Metering device, metering system and converter
By setting multiple communication interfaces in the metering circuit, one metering device can serve multiple control devices, solving the problems of large number of devices and large space occupation in the existing technology, reducing costs and saving space.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2026-03-17
AI Technical Summary
In the existing technology, the metering device and the converter control system of the wind turbine are each equipped with a separate metering device, resulting in a large number of devices, high cost and large space occupation.
Design a metering device that connects to a wind turbine generator set and a converter control device by setting multiple communication interfaces in the metering circuit, so that one metering device can serve multiple control devices and share metering data.
It reduces the cost of metering devices, saves space, and allows multiple control devices to acquire metering data.
Smart Images
Figure CN224005175U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power technology, and in particular to a metering device, metering system and converter. Background Technology
[0002] In related technologies, the main control system of a wind turbine generator set is equipped with a metering device. In this metering device, the metering equipment samples the current through a current transformer and samples the voltage through a voltage transformer or a high-voltage isolation resistor to calculate the power. In addition, the converter control system is equipped with another metering device, resulting in a large number of metering devices installed on the power line, which is costly and occupies a lot of space. Utility Model Content
[0003] In view of this, the purpose of this application is to provide a metering device, a metering system and a converter to reduce the cost of the metering device and save space.
[0004] In a first aspect, embodiments of this application provide a metering device, which includes a voltage sampling device, a voltage sampling circuit, a current sampling device, a current sampling circuit, and a metering circuit; the voltage sampling device is used to detect the voltage of a line, and the current sampling device is used to detect the current of a line; the voltage sampling device, the voltage sampling circuit, and the metering circuit are connected in sequence; the current sampling device, the current sampling circuit, and the metering circuit are connected in series; the metering circuit is provided with multiple communication interfaces, which are used to connect to corresponding control devices.
[0005] The aforementioned multiple communication interfaces include: a first communication interface and a second communication interface; the control device includes: a wind turbine generator control device and a converter control device; the first communication interface is connected to the wind turbine generator control device, and the second communication interface is connected to the converter control device.
[0006] The aforementioned metering circuit and the second communication interface are located within the converter control device; the first communication interface is located on the converter control device.
[0007] The aforementioned metering circuit and the first communication interface are located inside the wind turbine generator control device; the second communication interface is located on the wind turbine generator control device.
[0008] The aforementioned metering circuit includes: a metering chip and a signal processing chip that are interconnected; the metering chip is connected to a voltage sampling circuit and a current sampling circuit; and the signal processing chip is connected to multiple communication interfaces.
[0009] The metering circuit mentioned above includes: a metering chip, the metering chip being connected to a first processing chip in the converter control device, and a first communication interface being disposed on the first processing chip.
[0010] The aforementioned metering circuit includes: a metering chip, which is connected to a second processing chip in the wind turbine generator control device, and a second communication interface is located on the second processing chip.
[0011] The aforementioned current sampling circuit is connected to the current signal interface of the converter control device.
[0012] Secondly, embodiments of this application provide a metering system, which includes the aforementioned metering device and also includes multiple control devices; multiple communication interfaces in the metering device are respectively connected to the corresponding control devices.
[0013] The aforementioned control devices include: a wind turbine generator control device and a converter control device; the wind turbine generator control device and the converter control device are communicatively connected.
[0014] Thirdly, embodiments of this application provide a converter, which includes: a metering device; the metering device is connected to the control system of the converter.
[0015] The aforementioned metering device, metering system, and converter include a voltage sampling device, a voltage sampling circuit, a current sampling device, a current sampling circuit, and a metering circuit. The voltage sampling device is used to detect the line voltage, and the current sampling device is used to detect the line current. The voltage sampling device, voltage sampling circuit, and metering circuit are connected sequentially; the current sampling device, current sampling circuit, and metering circuit are connected in series. The metering circuit is equipped with multiple communication interfaces for connecting to corresponding control devices. In this method, the metering circuit has multiple communication interfaces to connect to different control devices. Only one metering device is installed on the line, and multiple control devices can obtain metering data. It is not necessary to install a separate metering device for each control device, thus reducing the cost of the metering device and saving space.
[0016] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description
[0017] To more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram of a measurement method in a related technology;
[0019] Figure 2A schematic diagram of a metering device provided in an embodiment of this application;
[0020] Figure 3 A schematic diagram of another metering device provided in the embodiments of this application;
[0021] Figure 4 This is a schematic diagram of the circuit connection of the first metering device provided in the embodiments of this application;
[0022] Figure 5 This is a schematic diagram of the wiring connection of the second metering device provided in the embodiments of this application;
[0023] Figure 6 A schematic diagram illustrating the first current sampling method provided in this application embodiment;
[0024] Figure 7 A schematic diagram illustrating a second current sampling method provided in an embodiment of this application;
[0025] Figure 8 A schematic diagram illustrating the third current sampling method provided in the embodiments of this application;
[0026] Figure 9 A schematic diagram of another metering device provided in the embodiments of this application;
[0027] Figure 10 A schematic diagram of another metering device provided in the embodiments of this application;
[0028] Figure 11 A schematic diagram of another metering device provided in the embodiments of this application;
[0029] Figure 12 A schematic diagram of another metering device provided in the embodiments of this application;
[0030] Figure 13 A schematic diagram of a metering system provided in an embodiment of this application;
[0031] Figure 14 A schematic diagram of another metering system provided in the embodiments of this application;
[0032] Figure 15 This is a schematic diagram of a converter provided in an embodiment of this application. Detailed Implementation
[0033] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0034] In the power system of wind turbine generator sets, the main control system of the wind turbine generator set needs to collect the net grid power of the converter. Therefore, a metering device is connected to the main control system. The metering device integrates current sampling circuit and voltage sampling circuit. The current sampling circuit collects the current signal on the power line through the current transformer CT, and the voltage sampling circuit collects the voltage signal on the power line through the voltage transformer PT or high-voltage isolation resistor. The metering device calculates the power, circuit and other metering data through the current signal and voltage signal, and then sends them to the main control system.
[0035] Similarly, the converter control system also needs to collect the net on-grid power of the converter. Therefore, the converter control system is also connected to an external metering device. The metering device integrates current sampling circuit and voltage sampling circuit. The current sampling circuit collects the current signal on the power line through the current transformer CT, and the voltage sampling circuit collects the voltage signal on the power line through the voltage transformer PT or high-voltage isolation resistor. The metering device calculates the power, circuit and other metering data through the current signal and voltage signal, and then sends them to the converter control system.
[0036] like Figure 1 As shown, current transformers and voltage transformers are connected to the power lines between the transformer and the converter. The power lines are three-phase power lines. Current transformers CT1, CT2 and CT3 are each connected to one phase of the power line, and current transformers CT4, CT5 and CT6 are each connected to one phase of the power line.
[0037] The main control system of a wind turbine generator is connected to a set of metering equipment, current sampling circuit, voltage sampling circuit, current transformer, and voltage transformer PT (or high-voltage isolation resistor). In addition, the converter control system is also connected to a set of metering equipment, current sampling circuit, voltage sampling circuit, current transformer, and voltage transformer PT (or high-voltage isolation resistor). This method results in a large number of devices, high cost, and requires a large space.
[0038] Based on this, the metering device, metering system and converter provided in the embodiments of this application can be applied to the metering of various types of lines, such as voltage and current metering of high-voltage lines.
[0039] To facilitate understanding of this embodiment, a measuring device disclosed in this application will first be described in detail, such as... Figure 2As shown, the metering device includes a voltage sampling device 20, a voltage sampling circuit 21, a current sampling device 22, a current sampling circuit 23, and a metering circuit 24.
[0040] Voltage sampling devices are used to detect the voltage of the line, and current sampling devices are used to detect the current of the line; the voltage sampling devices and current sampling devices are connected to the line respectively. The voltage sampling device, voltage sampling circuit, and metering circuit are connected in sequence; the current sampling device, current sampling circuit, and metering circuit are connected in series.
[0041] This line is typically a high-voltage line; for example, in a power generation system, it might be the line between a converter and a transformer connected to the power grid. The voltage sampling device can be a voltage transformer (PT) or a high-voltage isolation resistor. When the line is three-phase, one voltage sampling device is installed for each phase. The voltage sampling device can collect the phase voltage or line voltage of the line.
[0042] The voltage sampling device may include multiple devices; each voltage sampling device is connected to a voltage sampling circuit; the line is a three-phase line, with each phase connected to a corresponding voltage sampling device. For example, when the voltage sampling device is a voltage transformer, one voltage transformer is connected to each phase; when the voltage sampling device is a high-voltage isolation resistor, one high-voltage isolation resistor is connected to each phase.
[0043] The current sampling device can be a current transformer (CT) or other devices with current sampling function. The current sampling circuit can be used to control the sampling time interval and to convert the current signal collected by the current sampling device, and send the converted current signal to the metering circuit.
[0044] The aforementioned current sampling devices may include multiple devices; each current sampling device is connected to a current sampling circuit; the line is a three-phase line, with each phase line connected to a corresponding current sampling device. For example, when the current sampling device is a current transformer, one current transformer is connected to each phase line.
[0045] The voltage sampling circuit can be used to control the sampling time interval and to convert the voltage signal collected by the voltage sampling device, and then send the converted voltage signal to the metering circuit.
[0046] Metering circuits typically include metering chips, and may also include MCU (Microcontroller Unit) chips. The metering chip calculates data such as power and energy consumption based on the received voltage and current signals.
[0047] The aforementioned metering circuit is equipped with multiple communication interfaces 25, which are used to connect to corresponding control devices. These communication interfaces are used to transmit metering data such as current, voltage, and power and circuit parameters calculated by the metering circuit.
[0048] By setting up multiple communication interfaces, data can be sent to different control devices, such as wind turbine generator control devices and converter control devices; Figure 2 In the example, control device 1, control device 2, and so on up to control device n are connected to different communication interfaces. The communication interface can be a fiber optic interface or a network cable interface, such as a PROFIBUS (Process Filter BUS) interface, a CAN (Controller Area Network) interface, an RS485 interface, etc.
[0049] The aforementioned metering device includes a voltage sampling device, a voltage sampling circuit, a current sampling device, a current sampling circuit, and a metering circuit. The voltage sampling device is used to detect the voltage of the line, and the current sampling device is used to detect the current of the line. The voltage sampling device, voltage sampling circuit, and metering circuit are connected in sequence; the current sampling device, current sampling circuit, and metering circuit are connected in series. The metering circuit is equipped with multiple communication interfaces for connecting to corresponding control devices. In this method, the metering circuit is equipped with multiple communication interfaces to connect to different control devices. Only one metering device is installed on the line, and multiple control devices can obtain metering data. It is not necessary to install a separate metering device for each control device, thus reducing the cost of the metering device and saving space.
[0050] In one specific implementation, such as Figure 3 The system includes multiple communication interfaces, including a first communication interface 250 and a second communication interface 251; the control device includes a wind turbine generator control device and a converter control device; the first communication interface is connected to the wind turbine generator control device, and the second communication interface is connected to the converter control device.
[0051] The wind turbine generator control device can also be called the main control system of the wind turbine generator, and the converter control device can also be called the converter control system.
[0052] Figure 4 for Figure 3 The diagram shows the circuit connections corresponding to the metering device. Current transformers CT1, CT2, and CT3 are connected to the current sampling circuit to collect the current signal of each phase of the line. The current signal is processed by the current sampling circuit and then sent to the metering circuit. Voltage transformers or high-voltage isolation resistors collect the voltage signal of each phase of the line. The voltage signal is processed by the voltage acquisition circuit and then sent to the metering circuit. The current sampling circuit, voltage sampling circuit, and metering circuit can be integrated into a metering device.
[0053] Figure 4 The measuring device in the middle is relative to Figure 1This saves three current transformers and a set of voltage transformers or high-voltage isolation resistors, as well as a current sampling circuit, a voltage sampling circuit, and a metering circuit, effectively reducing the cost of the metering device and saving space.
[0054] In addition, one current transformer can be saved, reducing the number of current transformers from three to two. These two current transformers can be connected to any two phase lines respectively. Figure 5 In the circuit, current transformers CT1 and CT2 are connected to two phases of the circuit, while current transformer CT3 is omitted.
[0055] For details, see Figure 6 In a three-phase circuit, each of phases A, B, and C is connected to a current sampling device, designated as current sampling device 1, current sampling device 2, and current sampling device 3, respectively. Each current sampling device is further connected to a current sampling circuit; specifically, current sampling device 1 is connected to current sampling circuit 1, current sampling device 2 to current sampling circuit 2, and current sampling device 3 to current sampling circuit 3. Current sampling circuits 1, 2, and 3 are then connected to a metering circuit. The current sampling circuit can specifically be a current transformer.
[0056] The current sampling device collects the current signal of each phase line, and the current signal is processed by the corresponding current sampling circuit and then sent to the metering circuit.
[0057] See Figure 7 The circuit is a three-phase circuit, and it includes two current sampling devices; each current sampling device is connected to any two phases of the circuit. Figure 7 The example given is connecting phase A and phase B lines. Of course, phase A and phase C lines can also be connected, or phase B and phase C lines can be connected.
[0058] The current sampling circuit consists of two circuits, each connected to a corresponding current sampling device; the two current sampling circuits are connected to the control chip in the metering circuit. This control chip can be an MCU chip or other types of chips.
[0059] The current sampling device collects the current signals of the two phase lines respectively. After the current signals are processed by the corresponding current sampling circuit, they are sent to the control chip in the metering circuit. The control chip can calculate the current signal of the phase line without the current sampling device based on the current signals of the two phase lines.
[0060] For example, Figure 7 Two current sampling devices sample the current signals of phase A and phase B lines, and the control chip can calculate the current signal of phase C line based on the current signals of phase A and phase B lines.
[0061] See Figure 8 The line is a three-phase line, and the current sampling devices include a first current sampling device and a second current sampling device; the current sampling circuit includes a first current sampling circuit, a second current sampling circuit and a third current sampling circuit;
[0062] The first current sampling device is connected to the first phase line in the circuit. The first current sampling device is also connected to the input terminal of the first current sampling circuit. The output terminal of the first current sampling circuit is connected to the output terminal of the third current sampling circuit. The input terminal of the third current sampling circuit is connected to the first current sampling device.
[0063] The second current sampling device is connected to the second phase of the circuit. It is also connected to the input of the second current sampling circuit, whose output is connected to the output of the third current sampling circuit. The input of the third current sampling circuit is connected to the second current sampling device.
[0064] The first phase and the second phase can be any two phases in the line. Figure 8 If phase A and phase C are connected, phase A and phase B can also be connected, or phase B and phase C can be connected.
[0065] If the current signal of phase A is IA, the output signal of the first current sampling circuit is IA; if the current signal of phase C is IC, the output signal of the second sampling current is IC. Since the output of the first current sampling circuit and the output of the second sampling current are both connected to the output of the third current sampling circuit, the signal of the output of the third current sampling circuit is -IA-IC. Therefore, the current signal of phase B can be obtained as -IA-IC.
[0066] The first current sampling circuit, the second current sampling circuit, and the third current sampling circuit output corresponding current signals to the metering circuit, so that the metering circuit can obtain the current signal of each phase line.
[0067] See Figure 9 This embodiment provides another metering device, in which the metering circuit and the second communication interface are located within the converter control device; the first communication interface is located on the converter control device. In this method, the metering circuit is integrated into the converter control device, and the wind turbine generator control device obtains metering data from the converter control device.
[0068] Specifically, the metering circuit includes a metering chip, which is connected to a first processing chip in the converter control device. A first communication interface is located on the first processing chip. This first processing chip can be a microcontroller, MCU (Micro Controller Unit) chip, etc.
[0069] The metering chip can be connected to the first processing chip via the second communication interface, and the first processing chip is connected to the first communication interface.
[0070] The wind turbine generator control device is connected to the first communication interface on the converter control device; the metering data output by the metering circuit can be sent to the first processing chip inside the converter control device, and then the metering data is sent to the wind turbine generator control device through the first processing chip. This method can also achieve the installation of one metering device, with multiple control devices obtaining metering data.
[0071] See Figure 10 This embodiment provides another metering device, in which the metering circuit and the first communication interface are located within the wind turbine generator control device; the second communication interface is located on the wind turbine generator control device. In this method, the metering circuit is integrated into the wind turbine generator control device, and the converter control device obtains metering data from the wind turbine generator control device.
[0072] Specifically, the metering circuit includes a metering chip, which is connected to a second processing chip in the wind turbine generator control device. A second communication interface is located on the second processing chip. This second processing chip can be a microcontroller, MCU (Micro Controller Unit) chip, or the like.
[0073] The metering chip can be connected to the second processing chip through the first communication interface, and the second processing chip is connected to the second communication interface.
[0074] The converter control device is connected to the second communication interface on the wind turbine generator control device; the metering data output by the metering circuit can be sent to the second processing chip inside the wind turbine generator control device, and then the second processing chip sends the metering data to the converter control device. This method can also achieve the installation of one metering device, with multiple control devices obtaining the metering data.
[0075] There is another implementation method, see Figure 11 The metering circuit includes a metering chip 241 and a signal processing chip 242 that are interconnected; the metering chip is connected to a voltage sampling circuit and a current sampling circuit; the signal processing chip is connected to multiple communication interfaces. The signal processing chip can be a microcontroller, MCU chip, etc.
[0076] In this method, the metering chip receives the voltage signal output by the voltage sampling circuit and the current signal output by the current sampling circuit. It calculates metering data such as electricity and power based on the voltage and current signals, and sends this metering data to the signal processing chip. The signal processing chip then sends the metering data to the wind turbine generator control device through the first communication interface and to the converter control device through the second communication interface.
[0077] See Figure 12 This embodiment provides another metering device, in which the current sampling circuit is connected to the current signal interface of the converter control device, and the second communication interface is connected to the communication interface of the converter control device.
[0078] In this method, the converter can obtain the current signal through the second communication interface or through the current sampling circuit. In one implementation, the current data obtained through the second communication interface has higher accuracy, which can improve the power detection accuracy of the converter. Moreover, only one set of current transformer and current sampling circuit is used, which reduces the detection cost.
[0079] In addition, the converter control device directly obtains the current data sampled by the current sampling circuit through the current signal interface for the control and protection of the converter.
[0080] See Figure 13 This embodiment also provides a metering system, which includes a metering device 90 and a plurality of control devices 91; the plurality of communication interfaces in the metering device are respectively connected to the corresponding control devices.
[0081] In one specific manner, see Figure 14 The control device includes a wind turbine generator control device 911 and a converter control device 912; the wind turbine generator control device and the converter control device are communicatively connected.
[0082] In this approach, the wind turbine generator control device can obtain metering data from either the metering device or the converter control device; similarly, the converter control device can obtain metering data from either the metering device or the wind turbine generator control device.
[0083] See Figure 15 This embodiment also provides a converter, which includes the aforementioned metering device; the metering device is connected to the control system of the converter.
[0084] The converter control unit and the metering unit can achieve high-speed communication with high real-time performance. Power data calculated by the metering unit can be quickly transmitted to the converter control unit, enabling high-precision control of the converter's output power. The converter control unit can also update the wind turbine generator control unit with data collected from the metering unit.
[0085] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.
[0086] Furthermore, in the description of the embodiments of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0087] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.
[0088] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0089] Finally, it should be noted that the above embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The protection scope of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the technical scope disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be determined by the protection scope of the claims.
Claims
1. A metering device, characterized by The metering device comprises a voltage sampling device, a voltage sampling circuit, a current sampling device, a current sampling circuit and a metering circuit; The voltage sampling device is used for detecting the voltage of the line, and the current sampling device is used for detecting the current of the line; The voltage sampling device, the voltage sampling circuit and the metering circuit are connected in sequence; the current sampling device, the current sampling circuit and the metering circuit are connected in series; The metering circuit is provided with a plurality of communication interfaces, and the communication interfaces are used for connecting corresponding control devices.
2. The metering device of claim 1, wherein, The plurality of communication interfaces comprise a first communication interface and a second communication interface; the control devices comprise a wind turbine generator control device and a converter control device; The first communication interface is connected to the wind turbine generator control device, and the second communication interface is connected to the converter control device.
3. The metering device of claim 2, wherein, The metering circuit and the second communication interface are arranged in the converter control device; The first communication interface is arranged on the converter control device.
4. The metering device of claim 2, wherein, The metering circuit and the first communication interface are arranged in the wind turbine generator control device; The second communication interface is arranged on the wind turbine generator control device.
5. The gauge of claim 1, wherein, The metering circuit comprises a metering chip and a signal processing chip connected to each other; The metering chip is connected to the voltage sampling circuit and the current sampling circuit; and the signal processing chip is connected to the plurality of communication interfaces.
6. The metering device of claim 2, wherein, The metering circuit comprises a metering chip connected to a first processing chip in the converter control device, and the first communication interface is arranged on the first processing chip.
7. The gauge of claim 2, wherein, The metering circuit comprises a metering chip connected to a second processing chip in the wind turbine generator control device, and the second communication interface is arranged on the second processing chip.
8. The metering device of claim 2, wherein, The current sampling circuit is connected to a current signal interface of the converter control device.
9. A metrology system characterized by, The metering system comprises the metering device according to any one of claims 1-8, and further comprises a plurality of control devices; The plurality of communication interfaces in the metering device are respectively connected to corresponding control devices.
10. The metrology system of claim 9, wherein, The control devices comprise a wind turbine generator control device and a converter control device; The wind turbine generator control device is in communication connection with the converter control device.
11. A current transformer, characterized by The converter comprises the metering device according to any one of claims 1-8, and the metering device is connected to a control system of the converter.