EP2850714A2

EP2850714A2 - Assembly of a system for generating a direct current or an alternating current, and system for generating a direct current or an alternating current

Info

Publication number: EP2850714A2
Application number: EP13730100.8A
Authority: EP
Inventors: Sascha LEHRMANN; Kai FIEBER
Original assignee: juwi technologies GmbH
Current assignee: JUWI INTERNATIONAL GMBH
Priority date: 2012-05-16
Filing date: 2013-05-15
Publication date: 2015-03-25
Also published as: WO2013170958A2; WO2013170958A3; DE202013011142U1

Abstract

The invention relates to an assembly of a system for generating a direct current or an alternating current, having at least a first section and a second section, wherein the first section has at least two energy generators which are connected in series and the second section has at least one energy generator, wherein at least the energy generators of the first section generate a direct current from electromagnetic radiation, thermal radiation, fluid flows or biomass or are fuel cells which generate direct current, wherein the first section and the second section are connected in parallel to an input of a connection box and the connection box has a step-up converter with which the input DC voltage which is applied to the input of the connection box by connection to the first section and to the second section is converted into an output DC voltage which is produced at an output of the connection box, wherein the output DC voltage is higher than the input DC voltage.

Description

"Assembly of a system for generating a direct current or a

AC power and plant for generating a direct current or a

Alternating current "

The invention relates to an assembly of a system for generating a direct current or an alternating current and such a system for generating a direct current or an alternating current.

From practice, photovoltaic systems are known as one of the possible designs of a system for generating a direct current or alternating current. As one of the possible designs of such photovoltaic systems, the concept described in more detail below is known in practice: individual photovoltaic modules are connected in series and thereby combined into one strand. The length of the string (the number of photovoltaic modules in a string) is determined by the output voltage of the individual modules and the permissible input voltage range of the inverter, at whose input the DC voltage generated by the string is applied. As an embodiment of this known in practice concept, it is also known to form a plurality of strands and summarized in a parallel circuit and collect at the entrance of a junction box. If a plurality of such junction boxes are provided, which each have their own strings connected in parallel, the output currents of these junction boxes, which are often direct currents, can be fed to the input terminal field of an inverter. With the

CONFIRMATION COPY Inverters, the input currents are then converted into an alternating current. This concept known from practice is shown in FIG.

A disadvantage of photovoltaic modules is that the output voltage of the photovoltaic modules is not constant, but changes, for example due to

Heating of the photovoltaic module forming solar cells (photovoltaic cells). Other influencing factors for the output voltage of the photovoltaic module are, for example, the radiation to the module and the ambient temperature. Within a string, the individual voltages add up to the so-called string voltage, since the photovoltaic modules of the string are combined in series. By combining several strands with different strand voltage, as may result, for example, due to the manufacturing tolerances of the individual solar cells or photovoltaic modules, balancing currents can flow between the individual strands to build a common voltage level. This process is often called

Mismatching called. Frequently photovoltaic modules allow manufacturing only certain return currents, so in such interconnections fuses must be made to avoid that the respective photovoltaic module is exposed to excessive reverse current.

In the embodiment in which a plurality of junction boxes are provided, whose output current is supplied to the inverter, there is thus a situation that in an inverter having a plurality of input channels, the input voltages per channel may vary within a certain range. This results in changing operating points for the inverter. For this purpose, MPP trackers (Maximum Power Point Tracker) are frequently used in practice, which are to find the optimum operating point in each case, whereby the optimum operating point is understood as the maximum power point of the strand group. From WO 2010/002960 A1 it is known in a system for producing a

AC to provide an assembly having at least a first strand and a second strand, wherein the first strand has a plurality of series-connected photovoltaic modules and also the second strand has a plurality of series-connected photovoltaic modules. Each strand may have a terminal box, so that the strand tension of the strand is applied in each case to the connection box assigned to this strand. In a preferred embodiment, WO 2010/002960 A1 provides for assigning a terminal box to each individual photovoltaic module. In this specific embodiment, in which each individual photovoltaic module is assigned a terminal box, WO 2010/002960 A1 proposes forming the terminal box with an up-converter, which is referred to therein as a "boost module." This boost module allows it, the voltage supplied by the individual photovoltaic module, applied to the terminal box input DC voltage applied to an output of the respective, the photovoltaic module associated terminal box

To convert output DC voltage, wherein the DC output voltage is higher than the DC input voltage.

Against this background, the invention has the object to provide an assembly of a system for generating a direct current or an alternating current and to provide a system for generating a direct current or alternating current, which has a smaller number of components and thereby a lower probability of failure, low maintenance and has lower investment costs.

This object is achieved by the assembly of claim 1 and the system of FIG. Advantageous embodiments are given in the subclaims and the following description.

The invention is based on the idea of connecting at least one first strand and at least one second strand in parallel to an input of a terminal box and this terminal box with a

Up converter form, with which the voltage applied to the input of the terminal box by the interconnection with the first strand and the second strand input DC voltage is converted to a voltage applied to an output of the terminal box output DC voltage, wherein the DC output voltage is higher than the DC input voltage. This offers the

Advantage that terminal boxes configured with boosters do not need to be maintained for each power generator, for example for each photovoltaic module. There does not even have to be a junction box with one boost converter per string. It has been recognized that even when combining multiple strings in a parallel connection to the input of a boost converter junction box, the plant for generating a DC or AC current can still be operated with high efficiency.

The solution according to the invention offers the advantage of reducing the number of components. As a result, a system equipped with the assembly according to the invention for generating a direct current or an alternating current can be built with lower investment costs.

The assembly according to the invention comprises at least a first strand and a second strand, which are connected in parallel to an input of a junction box with a boost converter. Within the scope of the invention it is It is also possible to connect more than two strings in parallel to the input of the connection box. For example, more than three, more than five, more than ten, more than 20, more than 50 and particularly preferably more than 100 strands can be connected in parallel to the input of a terminal box while still a sufficiently high efficiency of the entire system for Generating a direct current can be maintained. The number of strands to be provided in parallel is limited, in particular, by the maximum power of the boost converter. In the assembly according to the invention, the first strand has at least two in

Series connected to each other power generator. To achieve the advantages of the invention, it is only necessary that the second strand has at least one energy generator. In a preferred embodiment, however, the second strand also has at least two energy producers connected in series with one another. It is also conceivable that a power generator in a strand through the

Parallel connection of two or more sub-power generator is formed. For example, a first energy generator in the first strand can be formed by connecting two sub-energy generators in parallel, wherein the first energy generator thus formed in the first strand can be connected in series with a second energy generator, which in turn is formed by connecting two or more sub-generators in parallel ,

In a preferred embodiment, the first strand and / or the second strand more than two series-connected energy producers, namely preferably more than three, more than four, more than five, more than ten, more than 15 or more preferably more than 20 in series with each other connected energy producers. In particular, the number of power generators connected in series will be limited by a maximum system voltage possibly selected for the system and the voltage supplied in the train per power generator. For example, at a maximum of 1000VDC

System voltage 24 modules per strand (polycrystalline, 60 cells) or 18 modules per strand (monocrystalline, 60 cells) may be provided. Changing the maximum desired system voltage, for example, to 1500VDC, so more modules per strand are conceivable.

The energy generators of the first strand are designed to generate a direct current from electromagnetic radiation (for example as a photovoltaic module), heat radiation (for example via solar thermal energy), fluid flows (for example wind or water power) or biomass. In particular, the energy producers connected in series in the first string are preferably selected from the group of those listed below, in particular as energy producers selected components selected photovoltaic module, solar thermal module with connected turbine for generating an alternating current and rectifier for generating a direct current, wind turbine or combustion boiler for burning biomass and heating a fluid with downstream turbine for generating an alternating current and attached rectifier for generating a direct current.

Likewise, a power generator of the first train may be a fuel cell that generates DC power.

In a preferred embodiment, the energy producers in the first strand of the same type (for example, all photovoltaic modules in contrast to a mixture of, for example, photovoltaic modules and fuel cells in one strand), particularly preferably of the same design (for example, all photovoltaic modules with 60 polycrystalline cells) within each type. However, it is also conceivable to provide energy generators of different types within the first strand, for example a first energy generator which generates direct current from electromagnetic radiation, and a second energy generator which is designed as a fuel cell which generates direct current.

In a preferred embodiment, the at least one energy generator in the second strand is also an energy generator, which consists of electromagnetic radiation,

Heat radiation, fluid flows or biomass generated by a direct current or a fuel cell that generates direct current. In a particularly preferred embodiment, all energy producers in an assembly of the same type, particularly preferably photovoltaic modules and very particularly preferably identically constructed photovoltaic modules.

In a preferred embodiment of the embodiment described in more detail above, in which a power generator is formed by parallel connection of two or more sub-power generators, the respective sub-power generator is also a power generator, which consists of electromagnetic radiation,

Heat radiation, fluid flows or biomass generated by a direct current or a fuel cell that generates direct current.

The up-converter provided in the terminal box, which may also be referred to as boost converter or boost-converter or step-up converter, is a DC-DC converter in which the magnitude of the output voltage is greater than the magnitude of the input voltage. For example, it may be constructed such that an inductance is connected in series with a freewheeling diode, behind which a charging capacitor adds up the output voltage. A coil is connected through a switch, typically a semiconductor switch, such as an IGBT (insulated-gate bipolar transistor; insulated gate electrode) or a MOSFET (metal-oxide-semiconductor field-effect transistor) connected to ground. When switching the input voltage drops on the coil, the current through the coil and thus the stored energy in the magnetic field increases. When the switch is opened again, the coil tries to maintain the current flow. The voltage at the secondary end rises very quickly until it exceeds the voltage applied to the capacitor and opens the diode. The current continues to flow unchanged in the first moment and continues to charge the capacitor. The magnetic field is thereby reduced and releases its energy by driving the current through the diode into the charging capacitor and to the load. Similarly, activation by means of a VJET

(Vertical junction field effect transistor) conceivable.

In a preferred embodiment, the boost converter provides a constant DC output voltage. The boost converter may particularly preferably permanently provide a constant DC output voltage, for example, for the entire operating time of the assembly, for example when designed with photovoltaic modules as energy producers for the entire time in which the photovoltaic modules are irradiated with electromagnetic radiation. However, it is also conceivable for the boost converter to be a constant only for a predetermined time period (or determined by measuring ambient or plant parameters)

DC output voltage supplies and for another period of time another (constant at the other level) output DC voltage generated.

The boost converter is in particular designed such that the output DC voltage that it delivers is adjustable. The amount of as

Output DC voltage output from the jack voltage can be adjusted for example via the control of the switch, in particular by changing the frequency of the switching operations. In a preferred embodiment, the boost converter is designed in such a way that it supplies a DC output voltage which is constant for at least fixed periods of time even when the input DC voltage fluctuates. The time periods may be longer than one second, preferably longer than one minute, preferably more than one hour. By driving the switches, in particular their switching frequency can be achieved that the boost converter supplies even with fluctuating input DC voltage at least for a fixed time periods constant DC output voltage.

In a preferred embodiment, the boost converter is configured to provide low voltage power transfer at voltages of 500

VDC up to 1500 VDC on the input side and voltages on the output side from 600 VDC up to 1500 VDC unipolar or 600 VDC to 3000 VDC with bipolar connection type. In an alternative embodiment, the boost converter is designed such that it provides input DC voltages of greater than 1500 VDC in the unipolar or bipolar type of connection in the medium-voltage range at voltages of 500 VDC to 1500 VDC on the input side.

In a preferred embodiment, a limiter, for example in the form of a component, may be connected downstream of the boost converter with a chopper control, which lowers the output DC voltage supplied by the boost converter to a lower level. In a chopper control (impulse control) is the

Output DC voltage of the boost converter chopped by electronic switches (thyristor pulse controller, DC controller, transistor or IGBTSchalter) and the mean value of the voltage varies (comparable to a pulse width modulation (PWM) by means of the duty cycle). To achieve the desired values (duty cycle, voltage, speed or power), either the

Clock frequency or the duty cycle changed.

In a preferred embodiment, an electronic component of the junction box, which may be coupled to the boost converter, is responsible for controlling the voltage. Primarily, in this embodiment, a

Regulation of the voltage, if a certain limit value of the voltage or voltage change is exceeded, there is a limitation of the current and a "chopper" with the above-described chopper control.

In a preferred embodiment, a component with a chopper control can also be connected upstream of the up-converter. In such a component with a chopper control, a current can be generated, which flows back in the direction of the energy generator. This can be used, for example, to energize photovoltaic modules designed energy generator to a

Defrosting function of the same (snow load minimization) to generate. Likewise, components with chopper control can be provided for each individual strand, for example at the location where the ends of the strand are guided into the housing of the connection box.

Additionally or alternatively, the boost converter itself is designed such that it can compensate for an overvoltage, in particular preferably can compensate for an overvoltage within a tolerance band. The tolerance band may, for example, have a width of 0V to 100V, and more preferably a width of 0V to 700V. In a preferred embodiment of the invention described in more detail below, the inventive system Assembly, the tolerance band is determined depending on the system parameters. If, for example, an inverter is provided within the plant, to which the current discharged from the terminal box is supplied, the tolerance band can be set to the ability of the inverter to absorb fluctuating input voltages. Likewise, the adjustable tolerance band can be limited by the semiconductor material of the switches in the up-converter. In particular, this balancing of the overvoltage is realized by alternating the activation of the power semiconductors (electronic switches) in the up-converter, whereby a lowering or targeted increase of the output voltage is achieved.

In a preferred embodiment, the terminal box has a cooling. Particularly preferably, the connection box may have an exposed heat sink facing the environment of the connection box. Such a heat sink is suitable for dissipating the power loss, so this in the

Up-converter arises. The cooling can be convection cooling. Likewise, the cooling can be carried out in conjunction with a heat exchanger, for example a liquid-conducting heat exchanger or even an air / air heat exchanger. However, the cooling can also be a PWM-controlled, forced cooling or else a forced cooling with discrete voltage levels. For a forced cooling, it is particularly preferred to use a fan which can generate a fluid flow, preferably an air flow, flowing over a heat sink. By means of the pulse width modulation (PWM) control, the speed of such a fan can preferably be adjusted continuously. Similarly, the fan can discrete speed levels (discrete voltage levels, which by the

Electric motor of the fan converted to discrete speed levels lead).

Additionally or alternatively, the cooling of the connection box can be brought about by the fact that the heat input is reduced in the terminal box. It is conceivable that a power loss occurs in the boost converter. It is also conceivable that this power loss is converted by the up-converter or other components in the junction box into heat. In a preferred embodiment, the heat input into the connection box can now be reduced, in which the accumulation of the heat caused by the reduction of the power loss is reduced. This can be done, for example, by reducing the power of the boost converter, or possibly even shutting off the boost converter, so that the assembly does not temporarily provide a DC output voltage. The regulation of the power of the up-converter can be carried out in particular preferably by means of a pulse width modulation (PWM) control of the switches in the up-converter. Particularly preferably, a temperature sensor is provided on and / or in the connection box. Particularly preferably, in addition to the temperature sensor, a control is provided which activates cooling and / or reduces the power of the boost converter and / or switches off the boost converter when a predetermined temperature level is reached.

In a preferred embodiment, the assembly according to the invention has a measuring system which carries out measurements at at least two measuring points. The measurements can be recorded in a memory and / or evaluated in an evaluation unit and / or via suitable means, such as lines, but also

Radio communications are forwarded to out-of-assembly receivers. For example, the measurement system may measure temperatures, such as the temperatures of individual photovoltaic modules (if used as energy generators), or measure the temperature in a housing of the junction box. Likewise, the measurement system may acquire performance data of the assembly, such as the current in a string or the voltage across a string or, for example, the current flow in the boost converter and the voltage at the input of the boost converter and / or the current flow from the boost converter and the voltage at the output of the boost converter , Parts of the measuring system, such as a measuring board can be integrated into the housing of the terminal box.

In a preferred embodiment, the assembly according to the invention has a control that carries out control interventions on actuators of the assembly based on the measurements of the measuring system. For example, the up-converter may be preceded by an MPP tracking module which determines the optimum operating point of the

Up-converter seeks. To do this, the MPP tracking module intervenes on an actuator, such as an adjustable resistor provided in the terminal box, varies resistance, and iteratively and iteratively checks iteratively which position of the actuator provides the best performance of the boost converter. The MPP tracking module can also be configured in such a way that the optimum operating point is sought by changing the setting of the up-converter, for example by controlling the switches of the up-converter, and the MPP tracking module is designed only as an evaluation unit which measures the power of the up-converter With a first set of setting checks, the boost converter's performance checks with a different set of settings, and finally the

Choose set of setting that offers the greater performance.,

In a preferred embodiment, either at the input of the up-converter (ie after the parallel connection of the strings) or at the ends of the strings, shortly before their parallel connection, a DC contactor is integrated in the terminal box. As a result, an overcurrent protection device can be provided, which in combination with a Current measurement can cause the DC contactor triggers from a pre-defined variable variable current on the DC contactor. The tripping characteristic (tripping characteristic) can be determined and adjusted by an electronic circuit, or realized by software in a control unit. In a preferred embodiment, the DC contactor is also controllable from outside the assembly according to the invention, for example via a cable or via radio. Particularly preferably, the triggering of the DC contactor can also be formed by a key switch or a pressure switch. The terminal box may in a preferred embodiment, a metallic

Have housing or a partially metallic housing executed. A metallic or partially metallic housing can serve to take over a cooling capacity. The housing may, in a preferred embodiment, comprise a body in which the electronics are housed and a pedestal on which the carcass stands. It is also possible that the housing is suspended, for example, mounted on a wall.

In a preferred embodiment, the terminal box on quick connectors, such as plugs, on which the ends of the strands can be connected, or to which an output power can be connected. It is also conceivable to make the connection of the cable to the terminal box by means of a combination of bolt and cable lug. The bolt is screwed into a live thread and transmits the current through the bolt and the cable lug at the end of the cable to the cable. Likewise, terminals of the connection box can be terminal blocks (V

Terminals, cage clamps) may be provided.

Preferably, the parallel connection of the strands takes place within the junction box. For this purpose, the terminal box may have a plurality of inputs, for example. Quick connections, into which the ends of the strands are inserted, wherein the quick connectors are connected in the terminal box so that there is a parallel connection of the strands.

In a preferred embodiment, the assembly is designed such that individual strands can be removed from the parallel circuit, for example by opening switches provided in the strands.

In a preferred embodiment, the boost converter is independent and does not require any information or communications between the inverter and the boost converter. The inventive system for generating a direct current or an alternating current know at least one first assembly according to the invention and at least one second inventive assembly and a DC bus system, wherein the output of the terminal box of the first module is connected to the DC bus system and the output of

Terminal box of the second module is connected to the DC bus system.

In a preferred embodiment, the DC bus system has a constant voltage. With the help of the up-converter of the junction boxes, a constant output voltage can be generated at the terminal boxes, which is equal to the voltage of the DC bus system selected as constant in a preferred embodiment. In such an embodiment of a constant voltage DC bus system, an inverter connected to the DC bus system may be a constant one

Maintained tension and can work in an optimal operating point.

In an embodiment with an inverter connected to the DC bus system, the voltage at the input of, or the inverter and the output voltage at the terminal boxes can be detected, compared and possibly readjusted to keep the voltage of the DC bus system at the inverter input constant ,

In a preferred embodiment, at least one inverter is connected to the DC bus system to which DC power is supplied from the DC bus system via a terminal and generates an AC current therefrom. In a preferred embodiment, multiple inverters may be connected to the DC bus system. In a supplementary or alternative embodiment may be attached to the

DC bus system connected to a terminal to which a DC load can be connected. In this way, the system according to the invention can be used to generate a direct current, namely when the DC load is connected to this terminal. As a direct current consumer, an energy storage medium is understood.

For example, a battery can be connected to this port.

In a preferred embodiment, the DC bus system is arranged outside a housing, in particular arranged outside a housing of a terminal box. In a preferred embodiment, the

DC bus system used to connect a junction box with a DC consumers and / or an inverter to connect, which are arranged in a different housing and which are particularly preferably spaced from the housing of the junction box. In a preferred embodiment, the length of at least one line of the DC bus system is longer than the length, width and / or height of a terminal box, and more preferably longer than 0.5m, more preferably longer than 1m, more preferably longer than 5m and above all preferably longer than 10m.

In a preferred embodiment, the DC bus system connects a junction box and an inverter or DC load if the inverter or DC load is more than 1m, more preferably more than 5m, more preferably more than 10m and most preferably more than 20m of the Terminal box are removed.

In a preferred embodiment, the length of the shortest connection cable of the power generator closest to the terminal box to the terminal box is shorter than the length of the shortest line forming part of the DC bus system.

Especially when using a DC bus system over long distances from the terminal box to the inverter or a DC load can be realized the advantages that the transmission losses are less with DC lines than with AC acted upon lines.

In a preferred embodiment, the length of the shortest connecting cable of the energy generator closest to the connection box with the connection box is shorter than 5 m, in particular equal to or shorter than 3 m, particularly preferably less than 1 m. The connection cable is understood in particular to be the cable which leaves the energy generator, for example the photovoltaic module, and extends to a connection to the connection box. Its length is the length from leaving the power generator, eg. From leaving the housing of the power generator to the entrance into the junction box or a connection box upstream of any collection point where the strands are connected in parallel before entering the junction box. Such a collection point is also understood as "entry into the connection box" or "connection to the connection box" for the purpose of simplifying the description. As a connection to the terminal box is also understood both a provided on the housing of the terminal box connector to which a strand is connected, as well as a passage opening for a cable of the strand understood. In its course from the power generator to the connection box, the cable may have intermediate plugs. For example, to form the connection cable a cable leading out of the power generator having a plug is connected to a cable leading out of the terminal box and having a plug. The line thus formed is also understood as a connection cable. This is done against the background of the advantage achieved with this preferred embodiment: In the preferred embodiment, it is attempted to place the junction box and, in particular, the boost converter provided therein as close as possible to the power generators connected in series. If the boost converter is used to generate a constant DC output voltage, the advantages associated with this embodiment are realized as close as possible to the string.

In a preferred embodiment, the string of series-connected power generators may be configured to extend in a direction away from the terminal box from a starting point near the terminal box. The end of the strand at the starting point is connected to the junction box, usually via the shortest connecting cable. In such an embodiment, a cable is provided at the end of the strand remote from the junction box, which is returned to the junction box to complete the series connection. In a preferred embodiment, this returning cable has a length of more than 30 meters, more preferably more than 40 meters. In a preferred embodiment, this returning cable has a length of less than 190 meters, more preferably less than 180 meters.

In an alternative embodiment, the string of series-connected power generator can be designed so that it from a terminal box near starting point in the manner of a loop, for example, in the form of two mutually parallel sub-strands (leading sub-strand, trailing sub-strand) to a End point extends, which is also located near the terminal box. Both the end of the strand at the starting point and the end of the strand at the end point are preferably connected to each other with approximately equal short connecting cables, preferably with connecting cables of the length of the shortest connecting cable described in detail above.

In a preferred embodiment, the DC bus system is designed as a daisy chain, particularly preferably as a daisy chain in the ring. A "daisy chain" refers to a number of hardware components which are connected in series, namely in the form of a bus system, whereby a first component, here a first connection box, is directly via the bus with the inverter or the DC load The other components, such as the other inverters or DC consumers or The other terminal boxes are also connected to their predecessors (series connection principle), so that a chain is created (therefore "daisy-chain") .The signal to and from one component now goes through its predecessor to the first inverter, or until the first direct current By using a daisy-chain structure, it is possible to redirect power flows (currents) .Through a DC switching point coupled to the electronic components of the boost converter, the ring can be interrupted in a defined manner and a faulty segment, eg a cable, can be disconnected The DC bus also allows the entire terminal box to be disconnected from the DC bus

DC bus system. On site, the DC voltage switching point can also be used for activation during maintenance work. The DC voltage switching point is electronically protected against automatic restart. When connecting several terminal boxes and at least one inverter in a version of the DC bus as a daisy chain, the system connected in this way may be able to remove faulty line segments or terminal boxes from the system (to be disconnected from the DC bus). This can be implemented in particular preferably as follows: It can in normal operation, before the boost cycle, so before the conductive phase of the power semiconductor switch of the boost converter begins, ie in the dead time (off) an insulation measurement (voltage QC + to ground, DC against Earth). Since the dead time (time-out) of the power semiconductor switch of the boost converter is often about 170 [is and for an insulation measurement usually 3 to 4 ε are needed, the implementation of such a measurement is not critical. The measurement result of the insulation measurement can be reported back to an evaluation unit. This allows insulation faults to be detected on the DC cables (input and output side of the terminal box). Monitoring the output current of the boost converter provides detection (overshoot) of limit and threshold values as well as the change (increase) in the current. The integrated controller can now be based on this

Values change the control within the up-converter (variation of the PWM). Thus, the output current is automatically limited to a set maximum value. If this maximum value is reached for a longer time (fixed time x), the boost converter is switched off and the connection box is disconnected on the DC output side.

A disconnect function on the DC side can be achieved by DC switches in each path (DC +, DC-, DC "0", etc.). These are preferably designed as motorized DC switches or DC circuit breakers with a switching capacity of up to 500 A. To control these switching points, the control electronics of the

Boost unit (boost converter) via appropriately sized switching outputs feature. These switching outputs can be, for example, semiconductor switches or relays.

In order to realize the function of the separation of faulty line segments of the DC bus, a corresponding arrangement of the DC switching elements is to be selected. This is as follows: In each path and here for each connection point (line), such a DC switching point is to be integrated. All connection points of each path must be connected to the jumpers to the jumpers and to the corresponding path of the push-up unit.

In a preferred embodiment, the voltage and the current are detected at each terminal box of the DC bus system. With a measuring system, furthermore, the components of the string monitoring can be read out, the data can be evaluated and forwarded. For this purpose, an internal communication bus, e.g. RS485 or CAN, to which the

Measuring system can be connected.

The DC bus system allows the generation-dependent switching on / off of inverters, if several inverters are provided in the DC bus system. Thus, the inverters can be operated at their (optimum) operating points for the majority of the time - the efficiency of the system increases. The individual terminal boxes can also be removed from the bus. In a preferred embodiment, the assembly, or the system is modular. Multiple in the assembly, or provided in the system components are identical.

In a preferred embodiment, the up-converter of the system according to the invention is designed such that it interleaved a two-channel boost

Wiring unipolar performs. Likewise, the boost converter can be designed such that it carries out a two-channel boosting by means of bipolar interconnection of the generating units. In a preferred embodiment of the system according to the invention are individual

Terminal boxes can be separated from the DC bus, for example by means of switches provided on the output side of the terminal boxes. In this way, a malfunctioning terminal box can be removed from the system. The provided in a preferred embodiment MPP tracking with the

Up-converter upstream MPP tracking module in terms of the best The operating point of the boost converter, combined with a boost converter boost, resulting in a constant output DC voltage on the boost converter, has the advantage of optimizing power generation at each boost converter and already feeding the optimally achievable DC power into the bus. This can be done at a

Embodiment of the system according to the invention with an inverter, for example, be waived to make an MPP tracking respect. An optimal operating point of the inverter. In a preferred embodiment, the constant output voltage of the boost converter and thus of the junction box described by the variable specification of a desired value is adjustable. Thus, an adjustment of the output voltage is given to the downstream inverter. Due to the constant voltage and its adjustability, the inverter can be operated in a fixed constant operating point. The voltage value of this inverter operating point can be taken from characteristics of the inverter manufacturer.

The embodiment of the system according to the invention with MPP tracking on the terminal boxes offers the possibility of shifting the MPP tracking from the inverter to the level of the terminal box or individual strings. This results in a much higher efficiency and the influence of shading, z. B. by

Cloud train and different module parameters are minimized. The optimum operating point for each terminal box is chosen. The MPP tracking (finding the operating point) can be done much faster than in a central inverter. In the prior art, PWM controls are often used in central inverters to slowly perform MPP tracking.

Frequently, these frequencies are 3 kHz to 17 kHz. Performing an MPP tracking on the connection box could, for example, be done with faster PWM control, for example those operating at 10 kHz to 100 kHz. In addition, MPP tracking in the boost converter is expected to have a lower voltage swing range. Therefore, the MPP algorithm must perform fewer iterative steps to find the optimum operating point at the time. This also allows a higher speed of tracking implement. In the inverter, this functionality can be omitted, this then only regulates to a fixed input value.

In a preferred embodiment, the system has a control in which an algorithm for line length detection is implemented for the automatic regulation of the output voltage level to the limit voltage of the inverter. The following procedure can be followed: During commissioning of the system, the cable length between terminal box and

Inverter is automatically detected by applying various pulses (bursts) to the Be given line section. These pulses are reflected at the line end (inverter) and run back to the starting point (connection box). The line length can now be determined from the propagation times of the pulses. If the values of the parameters line cross section and conductor material are specified for the algorithm, the expected value can be determined from these and the line length

Voltage drop on the line section to be determined depending on the current. The output voltage of the boost converter (boost unit) can now be readjusted in order to provide the desired constant voltage at the inverter so that the current-dependent voltage difference determined in this way can be determined.

In a preferred embodiment, the system has a complete monitoring of the system with reference to VDE0100-712 (DIN IEC 60364-7-7 2), so that no line protection is required on the output side. In a preferred embodiment, wherein the up-converter a component with

Chopper function is upstream or downstream, the maximum phase voltage may temporarily exceed the voltage of the DC bus system, as the combined up-converter with chopper function holds the strand voltage. In this embodiment, a simultaneously integrated, secondary control on the current limit the maximum supply current in the DC bus system and can thus detect and limit insulation and short circuit errors.

The inverter can be designed such that it separates away a back-energized line in the event of a fault.

In a preferred embodiment, the assembly according to the invention, or the system according to the invention is provided at least one electronic or electromechanical separation unit. Particularly preferred, as far as these elements are provided in the respective embodiment of the invention, the element for separating a junction box from the DC voltage

Bus system and / or the element for separating an inverter or a DC consumer designed as an electronic or electromechanical separation unit. In a preferred embodiment, the assembly according to the invention, or the system according to the invention is a communication interface for maintenance and data logging provided. The communication interface for maintenance and data logging can be provided on a component of the assembly according to the invention, preferably the connection box. Likewise, the communication interface for maintenance and data logging can be provided, for example, in the area of the inverter. The communication interface for maintenance and data logging is particularly preferably connected to a communication network of the system that can be read at the communication interface for maintenance and data logging data, which are read by measuring points that have been detected at different measuring locations of the system. The provision of only one communication interface for maintenance and data logging, preferably at an easily accessible location of the system according to the invention, makes it possible to carry out simple maintenance, for example the installation of software updates, and to carry out simple data logging.

In a preferred embodiment, one or the above-described communication interface is designed for remote action, for example by incorporating a telecommunication connection. In this way, the release of certain modules, or the entire system, but also the installation of updates and the data logging done from outside.

In a preferred embodiment, the assembly according to the invention or the system according to the invention has a communication interface for connecting a visual service unit, such as a monitor. This visual service unit may be useful, for example, in the maintenance of the plant or in the commissioning of the plant.

In a preferred embodiment, the assembly according to the invention and / or the system according to the invention comprises means for the electronic activation and locking of the assembly per se, of individual components of the assembly, such as a string or the system. These means are preferably triggered from the outside, for example in an accident or at the beginning of a maintenance cycle.

In a preferred embodiment, the assembly or the system according to the invention has a display unit, preferably an externally visible display unit, which has one or more of the following properties:

, Optical visualization operating state

, Output of input and output parameters

, Display of the current system voltages, currents

, Display of MPP parameters and states

, Display of errors, warnings and alarms The invention will be explained in more detail with reference to a drawing showing only embodiments of the invention. Show:

1 is a schematic representation of the known from the prior art topology of photovoltaic systems,

Fig. 2 is a schematic representation of a first embodiment of the inventive system for generating an alternating current, Fig. 3 is a schematic representation of a second embodiment of a

Plant for generating an alternating current according to the invention,

Fig. 4 is a schematic representation of a measured value at a

Bus subscriber within the system according to the invention for generating an alternating current according to the invention

Fig. 5 is a schematic representation of a unipolar interconnection of

Terminal box with an inverter, Fig. 6a), b) are schematic representations of two embodiments of a bipolar interconnection of the junction box with an inverter,

Fig. 7 is a schematic representation of DC switching points on the

Output side of two terminal boxes,

Fig. 8 a), b), c) d) is a perspective, schematic view from the front on a

Terminal box, a perspective, schematic view from the rear of a terminal box, a first embodiment of a connection variant for a DC output in a schematic, disassembled view and a second embodiment of a connection variant for a DC output,

Fig. 9 a), b), c) is a perspective, schematic view from the front of another

Embodiment of a terminal box, a perspective, schematic view from the rear of this embodiment and a side view of this embodiment and

10 a), b) is a perspective, schematic view from the front of a hanging mounted further embodiment of a connection box, a perspective and a side view of this embodiment.

The topology of a photovoltaic system known from practice, shown in FIG. 1, has four strands 1, 2, 3, 4. Each strand 1, 2, 3, 4 has three series-connected to each other power generator 5, 6, 7 in the form of photovoltaic modules. The strand 1 and the strand 2 are connected in parallel to a terminal box 8. The strand 3, and the strand 4 are connected in parallel to a junction box 9. The terminal box 8 has a DC main cable 10, which is fed to a first input terminals of an input terminal field of the inverter 11.

The connection box 9 has a second direct current main cable 12, which is led to a further input terminal of the input terminal field of the inverter 11. The inverter generates an alternating current from the direct currents supplied to it.

In the embodiment of the inventive system for generating an alternating current shown in FIG. 2, a first strand 21 and a second strand 22 are provided, as well as a third strand 23. The strands 21, 22, 23 have energy generators which are made of electromagnetic radiation, namely solar rays to generate a direct current, namely photovoltaic modules 25, 26, 27 the

Photovoltaic modules 25, 26, 27 of the first strand are connected in series with each other. Likewise, the photovoltaic modules 25, 26, 27 of the second strand 22 are connected in series and the photovoltaic modules 25, 26, 27 of the third strand 23 connected in series. The first strand 21 and the second strand 22 are connected in parallel to an input of a connection box 28. Of the

Strand 23 is connected to the input of a connection box 29. The connection box 28 has an up-converter 33. The terminal box 29 also has an up-converter 34. The embodiment shown in FIG. 2 has a DC bus system 35. To the DC bus system 35 inverters 36, 37 are connected and the terminal boxes 28, 29th

The embodiment of the system according to the invention shown in Fig. 3 shows the embodiments of the DC bus system as a daisy chain. The illustrated

Embodiment of the inventive system for generating an alternating current has a first strand 41 and a second strand 42 and a third strand 43 and a fourth strand 44. The strands 41, 42, 43, 44 have energy generators, which can generate direct current from electromagnetic radiation, namely solar rays, namely the photovoltaic modules 45, 46, 47 of the first strand 41 are connected in series with each other. Likewise, the photovoltaic Modules 45, 46, 47 of the second strand 42 connected in series and the photovoltaic modules 45, 46, 47 of the third strand 43 connected in series and the photovoltaic modules 45, 46, 47 of the fourth strand 44 connected in series. The first strand 41 and the second strand 42 are connected in parallel to an input of a connection box 48. The third strand 43 and the fourth strand 44 are connected in parallel to an input of a connection box 49. The connection box 48 has an up-converter 53. The terminal box 49 also has an up-converter 54. The embodiment shown in FIG. 3 has a DC bus system 55, which is designed as a daisy-chain. To the DC bus system 55 inverters 56, 57 are connected and the junction boxes 48, 49th

Fig. 4 shows that the system according to the invention can be provided with a system for measured value detection. This is for example on the

Inverter 56, a measuring unit 60 for detecting current and voltage provided. Likewise, a measuring device 61 for detecting current and voltage is provided in the connection box 53. Via a communication line 62, the measured values thus acquired can be supplied to an evaluation unit (not shown).

5 shows a possibility of a unipolar interconnection of a connection box 100 with an inverter 101. The connection box 100 has an up-converter 102. The boost converter 102 has a positive pole output and a negative pole output of the junction box 100 within the junction box

100 connected (via lines not shown). The positive pole output of the connection box 100 is connected to a positive pole input of the inverter 101 via a line 103. The negative pole output of the connection box 100 is connected to a negative pole input of the inverter 101 via a line 104.

FIG. 6 a) shows a possibility of a bipolar interconnection of a connection box 110 with an inverter 111. The connection box 110 has an up-converter 112. The boost converter 102 is connected to a positive pole output, a ground output and a negative pole output of the junction box 100 within the junction box 100 (via lines not shown).

The positive pole output of the terminal box 110 is connected to a positive pole input of the inverter 111 via a line 113. The ground output of the terminal box 110 is connected to a ground input of the inverter 111 via a line 115. The negative pole output of the connection box 110 is connected to a negative pole input of the inverter 1 11 via a line 4. FIG. 6 b) shows a further possibility of bipolar shading of a connection box 120 with an inverter 121. The connection box 120 has an up-converter 122. The boost converter 122 is connected to a positive pole output, a ground output, and a negative pole output of the junction box 120 within the junction box 120 (not shown)

Cables). The positive pole output of the connection box 120 is connected to a positive pole input of the inverter 121 via a line 123. The ground output of junction box 120 is grounded. The ground input of the inverter 121 is grounded. The negative pole output of the connection box 120 is connected to a negative pole input of the inverter 121 via a line 124.

FIG. 7 shows a possibility of providing switching points 130, 131, 132 at the outputs of the connection box 133. The connection box 133 has an up-converter 134. This has a positive pole output, a ground output and a negative pole output. The positive pole output is connected via a cable 135 to an internal busbar and above with parallel outgoing switches 131, 141. The ground output is connected via a cable 137 to an internal busbar and above with parallel outgoing switches 132, 142. The negative pole output is via a cable 139 with an internal

Busbar and above with parallel outgoing, output-side switches 133, 143 connected. In the operating situation illustrated in FIG. 7, the switches 131, 132, 133, 141, 142, 143 are opened. If the switches 131, 132, 133, 141, 142, 143 are connected, then the respectively assigned switch 131, 132, 133 respectively connects one end of a direct current cable 144, 145, 146, each having one pole (positive pole output, ground connection).

Output, negative pole output). Furthermore, each associated switch 141, 142, 143 in the closed state connects one end of a DC cable 147, 148, 149, each with a pole (positive-pole output, ground output, negative pole output). FIG. 7 further shows that the system has a further connection box 150, which is constructed in a comparable manner to the connection box 130. In each case another end of the

DC cable 147, 148, 149 can be connected via the switches 151, 152, 153 to the respective internal busbar of the junction box 150.

Fig. 8 a) shows a first connection variant of a DC cable to a DC output of a junction box 160. The in Fig. 8a) in a

An exploded view of the connection variant components include a bolt 161, the DC cable 162, a lug 163 attached to the DC cable 162, and a threaded bore 164. The threaded bore 164 represents a positive pole, the ground, or negative pole of the DC output of the junction box 160. The bolt 161 will through the opening of the

Lug 163 out and screwed into the threaded hole 164 and connects thus conducting the threaded hole 164 with the DC cable 162. For the other poles, or the mass of the DC output of the junction box 160 may be provided such other connections. Fig. 8 b) shows a second connection variant for DC cables to a

DC output of the terminal box 160. For this purpose, the terminal box 160 terminal blocks 165, 166, for example, cage or V-terminals. For example, the positive potential is applied to the terminal block 165 and the negative potential of the terminal box 160 to the terminal block 166. A first DC cable 167 is connected to the terminal 165, a second

DC cable 168 clamped to the terminal block 166.

Fig. 8 c) shows the front of the housing of an embodiment of the terminal box 160. This housing has a base 170, with which it stands on the floor. On the base 170 of the body 171 of the terminal box 160 sits.

The body 171 has a hinged door 172 on one side. In the door a display 173 is integrated.

FIG. 8 d) shows the rear side of the housing of the connection box 160. There it can be seen that the body 171 has a heat sink 174 on its rear side.

Furthermore, it can be seen from FIG. 8 d) that the DC cables, for example the DC cables 167, 168, can be continued underground from the terminal box 160. Fig. 9 a) shows the front side of the housing of an embodiment of the

Terminal box 180. This housing has a base 181 with which it stands on the floor. The body 182 of the connection box 180 is seated on the base 181. The body 182 has a double-leaf door 183. A display 184 is integrated in a door leaf.

9 b) shows the rear side of the housing of the connection box 180. There it can be seen that the body 182 has a heat sink 185 on its rear side.

Fig. 9 c) shows the side of the housing of the junction box 180. It can be seen four openings 186 in the housing. These serve for example as

DC voltage inputs for the terminal box. For example, on the upper two inputs, the plus and the minus end of a first strand and on the lower two inputs, the plus and the minus end of a second strand are placed. The unipolar ends of the strings are connected in the terminal box, so that there is a parallel connection of the strands at the entrance of the terminal box. 10 a) shows the front side of the housing of a wall-mounted embodiment of the connection box 190. The housing has a double-leaf door 191. A display 192 is integrated in a door leaf.

Fig. 10 b) shows the side of the housing of the junction box 190. It can be seen four openings 191 in the housing. These serve, for example, as DC voltage inputs for the terminal box. For example, on the upper two inputs, the plus and the minus end of a first strand and on the lower two inputs, the plus and the minus end of a second strand are placed. The unipolar ends of the strings are connected in the terminal box, so that there is a parallel connection of the strands at the entrance of the terminal box. Furthermore, you can see the wall bracket 192 of the housing.

Claims

"Claims"

An assembly of a plant for generating a direct current or an alternating current having at least a first strand and a second strand, wherein the first strand has at least two series-connected energy producers and the second strand comprises at least one energy generator, wherein at least the energy generator of the first strand of electromagnetic Radiation, heat radiation, fluid flows or biomass generate a direct current or fuel cells that generate direct current, wherein the first strand and the second strand are connected in parallel to an input of a terminal box and the terminal box has an up-converter, with those at the entrance of the terminal box is converted by the connection with the first strand and the second strand applied DC input voltage to a voltage applied to an output of the terminal box constant DC output voltage, wherein the DC output voltage is higher t as the DC input voltage.

An assembly according to claim 1, characterized in that the second strand has at least two series-connected energy producers and the energy generator of the second strand of electromagnetic radiation, heat radiation, fluid flows or biomass generate a direct current or fuel cells that generate direct current.

An assembly according to claim 1 or 2, characterized in that the connection box with boost converter can correct an overvoltage.

System for generating a direct current or an alternating current with at least one first subassembly, which is designed as an assembly according to one of claims 1 to 3, and a second subassembly, which is designed as an assembly according to one of claims 1 to 3, and with a DC voltage Bus system, wherein the output of the terminal box of the first module is connected to the DC bus system and the output of the terminal box of the second module is connected to the DC bus system.

Installation according to claim 4, characterized in that an inverter is connected to the DC bus system, which is supplied via a terminal DC power from the DC bus system and generates an AC therefrom. Installation according to claim 4 or 5, characterized in that a connection is connected to the DC bus system, can be connected to the DC load.

Installation according to one of claims 4 to 6, characterized in that the DC bus system is designed as a daisy chain.