Power grid simulation device capable of operating in dual modes and control method thereof

Abstract

The invention relates to the technical field of power grid simulation, and particularly provides a power grid simulation device capable of operating in dual modes and a control method thereof, and the method comprises the steps: connecting an input side of a power grid simulator with a first switch and then accessing a power grid; the output side of the power grid simulator is connected with a third switch and then connected to the tested equipment; a connection point between the input side of the power grid simulator and the first switch and a connection point between the output side of the power grid simulator and the third switch are connected to a load state branch; the load state branch is connected with a second switch; and the controller is used for controlling the on-off of the first switch, the second switch and the third switch and the rectification side switching signal and the inversion side switching signal of the power grid simulator according to a preset operation mode of the power grid simulation device. According to the technical scheme provided by the invention, the operation scene of the power grid simulation device is expanded, and technical and equipment support is provided for grid-connected / off-grid operation capability verification 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 in particular to a power grid simulation device capable of dual-mode operation and a control method thereof. Background Art

[0002] The technical requirements for grid-connected renewable energy sources are constantly increasing, and the performance of grid-connected test equipment for units needs to be improved urgently. The grid simulator is a key equipment for conducting grid-connected tests of renewable energy units. Existing research focuses on the system topology and control technology of the grid simulator, and proposes structures such as three-phase back-to-back full-bridge, inverter-side H-bridge cascade, and modular multi-level based on power electronic converters. The control strategy is basically a method to reproduce grid faults and disturbances. With the development of grid-connected technology and the launch of prototypes, the unique control performance of grid-connected renewable energy units needs to be verified urgently, among which the independent load-carrying capacity needs to be verified with the load device. However, the existing grid simulator can only simulate the operating status of the grid. If a 10MW-class passive load device is developed, it will not only be large in size but also inflexible in control. The development of an independent 10MW-class active load simulator will add huge costs, and it is difficult to balance economy and flexibility.

[0003] Currently, there are patents for research on power grid simulation, such as:

[0004] The invention patent application "CN115940663A A power grid simulator and its control method" discloses a topology of a power grid simulation device and a control method of a rectifier circuit and an inverter circuit. The power grid simulation device uses a multi-winding transformer on the input side. The inverter current in the converter unit can be used for reactive power compensation through a switch device 60. The output is through a 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, the system input adopts a multi-winding transformer structure, which is complex in design and difficult to expand the capacity level of the device. The power unit does not consider the multi-level converter structure, and the rectifier circuit control and 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 positive-sequence and negative-sequence voltage sequence simulation capabilities.

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

[0007] Although this patent provides a topology for a large-capacity power grid simulation device, its overall structure only considers the requirements of simulating power grid operation. It does not involve load power or current monitoring and feedback 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] The invention patent application "CN117411327A A kind of energy-fed split-capacitor three-phase power electronic load compatible with multiple needs" uses an AC / DC / AC two-stage back-to-back structure in the main circuit. The front stage is a three-phase four-wire split-capacitor PWM rectifier bridge to simulate the load; the rear stage is a three-phase three-wire PWM inverter bridge to achieve energy feedback; a split capacitor is used in the middle side, and a flyback circuit and SPWM control strategy are used to control the voltage across the capacitor.

[0009] However, the patent provides a two-level structure of power electronic load simulation device topology, the device capacity is small and difficult to expand; in order to achieve split capacitor voltage balancing, a voltage dividing branch is added, which does not improve the AC power quality level of the two-level structure. At the same time, the topology and control only consider the load operation mode, and do not involve the operation mode and control strategy of the simulated power grid. Summary of the invention

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

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

[0012] A power grid simulator, a first switch, a second switch, a third switch, a load state 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] A connection point between the input side of the power grid simulator and the first switch and a connection point between the output side of the power grid simulator and the third switch are connected to a load state branch;

[0016] The load state branch is connected to a second switch;

[0017] The controller is used to control the on and 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 a preset operating mode of the power grid simulation device.

[0018] Preferably, the power grid simulator comprises: 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 windings of the multiple three-winding transformers are cascaded, and the tails of the final three-phase transformers are short-connected together to serve 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] Furthermore, the controller is specifically used to: when the preset operating mode is the power grid simulation operating 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 medium power voltage balance, and use the outer loop to use the positive sequence and negative sequence voltage closed-loop control algorithm to generate the inverter side switch signal of the three-level DC / AC converter.

[0025] Furthermore, the step of generating a rectifier-side switch signal of a three-level AC / DC converter with the goal of stabilizing the DC bus voltage and balancing the medium power voltage includes:

[0026] Generate a d-axis current reference value and a q-axis current reference value based on the positive and negative direct 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] The d-axis and q-axis components of the initial modulation voltage are subjected to dq inverse transformation 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 modulated by PWM to generate the rectifier-side switching signal of the three-level AC / DC converter.

[0031] Furthermore, 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 d-axis current reference value and the q-axis current reference value respectively, G1(s) is the first PI regulator transfer function, To set the DC voltage, U dc is the DC bus voltage, G LPF (s) is the low-pass filter transfer function, i p 、i n are the positive and negative DC bus currents respectively.

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

[0035]

[0036] In the above formula, are the d-axis and q-axis components of the initial modulation voltage, respectively, i gd 、i gq are the d-axis and q-axis components of the AC side current, G2(s) and G3(s) are the transfer functions of the second and third PI regulators, respectively. gd , U gq are the d and q components of the input grid voltage, respectively, K d is the decoupling coefficient of the inner loop current 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 It 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] Further, the outer loop adopts a positive sequence and negative sequence voltage closed loop control algorithm to generate an inverter side switch signal of a three-level DC / AC converter, including:

[0041] The positive and negative sequence components of the capacitor voltage on the AC side of the three-level DC / AC converter are transformed by dq to obtain the positive and negative sequence components of the capacitor voltage on the dq axis;

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

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

[0044] Inversely transforming the dq axis positive and negative sequence components dq of the modulation voltage to generate positive and negative sequence components of the three-phase modulation voltage;

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

[0046] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

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

[0048]

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

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

[0051]

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

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

[0054]

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

[0056] Furthermore, the controller is specifically used to: when the preset operating mode is a load simulation operating 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 medium power voltage balance, and use a given power load control algorithm to generate an inverter side switch signal of the three-level DC / AC converter.

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

[0058] Generate dq-axis components of a modulation voltage based on the output side power of the power grid simulator;

[0059] The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage;

[0060] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

[0061] Furthermore, the dq 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, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, respectively, set and Q set are the set active and reactive values ​​of the simulated load, P and Q are the output side active and reactive power of the power grid simulator, respectively. and They are the d and q component compensation 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.

[0064] Furthermore, the controller is specifically used to: when the preset operating mode is the load simulation operating mode, close the first switch, the second switch and the third 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 medium power voltage balance, and use a follow-up power load control algorithm to generate an inverter side switch signal of the three-level DC / AC converter.

[0065] Further, the method of using a follow-up power load control algorithm to generate an inverter-side switch signal of a three-level DC / AC converter includes:

[0066] Generate dq-axis components of a modulation voltage based on the three-phase current of the load state branch;

[0067] The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage;

[0068] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

[0069] Furthermore, the dq 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, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, i d_cb2 and i q_cb2 They are the d-axis and q-axis components of the current in the load state branch, and They are the d and q component compensation 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.

[0072] In a second aspect, a control method for a power grid simulation device capable of dual-mode operation is provided, wherein the power grid simulation device capable of dual-mode operation comprises:

[0073] The controller controls the on and 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 a preset operation mode of the power grid simulation device.

[0074] In a third aspect, a computer device is provided, comprising: 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 of the power 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, and when the computer program is executed, the control method of the power grid simulation device capable of dual-mode operation is implemented.

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

[0079] The present invention provides a dual-mode operation power grid simulation device and a control method thereof, comprising: a power grid simulator, a first switch, a second switch, a third switch, a load state 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 state branch; the second switch is connected to the load state branch; the controller is used to control the on and 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 realizes the dual-mode operation control of the power grid simulation device, expands the application scope of the power grid simulation device, saves the investment of 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 dual-mode power grid simulation device provided by the present invention, the inverter side of the power grid simulator achieves an increase in the capacity of the device through the cascading of multiple converters, and the capacity of the inverter side can be expanded to hundreds of megawatts; the rectifier side achieves midpoint voltage balance and rapid response to power changes through DC side current feedback and capacitor voltage deviation closed-loop control; on the one hand, the inverter side improves the voltage and power quality and control accuracy through positive and negative sequence voltage sequencing control to achieve power grid simulation, and on the other hand, load simulation is achieved through load power closed-loop control or load current monitoring and feedback control. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0083] Figure 3 It is a schematic diagram of the inverter-side switch signal generation principle of the power grid simulator according to an embodiment of the present invention. DETAILED DESCRIPTION

[0084] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0085] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0086] Example 1

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

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

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

[0090] A connection point between the input side of the power grid simulator and the first switch and a connection point between the output side of the power grid simulator and the third switch are connected to a load state branch;

[0091] The load state branch is connected to a second switch;

[0092] The controller is used to control the on and 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 a preset operating mode of the power grid simulation device.

[0093] In this embodiment, 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;

[0094] The input side of the power 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 windings of the multiple three-winding transformers are cascaded, and the tails of the final three-phase transformers are short-connected together to serve as the output side of the power grid simulator.

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

[0099] In one embodiment, the controller is specifically used to: when the preset operating mode is the power grid simulation operating 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 medium power voltage balance, and use the outer loop to use the positive sequence and negative sequence voltage closed-loop control algorithm to generate the inverter side switch signal of the three-level DC / AC converter.

[0100] In one embodiment, if Figure 2 As shown, the method of generating a rectifier-side switch signal of a three-level AC / DC converter with the goal of stabilizing the DC bus voltage and balancing the medium power voltage includes:

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

[0102] 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;

[0103] The d-axis and q-axis components of the initial modulation voltage are subjected to dq inverse transformation to generate a three-phase modulation voltage;

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

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

[0106] In one embodiment, the positive and negative direct bus currents are fed forward through a low-pass filter, and the DC bus voltage U dc With the set DC voltage U dc *The deviation is superimposed on the output of PI and used as the d-axis current reference value, while 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 first PI regulator transfer function, To set the DC voltage, U dcis the DC bus voltage, G LPF (s) is the low-pass filter transfer function, i p 、i n are the positive and negative DC bus currents respectively.

[0109] In one embodiment, the d-axis and q-axis components i of the AC side current gd 、i gq , respectively with the reference current i gd *、i gq * The difference is generated by the regulator to generate the d-axis and q-axis components of the initial modulation voltage, and the d-axis and q-axis components of the initial modulation voltage are as follows:

[0110]

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

[0112] In one embodiment, to achieve balanced control of the midpoint voltage of capacitors C1 and C2, the voltage U on capacitor C1 is C1 and the voltage U on capacitor C2 C2 The difference is passed through the PI4 regulator and the initial modulation voltage d and q axis components U d *、U q *U generated by dq inverse transformation abc * Add together to form the final modulation voltage U gabc *, the final modulation voltage is as follows:

[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 of 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 of 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, if Figure 3 As shown, the outer loop adopts a positive sequence and negative sequence voltage closed loop control algorithm to generate an inverter side switch signal of a three-level DC / AC converter, including:

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

[0117] Generate current dq-axis positive and negative sequence components based on the capacitor voltage dq-axis positive and negative sequence components;

[0118] Generate dq-axis positive and negative sequence components of the modulation voltage based on the dq-axis positive and negative sequence components of the current;

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

[0120] generating an inverter modulation voltage based on the positive and negative sequence components of the three-phase modulation voltage;

[0121] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

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

[0123]

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

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

[0126]

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

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

[0129]

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

[0131] In one embodiment, the controller is specifically used to: when the preset operating mode is a load simulation operating 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 medium power voltage balance, and use a given power load control algorithm to generate an inverter side switch signal of the three-level DC / AC converter.

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

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

[0134] The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage;

[0135] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter, thereby realizing a given power load simulation.

[0136] In one embodiment, the voltage and current at the output side of the power grid simulation device are collected. Figure 1 The terminal voltage and current of CB3 are used to calculate the total active power P and reactive power Q, which are respectively compared with the set active power value P of the simulated load. set , Q set The difference is sent to the PI regulator, and the PI regulator output 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-axis and q-axis components of the modulation voltage, G9(s) and G 10(s) are the ninth and tenth PI regulator transfer functions, respectively, set and Q set are the set active and reactive values ​​of the simulated load, P and Q are the output side active and reactive power of the power grid simulator, respectively. and They are the d and q component compensation 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 used to: when the preset operating mode is a load simulation operating mode, close the first switch, the second switch and the third 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 medium power voltage balance, and use a follow-up power load control algorithm to generate an inverter side switch signal of the three-level DC / AC converter.

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

[0141] Generate dq-axis components of a modulation voltage based on the three-phase current of the load state branch;

[0142] The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage;

[0143] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

[0144] In one embodiment, the three-phase current i of the load state branch is collected. abc_cb2 , after dq transformation, we get the d and q components of the current i d_cb2 and i q_cb2 , compare the two with 0 respectively, send the deviation to the PI regulator, and superimpose the PI regulator output with the dq component compensation link of the AC output current. At the same time, 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:

[0145]

[0146] In the above formula, and are the d-axis and q-axis components of the modulation voltage, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, i d_cb2 and i q_cb2 They are the d-axis and q-axis components of the current in the load state branch, and They are the d and q component compensation 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.

[0147] The specific control block diagram is as follows Figure 3 When the selector switch K1 is in a, it runs in the grid simulation mode; when K1 is in b and K2 is in 1, it runs in the given power load simulation mode; when K1 is in b and K2 is in 2, it runs in the follow-up power load simulation mode. Figure 3 Middle U mabc and I mabc The three-phase voltage and current of the inverter are measured respectively.

[0148] Example 2

[0149] The present invention provides a control method for a power grid simulation device capable of dual-mode operation, wherein the power grid simulation device capable of dual-mode operation comprises:

[0150] The controller controls the on and 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 a preset operation mode of the power grid simulation device.

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

[0152] Furthermore, when the preset operating mode is the grid simulation operating mode, the first switch and the third switch are closed, and the second switch is opened, and the rectifier side switch signal of the three-level AC / DC converter is generated with the goal of stabilizing the DC bus voltage and the balance of the medium power voltage, and the outer loop adopts the positive-sequence and negative-sequence voltage closed-loop control algorithm to generate the inverter side switch signal of the three-level DC / AC converter.

[0153] Furthermore, the step of generating a rectifier-side switch signal of a three-level AC / DC converter with the goal of stabilizing the DC bus voltage and balancing the medium power voltage includes:

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

[0155] 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;

[0156] The d-axis and q-axis components of the initial modulation voltage are subjected to dq inverse transformation to generate a three-phase modulation voltage;

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

[0158] The final modulation voltage is modulated by PWM to generate the rectifier-side switching signal of the three-level AC / DC converter.

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

[0160]

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

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

[0163]

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

[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 It 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] Further, the outer loop adopts a positive sequence and negative sequence voltage closed loop control algorithm to generate an inverter side switch signal of a three-level DC / AC converter, including:

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

[0170] Generate current dq-axis positive and negative sequence components based on the capacitor voltage dq-axis positive and negative sequence components;

[0171] Generate dq-axis positive and negative sequence components of the modulation voltage based on the dq-axis positive and negative sequence components of the current;

[0172] Inversely transforming the dq axis positive and negative sequence components dq of the modulation voltage to generate positive and negative sequence components of the three-phase modulation voltage;

[0173] generating an inverter modulation voltage based on the positive and negative sequence components of the three-phase modulation voltage;

[0174] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

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

[0176]

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

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

[0179]

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

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

[0182]

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

[0184] Furthermore, when the preset operating mode is the load simulation operating mode, the first switch and the third switch are closed, and the second switch is opened, and the rectifier side switch signal of the three-level AC / DC converter is generated with the goal of stabilizing the DC bus voltage and the balance of the medium power voltage, and the inverter side switch signal of the three-level DC / AC converter is generated using a given power load control algorithm.

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

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

[0187] The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage;

[0188] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

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

[0190]

[0191] In the above formula, and are the d-axis and q-axis components of the modulation voltage, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, respectively, set and Q set are the set active and reactive values ​​of the simulated load, P and Q are the output side active and reactive power of the power grid simulator, respectively. and They are the d and q component compensation 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] Furthermore, when the preset operating mode is the load simulation operating mode, the first switch, the second switch and the third switch are closed, and the rectifier side switch signal of the three-level AC / DC converter is generated with the goal of stabilizing the DC bus voltage and the balance of the medium power voltage, and the inverter side switch signal of the three-level DC / AC converter is generated by using a follow-up power load control algorithm.

[0193] Further, the method of using a follow-up power load control algorithm to generate an inverter-side switch signal of a three-level DC / AC converter includes:

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

[0195] The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage;

[0196] The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

[0197] Furthermore, 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, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, i d_cb2 and i q_cb2 They are the d-axis and q-axis components of the current in the load state branch, and They are the d and q component compensation 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.

[0200] Example 3

[0201] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and 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 other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing 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-mentioned embodiment.

[0202] Example 4

[0203] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It can be understood that the computer-readable storage medium here can include both built-in storage media in a computer device and, of course, extended storage media supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can 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 processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of a control method of a power grid simulation device capable of dual-mode operation in the above embodiment.

[0204] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may 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.) containing computer-usable program code.

[0205] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes 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 a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0206] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0207] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0208] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A power grid simulation device capable of dual-mode operation, characterized in that: The device comprises: a power grid simulator, a first switch, a second switch, a third switch, a load state 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; A connection point between the input side of the power grid simulator and the first switch and a connection point between the output side of the power grid simulator and the third switch are connected to a load state branch; The load state branch is connected to a second switch; The controller is used to control the on and 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 a preset operating mode of the power grid simulation device.

2. The device according to claim 1, characterized in that The power grid simulator comprises: 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 windings of the multiple three-winding transformers are cascaded, and the tails of the final three-phase transformers are short-connected together to serve as the output side of the power grid simulator.

3. The device according to claim 2, characterized in that The preset operation mode includes at least one of the following: a power grid simulation operation mode and a load simulation operation mode.

4. The device according to claim 3, characterized in that The controller is specifically used for: when the preset operation mode is the power grid simulation operation mode, closing the first switch and the third switch, opening the second switch, generating a rectifier-side switch signal of the three-level AC / DC converter with the goal of stabilizing the DC bus voltage and balancing the medium power voltage, and using an outer loop to use a positive-sequence and negative-sequence voltage closed-loop control algorithm to generate an inverter-side switch signal of the three-level DC / AC converter.

5. The device according to claim 4, characterized in that The method of generating a rectifier-side switch signal of a three-level AC / DC converter with the goal of stabilizing the DC bus voltage and balancing the medium power voltage includes: Generate a d-axis current reference value and a q-axis current reference value based on the positive and negative direct bus currents; 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; The d-axis and q-axis components of the initial modulation voltage are subjected to dq inverse transformation to generate a three-phase modulation voltage; generating a final modulation voltage based on the three-phase modulation voltage; The final modulation voltage is modulated by PWM to generate the rectifier-side switching signal of the three-level AC / DC converter.

6. The device according to claim 5, 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 d-axis current reference value and the q-axis current reference value respectively, G1(s) is the first PI regulator transfer function, To set the DC voltage, U dc is the DC bus voltage, G LPF (s) is the low-pass filter transfer function, i p 、i n are the positive and negative DC bus currents respectively.

7. The device according to claim 6, 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, i gd 、i gq are the d-axis and q-axis components of the AC side current, G2(s) and G3(s) are the transfer functions of the second and third PI regulators, respectively. gd , U gq are the d and q components of the input grid voltage, respectively, K d is the decoupling coefficient of the inner loop current on the rectifier side.

8. The device according to claim 7, 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 It 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.

9. The device according to claim 4, characterized in that The method of using an outer loop to generate an inverter-side switch signal of a three-level DC / AC converter using a positive-sequence and negative-sequence voltage closed-loop control algorithm includes: The positive and negative sequence components of the capacitor voltage on the AC side of the three-level DC / AC converter are transformed by dq to obtain the positive and negative sequence components of the capacitor voltage on the dq axis; Generate current dq-axis positive and negative sequence components based on the capacitor voltage dq-axis positive and negative sequence components; Generate dq-axis positive and negative sequence components of the modulation voltage based on the dq-axis positive and negative sequence components of the current; Inversely transforming the dq axis positive and negative sequence components dq of the modulation voltage to generate positive and negative sequence components of the three-phase modulation voltage; generating an inverter modulation voltage based on the positive and negative sequence components of the three-phase modulation voltage; The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

10. The device according to claim 9, characterized in that The positive and negative sequence components of the current dq axis are as follows: In the above formula, and are the positive and negative sequence components of the current dq axis, G5(s) and G6(s) are the transfer functions of the fifth and sixth PI regulators, respectively. and are the given positive and negative sequence components of the dq axis voltage respectively, and They are the positive and negative sequence components of the capacitor voltage dq axis respectively.

11. The device according to claim 10, characterized in that The dq axis positive and negative sequence components of the modulation voltage are as follows: In the above formula, and are the dq axis positive and negative sequence components of the modulation voltage, G7(s) and G8(s) are the seventh and eighth PI regulator transfer functions, respectively. and are the reference values ​​of the positive and negative sequence components of the current dq axis, R v is a given virtual resistor, s is the Laplace operator, L v For a given virtual inductance, and They are the positive and negative sequence components of the dq axis of the AC output current respectively.

12. The device according to claim 11, characterized in that The inverter modulation voltage is as follows: In the above formula, is the inverter modulation voltage, and They are the positive and negative sequence components of the three-phase modulation voltage respectively.

13. The device according to claim 3, characterized in that The controller is specifically used 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 balance of the medium power voltage, and use a given power load control algorithm to generate an inverter-side switch signal of the three-level DC / AC converter.

14. The device according to claim 13, characterized in that The method of using a given power load control algorithm to generate an inverter-side switch signal of a three-level DC / AC converter comprises: Generate dq-axis components of a modulation voltage based on the output side power of the power grid simulator; The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage; The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

15. The device according to claim 14, 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, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, respectively, set and Q set are the set active and reactive values ​​of the simulated load, P and Q are the output side active and reactive power of the power grid simulator, respectively. and They are the d and q component compensation 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.

16. The device according to claim 3, characterized in that The controller is specifically used to: when the preset operation mode is the load simulation operation mode, close the first switch, the second switch and the third 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 balance of the medium power voltage, and use a follow-up power load control algorithm to generate an inverter side switch signal of the three-level DC / AC converter.

17. The device according to claim 16, characterized in that The method of using a follow-up power load control algorithm to generate an inverter-side switch signal of a three-level DC / AC converter includes: Generate dq-axis components of a modulation voltage based on the three-phase current of the load state branch; The dq axis component of the modulation voltage is subjected to dq inverse transformation to obtain an inverter modulation voltage; The inverter modulation voltage is subjected to carrier phase shift modulation to obtain an inverter side switching signal of a three-level DC / AC converter.

18. The device according to claim 17, 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, G9(s) and G 10 (s) are the ninth and tenth PI regulator transfer functions, i d_cb2 and i q_cb2 are the d-axis and q-axis components of the current in the load state branch, and They are the d and q component compensation 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.

19. A control method for a power grid simulation device capable of dual-mode operation based on any one of claims 1 to 18, characterized in that: The method comprises: The controller controls the on and 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 a preset operation mode of the power grid simulation device.

20. A computer device, characterized in that: include: one or more processors; The processor is configured 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 power grid simulation device capable of dual-mode operation as claimed in claim 19 is implemented.

21. 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 power grid simulation device capable of dual-mode operation as claimed in claim 19 is implemented.

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