Control device for controlling a voltage source converter, power support system and method

Abstract

According to an aspect of the present disclosure, there is provided a control device (100) for a voltage source converter, VSC, electrically connected to a power system via a point of common coupling, PCC, wherein the control device (100) is configured to provide a voltage reference (U ref ) to the VSC to control the VSC in a static synchronous compensator, STATCOM, mode, or in an enhanced STATCOM, ESTATCOM, mode, wherein the voltage reference (U ref ) is based on at least a phase angle of an internal voltage source, IVS, of the VSC, wherein the IVS phase angle ( ) is indicative of at least an amount of active power (P) exchanged between the VSC and the power system via the PCC, the control device (100) comprising: a power control loop (110) configured to determine the IVS phase angle ( ) based on at least a feed-forward damping of an energy parameter.

Description

Technical Field

[0001] This disclosure relates to the fields of power systems and electrical engineering. Specifically, this disclosure relates to the synchronization and control of grid-connected converters and voltage source converters (VSCs) in power systems. Background Technology

[0002] The global transition to a renewable energy-based power system is driving the replacement of traditional synchronous power generation with converter-interface power generation. Grid-connected (GFM) converters have become the preferred solution for addressing the challenges of this transition. These converters typically utilize their DC-side energy for grid synchronization, thus enabling them to function as voltage sources.

[0003] Over time, the GFM strategy has evolved from simply providing basic reactive power support to actively shaping grid voltage and responding to changes in grid voltage phase angle and frequency. Additionally, the VSC must remain operational and support the grid under extremely low short-circuit power conditions, such as during grid recovery. This requirement necessitates the integration of additional energy storage systems (ESS), such as supercapacitors and battery energy storage systems (BESS), to supplement the limited energy available in the DC branch capacitors for grid stabilization. In this context, the VSC's synchronization control must be resilient and capable of providing critical damping services to ensure reliable operation.

[0004] Various synchronization methods have been developed for inverter-based resources (IBRs). Initially, research focused on suppressing disturbances such as voltage harmonics, imbalances, phase jumps, and frequency deviations. However, this focus has shifted to ensuring the synchronization stability of weak and faulty grids. This shift is driven by the increasing proportion of IBRs in power systems, which leads to reduced inertia and a lower short-circuit ratio (SCR), ultimately compromising the stability of these resources. Furthermore, traditional synchronization methods for GFM converters face angular stability issues during high-frequency disturbances and lack the necessary GFM characteristics.

[0005] Therefore, an improved solution is needed to at least alleviate some of the problems present in traditional solutions. Summary of the Invention

[0006] The purpose of this disclosure is to provide a control device, power support system, and method for controlling VSCs, which at least mitigates some of the disadvantages of current solutions, improves current solutions in at least one aspect, or provides an alternative to current solutions in at least one aspect. Further, the purpose is preferably to enhance the stability and reliability of grid-connected converters in power systems.

[0007] Another object of this disclosure is preferably to provide an improved control device for a voltage source converter, thereby enabling efficient and stable operation in a power system.

[0008] These and other objectives are achieved, at least in part, by the invention as defined in the independent claims. Preferred embodiments are set forth in the dependent claims. Additional advantageous exemplary embodiments are described below.

[0009] According to a first aspect, a control device for a voltage source converter (VSC) is provided. The VSC is electrically connected to a power system via a point of common coupling (PCC). The control device is configured to provide a voltage reference to the VSC to control the VSC in either a static synchronous compensator (STATCOM) mode or an enhanced STATCOM (i.e., ESTATCOM) mode. The voltage reference is based at least on the phase angle of an internal voltage source (IVS) of the VSC, wherein the IVS phase angle at least indicates the amount of active power exchanged between the VSC and the power system via the PCC. The control device includes a power control loop configured to determine the IVS phase angle based at least on feedforward damping of an energy parameter. The power control loop is further configured to operate in either a first mode corresponding to the STATCOM mode of the VSC or a second mode corresponding to the ESTATCOM mode of the VSC. In the first mode, the power control loop is configured to obtain DC link energy as an energy parameter, wherein the DC link energy indicates the amount of electrical energy exchanged between the DC link energy source of the VSC and the power system. In the second mode, the power control loop is configured to obtain an estimated energy as an energy parameter, wherein the estimated energy corresponds to an active power correction based at least on: active power, an active power reference of active power, and an active power reference correction. The active power reference correction is based at least on the energy correction. The energy correction is based at least on the estimated energy and the DC link energy.

[0010] In other words, this method can take into account DC link energy and, optionally, AC side energy (based on power estimation) to generate a synchronization angle according to the operating mode (STATCOM or ESTATCOM). Therefore, this method provides a robust power synchronization solution for VSCs, enabling them to dampen oscillations and converge to steady state more quickly.

[0011] Furthermore, unlike the feedback concept in traditional methods, this control device provides damping via a feedforward approach. Therefore, no additional loops or circuits are required to provide damping. Additionally, the power control loop (specifically, energy correction) ensures that the energy error always converges to zero. This combination enables enhanced damping and angular stability even under transient conditions.

[0012] In other words, this method also enables VSC to achieve faster and more effective damping after transient events, thereby ensuring the stability of the system and controller.

[0013] This facilitates efficient control of the VSC. This method enables precise management of active power exchange with the power system. The power control loop can be adjusted in real time, ensuring stable operation and minimizing potential disturbances in the power system.

[0014] The power control loop of this control device is further capable of accurately calculating phase angle correction by taking into account both the source phase angle and the IVS phase angle. The energy balancing circuit can resolve and / or compensate for any deviations in energy exchange, thereby maintaining system stability. In other words, the energy balancing circuit enables the system to remain stable and operate within predetermined limits even in the presence of disturbances or errors.

[0015] Energy correction is based at least on DC link energy and estimated energy, enabling the control device to also account for variations in DC link energy, for example, ensuring that the VSC operates within predetermined limits. By incorporating both DC link energy and estimated energy into the energy correction calculation, the control device achieves a comprehensive understanding of energy dynamics.

[0016] Furthermore, this method can eliminate harmonics introduced by the cell DC voltage without any additional control logic. Specifically, the method eliminates the second-order harmonics inherent in the cell DC voltage and maintains the energy balance between the energy storage system and the grid without the need for additional control mechanisms.

[0017] This control device, based at least on phase angle correction, controls the VSC to facilitate precise operational control. By utilizing phase angle correction, the control device can ensure smooth operation of the VSC with the power system, for example, minimizing potential interruptions and ensuring reliable energy exchange.

[0018] The control device can be a power controller, for example, a power synchronization controller.

[0019] Overall, this method enables robust power controllers with inherent frequency and damping control, and achieves an improved GFM control structure, thereby eliminating the need for additional synchronization loops.

[0020] Furthermore, this method improves system stability, enhances performance, and increases efficiency. By providing a robust power synchronization solution, it enables VSC to operate effectively in a variety of applications, thereby ensuring the reliable and stable operation of power systems. This can promote the adoption of VSC in different industries, for example, contributing to the development of more efficient and sustainable energy systems.

[0021] The active power exchanged between the VSC and the power system via the PCC can be determined from the current and voltage measurements at the PCC. The current at the PCC (or other location) can be measured using a current transformer (CT). The voltage at the PCC (or other location) can be measured using a voltage transformer (VT). Current and voltage can be represented as phasors. Active power can be determined as voltage multiplied by current multiplied by the power factor (the cosine of the phase angle between voltage and current). The voltage and current multiplied by the power factor can be the root mean square (RMS) value.

[0022] The power control loop can be configured to obtain an active power reference correction via an energy balancing circuit, which is configured to determine the active power reference correction based at least on the energy correction.

[0023] The power control loop can be configured to determine the active power correction based at least on active power, active power reference, and active power reference correction.

[0024] The power control loop can be configured to determine the estimated energy corresponding to the active power correction.

[0025] The power control loop can be configured to determine a phase angle correction based on the difference between the source phase angle and the phase angle of the internal voltage source IVS, where the source phase angle is the phase angle of the power system, and the IVS phase angle is based at least on the feedforward damping of the estimated energy. The energy correction is based at least on the estimated energy and the DC-DC link energy, which indicates the amount of electrical energy exchanged between the DC-DC link energy source and the power system. The control device can be configured to control the VSC at least based on the phase angle correction.

[0026] According to one embodiment, the active power reference correction is based at least on the difference between the DC link energy and the energy correction scaled by the integral energy gain. The active power reference correction can be provided via an energy balancing circuit.

[0027] An energy balancing circuit can be configured to correct or maintain the energy balance between the DC link energy and the estimated energy. The energy balancing circuit can correct or maintain the energy balance between the DC link energy and the estimated energy via active power reference correction.

[0028] In a non-limiting example, the difference between the DC link energy and the estimated energy can be an energy correction.

[0029] By determining the power reference correction based on the difference between the DC link energy and the estimated energy, the active power reference correction can be accurately calculated. In other words, the difference between the DC link energy and the estimated energy provides an energy correction term. This energy correction can mitigate the mismatch between energy from the DC side and energy sent to the grid. Furthermore, scaling the energy correction by the integral energy gain allows the control equipment to adjust the active power reference correction over time, for example, ensuring that the VSC operates within predetermined limits. This is because theoretical energy (e.g., based on, for example, the system inertia constant (H) and frequency deviation (…)… The difference between the energy calculated using parameters such as (energy) and the actual energy stored in the ESS may result in an energy imbalance.

[0030] According to one embodiment, the IVS phase angle is based at least on a proportional portion of the IVS phase angle provided by a feedforward damping circuit configured to receive energy parameters as input. The energy parameters can depend on the mode of the power control loop. In a first mode, the energy parameters can be DC link energy. In a second mode, the energy parameters can be estimated energy.

[0031] This facilitates more accurate adjustment of the IVS phase angle in response to estimated energy changes, enabling the VSC to respond quickly to changes in the power system. Using feedforward damping circuitry allows for even more precise control of the IVS phase angle, ensuring coordinated operation of the VSC with the power system.

[0032] Overall, using feedforward damping simplifies the definition and understanding of damping phenomena, leading to more effective control. Furthermore, damping achieved through feedforward methods is relatively more effective than traditional feedback-based damping mechanisms. Additionally, integrating feedback control for damping with power limiters can be challenging; therefore, feedforward may be the preferred approach in applications requiring power limiting.

[0033] According to one embodiment, the proportional portion of the IVS phase angle is based at least on an energy parameter scaled proportionally to the gain.

[0034] In other words, the control device can adjust the proportional portion of the IVS phase angle in response to changes in energy parameters. Implementing proportional gain provides a faster response. Using proportional gain allows the control device to fine-tune the proportional portion of the IVS phase angle, for example, ensuring that the VSC operates within predetermined limits.

[0035] The proportional gain defines the damping characteristics of a control device. Specifically, the proportional gain is related to the damped portion of the IVS phase angle, and adjusting this gain directly affects the amount of damping achieved. A higher proportional gain provides more damping. However, if the chosen proportional gain is too high, it can lead to overdamping of the system. Therefore, the proportional gain can be tuned to achieve an optimal balance between damping and stability, as will be explained further in this paper.

[0036] According to one embodiment, the IVS phase angle is further based on the integral portion of the IVS phase angle. The integral portion of the IVS phase angle can be provided by an integrator circuit configured to receive energy parameters as input.

[0037] Therefore, the IVS phase angle can be adjusted over a long period. The integral component allows the control device to account for cumulative changes in energy parameters, for example, ensuring that the VSC operates within predetermined limits.

[0038] The integral terminator serves as a mechanism for tracking the system frequency and adjusting the converter frequency, ensuring, for example, that any frequency deviations or disturbances are corrected. The integral terminator enables the control device to accurately track changes in the system frequency and make necessary adjustments to maintain stability. On the other hand, the proportional terminator provides damping for the system, helping to mitigate oscillations and stabilize the response to frequency disturbances. Therefore, the combination of the integral and proportional terms of the IVS phase angle allows the controller to effectively correct frequency errors and provide a stable output. In other words, the integral term ensures accurate tracking and correction of frequency changes, while the proportional term contributes to the overall damping and stability of the system.

[0039] In a non-limiting example, the proportional portion and the integral portion of the IVS phase angle are added together to generate the final phase angle correction for the IVS. Furthermore, the DC voltage can be used to estimate the available energy, i.e., the DC link energy. Therefore, the DC link energy can be compared with the estimated energy to calculate the phase angle as discussed above.

[0040] According to one embodiment, the integral portion of the IVS phase angle is determined by the integral gain and the subsequent energy integrator.

[0041] This facilitates the accurate calculation of the integral portion of the IVS phase angle using both integral gain and energy integrator. Using integral gain allows the control device to adjust the integral portion of the IVS phase angle over time, thereby ensuring the VSC operates within predetermined limits. Integral gain can track the system frequency. Furthermore, integral gain can ultimately limit the system's inertia.

[0042] According to one embodiment, the IVS phase angle is based at least on the sum of the proportional portion and the integral portion of the IVS phase angle.

[0043] This facilitates more accurate and stable control of the power controller.

[0044] According to one embodiment, the control device further includes an AC voltage controller (AVC) configured to regulate the AC voltage output of the VSC. The AVC can (indirectly) control the reactive power exchanged between the VSC and the power system via the PCC by regulating the AC voltage output.

[0045] By regulating reactive power, AVC helps stabilize the voltage output of VSC, for example, ensuring that it remains within desired limits.

[0046] Therefore, AVC can enhance the ability of VSC to support grid stability, such as in situations where voltage fluctuations may occur. Additionally, regulating reactive power can improve distribution efficiency.

[0047] According to one embodiment, the AVC provides an amplitude voltage based on the reactive power measured at the PCC and a reactive power reference of the reactive power.

[0048] In other words, the AVC can determine the magnitude of the voltage it provides based on the reactive power measured at the PCC and a predefined reactive power reference. The reactive power reference can serve as a target or benchmark for the desired reactive power level. By comparing the reactive power measured at the PCC with this reference, the AVC can adjust the voltage magnitude accordingly to ensure the ideal performance and stability of the VSC.

[0049] Reactive power measured at the PCC can be indirectly measured via voltage and current measurements at the PCC. Reactive power can be determined as voltage multiplied by current multiplied by the sine of the phase angle between the voltage and current. The voltage and current multiplied by the sine of the phase angle can be the root mean square (RMS) value.

[0050] According to one embodiment, the control device is further configured to determine the electromotive force (EMF) based on the IVS phase angle and amplitude voltage.

[0051] In other words, by using the IVS phase angle and voltage amplitude, the control device can obtain the EMF. The determined EMF can represent a measure of the VSC's energy conversion capability.

[0052] Therefore, robust operation of the VSC can be provided, for example, by ensuring that the EMF meets grid requirements.

[0053] According to one embodiment, the voltage reference is further based on the EMF and the virtual admittance determined by the virtual admittance controller VAC.

[0054] In other words, the virtual admittance controller can be configured to adjust the output impedance of the VSC. The output impedance of the VSC can be adjusted based on the virtual impedance.

[0055] In a sense, VAC can be designed to reshape the effective impedance of VSC to provide good and / or adequate damping.

[0056] According to one embodiment, the voltage reference is further based on a current limit of the current between the VSC and the power system. This current can be the current conducted between the VSC and the power system via the PCC.

[0057] Using current limits (i.e., current limiting) allows control devices to prevent excessive current from flowing between the VSC and the power system, thereby protecting both the VSC and the power system from potential damage. In other words, current limits prevent the VSC from operating above a maximum permissible current threshold. In the example, the control device may implement specific current limiting measures to provide additional current limiting protection, such as a current limiting unit configured to limit current propagation between the VSC and the PCC.

[0058] This can further facilitate current limiting in the VSC, thereby protecting the VSC's sensitive power electronics without relying on tripping functions that could impair the VSC's network capability. As an example, the maximum permissible current threshold can be specified by a current limit reference. The current limiting unit can be configured to receive said current reference and provide a processed current reference to the current controller.

[0059] According to one embodiment, the control device is configured to control the VSC at least via a voltage reference of the VSC. The VSC may be a VSC configured to provide power support (active power support and / or reactive power support) to a power system such as a power grid. The power system may be configured for high-voltage (HV) applications and / or medium-voltage (MV) applications and / or low-voltage (LV) applications.

[0060] HV generally refers to voltages exceeding those used in residential and / or commercial applications, with specific thresholds depending on the region. For example, the International Electrotechnical Commission (IEC) typically classifies alternating current (AC) voltages of 1000 V or higher and direct current (DC) voltages of 1500 V or higher as high voltage. More specifically, HV can refer to voltage levels equal to or greater than 35 kV and up to several hundred kilovolts. However, HV can also refer to voltage levels equal to or greater than 115 kV.

[0061] MV typically refers to a voltage level higher than LV but lower than HV. MV generally includes voltages equal to or greater than 1 kV but less than 35 kV. These voltage levels are commonly used in power distribution in urban or industrial environments and in transformers used to transmit power to end-user loads. However, MV can also refer to a voltage level equal to or greater than 10 kV but less than 66 kV (while HV is equal to or greater than 66 kV).

[0062] LV typically refers to the voltage level used in residential, commercial, and light industrial applications. LV generally includes voltages below 1 kV, most commonly 230 V for residential use and 400 V for commercial and industrial applications. LV power lines can be used to distribute electricity directly to end users such as homes, businesses, and small industries. However, LV can also refer to 1000 V or lower (in which case MV is at least greater than 1000 V but less than 35 kV or 66 kV).

[0063] According to a second aspect of this disclosure, a power support system is provided. The power support system includes: a grid-type converter configured to be electrically connected to a power system via a point of common coupling (PCC); and control equipment according to the first aspect or any embodiment of the first aspect.

[0064] This facilitates the creation of integrated power support systems, enabling efficient management of the flow of electrical energy between the grid-connected converter and the power system. The control equipment allows for precise control of the grid-connected converter's operation, ensuring stable and efficient performance.

[0065] Specifically, grid-connected converters can generate voltages and frequencies that support the power system, while control equipment regulates the power exchange between the VSC and the power system.

[0066] The power support system may include multiple VSCs. The control device can be configured to control each VSC individually. The VSCs may be electrically connected or electrically connected to renewable energy sources.

[0067] The second aspect generally presents the same or corresponding advantages as the first aspect.

[0068] According to one embodiment, the VSC of the power support system is configured to be electrically connected to an energy storage system (ESS) and / or operate as a static synchronous compensator (STATCOM). When electrically connected to an ESS, the converter is configured to charge or discharge the ESS to supply active power to the power grid or absorb excess power. When operating as a STATCOM, the converter is configured to provide reactive power compensation by injecting or absorbing reactive power, thereby regulating the voltage at the PCC. The converter can be configured to seamlessly switch between ESS and STATCOM operating modes based on network conditions, thereby enhancing grid stability, supporting voltage regulation, and improving power quality. In particular, the converter can be configured to operate as an E-STATCOM (enhanced STATCOM) by providing both reactive and active power support via the ESS.

[0069] According to a third aspect of this disclosure, a method for controlling a voltage source converter (VSC) is provided. The VSC is electrically connected to a power system via a point of common coupling (PCC). The method includes providing a voltage reference to the VSC to control the VSC in either a Static Synchronous Compensator (STATCOM) mode or an Enhanced STATCOM (i.e., ESTATCOM) mode. The voltage reference is based at least on the phase angle of an internal voltage source (IVS) of the VSC, wherein the IVS phase angle at least indicates the amount of active power exchanged between the VSC and the power system via the PCC. The method further includes: determining the IVS phase angle via a power control loop based at least on feedforward damping of an energy parameter; operating the power control loop in a first mode corresponding to the STATCOM mode of the VSC, or in a second mode corresponding to the ESTATCOM mode of the VSC. In the first mode, the power control loop obtains DC link energy as an energy parameter, wherein the DC link energy indicates the amount of electrical energy exchanged between the DC link energy source of the VSC and the power system. In the second mode, the power control loop obtains an estimated energy as an energy parameter, wherein the estimated energy corresponds to an active power correction based at least on: active power, an active power reference of active power, and an active power reference correction based at least on the energy correction. The energy correction is based at least on the estimated energy and the DC link energy.

[0070] This aspect generally presents the same or corresponding advantages as the previous aspects.

[0071] The method may include obtaining an active power reference correction via a power control loop through an energy balancing circuit, which determines the active power reference correction based at least on the energy correction.

[0072] The method may include determining an active power correction via a power control loop based at least on active power, an active power reference, and an active power reference correction.

[0073] This method may include determining the estimated energy corresponding to the active power correction via a power control loop.

[0074] This method may include determining a phase angle correction via a power control loop based on the difference between the source phase angle and the phase angle of the internal voltage source IVS. The source phase angle may be the phase angle of the power system. The IVS phase angle may be based at least on the feedforward damping of estimated energy.

[0075] This method may include controlling the VSC based at least on phase angle correction. Energy correction may be based at least on estimated energy and DC-DC link energy, which indicates the amount of electrical energy exchanged between the DC-DC link energy source and the power system.

[0076] According to a fourth aspect, a computer-readable storage medium is provided. The computer-readable storage medium includes instructions that, when executed by a computer, cause the computer to perform the method according to the third aspect.

[0077] This aspect generally presents the same or corresponding advantages as the previous aspects.

[0078] The effects and features of the first, second, third, and fourth aspects are substantially similar. The examples mentioned regarding the first, second, and third aspects are substantially compatible. It should further be noted that, unless otherwise expressly stated, this disclosure covers all possible combinations of features.

[0079] Generally, unless otherwise expressly defined herein, all terms used in the claims will be interpreted according to their ordinary meaning in the art. Unless otherwise expressly stated, all references to “a / the [element, device, component, apparatus, step, etc.]” ​​will be openly interpreted as referring to at least one instance of the said element, device, component, step, etc. Attached Figure Description

[0080] The above and other objects, features, and advantages of this disclosure will be better understood through the following illustrative and non-limiting detailed description with reference to the accompanying drawings. In the drawings, unless otherwise specified, the same reference numerals will be used for the same elements.

[0081] Figure 1 A block diagram of the control equipment for a voltage source converter is schematically illustrated. Figure 2 A schematic diagram of the network control scheme is shown, and Figure 3The diagram illustrates a flowchart of a method for controlling a voltage source converter. Detailed Implementation

[0082] The principles of this disclosure will be described below with reference to illustrative embodiments. All these embodiments are given only to enable those skilled in the art to better understand and further practice this disclosure, and not to limit the scope of this disclosure. For example, features illustrated or described as part of one embodiment may be used with another embodiment to produce yet another embodiment. For clarity, not all features of an actual implementation are described in this specification. It should be understood, of course, that in the development of any such actual embodiment, many implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from implementation to implementation. Furthermore, it should be understood that such development work may be complex and time-consuming, but will be a routine task for those skilled in the art who will benefit from this disclosure.

[0083] The disclosed subject matter will now be described with reference to the accompanying drawings. Various structures, systems, and devices are schematically depicted in the drawings for illustrative purposes only and to avoid obscuring the description with details familiar to those skilled in the art. Nevertheless, the drawings are included as illustrative examples for describing and explaining the disclosed subject matter. The words and phrases used herein should be understood and interpreted in accordance with the understanding of those skilled in the art. The consistent use of terms or phrases herein is not intended to imply a specific definition of a term or phrase, i.e., a definition different from the common and customary meaning understood by those skilled in the art. If a term or phrase is intended to have a specific meaning, i.e., a meaning different from that understood by those skilled in the art, such a specific definition will be clearly stated in the specification in a manner that directly and explicitly provides for the specific definition of that term or phrase.

[0084] This disclosure is based on the inventor's understanding that a grid-connected voltage source converter (VSC) system can utilize an internal voltage source (IVS) 130 and subsequent virtual admittance (VSC). To model, for example, Figure 2 This is further illustrated in the text. Within the subsynchronous frequency range, for example, up to 50 Hz, the VSC current can follow a reference current obtained from the virtual admittance controller (VAC) 140. Therefore, the apparent power ( S ) can be represented as: (1) in, These are the PCC voltage and current. yes The phase angle, and j It is the imaginary unit.

[0085] The expression for equation (1) can be linearized as follows: (2) Virtual Admittance It is usually frequency-dependent. However, at relatively low frequencies and when the nominal frequency variation is relatively small, It can be considered as having a constant frequency and can be represented as: (3) In the example, assuming steady state, , And definition The linearized expression in equation (2) can be decomposed into real and imaginary components. These real and imaginary components can then be represented by active and reactive power output relative to the grid voltage magnitude and phase angle, as shown below: (4) According to the expression in equation (4), the open-loop transfer function of the power loop (without filter dynamics) can be written as: (5) Furthermore, it enables control devices to be based on power response. （P） With frequency ( It operates on the principle that energy ( ) is proportional to its time derivative. In other words, energy ( ) W It is proportional to the frequency deviation. This can be expressed mathematically as: (6) Based on the above expression in equation (6), it can be recognized that the control device for the VSC can be designed by combining two integrators, where the first integrator can be used to convert power into energy, and the second integrator can be used to determine the frequency of the IVS. The implementation of this concept is... Figure 1 The diagram is presented in the form of a schematic block diagram.

[0086] Furthermore, in order to correct and / or maintain the energy balance between the energy storage system and the actual energy calculated from the AC side power, an integral gain can be used. K iw Energy balancer circuits, for example, such as Figure 1 As depicted. Therefore, the expression for the IVS phase angle can be expressed as: (7) Substituting the expression in equation (7) into equation (5), the transfer function... G (s This can be expressed as the following standard second-order equation: (8) in, ;and It is the natural oscillation frequency, and It is the damping factor.

[0087] By considering the steady-state power error from (8) and comparing it with equation (6), the proportional-integral gain can be obtained. The expression is as follows: (9) It is worth noting that the same concept can be used to obtain the phase angle in the absence of a VSC with an energy storage system. Therefore, the control device can effectively dampen and avoid any second-order harmonic interference from the unit DC voltage. However, in this case, the expression in equation (6) will be invalid because it can only contribute the minimum inertial power. However, the proportional-integral gain... Then we can obtain the following from equation (8): (10) Furthermore, Figure 2 The AVC of the VSC described in the diagram determines the size of the IVS. As required, the AVC can be based on the reactive power setpoint. Or bus voltage. However, AVC can also be coupled with VAC values ​​and can naturally behave as an integrator, which can be expressed as: (11) in, It is a time constant, and It means The ratio of bandwidth.

[0088] It is worth noting that the grid frequency can limit energy (W). The relationship between energy and frequency can be derived from... Given, among which, H This represents the system's inertia. Additionally, the integral gain (Ki) is... i ) or time constant ( Inertia can be limited ( H The value of ).

[0089] Based on the above, Figure 1 A schematic block diagram depicts a control device 100 for a voltage source converter (VSC) electrically connected to a power system via a point of common coupling (PCC), wherein the control device 100 is configured to control the VSC (see [reference]). Figure 2 Provides a voltage reference (U) refTo control the VSC in either Static Synchronous Compensator (STATCOM) mode or Enhanced STATCOM (ESTATCOM) mode, wherein the voltage reference (U) ref ) is at least based on the phase angle of the internal voltage source IVS of the VSC, where the IVS phase angle ( This at least indicates the amount of active power (P) exchanged between the VSC and the power system via the PCC. For example... Figure 1 As illustrated, the control device 100 includes a power control loop 110 configured to determine the IVS phase angle based at least on the feedforward damping of energy parameters. The power control loop 110 is further configured to operate in a first mode corresponding to the STATCOM mode of the VSC, or in a second mode corresponding to the ESTATCOM mode of the VSC. In the first mode, the power control loop (110) is configured to obtain DC link energy (…). W DC ) is used as an energy parameter, where the energy of the DC link ( W DC This indicates the amount of electrical energy exchanged between the DC link energy source of the VSC and the power system. In the second mode, the power control loop (110) is configured to obtain the estimated energy ( W P ) as an energy parameter, where the estimated energy ( W P ) corresponds to active power correction based on at least the following: P): Active power (P), active power reference (P) of active power (P) ref ), and at least based on energy correction ( Active power reference correction (W) P ref ), of which, energy correction ( W) is at least based on an estimated energy ( W P ) and DC link energy ( W DC ).

[0090] exist Figure 1 In this configuration, the power control loop 110 is further configured to be based on the source phase angle (…). Phase angle with internal voltage source IVS The difference between the two is used to determine the phase angle correction. ).

[0091] Source phase angle ( ) is the phase angle of the power system, and the IVS phase angle ( At least based on feedforward damping of energy parameters.

[0092] Energy Correction ( W) can be based at least on an estimated energy ( W P ) and DC link energy ( W DC The DC link energy indicator represents the amount of electrical energy exchanged between the DC link energy source and the power system.

[0093] Furthermore, in Figure 1 In this configuration, the control device 100 is configured to be based at least on phase angle correction ( Use this to control VSC.

[0094] In the non-limiting example, the active power reference (P) ref The active power reference (P) can be set to zero for generalization. However, the active power reference (P) ref ) can be set to a non-zero value to take into account the specific operating conditions of the VSC and the power system.

[0095] The energy balancing circuit 112 may include additional components such as filters, amplifiers, or signal conditioners to handle energy correction. W) and provides active power reference correction ( Furthermore, the control device 100 can be configured to receive external inputs, such as measurements of the frequency, voltage, or current of the power system, and thereby adjust the active power reference (P) accordingly. ref Current (current at the PCC or other location) can be measured by a current transformer (CT). Voltage (voltage at the PCC or other location) can be measured by a voltage transformer (VT). Frequency can be detected by waveform analysis of the current and / or voltage, which can be performed by control equipment or a separate frequency measurement device. Active power reference correction (… P ref It can also be based on other factors, including but not limited to the VSC's operating mode, the power system's topology, or environmental conditions.

[0096] Control device 100 may further include a communication interface for receiving and / or transmitting, for example, an active power reference (P). ref Energy Correction W) and / or active power reference correction ( P ref The communication interface can be used to coordinate the operation of multiple VSCs connected to the same power system and / or to receive commands from the control center.

[0097] The energy balancing circuit 112 can be further configured to adjust the active power reference correction accordingly. P ref It is used to handle faults or anomalies in the power system, such as voltage drops or frequency deviations.

[0098] In a non-limiting example, control device 100 may include a monitoring and / or recording system to track the performance of the VSC, power system, and / or energy balancing circuit 112. The monitoring and / or recording system may be used, for example, to identify trends, detect anomalies, and / or optimize the operation of the VSC and power system.

[0099] Furthermore, such as Figure 1 The described active power reference correction ( P ref Based on DC link energy ( W DC ) and the energy gain by integration (k iw Scaling energy correction ( W P The difference between them.

[0100] DC link energy ( W DC ) and the energy gain by integration (k iw Scaling energy correction ( W P The difference between (k) and (k) can be calculated using various mathematical operations, including but not limited to subtraction. Integral energy gain (k) iw Active power reference correction ( ) can be a fixed value, an adjustable parameter, or a predetermined variable depending on the operating conditions of the VSC and / or the power system. P ref This can be provided via energy balancing circuit 112. Energy balancing circuit 112 may include additional components such as filters to, for example, calculate the DC link energy (…). W DC ) and energy correction ( W P The differences between them are processed beforehand.

[0101] The energy balancing circuit 112 can be further configured to take into account nonlinear effects in the VSC or power system, such as saturation or hysteresis. This can be achieved, for example, by describing the nonlinear behavior using a mathematical model. Furthermore, the control device 100 can be configured, for example, to adjust the integral energy gain (k...) accordingly. iw ) and active power reference correction ( P refTo adapt to changes in the topology or operating conditions of the power system.

[0102] exist Figure 1 In the middle, IVS phase angle ( Based on the IVS phase angle provided by the feedforward damping circuit 114 ( ) proportion part ( The feedforward damping circuit is configured to receive energy parameters as input. Furthermore, the IVS phase angle ( ) proportion part ( Based on proportional gain (k P ) Scaling of energy parameters. In Figure 1 In this context, the energy parameters depend on the mode of the power control loop 110. In the first mode, the energy parameters are the DC link energy ( W DC In the second mode, the energy parameter is an estimated energy ( ).

[0103] The IVS phase angle provided by the feedforward damping circuit 114 ( ) proportion part ( The feedforward damping circuit 114 can be calculated using various mathematical operations, including but not limited to multiplication. Additional components such as filters, amplifiers, or signal conditioners may be included to process energy parameters and provide the IVS phase angle (…). ).

[0104] Proportional gain (k P This can be, for example, a fixed value, an adjustable parameter, or a predetermined variable depending on the operating conditions of the VSC and / or the power system. Additionally, the feedforward damping circuit 114 can be configured to account for nonlinear effects in the VSC and / or the power system, such as saturation and / or hysteresis. This can be achieved, for example, by describing the nonlinear behavior using a mathematical model.

[0105] Furthermore, the control device 100 can be configured, for example, to adjust the proportional gain (k) accordingly. P ) and IVS phase angle ( To adapt to changes in the topology and / or operating conditions of the power system.

[0106] Additionally, in Figure 1 In the middle, IVS phase angle ( Further based on IVS phase angle ( The integral part of ) Here, the IVS phase angle ( The integral part of ) ) by integral gain (k i ) and the subsequent energy integrator ( )Sure.

[0107] From the integral gain (k i ) and the subsequent energy integrator ( The determined IVS phase angle ( The integral part of ) The integral gain (k) can be calculated using various mathematical operations, including but not limited to integration, multiplication, and / or division. i It can be a fixed value, an adjustable parameter, or a predetermined variable that depends on the operating conditions of the VSC and / or the power system.

[0108] Energy integrator ( () can be a numerical integrator, an analog integrator, or any other suitable integration method.

[0109] exist Figure 1 The diagram also illustrates the IVS phase angle ( The integral part of ) ) and proportional part ( Based on estimated energy ( W P ) or directly based on DC link energy ( W DC In particular, in Figure 1 In the power control circuit 110, there is a switch 116.

[0110] In the example (not explicitly shown in the figure), only the IVS phase angle ( The integral part of ) ) or only its proportionate part ( Selectively based on estimated energy ( W P ) or directly based on DC link energy ( W DC Therefore, in this example, switch 116 can be connected only to the IVS phase angle ( ) proportion part ( The path, or only connected to the IVS phase angle ( The integral part of ) The path of ).

[0111] Switch 116 can, for example, determine the IVS phase angle ( The integral part and / or proportional part of () , ) is based on estimating energy ( W P Or directly based on DC link energy ( W DCIn other words, switch 116 allows the IVS phase angle ( The integral part of ) ) and proportional part ( Based on estimated energy ( W P ) or DC link energy ( W DC Any one of them.

[0112] In a sense, switch 116 can be used when estimating energy ( W P ) or DC link energy ( W DC The selection is made between these options, thereby calculating the IVS phase angle accordingly. The integral part of ) ) and / or proportional portion ( This selection allows control device 100 to operate in different modes, such as STATCOM or ESTATCOM mode. Specifically, switch 116 enables control device 100 to use estimated energy from power calculations (…). W P ) or directly use DC link energy ( W DC Choose between ) and ). In the example, you can choose to estimate the energy ( W P To achieve better performance and / or avoid introducing second-order harmonics from the DC link voltage.

[0113] Switch 116 can be implemented using various technologies, including but not limited to mechanical switches, electronic switches, or software-based switches.

[0114] Although not in Figure 1 As shown, but switch 116 may include additional components such as a signal conditioner to estimate energy ( W P ) and DC link energy ( W DC The estimated energy and / or the DC link energy are processed before making a choice between them.

[0115] In addition, Figure 1 In the middle, IVS phase angle ( At least based on the IVS phase angle ( ) proportion part ( ) and IVS phase angle ( The integral part of ) ) and.

[0116] In the example, control device 100 can be configured to adjust switch 116 accordingly and thus the IVS phase angle ( The integral part of ) ) and / or proportional portion ( To adapt to changes in the topology and / or operating conditions of the power system.

[0117] Furthermore, in Figure 1 In the control device 100, there is an AC voltage controller AVC 120, which is configured to regulate the reactive AC voltage output of the VSC.

[0118] The AVC 120 can be configured to use various control strategies to regulate the AC voltage output of the VSC, including but not limited to integral control and virtual admittance-based control. Control of virtual admittance, proportional-integral-derivative (PID) control, state-space control, and / or model predictive control. Virtual admittance () can be part of AVC 120. This can be, for example, a component of the AVC 120. The AVC 120 may also include additional components such as filters, amplifiers, or signal conditioners to process the AC voltage output and provide a corrected voltage reference. The AVC can (indirectly) control the reactive power exchanged between the VSC and the power system via the PCC by adjusting the AC voltage output.

[0119] The AVC 120 can be configured to account for nonlinear effects in the VSC or power system, such as saturation or hysteresis. This can be achieved, for example, by describing the nonlinear behavior through a mathematical model. Furthermore, the control device 100 can be configured to adapt to changes in the power system topology and / or operating conditions by adjusting the AVC 120 and AC voltage output accordingly.

[0120] The control device 100 can also be configured to coordinate the operation of multiple VSCs connected to the same power system by adjusting the AVC 120 and AC voltage output accordingly.

[0121] Figure 2 A schematic block diagram of the network control scheme is shown. Here, the power control loop 110 and AVC 120 (e.g., as per [reference]) Figure 1 (As described) is communicatively connected to the IVS 130. The output of the IVS 130 then connects to the source voltage (U... S Addition and combination.

[0122] The output of the IVS 130 can be a sinusoidal voltage waveform, a pulse-width modulation (PWM) signal, or any other suitable voltage waveform. Additionally, the source voltage (U...) SVarious sensors can be used for measurement, including but not limited to voltage transformers, electronic voltage transmitters, and / or Hall effect sensors. Alternatively or additionally, capacitive voltage transmitters (CVTs) can be used.

[0123] Although not shown in detail in the figure, the AVC 120 can be based on the reactive power (Q) measured at the PCC and the reactive power reference (Q) of that reactive power (Q). ref ) to provide amplitude voltage (U IVS ).

[0124] The reactive power (Q) measured at the PCC can be calculated using various methods, including but not limited to: processing voltage and current measurements from transmitters such as voltage and current transmitters; extracting the positive-sequence component, for example, through filters such as phase-locked loop (PLL) filters or positive-negative (PN) sequence filters. Other exemplary methods may involve instantaneous power theory, RMS power theory, or fundamental frequency power theory. The reactive power reference (Q) for reactive power (Q) ref It can be set to a fixed value, an adjustable parameter, or a predetermined variable that depends on the operating conditions of the VSC and the power system.

[0125] Additionally, although not shown in the figure, the amplitude voltage (U) IVS Filters can be used to filter noise and / or harmonics, for example.

[0126] Furthermore, the control device 100 can be configured to adjust the reactive power reference (Q) accordingly. ref ), amplitude voltage (U) IVS ) and AVC 120 to adapt to changes in power system topology and / or operating conditions.

[0127] Furthermore, the control device 100 can be configured based on the IVS phase angle ( ) and amplitude voltage (U IVS To determine the electromotive force (EMF).

[0128] Voltage reference (U ref This can then be further based on the EMF and the virtual admittance determined by the virtual admittance controller VAC 140. For example, such as Figure 2 What is depicted.

[0129] Voltage reference (U ref It can be further based on the current limit between the VSC and the power system.

[0130] Therefore, control device 100 may include a current limiting unit (not shown in the figures) configured to apply a current limit to prevent the VSC from operating above a maximum permissible current threshold. This facilitates current limiting of the VSC, thereby protecting the VSC's sensitive power electronics without relying on tripping functions that could impair the VSC's grid-connectivity. As a non-limiting example, the maximum permissible current threshold may be specified by a current limit reference. The current limiting unit may be configured to receive the current reference and provide a processed current reference to the current controller. The processed current reference may be an unadjusted current reference or a current reference adjusted based on the current limit reference.

[0131] Current limits can be adjusted, for example, based on various operating conditions of the VSC and / or the power system. As a non-limiting example, current limits can be based on the rated current of the VSC, the rated power of the VSC, the target current at the PCC, or the target power to be exchanged via the PCC based on operating conditions (such as fault conditions of the power system or VSC). Alternatively or in combination, current limits can be based, for example, on any one or more of active power, reactive power, energy storage power limits, energy storage current limits, energy storage voltage limits, and major component thermal limits.

[0132] Although not explicitly depicted in the figure, the grid-type converter and control device 100, configured to be electrically connected to the power system via the PCC (e.g., as per [reference]), is shown. Figure 1 The described (item) can constitute or form part of an electrical support system.

[0133] In this example, the power support system may include multiple VSCs. Control device 100 may be configured, for example, to control multiple VSCs individually or at least partially uniformly. The VSCs may be electrically connected or electrically connected to renewable energy sources, such as solar power plants or wind power plants.

[0134] The power support system may include multiple grid-connected converters, each connected to a separate power system via a PCC. Therefore, the control device 100 can be configured to coordinate the operation of the multiple grid-connected converters.

[0135] Figure 3 A flowchart is depicted for a method 1000 for controlling a VSC electrically connected to a power system via a PCC.

[0136] exist Figure 3 In the example, method 1000 includes: Provide 1100 voltage reference to VSC (U ref To control the VSC in either Static Synchronous Compensator (STATCOM) mode or Enhanced STATCOM (ESTATCOM) mode, where the voltage reference (U)ref ) is at least based on the phase angle of the internal voltage source IVS of the VSC, where the IVS phase angle ( It at least indicates the amount of active power (P) exchanged between the VSC and the power system via the PCC; The 1200° IVS phase angle is determined via a power control loop based at least on feedforward damping of energy parameters. );as well as The 1300 power control loop can be operated in either the first mode corresponding to the STATCOM mode of the VSC, or in the second mode corresponding to the ESTATCOM mode of the VSC.

[0137] Furthermore, although not in Figure 3 As shown, however, in the first mode, the power control loop obtains DC link energy ( W DC ) as an energy parameter, where DC link energy ( W DC This indicates the amount of electrical energy exchanged between the VSC's DC link energy source and the power system. Additionally, in the second mode, the power control loop obtains an estimated energy ( W P ) as an energy parameter, where the estimated energy ( W P ) corresponds to active power correction based on at least the following: P): Active power (P), active power reference (P) of active power (P) ref ), and at least based on energy correction ( Active power reference correction (W) P ref ), of which, energy correction ( W) is at least based on an estimated energy ( W P ) and DC link energy ( W DC ).

[0138] Furthermore, the power control loop 110 can obtain active power reference correction via the energy balance circuit 112. P ref The energy balancing circuit 112 can be based at least on energy correction ( W) to determine the active power reference correction ( P ref ).

[0139] Furthermore, although not in Figure 3As explained in the text, however, the power control loop 110 can obtain an active power reference correction via the energy balance circuit ( P ref This energy balancing circuit is based at least on energy correction ( W) to determine the active power reference correction ( P ref ).

[0140] The power control loop 110 can be based at least on active power (P) and active power reference (P). ref ) and active power reference correction ( P ref To determine the active power correction ( P); Power control loop 110 can determine the active power correction ( The estimated energy corresponding to P) W P ).

[0141] The power control loop 110 can be based on the source phase angle ( Phase angle with internal voltage source IVS The difference between the two is used to determine the phase angle correction. ), where the source phase angle ( ) is the phase angle of the power system, and the IVS phase angle ( At least based on estimated energy ( W P Feedforward damping.

[0142] The power control loop 110 can be based at least on phase angle correction ( Use this to control VSC.

[0143] It should be understood that the steps of the method 1000 described herein may be performed in any suitable order without departing from the scope of the invention.

[0144] Furthermore, although not shown in the figures, a computer-readable storage medium is provided that includes instructions that, when executed by a computer, cause the computer to perform, for example, actions concerning... Figure 3 Method 1000 as described.

[0145] In the foregoing, this disclosure has been described primarily with reference to a limited number of examples. However, it will be readily understood by those skilled in the art that other examples besides those disclosed above are also possible within the scope of this disclosure as defined by the appended claims.

Claims

1. A control device (100) for a voltage source converter (VSC), the VSC being electrically connected to a power system via a point of common coupling (PCC), wherein, The control device (100) is configured to provide a voltage reference (U) to the VSC. ref To control the VSC in either Static Synchronous Compensator (STATCOM) mode or Enhanced STATCOM (ESTATCOM) mode, wherein the voltage reference (U ref ) is at least based on the phase angle of the internal voltage source IVS of the VSC, wherein the phase angle of the IVS ( The control device (100) at least indicates the amount of active power (P) exchanged between the VSC and the power system via the PCC, and includes: The power control loop (110) is configured to determine the IVS phase angle based at least on the feedforward damping of the energy parameters. ), The power control loop (110) is further configured to operate in a first mode corresponding to the STATCOM mode of the VSC, or in a second mode corresponding to the ESTATCOM mode of the VSC. In the first mode, the power control loop (110) is configured to obtain DC link energy ( W DC ) is used as the energy parameter, wherein the DC link energy ( W DC This indicates the amount of electrical energy exchanged between the DC link energy source of the VSC and the power system. In the second mode, the power control loop (110) is configured to obtain an estimated energy ( W P ) as the energy parameter, wherein the estimated energy ( W P ) corresponds to active power correction based on at least the following: P): The active power (P), the active power reference of the active power (P) ref ), and at least based on energy correction ( Active power reference correction (W) P ref ), wherein the energy correction ( W) is at least based on the estimated energy ( W P ) and the DC link energy ( W DC ).

2. The control device (100) according to claim 1, wherein, The active power reference correction ( P ref At least based on the DC link energy ( W DC ) and the energy gain by integration (k iw The scaled energy correction ( W P The difference between them.

3. The control device (100) according to claim 1 or 2, wherein, The IVS phase angle ( ) at least based on the IVS phase angle provided by the feedforward damping circuit (114) ) proportion part ( The feedforward damping circuit is configured to receive the energy parameters as input.

4. The control device (100) according to any one of claims 1 to 3, wherein, The IVS phase angle ( The proportional portion of ) At least based on proportional gain (k) P The energy parameters are scaled.

5. The control device (100) according to any one of claims 1 to 4, wherein, The IVS phase angle ( Further based on the IVS phase angle ( The integral part of ) ).

6. The control device (100) according to claim 5, wherein, The IVS phase angle ( The integral part of ) ) by integral gain (k i ) and the subsequent energy integrator ( )Sure.

7. The control device (100) according to claim 5 or 6, wherein, The IVS phase angle ( At least based on the IVS phase angle ( The proportional portion of ) ) and the IVS phase angle ( The integral part of ) ) and.

8. The control device (100) according to any one of claims 1 to 7, wherein, The control device (100) further includes an AC voltage controller (AVC) (120) configured to regulate the AC voltage output of the VSC.

9. The control device (100) according to claim 8, wherein, The AVC (120) is based on the reactive power (Q) measured at the PCC and the reactive power reference (Q) of the reactive power (Q). ref ) to provide amplitude voltage (U IVS ).

10. The control device (100) according to claim 9, wherein, The control device (100) is further configured to base its operation on the IVS phase angle ( ) and the amplitude voltage (U) IVS To determine the electromotive force (EMF).

11. The control device (100) according to claim 10, wherein, The voltage reference (U) ref Further based on the EMF and the virtual admittance determined by the virtual admittance controller VAC (140), ).

12. The control device (100) according to any one of claims 1 to 11, wherein, The voltage reference (U) ref Further, based on the current limit between the VSC and the power system.

13. A power support system, comprising: Grid-type converters are configured to be electrically connected to the power system via a point of common coupling (PCC), and The control device (100) according to any one of claims 1 to 12.

14. A method (1000) for controlling a voltage source converter (VSC) electrically connected to a power system via a point of common coupling (PCC), the method (1000) comprising: Provide (1100) voltage reference (U) to the VSC ref To control the VSC in either Static Synchronous Compensator (STATCOM) mode or Enhanced STATCOM (ESTATCOM) mode, wherein the voltage reference (U ref ) is at least based on the phase angle of the internal voltage source IVS of the VSC, wherein the phase angle of the IVS ( It at least indicates the amount of active power (P) exchanged between the VSC and the power system via the PCC; The IVS phase angle (1200) is determined via a power control loop based at least on feedforward damping of energy parameters. );as well as The power control loop can be operated (1300) in a first mode corresponding to the STATCOM mode of the VSC, or in a second mode corresponding to the ESTATCOM mode of the VSC. In the first mode, the power control loop obtains DC link energy ( W DC ) is used as the energy parameter, wherein the DC link energy ( W DC This indicates the amount of electrical energy exchanged between the DC link energy source of the VSC and the power system. In the second mode, the power control loop obtains an estimated energy ( W P ) as the energy parameter, wherein the estimated energy ( W P ) corresponds to active power correction based on at least the following: P): The active power (P), the active power reference of the active power (P) ref ), and at least based on energy correction ( Active power reference correction (W) P ref ), wherein the energy correction ( W) is at least based on the estimated energy ( W P ) and the DC link energy ( W DC ).

15. A computer-readable storage medium comprising instructions that, when executed by a computer, cause the computer to perform the method (1000) according to claim 14.

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