A voltage and frequency stabilizing device and method for a drilling platform diesel generator system based on SVG

Abstract

The present invention proposes a voltage and frequency stabilizing device for a drilling platform diesel generator system based on SVG, wherein the power module of the voltage and frequency stabilizing device includes an H-bridge circuit and a DC side capacitor C connected in parallel therewith, and also includes an active power regulating circuit connected in parallel at both ends of the H-bridge circuit, wherein the active power regulating circuit includes a fully controlled switching device VT5 and a resistor Rb connected in series therewith. The active power consumed by Rb is adjusted by adjusting the PWM wave of the input pulse width variation of the fully controlled switching device VT5; SVG independently controls the active branch and the reactive branch, so that SVG regulates the reactive power of the power grid while ensuring that the active power of the power grid changes smoothly according to the settable inertia link in the case of a sudden change in the active power of the load, thereby stabilizing the voltage and frequency of the power grid and ensuring the stable operation of the island operation generator.

Description

Technical Field

[0001] The invention relates to the technical field of reactive power compensation, and in particular to a voltage and frequency stabilizing device and method for a drilling platform diesel power generation system based on SVG. Background Art

[0002] At present, the distribution network of offshore drilling platforms belongs to an isolated microgrid, which is usually powered by multiple diesel generators in parallel, unlike land-based equipment with multiple backup power supplies. To ensure drilling safety, the load rate of the main diesel engine is about 50%, and the load rate of the diesel generator set is about 60%, both of which are in the low efficiency area. The main diesel engine has a lot of redundant power, resulting in high fuel and maintenance costs and low work efficiency.

[0003] The main loads of the offshore drilling platform system include winches, turntables, mud pumps, top drives and other equipment. The use of a DC speed control system results in frequent sudden load changes on site, resulting in large current shocks, and the diesel generator system cannot quickly adjust the output active power, resulting in large fluctuations in the output voltage of the generator, frequency deviations, and waveform distortions. Frequent fluctuations in frequency and voltage can cause the turntable inverter to trip, the auxiliary system to stop protectively, and even motors, household appliances and logging instruments to burn out, causing huge economic losses.

[0004] In order to solve the power quality problem of diesel generator system on offshore drilling platform, it was decided to study the voltage and frequency stabilization device of diesel generator system on drilling platform based on SVG. SVG realizes independent control of active power and reactive power through active loop and reactive loop, so that SVG can adjust the reactive power of the power grid at the same time, and ensure the active power of the power grid changes smoothly according to the settable inertia link when the active power of the load changes suddenly, so as to stabilize the voltage and frequency of the power grid and ensure the stable operation of the generator in island operation. Summary of the invention

[0005] In order to solve the problems raised by the background technology, the present invention proposes a voltage and frequency stabilizing device and method for a drilling platform diesel generator system based on SVG. SVG independently controls the active branch and the reactive branch, so that SVG can regulate the reactive power of the power grid while ensuring that the active power of the power grid changes smoothly according to the settable inertia link when the active power of the load suddenly changes, thereby stabilizing the voltage and frequency of the power grid and ensuring the stable operation of the island-operated generator.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A voltage and frequency stabilizing device for a drilling platform diesel generator system based on SVG, wherein a power module of the voltage and frequency stabilizing device comprises an H-bridge circuit and a DC side capacitor C connected in parallel therewith, and also comprises an active power regulating circuit connected in parallel at both ends of the H-bridge circuit, wherein the active power regulating circuit comprises a fully controlled switching device VT5 and a resistor Rb connected in series therewith.

[0008] Furthermore, a first reverse diode is connected in parallel at both ends of the fully-controlled switching device VT5.

[0009] Furthermore, a second reverse diode is connected in parallel between the two ends of the resistor Rb.

[0010] Furthermore, the fully controlled switching device VT5 is an IGBT.

[0011] The control method of the voltage and frequency stabilizing device of the diesel generator system of the drilling platform based on SVG adjusts the active power consumed by Rb by adjusting the PWM wave with a pulse width change input by the fully controlled switching device VT5; when the PWM wave with a duty cycle of D (0≤D≤1) is input, the active power Pm consumed by a single power unit Rb is calculated as shown in Formula 1:

[0012]

[0013] The active power Ps consumed by the entire SVG system is calculated as shown in Formula 2:

[0014]

[0015] The variables in the formula have the following meanings:

[0016] V DC : DC side voltage value;

[0017] D: VT5 switch conduction duty cycle;

[0018] N: the number of SVG series stages per phase;

[0019] R b : Resistance of power unit discharge resistor Rb;

[0020] By controlling the conduction duty cycle D of the VT5 switch tube, the active power consumed by the SVG voltage and frequency stabilization device is continuously and proportionally adjusted.

[0021] The control method of the voltage and frequency stabilizing device comprises the following steps:

[0022] Step 1: SVG voltage and frequency stabilization device samples the grid voltage u in real time a grid 、u b grid 、u cgrid , grid current i a grid,i b grid,i c grid, SVG current i a svg 、i b svg 、i c svg , the simultaneous compensation and regulation of active power and reactive power are realized in a synchronous rotating coordinate system with active and reactive power decoupling;

[0023] In order to realize zero-static tracking control under linear synchronous rotating standard, the three-phase voltage at the common coupling point of the detection device system is detected, and the double dq decoupled digital phase-locking algorithm is used to realize the precise phase locking of the grid voltage, and at the same time, the frequency and phase required for synchronous rotating coordinate transformation are extracted;

[0024] Step 2: The control system of the SVG voltage and frequency stabilization device is composed of a DC voltage control loop, two fundamental wave current control loops of active d-axis and reactive q-axis, and an SVG active regulation control loop;

[0025] The PI output of the DC side voltage control loop is used as the active command component of the fundamental active current control loop and is implemented using PI control; the fundamental current control adopts dq decoupling control in a synchronous rotating coordinate system, and the DC side voltage outer loop output is used as the active current inner loop command reference value I dref , realize active power regulation;

[0026] The output of the system-level reactive power control module is used as the fundamental reactive current inner loop reference value I qref , realize the reactive power regulation of the system; the current control loop realizes the current zero-static-error tracking of the active component Id and reactive component Iq of the SVG output current in the synchronous rotating coordinate system to obtain the active component md and reactive component mq of the modulated wave voltage signal, and realizes the SPWM modulation of the power devices in the H-bridge power unit in the three-phase static coordinate system through dq / abc transformation;

[0027] Step 3: SVG active power regulation control detects the load active power P load Calculate the active power regulation branch control duty cycle D, and finally realize the control of VT5 in the active power regulation branch through PWM modulation;

[0028] The SVG control logic of VT5 in the active power regulation branch is as follows:

[0029] Step 301: Detect the load active power change P err And the active power setting threshold P set For comparison, when P set >P err And the duration is △T1, the output active power regulation command Pref =P err When P err <P set And the duration is △T2, the output active power regulation command P ref =0;

[0030] Step 302: According to the active power instruction P ref Calculate the active power regulation branch control duty cycle D, and finally realize the control of active power regulation branch VT5 through PWM modulation;

[0031] The load active power P load and load reactive power Q load The calculation is as follows:

[0032]

[0033]

[0034] Step 403: The current inner loop closed loop transfer function can be equivalent to a first-order inertia link, and its equivalent time constant is T C , T C It is related to the current inner loop PI parameters and control system delay; P mload (s) is the load active power detected by the SVG system, as shown in Formula 4, where the detection link is equivalent to the first-order inertia link, and its equivalent time constant is T2; after the current inner loop is equivalently processed, the transfer function of the grid active power and the load active power after adding active power regulation is shown in Formula 5; where, Pl oad (s) is the load active power, P grid (s) is the active power of the power grid, T1 is the set active power decay time constant;

[0035]

[0036]

[0037] Where T1 is the set active decay time constant. Usually Tc and T2 are much smaller than T1, so the above formula can be simplified as follows:

[0038]

[0039] It can be seen from the above formula that after adding SVG to adjust the active power, when the load active power suddenly changes, the grid active power can decay smoothly according to the inertia link with a time constant of T1.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. SVG independently controls the active branch and the reactive branch, so that SVG can adjust the reactive power of the grid while ensuring that the active power of the grid changes smoothly according to the settable inertia link in the case of sudden changes in the active power of the load, thereby stabilizing the voltage and frequency of the grid and ensuring the stable operation of the generator in island operation. It can compensate for the reactive power and grid harmonics of the microgrid in the island operation of the drilling platform, and at the same time, it can adjust the active power of the grid in the case of sudden changes in the load. The active power of SVG changes smoothly according to the settable inertia link, thereby stabilizing the voltage and frequency of the grid and ensuring the stable operation of the generator in island operation.

[0042] 2. The new voltage and frequency stabilization device for the diesel generator system of the drilling platform based on SVG adopts the power module cascade technology. The active command current and reactive command current of the SVG voltage and frequency stabilization device are calculated by sampling the grid voltage PT, grid current CT and SVG output HOLL current. The DC side voltage balance of the SVG voltage and frequency stabilization device is controlled by sampling the DC side voltage Udc of the SVG voltage and frequency stabilization device and sampling the SVG output HOLL current. The SVG voltage and frequency stabilization device realizes zero-static-error tracking of the current command in the synchronous rotating coordinate system through independent decoupled current closed-loop control, thereby realizing reactive power compensation of the diesel generator system of the drilling platform and smooth regulation of the active power of the grid, thereby stabilizing the voltage and frequency of the grid and ensuring the stable operation of the island-operated generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is the topological structure diagram of the SVG voltage and frequency stabilization device system;

[0044] Figure 2 This is the structure diagram of the power unit of the SVG voltage and frequency stabilization device;

[0045] Figure 3 It is the control strategy principle frame of SVG voltage and frequency stabilization device Figure 1 ;

[0046] Figure 4 It is the control strategy principle frame of SVG voltage and frequency stabilization device Figure 2 ;

[0047] Figure 5 It is the control strategy principle frame of SVG voltage and frequency stabilization device Figure 3 ;

[0048] Figure 6 It is the structure diagram of the transfer function between load active power and grid active power after adding SVG voltage and frequency stabilization device;

[0049] Figure 7 It is a specific implementation flow chart of the SVG voltage and frequency stabilization device test;

[0050] Figure 8This is a comparison chart of active regulation and reactive compensation power of SVG voltage and frequency stabilization device;

[0051] Fig. 9 This is a comparison chart of active regulation and reactive compensation current of SVG voltage and frequency stabilization device.

[0052] In the figure: 1-grid power supply 2-grid voltage sampling device PT 3-grid current sampling device CT 4-SVG voltage and frequency stabilizing device 5-SVG output current HOLL 6-SVG voltage and frequency stabilizing device controller 7-motor and other loads. DETAILED DESCRIPTION

[0053] The specific implementation modes provided by the present invention are described in detail below with reference to the accompanying drawings.

[0054] The new voltage and frequency stabilization device for the diesel generator system of the drilling platform based on SVG adopts the power module cascade technology. The active command current and reactive command current of the SVG voltage and frequency stabilization device are calculated by sampling the grid voltage PT, grid current CT and SVG output HOLL current. The DC side voltage balance of the SVG voltage and frequency stabilization device is controlled by sampling the DC side voltage Udc of the SVG voltage and frequency stabilization device and sampling the SVG output HOLL current. The SVG voltage and frequency stabilization device realizes zero-static-error tracking of the current command in the synchronous rotating coordinate system through independent decoupled current closed-loop control, thereby realizing reactive power compensation of the diesel generator system of the drilling platform and smooth regulation of the active power of the grid, thereby stabilizing the voltage and frequency of the grid and ensuring the stable operation of the island-operated generator.

[0055] like Figure 1 As shown, the scheme of the present invention includes a power supply 1, a power supply PT 2, a power supply CT 3, a SVG voltage and frequency stabilization device 4, a SVG output current HOLL 5, a SVG voltage and frequency stabilization device controller 6, and a load such as a motor 7. The system topology is shown in FIG. Figure 1As shown: the SVG voltage and frequency stabilizing device 4 is connected in parallel to the power supply 1 of the power grid system, and the SVG voltage and frequency stabilizing device is started. The SVG voltage and frequency stabilizing device controller 6 controls the DC voltage balance of the device by sampling the DC side voltage Udc of the power unit and the HOLL current output of the SVG voltage and frequency stabilizing device; the SVG voltage and frequency stabilizing device controller 6 samples the grid voltage, grid current, and the output current of the SVG voltage and frequency stabilizing device, and calculates in real time to give the active current instruction and reactive current instruction of the SVG voltage and frequency stabilizing device; at the same time, the independently decoupled current closed-loop control realizes the current instruction tracking without static error in the synchronous rotating coordinate system, thereby realizing the reactive power compensation of the drilling platform diesel generator system and the smooth regulation of the active power of the grid. The comparison test of the SVG voltage and frequency stabilizing device and the start and stop of the impact load is carried out, and the compensation and regulation effect of the SVG voltage and frequency stabilizing device on the active power and reactive power of the grid is detected by the standard power quality detection device.

[0056] like Figure 2 As shown in FIG. 1 , the power module of the SVG voltage and frequency stabilization device mainly includes the topological structure of an H-bridge circuit and an active power regulation circuit. The H-bridge circuit is formed by IGBT modules VT1-VT4 and a DC capacitor C and a voltage-equalizing resistor R connected in parallel therewith.

[0057] The active power regulation circuit of the present invention is an active power regulation circuit composed of an IGBT module VT5 and a resistor Rb, which are connected in parallel at both ends of an H-bridge circuit composed of IGBT modules VT1-VT4. VT5 inputs a PWM wave with a varying pulse width to adjust the active power consumed by Rb. When a PWM wave with a duty cycle of D (0≤D≤1) is input, the active power Pm consumed by a single power unit Rb is calculated as shown in Formula 1:

[0058]

[0059] The active power Ps consumed by the entire SVG system is calculated as shown in Formula 2:

[0060]

[0061] The variables in the formula have the following meanings:

[0062] VDC: DC side voltage value;

[0063] D: VT5 switch conduction duty cycle;

[0064] N: the number of SVG series stages per phase;

[0065] Rb: resistance value of power unit discharge resistor;

[0066] It can be seen from the above formula that by controlling the conduction duty cycle D of the VT5 switch tube, the active power consumed by the SVG voltage and frequency stabilization device can be continuously and proportionally adjusted.

[0067] The control method of the voltage and frequency stabilizing device comprises the following steps:

[0068] Step 1: Figure 3 As shown, the SVG voltage and frequency stabilization device samples the grid voltage u in real time. a grid 、u b grid 、u c grid , grid current i a grid,i b grid,i c grid, SVG current i a svg 、i b svg 、i c svg , the active power and reactive power are compensated and regulated simultaneously in the synchronous rotating coordinate system with active and reactive power decoupling; in order to realize the zero-static tracking control under the linear synchronous rotating standard, the three-phase voltage at the common coupling point of the detection device system is detected, and the double dq decoupling digital phase-locking algorithm is used to realize the precise phase locking of the grid voltage, and at the same time, the frequency and phase required for the synchronous rotating coordinate transformation are extracted;

[0069] Step 2: Figure 4 As shown, the control system of the SVG voltage and frequency stabilization device consists of a DC voltage control loop, two fundamental current control loops of active d-axis and reactive q-axis, and an SVG active regulation control loop;

[0070] The PI output of the DC side voltage control loop is used as the active command component of the fundamental active current control loop and is implemented using PI control; the fundamental current control adopts dq decoupling control in a synchronous rotating coordinate system, and the DC side voltage outer loop output is used as the active current inner loop command reference value I dref , realize active power regulation;

[0071] The output of the system-level reactive power control module is used as the fundamental reactive current inner loop reference value I qref , realize the reactive power regulation of the system; the current control loop realizes the current zero-static-error tracking of the active component Id and reactive component Iq of the SVG output current in the synchronous rotating coordinate system to obtain the active component md and reactive component mq of the modulated wave voltage signal, and realizes the SPWM modulation of the power devices in the H-bridge power unit in the three-phase static coordinate system through dq / abc transformation;

[0072] Step 3: Figure 5 As shown in the figure, SVG active power regulation control detects the load active power P load Calculate the active power regulation branch control duty cycle D, and finally realize the control of VT5 in the active power regulation branch through PWM modulation;

[0073] like Figure 5-6 As shown, the SVG control logic of VT5 in the active power regulation branch is as follows:

[0074] Step 301: Figure 5 As shown, by detecting the load active power change P err And the active power setting threshold P set For comparison, when P set >P err And the duration is △T1, the output active power regulation command P ref =P err When P err <P set And the duration is △T2, the output active power regulation command P ref =0;

[0075] Step 302: According to the active power instruction P ref Calculate the active power regulation branch control duty cycle D, and finally realize the control of active power regulation branch VT5 through PWM modulation;

[0076] The load active power P load and load reactive power Q load The calculation is as follows:

[0077]

[0078]

[0079] Step 303: Figure 5 The current inner loop closed loop transfer function shown can be equivalent to a first-order inertia link, and its equivalent time constant is T C , T C It is related to the current inner loop PI parameters and control system delay; P mload (s) is the load active power detected by the SVG system, as shown in Formula 4, where the detection link is equivalent to a first-order inertia link, and its equivalent time constant is T2; Figure 6 As shown, after the current inner loop is equivalently processed, the transfer function of the grid active power and the load active power after adding active power regulation is shown in Formula 5; where, Pl oad (s) is the load active power, P grid (s) is the active power of the power grid, T1 is the set active power decay time constant;

[0080]

[0081]

[0082] Where T1 is the set active decay time constant. Usually Tc and T2 are much smaller than T1, so the above formula can be simplified as follows:

[0083]

[0084] It can be seen from the above formula that after adding SVG to adjust the active power, when the load active power suddenly changes, the grid active power can decay smoothly according to the inertia link with a time constant of T1.

[0085] The specific implementation process of the present invention is as follows Figure 7 shown. Figure 8 It is a comparison diagram of active regulation and reactive compensation power of the SVG voltage and frequency stabilizing device of the present invention; Fig. 9 It is a comparison diagram of active regulation and reactive compensation current of the SVG voltage and frequency stabilizing device of the present invention.

[0086] In summary, the SVG voltage and frequency stabilization device can compensate for the reactive power and grid harmonics of the drilling platform's islanded microgrid. At the same time, it can adjust the active power of the grid in the event of a sudden load change. The SVG active power changes smoothly according to the settable inertia link, thereby stabilizing the grid voltage and frequency and ensuring the stable operation of the islanded generator.

[0087] The above embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the above embodiments. The methods used in the above embodiments are conventional methods unless otherwise specified.

Claims

1. A control method for a voltage and frequency stabilizing device of a diesel generator system of a drilling platform based on SVG, wherein the power module of the voltage and frequency stabilizing device comprises an H-bridge circuit and a DC side capacitor C connected in parallel therewith; and further comprises an active power regulating circuit connected in parallel to both ends of the H-bridge circuit, wherein the active power regulating circuit comprises a fully controlled switching device VT5 and a resistor Rb connected in series therewith; The control method of the voltage and frequency stabilizing device comprises the following steps: Step 1: SVG voltage and frequency stabilization device samples the grid voltage u in real time a grid 、u b grid 、u c grid , grid current i a grid 、i b grid 、i c grid , SVG current i a svg 、i b svg 、i c svg , the simultaneous compensation and regulation of active power and reactive power are realized in a synchronous rotating coordinate system with active and reactive power decoupling; In order to realize zero-static tracking control under linear synchronous rotating standard, the three-phase voltage at the common coupling point of the detection device system is detected, and the double dq decoupled digital phase-locking algorithm is used to realize the precise phase locking of the grid voltage, and at the same time, the frequency and phase required for synchronous rotating coordinate transformation are extracted; Step 2: The control system of the SVG voltage and frequency stabilization device is composed of a DC voltage control loop, two fundamental wave current control loops of active d axis and reactive q axis, and an SVG active regulation control loop; The PI output of the DC side voltage control loop is used as the active command component of the fundamental active current control loop and is implemented using PI control; Fundamental current control adopts dq decoupling control in synchronous rotating coordinate system, and the DC side voltage outer loop output is used as the active current inner loop instruction reference value I dref , realize active power regulation; The output of the system-level reactive power control module is used as the fundamental reactive current inner loop reference value I qref , realize the reactive power regulation of the system; the current control loop realizes the current zero-static-error tracking of the active component Id and reactive component Iq of the SVG output current in the synchronous rotating coordinate system to obtain the active component md and reactive component mq of the modulated wave voltage signal, and realizes the SPWM modulation of the power devices in the H-bridge power unit in the three-phase static coordinate system through dq / abc transformation; Step 3: SVG active power regulation control detects the load active power P load Calculate the active power regulation branch control duty cycle D, and finally realize the control of VT5 in the active power regulation branch through PWM modulation; The SVG control logic of VT5 in the active power regulation branch is as follows: Step 301: Detect the load active power change P err And the active power setting threshold P set For comparison, when P err >P set And the duration is △T1, the output active power regulation command P ref =P err When P err <P set And the duration is △T2, the output active power regulation command P ref =0; Step 302: According to the active power instruction P ref Calculate the active power regulation branch control duty cycle D, and finally realize the control of active power regulation branch VT5 through PWM modulation; The load active power P load and load reactive power Q load The calculation is as follows: Step 403: The current inner loop closed loop transfer function can be equivalent to a first-order inertia link, and its equivalent time constant is T C , T C It is related to the current inner loop PI parameters and control system delay; P mload (s) is the load active power detected by the SVG system, as shown in Formula 4, where the detection link is equivalent to the first-order inertia link, and its equivalent time constant is T2; after the current inner loop is equivalently processed, the transfer function of the grid active power and the load active power after adding active power regulation is shown in Formula 5; where P load (s) is the load active power, P grid (s) is the active power of the power grid, T1 is the set active power decay time constant; Where T1 is the set active decay time constant. Usually Tc and T2 are much smaller than T1, so the above formula can be simplified as follows: It can be seen from the above formula that after adding SVG to adjust the active power, when the load active power suddenly changes, the grid active power can decay smoothly according to the inertia link with a time constant of T1.

2. The control method of a voltage and frequency stabilizing device of a drilling platform diesel generator system based on SVG according to claim 1 is characterized in that: The control method of the voltage and frequency stabilizing device further includes: adjusting the active power consumed by Rb by adjusting the PWM wave with a pulse width change input by the fully controlled switching device VT5; when the PWM wave with a duty cycle of D (0≤D≤1) is input, the active power Pm consumed by a single power unit Rb is calculated as shown in Formula 1: The active power Ps consumed by the entire SVG system is calculated as shown in Formula 2: The variables in the formula have the following meanings: V DC : DC side voltage value; D: VT5 switch conduction duty cycle; N: the number of SVG series stages per phase; R b : Resistance of power unit discharge resistor Rb; By controlling the conduction duty cycle D of the VT5 switch tube, the active power consumed by the SVG voltage and frequency stabilization device is continuously and proportionally adjusted.

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