Improved converter bridge controller

Abstract

An improved converter bridge controller. A converter bridge controller (200) is provided for power converter hardware (268) connectable to an AC power network (260). The controller (200) includes an output unit (102) configured to generate a quadrature voltage component reference (126) to a PWM modulator (106) that determines the switching of the power converter hardware (268), wherein the quadrature voltage component reference (126) includes a first signal (108) and a second signal (110). The output unit (102) includes a first component (112) and a second component. The first component (112) is configured to generate the first signal (108) based on a current reference (116) of the active current to be generated by the power converter hardware (268). The second component is configured to provide a second signal (110) to reduce the difference between the measured converter active current component (118) of the feedback current and the current reference (116) of the active current.

Description

Technical Field

[0001] The present invention relates to the field of controller devices for controlling power converter hardware and methods for operating such controller devices. Background Technology

[0002] Many wind turbines or photovoltaic systems use closed-loop current control, closed-loop vector current control, or variable dual-vector current control for their current power converters. These control systems do not inherently provide the characteristics necessary to function as AC systems in a manner similar to that of synchronous machines.

[0003] For example, if the AC system frequency (i.e., the AC power network, such as a grid or islanded power network) drops, for example, due to losses at a large power plant, the AC system frequency supplied by a conventional current-controlled power converter decreases transiently and thus maintains a constant power transfer. In contrast, a synchronous generator with a large rotating mass cannot change its rotational speed instantaneously, and therefore an angular error occurs between the generator's anti-electromagnetic force (EMF) and the AC system. This results in an increased power flow from the synchronous generator to the power system. This transient power flow draws energy from the generator's rotating mass and transfers it to the AC system, thus providing "inertia" to the AC system. Conversely, when a large load is removed from the power system, the system frequency increases, and current control again does not respond to this (and does not function to maintain a constant power flow). In contrast, the synchronous generator will function to maintain its pre-event rotational speed and thus transiently input power.

[0004] EP 2221936 B2 discloses a system and method for controlling a grid-connected power generation system, the system including a wind turbine, a converter, a first controller, and a second controller. The wind turbine supplies electrical power to the grid, and the converter couples the wind turbine to the grid. The first controller calculates a voltage command to simulate the phasor back electromotive force behind an inductor. The controller further generates a converter switching command based on the voltage command. The voltage command includes a voltage amplitude reference and an internal frequency reference, which is calculated based on the power imbalance between an active power reference and the electrical power. The second controller limits the converter current. Summary of the Invention

[0005] In view of the above, there is a need for improved techniques that enable the provision of efficient power converters while substantially avoiding or at least reducing one or more of the aforementioned problems.

[0006] This need can be met by the following subject matter. More specific solutions describe advantageous embodiments of the subject matter disclosed herein.

[0007] According to a first aspect of the subject matter disclosed herein, a controller is provided, particularly a converter bridge controller for power converter hardware (of a power converter) connectable to an AC power network. According to an embodiment of the first aspect, the controller includes: an output unit (e.g., a current controller) configured to generate a quadrature voltage component reference to a pulse width modulation (PWM) modulator determining the switching of the converter, wherein the quadrature voltage component reference includes a first signal and a second signal; the output unit includes a first component (e.g., a steady-state component) and a second component (e.g., a correction control unit); the first component is configured to generate the first signal based on a current reference of active current to be generated by the power converter hardware; and the second component is configured to provide a second signal to reduce the difference between the measured converter active current component of the feedback current and the current reference of the active current (e.g., matching the measured converter active current component of the feedback current with the current reference of the active current).

[0008] According to a second aspect of the subject matter disclosed herein, a power converter is provided. According to an embodiment of the second aspect, a power converter is provided, comprising: a converter bridge controller according to the first aspect or embodiments thereof; and power converter hardware controlled by an output signal of the converter bridge controller, wherein the output signal includes a quadrature voltage component reference. Therefore, the output signal of the converter bridge controller is a control signal for the power converter hardware.

[0009] According to a third aspect of the subject matter disclosed herein, a method for generating control signals for power converter hardware is provided. According to an embodiment of the third aspect, a method for generating control signals for power converter hardware connectable to an AC power network is provided, the method comprising: generating quadrature components of control signals depending on a first signal and a second signal; generating the first signal based on a current reference of an active current to be generated by the power converter hardware; and providing a second signal to reduce the difference between the measured feedback current's converter active current component and the active current's current reference (e.g., matching the measured feedback current's converter active current component with the active current's current reference).

[0010] According to a fourth aspect of the subject matter disclosed herein, a computer program product is provided. According to an embodiment of the fourth aspect, a computer program product is provided including non-transitory program elements configured to control the method according to the third aspect or embodiments thereof when executed by a processor device.

[0011] According to an embodiment, the quadrature voltage component reference is the d-axis reference voltage in the dq-axis coordinate system. Typically, as with field-oriented control, the dq-axis coordinate system has the advantage that control is performed by manipulating DC quantities rather than three-phase time-varying (AC) quantities. According to a further embodiment, the power converter hardware is operating with a pulse-width modulation (PWM) strategy, and the output signal of the converter bridge controller (and specifically the quadrature voltage component reference of the output signal) is a control signal for the PWM modulator of the power converter. In particular, according to an embodiment, the output signal is the PWM voltage reference of the PWM modulator that determines the switching of the power converter hardware.

[0012] The embodiments of the subject matter disclosed herein are based on the idea of ​​stabilizing an AC system (particularly in the sense that "inertia" is added to the AC system) by controlling the quadrature component in response to a current reference of the active current. Specifically, the embodiments of the subject matter disclosed herein are based on the idea of ​​stabilizing an AC system by adding a voltage to the d-axis instead of the q-axis by changing the coupling of the q-axis controller (e.g., a q-axis proportional-integral (PI) controller), and additionally or alternatively by adding a voltage to the q-axis instead of the d-axis by changing the coupling of the d-axis controller (e.g., a d-axis proportional-integral (PI) controller).

[0013] The embodiments of the subject matter disclosed herein permit operation on very weak power networks (AC systems) with a short-circuit ratio (SCR) << 1 and on islanded power networks.

[0014] According to an embodiment, the output unit is further configured to generate an in-phase or direct q-axis voltage component reference for the PWM modulator. The in-phase voltage component reference may be the primary component of the output signal (i.e., it primarily determines the voltage amplitude of the output signal supplied to the PWM modulator).

[0015] According to an embodiment, the in-phase voltage component reference includes a third signal and a fourth signal. The output unit may include a third component (e.g., a steady-state component) and a fourth component (e.g., a correction control unit). According to an embodiment, the third component is configured to generate a third signal based on a current reference for the reactive current (also referred to as Idp*); and the fourth component is configured to provide a fourth signal to reduce the difference between the measured feedback current converter reactive current component and the reactive current current reference (e.g., matching the measured feedback current converter reactive current component with the reactive current current reference).

[0016] According to an embodiment, a current reference for reactive current is provided by a voltage controller (Vac controller), for example, based on voltage demand and the measured voltage amplitude.

[0017] According to an embodiment, a further component of the output unit is configured to generate an in-phase voltage component reference based on voltage demand and voltage feedback signal.

[0018] According to an embodiment, the in-phase voltage component reference includes a further (e.g., a fifth) signal representing the desired baseband voltage at the converter output. For example, according to an embodiment, the fifth signal is one of the AC voltage demand (also referred to as Vac*), the nominal value of the AC voltage, and the filtered q-axis voltage feedback. The AC voltage demand is a voltage amplitude reference on the grid side of the converter reactor and is the voltage amplitude that the converter is attempting to achieve by providing both the in-phase and quadrature voltage component references to the PWM modulator.

[0019] According to an embodiment, the in-phase voltage component reference is generated by adding the individual signals (e.g., a third signal, a fourth signal, and an optional fifth signal).

[0020] According to an embodiment, the output unit includes a summing unit for adding a third signal and a fourth signal (and optionally a fifth signal) to generate an in-phase component of the output signal.

[0021] According to a further embodiment, instead of the aforementioned third and fourth signals, the in-phase voltage component includes an alternative fourth signal based on the AC voltage demand and the measured feedback voltage amplitude. According to the embodiment, the alternative fourth signal is provided to reduce the difference between the AC voltage demand and the measured feedback voltage amplitude. Therefore, in one embodiment, the third component of the output unit is omitted, and the fourth component is configured to provide the fourth signal to reduce the difference between the AC voltage demand and the measured feedback voltage amplitude.

[0022] According to the embodiment, the measured feedback voltage amplitude Vmag is the square root of the sum of the squares of the q-axis feedback voltage amplitude Vdp and the d-axis feedback voltage amplitude Vqp:

[0023] .

[0024] According to an embodiment, the q-axis feedback voltage amplitude can be a filtered signal (which may then be referred to as Vqpf), and / or the d-axis feedback voltage amplitude can be a filtered signal (which may then be referred to as Vdpf).

[0025] According to an embodiment, the quadrature voltage component reference includes a sixth signal representing the alignment of the dq-axis coordinate system, and the criterion for the dq-axis coordinate system and the measured voltage of the power network is zero. However, since the sixth signal is typically zero or close to zero, according to an embodiment, the sixth signal is omitted when calculating the quadrature voltage component reference.

[0026] According to an embodiment, an orthogonal voltage component reference is generated by adding a first signal, a second signal, and an optional sixth signal.

[0027] According to an embodiment, the output unit includes a summing unit for adding the first signal and the second signal (and optionally a sixth signal) to generate orthogonal components of the output signal.

[0028] According to an embodiment, the converter bridge controller further includes a tracking unit, particularly a phase-locked loop (PLL) controller; the tracking unit is further configured to align the dq-axis coordinate system with the input signal based on the measured voltage (Vfb).

[0029] The transformation from a three-phase AC system to the dq-axis coordinate system can be performed using the grid angle (theta0) calculated by the tracking unit (also referred to herein as a 3 / 2 conversion). The primary purpose of the tracking unit is to align the converter's internal dq-axis coordinate system (also referred to as the dq-axis reference frame) with the measured voltage in steady state. This is achieved, for example, by the action of the tracking unit's proportional-integral (PI) controller, by zeroing (or controlling) the d-axis component of the measured feedback voltage, as is known in the art.

[0030] According to one embodiment, the input signal to the tracking unit is based on a voltage feedback signal indicating the instantaneous d-axis voltage component of the measured network voltage. According to a further embodiment, the tracking unit is configured to provide a frequency signal indicating the grid frequency (f0) and an angle signal indicating the grid angle (theta0), the frequency signal and the angle signal (f0, theta0) being calculated based on the input signal to the tracking unit.

[0031] According to an embodiment, the second and / or fourth components of the output unit include at least one of a proportional-integral controller and a proportional-integral-derivative controller. However, according to other embodiments, any other suitable controller may be used.

[0032] According to an embodiment, the input signal to the tracking unit is further based on the frequency signal of the tracking unit. For example, according to an embodiment, the tracking unit includes a summing unit (also referred to as a first summing unit) configured to sum (i) the voltage feedback signal and (ii) an offset component based on the frequency signal, thereby providing the input signal. For example, according to an embodiment, a gain stage (which may be referred to as VdDroop) is provided, which receives the frequency signal and provides the offset component in response thereto. The offset component can assist the tracking unit in finding a stable frequency operating point—if the power network is an islanded power network—and can allow for frequency-dependent voltage tracking errors.

[0033] According to a further embodiment, the active current reference (Iqp*) includes an offset component based on the frequency signal of the tracking unit. This offset component of the active current reference assists in balancing the active load in an islanded power network with the active current controlled by the converter bridge controller. According to an embodiment, the offset of the active current reference is generated by manipulating the nominal current reference of the active current based on power demand and the measured feedback voltage amplitude. According to a further embodiment, the offset component of the active current reference is generated by manipulating power demand. In the case of a wind turbine converter, power demand is typically based on prevailing wind conditions (only one example is given).

[0034] According to an embodiment, the converter bridge controller includes a summing unit (also referred to as a second summing unit) configured to receive a nominal current reference of active current based on power demand and a measured feedback voltage amplitude; wherein the (second) summing unit is further configured to receive a current offset signal based on a frequency signal from a tracking unit; and wherein the (second) summing unit is configured to provide a current reference (Iqp*) of the active current based on the nominal current reference and the current offset signal. In this embodiment, the current offset signal corresponds to an offset component of the current reference of the active current.

[0035] According to a further embodiment, the converter bridge controller includes a summing unit (also referred to as a second or third summing unit) configured to receive power demand; wherein the (second / third) summing unit is further configured to receive a power offset signal based on a frequency signal from a tracking unit; and wherein the (second / third) summing unit is configured to provide a modified power demand based on the power demand and the power offset signal to a current reference calculation unit for calculating a current reference (Iqp*) of the active current based on the modified power demand and the measured feedback voltage amplitude.

[0036] Current offset signals and current references based on active current with modified power demand can provide a frequency-dependent steady-state active current (power) dependence; such a relationship is often referred to as regulator control in power engineering. These combined elements allow converters to have a frequency-to-power relationship such that converter groups or other generators with said control can share a balance of active power demand in an isolated (islanded) network. In such a network, it may be necessary for generators to be able to meet fluctuating active power demand in a manner that satisfies the difference between the shared dispatched power (the sum of active power references) and actual demand for a given number of participating generators.

[0037] The participating bridge controllers “see” the same frequency, which allows them to change their output power equally in response to frequency changes.

[0038] According to an embodiment, the first component of the output unit is configured to further depend on the frequency signal of the tracking unit (e.g., or The first signal (Vqxc) is provided by either an active current reference, the frequency signal of the tracking unit's angle signal, or the inductance of the line reactor plus the turbine transformer. According to an embodiment, the first signal is calculated as the product of these quantities.

[0039] According to a further embodiment, the third component of the output unit is configured to further depend on the frequency signal of the tracking unit (e.g., or The third signal (Vdxc) is provided using either a current reference for the reactive current, the frequency signal or angle signal of the tracking unit, and the inductance of the line reactor plus the turbine transformer. According to an embodiment, the third signal is calculated as the product of these quantities.

[0040] According to embodiments, any of the signals described herein can be passed through a suitable filter, which in embodiments may include at least one of an adaptive (i.e., frequency-dependent) filter and a non-adaptive filter. Providing a suitable filter is a well-known practice known to those skilled in the art.

[0041] According to a further embodiment, the voltage feedback signal (Vdpf) is a filtered d-axis component calculated based on the measured three-phase network voltage and theta0 of the power network.

[0042] As used herein, references to computer program products are intended to be equivalent to references to non-transitory program elements and / or computer-readable media containing non-transitory program elements for controlling processor devices (e.g., computer systems) to implement and / or coordinate the performance of the methods and embodiments thereof described herein.

[0043] Non-transitory program elements can be implemented as computer-readable instruction code using any suitable programming language (such as, for example, JAVA, C++) and can be stored on computer-readable media (removable disks, volatile or non-volatile memory, embedded memory / processors, etc.). Non-transitory program elements are operable to program a computer or any other programmable device to perform intended functions. Computer program products are available from networks such as the World Wide Web, from which they can be downloaded.

[0044] The subject matter disclosed herein can be implemented using computer programs (corresponding software). However, the subject matter disclosed herein can also be implemented using one or more specific electronic circuits (corresponding hardware). Furthermore, the subject matter disclosed herein can also be implemented in a hybrid form—that is, a combination of software modules and hardware modules.

[0045] According to an embodiment of the first aspect, the converter bridge controller is adapted to provide one or more functionalities and / or features as disclosed herein, and / or provide one or more claimed functionalities and / or features as disclosed herein, particularly in any aspect of the embodiments disclosed herein.

[0046] According to an embodiment of the second aspect, the power converter is adapted to provide one or more of the functionalities and / or features of the embodiments disclosed herein, and / or to provide one or more of the claimed functionalities and / or features of the embodiments disclosed herein, particularly any aspect thereof.

[0047] According to an embodiment of the third aspect, the method is adapted to provide one or more functionalities and / or features in the embodiments disclosed herein, and / or provide one or more claimed functionalities and / or features in the embodiments disclosed herein, particularly in any aspect of the embodiments disclosed herein.

[0048] According to an embodiment of the fourth aspect, the computer program product is adapted to provide one or more functionalities and / or features as disclosed herein, and / or to provide one or more claimed functionalities and / or features as disclosed herein, particularly in any aspect of the embodiments disclosed herein.

[0049] The reference converter bridge controller, power converter, and corresponding methods and computer program products have been described above and exemplary embodiments of the subject matter disclosed herein will be described below. It must be noted that any combination of features related to different aspects of the subject matter disclosed herein is of course possible. In particular, some features have been or will be described with reference to device-type embodiments, while others have been or will be described with reference to method-type embodiments. However, those skilled in the art will understand from the above and following description that, unless otherwise stated, any combination of features related to different aspects or embodiments, such as even combinations of features from device-type embodiments and features from method-type embodiments, are considered to be disclosed with this application, in addition to any combination of features belonging to one aspect.

[0050] The aspects and embodiments defined above, as well as further aspects and embodiments of the subject matter disclosed herein, will be apparent from the examples to be described below and explained with reference to the accompanying drawings, but the invention is not limited thereto. Attached Figure Description

[0051] Figure 1 A control block diagram of a converter bridge controller according to an embodiment of the subject matter disclosed herein is shown schematically;

[0052] Figure 2 A further control block diagram of a converter bridge controller according to an embodiment of the subject matter disclosed herein is shown;

[0053] Figure 3 A further control block diagram of a converter bridge controller according to an embodiment of the subject matter disclosed herein is shown;

[0054] Figure 4 A further control block diagram of a converter bridge controller according to an embodiment of the subject matter disclosed herein is shown;

[0055] Figure 5 A power converter according to an embodiment of the subject matter disclosed herein is shown. Detailed Implementation

[0056] The illustrations in the accompanying drawings are schematic. Note that similar or identical elements are provided with the same reference numerals in different drawings.

[0057] Figure 1 A control block diagram of a converter bridge controller 100 according to an embodiment of the subject matter disclosed herein is shown schematically.

[0058] According to an embodiment, the controller 100 includes, as shown in the example... Figure 1 The output unit 102 shown is in the form of a current controller and is configured to generate a quadrature voltage component reference 104 for the PWM modulator 106. The PWM modulator 106 may be part of the controller 100 (e.g., ...). Figure 1 (as shown in the illustration), or in another embodiment, it can be a separate device.

[0059] According to an embodiment, the quadrature voltage component reference 104 includes a first signal 108 and a second signal 110 (i.e., it is composed of the first signal 108 and the second signal 110, such as...). Figure 1 (As shown in the diagram). According to an embodiment, a summing unit 111 is provided for adding the first signal 108 and the negative of the second signal 110 (signal 104 = -signal 110 - signal 108). The first signal 108 and the second signal 110 are generated by the first component 112 and the second component 114 of the output unit, respectively. According to an embodiment, the first component 112 provides the steady-state component and is based on what should be provided by the power converter hardware ( Figure 1The active current generated (not shown) is used as a current reference 116Iqp* to provide the first signal 108. For example, according to an embodiment, the first signal 108 (also referred to as Vdxc) is calculated as:

[0060] Vdxc-2*π*f0*L*Iqp*

[0061] Where π is the digital value pi, f0 is the grid frequency, L is the inductance of the line reactor + turbine transformer, and Iqp* is the reference current 116 for the active current.

[0062] According to an embodiment, the second component 114 is configured to provide a second signal 110 to reduce (e.g., to eliminate) the difference between the measured feedback current converter active current component 118 and the active current current reference 116. In another embodiment, the second component 114 is configured to correct errors in the feedforward term of the active current reference.

[0063] According to an embodiment, in the summing node 120 of the second component 114, the active current component 118 of the converter is subtracted from the current reference 116 of the active current. The resulting signal 122 is provided to a suitable controller, such as a proportional-integral controller 124. According to an embodiment, the gain G(Kpp+Kip) of the proportional-integral controller 124 is calculated according to the following formula:

[0064] ,

[0065] Among them, for example

[0066] ;

[0067] ;

[0068] It is the time integral over Kip; and

[0069] L is the inductance of the line reactor + turbine transformer, and BW is the expected bandwidth of the current controller.

[0070] According to embodiments, typical bandwidths are in the range of 20 rad / s to 40 rad / s. For example, according to an embodiment, the bandwidth is BW = 30 rad / s. Therefore, embodiments of the subject matter disclosed herein allow for lower bandwidths than conventional systems (typically with a bandwidth of 600 rad / s).

[0071] According to a further embodiment, the output unit 102 is further configured to generate an in-phase voltage component 126 to the PWM modulator 106. According to an embodiment, the in-phase voltage component 126 includes a third signal 128 and a fourth signal 130. According to an embodiment, a summing unit 131 is provided for adding the third signal 128 and the fourth signal 130. The third signal 128 and the fourth signal 130 are generated by a third component 132 and a fourth component 134 of the output unit 102, respectively.

[0072] According to an embodiment, the third component 132 is configured similarly to the first component 112. For example, according to an embodiment, the third component 132 provides a steady-state component and provides a third signal 128 based on a reactive current reference 136 (i.e., a current reference, Idp*, of the reactive current that should be generated by the power converter hardware).

[0073] For example, according to an embodiment, the third signal 128 (also known as Vqxc) is calculated as:

[0074]

[0075] Where π is the digital value pi, f0 is the grid frequency, L is the inductance of the line reactor + turbine transformer, and Idp* is the reactive current reference 136.

[0076] According to an embodiment, the fourth component 134 is configured to provide a fourth signal 130 to reduce (e.g., eliminate) the difference between the measured feedback current converter reactive current component 138 and the reactive current current reference 136. According to an embodiment, the fourth component 134 is configured similarly to the second component 114. For example, according to an embodiment, the fourth component 134 is configured to correct errors in the feedforward term of the reactive current reference.

[0077] According to an embodiment, in the summing node 140 of the fourth component 134, the reactive current component 138 of the converter is subtracted from the current reference 136 of the reactive current to provide the resulting signal 142. Typically, the feedback signal is subtracted from the reference (i.e., in summing unit 140, signal 142 = signal 136 - signal 138; in summing unit 120, signal 122 = signal 116 - signal 118).

[0078] The resulting signal 142 is provided to a suitable controller, such as a proportional-integral controller 144. According to an embodiment, the proportional-integral controller 144 is a positive-sequence current controller, which can be configured identically to the controller 124 of the second component 114. Therefore, according to an embodiment, the gain G(Kpp+Kip) of the proportional-integral controller 144 of the fourth component 142 is calculated according to the following formula:

[0079] ;

[0080] in

[0081] ;

[0082] ;

[0083] L, BW, and integrals As defined above for controller 124.

[0084] According to the embodiment, the quadrature component 104 of the output signal is the d-axis reference voltage Vd of the synchronously rotating dq-axis coordinate system, and the in-phase component 126 of the output signal is the q-axis reference voltage Vq of the synchronously rotating dq-axis coordinate system.

[0085] According to one embodiment, the converter bridge controller 100 includes a tracking unit 146 configured to align the dq-axis coordinate system with an input signal 148 based on a measured voltage 150 Vfb of the power network. According to another embodiment, the input signal 148 indicates the inverse d-axis component of the measured network voltage 150.

[0086] The measured network voltage is time-varying, so in the above context, instantaneous means that the signal represents the network voltage amplitude at that particular moment. If, according to the embodiment, the power converter is microprocessor-controlled, all calculations of control quantities will be performed in precise time steps, such as 200 microseconds (200 μs). In such an exemplary implementation, the “instantaneous” representation of the continuously time-varying AC system is updated every 200 μs.

[0087] According to an embodiment, the tracking unit 146 is further configured to provide a frequency signal 147 indicating the grid frequency f0. According to a further embodiment, the tracking unit is further configured to provide an angle signal 149 indicating the grid angle theta0. According to an embodiment, the frequency signal 147 / angle signal 149 is determined by the tracking unit 146 based on the input signal 148. According to a further embodiment, the tracking unit 146 is a phase-locked loop controller (PLL controller).

[0088] According to one embodiment, the tracking unit 146 includes a suitable controller 209, such as a proportional-integral controller, which provides a frequency signal 147 in response to the input signal 148. According to a further embodiment, the tracking unit 146 includes an integrator 211 that integrates the frequency signal 147 to provide an angle signal 149.

[0089] According to an embodiment, the voltage feedback signal 152 is one of two outputs of a three-phase AC to dq converter (e.g., a filtered output). For example, according to an embodiment, the controller 100 includes a three-phase AC to dq converter 154 that receives a measured voltage 150 and angle theta 0 149 as inputs and provides a d-axis voltage component 156 Vdp and a q-axis voltage component 158 ​​Vqp in response. According to an embodiment, a filter, such as a first filter 160, is provided, configured to filter the d-axis voltage component 156, thereby generating a filtered d-axis voltage component 161, also referred to as Vdpf. According to an embodiment, the filtered d-axis voltage component 161 is taken as the voltage feedback signal 152, such as... Figure 1 As shown in the figure. Further, according to an embodiment, a second filter 162 is provided, configured to filter the q-axis voltage component 158 ​​to provide a filtered q-axis component 164, also referred to as Vqpf. According to a further embodiment, an amplitude calculation unit 166 is provided, configured to calculate a voltage amplitude 168 (also referred to as the measured feedback voltage amplitude Vmag) based on the filtered d-axis voltage component 161 and the filtered q-axis voltage component 164.

[0090] .

[0091] According to an embodiment, the alignment of the converter's internal dq-axis reference frame with the measured voltage 150 is performed by controlling the d-axis voltage component 156 to zero via the operation of the tracking unit 146. However, this alignment is a standard technique and therefore is not described in more detail.

[0092] According to an embodiment, the active current component 118 of the measured feedback current converter is the output of a three-phase AC-to-dq converter (e.g., a filtered output). For example, according to an embodiment, the controller 100 includes a three-phase AC-to-dq converter 170 that receives the measured current 172 Ifb and provides a d-axis current component 174 Idfb and a q-axis current component 176 Iqfb. As is typically the case, the dq converter 170 may also receive the angle theta0. According to an embodiment, a filter, such as a third filter 178, is provided, configured to receive the d-axis current component 174 and, in response, provide a filtered d-axis current component 180 Idfbf. According to an embodiment, the filtered d-axis current component 180 is taken as the measured feedback converter reactive current component 138. According to a further embodiment, a fourth filter 182 is provided, configured to receive the q-axis current component 176 and, in response, provide a filtered q-axis current component 184 Iqfbf. According to the embodiment, the filtered q-axis current component 184 is taken as the active current component 118 of the converter of the measured feedback current, such as... Figure 1 As shown in the image.

[0093] The conversion from a three-phase AC system to the dq-axis coordinate system (shown as a 3 / 2 conversion performed by dq converters 154 and 170) can be performed using the grid angle 149 (theta0) calculated by the tracking unit 146, such as... Figure 1 As shown in the image.

[0094] According to a further embodiment, the in-phase voltage component 126 includes a fifth signal 186 (which may also be referred to as Vac* or Vac nominal), representing the desired baseband voltage at the converter's output. Therefore, in this embodiment, the summing unit 131 is configured to also receive the fifth signal 186 and add the third signal 128, the fourth signal 130, and the fifth signal 186.

[0095] According to an embodiment, the PWM modulator is configured to receive an in-phase voltage component 126 and a quadrature voltage component 104, as well as theta0, and in response to provide an output signal 188, such as in response to a switching command for an insulated-gate bipolar transistor (IGBT). According to an embodiment, PWM modulation requires theta0, Vd, and Vq.

[0096] It should be noted that while the second and fourth components include a proportional-integral controller according to some of the embodiments described above, any suitable controller may be used for this purpose according to other embodiments. For example, according to an embodiment, the second and / or fourth components may include a proportional-integral-derivative controller.

[0097] Furthermore, any filters described with respect to controller 100 according to the embodiments (i.e., optionally), such as filters (filter blocks) 160, 162, 178, 182, and the first component 112 and the third component 132, may include adaptive (frequency-dependent) components. According to the embodiments, entities 112, 132, 160, 162, 178, 182 may include combinations of adaptive and non-adaptive components, and in particular, filter blocks 160, 162, 178, 182 may include both adaptive and non-adaptive filters. For this purpose, the frequency signal 147 of tracking unit 146 can be provided to any such adaptive component, such as... Figure 1 The dashed line at position 147 indicates this. For example, filters 160, 162, 178, and 182 may include an asymmetric notch filter (e.g., at 2 * f0 = 100 Hz) and a stabilized notch filter (exemplarily shown in...). Figure 4 middle).

[0098] Figure 2 A further converter bridge controller 200 according to an embodiment of the subject matter disclosed herein is shown.

[0099] Figure 2 The controller 200 shown includes a controller with Figure 1 The controller 100 shown contains similar or identical components, and the description of these components will not be repeated here. Instead, additional or different components of the controller 200 will be described below with reference to further embodiments.

[0100] According to an embodiment, the active current reference 116 includes a current offset component 190 (also referred to as Iqdroop) based on the frequency signal 147 of the tracking unit 146. For example, according to an embodiment, an offset device 192 is provided that receives the frequency signal 147 and provides the current offset component 190 in response thereto. According to an embodiment, the offset device 192 includes a gain stage having a typical gain of approximately 3% of the active current Iq per radian per second (Iqdroop = 3% Iq / rad / s).

[0101] Here, Iq means the rated active current of the power converter.

[0102] According to a further embodiment, a summing unit 194 is provided, configured to receive a nominal current reference 196 based on the power demand 198 and the measured feedback voltage amplitude 168. According to an embodiment, a current reference calculation unit 202 is provided, configured to receive the power demand 198 and the measured feedback voltage amplitude 168, and in response provide the nominal current reference 196 for the active current.

[0103] According to an embodiment, the current reference calculation unit 202 calculates the active current demand based on the wind turbine power demand. The wind turbine power demand is calculated by the wind turbine controller to (typically) maximize the power extracted from available wind conditions.

[0104] The summing unit 194 is further configured to subtract the current offset component 190 from the nominal current reference 196 of the active current in order to provide a current reference 116 for the active current. Subtracting the current offset component 190 from the nominal current reference 196 of the active current can help the current controller 102 find a stable operating point, especially if the converter is operating in islanded mode (not connected to the grid).

[0105] According to a further embodiment, the input signal 148 is based not only on the voltage feedback signal 152 but also on the frequency signal 147 of the tracking unit. For example, according to an embodiment, a voltage offset component 204 (which may also be referred to as Vddroop) is added to the voltage feedback signal 152. Adding the voltage offset component 204 to the voltage feedback signal 152 can help the tracking unit find a stable frequency operating point, especially if the converter is operating in islanded mode (not connected to the power grid).

[0106] According to one embodiment, the converter bridge controller 200 includes a summing unit 206 for adding the voltage feedback signal 152 and the voltage offset component 204 to provide an input signal 148. According to a further embodiment, a zero-voltage signal 207 can be added to the output signal 148, for example, by correspondingly configuring the summing unit 206, such as... Figure 2 As shown in the image.

[0107] According to an embodiment, the voltage offset component 204 is provided by a voltage offset calculation unit 208 (e.g., a gain stage). A typical gain for the offset calculation unit 208 may be -1 volt per second per radian (Vddroop = -1 V / rad / s).

[0108] According to a further embodiment, the reactive current reference 136 is provided by the voltage controller 210 (Vac controller), such as Figure 2 As shown in the illustration. According to an embodiment, voltage controller 210 receives voltage demand 212 and the measured feedback voltage amplitude 168 as input 214 to controller 216 (e.g., a proportional-integral controller). According to an embodiment, a summing unit 218 is provided for subtracting the measured feedback voltage amplitude 168 from the voltage demand 212, such as... Figure 2 As shown in the illustration. According to an embodiment, the voltage controller 210 provides a current reference 136 (also known as Idp*) for reactive current in response to voltage demand 212 and the measured feedback voltage amplitude 168.

[0109] Figure 3 A further converter bridge controller 300 according to an embodiment of the subject matter disclosed herein is shown.

[0110] Figure 3 The controller 300 shown includes a controller with Figure 1 The controller 100 shown and Figure 2 The controller 200 shown contains similar or identical components, and the description of these components will not be repeated here. Instead, additional or different components of the controller 300 will be described below with reference to further embodiments.

[0111] Instead of such as about Figure 2 The description is of subtracting the current offset component 190 from the nominal current reference 196 of the active current, such as... Figure 3 As shown, the power offset component 220 can be subtracted from the power demand 198. According to an embodiment, the power offset component 220 is provided based on the frequency signal 147 of the tracking unit 146. For example, according to an embodiment, a power offset device 226 is provided that receives the frequency signal 147 and provides the power offset component 220 in response thereto.

[0112] According to an embodiment, the controller 300 includes a summing unit 222 for subtracting a power offset component 220 from the power demand 198 to provide a modified power demand 224, such as... Figure 3 As shown in the diagram. The modified power demand 224 is then provided to the current reference calculation unit 202, which provides a current reference 116 for the active current based on the modified power demand 224 and the measured feedback voltage amplitude 168.

[0113] Subtracting the power offset component 220 from the power demand 198 can enable the current controller 102 to find a stable operating point, especially if the converter is operating in islanded mode (not connected to the grid).

[0114] Considering the above Figure 2 and Figure 3 Subtracting the current offset component 190 from the nominal current reference 196 of the active current, or subtracting the power offset component 220 from the power demand 198, allows the converter to have a frequency-to-power relationship that enables a group of converters or other generators with the described control to share a balance of active power demand in an isolated (islanded) network. In such a network, it is necessary for the generator to be able to meet fluctuating active power demand in a manner that satisfies the difference between the power dispatched (the sum of active power references) shared by a given number of participating generators (e.g., via the frequency of the islanded network) and the actual demand.

[0115] Figure 4A further converter bridge controller 400 is shown, according to an embodiment of the subject matter disclosed herein.

[0116] Figure 4 The controller 400 shown includes a controller with Figure 1 The controller 100 shown Figure 2 The controller 200 shown and Figure 3 The controller 300 shown contains similar or identical components, and the description of these components will not be repeated here. Instead, additional or different components of the controller 400 are described below with reference to further embodiments.

[0117] According to an embodiment, (e.g., by a further component 134 of the controller) an in-phase voltage component reference 126 is generated based on voltage demand 212 and feedback voltage 150, or more specifically based on voltage demand 212 and voltage amplitude 168, such as... Figure 4 As shown in the image.

[0118] According to an embodiment, voltage amplitude 168 is filtered by filter 228 (fifth filter) and then passed through percentage calculation unit 230, which provides a percentage of the measured voltage 232 (relative to the nominal voltage). The difference 234 (in percentage) between the percentage of the measured voltage 232 and the voltage reference 212 is determined as input 214 to controller 144. Controller 144 generates in-phase voltage component reference 126 in response to input 214.

[0119] According to an embodiment, a summing unit 236 is provided for receiving a voltage amplitude 168 or a signal derived therefrom (e.g., a percentage of the measured voltage 232) and a voltage demand 212, and providing a difference 234 in response thereto.

[0120] According to further embodiments, a PI controller (e.g., controller 144) disclosed herein includes a KP gain block 238 and a KI gain block 240, an integration block 242 for integrating the output of the KI block, and a summing unit 244 for adding the output of the KP gain block and the integrated output of the KI gain block to an output (e.g., the in-phase voltage component reference 126 in the illustrated embodiment). It should be understood that, for example, the PI controller of PI controller 124 or tracking unit 146 can be configured accordingly, and... Figure 4 The corresponding block has been provided with the same reference marker.

[0121] Regarding tracking unit 146, note that summing unit 244 also receives nominal frequency 246.

[0122] Unlike controllers 100, 200, and 300, Figure 4The controller 400 explicitly shows a dq-to-three-phase AC converter block 248, which receives a quadrature voltage component reference 104 and a non-inverting voltage component reference 126, and in response provides a PWM input signal to a PWM modulator 250. The PWM modulator provides switching commands to a converter reactor 254, the output of which is provided to the power grid 260 via components 256 and 258.

[0123] According to the embodiment, in addition to the first signal 108 and the second signal 110, the quadrature voltage component reference also includes a quadrature voltage feedforward component 262, such as... Figure 4 As shown in the figure. However, in most cases, the quadrature voltage feedforward component 262 (also known as VdFfwd) will be zero or close to zero, and therefore can be omitted according to the embodiment.

[0124] Therefore, according to the embodiment, the reference voltages Vd 104 (quadrature voltage component reference) and Vq (in-phase voltage component reference) 126 of the PWM modulator are calculated as follows.

[0125] According to an embodiment (similar to) Figure 1 , Figure 2 and Figure 3 As shown, for example in the summing unit 244 of controller 144, further signals (Vac* or Vac nominal 186, see also) can be added. Figure 1 , Figure 2 or Figure 3 Add to Vq).

[0126] Vq (126) = Output of VacPIop (144) = (in the above embodiment) = Output of KP gain block 238 + Output of integration block 242 + (Vac* or Vac nominal, 186).

[0127] .

[0128] Figure 5 A power converter 280 according to an embodiment of the subject matter disclosed herein is shown.

[0129] The power converter includes a converter bridge controller according to embodiments of the subject matter disclosed herein, such as those relating to... Figure 1The converter bridge controller 100 is described. According to an embodiment, the power converter includes a processor device 264 on which the converter bridge controller 100 (or 200, 300, 400) is implemented. According to an embodiment, the converter bridge controller is implemented in software (e.g., in the form of a computer program product according to embodiments of the subject matter disclosed herein). According to an embodiment, the processor device 264 includes at least one processor configured to execute program elements according to embodiments of the subject matter disclosed herein.

[0130] According to an embodiment, the program element is configured to provide, when executed by the processor device 264, the converter bridge controller 100 (or, in other embodiments, converter bridge controller 200, 300, or 400) described in the embodiments of the subject matter disclosed herein. Through the operation of the bridge controller according to the embodiments of the subject matter disclosed herein, an output signal 188 of the PWM modulator 106 is provided. According to an embodiment, the PWM modulator (e.g., as part of the converter bridge controller) is also implemented in software. According to an embodiment, the output signal 188 of the PWM modulator is provided based on a quadrature voltage component reference Vd, a non-inverting voltage component reference Vq, and an angle signal theta0, such as... Figure 5 As shown in the image.

[0131] Further, according to an embodiment, the power converter 280 includes power converter hardware 268 configured to receive an output signal 188 from a PWM modulator and, in response, convert power from a power generation device such as a wind turbine generator into output power, which is supplied to the power network 260, such as a power grid, via an electrical connection 270 between the power converter 280 and the power network 260. It should be understood that the power network 260 can also be an islanded power network. In such a case, regarding... Figure 2 and Figure 3 The described droop signals 190, 204, and 220 function to improve the stability of the converter bridge controller operation.

[0132] According to an embodiment, the power converter hardware 268 includes power electronic components (such as IGBTs) and may include other hardware, such as power supply and gate drivers for the power electronic components. Figure 5 (Not shown in the image).

[0133] According to embodiments of the subject matter disclosed herein, any suitable entity disclosed herein (e.g., controller, unit, and device) is provided at least in part as a corresponding computer program that enables a processor device to provide the functionality of the corresponding entity as disclosed herein. According to other embodiments, any suitable entity disclosed herein may be provided in hardware. According to other hybrid embodiments, some entities may be provided in software, while others may be provided in hardware.

[0134] It should be noted that any entity disclosed herein (e.g., controllers, units, and devices) is not limited to the dedicated entities described in some embodiments. Rather, the subject matter disclosed herein can be implemented in various ways and at various granularities at the device level or software module level, while still providing the desired functionality. Furthermore, it should be noted that, according to embodiments, each of the functions disclosed herein can be provided as a separate entity (e.g., a software module, a hardware module, or a hybrid module). According to other embodiments, entities (e.g., software modules, hardware modules, or hybrid modules (combined software / hardware modules)) are configured to provide two or more functions as disclosed herein. According to an embodiment, the converter bridge controller includes a processor device comprising at least one processor for executing at least one computer program corresponding to a respective software module.

[0135] In this paper, the summation unit can generally be a summation node.

[0136] It should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, elements described in association with different embodiments may be combined. It should also be noted that reference numerals in the claims should not be construed as limiting the scope of the claims.

[0137] To summarize the above embodiments of the present invention, it can be stated that:

[0138] A converter bridge controller 200 is provided for power converter hardware 268 connectable to an AC power network 260. The controller 200 includes an output unit 102 configured to generate a direct 104 and a quadrature voltage component reference 126 for a PWM modulator 106 that determines the switching of the power converter hardware 268, wherein the quadrature voltage component reference 126 includes a first signal 108 and a second signal 110. The output unit 102 includes a first component 112 and a second component. The first component 112 is configured to generate the first signal 108 based on a current reference 116 of the active current to be generated by the power converter hardware 268. The second component is configured to provide a second signal 110 to reduce the difference between the measured converter active current component 118 of the feedback current and the current reference 116 of the active current.

[0139] According to an embodiment, the current controller is a positive-sequence current controller, wherein the d-axis and q-axis outputs of the feedforward correction units (the first component 114 and the third component 134 of the current controller 102) are routed to opposite axes Vq and Vd, respectively.

Claims

1. A converter bridge controller (100, 200, 300, 400) for power converter hardware (268) connectable to an AC power network (260), comprising: The output unit (102) is configured to generate an orthogonal voltage component reference Vd (104) for a PWM modulator (106) that determines the switching of the power converter hardware (268), wherein the orthogonal voltage component reference Vd (104) includes a first signal (108) and a second signal (110), and wherein the orthogonal voltage component reference Vd (104) is a d-axis reference voltage of a synchronously rotating dq-axis coordinate system; The output unit (102) includes a first component (112) and a second component; The first component (112) is configured to generate a first signal (108) based on a current reference Iqp* (116) of the active current to be generated by the power converter hardware (268); and The second component is configured to provide a second signal (110) to reduce the difference between the active current component Iqfbf (118) of the measured feedback current converter and the current reference Iqp* (116) of the active current.

2. The converter bridge controller according to claim 1, in, The output unit (102) is further configured to generate an in-phase voltage component reference (126) for the PWM modulator, wherein the in-phase voltage component reference Vq (126) is a q-axis reference voltage in a synchronously rotating dq-axis coordinate system; wherein (i) The in-phase voltage component reference Vq (126) includes a third signal (128) and a fourth signal (130), and the output unit (102) includes a third component (132) and a fourth component (134). The third component (132) is configured to generate the third signal (128) based on the current reference (136) of the reactive current, and the fourth component (134) is configured to provide the fourth signal (130) to reduce the difference between the measured feedback current converter reactive current component (138) and the reactive current current reference (136). or (ii) A further component (134) of the output unit (102) is configured to generate an in-phase voltage component reference Vq (126) based on the voltage demand (212) and the voltage feedback signal (168).

3. The converter bridge controller according to claim 2, wherein, The in-phase voltage component reference Vq (126) includes a fifth signal (186) that represents the desired steady-state fundamental frequency voltage at the output of the power converter hardware (268).

4. The converter bridge controller according to claim 1, It further includes a tracking unit (146); The tracking unit (146) is further configured to align the dq axis coordinate system with the input signal (148) based on the measured network voltage (150).

5. The converter bridge controller according to claim 4, wherein, The tracking unit (146) is a phase-locked loop controller.

6. The converter bridge controller according to claim 4, The input signal (148) is based on a voltage feedback signal (152), which indicates the instantaneous d-axis voltage component of the measured network voltage (150); and / or The tracking unit (146) is configured to provide a frequency signal (147) indicating the grid frequency and an angle signal (149) indicating the grid angle, the frequency signal (147) and the angle signal (149) being calculated based on the input signal (148).

7. The converter bridge controller according to claim 6, wherein, The input signal (148) is further based on the frequency signal (147) of the tracking unit (146).

8. The converter bridge controller according to claim 7, wherein, The tracking unit (146) includes a first summing unit (206) configured to sum (i) the voltage feedback signal (152) and (ii) the offset component (204) based on the frequency signal (147), thereby providing an input signal (148).

9. The converter bridge according to any one of claims 6 to 8, wherein, The active current reference Iqp*(116) includes the offset component of the frequency signal (147) based on the tracking unit (146).

10. The converter bridge controller of claim 6, further comprising: Second summation unit (194); The second summing unit (194) is configured to receive a nominal current reference (196) of the active current based on the power demand (198) and the measured feedback voltage amplitude (168). The second summing unit (194) is further configured to receive a current offset signal (190) based on the frequency signal (147) of the tracking unit (146); The second summing unit (194) is configured to provide a current reference Iqp* (116) for the active current based on the nominal current reference (196) and the current offset signal (190) of the active current.

11. The converter bridge controller of claim 6, further comprising: Second summation unit (222); The second summing unit (222) is configured to receive power requirements (198); The second summing unit (222) is further configured to receive a power offset signal (220) based on the frequency signal (147) of the tracking unit (146); The second summing unit (222) is configured to provide a modified power demand (224) to the current reference calculation unit (202) based on the power demand (198) and the power offset signal (220) for calculating the current reference Iqp* (116) of the active current based on the modified power demand (224) and the measured feedback voltage amplitude (168).

12. The converter bridge controller according to claim 6, wherein the first component (112) of the output unit (102) is configured to provide a first signal (108) further depending on the frequency signal (147) or angle signal (149) of the tracking unit (146).

13. The converter bridge controller according to claim 7, The voltage feedback signal (152) is the filtered d-axis component of the measured network voltage (150).

14. A power converter (280), comprising: The converter bridge controller (100, 200, 300, 400) according to any one of claims 1 to 13; and Power converter hardware (268) controlled by the output signal (188) of the converter bridge controller.

15. A method for generating control signals (104, 126) for power converter hardware (268) connectable to an AC power network, the method comprising: The voltage quadrature component Vd(104) of the control signal (104, 126) is generated depending on the first signal (108) and the second signal (110); The first signal (108) is generated based on the current reference Iqp* (116) of the active current to be generated by the power converter hardware (268); and A second signal (110) is provided to reduce the difference between the active current component Iqfbf (118) of the measured feedback current converter and the current reference Iqp* (116) of the active current.

16. A computer program product comprising non-transitory program elements configured to control the method of claim 15 when executed by a processor device (264).

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