Photovoltaic installation for feeding an electric grid, and central control and monitoring device for a photovoltaic installation

p0001description

p0002Photovoltaic system for feeding in an electrical network and central control and monitoring unit for photovoltaic tai plant

p0003The invention relates to a photovoltaic system for feeding in an electrical network, especially in a public power grid, with several solar inverters, chen to wave ever a photovoltaic generator is connected, the

p0004Solar inverters are connected via a communications data technology with each other and where one also connected to the communication central control and monitoring unit to control and monitor the connected solar is ter provided.

p0005The invention relates to a central control and monitoring unit for such a photovoltaic system.

p0006ltaikanlagen Photov serve the supply of electric current in an electrical network, such as voltage grid in a 1-phase 50Hz / 230V-voltage network or in a 3-phase 50Hz / 400V voltage as a power supply company. Given by photovoltaic systems may include one or more photovoltaic generators, where a photovoltaic generator can consist of one or more solar modules, which in turn interconnected or which a plurality of one another can have solar cells. It usually several solar modules are connected as a "string" in series, so that the need of the inverter module input voltage is achieved. The electric current generated in photovoltaic schem way is then fed to one or more solar inverters that convert which one or ones, the DC voltage supplied to a regulated standard mains voltage. Such solar inverters are known for 1- phase versions for example in DE 196 42 522 Cl. A photovoltaic system may further comprise a plant control level to control and management of multiple connected solar inverters.

p0007The operation of photovoltaic systems which feed into the public grid of power supply company, subject to relevant national or international regulations.

p0008For example, a maximum single-phase feed-in power of 4,6kVA allowed for the territory of the Federal Republic of Germany. At a higher feed-in power of the solar inverter is either run three-phase or single-phase provided that there are several solar inverters, which spread across the three phases of the electrical network feed. Here an unbalanced load between phases of over 4,6kVA is not allowed.

p0009In single-phase feed solar inverters and 4,6kVA approved and also single-phase Netzüberwachungsein- direction is provided. It monitors the network side continuously the mains voltage, the mains frequency and changes in the network impedance. Violations of the monitoring at the monitoring criteria will be a safe shutdown of the supplying solar inverter. The network monitoring device ensures that supply during maintenance work can bear no dangerous for the service personnel mains voltages when appropriate current branches are enabled by the power grid.

p0010For a higher power range, a three-phase grid monitoring device can be used, which is then approved for an electric power to 30kVA.

p0011On the territory of the Federal Republic of Germany Electrical Networks apply to public Liehe currently following monitoring criteria: Supply voltage range: 184V - 265V AC Frequency range: 49,8Hz - 50,2Hz impedance mismatch: <0,5Ω

p0012If any of the above monitoring criteria "injured", there is a shutdown of the respective solar inverter for about 30 seconds. Subsequently, another connection of the solar inverter, if the above criteria are within the allowable range.

p0013increasingly For some time there is a desire of operators of photovoltaic systems to be able to expand it. The cause is the one based on the fact that operators want to first operate the photovoltaic system "in the small" to tabilitat the pension to be able to verify the system before additional investments are made.

p0014Secondly, the feed is in the area of ​​Germany since 1.1.2004 the operation of facilities over 4, eg βkVA borrowed hinsieht- been favored, which has led to, increased demand for extensions of existing photovoltaic systems.

p0015For this reason, solar inverters are increasingly being offered which can be ranked according to their number according to the configured infeed modules together. Here, a central control and monitoring unit is responsible for controlling and monitoring the associated mostly through a communication with each solar inverter. then can such as the current feed-in power, the duration of sunshine and internal parameters of the connected inverters are presented and, if these parameters are changed, via a display unit and input keys of the control and monitoring device as in the case of an extension of the photovoltaic system. A disadvantage of the previous modular design of the solar inverter is that the respective network monitoring devices interact with each other in series of several modules of solar inverters, which led to increased unnecessary waste circuits of solar inverters and hence losses in terms of the energy supplied is.

p0016It is therefore an object of the invention to provide a photovoltaic system, which allows more efficient running and has a simpler structure.

p0017It is another object of the invention to provide a suitable central control and monitoring unit for such a photovoltaic system.

p0018The object is achieved with a photovoltaic system for feeding into an electric grid, the photovoltaic system several solar inverters, which feed on the output side to the power grid, and several photovoltaic generators up points, which are each connected to an input side of a solar inverter. A communication bus connects the solar inverter data purposes with each other, wherein a central control and monitoring unit is provided which is also connected to the communication bus for control and monitoring of solar inverters and has a network monitoring device, which switches off the solar inverter for failure predeterminable grid monitoring criteria at least temporarily.

p0019The great advantage of the invention lies in the fact that a central control and monitoring unit assumes the exclusive network monitoring. This is a mutual influence, such as avoided by an impedance jump a disconnected solar inverter, the other modular solar inverter, each with its own Netzuberwachungsreinrichtung. Unnecessary shutdowns of individual solar inverters are avoided. The electrical energy fed amount is increased. The network monitoring device of the central control and monitoring device can single or three phase according to the configured be designed solar feed-in power. The network monitoring device can be designed such that they can be exchanged within the central control and monitoring device.

p0020It is thus advantageously possible to use for example in expansion of the system instead of a single-phase three-phase grid monitoring device.

p0021The network monitoring devices typically require a technical approval of a national or international regulatory agency to comply with the relevant safety requirements. For this purpose, the network monitoring device measuring means for monitoring a predetermined voltage and / or frequency range and / or a predetermined impedance discontinuity value.

p0022The network monitoring device is particularly suitable for single-phase or three-phase public 50 Hz alternating current network, such as in Europe, or even for a 60 Hz AC power, such as in the US, formed.

p0023The object is further achieved with a central control and monitoring unit for controlling and monitoring of several solar inverters of a photovoltaic system for feeding into an electric grid and for monitoring predeterminable on grid tiger monitoring criteria.

p0024The invention is exemplified in more detail on the following single figure.

p0025The figure shows a photovoltaic system according to the invention PVA having four exemplary photovoltaic generators SM1-SM4. For clarity, the internal structure is not further illustrated. The photovoltaic generators SM1-SM4 dine here in a respective solar inverters M1-M4. In the example of the figure, each solar inverter M1-M4 has an inverter module WR, which is input connected to a photovoltaic generator PVA. Here, the solar is DC in a single-phase AC voltage converted. For safety can - as shown in the example of the figure - be this voltage Galvanic isolation to the voltage level of the photovoltaic generators SM1-SM4.

p0026In the example of the figure, the four solar inverters M1-M4 is fed into each phase R, S, T of an electric network SN, to achieve a uniform distribution in about performance in this network SN. Such a network SN is especially a public 3-phase 50Hz / 400V-voltage grid. With N the al- len three feeding solar inverters M1-M4 common neutral.

p0027Each solar inverter M1-M4 has a microcontroller .mu.C as electronic control unit. This is about electrical see interconnections for controlling, regulating and monitoring and diagnosis of the associated inverter module WR connected to this.

p0028In the example of the figure also the microcontroller .mu.C is connected to a bus interface BA. Such bus interface tailored also available as integrated components and the respective communication.

p0029A communication bus connects the solar inverter Ml M4 data purposes with each other, wherein a central control and monitoring unit MAS is provided which is also connected to the communication bus for control and monitoring of solar inverters M1-M4. The central control and monitoring unit MAS acts as the parent "Masters", which the "slaves", ie the exemplary four solar inverters M1-M4 modulates. According to the invention, the central control and monitoring unit MAS solely a network monitoring device, which switches off the solar inverter M1-M4, at least temporarily, in non-compliance with definable grid monitoring criteria, as described above.

p0030The central control and monitoring unit MAS advantageously has no power supply, such as an inverter on, but only includes the controlling and monitoring of solar inverters M1-M4 necessary additional electronic control unit .mu.C2 and a bus interface BA for connection to the communication bus.

p0031By eliminating the power unit an extremely compact design of the central control and monitor MAS is possible.

p0032In the example of the figure, the central control and monitoring unit MAS has a display unit DISP and input keys on T by which advantageous as current operating parameters such as the current electrical infeed power can be centrally displayed for the entire photovoltaic installation PVA. By means of the input keys T, it is eg possible to make changes to the configuration of the photovoltaic system PVA or to change the operating display DISP.