A Phase Sequence Detection and Adaptive Adjustment Method for Energy Storage Inverters

Abstract

The present invention relates to the technical field of phase sequence detection, and discloses a phase sequence detection and adaptive adjustment method for an energy storage converter. The phase sequence detection method determines whether the phase sequence of the energy storage converter is positive or negative based on the per-unit value of the sampled voltage at a certain moment and the per-unit value of the voltage after a set delay duration. The present invention solves the problems existing in the prior art, such as large computational amount and much occupation of processor resources.

Description

Technical Field

[0001] The present invention relates to the technical field of phase sequence detection, and specifically to a phase sequence detection and adaptive adjustment method for an energy storage converter. Background Art

[0002] With the rapid growth of power energy storage demand, energy storage converters are widely used in AC-DC bidirectional conversion to realize the charging and discharging of batteries. When the energy storage converter needs to be connected to the grid, an incorrect grid incoming phase sequence will cause the grid connection to fail. Therefore, after the energy storage converter is powered on, it is necessary to detect the phase sequence of the AC port to ensure the normal operation of the device.

[0003] Currently, phase sequence detection mainly relies on phase sequence detection devices or embedded software. Undoubtedly, adding a phase sequence detection device will increase the cost and structural complexity of the energy storage converter. Therefore, some energy storage converter manufacturers judge the phase sequence based on the analog quantity sampling results of the device itself combined with software algorithms. For example, judging according to the characteristics of positive sequence data combined with phase, or performing Fourier transform on the sampling data and then judging according to the square wave time sequence, and decomposing the positive and negative sequence components in the rotating coordinate system and then judging, etc. The above software methods require a large amount of calculation, which will occupy a lot of resources of the embedded processor, thus affecting the software design and development of the energy storage converter. Therefore, a simple and effective phase sequence judgment method is necessary. Summary of the Invention

[0004] To overcome the deficiencies of the prior art, the present invention provides a phase sequence detection and adaptive adjustment method for an energy storage converter, which solves the problems existing in the prior art such as large calculation amount and much occupation of processor resources.

[0005] The technical solution adopted by the present invention to solve the above problems is as follows:

[0006] A phase sequence detection method for an energy storage converter, which judges whether the phase sequence of the energy storage converter is positive sequence or negative sequence based on the per-unit value of the sampled voltage at a certain moment and the per-unit value of the voltage after a delay setting duration.

[0007] As a preferred technical solution, it includes the following steps:

[0008] S1, Sampling: Obtain the grid voltage through a voltage sampling circuit and perform per-unit conversion to obtain U a 、U b 、U c ; where U a represents the grid voltage of phase A, U b represents the grid voltage of phase B, and U c represents the grid voltage of phase C;

[0009] S2, Denoising processing: Perform denoising processing on the sampling result to obtain Where represents the per-unit value of the grid voltage of phase A after denoising, represents the per-unit value of the grid voltage of phase B after denoising, represents the per-unit value of the grid voltage of phase C after denoising;

[0010] S3, Feature extraction: Based on the denoised extract the first eigenvalue V1 and the second eigenvalue V2;

[0011] S4, Phase sequence judgment: When the first eigenvalue V1 is greater than the second eigenvalue V2, it is determined that the phase sequence of the energy storage converter is positive sequence; otherwise, it is determined that the phase sequence of the energy storage converter is negative sequence.

[0012] As a preferred technical solution, in step S2, the feature extraction method is:

[0013]

[0014] If then V1 = U d1 ;

[0015] If the sampling time is delayed by T / 10, then V2 = U d2 ;

[0016] where U d represents the feature voltage, U d1 represents the feature voltage value of the first feature point, U dc represents the feature voltage value of the second feature point, and T represents the voltage period.

[0017] As a preferred technical solution, in step S1, the sampled three-phase voltages are all phase voltages, or the sampled three-phase voltages are all line voltages.

[0018] As a preferred technical solution, in step S2, the sampling result is processed by moving average to achieve denoising.

[0019] An energy storage converter phase sequence adaptive adjustment method includes the above-mentioned energy storage converter phase sequence detection method, and further includes the following steps:

[0020] S5, Phase sequence adaptive adjustment: If the phase sequence judgment result in step S4 is positive sequence, the energy storage converter operates according to the default setting; if the phase sequence judgment result in step S4 is negative sequence, then exchange the sampling results and their corresponding drive signals of any two-phase sampling channels.

[0021] As a preferred technical solution, the drive signal in step S5 is the IGBT drive signal.

[0022] As a preferred technical solution, the energy storage converter adopted includes an AC circuit breaker, an AC contactor, an AC three-phase reactor, an isolation transformer, an AC / DC module, a DC relay, and a DC circuit breaker that are electrically connected in sequence. The input end of the circuit breaker is used to input the grid voltage and sample the grid voltage, and the AC contactor is used to sample the inversion voltage.

[0023] As a preferred technical solution, the energy storage converter adopted further includes a bus capacitor, and the node between the AC / DC module and the DC relay is electrically connected to the bus capacitor.

[0024] As a preferred technical solution, the energy storage converter adopted further includes a filter capacitor, and the node between the AC contactor and the AC three-phase reactor is electrically connected to the filter capacitor.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention is relatively simple to implement, can reduce the occupation of microprocessor resources, and improve the efficiency of phase sequence detection;

[0027] (2) After detecting a phase sequence error, the present invention can be directly processed by software, avoiding the costs brought by re-wiring or other situations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a topology diagram of the energy storage converter adopted in the embodiment of the present invention;

[0029] Figure 2 It is a schematic diagram of the positive sequence feature extraction result;

[0030] Figure 3 It is a schematic diagram of the negative sequence feature extraction result;

[0031] Figure 4 It is a schematic diagram of the steps of a phase sequence adaptive adjustment method for an energy storage converter according to the present invention.

[0032] Marks and corresponding component names in the drawings: 1. DC circuit breaker, 2. AC contactor, 3. AC three-phase reactor, 4. Isolation transformer, 5. AC / DC module, 6. Bus capacitor, 7. Filter capacitor, 8. DC relay, 9. DC circuit breaker. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following further describes the present invention in detail in conjunction with the embodiments and the drawings, but the embodiments of the present invention are not limited thereto.

[0034] Embodiment 1

[0035] As Figures 1 to 4As shown, the main purpose of the present invention is to avoid performing effective but computationally intensive operations such as Fourier transform and dual synchronous coordinate decoupling phase-locked loop (DDSRF-SPLL) during phase sequence judgment, and reduce the microprocessor resources occupied by using software methods to implement the AC line phase sequence judgment of the energy storage converter. When the phase sequence is judged to be incorrect, the AC input and output of the energy storage converter can be adjusted to the correct phase sequence through phase sequence self-adaptation, so as to realize the normal grid connection function without changing the wiring.

[0036] In order for the energy storage converter to be successfully grid-connected and avoid a large inrush current during grid connection, voltage sampling is respectively performed on both sides of the switch at the AC output end as Figure 1 shown. After the device is powered on, the grid phase sequence is judged based on the voltage sampling results on the grid side.

[0037] Figure 1 The topology of the energy storage converter adopted by the present invention is shown. Voltage sampling points are shown on the 400V / 50Hz grid input side, and current sampling points are provided at the reactor. Both of them collect data of three phases A, B, and C. The AC / DC module is mainly composed of IGBTs, and the IGBTs are driven by three-phase PWM signals. The adopted energy storage converter includes an AC circuit breaker 1 (an AC molded case circuit breaker is adopted in this embodiment), an AC contactor 2, an AC three-phase reactor 3, an isolation transformer 4, an AC / DC module 5, a DC relay 8, and a DC circuit breaker 9 (a DC molded case circuit breaker is adopted in this embodiment) that are electrically connected in sequence. The input end of the circuit breaker 1 is used to input the grid voltage and grid voltage sampling, and the AC contactor 2 is used for inverter voltage sampling. Preferably, the adopted energy storage converter further includes a bus capacitor 6, and the node between the AC / DC module 5 and the DC relay 8 is electrically connected to the bus capacitor 6. Preferably, the adopted energy storage converter further includes a filter capacitor 7, and the node between the AC contactor 2 and the AC three-phase reactor 3 is electrically connected to the filter capacitor 7.

[0038] Since the preliminary sampled data is contaminated with relatively large noise, the sampled data needs to be filtered before judgment, and then feature extraction is performed from the processed data for phase sequence judgment. When the phase sequence is correct, the energy storage converter operates normally; when the phase sequence is incorrect, the grid voltage, inverter voltage, and current sampling results of any two phases (A, B or B, C or A, C) are exchanged with each other, so that the control system obtains positive sequence data for implementing the normal control algorithm. Finally, the PWM drive signals of the two phases output by the control system (corresponding to the two phases of the exchanged sampled data) are exchanged to ensure the consistency of input and output, thereby realizing the function of phase sequence self-adaptation.

[0039] Figure 2 In, U c is the data after filtering the C-phase voltage sampling, U dThe data obtained after collecting and filtering the voltages of phase A and phase B and then extracting features. The positive-sequence voltages UVW, VWU, and WUV are all Figure 2 Results.

[0040] Figure 3 In, U c Is the data after sampling and filtering the voltage of phase C, and U d Is the data obtained after collecting and filtering the voltages of phase A and phase B and then extracting features. The negative-sequence voltages UWV, WVU, and VUW are all Figure 3 Results.

[0041] The present invention is relatively simple to implement, can reduce the occupation of microprocessor resources, and improve the efficiency of phase sequence detection. After detecting a phase sequence error, it can be directly processed by software to avoid the costs brought by re-wiring or other situations.

[0042] Embodiment 2

[0043] As Figures 1 to 4 Shown, as a further optimization of Embodiment 1, on the basis of Embodiment 1, this embodiment further includes the following technical features:

[0044] Using the present invention for phase sequence adaptive adjustment of the energy storage converter, the specific implementation process is as follows:

[0045] Step 1: Obtain the grid voltage through the voltage sampling circuit and perform per-unit conversion to obtain: U a , U b , U c , Either phase voltage or line voltage sampling can be used, but it needs to be unified.

[0046] Step 2: Perform moving average processing on the sampling results to avoid the influence of noise on the judgment results.

[0047]

[0048] The parameter meanings are as follows:

[0049] Moving Average: Moving average processing;

[0050] U a , U b , U c : Initial sampling per-unit value;

[0051] Sampling and filtering results.

[0052] Step 3: Extract features. The extraction results are as Figure 2 And Figure 3 Shown, in the case of positive-sequence voltage, the peak value of U d Slightly leads Under negative-sequence voltage conditions, U d The peak value lags slightly

[0053] (i.e., in this case, U d = U d1 );

[0054] Delay (i.e., in this case, U d = U d2 );

[0055] U d : Characteristic data.

[0056] V1, V2, U d1 , U d2 : Characteristic data when the conditions are met;

[0057] T is defaulted to 0.02 s.

[0058] Step 4: Determine the phase sequence. It is difficult to directly determine whether it is leading or lagging through data, so a simple and effective determination method is proposed. That is, when the per-unit value of the sampled voltage is greater than 0.9, record the first characteristic value V1 at this time, and record the second characteristic value V2 at this moment after a delay of T / 10. When the first characteristic value V1 is greater than the second characteristic value V2, it can be determined that it belongs to the positive-sequence situation, and vice versa for the negative-sequence situation.

[0059]

[0060]

[0061] UVW, VWU, WUV: Positive phase sequence;

[0062] UWV, WVU, VUW: Negative phase sequence.

[0063] Step 5: Phase-sequence adaption. If the phase-sequence result is positive-sequence, the energy storage converter operates normally according to the default settings. If it is negative-sequence, exchange any two-phase sampling channels and the corresponding IGBT drive signals. For example, exchange the voltage and current sampling data of phases A and B. The exchanged voltage data is positive-sequence, and normal results can be obtained when performing coordinate transformation and positive-negative sequence decomposition, so as to ensure the smooth completion of the inner and outer loop PI control in the dq rotating coordinate system. Since the final modulation wave is based on the exchanged sampling channels of phases A and B, it is necessary to exchange the PWM drive signals of phases A and B to ensure the correct correspondence of input and output and realize the smooth grid connection function of the energy storage converter.

[0064]

[0065] PWM a , PWM b : PWM drive signals for phases a and b.

[0066] As described above, the present invention can be preferably implemented.

[0067] All features disclosed in all embodiments in this specification, or steps in all methods or processes implicitly disclosed, except for mutually exclusive features and / or steps, can be combined and / or extended and / or replaced in any manner.

[0068] The above description is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. According to the technical essence of the present invention, any simple modification, equivalent replacement, and improvement made to the above embodiments within the spirit and principle of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A phase sequence detection method for an energy storage converter, characterized in that, Based on the per-unit value of the sampled voltage at a certain moment and the per-unit value of the voltage after the set delay duration, determine whether the phase sequence of the energy storage converter is positive or negative; It includes the following steps: S1, Sampling: Obtain the grid voltage through the voltage sampling circuit and perform per-unit processing to obtain U a , U b , U c ; Among them, U a represents the grid voltage of phase A, U b represents the grid voltage of phase B, U c represents the grid voltage of phase C; S2, Denoising processing: Perform denoising processing on the sampling result to obtain wherein represents the per-unit value of the grid voltage of phase A after denoising, represents the per-unit value of the grid voltage of phase B after denoising, represents the per-unit value of the grid voltage of phase C after denoising; S3, Feature extraction: Based on the denoised extract the first eigenvalue V1 and the second eigenvalue V2; S4, Phase sequence judgment: When the first eigenvalue V1 is greater than the second eigenvalue V2, it is determined that the phase sequence of the energy storage converter is positive; otherwise, it is determined that the phase sequence of the energy storage converter is negative.

2. The phase sequence detection method of an energy storage converter according to claim 1, characterized in that In step S2, the feature extraction method is: If then V1 = U d1 ; If the sampling time is delayed by T / 10, then V2 = U d2 ; Among them, U d represents the characteristic voltage, U d1 represents the characteristic voltage value of the first characteristic point, U d2 represents the characteristic voltage value of the second characteristic point, and T represents the voltage period.

3. The phase sequence detection method of an energy storage converter according to claim 2, wherein In step S1, the sampled three-phase voltages are all phase voltages, or the sampled three-phase voltages are all line voltages.

4. A phase sequence detection method for an energy storage converter according to claim 3, characterized in that In step S2, perform a moving average process on the sampling result to achieve noise reduction.

5. A method for adaptively adjusting the phase sequence of an energy storage converter, characterized in that, It includes a method for detecting the phase sequence of an energy storage converter according to any one of claims 2 to 4, and further includes the following steps: S5, Phase sequence adaptive adjustment: If the phase sequence judgment result in step S4 is positive, the energy storage converter operates according to the default setting; if the phase sequence judgment result in step S4 is negative, then exchange the sampling results of any two-phase sampling channels and their corresponding drive signals.

6. A method for adaptively adjusting the phase sequence of an energy storage converter according to claim 5, characterized in that, The drive signal described in step S5 is an IGBT drive signal.

7. A method for adaptively adjusting the phase sequence of an energy storage converter according to claim 6, characterized in that The adopted energy storage converter includes an AC circuit breaker (1), an AC contactor (2), an AC three-phase reactor (3), an isolation transformer (4), an AC / DC module (5), a DC relay (8), and a DC circuit breaker (9) that are electrically connected in sequence. The input end of the circuit breaker (1) is used to input the grid voltage and the grid voltage sampling, and the AC contactor (2) is used for inverter voltage sampling.

8. A method for adaptively adjusting the phase sequence of an energy storage converter according to claim 7, characterized in that, The adopted energy storage converter further includes a bus capacitor (6), and the node between the AC / DC module (5) and the DC relay (8) is electrically connected to the bus capacitor (6).

9. A method for adaptively adjusting the phase sequence of an energy storage converter according to claim 7, characterized in that, The adopted energy storage converter further includes a filter capacitor (7), and the node between the AC contactor (2) and the AC three-phase reactor (3) is electrically connected to the filter capacitor (7).

Images