Method for controlling inverter assemblies in a power generation system having parallel inverters

Abstract

The invention relates to a method for controlling a set of at least two inverters (1a, 1b) in a power generation system having parallel inverters. The method comprises the following steps implemented by at least one data processing unit (2a, 2b): (a) for each inverter (1a, 1b) of said set, obtaining an input duty cycle (PWMi) of an input signal (Si) received by the inverter (1a, 1b), (b) calculating a mean duty cycle (PWMm) from the input duty cycles (PWMi), (c) modulating and synchronizing the input signal (Si) received by each inverter (1a, 1b) into an output signal (So) having an output duty cycle (PWMo) corresponding to the mean duty cycle (PWMm).

Description

Technical Field

[0001] The present invention relates to a method for controlling a group of inverters in a power generation system having parallel inverters. Background Technology

[0002] In the aviation industry, it is well known that synchronous three-phase generators are powered by each engine of an aircraft. Inverters allow direct current (DC) to be converted to alternating current (AC) to drive loads (electric motors, heating systems, etc.). These inverters can be single-phase or multi-phase inverters.

[0003] In the traditional approach, several inverters are used in parallel in synchronous mode (such as...). Figure 1 (As shown). Therefore, these inverters have output inductors connected to each other. However, during operation, any difference in the duty cycle of the current supplied by each inverter or any difference in synchronization between the inverters can cause circulating current between the inverters. Figure 2 As shown, these circulating currents cause a shift in the current drawn from the inverter. To reduce these currents, it is known to increase the output inductance, such as by... Figure 3 As seen in the diagram, the greater the increase in inductance, the more the circulating current decreases. However, increasing the output inductance increases the system's mass. Mass is, as is well known, a limiting factor in aeronautics. Therefore, this approach is not satisfactory.

[0004] Therefore, it is necessary to provide a method for controlling a group of inverters in a power generation system with parallel inverters, which allows for a stable output signal without increasing the mass of the embedded components, and prevents the output signal from deviating. Summary of the Invention

[0005] According to a first aspect, the present invention relates to a method for controlling a group of at least two inverters in a power generation system having inverters in parallel. The method includes the following steps implemented by at least one data processing unit:

[0006] (a) For each inverter in the group, obtain the input duty cycle of the input signal received by the inverter.

[0007] (b) Calculate the average duty cycle from the input duty cycle.

[0008] (c) The input signal received by each inverter is modulated and synchronized into an output signal, the output signal having an output duty cycle corresponding to the average duty cycle.

[0009] In a particularly advantageous manner, the average duty cycle of a set of input duty cycles is calculated and used to modulate the output signal, enabling all inverters to emit the same stable signal. In other words, the method according to the invention provides a redundant (and therefore safe) system in which all inverters emit the same synchronous output signal, thereby avoiding phase shift problems and eliminating the need to add additional coils to the inverter output, thus reducing quality issues.

[0010] According to a preferred embodiment, each inverter in the group may include a dedicated data processing unit, and step (a) is implemented by a plurality of the dedicated data processing units.

[0011] According to a particularly preferred embodiment, step (a) may include the input duty cycle of the signal received by each inverter of the group from the group of inverters.

[0012] This approach provides a robust and redundant system where information is shared. In other words, it allows for the multiplication of information exchange to prevent a global failure in the event of an inverter malfunction.

[0013] Step (a) may include each of the plurality of data processing units determining the input duty cycle of the input signal received by the inverter.

[0014] Step (b) can be implemented independently by each data processing unit that implements step (a).

[0015] Each inverter may include a modulation unit, and step (c) includes sending modulation control to the modulation unit of each inverter in the group.

[0016] Step (c) can be implemented independently by each data processing unit.

[0017] Step (c) can be performed by generating a rectangular signal at a determined frequency, wherein the ratio of the time in the high state of the signal to the period of the signal at the determined frequency corresponds to the value of the output duty cycle.

[0018] According to a second aspect, the present invention relates to a set of parallel inverters located in a power generation system, controlled by a method according to the invention.

[0019] An inverter may include a data processing unit, a communication unit, and a modulation unit.

[0020] The data processing unit can be adapted to implement step (b).

[0021] The communication unit may be adapted to implement step (a) of the method to send the input duty cycle obtained by the inverter and receive the input duty cycle obtained by other inverters.

[0022] The modulation unit can be adapted to implement step (c).

[0023] According to a third aspect, the present invention relates to a computer program product comprising code instructions that, when executed on a computer, automated machine, or programmable logic circuit, are used to perform a method according to the invention for controlling a group of inverters.

[0024] According to a fourth aspect, the present invention relates to a storage device readable by a computer device, wherein a computer program product on the storage device includes code instructions for executing a method according to the invention for controlling a group of inverters. Attached Figure Description

[0025] Other features and advantages of the invention will become apparent from the following description, which is purely illustrative and not restrictive, and should be read with reference to the accompanying drawings, in which:

[0026] - Figure 1 It is the wiring diagram of a known system;

[0027] - Figure 2 yes Figure 1 The phase curve of the signal at the output of the system;

[0028] - Figure 3 Improve by displaying current circulation on the wiring diagram Figure 2 ;

[0029] - Figure 4 This is a block diagram of a group of parallel inverters controlled by the method according to the present invention;

[0030] - Figure 5 This is a wiring diagram of a set of inverters according to the present invention. Detailed Implementation

[0031] The present invention relates to a method for controlling a group of inverters 1a, 1b in a power generation system having parallel inverters, and to a group of inverters 1a, 1b.

[0032] For convenience, the following description is made with reference to two inverters 1a and 1b, but the invention is by no means limited to two inverters 1a and 1b. The invention can be implemented with three, four, or as many inverters as needed.

[0033] Inverter

[0034] Inverters 1a and 1b mainly include processing units 2a and 2b, communication units 4a and 4b, and modulation units 6a and 6b.

[0035] Inverters 1a and 1b consist of digital electronic devices including a control section and an electronic power section.

[0036] The control section integrates processing units 2a and 2b and communication units 4a and 4b. The control section can be fully integrated into inverters 1a and 1b or partially offset outside of inverters 1a and 1b.

[0037] The electronic power section integrates modulation units 6a and 6b.

[0038] According to the embodiments given here, a programmable logic circuit of the "Field Programmable Gate Array" (FPGA) type integrates a control section, namely, processing units 2a, 2b and communication units 4a, 4b.

[0039] Processing units 2a and 2b communicate with external systems via communication units 4a and 4b to receive local duty cycles and send inverter health data. Furthermore, processing units 2a and 2b average the duty cycles received from other inverters 1a and 1b.

[0040] Communication units 4a and 4b are based on a multi-point bus (1 to n), i.e., n buses, to connect n inverters 1a and 1b in parallel.

[0041] According to the embodiment given herein, modulation units 6a and 6b generate an output signal So based on a signal requested by processing units 2a and 2b using a carrier signal Sp corresponding to the requested average duty cycle PWMm. The carrier signal Sp is synchronized by an external signal that allows modulation units 6a and 6b of different inverters 1a and 1b to generate the same signal So (after averaging) at the same time (synchronously). These signals So, with duty cycles PWMo, control power transistors to generate the output current of each inverter 1a and 1b. Therefore, a change in the duty cycle can modulate the output signal So.

[0042] In operation, typically, each inverter 1a, 1b receives an input signal Si representing the input duty cycle PWMi. Data processing units 2a, 2b know how to determine the input duty cycle PWMi. Inverters 1a, 1b can modulate the received input signal Si by applying an output duty cycle PWMo. The output duty cycle PWMo is determined, recorded, or received by the data processing units 2a, 2b. Then, the data processing units 2a, 2b instruct the modulation units 6a, 6b to modulate the received input signal Si such that the output signal So of the inverters 1a, 1b has the desired output duty cycle PWMo.

[0043] It is stipulated that if the output duty cycle PWMo is sent to the data processing units 2a and 2b, the transmission shall be completed by the communication units 4a and 4b.

[0044] Furthermore, as described below, communication units 4a and 4b can also be used to exchange information among several inverters 1a and 1b. The exchanged information may, for example, be the input duty cycle PWMi of each inverter 1a and 1b.

[0045] Inverters 1a and 1b are adapted to be controlled according to the method described below.

[0046] Inverters 1a and 1b are specified to be multiphase inverters. In this case, the control method (given below) operates on the total number of phases of inverters 1a and 1b.

[0047] Control methods

[0048] The present invention relates to a method for controlling a group of inverters 1a, 1b in a power generation system having parallel inverters.

[0049] The method includes the following steps:

[0050] (a) For each inverter 1a, 1b in the group, obtain the input duty cycle PWMi of the input signal Si received by the inverter 1a, 1b.

[0051] (b) Calculate the average duty cycle PWMm from the input duty cycle PWMi.

[0052] (c) The input signal Si received by each inverter 1a, 1b is modulated and synchronized into an output signal So, the output signal So having an output duty cycle PWMo corresponding to the average duty cycle PWMm.

[0053] According to the first embodiment, the method uses external processing units 2a, 2b, which receive the input duty cycle PWMi sent via communication units 4a, 4b from each inverter 1a, 1b (step (a)).

[0054] Typically, external processing units 2a and 2b can be computers, automated machines, or programmable logic circuits, including communication devices and at least one processor and / or functions executed in wiring logic. According to this embodiment, step (b) is performed by an external processing unit that receives all input duty cycles PWMi, thereby determining the average duty cycle PWMm by calculating the average of the input duty cycles. This average duty cycle PWMm is then sent to inverters 1a and 1b via communication units 4a and 4b. Then, the data processing units 2a and 2b of each inverter 1a and 1b instruct modulation units 6a and 6b to modulate the received input signal Si into an output signal So accordingly, such that the output duty cycle PWMo is equal to PWMm.

[0055] According to a preferred embodiment, the three steps (a), (b), and (c) can be performed by all or some of the units of inverters 1a and 1b. Therefore, the system is redundant and robust in the event of a failure of one or more inverters 1a and 1b.

[0056] More specifically, each inverter 1a, 1b receives an input signal Si. Processing units 2a, 2b determine the corresponding input duty cycle PWMi (step (a)). Then, communication units 4a, 4b of each inverter 1a, 1b send the input duty cycle PWMi to the other inverters 1 (step (a)). Thus, each communication unit 4a, 4b sends the input duty cycle PWMi through its inverter 1a or 1b and receives the input duty cycle PWMi from the other inverters 1a or 1b (step (a)). All input duty cycles PWMi are sent to the processing units 2a, 2b of each inverter 1a, 1b (step (a)). Then, each processing unit 2a, 2b calculates the average duty cycle PWMm corresponding to the average value of the input duty cycles PWMi (step (b)). Then, the average duty cycle PWMm is sent to the modulation units 6a, 6b. Then, modulation units 6a and 6b modulate the received input signal Si according to the average duty cycle PWMm (step (c)), such that the output duty cycle PWMo is equal to the average duty cycle PWMm. In a particularly advantageous manner, each inverter 1a and 1b subsequently transmits the same output signal So with the same average duty cycle PWMm. Therefore, the set of output signals So transmitted by inverters 1a and 1b is synchronized, such that there is no offset between the set of output signals.

[0057] An additional step can be added to compare the determined average duty cycle PWMm for each inverter 1a, 1b. This checking step can be performed by mutual exchange, such as performing mutual exchange on the input duty cycle PWMi. According to another approach, this step can be delegated to a single inverter 1a, 1b established as a trusted inverter 1a, 1b, which centralizes all determined average duty cycles PWMm and compares the determined average duty cycle with its own average duty cycle PWMm. According to yet another approach, the checking and comparison of the average duty cycle PWMm can be performed by an external processing unit.

[0058] Computer program products

[0059] According to a third aspect, the present invention relates to a computer program product comprising computer program product code instructions, wherein when the program is executed on a computer, the code instructions are used to perform a method according to the invention for controlling a group of inverters 1a, 1b.

[0060] It should be understood that the computer can be embedded in each inverter 1a, 1b and includes data processing units 2a, 2b. The computer may also include communication units 4a, 4b. In this case, the computer can be an electronic card, such as a programmable logic circuit or an automated machine.

[0061] storage device

[0062] According to a fourth aspect, the present invention relates to a storage device, readable by a computer device, wherein a computer program product on the storage device includes instructions for executing a method according to the invention for controlling a group of inverters 1a, 1b. The storage device may be the internal memory of processing units 2a, 2b of the inverters 1a, 1b.

Claims

1. A method for controlling a group of at least two inverters (1a, 1b) in a power generation system having inverters in parallel, the method being characterized in that it comprises the following steps implemented by at least one data processing unit (2a, 2b): (a) for each inverter (1a, 1b) of the group, obtaining an input duty cycle (PWMi) of an input signal (Si) received by the inverter (1a, 1b), (b) calculating an average duty cycle (PWMm) from the input duty cycles (PWMi), (c) modulating and synchronizing the input signal (Si) received by each inverter (1a, 1b) into an output signal (So) having an output duty cycle (PWMo) corresponding to the average duty cycle (PWMm).

2. The method of claim 1, wherein, Each inverter (1a, 1b) of the group comprises a data processing unit (2a, 2b), step (a) being implemented by a plurality of said data processing units (2a, 2b).

3. The method of claim 2, wherein, Step (a) comprises receiving by each inverter (1a, 1b) of the group an input duty cycle (PWMi) of the input signal (Si) received by the group of inverters (1a, 1b).

4. The method of claim 2 or 3, wherein, Step (a) comprises determining by each of the plurality of data processing units (2a, 2b) the input duty cycle (PWMi) of the input signal (Si) received by the inverter (1a, 1b).

5. The method of claim 2 or 3, wherein, Step (b) is implemented independently by each data processing unit (2a, 2b) implementing step (a).

6. The method of any one of claims 1 to 3, wherein, Each inverter (1a, 1b) comprises a modulation unit (6a, 6b), step (c) comprising, for each inverter (1a, 1b) of the group, sending a modulation control to the modulation unit (6a, 6b) of the inverter (1a, 1b).

7. The method of claim 5, wherein, Each inverter (1a, 1b) comprises a modulation unit (6a, 6b), step (c) comprising, for each inverter (1a, 1b) of the group, sending a modulation control to the modulation unit (6a, 6b) of the inverter (1a, 1b); wherein step (c) is implemented independently by each data processing unit (2a, 2b).

8. The method of any one of claims 1 to 3, wherein, Step (c) is performed by generating a square signal at a determined frequency, wherein the ratio of the time spent in the high state of the signal to the period of the signal at the determined frequency corresponds to the value of the output duty cycle (PWMo).

9. A set of parallel inverters (la, lb) located in a power generation system, characterized in that, The inverters (1a, 1b) are controlled according to the method of any one of claims 1 to 8.

10. The set of parallel inverters of claim 9, wherein, Each inverter (1a, 1b) comprises a data processing unit (2a, 2b), a communication unit (4a, 4b) and a modulation unit (6a, 6b).

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