terminal (12_1), and wherein the nth buck converter (18_n) has exactly one buck converter output (22_n2) connected to the second module terminal (22_n2). 12_2) is connected.

2. Photovoltaic module (10) according to claim 1, wherein, for n 3≥ and and for

2 ≤ y ≤ n-1 and the y-th buck converter (18__y) a first

Buck converter output (22_y1, 22_y3) connected to the first module terminal (12_1) and the y-th buck converter (18_y) one second buck converter output (22_y2, 22_y4) connected to the second module terminal (12 2).

3. photovoltaic module (10) according to claim 1 or 2, wherein the buck converter inputs (20_x1, 20_x2) and the buck converter outputs (22_x1, 22_x2, 22_y1, 22_y2, 22_y3, 22_y4) of the x-th buck converter (18_x) by means of internal circuit within the x -ten Tiefsetzstellers (18_x) are electrically connected directly to each other.

4. photovoltaic module (10) according to claim 2 or 3, wherein the y-th buck converter (18_y) the y-th sub-cell string (16_y) exclusively unidirectional a buck converter

supplies as long as the voltage (VyT), which falls in the y-th buck converter (16_y), is less than or equal to the predetermined voltage limit (V _Y G).

5. photovoltaic module (10) according to claim 4, wherein the first buck converter (18_1) and the n-th buck converter (18_n) the y-th buck converter (18_y) exclusively unidirectional Tiefsetzstellerieistung

supplies.

6. photovoltaic module (10) according to any one of the preceding claims, wherein the predetermined voltage ungsgrenzwert (VXG) of the x-th buck converter (18_x) has a value less than or equal to zero volts and the x-th activated buck converter (18_x) Teilzelistrangleistung (ΡΧ , ΜΡΡ) of the xth sub-cell strand (16_x) is increased.

7. photovoltaic module (10) according to claim 6, wherein the buck converter switching means (24_x) of the x-th buck converter (18_x) periodically switched on activation in order to increase the Teilzelistrangleistung (ΡΧ, ΜΡΡ) of the x-th Teilzellstrangs (16_x).

8. photovoltaic module (10) according to any one of the preceding claims, wherein the predetermined voltage limit of the x-th buck converter (18_x)

each having a fixed voltage limit (VG).

9. photovoltaic module (10) according to any one of the preceding claims, wherein the Photovoitaikmodul (10) comprises a Tiefsetsteliersteuerung (36), by means of which the Tiefsetzstellerschalteinrichtung (24_x) of the x-th buck converter (18_x) is controlled to a Photovoitaikmodulieistung (PM) of Photovoltaic module (10) to maximize and the Tiefsetzsteliersteuerung (36) with maximum power point tracking, MPPT, is formed.

10. photovoltaic module (10) according to any one of claims 2 to 9, wherein the buck converter switching means (24_1, 24_n) of the first and n-th buck converter (18 _1, 18_n) each have a buck converter switch (26_11, 26_n1) and the buck converter switching means (24_y ) of the yth step-down divider (18_y) has a first and a second step-down switch (26_y1, 26_y2).

1 photovoltaic module (10) according to claim 10, in which a module current (IM) and a teiizellstrangstrom (l _x ) by the x-th sub-cell string (16_x) is monitored and the buck converter switch (26_1 1, 26_n1) of the first and n- ten buck converter (18_1, 18_n) closed and the buck converter switch (26_y1, 26_y2) of the y-th buck converter (18_y) are opened when the difference between the module current and Teiizellstrangstrom (Ix) through the x-th sub-cell string (16_x) under a predetermined x-th current limit for the x-th sub-cell strand decreases

12. photovoltaic module (10) according to claim 1 1, wherein the predetermined current limit (IXG) for the x-th sub-cell strand (16_x) has a fixed current limit (IG) and / or the deviation between the module current and

Teiizellstrangstrom (Ix) is in a range of less than 1% to a deviation of less than 10%.

13. photovoltaic module (10) according to any one of the preceding claims, in which an xth capacitor (34_x1) is connected in parallel with the xth subcell line (16_x).

14. Photovoltaic module (10) according to one of the preceding claims, wherein at least one cell strand (14) has three series-connected partial cell strands (S1 ..S3).

15. Control circuit with a plurality of buck converters (18_1, 18_n) for a photovoltaic module (10),

wherein the photovoltaic module (10) has a first module connection (12_1) and a second module connection (12_2) and at least one cell strand (14),

where, for n≥ 2 and

at least one cell strand (14) has n partial cell strands (16_1..16_n) connected in series;

wherein, for 1≤x≤n and xeM, an xth subcell string (16_x) is associated with an xth buck converter (18_x) with two buck converter inputs (20_x1, 20x2) and a buck converter switching device (24_x),

wherein the step-down stage switching means (24_x) of the xth step-down divider

(18_x) is activatable, as long as a voltage (VIA, VnA, VyT), which in the x-th

Buck converter (18_x) drops, less than or equal to a given respective

Voltage limit (VXG) is, and

wherein the buck converter switching means (24_x) of the x-th buck converter (18_x) is deactivated, as long as a voltage in the x-th

Buck converter (18_x) drops, larger than the given one

Voltage limit (V _X G),

wherein the first buck converter (18 1) exactly one buck converter output

(22_11), which is connected to the first module connection (12_1), and wherein the nth buck converter (18_n) exactly one buck converter output

(22_n2) connected to the second module terminal (12 2).

16. Control circuit according to claim 15, wherein the x-th buck converter

(18_x) is designed to have a free-wheeling diode (40_x) of the xth sub-cell string

(16_x) of the Photovoitaikmoduls (10) to replace.

17. A method for controlling a photovoltaic module (10) with at least one cell strand (14),

wherein at least one cell strand (14) comprises n partial cell strands connected in series

(16_1 ..16_n) with n≥ 3 and

where, for 1≤x≤n and

an x-th subcell string (16_x) is in each case assigned an xth subset converter (18_x) with a buck converter switching device (24_x),

the method comprising the steps of:

- Enable the buck converter switching means (24_x) of the x-th buck converter (18_x), as long as a voltage (VIA, VnA, V / r), which falls above the x-th sub-cell string (16_x), less than or equal to a predetermined x-th voltage limit Is (VXG)

- Disabling the buck converter switching means (24_x) of the x-th buck converter (18_x), as long as the voltage above the x-th

Teilzellstrang (16_x) falls, is greater than the predetermined x-th voltage limit, and

Transmission of electrical power between a buck converter input (20_x1, 20_x2) and a buck converter output (22_x1, 22_x2, 22_y1, 22_y2, 22_y3, 22_y4) of the xth buck converter (18_x) by means of internal switching via a direct electrical connection in the xth buck converter ( 18_x).

18. photovoltaic module (10) having a first module connection (12 1) and a second module connection (12_2) and at least one cell strand (14),

wherein at least one cell strand (14) comprises n series-connected partial cell strands (16_1 .. 16_n) connected to n + 1 nodes (28_1 .. 28_n + 1) and wherein the first node point (28_1) at the beginning of the cell strand (14 ) and the n + 1-th node (28_n + 1) at the end of the cell strand (14), with n≥ 2 and ne

where, for 1≤x≤n-1 and an xth controllable half-bridge (44_x)

comprising two asynchronously switchable switching devices (46_x1, 46_x2) between the i-th node (28_i), with 1 si≤x and ie M, and the jth node (28J), with x + 2≤j≤n + 1 and each N, of the cell string (14) is connected and a half-bridge node (50_x) between the two switching devices (46_x1, 46_x2) is connected to the x + 1-th node (28_x + 1) of the cell string (14),

wherein the first half-bridge (44_1) for providing a target voltage (Vis) at the associated first sub-cell strand (16_1) is activated, as long as a voltage (Vi), which decreases in the first sub-cell strand (16_1), less than or equal to a predetermined respective voltage limit (VIG) is and the first half-bridge (44_1) is deactivated as long as a voltage (Vi), which falls in the first Teilzelistrang (16_1) is greater than the predetermined respective voltage limit (VIG), and

wherein the η-1-th half-bridge (44_n-1) for providing a target voltage (Vns) is activatable at the associated n-th partial cell string (16_n) as long as a voltage (Vn) falling in the n-th partial cell string (16_n) is smaller than or equal to a predetermined respective voltage _{limit value} (V _nG ) and the η-1-th half-bridge (44_n-1) can be deactivated as long as a voltage (Vn) which decreases in the nth subcell line (16_n) is greater than the predetermined one respective voltage _limit (V _nG ) is.

19. The photovoltaic module (10) according to claim 18, wherein, for the xth half bridge (44_x), the ith node of the cell string (14) is the first node (28_1) of the cell string and the jth node of the cell string (14) is the n + 1 node (28_n + 1) of the cell rank.

20. The photovoltaic module (10) according to claim 18, wherein, for the xth half bridge (44_x), the i-th node of the cell string (14) is the xth node (28_x) of the row of strings and the jth node of the cell string (14 ) is the χ + 2nd node (28_x + 2) of the cell strand.

21. The photovoltaic module (10) of claim 20, wherein, for n ≥ 3 and 1≤k≤n / 2 and n, k e I;

all odd half-bridges (44_2k-1) are connected in series in a first half-bridge line (68_1) and all straight half-bridges (44_2k) are connected in series in a second half-bridge line (68_2).

22. Photovoltaic module (10) according to any one of claims 18 to 21, wherein, for n ≥

3 and n e M;

the xth and x + 1th half bridges (44_x, 44_x + 1) to provide a

Target voltage (V _x + is) on the associated x + 1-th sub-cell string (16_x + 1) can be activated as long as a voltage (Vx + i), which falls in the x + 1-th sub-cell string (16_x + 1), less than or equal a predetermined respective voltage limit (VX + IG) and the x-th and the x + 1-th half-bridge (44_x, 44_x + 1) are deactivatable, as long as a voltage (Vx + i), in the x + 1-th subcell line (16_x + 1) falls, is greater than the predetermined respective voltage limit (VX + IG) is.

23. Photovoltaic module (10) according to one of claims 18 to 22, wherein the activatable half-bridges (44_1; 44_x, 44_x + 1; 44_n-1) have their two switching devices (46_11, 46_12; 46_x1, 46_x2, 46_x + 1_1, 46_x + 1_2 ; 46_n-1_1, 46_n-1_2) periodically asynchronously switch on activation to provide the setpoint voltages (Vis, Vx + is, Vns) of the associated sub-cell strands (16_1; 16_x + 1; 16_n).

24. Photovoltaic module (10) according to one of claims 18 to 23, wherein the photovoltaic module (10) comprises a half-bridge control (52) by means of which the activatable half-bridges (44_1; 44_x, 44_x + 1; 44_n-1) are activated and controlled, and

wherein the half-bridge controller (52) controls the target voltages (Vis; Vx + is; Vns) of the associated sub-cell strings (16_1; 16_x + 1; 16_n) with Maxim um power point tracking, MPPT.

25th photovoltaic module! (10) according to any one of claims 18 to 24,

wherein an x-th half-bridge inductance (54_x) is connected between the half-bridge node (50_x) of the x-th semiconductor bridge (44_x) and the x + 1-th node (28_x + 1) of the cell strand (14),

26. Photovoltaic module! (10) according to any one of claims 18 to 25,

wherein a cell string capacitor (54) is connected between the first node (28_1) and the η + 1-th node (28_n + 1) of the cell string (14),

27. Photovoltaic module (10) according to one of claims 21 to 26,

where, for 2≤y≤n-1 and

a y-th sub-cell strand capacitor (56_y1) is connected in parallel to the y-th subcell line (16_y).

28. Photovoltaic module (10) according to one of claims 18 to 27,

wherein the cell strand (14) at the first and η-1-th node (28_1, 28_n + 1) is connected via a Zeilstrangetiefsetzsteiler (62) to the first Modulanschiuss (12_1) and the second Modulanschiuss (12_2).

29. Photovoltaic module (10) according to claim 28,

wherein the half-bridge controller (52) includes the row-train-sinking divider (62) and the target voltages

the associated sub-cell strands (16 1; 16_x + 1; 16_n) with maximum power point tracking, MPPT, controls and supplies as the output current of the Zellstranunterffsetzstellers (62) a desired photovoltaic string current (Ipvst).

30. photovoltaic module (10) according to claim 29,

wherein the cell depressing setter (62) comprises the following configuration:

- an n-th controllable half-bridge (44_n) comprising two asynchronously switchable switching devices (46_n1, 46_n2) between the first node (28_1) and the η + 1-th node (28_n + 1) of the cell string (14);

a half-bridge node (50_n) between the two Switching means (46_n1, 46_n2) connected via a buck converter inductor (64) to the first module terminal (12__1) of the photovoltaic module (10);

a buck converter capacitor (66) between the first module terminal (12_1) and the second module terminal (12_2); and

- The η + 1-th node (28_n + 1) of the cell strand (14), which is connected to the second module connection (12_2).

31 control circuit having a plurality of controllable half-bridges (44_1 .. 44_n-1) for a photovoltaic module (10),

wherein the photovoltaic module (10) has a first module connection (12_1) and a second module connection (12_2) and at least one cell strand (14), where, for n≥2 and

at least one cell strand (14) has n series-connected partial cell strands (16_1 .16_n) which are connected to n + 1 nodes (28_1 .. 28_n + 1) and wherein the first node point (28_1) at the beginning of the cell strand (14) and the η + 1th node (28_n + 1) is at the end of the cell strand (14);

where, for 1≤x≤n-1 and

an x-th controllable half-bridge (44_x) comprising two asynchronously switchable switching devices (46_x1, 46_x2) between the i-th node (28_i), with 1≤i≤x and

and the jth node (28J), where x + 2≤ j <n + 1 and

the cell string (14) is connected and a half-bridge node (50_x) between the two switching devices (46_x1, 46_x2) is connected to the x + 1-th node (28_x + 1) of the cell string (14),

wherein the first half-bridge (44_1) for providing a target voltage (V1S) on the associated first sub-cell string (16 1) can be activated as long as a voltage (Vi), which falls in the first Teilzeilstrang (16_1), less than or equal to a predetermined respective voltage limit (VIG ) and the first half-bridge (44_1) is deactivatable as long as a voltage (Vi) falling in the first partial cell string (16_1) is greater than the predetermined respective voltage limit value (VIG), and

wherein the η-1-th half-bridge (44_n-1) for providing a target voltage (Vns) at the assigned nth Teüzeüstrang (16_n) is activated as long as a voltage (V _n ), which decreases in the n-th sub-cell string (16_n) is less than or equal to a predetermined respective voltage limit (VDG) and the η-1 -te half-bridge (44_n-1) can be deactivated as long as a voltage (Vn), which falls in the n-th sub-cell string (16_n) is greater than the predetermined respective voltage limit (VHG).

32. The control circuit according to claim 31, wherein the entirety of the n-1 half-bridges (44_1..44_n-1) of the cell string (14) is configured to form a total of free-wheeling diodes (40_1..40_n) of the cell string (14) of the photovoltaic module ( 10).

33. Method for controlling a photovoltaic module (10) with at least one cell strand (14),

wherein at least one cell strand (14) has n series-connected partial cell strands (16_1..16_n), where n ≥ 2 and

where, for 1≤x≤n-1 and an x-th controllable half bridge (44_x),

comprising two asynchronously switchable switching devices (46_x1, 46_x2), is configured

the method comprising the steps of:

Activating the first half-bridge (44_1) to provide a

Desired voltage (Vis) at the associated first partial cell strand (16_1), as long as a voltage (Vi) which drops in the first partial cell strand (16_1) is less than or equal to a predetermined respective voltage limit value (V-IG),

- Disabling the first half-bridge (44_1), as long as a voltage (Vi), which decreases in the first sub-cell strand (16_1), greater than the predetermined respective

Voltage limit (VIG) is, and

Activating the η-1-th half-bridge (44_n-1) for providing a setpoint voltage (Vns) at the assigned n-th partial cell string (16_n) as long as a voltage (V _n ) falling in the n-th partial cell string (16_n), is less than or equal to a predetermined respective voltage limit (VRG),

Deactivating the η-1 th half-bridge (44_n-1) as long as a voltage (Vn) falling in the nth sub-cell string (16_n) is greater than the predetermined one Voltage _limit (V _nG ).

34. A method for controlling a photovoltaic module (10) according to claim 33, wherein, for n-3 and n-e i, the method comprises the following additional steps:

- Activation of the x-th and x + 1 -th half bridge (44_x, 44_x + 1) for providing a reference voltage (V _x + 1 s) at the associated x + 1-th partial cell line (16_x + 1), as long as a voltage (Vx + i) falling in the x + 1-th sub-cell string (16_x + 1), less than or equal to a predetermined respective voltage limit

- deactivating the x-th and x + 1-th half bridge (44_x, 44_x + 1), as long as a voltage (V _x + i) falls, in the x + 1-th partial cell line (16_x + 1) is greater than the predetermined respective voltage limit (V _X + 1G).