JPH0522470B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a control device for a self-excited power converter that supplies power from a DC power source such as a fuel cell to an AC power system. [Technical background of the invention] For example, as seen in thermal power plants, conventional power generation methods that convert the energy contained in fuel into electrical energy through many conversion processes have poor energy conversion efficiency. Recently, attempts have been made to put into practical use a fuel cell power generation system in which fuel is chemically changed and electrical energy is directly extracted from the flow of electrons generated during this chemical change. In this case, the power generated from the fuel cell is direct current, so it must be converted to alternating current in order to be output to the normal power system, and this direct current to alternating current converter is usually referred to as a self-excited power converter This is called an inverter). Conventionally, the phase of the inverter output voltage was controlled to control the active power supplied from the inverter to the power system, and the magnitude of the inverter output voltage was controlled to control the reactive power. [Problems with the background art] However, according to the above conventional control method,
The active power control system and the reactive power control system interfere with each other, and it takes a long time for the system to reach a steady state after a control operation is applied, resulting in the problem that stable and responsive inverter control cannot be performed. Ta. That is, now, the output voltage of the inverter is V _I , the voltage of the power grid is V _L , the phase difference between the inverter output voltage and the power grid voltage is θ, and the interconnection impedance of the power transmission line until the inverter is connected to the power grid When is Z, the active power P and reactive power Q output from the inverter are given by the following equations (1) and (2). P=V _I・V _L・sinθ/Z…(1) Q=V _I・(V _I −V _L cosθ)/Z…(2) As is clear from these equations, the active power P does not necessarily depend on the phase difference θ. It is not only a function of V I but also related to the inverter output voltage V _I . Furthermore, the reactive power Q is not necessarily a function of only the inverter output voltage _VI , but is also related to the phase difference θ. Therefore, according to the conventional control method described above, when the phase difference θ (inverter output voltage V _I ) is changed in an attempt to change the active power P (reactive power Q), not only the active power P (reactive power Q) , the reactive power Q (active power P) also changes. Therefore, if the inverter output voltage V _I (phase difference θ) is corrected according to the change in reactive power Q (active power P),
It takes a long time to change the carefully controlled active power P (reactive power Q) and to settle it into a steady state. On the other hand, in order to stabilize the power system and respond to sudden changes in the system load in the event of a system fault, or sudden changes in the power supply in the event of a generator fault within the grid, a stable and quick response of the supplied active power and reactive power is required. Ru. In this regard, fuel cells and the like are expected to meet the above requirements because their power generation method does not involve thermal energy, and their output response characteristics are quick. However, the conventional inverter control method has
As mentioned above, since the response speed is slow, there is a problem in that the advantage of quick response of a DC power source such as a fuel cell cannot be effectively utilized. [Object of the Invention] The present invention eliminates mutual interference between active power control and reactive power control, which was unavoidable in conventional inverter control, and provides a stable and quick-responsive inverter control device that can independently execute each control. The purpose is to provide [Summary of the Invention] Therefore, the present invention is characterized in that mutual interference is eliminated by applying a correction command from at least one of the active power control system and the reactive power control system to the other control system. shall be. [Embodiment of the Invention] FIG. 1 shows a configuration diagram of an inverter control device according to an embodiment of the present invention, where 1 is a fuel cell. The DC output of the fuel cell 1 is converted into AC by an inverter 2, and is supplied to the power system 4 via a power transmission line 3. Let V _I be the output voltage of the inverter 2 at this time, P be the active power, and Q be the reactive power.
Further, the interconnection impedance of the power transmission line 3 is assumed to be Z, and the voltage of the power system 4 is assumed to be _VL . 5 is an active power detector, 6 is a reactive power detector, 7 is a phase detector, and 8 is a voltage detector. The output S _P of each of these detectors,
S _Q , S〓, and S _V are comparators 9, 10, 11, and 1, respectively.
Added to 2. 13 is an active power setting device, and 14 is a reactive power setting device. The outputs S ₁₃ and S ₁₄ from these setting devices are compared with S _P and S _Q , respectively, and the deviations are added to the active power control calculator 15 and the reactive power control calculator 16, respectively.
Differential) is calculated. As a result, the output of the active power control calculator 15 is sent to the comparator 11 as the phase command signal X.
and is added to the voltage correction coefficient section 17. Also,
The output of the reactive power control calculator 16 is the voltage command signal Y
The signal is added to the comparator 12 and the phase correction coefficient section 18 as a signal. Each signal X, Y is each coefficient part 1
In steps 7 and 18, the signals are multiplied by the gains G _V and G and applied to the comparators 12 and 11 as correction signals. The phase deviation signal from the comparator 11 is applied to a phase control calculation circuit 19 and converted into a phase control signal. Further, the voltage deviation signal from the comparator 12 is sent to the voltage control calculation circuit 20.
is added to the voltage control signal and converted into a voltage control signal. Each of these control signals is applied to the inverter 2 via the waveform control circuit 21, and the phase and magnitude of the voltage V _I output from the inverter 2 are adjusted so that the outputs of the comparators 11 and 12 are both 0. is adjusted, thereby controlling the active power P and the reactive power Q according to the set values. With the above configuration, the gain of the voltage correction coefficient section 17 is
G _V and the gain G of the phase correction coefficient unit 18 are for eliminating interference between active power control and reactive power control, and for the sake of explanation, V _I = V _IR , V _L = V _LR ,
Considering the state of operation with θ = θ _R , at this time
Let G _V and G〓 be the following values. G _V = V _IR・V _LR sinθ _R /2V _IR −V _LR cosθ _R …(3) G=1/V _IR・sinθ _R /cosθ _R =tanθ _R /V _IR …(4) Also, active power control Let us consider a case where the output X of the computing unit 15 and the output Y of the reactive power control computing unit 16 are computed based on their respective deviation input signals, and each changes by ΔX and ΔY. At this time, the inverter control device outputs the composite value of the command signals for controlling the phase applied to the comparators 11 and 12, and the command signal for controlling the voltage, respectively (ΔX−ΔY・G〓) and (ΔY −
Accordingly, the phase difference θ _R and the inverter voltage V _IR are also changed by Δθ and ΔV _{I ,} respectively. Therefore, Δθ and ΔV _I at this time are as shown in the following equation.

[Table] On the other hand, the change ΔP in active power and the change ΔQ in reactive power when phase difference θ and inverter voltage V _I change by Δθ and ΔV _I , respectively, can be expressed as follows. ΔP＝∂P／∂θ・Δθ＋∂P／∂V _I・ΔV _I …(6) ΔQ＝∂Q／∂θ・Δθ＋∂Q／∂V _I・ΔV _I …(7) Above (6), ( Substituting equations (1) and (2) above into equation 7), ΔP=∂(V _I・V _L・sinθ/Z)/∂θ・Δθ
+∂(V _I・V _L・sinθ/Z)/∂V _I・ΔV _I …(8) ΔQ=∂(V _I (V _I −V _L・cosθ)/Z)/∂θ
・Δθ+∂(V _I (V _I −V _L・cosθ)/Z)/∂V _I・ΔV _I
…(9) Performing each partial differentiation and rearranging, we get

[Table] 〓 〓 〓 Z Z
〓 〓 〓
becomes. Therefore, ΔP and ΔQ when changed by Δθ and ΔV _I from the state of V _I =V _IR , V _L =V _LR , and θ=θ _R can be expressed as follows, respectively.

【table】

〔Effect of the invention〕

As described above, according to the present invention, the conventional inverter control method that controls the phase of active power and the voltage of reactive power is improved, and by adding relatively simple mutual correction signals, active power control and Since interference with reactive power control is eliminated, stable and fast-responsive inverter power control that meets the system requirements is possible, and the benefits of not only fuel cells but also DC power supplies with fast response power supply can be realized. It can be used more effectively and has a significant effect on improving the supply capacity and stability of the AC power system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an inverter control device showing one embodiment of the invention, and FIGS. 2 and 3 are block diagrams of inverter control devices showing other embodiments of the invention. 1... Fuel cell, 2... Inverter, 3... Power transmission line, 4... Power system, 5... Active power detector, 6... Reactive power detector, 7... Phase detector,
8... Voltage detector, 9-12... Comparator, 13...
...Active power setting device, 14...Reactive power setting device, 1
5... Active power control computing unit, 16... Reactive power control computing unit, 17... Voltage correction coefficient section, 18... Phase correction coefficient section, 19... Phase control computing circuit, 20
... Voltage control calculation circuit, 21 ... Waveform control circuit.

Claims (1)

[Scope of Claims] 1. In a control device for a self-excited power converter that converts the output of a DC power source into alternating current, active power control that generates a phase command signal for the output voltage of the self-excited power converter based on a control deviation of the active power. a voltage correction coefficient section for generating a voltage correction signal for the output of the self-excited power converter based on the phase command signal; and a voltage correction coefficient section for generating a voltage correction signal for the output of the self-excited power converter based on the control deviation of reactive power a reactive power control unit that emits;
a phase correction coefficient section that generates a phase correction signal for the output voltage of the self-excited power converter based on the voltage command signal; a phase detection section that detects the phase of the output voltage of the self-excited power converter; a phase control section that performs phase control based on the sum of an output signal of the detection section, a phase command signal, and a phase correction signal; a voltage detection section that detects the output voltage of the self-excited power converter; and an output signal of the voltage detection section. a voltage control unit that performs voltage control based on the sum of a voltage command signal and a voltage correction signal; and a waveform control that inputs output signals of the phase control unit and the voltage control unit to control the phase and voltage of the output of the self-excited power converter. A control device for a self-excited power converter, comprising: 2. In a control device for a self-excited power converter that converts the output of a DC power source into alternating current, an active power control unit that issues a phase command signal for the output voltage of the self-excited power converter based on a control deviation of the active power, and a a reactive power control unit that generates a voltage command signal for the output of the self-excited power converter based on a control deviation; and a phase correction coefficient unit that generates a phase correction signal for the output voltage of the self-excited power converter based on the voltage command signal. a phase detection section that detects the phase of the output voltage of the self-excited power converter; a phase control section that performs phase control based on the sum of an output signal of the phase detection section, a phase command signal, and a phase correction signal; A voltage detection section that detects the output voltage of the excited power converter, a voltage control section that performs voltage control based on the output signal of the voltage detection section and the voltage command signal, and output signals of the phase control section and the voltage control section are input. A control device for a self-excited power converter, comprising: a waveform controller that controls the phase and voltage of the output of the self-excited voltage converter. 3. A control device for a self-excited power converter that converts the output of a DC power source into alternating current, comprising: an active power control section that issues a phase command signal for the output voltage of the self-excited power converter based on a control deviation of active power; a voltage correction coefficient section that issues a correction signal for the output voltage of the self-excited power converter based on the signal; and a reactive power control section that issues a voltage command signal for the output of the self-excited power converter based on a control deviation of the reactive power. ,
a voltage detection section that detects the output voltage of the self-excited power converter; a voltage control section that performs voltage control based on the sum of an output signal of the voltage detecting section, a voltage command signal, and a voltage correction signal; a phase detection section that detects the phase of the output voltage of the output voltage; a phase control section that performs phase control using the output signal of the phase detection section and a phase command signal; and a phase control section that receives the output signals of the phase control section and the voltage control section; 1. A control device for a self-excited power converter, comprising a waveform control section that controls the phase and voltage of the output of the excited power converter.