CONVERTER PARAMETERIZED CONSTANT ADMITTANCE MODELING METHOD BASED ON CROSS INITIALIZATION

Abstract

A converter parameterized constant admittance modeling method based on a cross initialization including the following steps: (1) performing parameterized modeling on a converter, wherein switches are modeled using a parametric historical current source constant admittance model and other components are modeled using a traditional electromagnetic transient simulation integral model in the converter; (2) detecting whether state switching occurs, performing cross initialization correction when occurring; (3) determining model parameters, and establishing an equivalent admittance matrix and an injection current source of a whole grid, to obtain an electromagnetic transient simulation equivalent model; (4) solving a network tide according to a basic solving equation I=YU to obtain an electromagnetic transient model simulation result of the converter at current time; and (5) calculating an equivalent admittance matrix and an injection current source at next time through a current network state quantity, and returning to step (2) until a simulation terminates.

Claims

1. A converter parameterized constant admittance modeling method based on a cross initialization, comprising the following steps: (1) performing an electromagnetic transient simulation modeling on a power electronic converter, wherein switches are modeled using a parametric historical current source constant admittance model and other components are modeled using a traditional electromagnetic transient simulation integral model in the power electronic converter, and giving an initial value and a step size of a system; (2) detecting whether an operating state switching occurs, performing a cross initialization correction if the operating state switching occurs, or skipping processing if the operating state switching does not occur; (3) calculating model parameters according to a network topology and an expected control effect, and establishing an equivalent electromagnetic admittance matrix and a historical current source of a whole grid, to obtain an electromagnetic transient simulation equivalent model of the power electronic converter; (4) solving, according to an electromagnetic transient basic solving equation I=YU, an equation established by the electromagnetic transient simulation equivalent model, to obtain an electromagnetic transient model simulation result of the power electronic converter at a current time; and (5) updating an electromagnetic transient simulation equivalent admittance matrix and the historical current source based on a current state quantity of each node in a network for solving at next time, and returning to step (2) until a simulation termination time arrives.

2. The converter parameterized constant admittance modeling method based on cross initialization according to claim 1, wherein in step (1), the electromagnetic transient simulation modeling of the power electronic converter comprises power electronic switches, inductors, capacitors and a control portion, and a specific relationship of the electromagnetic transient simulation modeling is as follows: a DC side voltage U.sub.dc is provided by an external DC voltage source, and a DC side output current I.sub.dc and an output power P.sub.dc passthrough DC side parallel capacitors and then are introduced into several groups of bridge arms composed of upper and lower switches and transmitted to an AC power grid U.sub.ac; the AC power grid feeds an active power P.sub.grid and a reactive power Q.sub.grid back to an outer loop controller, the outer loop controller outputs current reference values idref and iqref to an inner loop controller, and the inner loop controller compares AC side dq axis current components id and iq with the current reference values to generate an SPWM control signal of the power electronic converter.

3. The converter parameterized constant admittance modeling method based on cross initialization according to claim 1, wherein in step (2), the cross initialization correction is specifically as follows: at a time when an operating state of the power electronic converter is switched, an injection current source for a motion switch is calculated using historical state quantities of a voltage and a current of another switch on a corresponding bridge arm to reduce an error offset of the initial value at a switching time; the operating state of the power electronic converter is assumed to switch from S.sub.1 off and S.sub.2 on to S.sub.1 on and S.sub.2 off, and initial values of the cross initialization are obtained: $\{\begin{array}{c}{u}_{\mathrm{up}}^{\prime }\left(t-\Delta t\right)=u_{down}\left(t-\Delta t\right)\\ u_{down}^{\prime }\left(t-\Delta t\right)=u_{up}\left(t-\Delta t\right)\\ i_{\mathrm{up}}^{\prime }\left(t-\Delta t\right)=-i_{down}\left(t-\Delta t\right)\\ i_{down}^{\prime }\left(t-\Delta t\right)=-i_{up}\left(t-\Delta t\right)\end{array};$ injection current sources I.sub.inj,up(t), I.sub.inj,down(t) at a time of the operating state switching are solved using initial values of the historical state quantities.

4. The converter parameterized constant admittance modeling method based on cross initialization according to claim 1, wherein in step (3), establishing the electromagnetic transient simulation equivalent model of the power electronic converter is specifically: a given power electronic switch is expressed by the following equation: $\{\begin{array}{c}i\left(t\right)=G_{eq}u\left(t\right)+I_{\mathrm{inj}}\left(t\right)\\ I_{\mathrm{inj}}\left(t\right)=\alpha G_{eq}u\left(t-\Delta t\right)+\beta i\left(t-\Delta t\right)\end{array};$ wherein, α and β are respectively a voltage coefficient and a current coefficient of an equivalent injection current source; for components such as inductors and capacitors, an equivalent admittance and the historical current source are solved using a backward Euler method: $\{\begin{array}{c}{i}_L\left(t\right)=\frac{\Delta t}{L}{u}_L\left(t\right)+i_L\left(t-\Delta t\right)=G_{eq}{u}_L\left(t\right)+I_{\mathrm{inj},L}\left(t\right)\\ i_C\left(t\right)=\frac{C}{\Delta t}{u}_C\left(t\right)-\frac{C}{\Delta t}{u}_C\left(t-\Delta t\right)=G_{eq}{u}_C\left(t\right)+I_{\mathrm{inj},C}\left(t\right)\end{array};$ the above equations are algebraic equations including comprising unknown state quantities voltage u(t) and current i(t) and a known state quantities voltage u(t−Δt) at a previous time and current i(t−Δt) at the previous time, the above equations are simplified to obtain i=G.sub.eq*u+I.sub.inj, then the electromagnetic transient simulation equivalent admittance matrix G.sub.eq and the equivalent injection current source I.sub.inj is obtained, and an algebraic equation set is solved according to I=YU.

5. The converter parameterized constant admittance modeling method based on cross initialization according to claim 1, wherein the step of establishing the electromagnetic transient simulation modeling according to the network topology and the expected control effect is as follows: (41) establishing a parametric constant admittance model of the power electronic converter: $\{\begin{array}{c}{i}_{\mathrm{up}}\left(t\right)=G_{\mathrm{eq}1}{u}_{\mathrm{up}}\left(t\right)+I_{\mathrm{inj},\mathrm{up}}\left(t\right)=G_{\mathrm{eq}1}{u}_{\mathrm{up}}\left(t\right)+{\alpha }_{\mathrm{up}}{G}_{\mathrm{eq}1}{u}_{\mathrm{up}}\left(t-\Delta t\right)+\\ {\beta }_{\mathrm{up}}{i}_{\mathrm{up}}\left(t-\Delta t\right)\\ i_{\mathrm{down}}\left(t\right)=G_{\mathrm{eq}2}{u}_{\mathrm{down}}\left(t\right)+I_{\mathrm{inj},\mathrm{down}}\left(t\right)=G_{\mathrm{eq}2}{u}_{\mathrm{down}}\left(t\right)+\\ {\alpha }_{\mathrm{down}}{G}_{\mathrm{eq}2}{u}_{\mathrm{down}}\left(t-\Delta t\right)+{\beta }_{\mathrm{down}}{i}_{\mathrm{down}}\left(t-\Delta t\right)\\ i_L\left(t\right)=G_L{u}_L\left(t\right)+I_{\mathrm{inj},L}\left(t\right)=G_L{u}_L\left(t\right)+i_L\left(t-\Delta t\right)\end{array},$ (42) performing a complex frequency domain steady-state operation analysis on a switch model to obtain a switch model parameter expression as: $\{\begin{array}{cc}{i}_{on}\left(t\right)=G_{eq}{u}_{on}\left(t\right)+{\alpha }_{on}{G}_{eq}{u}_{on}\left(t-\Delta t\right)+i_{on}\left(t-\Delta t\right),& S=1\\ i_{\mathrm{off}}\left(t\right)=G_{eq}{u}_{\mathrm{off}}\left(t\right)-G_{eq}{u}_{\mathrm{off}}\left(t-\Delta t\right)+{\beta }_{\mathrm{off}}{i}_{\mathrm{off}}\left(t-\Delta t\right),& S=0\end{array};$ (43) solving a matrix equation about a midpoint voltage of converter bridge arms and the switches in an off state according to the network topology, taking a turn-on upper bridge arm switch and a turn-off lower bridge arm switch as an example: $\left[\begin{array}{c}{u}_{\mathrm{mid},n}\\ \frac{i_{\mathrm{down},n}}{G_2}\end{array}\right]=\left[\begin{array}{cc}{k}_{\mathrm{down}}-{\alpha }_{\mathrm{up}}{k}_{\mathrm{up}}& \left(1-{\beta }_{\mathrm{down}}\right)k_{\mathrm{down}}\\ k_{\mathrm{down}}-1-{\alpha }_{\mathrm{up}}{k}_{\mathrm{up}}& (k_{\mathrm{down}}-{\beta }_{\mathrm{down}}{k}_{\mathrm{down}}+{\beta }_{\mathrm{down}}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{mid},n-1}\\ \frac{i_{\mathrm{down},n-1}}{G_2}\end{array}\right]+\left[\begin{array}{c}\left(1-k_{\mathrm{up}}-k_{\mathrm{down}}\right)u_{\mathrm{pv}}\\ \left(1-k_{\mathrm{up}}-k_{\mathrm{down}}\right)u_{\mathrm{pv}}\end{array}\right]=A\left[\begin{array}{c}{u}_{\mathrm{mid},n-1}\\ \frac{i_{\mathrm{down},n-1}}{G_2}\end{array}\right]+B,\mathrm{where}{k}_1=\frac{G_{\mathrm{eq}1}}{G_{\mathrm{eq}1}+G_{\mathrm{eq}2}+G_L},k_2=\frac{G_{\mathrm{eq}2}}{G_{\mathrm{eq}1}+G_{\mathrm{eq}2}+G_L}$ (44) analyzing transient operating characteristics of a parameterized model to obtain corresponding parameters of the parameterized model in two different operating states as follows: $\mathrm{when}\{\begin{array}{c}{S}_{\mathrm{up}}=1\\ S_{\mathrm{down}}=0\end{array};$ $\{\begin{array}{c}{i}_{\mathrm{up}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t\right)+\frac{k_{\mathrm{down}}+\sqrt{k_{\mathrm{down}}}}{k_{\mathrm{up}}}{G}_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t-\Delta t\right)+i_{\mathrm{up}}\left(t-\Delta t\right)\\ i_{\mathrm{down}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t\right)-G_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t-\Delta t\right)+\frac{\sqrt{k_{\mathrm{down}}}}{\sqrt{k_{\mathrm{down}}+1}}{i}_{\mathrm{down}}\left(t-\Delta t\right)\end{array};$ $\mathrm{when}\{\begin{array}{c}{S}_{\mathrm{up}}=0\\ S_{\mathrm{down}}=1\end{array};$ $\{\begin{array}{c}{i}_{\mathrm{up}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t\right)-G_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t-\Delta t\right)+\frac{\sqrt{k_{\mathrm{up}}}}{\sqrt{k_{\mathrm{up}}+1}}{i}_{\mathrm{up}}\left(t-\Delta t\right)\\ i_{\mathrm{down}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t\right)+\frac{k_{\mathrm{up}}+\sqrt{k_{\mathrm{up}}}}{k_{\mathrm{down}}}{G}_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t-\Delta t\right)+i_{\mathrm{down}}\left(t-\Delta t\right)\end{array};$ (45) establishing models for a control link, a grid-side interface, of a electromagnetic transient simulation system of the power electronic converter, combining the electromagnetic transient basic solving equation I=YU of the electromagnetic transient simulation system of the whole grid; and (46) solving an electromagnetic transient simulation equation of the power electronic converter in combination with interface parameters, to obtain the current state quantity of the each node for updating the electromagnetic transient simulation equivalent admittance matrix and the historical current source, and returning to step (43) to continue a calculation until the simulation termination time arrives.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] FIG. 1 is a schematic flow diagram of a method according to the present invention.

[0034] FIG. 2 is a schematic diagram of a converter electromagnetic transient simulation model according to the present invention.

[0035] FIG. 3 is a schematic diagram of the cross initialization principle according to the present invention.

[0036] FIG. 4 is a comparison diagram of simulated A-phase upper arm switching voltage waveforms of a Ron/Roff model, a LC model and the model of the present invention.

[0037] FIG. 5 is a comparison diagram of simulated A-phase upper arm switching power loss waveforms of a Ron/Roff model, a LC model and the model of the present invention.

[0038] FIG. 6 is a comparison diagram of simulated A-phase output active power of a Ron/Roff model, a LC model and the model of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The technical solution of the invention will be described in detail below in conjunction with the accompanying drawings. The present invention establishes an electromagnetic transient model of a converter by using a parameterization method, analyzes operating characteristics of the model to determine optimal parameters, processes state switching errors by using a cross initialization method, and builds a constant admittance electromagnetic transient simulation parameterization model of the converter, thereby proposing a novel converter parameterized constant admittance modeling method based on cross initialization.

[0040] A converter parameterized constant admittance modeling method based on cross initialization disclosed in the present invention is shown in FIG. 1, including the following steps:

[0041] Step (1) electromagnetic transient simulation modeling is performed on a power electronic converter in which switches are modeled using a parametric historical current source constant admittance model and other components are modeled using a traditional electromagnetic transient simulation integral model, and an initial value and a step size of the system are given;

[0042] Step (2) whether operating state switching occurs is detected, cross initialization correction is performed if state switching occurs, or any processing is not performed if state switching does not occur;

[0043] Step (3) model parameters are calculated according to the network topology and expected control effect, and an equivalent electromagnetic admittance matrix and a historical current source of a whole grid are established, to obtain an electromagnetic transient simulation equivalent model of the converter;

[0044] Step (4) an equation established by the electromagnetic transient simulation equivalent model is solved according to an electromagnetic transient basic solving equation I=YU, to obtain an electromagnetic transient model simulation result of the converter at current time;

[0045] Step (5) the electromagnetic transient simulation equivalent admittance matrix and the historical current source are updated based on the current state quantity of each node in the network for solving at next time, and step (2) is returned until a simulation termination time arrives.

[0046] Step (11), the relationship between internal links of the electromagnetic transient simulation model of the converter is as follows:

[0047] DC side voltage U.sub.dc is provided by an external DC voltage source, and DC side output current lac and output power P.sub.dc pass through DC side parallel capacitors and then are introduced into several groups of bridge arms composed of upper and lower switches and transmitted to an AC power grid U.sub.ac; the power grid feeds active power P.sub.grid and reactive power Q.sub.grid back to an outer loop controller, the outer loop controller outputs current reference values idref and iqref to an inner loop controller, and the inner loop controller compares AC side dq axis current components id and iq with the reference values to generate an SPWM control signal of the converter.

[0048] Step (21), the cross initialization correction method is specifically as follows:

[0049] At the time when the operating state of the converter is switched, an injection current source for a motion switch is calculated using the historical state quantities of the voltage and current of another switch on the corresponding bridge arm, which can greatly reduce the error offset of the initial value at the switching time; the operating state of the converter is assumed to switch from S.sub.1 off and S.sub.2 on to S.sub.1 on and S.sub.2 off, and the initial values of cross initialization are obtained:

[00008]$\{\begin{array}{c}{u}_{\mathrm{up}}^{\prime }\left(t-\Delta t\right)=u_{down}\left(t-\Delta t\right)\\ u_{down}^{\prime }\left(t-\Delta t\right)=u_{up}\left(t-\Delta t\right)\\ i_{\mathrm{up}}^{\prime }\left(t-\Delta t\right)=-i_{down}\left(t-\Delta t\right)\\ i_{down}^{\prime }\left(t-\Delta t\right)=-i_{up}\left(t-\Delta t\right)\end{array}$

[0050] The injection current sources I.sub.inj,up(t), I.sub.inj,down(t) at the time of state switching are solved using the initial values of the state quantities.

[0051] Step (31), establishing an electromagnetic transient simulation equivalent model of the converter is specifically as follows:

[0052] A given power electronic switch is expressed by the following equation:

[00009]$\{\begin{array}{c}i\left(t\right)=G_{eq}u\left(t\right)+I_{\mathrm{inj}}\left(t\right)\\ I_{\mathrm{inj}}\left(t\right)=\alpha G_{eq}u\left(t-\Delta t\right)+\beta i\left(t-\Delta t\right)\end{array}$

[0053] Where, α and β are respectively a voltage coefficient and a current coefficient of an equivalent injection current source.

[0054] For components such as inductors and capacitors, an equivalent admittance and a historical current source are solved using a backward Euler method:

[00010]$\{\begin{array}{c}{i}_L\left(t\right)=\frac{\Delta t}{L}{u}_L\left(t\right)+i_L\left(t-\Delta t\right)=G_{eq}{u}_L\left(t\right)+I_{\mathrm{inj},L}\left(t\right)\\ i_C\left(t\right)=\frac{C}{\Delta t}{u}_C\left(t\right)-\frac{C}{\Delta t}{u}_C\left(t-\Delta t\right)=G_{eq}{u}_C\left(t\right)+I_{\mathrm{inj},C}\left(t\right)\end{array}$

[0055] The above equations are algebraic equations including unknown state quantities voltage u(t) and current i(t) and known state quantities voltage u(t−Δt) at the previous time and current i(t−Δt) at the previous time, the equations are simplified to obtain i=G.sub.eq*u+I.sub.inj, then an electromagnetic transient simulation equivalent admittance matrix G.sub.eq and an equivalent injection current source I.sub.inj can be obtained, and the algebraic equation set is solved according to I=YU.

[0056] The specific process of establishing an electromagnetic transient simulation model according to the network topology and expected control effect is:

[0057] Step (41), a parametric constant admittance model of the converter is established:

[00011]$\{\begin{array}{c}{i}_{\mathrm{up}}\left(t\right)=G_{\mathrm{eq}1}{u}_{\mathrm{up}}\left(t\right)+I_{\mathrm{inj},\mathrm{up}}\left(t\right)=G_{\mathrm{eq}1}{u}_{\mathrm{up}}\left(t\right)+{\alpha }_{\mathrm{up}}{G}_{\mathrm{eq}1}{u}_{\mathrm{up}}\left(t-\Delta t\right)+\\ {\beta }_{\mathrm{up}}{i}_{\mathrm{up}}\left(t-\Delta t\right)\\ i_{\mathrm{down}}\left(t\right)=G_{\mathrm{eq}2}{u}_{\mathrm{down}}\left(t\right)+I_{\mathrm{inj},\mathrm{down}}\left(t\right)=G_{\mathrm{eq}2}{u}_{\mathrm{down}}\left(t\right)+\\ {\alpha }_{\mathrm{down}}{G}_{\mathrm{eq}2}{u}_{\mathrm{down}}\left(t-\Delta t\right)+{\beta }_{\mathrm{down}}{i}_{\mathrm{down}}\left(t-\Delta t\right)\\ i_L\left(t\right)=G_L{u}_L\left(t\right)+I_{\mathrm{inj},L}\left(t\right)=G_L{u}_L\left(t\right)+i_L\left(t-\Delta t\right)\end{array}$

[0058] Step (42), complex frequency domain steady-state operation analysis is performed on the switch model, to obtain a switch model parameter expression as:

[00012]$\{\begin{array}{cc}{i}_{on}\left(t\right)=G_{eq}{u}_{on}\left(t\right)+{\alpha }_{on}{G}_{eq}{u}_{on}\left(t-\Delta t\right)+i_{on}\left(t-\Delta t\right),& S=1\\ i_{\mathrm{off}}\left(t\right)=G_{eq}{u}_{\mathrm{off}}\left(t\right)-G_{eq}{u}_{\mathrm{off}}\left(t-\Delta t\right)+{\beta }_{\mathrm{off}}{i}_{\mathrm{off}}\left(t-\Delta t\right),& S=0\end{array};$

[0059] Step (43), a matrix equation about a midpoint voltage of the converter bridge arms and the switches in the off state is solved according to the network topology, taking a turn-on upper bridge arm switch and a turn-off lower bridge arm switch as an example:

[00013]$\left[\begin{array}{c}{u}_{\mathrm{mid},n}\\ \frac{i_{\mathrm{down},n}}{G_2}\end{array}\right]=\left[\begin{array}{cc}{k}_{\mathrm{down}}-{\alpha }_{\mathrm{up}}{k}_{\mathrm{up}}& \left(1-{\beta }_{\mathrm{down}}\right)k_{\mathrm{down}}\\ k_{\mathrm{down}}-1-{\alpha }_{\mathrm{up}}{k}_{\mathrm{up}}& (k_{\mathrm{down}}-{\beta }_{\mathrm{down}}{k}_{\mathrm{down}}+{\beta }_{\mathrm{down}}\end{array}\right]\left[\begin{array}{c}{u}_{\mathrm{mid},n-1}\\ \frac{i_{\mathrm{down},n-1}}{G_2}\end{array}\right]+\left[\begin{array}{c}\left(1-k_{\mathrm{up}}-k_{\mathrm{down}}\right)u_{\mathrm{pv}}\\ \left(1-k_{\mathrm{up}}-k_{\mathrm{down}}\right)u_{\mathrm{pv}}\end{array}\right]=A\left[\begin{array}{c}{u}_{\mathrm{mid},n-1}\\ \frac{i_{\mathrm{down},n-1}}{G_2}\end{array}\right]+B,$$\mathrm{where}{k}_1=\frac{G_{\mathrm{eq}1}}{G_{\mathrm{eq}1}+G_{\mathrm{eq}2}+G_L},k_2=\frac{G_{\mathrm{eq}2}}{G_{\mathrm{eq}1}+G_{\mathrm{eq}2}+G_L}$

[0060] Step (44), transient operating characteristics of the parameterized model are analyzed, to obtain corresponding parameters of the model in two different operating states as follows:

[00014]$\mathrm{when}\{\begin{array}{c}{S}_{\mathrm{up}}=1\\ S_{\mathrm{down}}=0\end{array};$$\{\begin{array}{c}{i}_{\mathrm{up}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t\right)+\frac{k_{\mathrm{down}}+\sqrt{k_{\mathrm{down}}}}{k_{\mathrm{up}}}{G}_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t-\Delta t\right)+i_{\mathrm{up}}\left(t-\Delta t\right)\\ i_{\mathrm{down}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t\right)-G_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t-\Delta t\right)+\frac{\sqrt{k_{\mathrm{down}}}}{\sqrt{k_{\mathrm{down}}+1}}{i}_{\mathrm{down}}\left(t-\Delta t\right)\end{array};$$\mathrm{when}\{\begin{array}{c}{S}_{\mathrm{up}}=0\\ S_{\mathrm{down}}=1\end{array};$$\{\begin{array}{c}{i}_{\mathrm{up}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t\right)-G_{\mathrm{eq}}{u}_{\mathrm{up}}\left(t-\Delta t\right)+\frac{\sqrt{k_{\mathrm{up}}}}{\sqrt{k_{\mathrm{up}}+1}}{i}_{\mathrm{up}}\left(t-\Delta t\right)\\ i_{\mathrm{down}}\left(t\right)=G_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t\right)+\frac{k_{\mathrm{up}}+\sqrt{k_{\mathrm{up}}}}{k_{\mathrm{down}}}{G}_{\mathrm{eq}}{u}_{\mathrm{down}}\left(t-\Delta t\right)+i_{\mathrm{down}}\left(t-\Delta t\right)\end{array};$

[0061] Step (45), models for the control link, grid-side interface, etc. of the electromagnetic transient simulation system of the converter are established, combining the basic equation I=YU of the electromagnetic transient simulation system of the whole grid;

[0062] Step (46), the electromagnetic transient simulation equation of the converter is solved in combination with interface parameters, to obtain the current state quantity of each node for updating the electromagnetic transient equivalent admittance matrix and historical current source, and step (43) is returned to continue the calculation until the simulation termination time arrives. The following compares electromagnetic transient model simulation waveforms of three different power electronic converters to illustrate the technical advantages of the parametric constant admittance modeling method for the converter based on cross initialization.

[0063] Simulation modeling is performed on a three-phase bridge rectifier system, with a simulation step size of 1 μs. Relevant parameters of the converter model are shown in Table 1. The equivalent electromagnetic transient simulation model of the converter is shown in FIG. 2. The principle of cross initialization is shown in FIG. 3. The simulation waveform comparison of a Ron/Roff model, a LC model and this corrected model is shown in FIGS. 4-6. FIG. 4 shows voltage comparison of A-phase upper arm switches S.sub.1, FIG. 5 shows power loss comparison of A-phase upper arm switches S.sub.1, and FIG. 6 shows power comparison of A-phase output active power.

TABLE-US-00001 TABLE 1 Relevant parameters of converter model Relevant parameters of converter model Parameter size AC voltage source line voltage effective value U.sub.m(V) 380 AC voltage source frequency f.sub.ac(Hz) 50 DC side load R(Ω) 1 DC side capacitance C(mF) 5 Internal equivalent stray resistance R.sub.s(Ω) of the 0.1 converter Internal equivalent stray inductance L.sub.s(mH) of the 8 converter Inverter switch equivalent admittance G.sub.eq(S) 1 Rated active power P(kW) 45 Rated reactive power Q(kvar) 0 Carrier frequency f.sub.T(Hz) 5000

[0064] It can be seen from FIG. 4-6 that the waveform of the corrected converter parameterization model (thin solid line) is closer to that of the Ron/Roff model (thick dashed line) than the waveform of the LC model (thick dotted line). The converter parameterization model based on cross initialization can improve the simulation convergence performance of a converter model and greatly reduce the virtual power loss at the time of state switching. Meanwhile, it can be seen from FIGS. 4-6 that the converter parameterization model based on cross initialization and the Ron/Roff model have substantially identical simulation results, which shows the effectiveness of the method proposed in this invention. It can be seen from FIGS. 4-6 that, in the above-mentioned converter system, without affecting the simulation speed, the converter parameterization model based on cross initialization proposed in this invention has high precision, minimal virtual power loss, and desired steady-state and transient operating characteristics.