A power grid simulation device capable of dual-mode operation and its control method

Abstract

The present invention relates to the field of power grid simulation technology, and specifically provides a power grid simulation device capable of dual-mode operation and its control method, including: the input side of the power grid simulator is connected to the first switch and then accesses the power grid; the output side of the power grid simulator is connected to the third switch and then accesses the device under test; the connection point between the input side of the power grid simulator and the first switch and the connection point between the output side of the power grid simulator and the third switch access the load status branch; a second switch is connected to the load status branch; a controller for controlling the on / off of the first switch, the second switch, and the third switch and the rectifier side switch signal and the inverter side switch signal of the power grid simulator according to the preset operation mode of the power grid simulation device. The technical solution provided by the present invention expands the operation scenarios of the power grid simulation device and provides technical and equipment support for verifying the grid-connected / off-grid operation capabilities of high-power new energy power generation equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of power grid simulation, and particularly relates to a power grid simulation device capable of dual-mode operation and a control method thereof. Background Art

[0002] The technical requirements for new energy grid connection are continuously increasing, and the performance of unit grid connection test equipment urgently needs to be improved. The power grid simulation device is a key equipment for carrying out new energy unit grid connection tests. Existing research focuses on the system topology and control technology of the power grid simulation device, and proposes structures such as three-phase back-to-back full bridges, H-bridge cascades on the inverter side, and modular multilevel converters based on power electronic converters. The control strategy is basically a method for reproducing power grid faults and disturbances. With the development of grid-forming technology and the offline of prototypes, the unique control performance of grid-forming new energy units urgently needs to be verified. Among them, the independent load-carrying capacity needs to be verified in cooperation with the load device. However, the existing power grid simulation device can only simulate the operation state of the power grid. If a 10MW-class passive load device is developed, it will not only be large in size but also inflexible in control. Developing an independent 10MW-class active load simulation device will incur huge additional costs, and it is difficult to balance economy and flexibility.

[0003] Currently, there are patents researching on power grid simulation, for example:

[0004] The invention patent application "CN115940663A A power grid simulator and its control method" discloses the topology of a power grid simulation device and the control methods of the rectifier circuit and the inverter circuit. This power grid simulation device uses 1 multi-winding transformer on the input side. Through the switching device 60, the inverter current in the conversion unit can be used for reactive power compensation. The output passes through 1 three-phase winding transformer, and the power unit is a typical two-level structure. At the control level, the rectifier circuit controls the DC bus voltage and reactive power compensation, and the inverter circuit controls the direct-axis and quadrature-axis currents on the inverter AC side.

[0005] However, this system uses a multi-winding transformer structure on the input, which is complex in design and not easy to expand the capacity level of the device. The power unit does not consider the multi-level converter structure. The rectifier circuit control and the inverter circuit control are conventional two-level converter control structures. The inverter circuit directly controls the d-axis and q-axis components of the output current, and does not form an effective closed loop for the output voltage of the power grid simulation device, making it difficult to form the ability to simulate positive-sequence and negative-sequence voltage components separately.

[0006] The utility model patent "CN217655214U A high-voltage large-capacity power grid simulation device" discloses a high-voltage large-capacity power grid simulation device. The input side uses a step-down transformer, a multi-level rectifier unit, and a chopper unit. The inverter side uses a multi-level inverter unit and an output filter unit. The capacity of multiple inverters is accumulated through the secondary side cascade of the output-side three-phase transformer, and different power grid characteristics are simulated.

[0007] Although this patent presents a topology of a large-capacity power grid simulation device, its overall structure only considers the requirements during the operation of the simulated power grid, without covering the monitoring and feedback of load power or current when switching to an adjustable AC load, nor does it provide the operation mode and control method of the power grid simulation device as a load simulation device.

[0008] For the invention patent application "CN117411327A A Feed-in Type Split Capacitor Three-Phase Power Electronic Load Compatible with Multiple Requirements", the main circuit uses an AC / DC / AC two-stage back-to-back structure. The front stage is a three-phase four-wire split capacitor type PWM rectifier bridge for simulating the load; the rear stage is a three-phase three-wire PWM inverter bridge for realizing energy feedback; a split capacitor is used on the intermediate side, and a flyback circuit and an SPWM control strategy are adopted to balance the voltage across the capacitor.

[0009] However, this patent presents a topology of a power electronic load simulation device with a two-level structure. The device has a small capacity and is difficult to expand. To achieve voltage equalization of the split capacitor, a voltage division branch is added, but it does not improve the AC power quality level of the two-level structure. At the same time, this topology and control only consider the operation mode as a load and do not cover the operation mode and control strategy of simulating the power grid. Summary of the Invention

[0010] To overcome the above defects, the present invention proposes a power grid simulation device capable of dual-mode operation and its control method.

[0011] In a first aspect, there is provided a power grid simulation device capable of dual-mode operation, where the power grid simulation device capable of dual-mode operation includes:

[0012] A power grid simulator, a first switch, a second switch, a third switch, a load status branch, and a controller;

[0013] The input side of the power grid simulator is connected to the first switch and then connected to the power grid;

[0014] The output side of the power grid simulator is connected to the third switch and then connected to the device under test;

[0015] The connection point between the input side of the power grid simulator and the first switch and the connection point between the output side of the power grid simulator and the third switch are connected to the load status branch;

[0016] The second switch is connected to the load status branch;

[0017] The controller is configured to control the on / off of the first switch, the second switch, and the third switch, as well as the rectifier-side switch signal and the inverter-side switch signal of the power grid simulator according to the preset operation mode of the power grid simulation device.

[0018] Preferably, the power grid simulator includes: an input transformer, a three-level AC / DC converter, a plurality of cascaded three-level DC / AC converters, and a plurality of three-winding transformers;

[0019] The input side of the power grid simulator, the input transformer, and the three-level AC / DC converter are connected in sequence;

[0020] The DC output side of the three-level AC / DC converter is connected to a plurality of cascaded three-level DC / AC converters;

[0021] The plurality of cascaded three-level DC / AC converters are respectively connected to their corresponding three-winding transformers;

[0022] The secondary or primary sides of the windings of the plurality of three-winding transformers are cascaded, and the tails of the last-stage three-phase group transformers are short-circuited together as the output side of the power grid simulator.

[0023] Preferably, the preset operation mode includes at least one of the following: a power grid simulation operation mode and a load simulation operation mode.

[0024] Further, the controller is specifically configured to: when the preset operation mode is the power grid simulation operation mode, close the first switch and the third switch, and open the second switch, and generate a rectifier-side switching signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance, and adopt a positive-sequence and negative-sequence voltage closed-loop control algorithm in the outer loop to generate an inverter-side switching signal of the three-level DC / AC converter.

[0025] Further, generating the rectifier-side switching signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance includes:

[0026] Generating a d-axis current reference value and a q-axis current reference value based on the positive and negative DC bus currents;

[0027] Generating d-axis and q-axis components of an initial modulation voltage based on the d-axis current reference value and the q-axis current reference value;

[0028] Performing dq inverse transformation on the d-axis and q-axis components of the initial modulation voltage to generate a three-phase modulation voltage;

[0029] Generating a final modulation voltage based on the three-phase modulation voltage;

[0030] The final modulation voltage is subjected to PWM modulation to generate a rectifier-side switching signal of the three-level AC / DC converter.

[0031] Further, the d-axis current reference value and the q-axis current reference value are as follows:

[0032]

[0033] In the above formula, and are the reference values of the d-axis current and the q-axis current respectively, and G1(s) is the transfer function of the first PI regulator. is the set DC voltage, and U dc is the DC bus voltage. G LPF (s) is the transfer function of the low-pass filter, and i p , i n are the positive and negative DC bus currents respectively. <�

[0034] Furthermore, the d- and q-axis components of the initial modulation voltage are as follows:

[0035]

[0036] In the above formula, are the d- and q-axis components of the initial modulation voltage respectively, and i gd , i gq are the d- and q-axis components of the AC-side current respectively. G2(s) and G3(s) are the transfer functions of the second and third PI regulators respectively. U gd , U gq are the d- and q-components of the input grid voltage respectively. K d is the decoupling coefficient of the current inner loop on the rectifier side.

[0037] Furthermore, the final modulation voltage is as follows:

[0038]

[0039] In the above formula, is the final modulation voltage. is the three-phase modulation voltage. G4(s) is the transfer function of the fourth PI regulator. U C1 is the voltage of the capacitor between the zero level and the positive level on the DC output side of the three-level AC / DC converter. U C2 is the voltage of the capacitor between the zero level and the negative level on the DC output side of the three-level AC / DC converter.

[0040] Furthermore, the outer loop adopts a positive-sequence and negative-sequence voltage closed-loop control algorithm to generate the inverter-side switching signals of the three-level DC / AC converter, including:

[0041] Performing dq transformation on the positive- and negative-sequence components of the AC-side capacitor voltage of the three-level DC / AC converter to obtain the positive- and negative-sequence components of the capacitor voltage in the dq axis;

[0042] Generating the positive- and negative-sequence components of the current in the dq axis based on the positive- and negative-sequence components of the capacitor voltage in the dq axis;

[0043] Generate the positive and negative sequence components of the modulation voltage based on the positive and negative sequence components of the current in the dq axes;

[0044] Inverse transform the positive and negative sequence components of the modulation voltage in the dq axes to generate the positive and negative sequence components of the three-phase modulation voltage;

[0045] Generate the inverter modulation voltage based on the positive and negative sequence components of the three-phase modulation voltage;

[0046] Obtain the switching signals on the inverter side of the three-level DC / AC converter through carrier phase-shifted modulation of the inverter modulation voltage.

[0047] Furthermore, the positive and negative sequence components of the current in the dq axes are as follows:

[0048]

[0049] In the above formula, and are the positive and negative sequence components of the current in the dq axes respectively, G5(s) and G6(s) are the transfer functions of the fifth and sixth PI regulators respectively, and are the positive and negative sequence components of the given voltage in the dq axes respectively, and are the positive and negative sequence components of the capacitor voltage in the dq axes respectively.

[0050] Furthermore, the positive and negative sequence components of the modulation voltage in the dq axes are as follows:

[0051]

[0052] In the above formula, and are the positive and negative sequence components of the modulation voltage in the dq axes respectively, G7(s) and G8(s) are the transfer functions of the seventh and eighth PI regulators respectively, and are the reference values of the positive and negative sequence components of the current in the dq axes respectively, R v is the given virtual resistance, s is the Laplace operator, L v is the given virtual inductance, and are the positive and negative sequence components of the AC output current in the dq axes respectively.

[0053] Furthermore, the inverter modulation voltage is as follows:

[0054]

[0055] In the above formula, is the inverter modulation voltage, and are the positive and negative sequence components of the three-phase modulation voltage respectively.

[0056] Further, the controller is specifically configured to: when the preset operation mode is the load simulation operation mode, close the first switch and the third switch, and open the second switch, and generate a rectifier side switching signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance, and generate an inverter side switching signal of the three-level DC / AC converter by using a given power load control algorithm.

[0057] Further, the step of generating the inverter side switching signal of the three-level DC / AC converter by using the given power load control algorithm includes:

[0058] Generating d-axis and q-axis components of a modulation voltage based on the output side power of the grid simulator;

[0059] Performing a dq inverse transformation on the d-axis and q-axis components of the modulation voltage to obtain an inverter modulation voltage;

[0060] Performing carrier phase shift modulation on the inverter modulation voltage to obtain an inverter side switching signal of the three-level DC / AC converter.

[0061] Further, the d-axis and q-axis components of the modulation voltage are as follows:

[0062]

[0063] In the above formula, and are the d-axis and q-axis components of the modulation voltage respectively, G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators respectively, P set and Q set are the set active power value and reactive power value of the simulated load respectively, P and Q are the output side active power and reactive power of the grid simulator respectively, and are the d-axis and q-axis component compensations of the AC output voltage respectively, and are the d-axis and q-axis components of the AC output current respectively, K d1 is the compensation coefficient.

[0064] Further, the controller is specifically configured to: when the preset operation mode is the load simulation operation mode, close the first switch, the second switch, and the third switch, and generate a rectifier side switching signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance, and generate an inverter side switching signal of the three-level DC / AC converter by using a follow-up power load control algorithm.

[0065] Further, generating the inverter-side switching signals of the three-level DC / AC converter by using the follow-up power load control algorithm includes:

[0066] Generating the d-axis and q-axis components of the modulation voltage based on the three-phase currents of the load status branch;

[0067] Obtaining the inverter modulation voltage by performing dq inverse transformation on the d-axis and q-axis components of the modulation voltage;

[0068] Obtaining the inverter-side switching signals of the three-level DC / AC converter by performing carrier phase-shifted modulation on the inverter modulation voltage.

[0069] Further, the d-axis and q-axis components of the modulation voltage are as follows:

[0070]

[0071] In the above formula, and are the d-axis and q-axis components of the modulation voltage respectively, G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators respectively, i d_cb2 and i q_cb2 are the d-axis and q-axis components of the current of the load status branch respectively, and are the d-axis and q-axis component compensations of the AC output voltage respectively, and are the d-axis and q-axis components of the AC output current respectively, K d1 is the compensation coefficient.

[0072] In a second aspect, a control method for a grid simulation device capable of dual-mode operation is provided. The grid simulation device capable of dual-mode operation includes:

[0073] The controller controls the on / off of the first switch, the second switch, and the third switch, as well as the rectifier-side switching signals and inverter-side switching signals of the grid simulator according to the preset operation mode of the grid simulation device.

[0074] In a third aspect, a computer device is provided, including: one or more processors;

[0075] The processor is configured to execute one or more programs;

[0076] When the one or more programs are executed by the one or more processors, the control method for the grid simulation device capable of dual-mode operation is implemented.

[0077] In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed, the control method for the grid simulation device capable of dual-mode operation is implemented.

[0078] One or more of the above technical solutions of the present invention have at least one or more of the following beneficial effects:

[0079] The present invention provides a power grid simulation device capable of dual-mode operation and its control method, including: a power grid simulator, a first switch, a second switch, a third switch, a load status branch, and a controller; the input side of the power grid simulator is connected to the first switch and then accesses the power grid; the output side of the power grid simulator is connected to the third switch and then accesses the device under test; the connection point between the input side of the power grid simulator and the first switch and the connection point between the output side of the power grid simulator and the third switch access the load status branch; the second switch is connected to the load status branch; the controller is used to control the on-off of the first switch, the second switch, and the third switch and the rectifier-side switch signal and inverter-side switch signal of the power grid simulator according to the preset operation mode of the power grid simulation device. The technical solution provided by the present invention realizes the dual-mode operation control of the power grid simulation device, expands the application range of the power grid simulation device, saves the investment in independent load devices, simplifies the test process, and can provide technical and equipment support for the construction of new power systems;

[0080] Furthermore, in the power grid simulator of the power grid simulation device capable of dual-mode operation provided by the present invention, the inverter side realizes the improvement of the device capacity through the cascading of multiple converters, and the inverter side capacity can be expanded to the megawatt level; the rectifier side completes the midpoint voltage balance and the fast response to power changes through the closed-loop control of the DC-side current feedback and the capacitor voltage deviation; on the one hand, the inverter side improves the voltage power quality and control accuracy through the positive and negative sequence voltage sequence control, realizes the power grid simulation, and on the other hand, realizes the load simulation through the load power closed-loop control or the load current monitoring and feedback control. Description of the Drawings

[0081] Figure 1 is the main structural schematic diagram of the power grid simulation device capable of dual-mode operation according to the embodiment of the present invention;

[0082] Figure 2 is the schematic diagram of the generation principle of the rectifier-side switch signal of the power grid simulator according to the embodiment of the present invention;

[0083] Figure 3 is the schematic diagram of the generation principle of the inverter-side switch signal of the power grid simulator according to the embodiment of the present invention. Detailed Embodiments

[0084] The following further details the specific embodiments of the present invention with reference to the drawings.

[0085] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0086] Embodiment 1

[0087] Refer to the attached Figure 1 , Figure 1 which is a schematic diagram of the main structure of a grid simulation device capable of dual-mode operation according to an embodiment of the present invention. As Figure 1 shown, the grid simulation device capable of dual-mode operation in the embodiments of the present invention mainly includes: a grid simulator, a first switch CB1, a second switch CB2, a third switch CB3, a load status branch, and a controller;

[0088] The input side of the grid simulator is connected to the first switch and then connected to the power grid;

[0089] The output side of the grid simulator is connected to the third switch and then connected to the device under test;

[0090] The connection point between the input side of the grid simulator and the first switch and the connection point between the output side of the grid simulator and the third switch are connected to the load status branch;

[0091] The second switch is connected to the load status branch;

[0092] The controller is configured to control the on / off of the first switch, the second switch, and the third switch, as well as the rectifier-side switch signal and the inverter-side switch signal of the grid simulator according to the preset operation mode of the grid simulation device.

[0093] In this embodiment, the grid simulator includes: an input transformer, a three-level AC / DC converter, a plurality of cascaded three-level DC / AC converters, and a plurality of three-winding transformers;

[0094] The input side of the grid simulator, the input transformer, and the three-level AC / DC converter are connected in sequence;

[0095] The DC output side of the three-level AC / DC converter is connected to a plurality of cascaded three-level DC / AC converters. For example, n three-level DC / AC converters, and the DC output side outputs three levels, namely, a positive level P, a zero level O, and a negative level N;

[0096] The plurality of cascaded three-level DC / AC converters are respectively connected to their corresponding three-winding transformers;

[0097] The secondary or primary sides of the multiple three-winding transformers are cascaded, and the tails of the last-stage three-phase transformers are shorted together as the output side of the grid simulator.

[0098] In this embodiment, the preset operation mode includes at least one of the following: grid simulation operation mode, load simulation operation mode.

[0099] In one embodiment, the controller is specifically configured to: when the preset operation mode is the grid simulation operation mode, close the first switch and the third switch, and open the second switch, and generate the rectifier-side switching signals of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the medium-voltage balance, and generate the inverter-side switching signals of the three-level DC / AC converter by using a positive-sequence and negative-sequence voltage closed-loop control algorithm in the outer loop.

[0100] In one embodiment, as Figure 2 shown, generating the rectifier-side switching signals of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the medium-voltage balance includes:

[0101] Generating a d-axis current reference value and a q-axis current reference value based on the positive and negative DC bus currents;

[0102] Generating the d- and q-axis components of the initial modulation voltage based on the d-axis current reference value and the q-axis current reference value;

[0103] Performing a dq inverse transformation on the d- and q-axis components of the initial modulation voltage to generate three-phase modulation voltages;

[0104] Generating a final modulation voltage based on the three-phase modulation voltages;

[0105] The final modulation voltage is subjected to PWM modulation to generate the rectifier-side switching signals of the three-level AC / DC converter.

[0106] In one embodiment, the positive and negative DC bus currents are fed forward through a low-pass filter, and the output of the PI of the deviation between the DC bus voltage U dc and the set DC voltage U dc * is superimposed, and together they serve as the d-axis current reference value, and the q-axis current command is set to 0, that is, the d-axis current reference value and the q-axis current reference value are as follows:

[0107]

[0108] In the above formula, and are the d-axis current reference value and the q-axis current reference value respectively, G1(s) is the transfer function of the first PI regulator, is the set DC voltage, U dcis the DC bus voltage, G LPF (s) is the transfer function of the low-pass filter, i p 、i n are the positive and negative DC bus currents respectively.

[0109] In one embodiment, the d- and q-axis components i gd 、i gq of the AC-side current are respectively subtracted from the reference currents i gd *, i gq * and the differences are processed by a regulator to generate the d- and q-axis components of the initial modulation voltage. The d- and q-axis components of the initial modulation voltage are as follows:

[0110]

[0111] In the above formula, are the d- and q-axis components of the initial modulation voltage respectively, i gd 、i gq are the d- and q-axis components of the AC-side current respectively, G2(s) and G3(s) are the transfer functions of the second and third PI regulators respectively, U gd 、U gq are the d- and q-components of the input grid voltage respectively, K d is the decoupling coefficient of the current inner loop on the rectifier side.

[0112] In one embodiment, to achieve the neutral point voltage balance control of capacitors C1 and C2, the voltage U C1 across capacitor C1 and the voltage U C2 across capacitor C2 are subtracted and processed by a PI4 regulator, and then added to the U d *, U q * generated by the dq inverse transformation of the d- and q-axis components of the initial modulation voltage. The sum is used as the final modulation voltage U abc *. The final modulation voltage is as follows: gabc In the above formula,

[0113]

[0114] In the above formula, is the final modulation voltage, is the three-phase modulation voltage, G4(s) is the transfer function of the fourth PI regulator, U C1 is the voltage across capacitor C1 between the zero level and the positive level on the DC output side of the three-level AC / DC converter, U C2 is the voltage across capacitor C2 between the zero level and the negative level on the DC output side of the three-level AC / DC converter. Figure 2 In, i gabc is the three-phase current on the AC side.

[0115] In one embodiment, asFigure 3 As shown, the outer loop adopts a positive-sequence and negative-sequence voltage closed-loop control algorithm to generate the inverter-side switching signals of the three-level DC / AC converter, including:

[0116] The positive-sequence and negative-sequence components of the AC-side capacitor voltage of the three-level DC / AC converter are subjected to dq transformation to obtain the positive-sequence and negative-sequence components of the capacitor voltage on the dq axis;

[0117] Based on the positive-sequence and negative-sequence components of the capacitor voltage on the dq axis, generate the positive-sequence and negative-sequence components of the current on the dq axis;

[0118] Based on the positive-sequence and negative-sequence components of the current on the dq axis, generate the positive-sequence and negative-sequence components of the modulation voltage on the dq axis;

[0119] Inverse dq transform the positive-sequence and negative-sequence components of the modulation voltage on the dq axis to generate the positive-sequence and negative-sequence components of the three-phase modulation voltage;

[0120] Based on the positive-sequence and negative-sequence components of the three-phase modulation voltage, generate the inverter modulation voltage;

[0121] Subject the inverter modulation voltage to carrier phase-shifted modulation to obtain the inverter-side switching signals of the three-level DC / AC converter.

[0122] In one embodiment, the positive-sequence and negative-sequence components of the current on the dq axis are as follows:

[0123]

[0124] In the above formula, and are the positive-sequence and negative-sequence components of the current on the dq axis respectively, G5(s) and G6(s) are the transfer functions of the fifth and sixth PI regulators respectively, and are the positive-sequence and negative-sequence components of the given voltage on the dq axis respectively, and are the positive-sequence and negative-sequence components of the capacitor voltage on the dq axis respectively.

[0125] In one embodiment, the positive-sequence and negative-sequence components of the modulation voltage on the dq axis are as follows:

[0126]

[0127] In the above formula, and are the positive-sequence and negative-sequence components of the modulation voltage on the dq axis respectively, G7(s) and G8(s) are the transfer functions of the seventh and eighth PI regulators respectively, and are the reference values of the positive-sequence and negative-sequence components of the current on the dq axis respectively, R v is the given virtual resistance, s is the Laplace operator, L v is the given virtual inductance, and are the positive and negative sequence components of the dq axes of the AC output current, respectively.

[0128] In one embodiment, the inverter modulates the voltage as follows:

[0129]

[0130] In the above formula, is the inverter modulation voltage, and are the positive and negative sequence components of the three-phase modulation voltage, respectively.

[0131] In one embodiment, the controller is specifically configured to: when the preset operation mode is the load simulation operation mode and, close the first switch and the third switch, and open the second switch, so as to generate the rectifier side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the medium voltage balance, and generate the inverter side switch signal of the three-level DC / AC converter by using the given power load control algorithm.

[0132] In one embodiment, generating the inverter side switch signal of the three-level DC / AC converter by using the given power load control algorithm includes:

[0133] Generating the dq axis components of the modulation voltage based on the output side power of the grid simulator;

[0134] Performing dq inverse transformation on the dq axis components of the modulation voltage to obtain the inverter modulation voltage;

[0135] Performing carrier phase shift modulation on the inverter modulation voltage to obtain the inverter side switch signal of the three-level DC / AC converter, so as to realize the given power load simulation.

[0136] In one embodiment, collecting the output side voltage and current of the grid simulation device, that is, Figure 1 the port voltage and the flowing current of CB3 in, calculating the total active power P and reactive power Q, and respectively taking the differences with the set active value P of the simulated load set 、Q set and sending them into the PI regulator. The output of the PI regulator is superimposed on the dq component compensation link of the AC output current. In order to improve the response dynamics, the AC voltage feedforward method is adopted, and the dq axis components of the modulation voltage can be obtained as follows:

[0137]

[0138] In the above formula, and are the d and q axis components of the modulation voltage, respectively, and G9(s) and G 10(s) are the transfer functions of the ninth and tenth PI regulators, respectively, P set and Q set are the set active power value and reactive power value of the simulated load, respectively. P and Q are the active power and reactive power on the output side of the grid simulator, and are the d and q component compensations of the AC output voltage, respectively, and are the d and q components of the AC output current, respectively. K d1 is the compensation coefficient.

[0139] In one embodiment, the controller is specifically configured to: when the preset operation mode is the load simulation operation mode, close the first switch, the second switch, and the third switch, generate the rectifier side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the medium voltage balance, and generate the inverter side switch signal of the three-level DC / AC converter by using the follow-up power load control algorithm.

[0140] In one embodiment, generating the inverter side switch signal of the three-level DC / AC converter by using the follow-up power load control algorithm includes:

[0141] Generating the dq-axis components of the modulation voltage based on the three-phase current of the load status branch;

[0142] Performing dq inverse transformation on the dq-axis components of the modulation voltage to obtain the inverter modulation voltage;

[0143] Performing carrier phase-shifted modulation on the inverter modulation voltage to obtain the inverter side switch signal of the three-level DC / AC converter.

[0144] In one embodiment, the three-phase current i of the load status branch is collected abc_cb2 , and the d and q components i of the current are obtained through dq transformation d_cb2 and i q_cb2 , and the two are respectively compared with 0. The deviation is sent to the PI regulator. The output of the PI regulator is superimposed on the dq component compensation link of the AC output current. At the same time, to improve the response dynamics, the AC voltage feedforward method is used. The dq-axis components of the modulation voltage can be obtained as follows:

[0145]

[0146] In the above formula, and are the d and q axis components of the modulation voltage, respectively. G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators, respectively. i d_cb2 and i q_cb2 are the current d and q axis components of the load status branch, respectively. and are the d - component and q - component compensations of the AC output voltage respectively, and are the d - component and q - component of the AC output current respectively, and K d1 is the compensation coefficient.

[0147] The specific control block diagram is as shown in Figure 3 When the selection switch K1 is in position a, it operates in the grid simulation mode. When K1 is in position b and K2 is in position 1, it operates in the given power load simulation mode. When K1 is in position b and K2 is in position 2, it operates in the follow - up power load simulation mode. Figure 3 Among them, U mabc and I mabc are the three - phase voltage and current of the inverter respectively.

[0148] Embodiment 2

[0149] The present invention provides a control method for a grid simulation device capable of dual - mode operation. The grid simulation device capable of dual - mode operation includes:

[0150] The controller controls the on - off of the first switch, the second switch and the third switch, as well as the rectifier - side switch signal and the inverter - side switch signal of the grid simulator according to the preset operation mode of the grid simulation device.

[0151] Preferably, the preset operation mode includes at least one of the following: grid simulation operation mode, load simulation operation mode.

[0152] Further, when the preset operation mode is the grid simulation operation mode, close the first switch and the third switch, and open the second switch. Generate the rectifier - side switch signal of the three - level AC / DC converter with the goal of stabilizing the DC bus voltage and the mid - point voltage balance, and generate the inverter - side switch signal of the three - level DC / AC converter by using the positive - sequence and negative - sequence voltage closed - loop control algorithm in the outer loop.

[0153] Further, the generating of the rectifier - side switch signal of the three - level AC / DC converter with the goal of stabilizing the DC bus voltage and the mid - point voltage balance includes:

[0154] Generate the d - axis current reference value and the q - axis current reference value based on the positive and negative DC bus currents;

[0155] Generate the d - axis and q - axis components of the initial modulation voltage based on the d - axis current reference value and the q - axis current reference value;

[0156] Generate the three - phase modulation voltage by performing dq inverse transformation on the d - axis and q - axis components of the initial modulation voltage;

[0157] Generate the final modulation voltage based on the three - phase modulation voltage;

[0158] The final modulation voltage generates the rectifier - side switching signals of the three - level AC / DC converter through PWM modulation.

[0159] Furthermore, the d - axis current reference value and q - axis current reference value are as follows:

[0160]

[0161] In the above formula, and are the d - axis current reference value and q - axis current reference value respectively, G1(s) is the transfer function of the first PI regulator, is the set DC voltage, U dc is the DC bus voltage, G LPF (s) is the transfer function of the low - pass filter, i p 、i n are the positive and negative DC bus currents respectively.

[0162] Furthermore, the d - and q - axis components of the initial modulation voltage are as follows:

[0163]

[0164] In the above formula, are the d - and q - axis components of the initial modulation voltage respectively, i gd 、i gq are the d - and q - axis components of the AC - side current respectively, G2(s) and G3(s) are the transfer functions of the second and third PI regulators respectively, U gd 、U gq are the d - and q - components of the input grid voltage respectively, K d is the decoupling coefficient of the rectifier - side current inner loop.

[0165] Furthermore, the final modulation voltage is as follows:

[0166]

[0167] In the above formula, is the final modulation voltage, is the three - phase modulation voltage, G4(s) is the transfer function of the fourth PI regulator, U C1 is the voltage of the capacitor between the zero level and the positive level on the DC output side of the three - level AC / DC converter, U C2 is the voltage of the capacitor between the zero level and the negative level on the DC output side of the three - level AC / DC converter.

[0168] Furthermore, the outer loop adopts a positive - sequence and negative - sequence voltage closed - loop control algorithm to generate the inverter - side switching signals of the three - level DC / AC converter, including:

[0169] The positive and negative sequence components of the AC-side capacitor voltage of the three-level DC / AC converter are subjected to dq transformation to obtain the positive and negative sequence components of the capacitor voltage on the dq axes;

[0170] Based on the positive and negative sequence components of the capacitor voltage on the dq axes, generate the positive and negative sequence components of the current on the dq axes;

[0171] Based on the positive and negative sequence components of the current on the dq axes, generate the positive and negative sequence components of the modulation voltage on the dq axes;

[0172] Perform dq inverse transformation on the positive and negative sequence components of the modulation voltage on the dq axes to generate the positive and negative sequence components of the three-phase modulation voltage;

[0173] Based on the positive and negative sequence components of the three-phase modulation voltage, generate the inverter modulation voltage;

[0174] Subject the inverter modulation voltage to carrier phase-shifted modulation to obtain the inverter-side switching signals of the three-level DC / AC converter.

[0175] Furthermore, the positive and negative sequence components of the current on the dq axes are as follows:

[0176]

[0177] In the above formula, and are the positive and negative sequence components of the current on the dq axes respectively, G5(s) and G6(s) are the transfer functions of the fifth and sixth PI regulators respectively, and are the positive and negative sequence components of the given dq-axis voltages respectively, and are the positive and negative sequence components of the capacitor voltage on the dq axes respectively.

[0178] Furthermore, the positive and negative sequence components of the modulation voltage on the dq axes are as follows:

[0179]

[0180] In the above formula, and are the positive and negative sequence components of the modulation voltage on the dq axes respectively, G7(s) and G8(s) are the transfer functions of the seventh and eighth PI regulators respectively, and are the reference values of the positive and negative sequence components of the current on the dq axes respectively, R v is the given virtual resistance, s is the Laplace operator, L v is the given virtual inductance, and are the positive and negative sequence components of the AC output current on the dq axes respectively.

[0181] Furthermore, the modulation voltage of the inverter is as follows:

[0182]

[0183] In the above formula, is the modulation voltage of the inverter, and are the positive and negative sequence components of the three-phase modulation voltage respectively.

[0184] Furthermore, when the preset operation mode is the load simulation operation mode and, close the first switch and the third switch, and disconnect the second switch, generate the rectifier side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the medium voltage balance, and generate the inverter side switch signal of the three-level DC / AC converter by using the given power load control algorithm.

[0185] Furthermore, generating the inverter side switch signal of the three-level DC / AC converter by using the given power load control algorithm includes:

[0186] Generate the dq-axis components of the modulation voltage based on the output side power of the grid simulator;

[0187] Obtain the inverter modulation voltage by performing dq inverse transformation on the dq-axis components of the modulation voltage;

[0188] Obtain the inverter side switch signal of the three-level DC / AC converter by performing carrier phase shift modulation on the inverter modulation voltage.

[0189] Furthermore, the dq-axis components of the modulation voltage are as follows:

[0190]

[0191] In the above formula, and are the d and q axis components of the modulation voltage respectively, G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators respectively, P set and Q set are the set active power value and reactive power value of the simulated load respectively, P and Q are the output side active and reactive powers of the grid simulator respectively, and are the d and q component compensations of the AC output voltage respectively, and are the d and q components of the AC output current respectively, K d1 is the compensation coefficient.

[0192] Further, when the preset operation mode is the load simulation operation mode, close the first switch, the second switch, and the third switch, generate the rectifier-side switching signals of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the medium-voltage balance, and generate the inverter-side switching signals of the three-level DC / AC converter by using the follow-up power load control algorithm.

[0193] Further, the generating of the inverter-side switching signals of the three-level DC / AC converter by using the follow-up power load control algorithm includes:

[0194] Generate the dq-axis components of the modulation voltage based on the three-phase currents of the load state branch;

[0195] Obtain the inverter modulation voltage by performing dq inverse transformation on the dq-axis components of the modulation voltage;

[0196] Obtain the inverter-side switching signals of the three-level DC / AC converter by performing carrier phase-shifted modulation on the inverter modulation voltage.

[0197] Further, the dq-axis components of the modulation voltage are as follows:

[0198]

[0199] In the above formula, and are the d-axis and q-axis components of the modulation voltage respectively, G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators respectively, i d_cb2 and i q_cb2 are the d-axis and q-axis components of the current of the load state branch respectively, and are the d-axis and q-axis component compensations of the AC output voltage respectively, and are the d-axis and q-axis components of the AC output current respectively, K d1 is the compensation coefficient.

[0200] Embodiment 3

[0201] Based on the same inventive concept, the present invention further provides a computer device, which includes a processor and a memory. The memory is used to store a computer program, and the computer program includes program instructions. The processor is used to execute the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or may also be other general-purpose processors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, and is adapted to implement one or more instructions. Specifically, it is adapted to load and execute one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function, so as to implement the steps of the control method of a power grid simulation device capable of dual-mode operation in the above embodiments.

[0202] Embodiment 4

[0203] Based on the same inventive concept, the present invention further provides a storage medium, specifically a computer-readable storage medium (Memory). The computer-readable storage medium is a memory device in the computer device and is used to store programs and data. It can be understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and, of course, the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, and the operating system of the terminal is stored in this storage space. And, one or more instructions suitable for being loaded and executed by the processor are also stored in this storage space. These instructions may be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The one or more instructions stored in the computer-readable storage medium can be loaded and executed by the processor to implement the steps of the control method of a power grid simulation device capable of dual-mode operation in the above embodiments.

[0204] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that contain computer-usable program code.

[0205] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to the embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, as well as the combination of flows and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0206] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that implement the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0207] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process. Thus, the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in Figure 1 one flow or multiple flows and / or blocks Figure 1 one block or multiple blocks.

[0208] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: still can modify the specific implementation manners of the present invention or make equivalent replacements, and any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A power grid simulation device capable of dual-mode operation, characterized in that, The device includes: a power grid simulator, a first switch, a second switch, a third switch, a load status branch, and a controller; The input side of the power grid simulator is connected to the first switch and then connected to the power grid; The output side of the power grid simulator is connected to the third switch and then connected to the device under test; The connection point between the input side of the power grid simulator and the first switch and the connection point between the output side of the power grid simulator and the third switch are connected to the load status branch; The second switch is connected to the load status branch; The controller is used to control the on / off of the first switch, the second switch, and the third switch, as well as the rectifier side switch signal and the inverter side switch signal of the power grid simulator according to the preset operation mode of the power grid simulation device; The power grid simulator includes: an input transformer, a three-level AC / DC converter, a plurality of cascaded three-level DC / AC converters, and a plurality of three-winding transformers; The input side of the power grid simulator, the input transformer, and the three-level AC / DC converter are connected in sequence; The DC output side of the three-level AC / DC converter is connected to a plurality of cascaded three-level DC / AC converters; The plurality of cascaded three-level DC / AC converters are respectively connected to their corresponding three-winding transformers; The secondary or primary sides of the windings of the plurality of three-winding transformers are cascaded, and the tails of the last-stage three-phase group transformers are short-circuited together as the output side of the power grid simulator; The preset operation mode includes at least one of the following: a power grid simulation operation mode, a load simulation operation mode; Specifically, the controller is configured to: when the preset operation mode is the power grid simulation operation mode, close the first switch and the third switch, open the second switch, generate a rectifier side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance, and generate an inverter side switch signal of the three-level DC / AC converter by using a positive sequence and negative sequence voltage closed-loop control algorithm for the outer loop; Specifically, the controller is configured to: when the preset operation mode is the load simulation operation mode, close the first switch and the third switch, open the second switch, generate a rectifier side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance, and generate an inverter side switch signal of the three-level DC / AC converter by using a given power load control algorithm.

2. The device according to claim 1, characterized in that, Generating the rectifier side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the neutral point voltage balance includes: Generating a d-axis current reference value and a q-axis current reference value based on the positive and negative DC bus currents; Generating the d-axis and q-axis components of the initial modulation voltage based on the d-axis current reference value and the q-axis current reference value; Performing a dq inverse transformation on the d-axis and q-axis components of the initial modulation voltage to generate a three-phase modulation voltage; Generating a final modulation voltage based on the three-phase modulation voltage; The final modulation voltage is subjected to PWM modulation to generate a rectifier side switch signal of the three-level AC / DC converter.

3. The device according to claim 2, characterized in that, The d-axis current reference value and the q-axis current reference value are as follows: In the above formula, and are the reference values of the d-axis current and the q-axis current respectively, and G1(s) is the transfer function of the first PI regulator. is the set DC voltage, U dc is the DC bus voltage, and G LPF (s) is the transfer function of the low-pass filter. i p and i n are the positive and negative DC bus currents respectively.

4. The device according to claim 3, characterized in that, The d-axis and q-axis components of the initial modulation voltage are as follows: In the above formula, are the d-axis and q-axis components of the initial modulation voltage, respectively, and i gd , i gq are the d-axis and q-axis components of the AC-side current, respectively. G2(s) and G3(s) are the transfer functions of the second and third PI regulators, respectively. U gd , U gq are the d-axis and q-axis components of the input grid voltage, respectively. K d is the decoupling coefficient of the current inner loop on the rectifier side.

5. The device according to claim 4, characterized in that, The final modulation voltage is as follows: In the above formula, is the final modulation voltage, is the three-phase modulation voltage, G4(s) is the transfer function of the fourth PI regulator, U C1 is the voltage of the capacitor between the zero level and the positive level on the DC output side of the three-level AC / DC converter, U C2 is the voltage of the capacitor between the zero level and the negative level on the DC output side of the three-level AC / DC converter.

6. The device according to claim 1, characterized in that, The outer loop adopts a positive-sequence and negative-sequence voltage closed-loop control algorithm to generate the inverter-side switching signals of the three-level DC / AC converter, including: Performing dq transformation on the positive-sequence and negative-sequence components of the AC-side capacitor voltage of the three-level DC / AC converter to obtain the positive-sequence and negative-sequence components of the capacitor voltage on the dq axis; Generating the positive-sequence and negative-sequence components of the current on the dq axis based on the positive-sequence and negative-sequence components of the capacitor voltage on the dq axis; Generating the positive-sequence and negative-sequence components of the modulation voltage on the dq axis based on the positive-sequence and negative-sequence components of the current on the dq axis; Performing inverse dq transformation on the positive-sequence and negative-sequence components of the modulation voltage on the dq axis to generate the positive-sequence and negative-sequence components of the three-phase modulation voltage; Generating the inverter modulation voltage based on the positive-sequence and negative-sequence components of the three-phase modulation voltage; Subjecting the inverter modulation voltage to carrier phase-shifted modulation to obtain the inverter-side switching signals of the three-level DC / AC converter.

7. The device according to claim 6, characterized in that The positive-sequence and negative-sequence components of the current on the dq axis are as follows: In the above formula, and are the positive and negative sequence components of the dq-axis current respectively, and G5(s) and G6(s) are the transfer functions of the fifth and sixth PI regulators respectively. and are the positive and negative sequence components of the given dq-axis voltage respectively. and are the positive and negative sequence components of the dq-axis capacitor voltage respectively.

8. The device according to claim 7, characterized in that, The positive-sequence and negative-sequence components of the modulation voltage on the dq axis are as follows: In the above formula, and are the positive and negative sequence components of the dq-axis of the modulation voltage respectively, and G7(s) and G8(s) are the transfer functions of the seventh and eighth PI regulators respectively. and are the reference values of the positive and negative sequence components of the dq-axis of the current respectively, R v is the given virtual resistance, s is the Laplace operator, and L v is the given virtual inductance. and are the positive and negative sequence components of the dq-axis of the AC output current respectively.

9. The device according to claim 8, characterized in that The inverter modulation voltage is as follows: In the above formula, is the inverter modulation voltage, and are the positive and negative sequence components of the three-phase modulation voltage, respectively.

10. The device according to claim 9, characterized in that, The method of adopting a given power load control algorithm to generate the inverter-side switching signals of the three-level DC / AC converter includes: Generating the dq-axis components of the modulation voltage based on the output-side power of the grid simulator; Performing inverse dq transformation on the dq-axis components of the modulation voltage to obtain the inverter modulation voltage; Subjecting the inverter modulation voltage to carrier phase-shifted modulation to obtain the inverter-side switching signals of the three-level DC / AC converter.

11. The device according to claim 10, wherein The dq-axis components of the modulation voltage are as follows: In the above formula, and are the d-axis and q-axis components of the modulation voltage respectively. G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators respectively. P set and Q set are the set active power value and reactive power value of the simulated load respectively. P and Q are the active power and reactive power on the output side of the grid simulator respectively. and are the d-axis and q-axis component compensations of the AC output voltage respectively. and are the d-axis and q-axis components of the AC output current respectively. K d1 is the compensation coefficient.

12. The device according to claim 1, characterized in that, The controller is specifically configured to: when the preset operation mode is the load simulation operation mode, close the first switch, the second switch, and the third switch, and generate the rectifier-side switching signals of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and the midpoint voltage balance, and adopt a follow-up power load control algorithm to generate the inverter-side switching signals of the three-level DC / AC converter.

13. The device according to claim 12, characterized in that, The method of adopting a follow-up power load control algorithm to generate the inverter-side switching signals of the three-level DC / AC converter includes: Generating the dq-axis components of the modulation voltage based on the three-phase current of the load status branch; Performing inverse dq transformation on the dq-axis components of the modulation voltage to obtain the inverter modulation voltage; Subjecting the inverter modulation voltage to carrier phase-shifted modulation to obtain the inverter-side switching signals of the three-level DC / AC converter.

14. The device according to claim 13, characterized in that, The dq-axis components of the modulation voltage are as follows: In the above formula, and are the d-axis and q-axis components of the modulation voltage respectively, G9(s) and G 10 (s) are the transfer functions of the ninth and tenth PI regulators respectively, i d_cb2 and i q_cb2 are the d-axis and q-axis components of the current in the load state branch respectively, and are the d-axis and q-axis component compensations of the AC output voltage respectively, and are the d-axis and q-axis components of the AC output current respectively, K d1 is the compensation coefficient.

15. A control method for a power grid simulation device capable of dual-mode operation according to any one of claims 1-14, characterized in that, The method includes: The controller controls the on / off of the first switch, the second switch, and the third switch, as well as the rectifier-side switching signals and inverter-side switching signals of the grid simulator according to the preset operation mode of the grid simulation device.

16. A computer device, characterized in that, Including: One or more processors; The processor is used to execute one or more programs; When the one or more programs are executed by the one or more processors, the control method of the grid simulation device capable of dual-mode operation as described in claim 15 is implemented.

17. A computer-readable storage medium, characterized in that, A computer program is stored thereon, and when the computer program is executed, the control method of the grid simulation device capable of dual-mode operation as described in claim 15 is implemented.

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