Flywheel energy storage system and control method thereof

Abstract

The invention relates to a flywheel energy storage system and a control method thereof, the flywheel energy storage system is electrically connected to a bus and comprises an alternating current / direct current converter, a direct current / alternating current converter, a flywheel, a high-speed permanent magnet motor and a control device, the alternating current / direct current converter is provided with a first alternating current side and a first direct current side, the first alternating current side is electrically connected to the bus, and the first direct current side is electrically connected to the bus. The connection part between the AC / DC converter and the bus forms a grid-connected point, the DC / AC converter is provided with a second AC side and a second DC side, the second DC side is electrically connected to the first DC side, the high-speed permanent magnet motor is electrically connected to the second AC side to drive the flywheel to operate, and the control device collects signals of the grid-connected point and the first AC side. And the signal is controlled and compensated to provide at least one modulation signal, and the AC / DC converter is controlled to operate according to the at least one modulation signal.

Description

Technical Field

[0001] The present disclosure relates to the field of energy storage, and in particular to a flywheel energy storage system and a control method thereof. Background Art

[0002] At present, with the discovery of environmental problems and the improvement of renewable energy technology, the global new energy power generation industry is developing rapidly. Wind energy and photovoltaics, as pollution-free and renewable energy, have huge development potential, especially for places that are difficult for power grids to reach, such as coastal islands, remote mountainous areas, grasslands, rural areas and border areas, wind energy and photovoltaics can be used as a reliable way to solve production and living energy.

[0003] High-speed flywheel energy storage systems have the advantages of high efficiency, long life and good energy utilization. They are usually used in new power systems to control the voltage of new power systems to improve the operation quality and reliability of new power systems.

[0004] In the new power system, traditional synchronous units, wind and solar energy, flexible AC and DC equipment, and electronic load terminals are interconnected through complex power networks, which will produce "machine-electric-magnetic-control" multi-time scale interactions, which in turn trigger non-industrial frequency oscillations with a frequency range of several Hz to several kHz, namely "wide-band oscillation" (WBO). The configuration of flywheel energy storage systems in new power systems can also have a certain inhibitory effect on the problem of wide-band oscillations, but the wide-band oscillation suppression technology based on flywheel energy storage systems is not yet mature and needs further research.

[0005] Therefore, it is necessary to develop a flywheel energy storage system and a control method thereof to solve the problems faced by the prior art. Summary of the invention

[0006] The purpose of the present disclosure is to provide a flywheel energy storage system and a control method thereof, using a control device to sample and monitor the grid connection point between an AC / DC converter and a bus (i.e., a first three-phase AC voltage and a second three-phase AC voltage and a three-phase AC current of an AC / DC converter), and to control and compensate the sampled signals to provide at least one modulation signal, and to control the operation of the AC / DC converter according to the at least one modulation signal, thereby suppressing broadband oscillations in a new power system.

[0007] To achieve the above-mentioned purpose, a preferred embodiment of the present disclosure is to provide a flywheel energy storage system, which is electrically connected to the bus and includes an AC / DC converter, a DC / AC converter, a flywheel, a high-speed permanent magnet motor and a control device. The AC / DC converter has a first AC side and a first DC side, and the first AC side is electrically connected to the bus, wherein the connection between the AC / DC converter and the bus constitutes a grid connection point. The DC / AC converter has a second AC side and a second DC side, wherein the second DC side is electrically connected to the first DC side. The high-speed permanent magnet motor is electrically connected to the second AC side to drive the flywheel to operate. The control device collects signals from the grid connection point and the first AC side, and controls and compensates the signals to provide at least one modulation signal, and controls the operation of the AC / DC converter according to the at least one modulation signal.

[0008] To achieve the above-mentioned purpose, another preferred embodiment of the present disclosure is to provide a control method, which is applied to a flywheel energy storage system, wherein the flywheel energy storage system is electrically connected to a bus, and the control method comprises: (a) providing an AC / DC converter, wherein the AC / DC converter is electrically connected to the bus to form a grid-connected point; (b) providing a DC / AC converter, wherein a second DC side of the DC / AC converter is electrically connected to a first DC side of the AC / DC converter; (c) providing a high-speed permanent magnet motor to drive the flywheel to operate; and (d) collecting signals from the grid-connected point and a first AC side of the AC / DC converter, and controlling and compensating the signals to provide at least one modulation signal, and controlling the operation of the AC / DC converter according to the at least one modulation signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A circuit topology diagram of a novel power system disclosed in the present invention;

[0010] Figure 2 for Figure 1 The detailed circuit topology diagram of the flywheel energy storage system of the novel power system shown;

[0011] Figure 3 for Figure 2 The signal processing schematic diagram of the phase-locked circuit of the control device of the flywheel energy storage system shown;

[0012] Figure 4 for Figure 2 A signal processing schematic diagram of a power calculation circuit of a control device of a flywheel energy storage system shown;

[0013] Figure 5 for Figure 2 A schematic diagram of a wide-frequency oscillation damping control circuit of a control device for a flywheel energy storage system shown;

[0014] Figure 6 for Figure 2A detailed circuit topology diagram of a regulating circuit of a control device of a flywheel energy storage system shown; and

[0015] Figure 7 for Figure 2 A flow chart of a control method for a flywheel energy storage system is shown.

[0016] Description of reference numerals:

[0017] 100: New power system

[0018] 1: Flywheel energy storage system

[0019] 11: AC / DC converter

[0020] 11a: First AC side

[0021] 11b: First DC side

[0022] 12: DC / AC converter

[0023] 12a: Second AC side

[0024] 12b: Second DC side

[0025] 13: High-speed permanent magnet motor

[0026] 14: Flywheel

[0027] u dc : DC voltage

[0028] i fa 、i fb 、i fc : Three-phase AC current

[0029] u pa 、u pb 、u pc : The first three-phase AC voltage

[0030] u fa 、u fb 、u fc : Second three-phase AC voltage

[0031] θ: power frequency signal phase

[0032] Δθ pf : Phase deviation value

[0033] θ pf : Change angle

[0034] Q f : Reactive power signal

[0035] P f : Active power signal

[0036] S1: First inhibition output signal

[0037] i pabc : Second inhibition output signal

[0038] u pabc : The third inhibit output signal

[0039] 2: Busbar

[0040] 21: AC line

[0041] 3. Renewable Energy

[0042] 4: AC power grid

[0043] 9: Control device

[0044] 91: Signal acquisition circuit

[0045] 92: Phase-locked circuit

[0046] 93: Power calculation circuit

[0047] 94: Broadband Oscillation Damping Control Circuit

[0048] 941: Filter unit

[0049] 942: Proportional Phase Shifter

[0050] 943: Limiting unit

[0051] 95: Regulation circuit

[0052] 951: First coordinate transformation unit

[0053] 952: Second coordinate transformation unit

[0054] 953: First Calculator

[0055] 954: DC voltage regulator

[0056] 955: Second Calculator

[0057] 956: d-axis current regulator

[0058] 957: Third Calculator

[0059] 958: The Fourth Calculator

[0060] 959: Power Regulator

[0061] 960: Fifth Calculator

[0062] 961: q-axis current regulator

[0063] 962: Sixth Calculator

[0064] 963: Third coordinate transformation unit

[0065] 97: Driving circuit

[0066] i fα 、i fβ : Current in two-phase stationary coordinate system

[0067] u fα 、u fβ : Voltage in two-phase stationary coordinate system

[0068] i fq : q-axis current feedback value

[0069] i fd : d-axis current feedback value

[0070] u fq : q-axis voltage feedback value

[0071] u fd : d-axis voltage feedback value

[0072] u dc * : DC voltage given value

[0073] i d * : The first d-axis current given value

[0074] i d_add * : Second d-axis current regulation signal

[0075] u d_add * : Second d-axis voltage regulation signal

[0076] u d * : The first d-axis voltage regulation signal

[0077] Q f * : Reactive power given value

[0078] i q * : The first q-axis current given value

[0079] i q_add * : Second q-axis current given value

[0080] u q_add * : Second q-axis voltage regulation signal

[0081] u q* : The first q-axis voltage regulation signal

[0082] u α * : Modulation signal

[0083] u β * : Modulation signal

[0084] M1: The first compensation parameter

[0085] M2: Second compensation parameter

[0086] P: Grid connection point DETAILED DESCRIPTION

[0087] Some typical embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure can have various changes in different aspects without departing from the scope of the present disclosure, and the descriptions and drawings therein are essentially used for illustration rather than for limiting the present disclosure.

[0088] See also Figure 1 and Figure 2 ,in Figure 1 is a circuit topology diagram of the novel power system disclosed in the present invention, Figure 2 for Figure 1 The detailed circuit topology diagram of the flywheel energy storage system of the new power system is shown in FIG. Figure 1 As shown, the flywheel energy storage system 1 and the renewable energy system 3 of the present disclosure are electrically connected to the bus 2, respectively, and the AC power grid 4 is electrically connected to the bus 2 via the AC line 21, wherein the flywheel energy storage system 1, the bus 2, the renewable energy system 3 and the AC power grid 4 together constitute a new power system 100. The renewable energy system 3 may be, but is not limited to, an offshore wind farm and / or a photovoltaic power generation system. The flywheel energy storage system 1 can receive the electric energy provided by the bus 2, and convert the received electric energy into the kinetic energy of the motor rotor for storage. At this time, the electric energy of the bus 2 comes from the renewable energy 3 and / or the AC power grid 4. The flywheel energy storage system 1 can also convert the stored motor rotor kinetic energy into electric energy and provide it to the bus 2. At this time, the electric energy of the bus 2 comes from the renewable energy 3 and / or the flywheel energy storage system 1.

[0089] like Figure 2As shown, the flywheel energy storage system 1 includes an AC / DC converter 11, a DC / AC converter 12, a high-speed permanent magnet motor 13, a flywheel 14 and a control device 9. The AC / DC converter 11 has a first AC side 11a and a first DC side 11b, the first AC side 11a is electrically connected to the bus 2, and the connection between the AC / DC converter 11 and the bus 2 constitutes a grid connection point P. The DC / AC converter 12 has a second AC side 12a and a second DC side 12b, the second DC side 12b is electrically connected to the first DC side 11b of the AC / DC converter 11, and the second AC side 12a is electrically connected to the high-speed permanent magnet motor 13. In one embodiment, the AC / DC converter 11 converts a first AC voltage (for example, a 35KV medium voltage AC voltage) provided by the bus 2 into a DC voltage u dc (e.g. 380V low voltage DC voltage), the DC / AC converter 12 converts the DC voltage u provided by the AC / DC converter 11 dc Converted into a second AC voltage to provide a suitable working voltage for the high-speed permanent magnet motor 13, and the high-speed permanent magnet motor 13 drives the flywheel 14 to operate according to the second AC voltage provided by the DC / AC converter 12. The AC / DC device (AC, DC, AC conversion device) composed of the AC / DC converter 11 and the DC / AC converter 12 is connected to the bus 2, so that the flywheel energy storage system 1 disclosed in the present invention can achieve the advantages of centralized and flexible configuration. In another embodiment, the high-speed permanent magnet motor 13 converts the electric energy provided by the running flywheel 14 into a second AC voltage to transmit it to the DC / AC converter 12, and the DC / AC converter 12 converts the received second AC voltage into a DC voltage u dc , the AC / DC converter 11 receives a DC voltage u dc And converted into a first AC voltage and provided to bus 2.

[0090] The control device 9 can be, but is not limited to, a fully digital high-performance controller, which executes algorithms such as signal processing, loop control, space vector pulse width modulation (SVPWM) or sinusoidal pulse width modulation (SPWM), generates a switching signal, and drives the switch operation of the AC / DC converter 11. The control device 9 is configured to: form multiple control loops; generate multiple suppression output signals according to the voltage signal, current signal and power signal of the first AC side 11a of the AC / DC converter 11; and superimpose multiple suppression output signals in the corresponding control loop. The flywheel energy storage system 1 collects the grid voltage (the voltage of the bus 2) and the voltage and current of the first AC side 11a, controls and compensates the sampled signal to provide a modulation signal, and controls the switch operation in the AC / DC converter 11 according to the modulation signal, providing positive damping for the new power system 100 to absorb the oscillating power and suppress the non-power frequency oscillation in the new power system 100.

[0091] The structure and control method of the control device 9 will be further described below. Figure 2 In this embodiment, the control device 9 includes a signal acquisition circuit 91, a phase-locked circuit 92, a power calculation circuit 93, a broadband oscillation damping control circuit 94, a regulating circuit 95 and a driving circuit 97.

[0092] The signal acquisition circuit 91 is electrically connected to the AC / DC converter 11 and the bus 2 to sample the first three-phase AC voltage u of the bus 2. pa 、u pb 、u pc , a second three-phase AC voltage u of the first AC side 11a of the AC / DC converter 11 fa 、u fb 、u fc , three-phase alternating current i fa 、i fb 、i fc and the DC voltage u of the first DC side 11b of the AC / DC converter 11 dc .

[0093] The phase-locked circuit 92 receives the first three-phase AC voltage u of the bus 2 sampled by the signal acquisition circuit 91. pa 、u pb 、u pc , in order to track the phase information of the grid connection point P of the AC / DC converter 11. Figure 3 As shown, Figure 3 for Figure 2 The schematic diagram of the phase-locked circuit of the control device of the flywheel energy storage system shown in FIG. 1 shows that when the flywheel energy storage system 1 oscillates at a non-power frequency synchronous oscillation, the phase-locked circuit 92 separates the first three-phase AC voltage u of the bus 2. pa 、u pb 、u pc The power frequency voltage signal and the non-power frequency voltage signal in the power frequency voltage signal are phase-locked to obtain the power frequency signal phase θ, and the phase deviation value Δθ under the non-power frequency disturbance is further calculated according to the non-power frequency voltage signal. pf .

[0094] In one embodiment, the phase-locked circuit 92 further includes a phase detector, which can be but is not limited to a multiplier, for identifying the phase of the non-industrial frequency voltage signal. The phase detector inputs any two sinusoidal signals V1 and V2 in the non-industrial frequency voltage signal into the phase detector, wherein the expressions of the sinusoidal signals V1 and V2 refer to equation (1).

[0095]

[0096] Please refer to equation (2) for the transformation formula of the phase detector performing the product and difference transformation.

[0097]

[0098] Among them, V 1m 、V 2m are the maximum peak values ​​of the corresponding sinusoidal signals, ω1 and ω2 are the angular frequencies of the corresponding sinusoidal signals, t is the time, are the initial phase angles of the corresponding sinusoidal signals, V × The phase detector further uses the frequency difference (ω1-ω2) of the two sinusoidal signals in the above equation (2) to obtain the phase deviation value Δθ pf .

[0099] The phase-locked circuit 92 is also configured to convert the first three-phase AC voltage u of the bus 2 pa 、u pb 、u pc The power frequency voltage signal and the non-power frequency voltage signal synchronous component in the dq coordinate system are converted. Considering the power frequency phase tracking, based on the power frequency signal phase θ, the phase deviation value Δθ obtained by combining the non-power frequency phase locking is pf As the transformation angle θ of the dq coordinate transformation pf , and further perform dq coordinate transformation.

[0100] The power calculation circuit 93 is electrically connected to the signal acquisition circuit 91 and receives the second three-phase AC voltage u provided by the signal acquisition circuit 91. fa 、u fb 、u fc And the three-phase AC current i fa 、i fb 、i fc , and according to the second three-phase AC voltage u fa 、u fb 、u fc And the three-phase AC current i fa 、i fb 、i fc Perform power calculations. Figure 4 As shown, Figure 4 for Figure 2 The schematic diagram of the power calculation circuit of the control device of the flywheel energy storage system shown in FIG. 9 is a schematic diagram of the power calculation circuit of the control device of the flywheel energy storage system shown in FIG. fa 、u fb 、u fc And the three-phase AC current i fa 、i fb 、i fc Perform power calculation to obtain reactive power signal Q f And the active power signal P f .

[0101] The broadband oscillation damping control circuit 94 is used to change the damping of the flywheel energy storage system 1 to provide positive damping for the overall power generation system, and can be regarded as a controllable impedance. The broadband oscillation damping control circuit 94 is electrically connected to the signal acquisition circuit 91 and the power calculation circuit 93, and receives the reactive power signal Q provided by the power calculation circuit 93. f , active power signal P f and the second three-phase AC voltage u provided by the signal acquisition circuit 91 fa 、u fb 、u fc And the three-phase AC current i fa 、i fb 、i fc , and select one or more signals from the above signals, process the selected signals to obtain one or more suppressed output signals, wherein the selected signals are processed in a manner including filtering, proportional phase shifting and / or limiting.

[0102] In one embodiment, the broadband oscillation damping control circuit 94 includes a plurality of processing steps, see Figure 5 And cooperate Figure 1 and Figure 2 ,in Figure 5 for Figure 2 Schematic diagram of a broadband oscillation damping control circuit of a control device of a flywheel energy storage system shown in FIG. As shown in the figure, the broadband oscillation damping control circuit 94 includes at least one filtering unit 941, at least one proportional phase shifting unit 942 and at least one amplitude limiting unit 943, for example, three filtering units 941, three proportional phase shifting units 942 and three amplitude limiting units 943. Each filtering unit 941 may be, but is not limited to, a composite filter composed of a bandpass filter and a bandstop filter, wherein the first filtering unit 941 is for the reactive power signal Q f Or active power signal P f Filtering is performed to remove the reactive power signal Q f Or active power signal P f The second filtering unit 941 is used for the second three-phase AC voltage u fa 、u fb 、u fc Filter to remove the second three-phase AC voltage u fa 、u fb 、u fc The non-industrial frequency oscillation frequency, the third filter unit 941 for the three-phase AC current i fa 、i fb 、i fc Filter to remove the three-phase AC current i fa 、i fb 、i fcThe non-industrial frequency oscillation frequency. In the above filtering link, the band-stop filter can filter out the frequency that does not require phase compensation, and the band-pass filter can make the frequency of phase compensation more accurate.

[0103] In one embodiment, the transfer function of the bandpass filter of each filtering unit 941 may be as shown in equation (3), and the transfer function of the bandstop filter of each filtering unit 941 may be as shown in equation (4),

[0104]

[0105] Among them G BR is the gain of the band-stop filter, ξ BP is the damping ratio of the bandpass filter, ξ BR is the damping ratio of the band-stop filter, ω BP is the characteristic frequency of the bandpass filter, ω BR is the characteristic frequency of the band-stop filter.

[0106] Each proportional phase shift unit 942 receives the filtered signal provided by the corresponding filter unit 941 to proportionally amplify and phase adjust the signal of a specific oscillation frequency (for example, phase lead or lag compensation) to achieve damping suppression of the oscillation frequency and suppress the non-industrial frequency oscillation AC component to stabilize the output waveform and achieve smooth operation of the overall system. The first proportional phase shift unit 942 receives the filtered reactive power signal Q provided by the first filter unit 941 f Or active power signal P f , to perform proportional amplification and phase adjustment, the second proportional phase shift unit 942 receives the filtered three-phase AC voltage provided by the second filtering unit 941, to perform proportional amplification and phase adjustment, and the third proportional phase shift unit 942 receives the filtered three-phase AC current provided by the third filtering unit 941, to perform proportional amplification and phase adjustment. In one embodiment, each proportional phase shift unit 942 uses a transfer function to perform phase adjustment, wherein the transfer function of the proportional phase shift unit 942 can be shown as formula (5),

[0107]

[0108] Wherein, K is the proportional coefficient of the proportional phase shift unit 942, n is a positive integer, representing that it is n phase shift links connected in series, for example, three phase shift links in this embodiment are connected in series, and T1 and T2 are time constants. According to the above description, the relationship between the input signal and the suppressed output signal of the wide-band oscillation damping control circuit 94 can present the impedance relationship it represents. The flywheel energy storage system 1 disclosed in the present invention suppresses the phase fluctuation of the AC signal caused by the frequency oscillation through the wide-band oscillation damping control circuit 94, and provides phase compensation at the same time.

[0109] Each limiting unit 943 has a preset limiting value to limit the adjusted signal provided by the corresponding proportional phase shift unit 942 and output a corresponding suppression output signal. The first limiting unit 943 limits the power signal adjusted by the first proportional phase shift unit 942 and outputs a first suppression output signal S1, and the second limiting unit 943 limits the three-phase AC voltage adjusted by the second proportional phase shift unit 942 and outputs a second suppression output signal i pabc The third limiting unit 943 limits the three-phase AC current adjusted by the third proportional phase shifting unit 942 and outputs a third suppression output signal u pabc The first suppression output signal S1 may be a power signal, and the second suppression output signal may be a current signal and is indicated as i pabc , when the second inhibition output signal i pabc After coordinate transformation, the second suppression output signal i can be obtained. pabc The d-axis component i in the dq coordinate system pd and the q-axis component i pq The third suppression output signal may be a voltage signal and is denoted as u pabc , for the third suppression output signal u pabc Perform coordinate transformation to obtain the third suppression output signal u pabc The d-axis component u in the dq coordinate system pd and the q-axis component u pq .

[0110] The regulating circuit 95 has a plurality of regulating signals, is electrically connected to the broadband oscillation damping control circuit 94, receives one or more suppression output signals, and superimposes one or more suppression output signals on one or more regulating signals to obtain a modulation signal, wherein the regulating signal may be, but is not limited to, the first d-axis current given value i d * 、The first q-axis current given value i q * , the first q-axis voltage regulation signal u q * and / or the first d-axis voltage regulation signal u d * In this embodiment, the regulating circuit 95 is electrically connected to the broadband oscillation damping control circuit 94 to receive the first suppression output signal S1 and the second suppression output signal i provided by the broadband oscillation damping control circuit 94. pabc And the third suppression output signal u pabc .

[0111] The regulating circuit 95 is also electrically connected to the signal acquisition circuit 91 to receive the DC voltage u of the first DC side 11b of the AC / DC converter 11 sampled by the signal acquisition circuit 91. dcand the three-phase AC current i of the first AC side 11a of the AC / DC converter 11 fa 、i fb 、i fc And the second three-phase AC voltage u fa 、u fb 、u fc The regulating circuit 95 is also electrically connected to the phase-locked circuit 92 to receive the phase θ and phase deviation Δθ of the power frequency signal obtained by the phase-locked circuit 92. pf As the transformation angle θ of the dq coordinate transformation pf The regulating circuit 95 is also electrically connected to the power calculating circuit 93 to receive the reactive power signal Q f The regulating circuit 95 also receives or generates a DC voltage reference value u of the first DC side 11b of the AC / DC converter 11. dc * And reactive power signal given value Q f * For example, the regulating circuit is electrically connected to an upper controller to receive a given DC voltage value u of the first DC side 11b of the AC / DC converter 11 provided by the upper controller. dc * And reactive power signal given value Q f * .

[0112] The detailed circuit topology of the regulating circuit 95 will be further described below. Figure 6 And cooperate Figure 1 and Figure 2 ,in Figure 6 for Figure 2 Detailed circuit topology diagram of the regulating circuit of the control device of the flywheel energy storage system shown in the figure. As shown in the figure, the regulating circuit 95 includes a first coordinate transformation unit 951, a second coordinate transformation unit 952, a first calculator 953, a DC voltage regulator 954, a second calculator 955, a d-axis current regulator 956, a third calculator 957, a fourth calculator 958, a power regulator 959, a fifth calculator 960, a q-axis current regulator 961, a sixth calculator 962 and a third coordinate transformation unit 963.

[0113] The first coordinate transformation unit 951 transforms the three-phase alternating current i fa 、i fb 、i fc , the second three-phase AC voltage u fa 、u fb 、u fc Converted into the current i in the two-phase stationary coordinate system respectively fα 、i fβ and voltage u fα 、u fβThe second coordinate transformation unit 952 transforms the phase θ and phase deviation Δθ of the power frequency signal provided by the phase-locked circuit 92 into pf As the transformation angle θ pf , the current i in the two-phase stationary coordinate system fα 、i fβ and voltage u fα 、u fβ Converted into the q-axis current feedback value i in the two-phase rotating coordinate system respectively fq , d-axis current feedback value i fd , q-axis voltage feedback value u fq And d-axis voltage feedback value u fd It should be noted that the first coordinate transformation unit 951 and the second coordinate transformation unit 952 can be implemented by a single coordinate transformation unit, directly transforming the three-phase alternating current i fa 、i fb 、i fc , the second three-phase AC voltage u fa 、u fb 、u fc Converted into the q-axis current feedback value i in the two-phase rotating coordinate system respectively fq , d-axis current feedback value i fd And the q-axis voltage feedback value u fq , d-axis voltage feedback value u fd .

[0114] The first calculator 953 receives a preset DC voltage given value u dc * , where the DC voltage given value u dc * The first calculator 951 further receives the DC voltage u dc , and obtain the DC voltage given value u dc * With DC voltage u dc The DC voltage regulator 954 is electrically connected to the first calculator 953 and receives a DC voltage given value u dc * With DC voltage u dc The difference between the two is adjusted to obtain the first d-axis current given value i d * The DC voltage regulator 954 may be a PR regulator or a PI regulator. When the DC voltage regulator 954 is a PR regulator, its transfer function may be as shown in equation (6). When the DC voltage regulator 954 is a PI regulator, its transfer function may be as shown in equation (7).

[0115]

[0116] The second calculator 955 receives the first d-axis current given value i d * And d-axis current feedback value i fd , and obtain the first d-axis current given value i d * And d-axis current feedback value i fd The second calculator 955 further receives the second suppression output signal i pabc The d-axis component i in the dq coordinate system pd , and the d-axis component i pd Superimposed on the difference (also superimposed on the first d-axis current given value i d * ) to obtain the second d-axis current regulation signal i d_add * , whose calculation formula is shown in (8). By pabc The d-axis component i pd Superimposed on the first d-axis current given value i d * And d-axis current feedback value i fd The difference between them is used to superimpose the damping control on the d-axis current control loop.

[0117]

[0118] The d-axis current regulator 956 adjusts the second d-axis current signal i d_add * Adjust to obtain the first d-axis voltage adjustment signal u d * The third calculator 957 receives the first d-axis voltage adjustment signal u d * And the first compensation parameter M1 (i.e. ), and obtain the first d-axis voltage adjustment signal u d * And the first compensation parameter M1 (i.e. ), and the third calculator 957 further receives the third suppression output signal u pabc The d-axis component u in the dq coordinate system pd , and the d-axis component u pd Superimposed on the sum value (also superimposed on the first d-axis voltage regulation signal u d * ) to obtain the second d-axis voltage regulation signal u d_add * The third calculator 957 converts the third suppressed output signal u pabc The d-axis component u pd Superimposed on the first d-axis voltage regulation signal ud * And the first compensation parameter M1 (i.e. ) to realize the superposition of damping control on the first d-axis voltage regulation signal u d * . Among them ω e is the electrical angular velocity, L fd is the inductance L f The d-axis component of It is the permanent magnet flux of the high-speed permanent magnet motor 13.

[0119] The fourth calculator 958 receives a preset reactive power given value Q f * , where the reactive power given value Q f * The fourth calculator 958 receives the reactive power signal Q f , and obtain the reactive power given value Q f * and reactive power signal Q f The fourth calculator 958 further receives the first suppression output signal S1 and superimposes the first suppression output signal S1 on the difference (also superimposed on the reactive power given value Q f * The power regulator 959 is electrically connected to the fourth calculator 958, receives the superimposed reactive power difference, and adjusts the superimposed reactive power difference to obtain the first q-axis current given value i q * The power regulator 959 may be a PR regulator or a PI regulator.

[0120] The fifth calculator 960 receives the first q-axis current given value i q * And q-axis current feedback value i fq , and obtain the first q-axis current given value i q * And q-axis current feedback value i fq The fifth calculator 960 further receives the second suppression output signal i pabc The q-axis component i in the dq coordinate system pq , and the q-axis component i pq Superimposed on the difference (also superimposed on the first q-axis current given value i q * ) to obtain the second q-axis current given value i q_add * , whose calculation formula is shown in (9). By pabc The q-axis component ipq Superimposed on the first q-axis current given value i q * And q-axis current feedback value i fq The difference between them is used to superimpose damping control on the q-axis current control loop.

[0121]

[0122] The q-axis current regulator 961 sets a second q-axis current given value i q_add * Adjust to obtain the first q-axis voltage adjustment signal u q * The sixth calculator 962 receives the first q-axis voltage adjustment signal u q * and the second compensation parameter M2 (i.e. ω e (L fq i fq )) and obtain the first q-axis voltage regulation signal u q * and the second compensation parameter M2 (i.e. ω e (L fq i fq )) and the sixth calculator 961 further receives the third suppression output signal u pabc The q-axis component u in the dq coordinate system pq , and the q-axis component u pq Superimposed on the sum value (also superimposed on the first q-axis voltage regulation signal u q * ) to obtain the second q-axis voltage regulation signal u q_add * The sixth calculator 962 converts the third suppression output signal u pabc The q-axis component u pq Superimposed on the first q-axis voltage regulation signal u q * and the second compensation parameter M2 (i.e. ω e (L fq i fq )) to realize the superposition of damping control on the first q-axis voltage regulation signal u q * The third coordinate transformation unit 963 transforms the second d-axis voltage adjustment signal u in the two-phase rotating coordinate system into d_add * and the second q-axis voltage regulation signal u q_add * Converted into the modulation signal u in the two-phase stationary coordinate system α * and u β *. Where L fq is the inductance L f The q-axis component of .

[0123] The driving circuit 97 is electrically connected to the regulating circuit 95 to receive the modulation signal u α * and u β * , and according to the modulation signal u α * and u β * The control signal is obtained to control the switch operation of the AC / DC converter 11. The drive circuit 97 can be, for example but not limited to, modulating and generating the control signal through SPWM (Sinusoidal PWM) or SVPWM (Space Vector PWM) technology.

[0124] On the basis of the original signal, the signal obtained by the wide-band oscillation suppression link is added, and the difference between the signals is further reduced by superposition of multiple signals to obtain a modulated signal. After decoupling control, the control signal is output through PWM modulation to control the AC / DC converter 11 to operate stably.

[0125] In some embodiments, the control device 9 is implemented by a control chip, for example, the control device 9 is implemented by a DSP control chip, and the DSP control chip is responsible for completing signal sampling, signal processing calculation and loop control, etc. The driving circuit 97 is implemented by a control chip (for example, an FPGA control chip).

[0126] The present disclosure is not limited to this, and the control device 9 and / or the driving circuit 97 may also be implemented in other ways, such as by building an analog circuit. That is, the controller and / or the driving circuit of the present disclosure includes one or more of the control chip, operation program, processor, analog circuit and other structures that can realize the above functions.

[0127] See also Figure 7 , which is Figure 2 Flowchart of the control method of the flywheel energy storage system shown. First, execute step K1 to set the AC / DC converter 11, wherein the AC / DC converter 11 is electrically connected to the bus 2 to form a grid-connected point P. Next, execute step K2 to set the DC / AC converter 12, wherein the second DC side 12b of the DC / AC converter 12 is electrically connected to the first DC side 11b of the AC / DC converter 11. Next, execute step K3 to set a high-speed permanent magnet motor 13 to drive the flywheel 14 to operate. Next, execute step K4 to collect signals from the grid-connected point P and the first AC side 11a of the AC / DC converter 11, and control and compensate the signals to provide at least one modulation signal, and control the operation of the AC / DC converter 11 according to the at least one modulation signal.

[0128] In summary, the flywheel energy storage system disclosed in the present invention utilizes a control device to sample and monitor the grid connection point between the AC / DC converter and the bus (i.e., the first three-phase AC voltage and the second three-phase AC voltage and three-phase AC current of the AC / DC converter), and controls and compensates the sampled signal to provide at least one modulation signal, and controls the operation of the AC / DC converter according to at least one modulation signal, thereby suppressing the broadband oscillation in the new power system. The AC / DC converter and the DC / AC converter of the flywheel energy storage system disclosed in the present invention together form an AC / DC device connected to the AC side of the bus of the power grid, so that the flywheel energy storage system disclosed in the present invention can achieve the advantages of centralized and flexible configuration. The flywheel energy storage system disclosed in the present invention further utilizes the proportional phase shift unit of the control device to receive the filtered signal provided by the corresponding filter unit to proportionally amplify and phase adjust the signal of a specific oscillation frequency, thereby achieving damping suppression of the oscillation frequency, suppressing the non-industrial frequency oscillation AC component, so as to stabilize the output waveform and achieve smooth operation of the overall system.

Claims

1. A flywheel energy storage system, electrically connected to a bus bar, and comprising: an AC / DC converter having a first AC side and a first DC side, the first AC side being electrically connected to the bus, wherein the connection between the AC / DC converter and the bus constitutes a grid connection point; A DC / AC converter having a second AC side and a second DC side, wherein the second DC side is electrically connected to the first DC side; a flywheel; a high-speed permanent magnet motor, electrically connected to the second AC side, to drive the flywheel to operate; and A control device collects signals from the grid-connected point and the first AC side, controls and compensates the signals to provide at least one modulation signal, and controls the operation of the AC / DC converter according to the at least one modulation signal.

2. The flywheel energy storage system of claim 1 , wherein the control device comprises a signal acquisition circuit and a phase-locked circuit, sampling a first three-phase AC voltage of the bus, a second three-phase AC voltage of the first AC side of the AC / DC converter, a three-phase AC current and a DC voltage of the first DC side of the AC / DC converter, the phase-locked circuit receives the first three-phase AC voltage of the bus sampled by the signal acquisition circuit to track the phase information of the grid connection point, wherein when the flywheel energy storage system undergoes non-power frequency synchronous oscillation, the phase-locked circuit separates a power frequency voltage signal and a non-power frequency voltage signal in the first three-phase AC voltage of the bus, phase-locks the power frequency voltage signal to obtain a power frequency signal phase, and calculates a phase deviation value under non-power frequency disturbance according to the non-power frequency voltage signal.

3. The flywheel energy storage system as claimed in claim 2, wherein the phase-locked circuit is further configured to combine the phase of the power frequency signal with the phase deviation value to obtain a transformation angle as a dq coordinate transformation.

4. The flywheel energy storage system as claimed in claim 3, wherein the control device comprises a power calculation circuit, which receives and performs power calculation on the second three-phase AC voltage and the three-phase AC current provided by the signal acquisition circuit to obtain a reactive power signal and an active power signal.

5. A flywheel energy storage system as claimed in claim 4, wherein the control device comprises a broadband oscillation damping control circuit, which receives and processes the reactive power signal, the active power signal, the second three-phase AC voltage and / or the three-phase AC current provided by the power calculation circuit to obtain at least one suppression output signal.

6. A flywheel energy storage system as described in claim 5, wherein the broadband oscillation damping control circuit comprises at least one filtering unit, at least one proportional phase shifting unit and at least one limiting unit, the at least one filtering unit filters the reactive power signal, the active power signal, the second three-phase AC voltage and / or the three-phase AC current to filter out a non-industrial frequency oscillation frequency, the at least one proportional phase shifting unit proportionally amplifies and phase adjusts the signal filtered by the at least one filtering unit, and the at least one limiting unit limits the adjusted signal and outputs the at least one suppressed output signal.

7. A flywheel energy storage system as claimed in claim 5, wherein the control device comprises a regulating circuit and a driving circuit, the regulating circuit having the at least one signal, receiving the at least one suppression output signal, and superimposing the at least one suppression output signal on the at least one signal to obtain the at least one modulation signal, and the driving circuit controls the operation of the AC / DC converter according to the at least one modulation signal.

8. The flywheel energy storage system as claimed in claim 7, wherein the control device comprises a regulating circuit, the regulating circuit comprising: a first coordinate transformation unit, which transforms the three-phase AC current and the second three-phase AC voltage into a q-axis current feedback value, a d-axis current feedback value, a q-axis voltage feedback value, and a d-axis voltage feedback value according to the phase of the power frequency signal and the phase deviation value as the transformation angle; a first calculator, receiving the DC voltage and a preset DC voltage given value, and obtaining a difference between the DC voltage given value and the DC voltage; A DC voltage regulator receives and adjusts the difference between the DC voltage given value and the DC voltage to obtain a first d-axis current given value; a second calculator, receiving the first d-axis current given value, the d-axis current feedback value, and a d-axis component of a second suppressed output signal in the at least one suppressed output signal, and obtaining a difference between the first d-axis current given value and the d-axis current feedback value, and superimposing the d-axis component of the second suppressed output signal on the difference between the first d-axis current given value and the d-axis current feedback value to obtain a second d-axis current adjustment signal in the at least one signal; a d-axis current regulator, regulating the second d-axis current regulation signal to obtain a first d-axis voltage regulation signal in the at least one signal; as well as A third calculator receives the first d-axis voltage adjustment signal, a first compensation parameter and a d-axis component of a third suppressed output signal of the at least one suppressed output signal, and superimposes the d-axis component of the third suppressed output signal on the sum of the first d-axis voltage adjustment signal and the first compensation parameter.

9. The flywheel energy storage system as claimed in claim 8, wherein the control device comprises a regulating circuit, the regulating circuit comprising: a fourth calculator, receiving the reactive power signal, a preset reactive power given value, and a first suppressed output signal of the at least one suppressed output signal, obtaining a difference between the reactive power given value and the reactive power signal, and superimposing the first suppressed output signal on the difference between the reactive power given value and the reactive power signal to obtain a reactive power difference; a power regulator, receiving and regulating the reactive power difference to obtain a first q-axis current given value; a fifth calculator, receiving the first q-axis current given value, the q-axis current feedback value and a q-axis component of the second suppression output signal, obtaining a difference between the first q-axis current given value and the q-axis current feedback value, and superimposing the q-axis component on the difference between the first q-axis current given value and the q-axis current feedback value to obtain a second q-axis current given value; a q-axis current regulator, which regulates the second q-axis current given value to obtain a first q-axis voltage regulation signal in the at least one signal; a sixth calculator, receiving the first q-axis voltage adjustment signal, a second compensation parameter, and a q-axis component in the third suppression output signal, obtaining a difference between the first q-axis voltage adjustment signal and the second compensation parameter, and superimposing the q-axis component on the difference between the first q-axis voltage adjustment signal and the second compensation parameter; and A third coordinate transformation unit transforms the second d-axis voltage adjustment signal and the second q-axis adjustment signal into the at least one modulation signal.

10. The flywheel energy storage system as claimed in claim 5, wherein the control device processes the reactive power signal or the active power signal to obtain a suppressed output power signal, and superimposes the suppressed output power signal in a control loop of the control device, wherein the processing includes filtering, phase shifting and limiting.

11. The flywheel energy storage system as claimed in claim 2, wherein the control device processes the second three-phase AC voltage to obtain a suppressed output voltage signal, and superimposes the suppressed output voltage signal in a control loop of the control device, wherein the processing includes filtering, phase shifting and limiting.

12. The flywheel energy storage system as claimed in claim 2, wherein the control device processes the three-phase AC current to obtain a suppressed output current signal, and superimposes the suppressed output current signal in a control loop of the control device, wherein the processing includes filtering, phase shifting and amplitude limiting.

13. A control method, applied to a flywheel energy storage system, the flywheel energy storage system is electrically connected to a bus, and the control method comprises: (a) providing an AC / DC converter, wherein the AC / DC converter is electrically connected to the bus to form a grid connection point; (b) providing a DC / AC converter, wherein a second DC side of the DC / AC converter is electrically connected to a first DC side of the AC / DC converter; (c) providing a high-speed permanent magnet motor to drive a flywheel to operate; and (d) collecting signals from the grid connection point and a first AC side of the AC / DC converter, and controlling and compensating the signals to provide at least one modulation signal, and controlling the operation of the AC / DC converter according to the at least one modulation signal.

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