Title of Invention

STATIC CONVERTER CIRCUTT DIAGRAM ARRANGEMENT AND ACCOMPANYING TRIGGER PROCESS FOR GENERATORS WITH DYNAMICALLY CHANGEABLE OUTPUT

Abstract

The invention describes a static converter circuit arrangement as well as an allocated triggering procedure for connecting a three-phase generator with an energy network consisting of a first direct connection of the generator with the energy network and a second connetion of the generator(20) with the energy network(90), wherein here a four quadrant static converter is arranged in such a way that it consists of first power converter, whose three AC connections with three connections are linked with the energy network. The triggering procedure for idle current compensation in case of a network short circuit is designed such that in the first time period after the short circuit after the short circuit of the network side power converter supplies idle power through his AC connection in the energy network, in a second time period the power converter re-feeds idle power in the energy network and in a third time period the entire four quadrant converter controls the smooth restart without network loading with idle power of the generator.

Full Text

FORM 2 THE PATENTS ACT, 1970 (39 of 1970) COMPLETE SPECIFICATION (See Section 10, rule 13) STATIC CONVERTER CIRCUTT DIAGRAM ARRANGEMENT AND ACCOMPANYING TRIGGER PROCESS FOR GENERATORS WITH DYNAMICALLY CHANGEABLE OUTPUT SEMIKRCN ELEKTRONIK GMBH & CO. KG of POSTFACH 820251, 90253 NURNBERG, GERMANY, GERMAN Company The following specification particularly describes the nature of the invention and the manner in which it is to be performed : - ORIGINAL 1416/MUM/04 GRANTED 27-6-2007 Static converter circuit diagram arrangement and accompanying trigger process for generators with dynamically changeable output. Description [01] The invention describes a static converter circuit diagram arrangement for connecting a three-phase generator to energy network. Such circuit arrangements find exemplary use in a wind generator. Herein a dynamically varying output rating of the generator is obvious through the natural circumstances, the different wind speeds. [02] The current produced in the generator must be fed indeed according to voltage, frequency and phase into an existing power supply system. Typical values for this are voltages of a few hundreds to a few 10kv and frequencies of 50Hz or 60Hz. [03] The state of technology in wind energy generating plants having power generators producing dynamic current output with time-based variations is depicted as example through following technologies. [04] The DE 101,14,075 A1 reveals a complex integration of a generator with dynamically changeable output to a medium voltage power supply system. Herein the generator is connected with a bridge rectifier. This produces a DC voltage of a few kilo volts that is connected over a DC voltage connection with a cascading arrangement of inverter cells. This extremely flexible static converter circuit diagram arrangement can work very efficiently on the basis of the cascaded inverter cells and boost-converter integrated there in a large variance of the wind speeds and as a consequence thereof different output voltages of the generator. Disadvantage of such a static .converter circuit diagram arrangement is however that here no convenient and robust asynchronous machines can be used, because these require for the excitation a magnetic rotary field. 2- The relatively high expenditure in circuit technology, that excludes exemplary the installation of such a control arrangement into existing wind generator already for economic reasons, is further disadvantageous. [05] The US 5,652,485 reveals a simple possibility of integration of a wind generator at a energy network. Herein a four-quadrant inverter is switched directly with its change voltage connections between the output of the generator and the energy network. A Fuzzy-logic serves here as suitable for driving the four-quadrant inverter. It is herewith obvious that the four-quadrant inverter must show an efficiency that corresponds to the maximum output delivered by the generator, advantageous is this efficiency for guaranteeing of a secure operation even a little higher than that of the generator. [06] The simplest possibility of integrating a wind energy plant with a energy network is the direct connection of the generator of the wind energy plant with the energy network. For this purpose as generators preferably asynchronous machines are used due to their robust design. A so simple circuit arrangement has, however, several disadvantages. In case of low wind speeds, because of constant held generator speed a linkage to the energy network due to faulty output rating is not or with highly restricted efficiency possible. Further with this circuit arrangement not in each working condition, an idle power compensation is possible, which is required by the utility companies. [07] The invention describes further a trigger process of static converter circuit diagram arrangement for idle power (Wattless power) compensation in case of a short circuit in mains (power system). In case of a mains short circuit remains as a rule if the short circuit spot shows a certain distance from the spot to be observed, a residual voltage remains intact. If this remainder voltage shows another defined value, that is dependent of the specification of the energy network operator, exemplary 15% of the nominal voltage, then a feeding station, for example a wind energy producing station, connected there must be in a position to feed idle power into the energy network. A wind energy generator of above described architecture with direct connection of the generator with the energy network cannot perform this specification. 3 [08] The existing invention has the task to introduce a Static converter circuit diagram, that so extends the direct connection of a generator with dynamically changeable output to an energy network, that the generator"s rpm range, in which an efficient feeding into an energy network is possible, is extended to lower rpm, this extension can also be integrated with existing circuit arrangements and an idle power compensation during operation is possible, so as to introduce a trigger process, which in case of short circuit in the main can supply idle power" in the energy network. [09] The task is resolved through a Static converter circuit diagram arrangement with the features of the claim 1, as well as a trigger process as per the features of the claim 2. Preferred further developments can be found in sub-claims. [10] The invention based Static converter circuit diagram arrangement for connecting a three-phase generator with an energy network consists of two single connections. The first connection is a direct connection of the generator with the energy network wherein this connection has in each phase a switch, whereby this connection can be interrupted. The second connection of the generator with the energy network consists of a four-quadrant inverter consisting of two static converters, on their part each consisting of three half bridge circuit arrangernents of two circuit breakers each. This four-quadrant inverter has maximum half rated output of the generator. The second connection is arranged in such a way that the AC voltage connections of the first static converter are connected with the three-phases of the generator. The AC voltage connections of the second static converter are connected with the three phases of the energy network. Further, both static converters are connected with a common d.c. circuit wherein here between the positive and the negative connection of the d.c, intermediate circuit at least one condenser is fitted. [11] The invention based trigger process for an above named static converter circuit arrangement for the purpose of idle power compensation in case of a short circuit in the mains, wherein the remained supply voltage is same or larger than 10% of the rated voltage, can be divided into three time periods. The total short circuit phase up to an again reaching at least 80% of the rated voltage takes exemplary three seconds. Immediately after the short circuit, the generator will run down while being in direct connection with the energy network due to lack of supply voltage and separate 4 automatically from the energy network. In a connection over the four-quadrant inverter, the generator already connected not directly with the energy network. [12] In this first time period after the short circuit, with open switches between the generator and electricity network, the converter of four-quadrant inverter delivers via its alternating voltage connections idle power by means of energy stored in intermediate circuit into the energy network. During a subsequent second time period - similarly switches being open between the generator and the energy network - the network side converter draws active power for compensating his internal losses from the energy network and delivers idle power to the energy network. During this second time period, normally the supply voltage increases again. On reaching of exemplary 80% of the nominal voltage the feeding stations are again engaged In this third time period while as yet opened switches between the generator and the energy network the total four-quadrant inverter controls the smooth restart of the generator wherein no network load emerges with idle power. [13] In the further time period, dependent of the wind velocity and with that achievable generator output, the generator will supply power either via the four-quadrant inverter as before or directly being connected with the energy network via closed switches. [14] In the following the features and designs of the invention are explained as an example on the basis of Fig. 1, wherein the invention based Static converter circuit diagram arrangement is arranged in a wind power plant. [15] Represented is a wind power plant with a rotor (10) which drives a generator (20) through a gear. This generator (20) is an asynchronous machine with a nominal output voltage of 690V as per the state of the technology. The three output phases (22) are connected over a transformer (92) with a medium voltage energy network (90). So far the represented corresponds to the state of the technology how it is already in use severally as wind power plant. [16] For economical extension of an existing or also for manufacture of a new, economical wind power plant the represented circuit arrangement is extended according to the invention by a converter circuit. This converter circuit is designed as a four 5 quadrant inverter (100) and consists on generator side as well as network side of converter (50, 70) each, for its part made of three half bridge circuits each. Each of these half bridge circuits in turn consist of one upper (52, 72) and one lower (53, 73) power semiconductor switch respectively with anti-parallel connected recovery diode (54, 58, 74, 75). Both the converters (50, 70) are connected with their direct current cut outs (56, 58, 76, 78) through a direct current intermediate circuit (60) with an energy-storing condenser (62). [17] For integrating the four-quadrant inverter into the known circuit diagram, this has in the three phases (22) of the connection of the generator (20) to the energy network (90) one switch (30) per phase. Preferably consists each of these switches (30) of two anti-parallel connected power semiconductors, like Thyristors. The AC voltage connections (25) of the generator side converter (50) are connected respectively through a choke (40) with the three phases (22) of the generator (20). This connection (24) lies on the generator side of the switches (30). The alternating voltage connections (27) of the network side converter (70) are also connected respectively through a choke (80) with the three phases (22) of the generator, however this connection (26) lies of the network side of the switches (30) [18] At low wind velocities, by means of the switch (30) the first, that means the direct connection of the generator (20) with the energy network (90) is separated. The energy flows now over the four-quadrant inverter (100) to the current network. Because this connection is switched only for low wind velocities and therewith low rpm and thus low produced energy quantities, it is sufficient to design the four-quadrant inverter (100) to maximum half the output, preferably only one-third of the output of the generator (20). This has on the one hand the economic advantage of the lower costs of low capacity four-quadrant inverter (100), on the other hand hereby the mechanical installation is rendered easy. [19] In higher wind velocity, the switches (30) are closed, the electricity flows from the generator (20) directly to the energy network (90). In this case, both static converters (50, 70) of the four-quadrant inverter (100) deliver through suitable trigger the idle power to the energy network (90) as demanded by the network operator. 6 [20] The four-quadrant inverter (100) of the invention based Static converter circuit diagram arrangement serves in case of a short circuit the purpose of idle power compensation of the energy network (90). Based on the requests of the network operators, the nominal voltage to at least 80% is restored according to state of the technology after about three seconds. During this time, feeding stations like wind power generators must feed idle power into the energy network. For this purpose serves, the network side converter (70) actuated by the invention based triggering process of the four-quadrant inverter (100). [21] In the following it is assumed, that the generator (20) is directly connected that means through closed switches (30) with the energy network (90) After the short circuit the voltage of energy network (90) breaks down, for example, 20% the nominal value. After a period of approx. 150ms the nominal voltage restarts to increase until after three seconds the nominal voltage has again reached almost the original level. [22] The generator (20) delivers current in the case of the short circuit due to abscent external excitation only for few periods and is, therefore, automatically separated by means of the switch (30) from the energy network. Therefore the network side static converter (70) with its AC voltage connections has only a connection to the energy network (90) and can contribute to the idle power feeding into the energy network. Immediately after the short circuit, the network side static converter (70) is so actuated that he delivers idle power to the energy network (90). Herein in a first period after the short circuit the intermediate circuit (60) serves as a supplier of energy. While this idle power feeding, if required, for a short while currents can be fed above the nominal current of the circuit breakers, here power transistors (72, 73) (preferably IGBTs = Insulated Gate Bipolar transistor) as long as a thermal overload is avoided, that leads to the destruction of the power transistors. [23] In a second time period, until the power supply voltage has reached again 80% of the nominal voltage, the network side static converter (70) draws effective power out of the energy network (90) and feeds idle power back. The drawal of the effective power is necessary because the losses must be balanced, like for example switching losses of the IGBTs (72, 73) within the static converter (70). 7 [24] After reaching 80% of the nominal voltage in the third time period, the generator (20) is engaged again. The four-quadrant inverter (100) is actuated now in such a way that a soft restart of the generator (20) is guaranteed without network load with idle power. Subsequently the switches (30) are opened and a business such as before the short circuit is again possible. 8 We Claims: 1. Static converter for connecting a three-phase generator (20) with a energy network (90), consisting of a first direct connection of the generator (20) with the energy network (90) wherein this connection in each phase (22) has a switch (30), and of a second connection of the generator (20) with the energy network (90), wherein here a four-quadrant inverter (100) is so arranged with maximum half the nominal power of the generator (20), that the four-quadrant inverter (100) consists of first static converter (50), whose three alternating voltage connections (24) are connected with the three connections of the generator (20) and its DC current connections (56, 58) with an intermediate circuit (60) with a condenser (62), and a second current static converter (70) whose three alternating voltage connections (26) are connected with the energy network (90) and its direct current connections (76, 78) with the intermediate circuit (60). 2. Trigger process for a Static converter as per claim 1 for idle power compensation in case of a short circuit wherein the remainder power supply voltage is equal to or greater than 10% of the nominal voltage, to such an extent that in a first time period after the short circuit, wherein the switches (30) already are open or are opened due to short circuit, the network side static converter (70) supplies over its AC connections (24, 26) idle power from the energy stored in the intermediate circuit (60) in the energy network, in a second time period with continuously open switches (30) of the static converter (70) supplies idle power back into the energy network (90) and in a third time period with opened switches (30) the total four-quadrant inverter (100) controls the smooth restart of the generator (20) and herein holds the network load with idle power to the minimum or prevents and subsequently the generator again, supplies either further over the four-quadrant inverter (100) or directly connected, energy to the energy network (90). 9 3. Static converter as per claim 1 whereby each static converter (50, 70) consists of three half bridge circuits each with one upper and one lower circuit breaker. 4. Static converter as per claim 3 wherein each circuit breaker consists of one or more output transistors (52, 53, 72, 73) with respectively one or more anti-parallel connected power diodes (52, 53, 74, , 75). 5. Static converter as per claim 1 wherein each of the switches (30) consists of two power semiconductor switches connected anti-parallel, like Thyristors. 6. Control procedure as per claim 2 wherein within the first time period the power circuit breaker of the static converter (50, 70) are burdened beyond their nominal load, as long as this is possible for the power circuit breaker destruction free. Dated this 27th day of December, 2004 HIRAL CHANDRAKANT JOSHI AGENT FOR SEMIKRON ELEKTRONIK GMBH & CO.KG 10

Documents:

1416-mum-2004-abstract(27-06-2007).doc

1416-mum-2004-abstract(27-06-2007).pdf

1416-MUM-2004-CANCELLED PAGES(16-4-2009).pdf

1416-mum-2004-cancelled pages(27-06-2007).pdf

1416-mum-2004-claims(granted)-(27-06-2007).doc

1416-mum-2004-claims(granted)-(27-06-2007).pdf

1416-MUM-2004-COPY OF EP(16-4-2009).pdf

1416-MUM-2004-CORRESPONDENCE(16-4-2009).pdf

1416-mum-2004-correspondence(27-06-2007).pdf

1416-mum-2004-correspondence(ipo)-(09-05-2008).pdf

1416-mum-2004-drawing(27-06-2007).pdf

1416-mum-2004-form 1(27-06-2007).pdf

1416-mum-2004-form 13(27-09-2005).pdf

1416-mum-2004-form 18(19-12-2006).pdf

1416-mum-2004-form 2(granted)-(27-06-2007).doc

1416-mum-2004-form 2(granted)-(27-06-2007).pdf

1416-mum-2004-form 3(01-01-2005).pdf

1416-mum-2004-form 3(27-12-2004).pdf

1416-mum-2004-form 5(01-01-2005).pdf

1416-mum-2004-form 5(27-12-2004).pdf

1416-MUM-2004-GENERAL POWER OF ATTORNEY(16-4-2009).pdf

1416-mum-2004-power of attorney(27-12-2004).pdf

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