Energy storage converter voltage stabilization control method

Abstract

The application provides a voltage stability control method of an energy storage converter, which is controlled by an inductance current and a capacitance voltage of an LC filter; a voltage reference value is generated by voltage frequency droop control calculation, and voltage outer loop and current inner loop are adopted for control, and PI controllers are adopted for the voltage loop and the current loop; a difference between a nonlinear load sampling current and a nonlinear load rated current and a calculated filter capacitance current are fed forward to the current loop to change the reference value of the current loop. The voltage robust droop control method of the energy storage converter can reduce the medium frequency band impedance of the energy storage converter, solve the problem of serious voltage distortion of the energy storage converter when the energy storage converter is used with a nonlinear load, realize the function of voltage stability control of the energy storage converter, and effectively improve the power quality of power supply of the energy storage converter.

Description

Technical Field

[0001] This invention belongs to the field of power electronic converter control and relates to a voltage stability control method for energy storage converters, which is applicable to the control of power electronic converters. Background Technology

[0002] Currently, energy storage converters are widely used as mobile power sources. However, due to their limited capacity, they are prone to voltage distortion under load disturbances. Voltage stabilization control of energy storage converters can improve the power quality of the power supply and ensure the normal operation of the power load, which has important research value and significance.

[0003] Energy storage converters employing droop control can automatically adjust their output voltage according to the load power. However, under nonlinear load disturbances, these converters exhibit severe voltage distortion, significantly impacting the power supply quality. Nonlinear loads are common electrical loads, and active power filters are frequently used to compensate for harmonic currents, thereby improving the power supply quality of energy storage converters. However, some energy storage converter power supply systems lack active power filters. Therefore, this paper proposes a voltage stabilization control method for energy storage converters to address the voltage distortion problem under nonlinear load disturbances and ensure output voltage stability. Summary of the Invention

[0004] This invention provides a voltage stability control method for energy storage converters, improving the power supply quality of energy storage converters and solving the problem of voltage distortion in energy storage converters under nonlinear load disturbances. This invention includes the following steps:

[0005] Step (1): Acquire the inductor current i of the LC filter a i b i c and capacitor voltage v a ,v b ,v c To perform power calculations, the instantaneous output power P and Q of the energy storage converter are obtained. The instantaneous active power P and reactive power Q of the energy storage converter are:

[0006]

[0007] In the formula, v d and v q For the LC filter capacitor voltage v a ,v b ,v c The value of i in the dq coordinate system d and i q For the LC filter inductor current i a i b ic The value in the dq coordinate system;

[0008] The voltage reference value's amplitude and frequency are calculated and generated through voltage frequency droop control. The voltage reference value amplitude V and voltage reference value frequency f are:

[0009]

[0010] In the formula, f0 is the rated frequency of the output voltage of the energy storage converter, V0 is the rated amplitude of the output voltage of the energy storage converter, m is the active power droop coefficient, n is the reactive power droop coefficient, P0 is the rated active power of the energy storage converter, and Q0 is the rated reactive power of the energy storage converter.

[0011] The three-phase voltage reference value v is calculated using the voltage reference value amplitude V and the voltage reference value frequency f. aref ,v bref ,v cref Voltage reference value v aref ,v bref ,v cref for:

[0012]

[0013] In the formula, π is the coefficient of pi, t is the time coefficient, and cos() is the cosine function;

[0014] Through the voltage reference value v aref ,v bref ,v cref Calculate the voltage reference value v in the dq domain dref and v qref Voltage v dref and v qref for:

[0015]

[0016] In the formula, sin() is the sine function;

[0017] Step (2): Voltage v dref and v qref With voltage v d With v q The difference is calculated separately, by analyzing the voltage difference (v) dref -v d ) and (v qref -v q Perform PI calculations to obtain the control current i. dv and i qv Current i dv and i qv for:

[0018]

[0019] In the formula, G v (s) is the transfer function of the voltage loop PI controller, ω n C is the rated angular frequency of the output voltage of the energy storage converter. f This represents the filter capacitor value of the LC filter;

[0020] Acquire current i on nonlinear load na i nb i nc , will current i na i nb i nc The current i is obtained by performing an abc / dq transformation. dn with i qn Current i dn with i qn for:

[0021]

[0022] The rated current I under the dq axis is obtained from the rated active power P0 and rated reactive power Q0 of the energy storage converter. dn and I qn Rated current I dn and I qn for:

[0023]

[0024] The capacitor voltage v through the LC filter d v q With filter capacitor C f Calculate the d-axis filter capacitor current i. cd and q-axis filter capacitor current i cq for:

[0025]

[0026] Where s is the differential operator, C f It is the filter capacitor of the LC filter, v d and v q It is v a ,v b ,v c Voltage in the dq coordinate system;

[0027] According to the current I dn i dn i cd i dv The current loop command i of the d-axis system is calculated. dref According to the current I qn iqn i cq i qv The current loop command i of the q-axis system is calculated. qref Current loop instruction i dref and i qref for:

[0028]

[0029] Step (3): Current i dref and i qref With current i d with i q By taking the difference between the currents (i) dref -i d ) and (i qref -i q The control voltage e is obtained by performing PI calculation. d and e q Voltage e d and e q for:

[0030]

[0031] In the formula, G i (s) is the transfer function of the current loop PI controller, L f This represents the filter inductance value of the LC filter.

[0032] Through voltage e d and e q Calculate the internal voltage signal e a ,e b ,e c Internal voltage signal e a ,e b ,e c for:

[0033]

[0034] Through internal voltage signal e a ,e b ,e c Calculate the modulated signal s a =e a / (V dc / 2), s b =e b / (V dc / 2), s c =e c / (V dc / 2), V dc The DC-side voltage of the energy storage converter is determined by the modulation signal s. a ,sb ,s c PWM modulation is used to control the on and off of the switching transistors of the energy storage converter;

[0035] Step (4): Obtain the voltage v using the sequence impedance modeling method. d ,v q and current i d i q The frequency domain expression is:

[0036]

[0037]

[0038] In the formula, e is the natural constant, j is the imaginary unit, and ω p ω1 is the angular frequency of the disturbance voltage of the energy storage converter, ω1 is the angular frequency of the fundamental voltage of the energy storage converter, and δ is the angular frequency of the disturbance voltage of the energy storage converter. p1 β1 is the initial phase angle of the energy storage converter output voltage in the dq coordinate system, and α is the initial phase angle of the energy storage converter output voltage in the dq coordinate system. p1 It is the phase angle of the nonlinear load current, V p1 It is the rated amplitude of the output voltage of the energy storage converter, I p1 It is the rated amplitude of the nonlinear load current;

[0039] pass Figure 1 The circuit relationship of the energy storage converter can be obtained as follows:

[0040]

[0041] In the formula R f It is the resonant damping resistor of the LC filter;

[0042] According to equations (1) to (14), the impedance of the energy storage converter under the control strategy can be obtained:

[0043]

[0044] In the formula, Z in (s) is the analytical expression for the impedance of the energy storage converter, ω n This is the angular frequency of the rated voltage of the energy storage converter.

[0045] Compared with existing technologies, the method has the following advantages and effects:

[0046] (1) Under nonlinear load disturbance, the energy storage converter can actively compensate for harmonic current, so the energy storage converter voltage stability control method and system can operate stably and the total harmonic quantity of the energy storage converter output voltage is less than 5%.

[0047] (2) Since the method does not require the use of filters to extract harmonics, the method has a smaller computational load compared with active filter harmonic mitigation technology;

[0048] (3) Compared with the energy storage converter using droop control, the energy storage converter using the control has a smaller impedance in the mid-frequency band and is more like an ideal voltage source in the mid-frequency band. Under the control method, the energy storage converter has a stronger ability to suppress mid-frequency harmonics. Attached Figure Description

[0049] Figure 1 The diagram below shows the voltage stabilization control method and system block diagram for the energy storage converter.

[0050] Figure 2 This is a comparison diagram of the impedance-frequency characteristics of the energy storage converter under the aforementioned control method and the droop control method.

[0051] Figure 3 The experimental waveform diagram of the energy storage converter under droop control.

[0052] Figure 4 The experimental waveform diagram of the controlled energy storage converter is shown. Detailed Implementation

[0053] This application proposes a voltage stabilization control method for an energy storage converter, which is described in detail below with reference to the accompanying drawings:

[0054] Figure 1 This is a block diagram of the voltage stabilization control method and system for the energy storage converter. The inductor current i of the LC filter is collected. a i b i c and capacitor voltage v a ,v b ,v c To perform power calculations, the instantaneous output power P and Q of the energy storage converter are obtained. The instantaneous active power P and reactive power Q of the energy storage converter are:

[0055]

[0056] In the formula, v d and v q For the LC filter capacitor voltage v a ,v b ,v c The value of i in the dq coordinate system d and i q For the LC filter inductor current i a i b i c The value in the dq coordinate system;

[0057] The voltage reference value's amplitude and frequency are calculated and generated through voltage frequency droop control. The voltage reference value amplitude V and voltage reference value frequency f are:

[0058]

[0059] In the formula, f0 is the rated frequency of the output voltage of the energy storage converter, V0 is the rated amplitude of the output voltage of the energy storage converter, m is the active power droop coefficient, n is the reactive power droop coefficient, P0 is the rated active power of the energy storage converter, and Q0 is the rated reactive power of the energy storage converter.

[0060] The three-phase voltage reference value v is calculated using the voltage reference value amplitude V and the voltage reference value frequency f. aref ,v bref ,v cref Voltage reference value v aref ,v bref ,v cref for:

[0061]

[0062] In the formula, π is the coefficient of pi, t is the time coefficient, and cos() is the cosine function;

[0063] Through the voltage reference value v aref ,v bref ,v cref Calculate the voltage reference value v in the dq domain dref and v qref Voltage v dref and v qref for:

[0064]

[0065] In the formula, sin() is the sine function;

[0066] voltage v dref and v qref With voltage v d With v q The difference is calculated separately, by analyzing the voltage difference (v) dref -v d ) and (v qref -v q Perform PI calculations to obtain the control current i. dv and i qv Current i dv and i qv for:

[0067]

[0068] In the formula, G v(s) is the transfer function of the voltage loop PI controller, ω n C is the rated angular frequency of the output voltage of the energy storage converter. f This represents the filter capacitor value of the LC filter;

[0069] Acquire current i on nonlinear load na i nb i nc , will current i na i nb i nc The current i is obtained by performing an abc / dq transformation. dn with i qn Current i dn with i qn for:

[0070]

[0071] The rated current I under the dq axis is obtained from the rated active power P0 and rated reactive power Q0 of the energy storage converter. dn and I qn Rated current I dn and I qn for:

[0072]

[0073] The capacitor voltage v through the LC filter d v q With filter capacitor C f Calculate the d-axis filter capacitor current i. cd and q-axis filter capacitor current i cq for:

[0074]

[0075] Where s is the differential operator, C f It is the filter capacitor of the LC filter, v d and v q It is v a ,v b ,v c Voltage in the dq coordinate system;

[0076] According to the current I dn i dn i cd i dv The current loop command i of the d-axis system is calculated. dref According to the current I qn i qn i cq i qvThe current loop command i of the q-axis system is calculated. qref Current loop instruction i dref and i qref for:

[0077]

[0078] Current i dref and i qref With current i d with i q By taking the difference between the currents (i) dref -i d ) and (i qref -i q The control voltage e is obtained by performing PI calculation. d and e q Voltage e d and e q for:

[0079]

[0080] In the formula, G i (s) is the transfer function of the current loop PI controller, L f This represents the filter inductance value of the LC filter.

[0081] Through voltage e d and e q Calculate the internal voltage signal e a ,e b ,e c Internal voltage signal e a ,e b ,e c for:

[0082]

[0083] Through internal voltage signal e a ,e b ,e c Calculate the modulated signal s a =e a / (V dc / 2), s b =e b / (V dc / 2), s c =e c / (V dc / 2), V dc The DC-side voltage of the energy storage converter is determined by the modulation signal s. a ,s b ,s c PWM modulation is used to control the on and off of the switching transistors of the energy storage converter;

[0084] The voltage v is obtained by using the sequence impedance modeling method. d ,v q and current i d i q The frequency domain expression is:

[0085]

[0086]

[0087] In the formula, e is the natural constant, j is the imaginary unit, and ω p ω1 is the angular frequency of the disturbance voltage of the energy storage converter, ω1 is the angular frequency of the fundamental voltage of the energy storage converter, and δ is the angular frequency of the disturbance voltage of the energy storage converter. p1 β1 is the initial phase angle of the energy storage converter output voltage in the dq coordinate system, and α is the initial phase angle of the energy storage converter output voltage in the dq coordinate system. p1 It is the phase angle of the nonlinear load current, V p1 It is the rated amplitude of the output voltage of the energy storage converter, I p1 It is the rated amplitude of the nonlinear load current;

[0088] pass Figure 1 The circuit relationship of the energy storage converter can be obtained as follows:

[0089]

[0090] In the formula R f It is the resonant damping resistor of the LC filter;

[0091] According to equations (1) to (14), the impedance of the energy storage converter under the control strategy can be obtained:

[0092]

[0093] In the formula, Z in (s) is the analytical expression for the impedance of the energy storage converter, ω n This is the angular frequency of the rated voltage of the energy storage converter.

[0094] Figure 2 A comparison diagram of the impedance-frequency characteristics of the energy storage converter under the aforementioned control method and the droop control method is given. Figure 2 It can be seen that in the harmonic frequency band, the impedance amplitude of the energy storage converter is smaller under the control method, that is, the equivalent internal resistance of the energy storage converter is smaller, the energy storage converter is more like an ideal voltage source, and the stability of the output voltage is also stronger.

[0095] according to Figure 1 An experimental platform for a voltage stability control method and system for energy storage converters based on dSPACE was built. The experimental results are as follows: Figure 3 and Figure 4 As shown, where Figure 3 The experimental waveforms are shown under the droop control strategy. Figure 4 The image shows the experimental waveforms under the described control strategy. Figure 3 The experimental results show that, under the droop control strategy, the total voltage distortion rate of the energy storage converter is 6.38% after adding a nonlinear load, which is higher than the national standard of 5%. Figure 4 The experimental results show that, under the described control strategy, the total voltage distortion rate of the energy storage converter is 3.15% after adding a nonlinear load, which meets the national power quality requirements. Therefore, the voltage stability control method and system for the energy storage converter can effectively suppress the harmonic voltage on the AC side of the energy storage converter and improve the quality of the output power.

Claims

1. A voltage stabilization control method for an energy storage converter, characterized in that, Improving the output voltage stability of an energy storage converter under load disturbances includes the following steps: (1) Acquire the inductor current i of the LC filter a i b i c and capacitor voltage v a ,v b ,v c Power calculations are performed to obtain the instantaneous output power P and Q of the energy storage converter. Based on the instantaneous output power P and Q of the energy storage converter, the amplitude V and frequency f of the voltage reference value are calculated using voltage frequency droop control. The three-phase voltage reference value v is then calculated using the voltage reference value amplitude V and voltage reference value frequency f. aref ,v bref ,v cref ; through voltage reference value v aref ,v bref ,v cref The voltage reference value v is obtained after abc / dq transformation. dref and v qref ; (2) Voltage v dref and v qref With voltage v a ,v b ,v c Voltage v in the dq coordinate system d With v q The difference is calculated separately, by analyzing the voltage difference (v) dref -v d ) and (v qref -v q Perform PI calculations to obtain the control current i. dv and i qv ; Collect the current i on the nonlinear load na i nb i nc , will current i na i nb i nc The current i is obtained by performing an abc / dq transformation. dn with i qn The rated current I along the dq axis is calculated using the rated active power P0 and rated reactive power Q0 of the energy storage converter. dn and I qn ; through the filter capacitor voltage v d v q With filter capacitor C f Calculate the filter capacitor current i in the dq coordinate system cd and i cq According to the current I dn i dn i cd and i dv The current loop command i of the d-axis system is calculated. dref According to the current I qn i qn i cq and i qv The current loop command i of the q-axis system is calculated. qref ; (3) Current i dref and i qref With current i a i b i c Current i in the dq coordinate system d with i q By taking the difference between the currents (i) dref -i d ) and (i qref -i q The control voltage e is obtained by performing PI calculation. d and e q ; through voltage e d and e q Calculate the internal voltage signal e a ,e b ,e c ; via internal voltage signal e a ,e b ,e c Calculate the modulated signal s a =e a / (V dc / 2), s b =e b / (V dc / 2), s c =e c / (V dc / 2), V dc The DC-side voltage of the energy storage converter is determined by the modulation signal s. a ,s b ,s c PWM modulation is used to control the on and off of the switching transistors in the energy storage converter, which can improve the stability of the output voltage of the energy storage converter. (4) The voltage v is obtained by using the sequence impedance modeling method. d ,v q and current i d i q The frequency domain expression; based on the energy storage converter circuit relationship and voltage v d ,v q and current i d i q From the frequency domain expression, the impedance Z of the energy storage converter under the control strategy can be obtained. in (s).

2. The voltage stabilization control method for an energy storage converter according to claim 1, characterized in that, In step (1), the three-phase voltage reference value v aref ,v bref ,v cref for: In the formula, V is the reference voltage amplitude generated by the droop control calculation, π is the coefficient of pi, t is the time coefficient, and cos() is the cosine function.

3. The voltage stabilization control method for an energy storage converter according to claim 1, characterized in that, In step (2), the d-axis rated current I dn and q-axis rated current I qn for: Where V0 is the output voltage amplitude, and P0 and Q0 are the rated active power and rated reactive power of the energy storage converter, respectively.

4. The voltage stabilization control method for an energy storage converter according to claim 1, characterized in that, In step (2), the d-axis filter capacitor current i cd and q-axis filter capacitor current i cq for: Where s is the differential operator, C f It is the filter capacitor of the LC filter, v d and v q It is v a ,v b ,v c Voltage in the dq coordinate system.

5. The voltage stabilization control method for an energy storage converter according to claim 1, characterized in that, In step (2), the current loop command value i dref and i qref for: Among them, i dv and i qv i is the outer loop voltage output value. dn and i qn Let i be the nonlinear load current in the dq coordinate system. dv and i qv This is the control current obtained from the outer voltage loop.

6. The voltage stabilization control method for an energy storage converter according to claim 1, characterized in that, The impedance analysis value of the energy storage converter in step (4) is: In the formula, Z in (s) is the analytical expression for the impedance of the energy storage converter, where j is the imaginary unit and ω is the impedance of the converter. p ω is the angular frequency of the disturbance voltage of the energy storage converter. n L is the rated angular frequency of the output voltage of the energy storage converter. f C is the filter inductance value of the LC filter. f R is the filter capacitor value of the LC filter. f It is the resonant damping resistor of the LC filter, G i (s) is the transfer function of the current loop PI controller, G v (s) is the transfer function of the voltage loop PI controller.

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