Voltage-based converter stability assessment method

Abstract

This invention provides a voltage-based converter stability evaluation method, comprising the following steps: S1. Injecting single-phase voltage disturbances of different frequencies into the common coupling point of the converter; S2. Obtaining the line voltage V of the converter under the single-phase voltage disturbance. ab and V bc and the line voltage V on the grid side t,ab S3. Based on line voltage V ab and V bc Determine the positive sequence component V of the converter's response voltage. p Based on line voltage V t,ab and line voltage V bc Determine the positive sequence component V of the grid-side response voltage. t,p S4. Based on positive-order component V t,p With the positive-order component V p S5. Plot a Bode plot of the ratio Vtp / Vp; Find the point in the Bode plot where Vtp / Vp is 0, and determine the crossover frequency f. c The stability of the converter is determined based on the phase corresponding to the crossover frequency.

Description

Technical Field

[0001] This invention relates to a method for evaluating the stability of a converter, and more particularly to a voltage-based method for evaluating the stability of a converter. Background Technology

[0002] Converters are widely used in new energy, aerospace, shipbuilding, rail transportation and other fields. The stability of the converter system is important to the application scenario and is the key to ensuring the safe and reliable operation of the power system.

[0003] The most common methods for evaluating the stability of converters are state-space stability assessment and impedance-based stability assessment. The former requires obtaining the control structure and parameters of the converter and its system to achieve stability evaluation. However, the internal structural parameters of the converter are generally difficult to obtain accurately. The latter, on the other hand, avoids the need to know the control structure and parameters; it only requires obtaining the voltage and current responses at the ports to analyze system stability. Therefore, impedance-based stability assessment methods are widely used in practical engineering. However, existing impedance stability assessment methods evaluate stability by comparing the impedance ratio of two subsystems. Obtaining the impedance of each subsystem requires acquiring the voltage and current responses, leading to an excessive number of sensors used to measure voltage and current, and an increase in the amount of measurement data processed, thus increasing the cost of analyzing system stability. Moreover, impedance analysis requires establishing corresponding analytical models, whose algorithms are complex and relatively inefficient.

[0004] Therefore, in order to solve the above-mentioned technical problems, it is urgent to propose a new technical approach. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a voltage-based converter stability assessment method. When assessing the stability of a converter, only the voltage signals on the converter side and the grid side need to be obtained, without the need to set up other signal sensors, thereby reducing the measurement cost. Moreover, there is no need to establish signal models such as impedance during the stability judgment process, the algorithm is relatively simple, more efficient, and has good accuracy.

[0006] This invention provides a voltage-based converter stability evaluation method, comprising the following steps:

[0007] S1. Inject single-phase voltage disturbances of different frequencies into the common coupling point of the converter;

[0008] S2. Obtain the line voltage V of the converter under single-phase voltage disturbance. ab and V bc and the line voltage V on the grid side t,ab ;

[0009] S3. Based on line voltage V aband V bc Determine the positive sequence component V of the converter's response voltage. p Based on line voltage V t,ab and line voltage V bc Determine the positive sequence component V of the grid-side response voltage. t,p ;

[0010] S4. Based on positive sequence component V t,p With the positive-order component V p Plot a Bode plot using the ratios;

[0011] S5. Locate the point where Vtp / Vp is 0 in the Bode plot and determine the crossover frequency f. c The stability of the converter is determined based on the phase corresponding to the crossover frequency.

[0012] Furthermore, step S5 specifically includes:

[0013] In the Bode plot, find the point where |Vtp / Vp| = 0; the corresponding frequency f is... c Just for the frequency of crossing;

[0014] By crossing frequency f c The corresponding phase is determined. When the phase is greater than or equal to -180°, the converter is in a stable state; otherwise, it is in an unstable state.

[0015] Furthermore, the positive-sequence component V of the converter's response voltage is determined using the following method. p :

[0016] ;

[0017] Where: V n This represents the negative sequence component of the converter response voltage.

[0018] Furthermore, the positive-sequence component V of the grid-side response voltage is determined using the following method. t,p :

[0019] ;

[0020] Where: V t,n This represents the negative sequence component of the grid-side response voltage.

[0021] The beneficial effects of this invention are as follows: When evaluating the stability of a converter, only the voltage signals of the converter side and the grid side need to be obtained, without the need to set up other signal sensors, thereby reducing the measurement cost. Moreover, there is no need to establish signal models such as impedance during the stability judgment process, the algorithm is relatively simple, more efficient, and has good accuracy. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0023] Figure 1 This is a schematic diagram of the process of the present invention.

[0024] Figure 2 This is a schematic diagram of the measurement using existing methods.

[0025] Figure 3 This is a schematic diagram of the measurement method of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below:

[0027] This invention provides a voltage-based converter stability evaluation method, comprising the following steps:

[0028] S1. Inject single-phase voltage disturbances of different frequencies into the common coupling point of the converter; that is, it is possible to inject disturbances into any one of the three phases at the common coupling point.

[0029] S2. Obtain the line voltage V of the converter under single-phase voltage disturbance. ab and V bc and the line voltage V on the grid side t,ab ;

[0030] S3. Based on line voltage V ab and V bc Determine the positive sequence component V of the converter's response voltage. p Based on line voltage V t,ab and line voltage V bc Determine the positive sequence component V of the grid-side response voltage. t,p ;

[0031] S4. Based on positive sequence component V t,p With the positive-order component V p Plot a Bode plot using the ratios;

[0032] S5. Locate the point where Vtp / Vp is 0 in the Bode plot and determine the crossover frequency f. c The stability of the converter is determined based on the phase corresponding to the crossover frequency. Using this method, only voltage signals from the converter side and the grid side need to be acquired for converter stability assessment; no other signal sensors are required, thus reducing measurement costs. Furthermore, the stability judgment process does not require establishing impedance or other signal models, making the algorithm relatively simple, more efficient, and accurate.

[0033] In this embodiment, step S5 specifically includes:

[0034] In the Bode plot, find the point where |Vtp / Vp| = 0; the corresponding frequency f is... c The Bode plot is plotted using the logarithm of amplitude and frequency. Therefore, when Vtp = Vp, a point with a value of 0 will appear on the Bode plot. If there is no 0 point, it indicates that the converter is unstable. If it appears, further judgment is required.

[0035] By crossing frequency f c Determine the corresponding phase. When the phase is greater than or equal to -180°, the converter is in a steady state; otherwise, it is in an unstable state. Figure 3 As shown, in Figure 3 Find the point where the logarithm of |Vtp / Vp| is 0, then determine the frequency, and finally determine the corresponding phase based on that frequency in the phase calculation. Figure 3 The example given has a phase of 39°, which satisfies the condition, indicating whether the converter is stable at this point. Furthermore, through... Figure 2 and Figure 3 Comparison: In Figure 2 In traditional methods, two curves need to be determined, but in this invention, only one curve is required. The process is relatively simpler, and there is no need to establish corresponding impedance analysis models and corresponding signal analysis models. However, the accuracy is consistent with that of existing methods.

[0036] In this embodiment, the positive sequence component V of the converter's response voltage is determined by the following method. p :

[0037] ;

[0038] Where: V n This represents the negative sequence component of the converter response voltage.

[0039] The positive-sequence component V of the grid-side response voltage is determined by the following method. t,p :

[0040] ;

[0041] Where: V t,n This represents the negative sequence component of the grid-side response voltage.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A voltage-based converter stability evaluation method, characterized in that: Includes the following steps: S1. Inject single-phase voltage disturbances of different frequencies into the common coupling point of the converter; S2. Obtain the line voltage V of the converter under single-phase voltage disturbance. ab and V bc and the line voltage V on the grid side t,ab ; S3. Based on line voltage V ab and V bc Determine the positive sequence component V of the converter's response voltage. p Based on line voltage V t,ab and line voltage V bc Determine the positive sequence component V of the grid-side response voltage. t,p ; S4. Based on positive sequence component V t,p With the positive-order component V p Plot a Bode plot using the ratios; S5. Locate the point where Vtp / Vp is 0 in the Bode plot and determine the crossover frequency f. c The stability of the converter is determined based on the phase corresponding to the crossover frequency.

2. The voltage-based converter stability evaluation method according to claim 1, characterized in that: Step S5 specifically includes: In the Bode plot, find the point where |Vtp / Vp| = 0; the corresponding frequency f is... c Just for the frequency of crossing; By crossing frequency f c The corresponding phase is determined. When the phase is greater than or equal to -180°, the converter is in a stable state; otherwise, it is in an unstable state.

3. The voltage-based converter stability evaluation method according to claim 1, characterized in that: The positive sequence component V of the converter's response voltage is determined using the following method. p : ； Where: V n This represents the negative sequence component of the converter response voltage.

4. The voltage-based converter stability evaluation method according to claim 1, characterized in that: The positive-sequence component V of the grid-side response voltage is determined by the following method. t,p : ； Where: V t,n This represents the negative sequence component of the grid-side response voltage.

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