Method for controlling a power converter, converter arrangement and computer program product

Abstract

To provide improved energy transfer and power converter control.SOLUTION: Determining a frequency control error, an active power target, a phase angle target, a voltage control error, a reactive power target, and an output voltage target, and controlling the power converter by the output voltage target and the phase angle target, determining an active power target independently of the frequency control error if a fault signal is detected, otherwise at least according to the frequency control error, determining a phase angle target independently of the active power target if a fault signal is detected, otherwise at least according to the active power target, determining a reactive power target independently of the voltage control error if a fault signal is detected, otherwise at least according to the voltage control error, and determining an output voltage target independently of the reactive power target if a fault signal is detected, otherwise at least according to the reactive power target.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Technical Field The present disclosure relates to a control method for a power converter, a converter apparatus, and a computer program product. [Background technology]

[0002] Background technology A power converter converts power from a first side of the power converter to a second side of the power converter, and in one example, from the second side to the first side. This ability to convert power from the first side to the second side and from the second side to the first side is called bidirectional. The first side of the power converter is coupled to, for example, a renewable energy source or a battery or other energy storage device. The second side is coupled to, for example, the grid.

[0003] Typically, power converters are single-phase or multi-phase voltage source converters (abbreviated VSCs). VSCs can be either current-controlled (abbreviated CC-VSC for current-controlled VSCs), where the AC current is the primary controlled variable, or voltage-controlled (abbreviated VC-VSC for voltage-controlled VSCs), where the AC voltage is the primary controlled variable. Hybrid-controlled VSCs also exist, where the primary controlled variables are a combination of AC current and AC voltage.

[0004] A synchronous generator (abbreviated as SG) is the primary power generating device in an electric power system. It consists of two parts: a prime mover and a synchronous machine. A prime mover is an energy conversion device that converts some form of energy, such as steam or natural gas, into rotational energy. A synchronous machine converts rotational energy into AC electrical energy.

[0005] The power grid is becoming more decentralized as more renewable energy sources (abbreviated RES), such as photovoltaic devices, and storage systems are integrated into the grid. These RES or storage systems use power converters to provide an interface for power or energy transfer between the energy source or storage system and the grid. As the proportion of renewable energy and asynchronous machine interface energy sources increases, the proportion of electricity generation supplied by traditional synchronous generators decreases, which results in an overall reduction in grid strength and stiffness.

[0006] SGs can exhibit partial or complete desynchronization during faults (grid, microgrid, and / or connected equipment faults), and partial desynchronization can result in greater power required after the fault to resynchronize the SG and return it to steady state. Complete desynchronization can result in "pole slip," in which the SG rotor slips one or more pole pairs and electrically reindexes one or more 360 ​​degrees from its original index position. This can result in large currents in both the generator and the power system, potentially causing the generator to trip or protective devices in the power system to trip.

[0007] One use of a VC-VSC is to create an AC electrical network or grid. Energy can come from an energy storage system or device, such as a battery, flywheel, or supercapacitor, or from an energy generating device, such as a generator or solar photovoltaic power plant, or even from another grid. A bidirectional VC-VSC can be used as a load (consuming energy from the grid) or as a generator (producing energy into the grid). This ability to generate and consume energy is called a VS C generates the grid, meaning that it can run as the only grid-forming device on the grid, i.e. standalone, or it can be used to stabilize the frequency or voltage of a grid formed by other devices.

[0008] In one example, VC-VSCs are implemented with a control system that allows them to look like or mimic a synchronous generator, for example, to allow standalone and parallel operation of the VSC, parallel operation with other sources such as synchronous generators, and parallel operation with the grid. A VSC operating in this manner can be called a virtual synchronous generator (VSG for short).

[0009] The paper, "Practical application of a complete virtual synchronous generator control method for microgrid and grid-edge applications," by A. Tuckey and S. Round, presented at the 19th IEEE Workshop on Control and Modeling of Power Electronics, Italy, June 25-28, 2018, describes the VSG.

[0010] VSGs, like SGs, can experience partial and complete desynchronization. In one example, during a fault, response can be improved by adaptively changing the characteristics of the function in real time, i.e., by adjusting parameters such as the inertia constant H, the gains Kp and Ki, and the maximum and minimum limits of the frequency regulator function.

[0011] Document EP 3376627 refers to a method and a control system for controlling a power converter.

[0012] However, while adjusting the inertia constant and governor gains and limits improves response, it is not sufficient to create a fully functioning, practical VSG with good fault response during and after a fault, and other control variations are required. Summary of the Invention [Problem to be solved by the invention]

[0013] Disclosure of the Invention It may be an object of the present invention to provide improved energy transfer and power converter control. [Means for solving the problem]

[0014] This object is solved by a method for controlling a power converter according to the features of claim 1. Further embodiments of the present invention relate to a converter apparatus and a computer program product for controlling a power converter.

[0015] According to one embodiment, a method for controlling a power converter comprises: determining a frequency control error as a function of at least the setpoint frequency and the actual frequency; determining an active power target; determining a phase angle target depending on at least an active power target; determining a voltage control error as a function of at least a setpoint voltage and an actual voltage; determining a reactive power target; determining an output voltage target in response to at least a reactive power target; - controlling the power converter based on the output voltage target and the phase angle target.

[0016] Furthermore, the method comprises: determining an active power target independently of the frequency control error if a fault signal indicative of a fault is detected, and otherwise determining the active power target as a function of at least the frequency control error; determining a phase angle target independently of the active power target if a fault signal indicative of a fault is detected, and otherwise determining a phase angle target depending at least on the active power target; - determining a reactive power target independently of the voltage control error if a fault signal indicative of a fault is detected, and otherwise determining the reactive power target as a function of at least the voltage control error; - determining the output voltage target independently of the reactive power target if a fault signal indicating a fault is detected, and otherwise determining the output voltage target depending on at least the reactive power target.

[0017] Advantageously, when a fault signal indicative of a fault is detected, at least one of the active power target, the phase angle target, the reactive power target, and the output voltage target is no longer determined as it would be if no fault signal indicative of a fault were detected, and when a fault signal indicative of a fault is detected, at least one of these values ​​is, for example, kept constant or determined in another manner to improve energy transfer and control of the power converter.

[0018] According to one embodiment, the method includes determining an initialization value for at least one of the real real power and the real reactive power of the power converter when a fault signal indicative of a fault is detected.

[0019] According to one embodiment, the method includes continuously storing data in a memory at a predetermined period, the data including at least one of real real power and real reactive power, and determining the initialization value includes selecting the initialization value from the data stored in the memory.

[0020] According to one embodiment, the method includes determining that the fault is no longer detected and determining an active power target using an initialization value of the real active power and / or determining a reactive power target using an initialization value of the real reactive power.

[0021] According to one embodiment, the method includes waiting a predetermined time after detecting that the fault is no longer detected before determining the active power target using the initialized value of the real active power and / or before determining the reactive power target using the initialized value of the real reactive power.

[0022] According to one embodiment, the method is configured to mimic a synchronous electrical generator. According to one embodiment, if no fault signal indicating a fault is detected, determining a phase angle target in response to at least the active power target comprises determining an active power error in response to at least the active power target and the actual active power, and determining a phase angle target in response to at least the active power error.

[0023] According to one embodiment, if a fault signal indicative of a fault is detected, determining the phase angle target independently of the active power target includes creating or keeping constant a target frequency.

[0024] According to one embodiment, if no fault signal indicative of a fault is detected, determining the output voltage target as a function of at least the reactive power target includes determining a reactive power error as a function of at least the reactive power target and the actual reactive power; and determining an output voltage target as a function of at least the reactive power error. and determining a pressure target.

[0025] According to one embodiment, if a fault signal indicative of a fault is detected, determining the output voltage target independently of the reactive power target comprises keeping the output voltage target constant.

[0026] In the context of the following disclosure, the term function refers to a set or group of one or more functions based on executable program code, such as, for example, lines of program code, function blocks, functional subroutines and / or procedures. The term function is used to facilitate understanding of the method. In possible realizations of the method, different functions can be combined into one function.

[0027] According to further embodiments, the steps of determining a frequency control error and determining an active power target are performed by a frequency regulator function. The steps of determining an internal frequency and phase angle target are performed by an inertia function. The steps of determining a voltage control error and determining a reactive power target are performed by an automatic voltage regulation function. The steps of determining an output voltage target are performed by a rotor flux function. The steps of controlling the power converter based on the output voltage target and the phase angle target are performed by a transformation function. Optionally, these functions are combined. The functions can be written in separate blocks of program code, or in combined blocks of program code, or in one block of program code.

[0028] In one example, when operating at steady state, the frequency setpoint value and voltage setpoint value are constant, the frequency control error is zero, the active power target is equal to the actual active power, the voltage control error is zero, and the reactive power target is equal to the actual reactive power.

[0029] In one example, during a fault, the real active power and real reactive power may vary from their steady-state values. The real voltage and real frequency may also vary from their steady-state values. These variations in real active power, real reactive power, real voltage, and real frequency contribute to desynchronization of the VSG during a fault.

[0030] In yet a further embodiment, the method suspends execution of at least one of a frequency regulator function, an automatic voltage regulator function, a rotor flux function, and an inertia function, for example, when a fault signal indicating a fault is detected. Suspending a frequency regulator function, an automatic voltage regulator function, or a rotor flux function means that execution of the algorithm or function is suspended and the output is one of fixed, locked, remains constant, and frozen. For an inertia function, suspending means that execution of the algorithm or function is suspended, the frequency is one of fixed, locked, remains constant, and frozen, and the angle continues to progress.

[0031] In further embodiments, the constant output may be the value taken at the time the fault occurred, or may be some other value.

[0032] According to a further embodiment, advantageously, at least one of the frequency regulator function, the automatic voltage regulator function, the inertia frequency function, and the rotor flux function is suspended and the respective output is held constant until after the fault signal indicates that there is no fault. Thus, the output value of this function, which is the input value of the downstream function or transformation, is constant. Therefore, the downstream function or transformation can operate reliably and / or predictably even in the event of a fault.

[0033] According to a further embodiment, the execution of only one of the functions is suspended, the other functions operating independently of the value of the fault signal.

[0034] According to a further embodiment, the execution of two functions is suspended, while the other functions operate independently of the value of the fault signal.

[0035] According to a further embodiment, the execution of three functions is suspended: the other functions operate independently of the value of the fault signal.

[0036] According to a further embodiment, the execution of all four functions is suspended. In a further embodiment, the method is performed online, particularly when connected to a grid, and / or is performed in real time.

[0037] According to one embodiment, a converter device includes a controller and a power converter implemented as a voltage-controlled voltage-source converter. The controller is configured to perform the method described herein. In one example, the power converter is configured to be connected to a grid and an energy source / load device.

[0038] According to one embodiment, a computer program product includes instructions for causing a controller to perform a method for controlling a power converter.

[0039] The above-described power converter control method and computer program product are suitable for, for example, a converter device, and therefore the features and advantages described in relation to the converter device and the computer program product can be used for the method, and vice versa.

[0040] In one example, the fault is an unintentional or accidental short circuit or partial short circuit in the grid, the equipment connecting the converter to the grid, such as a tie wire or circuit breaker or transformer, or the power converter itself. Three-phase AC systems have eight different types of short circuits: (1) three-phase low-impedance short circuit, (2) phase-to-phase low-impedance short circuit, (3) phase-to-ground low-impedance short circuit, (4) phase-to-ground low-impedance short circuit, (5) three-phase high-impedance short circuit, (6) phase-to-ground high-impedance short circuit, (7) phase-to-ground high-impedance short circuit, and (8) phase-to-ground high-impedance short circuit. One-phase AC systems have two different types of short circuits: (1) phase-to-ground low-impedance short circuit, and (2) phase-to-ground high-impedance short circuit. Because the neutral is connected to ground, either directly or through an impedance, depending on the situation, a ground fault is synonymous with a neutral-to-ground fault. Many phenomena can cause faults. Examples include cables of different phases accidentally touching each other, animals forming conductive paths between phases or between one or more phases and ground, or between one or more phases and the neutral, insulation failure, a transformer or circuit breaker or other equipment fire, lightning strikes creating an arc that causes a fault, and many more.

[0041] In one example, an overload, which is a load that exceeds the converter's rating, typically causes excessive converter current. A slight overload does not cause the converter's output voltage to drop excessively, but a severe overload does. Faults, particularly low-impedance faults, have a similar effect on the converter as a severe overload, i.e., excessive converter current and a drop in output voltage. In one example, a method for detecting a fault may be to determine whether the converter current is excessive and the converter output voltage is dropping. In another example, a circuit breaker or fault relay may be used to detect the fault. In a further example, an upstream device may be used to detect the fault. When a fault is detected using one or another of the exemplary methods, the status of a fault variable or fault signal may be changed. Thus, the fault signal may be configured to indicate a fault or to indicate no fault.

[0042] In one example, the term "determining a parameter depending on another parameter" refers to a controller that uses, for example, a control loop, a look-up table, fuzzy logic, a model, and an observer. "The term 'parameter' means to include at least one of a parameter server, or another item implemented in hardware, software, or a combination of hardware / software that performs a decision process. The word has the meaning that the parameter may optionally also depend on further parameters."

[0043] In one example, the real frequency, real voltage, real real power, and real reactive power are values ​​of a power converter.

[0044] In one example, the real frequency, real voltage, real active power, and real reactive power are measured or sensed, for example, within the power converter, at the terminals of the power converter, or elsewhere. For example, one of two or more of these values ​​is measured or sensed at the terminals of a second side of the power converter, the second side being connected, for example, to the grid.

[0045] In one example, a method and controller for controlling a power converter is configured to improve power converter response during grid disturbances. The controller may be referred to as a control system.

[0046] The present disclosure includes several embodiments of converter apparatus and methods for controlling power converters. All features described with respect to one of the embodiments are also disclosed herein with respect to the other embodiments, even if the respective feature is not explicitly mentioned in the context of a particular embodiment.

[0047] BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding. In the drawings, elements of the same structure and / or function may be referred to by the same reference numerals. It should be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale. [Brief explanation of the drawings]

[0048] [Figure 1] 1A-1D are schematic diagrams of a transducer device according to different embodiments; [Figure 2] 1A-1D are schematic diagrams of a transducer device according to different embodiments; [Figure 3A] 1 is a schematic diagram of a method for controlling a power converter according to different embodiments; [Figure 3B] 1 is a schematic diagram of a method for controlling a power converter according to different embodiments; DETAILED DESCRIPTION OF THE INVENTION

[0049] Best Mode for Carrying Out the Invention FIG. 1 is a schematic diagram of a converter apparatus 10 according to one embodiment. The converter apparatus 10 comprises a controller 12 and a power converter 11. The power converter 11 is realized as a voltage-controlled voltage-source converter. The power converter 11 is configured to be connected to a grid 13 and an energy source / load device 14. The source / load device 14 is realized, for example, as a renewable energy source (abbreviated as RES), an energy storage device, or another grid. The controller 12 is configured to execute a method for controlling the power converter 11. The controller 12 includes at least one of a computer, a microprocessor, a microcontroller, and a field programmable gate array, abbreviated as FPGA. The controller 12 comprises a memory 16 and, optionally, an initialization value memory 15.

[0050] The computer program product 17 includes instructions for causing the controller 12 to perform a method for controlling the power converter 11 .

[0051] In one example, the method includes at least the following executable functions: a frequency regulator function 21, an inertia function 22, an automatic voltage regulator function 23, and a rotor flux function 24. The method mimics a synchronous generator. The frequency regulator function 21, the inertia function 22, the automatic voltage regulator function 23, and the rotor flux function 24 mimic a synchronous generator. The method can be implemented, for example, by a transformation function 2 5. The controller 12 implements, for example, a frequency regulator function 21, an inertia function 22, an automatic voltage regulator function 23, a rotor flux function 24, and a transformation function 25 using a computer program product 17. The functions may also be referred to as modules or blocks. Typically, the functions are implemented by software and / or hardware.

[0052] One aspect that both synchronous generators and VSGs exhibit is partial or complete desynchronization during a fault (grid or microgrid fault). Partial desynchronization results in a large amount of power (called resynchronization power or resynchronization torque) required after the fault to resynchronize the synchronous generator or VSG and return it to a steady state. Utility regulators and standards limit this resynchronization power, requiring, for example, 95% of its pre-fault value within 100 ms. Complete desynchronization results in a "pole slip" in which the synchronous generator rotor slips one or more pole pairs and electrically reindexes one or more 360 ​​degrees from its original index position. This causes large currents to flow in both the generator and the power system, potentially tripping the generator or tripping protective devices in the power system.

[0053] A VSG can experience partial and complete desynchronization, similar to a synchronous generator. The power converter 11 operates as a VSG. VSG operation during a fault can be achieved as described in Figures 2, 3A, and 3B.

[0054] FIG. 2 is a schematic diagram of a converter device 10 according to an embodiment that is a further development of the embodiment shown in FIG. 1. In this disclosure, the terms "magnetic flux" and "back EMF" can be used interchangeably, as they are similar in a VSG. The use of "hold," "freeze," and "lock" are interchangeable but can refer to different things. The virtual inertial frequency f can be frozen or locked (e.g., the virtual inertial frequency f remains the same), but the operation of the frequency regulator function 21 is held or locked, meaning it remains inactive.

[0055] Broadly speaking, the method for controlling the power converter 11 is configured to lock, freeze, or hold the operation of four of five control components: the SG rotor flux model, the automatic voltage regulator (AVR), the inertia, and the speed / frequency regulator. Thus, at least one of the frequency regulator function 21, the inertia function 22, the automatic voltage regulator function 23, and the rotor flux function 24 is held, locked, or frozen. The conversion function 25 (the fifth control component) is not frozen, locked, or held. Advantageously, the method reduces, avoids, or prevents partial / full desynchronization during a VSG fault.

[0056] The method takes a snapshot of the VSG's real active power P_act and real reactive power Q_act at or shortly before the fault is detected. The real active power P_act can be referred to as output active power or real power. The real reactive power Q_act can be referred to as output reactive power or reactive power. During fault shutdown, these stored values ​​of real active power P_act and real reactive power Q_act (which are no longer "actual" values ​​but are pre-fault values) are used as initialization values. Additionally, the rotor flux and virtual inertia frequency f values ​​are locked or frozen, or close to locked or frozen, and / or their parameters are adjusted at or shortly before the fault is detected. Furthermore, operation of the frequency regulator function 21 and the AVR function 23 is stopped upon fault detection, meaning their outputs are locked or frozen. Doing the above means that during the fault, the flux / back EMF and virtual inertia remain synchronized with the grid, and the excitation and regulator power remain unchanged.

[0057] Upon or immediately after the fault ceases, the flux / back EMF and inertia are unfrozen and their parameters are restored to their normal values ​​(if they have been changed). Additionally, the frequency regulator function 21 and the AVR function 23 are initialized with snapshots of the real power P_act and the reactive power Q_act, respectively, and their operation is resumed. This reduces resynchronization power and quickly achieves operation close to the pre-fault steady state. Once the fault is cleared, the power converter 10 is configured to immediately return to steady state. Therefore, the initialization value of the real reactive power Q_act is used to initialize the AVR function 23 and / or the initialization value of the real real power P_act is used to initialize the frequency regulator function 21.

[0058] The operation of the control device 12 is explained below using Figures 3A and 3B. FIG. 3A is a schematic diagram of a method for controlling a power converter 11 according to an embodiment that is a further development of the embodiment shown in FIGS.

[0059] The method for controlling the power converter 11 includes: - determining a frequency control error Ferr as a function of the setpoint frequency FSet and the actual frequency F_act of the power converter 11 (process 71); - determining an active power target PSet by the frequency regulator function 21 as a function of the frequency control error Ferr (process 72); - determining a phase angle target Φ according to the active power target PSet by the inertia function 22 (process 73); - determining a voltage control error Verr as a function of the setpoint voltage VSet and the actual voltage V_act provided by the power converter 11 (process 74); - determining a reactive power target Exc according to the voltage control error Verr by the AVR function 23 (process 75); - determining the output voltage target Vd* as a function of the rotor flux function 24 in response to the reactive power target Exc (process 76); - controlling the power converter 11 based on the output voltage target Vd* and the phase angle target Φ (process 77).

[0060] The above-described processes 71 to 77 are performed during normal operation (non-fault times) of the power converter 11. During normal operation, the power converter 10 is in steady state. Therefore, the voltage control error Verr and the frequency control error Ferr are zero or near zero before the fault.

[0061] Furthermore, the method comprises: - modifying the fault signal SF after detecting the fault (process 78) so that the fault signal SF indicates a fault; - Suspending at least one of the frequency regulator function 21, the inertia function 22, the automatic voltage regulator function 23 and the rotor flux function 24 (process 79) so that the at least one suspended function provides a constant value at its output.

[0062] Some of the processes can be performed in parallel. For example, processes 71 to 73 can be parallel to processes 74 to 76. Process 79 follows process 78.

[0063] The occurrence of a fault is detected using the method or process. The fault signal SF indicates a fault (e.g., is set to a first logic value), for example, when the current limit of the power converter 11 is reached with the terminal voltage inhibited, or another of the above-mentioned conditions is detected. When a fault is detected, the fault signal SF indicates a fault (e.g., acquires a first logic value). This allows the fault signal SF to be detected when a fault is detected. In other words, the fault signal SF is emitted and is "high" or "true" or "active" or "up" The fault signal SF is used throughout the control scheme to indicate the "fault" value.

[0064] When the fault has stopped, known as being "cleared", the fault signal SF indicates the absence of a fault (e.g., acquires a second logical value). In other words, the fault signal SF is weakened and indicates a "low" or "inactive" or "false" value. To improve the recovery of the pre-fault active power and pre-fault reactive power, the method may, for example, introduce a short predetermined delay between the fault being cleared and the weakened fault signal SF. The second logical value of the fault signal SF indicates the absence of a fault.

[0065] This causes process 78 to detect a fault and issue a fault signal SF. In process 79, while the fault signal SF indicates a fault (the fault signal SF is active), operation of the frequency regulator function 21 is suspended and the output of the frequency regulator function 21, i.e., the active power target PSet, is at a constant value. Thus, freezing prevents integrators or other controller types from winding up. The frequency regulator function 21 includes a frequency controller 113 (also called an FCtrl function or regulator frequency controller). The frequency controller 113 may be, for example, a P, PI, or PID controller. P controller stands for Proportional Controller, and PI stands for Proportional-Integral Controller. PID stands for Proportional-Integral-Derivative Controller. The frequency controller 113 includes a freeze control input 103 to which the fault signal SF is applied. When a fault signal SF indicating a fault is applied to the frequency controller 113 (via the freeze control input 103), the frequency controller 113 provides a constant value for the active power target PSet, e.g., independent of the frequency control error Ferr. The constant value is the value of the active power target PSet before the fault signal SF changes so that it indicates a fault.

[0066] If the fault signal SF changes, indicating that there is no current fault, the previous initialization value of the actual active power P_act is applied to the frequency controller 113 from the memory 16 or the initialization value memory 15. In this way, the frequency regulator function 21 can be initialized if it was previously suspended.

[0067] Furthermore, while the fault signal SF indicates a fault, operation of the AVR function 23 is suspended, and the output of the AVR function 23, i.e., the reactive power target Exc, is a constant value. This prevents winding of an integrator or other controller type. The AVR function 23 includes a voltage controller 115 (also referred to as a VCtrl function). The voltage controller 115 may be, for example, a P, PI, or PID controller. The voltage controller 115 includes a freeze control input 108 to which the fault signal SF is applied. When the fault signal SF indicating a fault is applied to the voltage controller 115 (via the freeze control input 108), the voltage controller 115 provides a constant value for the reactive power target Exc, independent of, for example, the voltage control error Verr. The constant value is the value of the reactive power target Exc before the fault signal SF changes so that the fault signal SF indicates a fault.

[0068] If the fault signal SF changes, indicating that there is no current fault, the previous initialization value of the actual reactive power Q_act is applied to the voltage controller 115 from the memory 16 or the initialization value memory 15. In this way, the AVR function 23 can be initialized if it was previously interrupted.

[0069] Figure 3B is a schematic diagram of a method for controlling a power converter according to an embodiment that is a further development of the embodiment shown in Figures 1, 2 and 3A. The method includes a step (process 80) of storing an initialization value of at least one of the power P_act and the real reactive power Q_act in the initialization value memory 15. The value is stored in the initialization value memory 15 when the fault signal SF changes and indicates a fault after the change, or after or before the fault signal SF is set to indicate a fault. For example, the initialization value of the real real power P_act is stored in the S / H memory 102. The initialization value of the real reactive power Q_act is stored in the S / H memory 107.

[0070] In one example, the method includes a step of storing data of the power converter 11 in the memory 16 at a predetermined period. The step of storing an initialization value of at least one of the actual active power P_act and the actual reactive power Q_act of the power converter 11 in the initialization value memory 15 includes a step of selecting at least one value from the data stored in the memory 16 and storing the selected value in the initialization value memory 15. The memory 16 is implemented as, for example, a circular buffer. The memory 16 is configured as, for example, a data logger. The memory 16 stores a history of data of at least one of the actual active power P_act and the actual reactive power Q_act.

[0071] Alternatively, the initialization value of at least one of the actual active power P_act and the actual reactive power Q_act of the power converter 11 is directly fetched from the memory 16. In this case, the initialization value memory 15 can be omitted.

[0072] When the fault signal SF changes such that it indicates a fault, a snapshot of the real active power P_act and / or real reactive power Q_act being supplied by the VSG is stored in the memory 16 and / or the initialization value memory 15. The real active power P_act and / or real reactive power Q_act are values ​​measured by the power converter 11. The initialization value memory 15 includes, for example, a sample-and-hold memory 102 (abbreviated as S / H memory) and a further S / H memory 107. This is indicated by a rising edge trigger of the S / H memories 102, 107. Thus, the real active power P_act and / or real reactive power Q_act are stored in the initialization value memory 15, for example, at the rising edge of the fault signal SF. The stored value or values ​​may be at or slightly earlier than the instance of the fault signal SF to ensure that the appropriate steady-state values ​​are stored. This is achieved, for example, by the circular buffer in the memory 16 mentioned above.

[0073] The controller 12 is implemented such that the frequency regulator function 21, the inertia function 22, the AVR function 23, and the rotor flux function 24 are configured to mimic a synchronous generator.

[0074] In the following, the process of the control device 12 before a fault is described. If the fault signal SF indicates that there is no fault, the step of determining the phase angle target Φ according to the active power target PSet by the inertia function 22 is: determining an active power error Perr as a function of the inertia function 22 depending on the active power target PSet and the actual active power P_act; determining a phase angle target Φ as a function of the active power error Perr by means of an inertia function 22.

[0075] The active power target PSet is provided at the output of the frequency regulator function 21. The active power error Perr is generated by a subtractor 40 of the inertia function 22, which receives the active power target PSet and the actual active power P_act as inputs. The phase angle target Φ is generated by an integrator 41 of the inertia function 22 in response to at least the target frequency f. The target frequency f is generated by an inertia controller 42 of the inertia function 22. The inertia controller 42 receives the active power error Perr. The inertia controller 42 is realized, for example, as a PI controller. The inertia controller 42 includes, for example, a parameter KH / S in a forward branch and a parameter Kd in a feedback branch. Alternatively, the inertia controller 42 may be implemented, for example, as a PID controller. controller or otherwise implemented.

[0076] In frequency regulator function 21, the setpoint frequency FSet and the actual active power P_act are provided to a first subtraction unit 43 of frequency regulator function 21. The actual active power P_act is corrected by a frequency droop function 44 of frequency regulator function 21. A frequency error Ferr is generated by a second subtraction unit 45 of frequency regulator function 21 in response to at least the actual frequency F_act and the output of first subtraction unit 43. An active power target PSet is generated by a frequency controller 113 in response to at least the frequency control error Ferr.

[0077] In the AVR function 23, the setpoint voltage VSet and the actual reactive power Q_act are provided to a first subtraction unit 46 of the AVR function 23. The actual reactive power Q_act is corrected by a voltage droop function 47 of the AVR function 23. A voltage control error Verr is generated by a second subtraction unit 48 of the AVR function 23 in response to at least the actual voltage V_act and the output of the first subtraction unit 46. A reactive power target Exc is generated by a voltage controller 115 in response to at least the voltage control error Verr.

[0078] If the fault signal SF indicates that there is no fault, determining the output voltage target Vd* by the rotor flux function 24 as a function of at least the reactive power target Exc comprises: determining a reactive power error Qerr in response to at least the reactive power target Exc and the actual reactive power Qact; - determining an output voltage target Vd* in response to at least the reactive power error Qerr.

[0079] The reactive power error Qerr is provided by a subtraction unit 49 of the rotor flux function 24 in response to at least the reactive power target Exc and the actual reactive power Q_act. The rotor flux function 24 includes a flux controller 52, which may be referred to as a flux model controller. The flux controller 52 is realized, for example, as an integrator with a parameter Kψ or as a PI or PID controller. The flux controller 52 generates an output voltage target Vd* in response to at least the reactive power error Qerr.

[0080] The transformation function 25 includes first and second transforms 53, 54. The first transform 53 receives the phase angle target Φ and the voltage target Vd* (or a quantity |Ea| derived from the voltage target Vd*) and generates a vector signal Ea. The transformation function 25 includes a virtual impedance 55. A subtraction unit 56 of the transformation function 25 provides a further vector signal Va in response to at least the output of the first transformer 53 and the output of the virtual impedance 55. The second transform 53 receives the output of the subtraction unit 56 and generates a signal that is provided to the power converter 11.

[0081] In the case of a fault, at least some of the following processes are performed: If the fault signal SF is set such that it indicates a fault, the step of determining the phase angle target Φ by the inertia function 22 as a function of at least the active power target PSet may (for example additionally) include: - adjusting at least the parameters of the inertial function 22, and - freezing the internal signals of at least the inertial function 22 (process 81).

[0082] Examples of at least parameters of the inertia function 22 being adjusted are the parameter KH / S in the forward branch and the parameter Kd in the feedback branch of the inertia controller 42. Examples of at least internal signals of the inertia function 22 are the target frequency f, the signal at the output of a feedback divider having the parameter Kd, or other internal signals.

[0083] In one example, when a fault signal SF indicative of a fault is detected, determining the phase angle target Φ independently of the active power target PSet includes, for example, keeping the target frequency f constant at a value at or shortly before the time when the fault signal SF indicative of a fault is detected.

[0084] While the fault signal SF indicates a fault (is active), the following actions are taken depending on the operation of the switch device 104: The parameters of the virtual inertial model can be changed or adjusted, - Values ​​internal to the virtual inertial model are frozen, which freezes the output or target frequency f and therefore ensures that the VSG remains synchronized to the grid 13.

[0085] When the first switch 104′ of the switch device 104 is set to a conductive state, the fault signal SF is provided to the first control input 105 of the inertia controller 42 to trigger at least a parameter modification. When the second switch 104″ of the switch device 104 is set to a conductive state, the fault signal SF is provided to the second control input 106 of the inertia controller 42 to trigger at least a parameter modification and the fault signal SF is provided to the second control input 106 of the inertia controller 42 to trigger at least a value of the inertia function 22 to be frozen. When the first switch 104′ is set to a conductive state and the second switch 104″ is set to a conductive state, the fault signal SF is provided to the first control input 105 of the inertia controller 42 to trigger at least a parameter modification and the fault signal SF is provided to the second control input 106 of the inertia controller 42 to trigger at least a value of the inertia function 22 to be frozen.

[0086] If the fault signal SF is set such that it indicates a fault, the step of determining the output voltage target Vd* by the rotor flux function 24 as a function of at least the reactive power target Exc comprises: - adjusting at least parameters of the rotor flux function 24, and - freezing the signal of at least the rotor flux function 24 (process 82). The signal can be an internal signal or the output voltage target Vd*.

[0087] In one example, when a fault signal SF indicating a fault is detected, the output voltage target Vd* is held constant, for example, at a value at or shortly before the fault signal indicating a fault is detected.

[0088] While the fault signal SF indicating a fault is detected or active, depending on the operation of the further switch device 109, the following actions may be taken: -The parameters of the magnetic flux model can be changed or adjusted, - Values ​​internal to the flux model are frozen, which freezes the output voltage target Vd* and therefore ensures that the VSG remains synchronized to the grid 13.

[0089] If the first switch 109′ of the further switching device 109 is set to a conducting state, the fault signal SF is provided to a first control input 110 of the flux controller 52 to trigger at least a parameter to be modified. If the second switch 109″ of the further switching device 109 is set to a conducting state, the fault signal SF is provided to a second control input 111 of the flux controller 52 to trigger at least a parameter to be modified and the fault signal SF is provided to a second control input 111 of the flux controller 52 to trigger at least a parameter to be modified and the fault signal SF is provided to a second control input 111 of the flux controller 52 to freeze at least a value of the rotor flux function 24. Triggers the system to at least freeze the value.

[0090] The switch device 104 and further switch devices may be realized using logic, software, or transistors to implement the switches 104', 104'', 109', 109''.

[0091] Furthermore, the method comprises: - determining that the fault is no longer detected after modifying the fault signal SF so that it indicates a fault; - modifying the fault signal SF so that it indicates no fault; - initializing at least one reserved function (process 83).

[0092] Thus, at least one or both of frequency regulator function 21 and automatic voltage regulator 23 are activated from a reserved state (which may be referred to as non-frozen) and initialized. Initializing the at least one frozen function includes providing the at least one reserved function with an initialization value of at least one parameter stored in initialization value memory 15 and / or memory 16.

[0093] Optionally, the step of modifying the fault signal SF such that it indicates no fault comprises waiting a predetermined time after detecting that the fault is no longer detected before modifying the fault signal SF.

[0094] The following describes an example of the actions or processes that occur when a fault is cleared: the fault is no longer detected, the fault signal SF indicates the absence of a fault (i.e., the fault signal SF drops) when or shortly after the fault is no longer detected.

[0095] 1. When the fault signal SF drops, the active power snapshot stored in the S / H memory 102 is used to initialize the frequency controller 113 by the fault signal SF on the reset line 112 dropping, which is indicated by a falling edge trigger of the frequency controller 113.

[0096] 2. Since the fault signal SF indicates that there is no fault (the fault signal SF is currently inactive), operation of the frequency controller 113 is activated (e.g., unfreeze), allowing the frequency controller 113 and frequency regulator function 21 to operate normally. This is achieved by providing the fault signal SF, indicating that there is no fault, to the freeze control input 103.

[0097] 3. The fault signal SF now indicates that there is no fault, so both of the following actions occur:

[0098] Returning the parameters of the inertia controller 42 implementing the virtual inertial model to their original values. This results from providing a fault signal SF to the first control input 105 indicating the absence of a fault.

[0099] b. The internal values ​​of the inertia controller 42 implementing the virtual inertial model are not frozen. This is achieved by providing a fault signal SF to the second control input 106 indicating the absence of a fault.

[0100] 4. When the fault signal SF drops, the reactive power sample stored in the further S / H memory 107 is The snapshot is used to initialize the AVR voltage controller 115 by lowering the fault signal SF on the reset line 114, which occurs on the falling edge of the fault signal SF.

[0101] 5. Now, the fault signal SF indicates that there is no fault, so operation of the AVR voltage controller 115 is activated (e.g., unfreeze), allowing the voltage controller 115 and AVR function 23 to operate normally. This results from providing the fault signal SF, indicating that there is no fault, to the freeze control input 108.

[0102] 6. The fault signal SF now indicates that there is no fault, so both of the following actions occur:

[0103] Returning the parameters of the flux model to their original values: This is achieved by providing a fault signal SF to the first control input 110 of the flux controller 52, indicating that there is no fault.

[0104] b. The internal values ​​of the flux controller 52 are unfrozen. This results from providing a fault signal SF to the second control input 111 of the flux controller 52, indicating that there is no fault.

[0105] After actions 1 through 6 above have occurred, the converter device 10 continues to operate normally. When the fault signal SF drops, an initialization value for the real reactive power Q_act is also optionally applied to the voltage droop function 47. An initialization value for the real real power P_act is also optionally applied to the frequency droop function 44.

[0106] While the present disclosure is susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and have been described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure as defined by the appended claims.

[0107] The embodiments shown in Figures 1-3B above represent exemplary embodiments of the improved converter apparatus and control method. As such, they do not constitute an exhaustive list of all embodiments of the improved converter apparatus and method. Actual apparatus and methods may differ from the illustrated embodiments, for example, with respect to apparatus, devices, and signals. [Explanation of symbols]

[0108] Reference sign 10. Converter device 11 Power Converter 12 Control device 13 Grid 14 Energy / Load Device 15 Initialization Value Memory 16 memory 21 Frequency regulator function 22 Inertia function 23 Automatic voltage regulator function 24 Rotor flux function 25 Conversion Function 40 Subtraction Unit 41 Integrator 42 Inertial Controller 43, 45 subtraction unit 44 Frequency droop function 46, 48, 49 Subtraction Units 47 Voltage droop function 52 Magnetic Flux Controller 53, 54 Conversion 55 Virtual Impedance 56 Subtraction Unit 71~83 Process 102 sample and hold memories 103 Freeze control input 104 Switching Device 104', 104'' switch 105, 106 Control input 107 Sample and hold memory 108 Freeze control input 112 Reset input 113 Frequency Controller 108 Control Input 109 Further Switching Devices 109', 109'' switch 110, 111 Control input 114 Reset Input 115 Voltage Controller EA Vector Signals Exc reactive power target f target frequency Ferr frequency control error FSet Setpoint frequency F_act Actual frequency Perr Active Power Error PSet Active Power Target P_act Actual active power Qerr Reactive power error Q_act Actual reactive power SF Fault Signal Va Further Vector Signals Vd* Output voltage target Verr Voltage control error VSet Set point voltage V_act actual voltage Φ Phase angle target

Claims

1. A method for controlling a power converter (11), comprising: - determining a frequency control error (Ferr) as a function of at least the setpoint frequency (FSet) and the actual frequency (F_act); - determining an active power target (PSet); - determining a phase angle target (Φ); - determining a voltage control error (Verr) as a function of at least the set point voltage (VSet) and the actual voltage (V_act); - determining a reactive power target (Exc); - determining an output voltage target (Vd*); - controlling the power converter (11) based on the output voltage target (Vd*) and the phase angle target (Φ), The method comprises: determining the active power target (PSet) independently of the frequency control error (Ferr) if a fault signal (SF) indicating a fault is detected, and otherwise determining the active power target (PSet) as a function of at least the frequency control error (Ferr); determining the phase angle target (Φ) independently of the active power target (PSet) when a fault signal (SF) indicating a fault is detected, and otherwise determining the phase angle target (Φ) in accordance with at least the active power target (PSet); determining said reactive power target (Exc) independently of the voltage control error (Verr) if a fault signal (SF) indicating a fault is detected, and otherwise determining said reactive power target (Exc) depending at least on the voltage control error (Verr); - determining the output voltage target (Vd*) independently of the reactive power target (Exc) if a fault signal (SF) indicating a fault is detected, and otherwise determining the output voltage target (Vd*) depending on at least the reactive power target (Exc).

2. determining an initialization value for at least one of an actual active power (P_act) and an actual reactive power (Q_act) of the power converter (11) when the fault signal (SF) indicating a fault is detected; The method of claim 1.

3. continuously storing data in a memory (16) at predetermined intervals; the data includes at least one of the actual active power (P_act) and the actual reactive power (Q_act); determining the initialization value includes selecting the initialization value from the data stored in the memory (16); The method of claim 2.

4. - determining that said fault is no longer detected; - determining the active power target (P Set) using an initialization value of the actual active power (P_act) and / or determining the reactive power target (Exc) using the initialization value of the actual reactive power (Q_act); Including, The method according to claim 2 or 3.

5. determining the active power target (P Set) using the initialized value of the actual active power (P_act) after detecting that the fault is no longer detected; and / or and waiting a predetermined time before determining the reactive power target (Exc) using the initialized value of the actual reactive power (Q_act). The method of claim 4.

6. configured to mimic a synchronous generator; The method according to any one of claims 1 to 5.

7. When a fault signal (SF) indicating a fault is not detected, the step of determining the phase angle target (Φ) in response to at least the active power target (P Set) comprises: - determining an active power error (Perr) depending on at least said active power target (PSet) and the actual active power (P_act); - determining the phase angle target (Φ) as a function of at least the active power error (Perr), The method according to any one of claims 1 to 6.

8. When the fault signal (SF) indicating a fault is detected, determining the phase angle target (Φ) independently of the active power target (P Set) includes keeping the target frequency (f) constant. The method according to any one of claims 1 to 7.

9. When a fault signal (SF) indicating a fault is not detected, the step of determining the output voltage target (Vd*) in accordance with at least the reactive power target (Exc) comprises: - determining a reactive power error (Qerr) depending on at least said reactive power target (Exc) and actual reactive power (Q_act); - determining the output voltage target (Vd*) in response to at least the reactive power error (Qerr), The method according to any one of claims 1 to 8.

10. When a fault signal (SF) indicating a fault is detected, determining the output voltage target (Vd*) independently of the reactive power target (Exc) includes keeping the output voltage target (Vd*) constant. The method according to any one of claims 1 to 9.

11. A transducer device (10), comprising: a control device (12), a power converter (11) realized as a voltage-controlled voltage source converter, A converter device (10) wherein the control device (12) is configured to perform a method for controlling the power converter (11) according to any one of claims 1 to 10.

12. A computer program product comprising instructions for causing the control device (12) of claim 11 to perform the method for controlling the power converter (11) of any one of claims 1 to 10.

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