Steady-state modeling method for ac-dc hybrid power system based on d-q electrical network

Abstract

The application discloses a steady-state modeling method of AC-DC hybrid power system based on D-Q electric network, and full-order models of AC network and converter station of the hybrid power system containing algebraic terms and differential terms in unified dq coordinate system are derived based on the idea of D-Q electric network modeling. Since the Park transformation is based on time-domain instantaneous value transformation instead of phasor transformation based on characteristic quantity, the time-domain characteristics of each state variable are retained when the instantaneous state variables in the three-phase stationary coordinate system are equivalently transformed into the dq coordinate system, so that the modeling method based on the D-Q electric network can not only accurately depict the dynamic process of the network, but also describe the steady-state characteristics of the network, and is used for analyzing the electric transient and full electromagnetic transient of the network. When applied to a calculation scene, three-phase instantaneous quantities are converted into direct current quantities, so that when the transient analysis is performed, the modeling method based on the D-Q electric network can reduce the order of the differential equation set, reduce the consumption of computer resources, and improve the analysis speed.

Description

Technical Field

[0001] This invention belongs to the field of electrical network modeling technology, specifically relating to a steady-state modeling method for AC / DC hybrid power systems based on DQ electrical networks. Background Technology

[0002] Power flow calculation is fundamental to the study of optimized operation and stable control of AC / DC hybrid power systems. Modern AC / DC hybrid power systems contain a large number of power electronic devices, fast control components, and DC devices. The extensive use of these devices has led to a lack of uniformity in the coordinate systems of state variables in different networks and different regions within the same network. When analyzing hybrid systems, traditional quasi-static phasor models, which are based on nodal admittance equations and use sinusoidal characteristics, require converter stations to convert the collected AC network power flow data to the dq coordinate system before calculation. This inconsistency in the coordinate systems of variables with the same attribute, as well as the conversion of state variables between different coordinate systems, increases the complexity of the power flow equations and affects the accuracy of the analysis and the performance of the calculation.

[0003] Meanwhile, the high-frequency equipment and fast switching devices in the system make small disturbances and oscillation problems more prominent. Traditional quasi-static phasor models lack the ability to analyze high-frequency components and transient processes. When performing stability analysis, they cannot establish high-order differential equations to analyze the dynamic process of the system, which makes the calculation method unable to be extended to the dynamic domain and can only analyze steady-state processes, resulting in poor scalability. Summary of the Invention

[0004] The purpose of this invention is to provide a steady-state modeling method for AC / DC hybrid power systems based on DQ power networks, which solves the problem of poor scalability caused by the lack of dynamic analysis in existing steady-state modeling methods.

[0005] The technical solution adopted in this invention is a steady-state modeling method for AC / DC hybrid power systems based on DQ power networks, which is implemented according to the following steps:

[0006] Step 1: For AC networks of AC / DC, establish a steady-state model of the AC network based on the node current relationship and power balance;

[0007] Step 2: For AC / DC network converters, establish a steady-state model of the AC / DC network converter based on the relationship between KCL and KVL;

[0008] Step 3: For the DC network of the AC / DC network, establish a steady-state model of the DC network based on the node current relationship and power balance;

[0009] Step 4: Integrate the steady-state models of the AC network, DC network and converter in the AC / DC network, and establish a steady-state model of the AC / DC hybrid power system based on the DQ power network.

[0010] Step 1 is as follows:

[0011] For a pure AC network, its full-order DQ electrical network model is:

[0012]

[0013]

[0014]

[0015] Where C and G are diagonal matrices of the capacitance and conductance of the AC network node-to-ground branches, R and L are diagonal matrices of the resistance and inductance of the AC network branches, and B... m V is the node-branch correlation matrix of the communication network, where K is the diagonal matrix representing the branch ratios of the communication network; dq F dq Let I be the column vector of the dq-axis components of the AC network bus voltage. dq.g The column vector of the dq-axis components of the sum of the currents injected into the source loads of the AC network bus;

[0016] When a multi-terminal DC network is embedded in an AC network, the AC bus node current relationship and power balance connected to the converter change as follows:

[0017] I dq.in =I dq.g -f dq.vsc (4)

[0018] P in =P g -P vsc (5)

[0019] Where I dq.in The dq-axis component of the current injected into the AC network bus, f dq.vsc P is the injection current from the AC network bus to the connected converter. in To inject active power into the AC network bus, P g P is the sum of the power injected into the source loads of the AC network bus. vsc f represents the active power injected into the connected converter by the AC network. When the AC network is not connected to the DC network, f dq.vsc With P vsc Both are 0. The injected current and injected active power of the source load connected to the bus are the same as the injected current and injected active power of the bus.

[0020] Therefore, considering the power exchange between the AC network bus and the DC network through the converter, the dynamic model of the AC / DC hybrid power system based on the DQ power network should be:

[0021]

[0022] Ignoring the differential terms in equation (6), the matrix expression of the steady-state model of the AC network of the AC-DC hybrid power system based on the DQ power network is as follows:

[0023]

[0024]

[0025] Step 2 is as follows:

[0026] The KVL and KCL equations for AC / DC network converters are as follows:

[0027]

[0028]

[0029] Among them, V s abc f is the three-phase voltage (abc) of the AC network bus s to which the converter is connected. sc abc To inject AC current into the converter's AC bus c, the three-phase currents abc are measured. k abc V is the modulation index of the instantaneous values ​​of the three phases abc corresponding to converter k. idc I is the voltage of the DC bus i of the converter. idc.vsc The current r is injected into the DC-side bus i of the converter. c , l c c c For the RLC parameters of the converter filter branch, c k The capacitor is located on the DC side of the converter.

[0030] By performing Parker transformation on equations (9) and (10), the steady-state model of the AC / DC hybrid power system converter based on the DQ power network is as follows:

[0031]

[0032]

[0033] Among them, f sd.vsc f sq.vsc The dq-axis component of the converter current injected into the AC network bus S;

[0034] The matrix expression of formulas (11) and (12) is the steady-state model of the AC / DC network converter:

[0035]

[0036]

[0037] D d D q V is the diagonal matrix of the dq-axis components of the converter modulation. d V q f d f q R represents the column vectors of the voltage dq-axis components of the AC network bus connected to the converter and the current dq-axis components injected into the converter from the bus, respectively. c L c C c I is a diagonal matrix of the RLC parameters of the converter filter branch. dc.vsc The column vector that injects the DC-side bus current into the converter.

[0038] Step 3 is as follows:

[0039] For a pure DC network, its dynamic model is as follows:

[0040]

[0041] Where C dc G dc R is a diagonal matrix of the capacitance and conductance of the DC network node-to-ground branches. dc L dc B is a diagonal matrix of the branch resistances and inductances of a DC network. dc V is the node-branch correlation matrix of a DC network. dc F ddc I is the DC network bus voltage. dc.g The sum of the currents injected into the source loads of the DC network bus;

[0042] When embedded in an AC network, the current in the DC network bus changes according to the power balance as follows:

[0043] I dc.in =I dc.g +I dc.vsc (16)

[0044] P dc.in =P dc.g +P dc.vsc (17)

[0045] Considering the power exchange between the DC network and the DC network through the converter, the dynamic model of the DC network in the AC / DC hybrid power system based on the DQ power network should be:

[0046]

[0047] Ignoring the differential terms in formula (15), the matrix expression of the steady-state model of the DC network of the AC / DC hybrid power system based on the DQ power network is as follows:

[0048] I dc.in =(L R +G dc V dc (19)

[0049] in:

[0050]

[0051] In the formula: I dc.in P dc.in I represents the total injected current and total injected power of DC bus i. dc.g P dc.g I represents the source-load injected current and source-load injected active power of the DC bus. dc.vsc P dc.vsc This indicates the injected current and active power from the converter station connected to the DC bus to the bus; L R This represents the Laplace matrix of a DC network.

[0052] Step 4 is as follows:

[0053] Assuming the AC / DC hybrid power system includes n AC buses, m DC buses, and r converter stations, and combining the steady-state models of the AC network, converters, and DC network in the AC / DC network, the steady-state model of the AC / DC hybrid power system based on the DQ power network is obtained as follows:

[0054]

[0055]

[0056] In formula (20), Vdc*, Vd*, and Vq* are the reduced-order DC voltage and AC dq-axis voltage phasors, which only include the voltages of the AC / DC system buses connected to the converter, and their orders are r and E. r It is an r-order identity matrix.

[0057] The beneficial effects of this invention are:

[0058] This invention presents a steady-state modeling method for AC / DC hybrid power systems based on DQ electric networks. This method, based on the concept of DQ electric network modeling, derives a full-order model of the AC network and converter station of the hybrid power system, including algebraic and differential terms, in a unified dq coordinate system. Since the Park transformation is based on instantaneous value transformation in the time domain rather than phasor transformation based on characteristic quantities, the DQ electric network-based modeling method preserves the time-domain characteristics of each state variable when equivalently transforming the instantaneous state variables in the three-phase stationary coordinate system to the dq coordinate system. This allows the DQ electric network-based modeling method to accurately characterize the network's dynamic processes and describe its steady-state characteristics, enabling it to be used for electrical transient and all-electromagnetic transient analysis. In computational scenarios, because the state variables in the three-phase stationary coordinate system are directly mapped to the rotating coordinate system, the three-phase instantaneous quantities are converted into DC quantities. Therefore, during transient analysis, the DQ electric network-based modeling method can reduce the order of the differential equation system, decrease the consumption of computer resources, and improve the analysis speed. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the steady-state model of the AC system based on the DQ electrical network of the present invention;

[0060] Figure 2 A schematic diagram of the electrical quantities of the AC busbar in the converter station;

[0061] Figure 3 Model of the AC busbar of the converter station in the dq coordinate system;

[0062] Figure 4 Model of the LC filter branch of the converter station;

[0063] Figure 5 The converter station model is in the dq coordinate system;

[0064] Figure 6 This is a schematic diagram showing the electrical quantities of the DC bus in the converter station.

[0065] Figure 7 The diagram shows the steady-state model of a back-to-back AC / DC hybrid power system based on the DQ power network.

[0066] Figure 8 This is a DC network structure diagram of the EEE39 improved system in an embodiment of the present invention. Detailed Implementation

[0067] The present invention will now be described in detail with reference to the accompanying drawings and an implementation example.

[0068] The present invention provides a steady-state modeling method for AC / DC hybrid power systems based on DQ power networks, which is implemented according to the following steps:

[0069] Step 1: For AC networks with AC / DC interconnects, establish a steady-state model of the AC network based on node current relationships and power balance; analyze the changes in current relationships and power balance of each bus node in an AC system embedded with a multi-terminal DC network, modify the dynamic model of the AC system's DQ power network, and establish a steady-state model of the AC network of a hybrid AC / DC power system based on the DQ power network. The specific process is as follows:

[0070] like Figure 1 As shown, for a pure AC network, its full-order DQ electrical network model is:

[0071]

[0072]

[0073]

[0074] Where C and G are diagonal matrices of the capacitance and conductance of the AC network node-to-ground branches, R and L are diagonal matrices of the resistance and inductance of the AC network branches, and B... m V is the node-branch correlation matrix of the communication network, where K is the diagonal matrix representing the branch ratios of the communication network; dq F dq Let I be the column vector of the dq-axis components of the AC network bus voltage. dq.g The column vector of the dq-axis components of the sum of the currents injected into the source loads of the AC network bus;

[0075] like Figure 2 As shown, when a multi-terminal DC network is embedded in the AC network, the AC bus node current relationship and power balance connected to the converter change as follows:

[0076] I dq.in =I dq.g -f dq.vsc (4)

[0077] P in =P g -P vsc (5)

[0078] Among them I dq.in The dq-axis component of the current injected into the AC network bus, f dq.vsc P is the injection current from the AC network bus to the connected converter. in To inject active power into the AC network bus, P g P is the sum of the power injected into the source loads of the AC network bus. vsc f represents the active power injected into the connected converter by the AC network. When the AC network is not connected to the DC network, f dq.vsc With P vscBoth are 0. The injected current and injected active power of the source load connected to the bus are the same as the injected current and injected active power of the bus.

[0079] Therefore, considering the power exchange between the AC network bus and the DC network through the converter, the dynamic model of the AC / DC hybrid power system based on the DQ power network should be:

[0080]

[0081] Ignoring the differential terms in equation (6), the matrix expression of the steady-state model of the AC network of the AC-DC hybrid power system based on the DQ power network is as follows:

[0082]

[0083]

[0084] The AC bus model of the converter station in the dq coordinate system is as follows Figure 3 As shown.

[0085] Step 2: For the AC / DC network converter, establish a steady-state model of the AC / DC network converter based on the relationship between KCL and KVL; write KVL and KCl equations based on the three-phase instantaneous state variables for the converter part, and map the instantaneous state variables from the abc three-phase coordinate system to the dq0 coordinate system to establish a steady-state model of the AC / DC hybrid power system converter based on the DQ power network.

[0086] The specific process of establishing a steady-state model of an AC / DC hybrid power system converter based on a DQ power network is as follows:

[0087] For example Figure 4 As shown, the KVL and KCL equations for the converter station are written as follows:

[0088]

[0089]

[0090] Among them, V s abc f is the three-phase voltage (abc) of the AC network bus s connected to the converter. sc abc To inject AC current into the converter's AC bus c, the three-phase currents abc are measured. k abc V is the modulation index of the instantaneous values ​​of the three phases abc corresponding to converter k. idc I is the voltage of the DC bus i of the converter. idc.vsc The current r is injected into the DC-side bus i of the converter. c , l c c cFor the RLC parameters of the converter filter branch, c k The capacitor is for the DC current of the converter;

[0091] Branch current f sc The current f injected into the converter by the AC network bus s s.vsc The relationship between them is:

[0092]

[0093] Substituting formula (11-1) into formula (9) yields:

[0094]

[0095] Based on coordinate transformation:

[0096] V s abc =P -1 V s dq0 (11-3)

[0097] f s abc =P -1 f s dq0 (11-4)

[0098]

[0099] Among them, P -1 To obtain the inverse matrix of the Parker transformation, substituting equations (11-3)-(11-5) into equation (11-2) and expanding the differential term by term, we get:

[0100]

[0101] Multiply both sides of the formula by the Parker transformation matrix P:

[0102]

[0103] in:

[0104]

[0105]

[0106] Therefore, the final form of formula (8) in the dq coordinate system is as follows:

[0107]

[0108] Ignoring the differential components of the state variables in formula (11-10), we can obtain the steady-state equation:

[0109]

[0110] Similarly, substituting formulas (11-4) and (11-5) into formula (10) yields:

[0111]

[0112] in:

[0113]

[0114] Substituting equations (11-1) and (12-2) into equation (12-1) and ignoring the differential term, we obtain the final form of equation (10) in the dq coordinate system as follows:

[0115]

[0116] Among them, f sd.vsc f sq.vsc The dq-axis component of the converter current injected into the AC network bus S;

[0117] The matrix expression of formulas (11) and (12) is the steady-state model of the AC / DC network converter:

[0118]

[0119]

[0120] D d D q V is the diagonal matrix of the dq-axis components of the converter modulation. d V q f d f q R represents the column vectors of the voltage dq-axis components of the AC network bus connected to the converter and the current dq-axis components injected into the converter from the bus, respectively. c L c C c I is a diagonal matrix of the RLC parameters of the converter filter branch. dc.vsc The column vector that injects the DC-side bus current into the converter.

[0121] Converter station model in dq coordinate system as follows Figure 5 As shown.

[0122] Step 3: For the DC network within the AC / DC network, establish a steady-state model of the DC network based on the node current relationships and power balance; analyze the multi-terminal DC network embedded in the AC network, the changes in the injected current relationships and power balance of each DC bus, modify its network dynamic model, and establish a steady-state model of the DC network of the AC / DC hybrid power system based on the DQ power network. The specific process is as follows:

[0123] For a pure DC network, its dynamic model is as follows:

[0124]

[0125] Where C dc G dc R is a diagonal matrix of the capacitance and conductance of the DC network node-to-ground branches. dc L dc B is a diagonal matrix of the branch resistances and inductances of a DC network. dc V is the node-branch correlation matrix of a DC network. dc F ddc I is the DC network bus voltage. dc.g The sum of the currents injected into the source loads of the DC network bus;

[0126] like Figure 6 The electrical quantities of the DC bus in the converter station are shown below: After being integrated into the AC network, the current relationship of the DC network bus changes with the power balance as follows:

[0127] I dc.in =I dc.g +I dc.vsc (16)

[0128] P dc.in =P dc.g +P dc.vsc (17)

[0129] Considering the power exchange between the DC network and the DC network through the converter, the dynamic model of the DC network in the AC / DC hybrid power system based on the DQ power network should be:

[0130]

[0131] Ignoring the differential terms in formula (15), the matrix expression of the steady-state model of the DC network of the AC / DC hybrid power system based on the DQ power network is as follows:

[0132] I dc.in =(L R +G dc V dc (19)

[0133] in:

[0134]

[0135] In the formula: I dc.in P dc.in I represents the total injected current and total injected power of DC bus i. dc.g P dc.gI represents the source-load injected current and source-load injected active power of the DC bus. dc.vsc P dc.vsc This indicates the injected current and active power from the converter station connected to the DC bus to the bus; L R This represents the Laplace matrix of a DC network.

[0136] Step 4: Integrate the steady-state models of the AC network, DC network, and converter in the AC / DC network to establish a steady-state model of the AC / DC hybrid power system based on the DQ power network. The specific process is as follows:

[0137] Assuming the AC / DC hybrid power system includes n AC buses, m DC buses, and r converter stations, and combining the steady-state models of the AC network, converters, and DC network in the AC / DC network, the steady-state model of the AC / DC hybrid power system based on the DQ power network is obtained as follows:

[0138]

[0139]

[0140] In formula (20), Vdc*, Vd*, and Vq* are the reduced-order DC voltage and AC dq-axis voltage phasors, which only include the voltages of the AC / DC system buses connected to the converter, and their orders are r and E. r It is an r-order identity matrix.

[0141] Steady-state model of back-to-back AC / DC hybrid power system based on DQ power network as follows: Figure 7 As shown.

[0142] The above is the complete derivation process of a steady-state modeling method for AC / DC hybrid power systems based on DQ electric networks. Since the Park transformation is based on the instantaneous value transformation in the time domain rather than the phasor transformation of characteristic quantities, the modeling method based on DQ electric networks retains the time-domain characteristics of each state variable when transforming the instantaneous state variables in the three-phase stationary coordinate system to the dq coordinate system. This allows the modeling method based on DQ electric networks to accurately characterize the dynamic process of the network and describe its steady-state characteristics.

[0143] Meanwhile, since the steady-state model of the AC / DC hybrid power system based on the DQ power network is derived from the dynamic models of the AC network, DC network and converter station, the dynamic model of the AC network is shown in formula (6), the dynamic model of the converter station is shown in formulas (11-10) and (12-1), and the dynamic model of the DC network is shown in formula (15), the model can be extended to the analysis of the dynamic domain.

[0144] The modeling method of this invention is used for electrical transient and all-electromagnetic transient analysis of networks. When applied to computational scenarios, the modeling method based on DQ electric networks directly maps the state variables in the three-phase stationary coordinate system to the rotating coordinate system, thereby converting the three-phase instantaneous quantities into DC quantities. Therefore, when performing transient analysis, the modeling method based on DQ electric networks can reduce the order of the differential equation system, reduce the consumption of computer resources, and improve the speed of analysis.

[0145] Example

[0146] A steady-state model of an AC / DC hybrid power system based on a DQ power network is applied to power flow calculations during steady-state processes. A 5VSC-MTDC system based on an improved IEEE 39 system is used as an example. The DC network structure and converter layout are as follows: Figure 8 As shown in Table 1, the control parameters converged after 5 iterations, with ε = 10. -6 The comparison between the calculated results and the simulation data is shown in Table 2. The highest voltage error at each node does not exceed 2.26e-4p.u., and the lowest is only 3.4e-6p.u. This result demonstrates the accuracy and effectiveness of the model in terms of computational performance.

[0147] Table 1

[0148]

[0149] Table 2

[0150]

[0151]

[0152] This invention presents a steady-state modeling method for AC / DC hybrid power systems based on DQ electric networks. This method, based on the concept of DQ electric network modeling, derives a full-order model of the AC network and converter station of the hybrid power system, including algebraic and differential terms, in a unified dq coordinate system. Since the Park transformation is based on instantaneous value transformation in the time domain rather than phasor transformation based on characteristic quantities, the DQ electric network-based modeling method preserves the time-domain characteristics of each state variable when equivalently transforming the instantaneous state variables in the three-phase stationary coordinate system to the dq coordinate system. This allows the DQ electric network-based modeling method to accurately characterize the network's dynamic processes and describe its steady-state characteristics, enabling it to be used for electrical transient and all-electromagnetic transient analysis. In computational scenarios, because the state variables in the three-phase stationary coordinate system are directly mapped to the rotating coordinate system, the three-phase instantaneous quantities are converted into DC quantities. Therefore, during transient analysis, the DQ electric network-based modeling method can reduce the order of the differential equation system, decrease the consumption of computer resources, and improve the analysis speed.

Claims

1. A steady-state modeling method for AC / DC hybrid power systems based on DQ electric networks, characterized in that, The specific steps are as follows: Step 1: For AC networks of AC / DC, establish a steady-state model of the AC network based on the node current relationship and power balance; Step 2: For AC / DC network converters, establish a steady-state model of the AC / DC network converter based on the relationship between KCL and KVL; Step 3: For the DC network of the AC / DC network, establish a steady-state model of the DC network based on the node current relationship and power balance; Steady-state model of AC / DC network converter: (13) (14) D d D q V is the diagonal matrix of the dq-axis components of the converter modulation. d V q f d f q R represents the column vectors of the voltage dq-axis components of the AC network bus connected to the converter and the current dq-axis components injected into the converter from the bus, respectively. c L c C c I is a diagonal matrix of the RLC parameters of the converter filter branch. dc.vsc The column vector into which the DC-side bus current is injected into the converter; Step 4: Integrate the steady-state models of the AC network, DC network, and converter in the AC / DC network to establish a steady-state model of the AC / DC hybrid power system based on the DQ power network; Step 4 is as follows: Assuming the AC / DC hybrid power system includes n AC buses, m DC buses, and r converter stations, and combining the steady-state models of the AC network, converters, and DC network in the AC / DC network, the steady-state model of the AC / DC hybrid power system based on the DQ power network is obtained as follows: (21) (22) In the formula, Vdc Vd Vq The DC voltage and AC dq-axis voltage phasors are reduced-order, containing only the voltages of the AC / DC system buses connected to the converter, with order r and E. r Let I be an r-order identity matrix; C and G are diagonal matrices representing the capacitance and conductance of the AC network node-to-ground branches, respectively. dq.in The dq-axis component of the current injected into the AC network bus, I dc.vsc L represents the injected current from the converter station connected to the DC bus to the bus. R I represents the Laplace matrix of a DC network. dc.in G represents the total injected current into the DC bus. dc Let V be a diagonal matrix of conductance. dc This is the DC network bus voltage.

2. The steady-state modeling method for AC / DC hybrid power systems based on DQ power networks according to claim 1, characterized in that, Step 1 is as follows: For a pure AC network, its full-order DQ electrical network model is: (1) (2) (3) Where C and G are diagonal matrices of the capacitance and conductance of the AC network node-to-ground branches, R and L are diagonal matrices of the resistance and inductance of the AC network branches, and B... m V is the node-branch correlation matrix of the communication network, where K is the diagonal matrix representing the branch ratios of the communication network; dq F dq Let I be the column vector of the dq-axis components of the AC network bus voltage. dq.g The column vector of the dq-axis components of the sum of the currents injected into the source loads of the AC network bus; When a multi-terminal DC network is embedded in an AC network, the AC bus node current relationship and power balance connected to the converter change as follows: (4) (5) Among them I dq.in The dq-axis component of the current injected into the AC network bus, f dq.vsc P is the injection current from the AC network bus to the connected converter. in To inject active power into the AC network bus, P g P is the sum of the power injected into the source loads of the AC network bus. vsc f represents the active power injected into the connected converter by the AC network. When the AC network is not connected to the DC network, f dq.vsc With P vsc Both are 0. The injected current and injected active power of the source load connected to the bus are the same as the injected current and injected active power of the bus. Therefore, considering the power exchange between the AC network bus and the DC network through the converter, the dynamic model of the AC / DC hybrid power system based on the DQ power network should be: (6) Ignoring the differential terms in equation (6), the matrix expression of the steady-state model of the AC network of the AC-DC hybrid power system based on the DQ power network is as follows: (7) (8)。 3. The steady-state modeling method for AC / DC hybrid power systems based on DQ power networks according to claim 1, characterized in that, Step 2 is as follows: The KVL and KCL equations for AC / DC network converters are as follows: (9) (10) Among them, V s abc f is the three-phase voltage (abc) of the AC network bus s to which the converter is connected. sc abc To inject AC current into the converter's AC bus c, the three-phase currents abc are measured. k abc V is the modulation index of the instantaneous values ​​of the three phases abc corresponding to converter k. idc I is the voltage of the DC bus i of the converter. idc.vsc The current r is injected into the DC-side bus i of the converter. c , l c c c For the RLC parameters of the converter filter branch, c k The capacitor is for the DC current of the converter; By performing Parker transformation on equations (9) and (10), the steady-state model of the AC / DC hybrid power system converter based on the DQ power network is as follows: (11) (12) in, f sd.vsc , f sq.vsc The dq-axis component of the converter current injected into the AC network bus S; The matrix expression of formulas (11) and (12) is the steady-state model of the AC / DC network converter.

4. The steady-state modeling method for AC / DC hybrid power systems based on DQ power networks according to claim 1, characterized in that, Step 3 is as follows: For a pure DC network, its dynamic model is as follows: (15) Where C dc G dc R is a diagonal matrix of the capacitance and conductance of the DC network node-to-ground branches. dc L dc B is a diagonal matrix of the branch resistances and inductances of a DC network. dc V is the node-branch correlation matrix of a DC network. dc F dc I is the DC network bus voltage. dc.g The sum of the currents injected into the source loads of the DC network bus; When embedded in an AC network, the current in the DC network bus changes according to the power balance as follows: (16) (17) Considering the power exchange between the DC network and the DC network through the converter, the dynamic model of the DC network in the AC / DC hybrid power system based on the DQ power network should be: (18) Ignoring the differential terms in formula (15), the matrix expression of the steady-state model of the DC network of the AC / DC hybrid power system based on the DQ power network is as follows: (19) in: (20) In the formula: I dc.in P dc.in I represents the total injected current and total injected power of the DC bus. dc.g P dc.g I represents the source-load injected current and source-load injected active power of the DC bus. dc.vsc P dc.vsc This indicates the injected current and active power from the converter station connected to the DC bus to the bus; L R This represents the Laplace matrix of a DC network.

Images